Lighting optical system

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical lighting system which can be used as an original irradiator in a proximity exposure device for printing: circuit patterns of a printed-wiring board; an integrated circuit, and the like, onto a substrate. The present invention is also useful in a contact printer and a process camera for printing the image of an original process film onto a machine plate, and the like. More particularly, the present invention relates to an optical lighting system which can uniformly irradiate the total area of a surface to be irradiated in a proximity exposure device and a contact printer (hereinafter these are simply referred to as a contact or proximity exposure system), or can perform irradiation such that the irradiance of an image surface is uniform in a process camera and the like (hereinafter simply referred to as a projection system).
2. Description of the Prior Art
FIG. 1 illustrates a conventional optical
or proximately exposure lighting system system according to "OPTICAL ENGINEERING HANDBOOK" published by ASAKURA SHOTEN in February, 1986, p. 682. FIG. 2 illustrates a conventional optical lighting system of a projection system.
Referring to FIG. 1, the conventional optical lighting system of a contact or proximity exposure system basically comprises a light source LS; a so-called fly's eye lens OS located in the vicinity of the second focal point of an elliptical mirror EM (for conveging light emitted from the light source LS); and a collimator lens CL located between the fly's eye lens OS and a surface P to be irradiated. The fly's eye lens OS is which is a lens which is formed by arranging a plurality of element lenses on a plane perpendicular to the optical axis of the element lenses. Reflection mirrors M.sub.2 and M.sub.3 act to change the advancing direction of the light. The real image of an exit pupil of the elliptical mirror EM is formed in the vicinity of the front focal point of the collimator lens CL through the fly's eye lens OS. The real image of an exit pupil of the fly's eye lens OS is formed on the surface P to be irradiated through the collimator lens CL. According to this optical lighting system, even if a small gap between an original pattern OG, placed on the surface P to be irradiated, and a photosensitive material PM occurs, gradation or misregistration of a printed pattern image can be prevented, since printing is performed by parallel light. Furthermore, irradiance is increased as high as possible by forming the real image of the exit pupil of the fly's eye lens OS, which is secondary light source, on the surface P to be irradiated. Still further, irradiance distribution is unified by correcting the nonuniform quantity of light caused at the second focal point of the elliptical mirror EM, through the fly's eye lens OS. The collimator lens CL having a long focal length is used since it is necessary to unify irradiance distribution on the surface P to be irradiated.
Referring to FIG. 2, the conventional optical lighting system of a projection system comprises: a number of light source lamps 11 arranged in a light source box 10; a light diffusion plate 12 located in front of the light source box 10: and a gradient filter GF located between the light diffusion plate 12 and an original OG. The gradient filter GF is constructed such that the transmittance of light therethrough becomes lower as it approaches the center. The original OG is irradiated through the gradient filter GF so that irradiance in the peripheral portion of the original's surface (i.e., a surface P to be irradiated) becomes higher, whereby irradiance on an image surface P' is unified. Namely, lowering of irradiance in the peripheral portion of the image surface P', which is caused by a projection lens IL in accordance with the "cos.sup.4 .theta. law", is corrected by the gradient filter GF.
In the conventional optical lighting system as hereinbefore described, an area of uniform irradiance on the surface P decreases when the optical path length is reduced to decrease the overall size of the device. Therefore, it is necessary to lengthen the optical path length in order to enlarge the area of uniform illuminance. Concommitantly, the overall size of the device is increased.
On the other hand, in the conventional projection optical lighting system as hereinbefore described, the quantity of light utilized is inefficient since the gradient filter GF is interposed in the optical path and is needed to unify the irradiance of the image surface.
SUMMARY OF THE INVENTION
According to a first aspect of the invention, an optical lighting system is provided which comprises an optical lens system including a lens which has an incident light plane, an exiting light plane and an optical axis, the system being placed between a light source and a surface to be irradiated. Irradiance at a irradiation height H on the surface to be irradiated is defined as S(H), and a relationship between an angle .theta., which a ray proceeding from the light source to the incident light plane of the lens optical system makes with the optical axis, and the irradiation height H is defined as the following equation (1):
.intg.S(H)HdH=.intg.J(.theta.)sin .theta.d.theta. (1)
Thus, an angle .alpha..sub.1, which the plane of incidence at a given incident height of the lens optical system makes with the optical axis is defined by the following equation (2):
tan .alpha..sub.1 =(-n cos.theta..sub.1 +cos .theta.)/(nsin .theta..sub.1 -sin.theta.) (2)
and an angle .alpha..sub.2, which the exiting light plane at a given exiting height of the optical lens system makes with the optical axis, is defined by the following equation (3):
tan .alpha..sub.2 =(-n cos.theta..sub.1 +cos.theta.)/(n sin.theta..sub.1 -sin.phi.) (3)
where, n is the refractive index of the lens optical system, J(.theta.) is the radiant intensity of the light source in the direction of an angle .theta. with respect to the optical axis, .theta..sub.1 is an angle which a ray proceeding through the optical lens system to the exiting light plane makes with the optical axis, and .phi. is an angle which a ray proceeding from the optical lens system at a given exiting height on the exiting light place of the optical lens system makes with the optical axis.
According to another aspect of the invention, an optical lighting system is provided which comprises an optical mirror system, having a reflecting surface and a optical axis, which is placed in the rear of a light source to irradiate a surface which is located in front of the light source. Irradiance at an irradiation height H on the surface to be irradiated is defined as S(H), and the relationship between angle .theta., which a ray proceeding from the light source to the reflecting surface of the optical mirror system makes with the optical axis, and the irradiation height H is defined as the following equation (4):
.intg.S(H)HdH=.intg.J(.theta..sub.1)sin .theta..sub.1 d.theta..sub.1 +.intg.J(.theta.)K(.beta.)sin .theta.d.theta. (4)
Thus, an angle .alpha..sub.3, which the reflecting surface at a given incident height of the optical mirror system makes with the optical axis, is defined by the following equation (5):
tan .alpha..sub.3 =l/tan {(.theta.-.phi.)/2} (5)
where .theta. is an angle which a ray proceeding from the light source to the mirror optical system makes with the optical axis, .theta..sub.1 is an angle which a ray proceeding from the light source directly to the irradiation height H makes with the optical axis, J(.theta..sub.1) and J(.theta.) are the radiant intensity of the light source in the directions of angles of .theta..sub.1 and .theta., respectively, with respect to the optical axis, K(.beta.) is a reflection factor of the mirror optical system wherein the incident angle is (.beta.), and .phi. is an angle which a.ray proceeding from the given incident height of the mirror optical system to the irradiation height H makes with the optical axis.
According to the present invention, the optical path length from a light source to a surface to be irradiated can be greatly decreased without reduction of irradiance in the peripheral portion of the surface to be irradiated in a contact or proximity exposure system. As a result, the overall size of the irradiator can be decreased. Furthermore, irradiance on an image surface can be unified without interposing a gradient filter, and the like, in the optical path in a projection system. As a result, the light is efficiently utilized.
Accordingly, it is an object of the present invention to provide an optical lighting system which can unify irradiance on a surface to be irradiated and decrease the optical path length thereby decreasing the overall device size, in a contact or proximity exposure system, and can unify irradiance on an image surface while efficiently utilizing light quantity without using a gradient filter and the like, in a projection system.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 and FIG. 2 illustrate prior art lighting systems.
FIG. 3 is a view showing a lens optical system according to an embodiment of an optical lighting system in accordance with the present invention.
FIG. 4 and FIG. 5 are enlarged views showing the portions IV and V of FIG. 3, respectively.
FIG. 6 is a perspective view schematically showing an optical lighting system using the lens optical system shown in FIG. 3.
FIG. 7 is a view showing a Fresnel lens according to another embodiment of the optical lighting system in accordance with the present invention.
FIG. 8 and FIG. 9 are enlarged views showing the portions VIII and IX of FIG. 7, respectively.
FIG. 10 is a view showing a optical mirror system according to still another embodiment of the optical lighting system in accordance with the present invention.
FIG. 11 is an enlarged view showing the portions XI of FIG. 10.
FIG. 12 is a view showing a Fresnel mirror according to still another embodiment of the optical lighting system in accordance with the present invention.
FIG. 13 to FIG. 39 are ray tracing views showing Examples 1-27 of the optical lighting system in accordance with the present invention, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An optical lighting system according to the present invention includes a optical lens system or an optical mirror system. In the following description, the principle of the present invention when utilizing an optical lens system will be described in reference FIG. 3 to FIG. 9. The principle of the present invention when utilizing an optical mirror system will be described in reference to FIG. 10 to FIG. 12. The light source used in the optical lighting system according to these embodiments is sufficiently small in comparison with the aperture diameter and focal length of the optical lighting system, and the radiant intensity of J(.theta.) of the light source is symmetrical with respeot to the optical axis of the optical lighting system.
FIG. 3 is a view showing an optical lens system according to an embodiment of an optical lighting system in accordance with the present invention. Referring to FIG. 3, an optical lens system L is placed between a light source LS and a surface P to be irradiated. Assuming a virtual sphere having a radius of r is located around the light source LS, as shown in FIG. 6, the area .delta. S.sub.1 of a circular band W.sub.1 on the virtual sphere, inner and outer circles of which are defined by radial lines extending from the center O of the virtual sphere in angles .theta. and .theta.+.delta..theta. with respect to an optical axis Z, respectively, is given by the following equation:
.delta.S.sub.1 =2.pi.r.sup.2 sin .theta..delta..theta. (6)
A solid angle .delta..OMEGA..sub.1 for viewing the circular band W.sub.1 from the center O of the virtual sphere is
.delta..OMEGA..sub.1 =2.pi.sin .theta..delta..theta. (7)
and hence radiant flux F passing through the circular band W.sub.1 is given by the following equation as the product of the solid angle .delta..OMEGA..sub.1 and the radiant intensity J(.theta.):
F=J(.theta.).multidot.2.pi.sin .theta..delta..theta. (8)
Assuming that the radiant flux F irradiates a circular band W.sub.2 on a surface P to be irradiated, and which has an outer radius H and .delta. H in width, through an optical lens system L, the area .delta. S.sub.2 of the circular band W.sub.2 is
.delta.S.sub.2 2.pi.H.delta.H (9)
and hence if the transmission factor of the optical lens system L is 100%, the illuminance S(H) of the circular band W.sub.2 on the surface P to be irradiated is given by the following equation:
S(H)=J(.theta.)sin .theta.67 .theta./H.delta.H (10)
The aforementioned equation (1) is obtained from the equation (10).
.intg.S(H)HdH=.intg.J(.theta.)sin .theta.d.theta. (1)
This equation (1) defines a relationship between an angle .theta., which a ray proceeding from the light source LS to the incident height R.sub.1 of the optical lens system L makes with the optical axis Z and a irradiation height H.
In other words, equation (1) defines the exiting angle .theta. of a ray emitted from the light source LS, when irradiance S(H) on the surface P to be irradiated is set by a given function which satisfies
ti S(H).gtoreq.S(O) (11)
, for example, to unify irradiance all over the surface P to be irradiated in a contact or proximity exposure system, or to increase irradiance at the peripheral portion of the surface P to be irradiated to unify the irradiance of an image surface in a projection system.
It will be now described that a ray emitted from the light source LS in an outgoing angle .varies. can be led to a given irradiation height H by defining angles .alpha..sub.1 and .alpha..sub.2 which the light incident and exiting planes F.sub.1 and F.sub.2 of the optical lens system L make with the optical axis, respectively, by the aforementioned equations (2) and (3).
Referring to FIG. 3, a ray emitted from the light source LS at outgoing angle reaches the point Q of an incident height R.sub.1 on the light incident plane F.sub.1 of the optical lens system L. FIG. 4 is an enlarged view showing the portion IV of FIG. 3. When the Snell's law is applied at the point Q in FIG. 4, the following equation results:
sin (.theta.+.beta.)=n sin (.beta.+.theta..sub.1) (12)
.beta.=90.degree.-.alpha..sub.1 (13)
where .alpha..sub.1 is an angle which the light incident plane F.sub.1 at the point Q makes with the optical axis Z, .beta. is an angle which a normal line N.sub.1 dropped to the point Q makes with the optical axis Z, and .theta..sub.1 is an angle which a ray refracted at the light incident plane F.sub.1 makes with the optical axis Z.
The following equation is obtained by substituting equation (13) in the equation (12) and simplifying same:
cos .theta.cos .alpha..sub.1 +sin .theta.sin .alpha., =n(cos .theta..sub.1 cos .alpha..sub.1 +sin .theta..sub.1 sin .alpha..sub.1) (14)
The aforementioned equation (2) is obtained by dividing the both sides of the equation 14) by cos .alpha..sub.1 and simplifying the same:
tan .alpha..sub.1 =(-ncos .theta..sub.1 'cos .theta.)/(n sin .theta..sub.1 -sin .theta.) (2)
pAt the other side of lens L a ray refracted at the light exiting plane F.sub.2 of the optical lens system L emerges from point T at outgoing height R.sub.2 of the light exiting plane F.sub.2 FIG. 5 is an enlarged view showing the portion V of FIG. 3. When Snell's law is applied at the point T in FIG. 5, the following equation results:
n sin (.gamma.-.theta..sub.1)=sin (.gamma.-.phi.) (15)
.gamma.=.alpha..sub.2 -90.degree. (16)
where .alpha..sub.2 is an angle which the light exiting plane F.sub.2 of outgoing at the point T makes with the optical axis Z, .gamma. is an angle which a normal line N.sub.2 dropped to the point T makes with the optical axis Z, and .phi. is an angle which an exiting ray from the point T makes with the optical axis Z.
The aforementioned equation (3) is obtained by substituting the equation (16) in the equation (15):
tan .alpha..sub.2 =(-ncos .theta..sub.1 +cos .theta.)/(n sin .theta..sub.1 -sin .phi.) (3)
According to the present invention, a ray emitted from the light source LS at an exiting angle reaches the irradiation height H and irradiates surface P in the desired irradiance S(H) satisfying the aforementioned equation (16), by defining the plane F.sub.1 of incidence of the optical lens system L by the equation (2 and the light exiting plane F.sub.2 by the equation (3 , as is evident from the above description.
The embodiment where the optical lens system is constructed with a Fresnel lens will now be described. FIG. 7 is a view showing a Fresnel lens according to this second embodiment of the optical lighting system in accordance with the present invention. As shown in FIG. 7, a ray emitted from a light source LS at outgoing angle .theta. reaches the point Q of a incident height R.sub.1 on the flat light incident plane F.sub.1 of the Fresnel Lens FL. FIG. 8 is an enlarged view showing the portion VIII of FIG. 7. When Snell's law is applied at point Q in FIG. 8, the following equation results:
sin .theta.-n sin .theta..sub.1 (17)
The equation (17) is rewritten into the following equation: ##EQU1##
At the other side of Fresnel lens FL, a ray refracted at the light incident plane F.sub.1 of the Fresnel lens FL emerges at the outgoing height R.sub.2 of a Fresnel optical surface F.sub.s, in FIG. 7. FIG. 9 is an enlarged view showing the portion IX of FIG. 7. When Snell's law is applied at the point T in FIG. 9, the aforementioned equation (3) is obtained:
tan .alpha..sub.2 =(-n cos .theta..sub.1 +cos .phi.)/(n sin .theta..sub.1 -sin .phi.) (3)
The following equation is obtained by substituting the above equation (17) and (18) in the equation (3): ##EQU2##
When the Fresnel lens is utilized, desired irradiance distribution similar to the optical lens system L as hereinbefore described can be obtained by forcing the Fresnel optical surface F.sub.s in accordance with the equation (19).
The use of a Fresnel optical system FL to obtain uniform irradiance distribution on the surface P to be irradiated will now be described in more detail. Assuming that the irradiance S(H) on the surface P to be irradiated, which appears in the aforementioned equation (1), is defined as S(H)=S(0) K (k: constant), the following equation is obtained:
.intg.KHdH=.intg.J(.theta.) sin .theta.d.theta. (20)
When the radiant intensity of the light source LS is defined as J(Q)=1 (in the case of an ideal point light source), the following equations are obtained from equation (20):
(k/2)H.sup.2 =1-cos .theta.=2sin.sup.2 (.theta./2) (21) ##EQU3## This equation (22) defines a relationship between an angle .theta., which is the angle a ray proceeding from the light source LS to the light incident plane F.sub.1 of the Fresnel lens FL makes with an optical axis Z, and an irradiation height H. In a paraxial region, the irradiation height H defined by the above equation (22) is given by the following equation:
H=.theta.(A+B=AB/f) (23)
where A is a distance from the light source LS to the light incident plane F.sub.1 of the Fresnel lens FL, B is a distance from the light exiting plane F.sub.2 to the surface P to be irradiated on the optical axis Z of the Fresnel lens FL, and f is the focal length on the optical axis Z of the Fresnel lens FL.
The constant k is given by the following equation by using the equations (22 and (23):
K=1/(A+B-AB/f).sup.2 (24)
The following equation is obtained by substituting equation (24) in the equation (22):
H=2(A+B-AB/f)sin (.theta./2) (25)
This equation (25) defines a relationship between the exiting angle .theta. from the light source LS and the irradiation height H, in the case where the distances A and B between the light source LS, the Fresnel lens FL and the surface P to be irradiated are appropriately defined and the surface P to be irradiated is irradiated in uniform irradiance by using a point light source.
That is, the configuration of the Fresnel lens FL is determined through the steps where first the height R.sub.1 on the light incident plane F.sub.1 is defined with respect to the exiting angle .theta. from the light source LS, secondly the outgoing height R.sub.2 is defined on the assumption that the thickness D of the Fresnel lens FL is negligible, and thirdly the inclination angle .alpha..sub.2 of the Fresnel optical surface F.sub.s at the exiting height R.sub.2 is defined by the aforementioned equation (19).
FIG. 10 is a view showing an optical mirror system according to a third embodiment of the optical lighting system in accordance with the present invention. In the case of an optical mirror system, the following equation can be applied in place of the equation (10) in the optical lens system as hereinbefore described:
S(H)={J(.theta..sub.1) sin .theta..sub.1 .delta..theta..sub.1 }/(H.delta.H) +{J(.theta.)K(.beta.)sin .theta..delta..theta.}/(H.delta.H)(26)
In this equation (26), the first term of the right side corresponds to irradiance by direct light from a light source LS, and the second term of the right side corresponds to irradiance by reflection light which is generated by reflecting light emitted from the light source LS by an optical mirror system M. The first term is substantially negligible if the light source LS is a surface light source or the like which emits light only toward the optical mirror system M.
The aforementioned equation (4) is obtained from the above equation (26).
S(H)H.delta.H=.intg.J(.theta..sub.1)sin .theta..sub.1 .delta..theta..sub.1 +J(.theta.)K(.beta.)sin .theta..delta..theta. (4)
This equation (4) defines a relationship between an angle .theta., which is the angle a ray proceeding from the light source LS to the incident height R.sub.3 of the mirror optical system M makes with an optical axis Z, and an irradiation height H.
That is, this equation shows that the opt-ical mirror system M can be formed to obtained desired illuminance S(H) on a surface P to be irradiated as is similar to the case of the optical lens system L.
It will now be described that an angle .alpha..sub.3, which a reflection surface F.sub.3 at the incident height R.sub.3 of the optical mirror system M makes with the optical axis Z is defined by the aforementioned equation (5).
It is assumed that a ray emitted from the light source LS is an exiting angle .theta. irradiates the point T of the incident height R.sub.3 on the reflection surface F.sub.3 of the optical mirror system M. FIG. 11 is an enlarged view showing the portion XI of FIG. 10.
When the law of reflection is applied to the point T in FIG. 11, the following equation results:
.beta.=.gamma.+.phi. (27)
where .beta. is an angle which an incident ray makes with a normal line N.sub.3 dropped on the point T, .gamma. is an angle which the normal line N.sub.3 makes with the optical axis Z, and .phi. is an angle which a reflected ray makes with the optical axis Z. The following equation defines the relationship between the angles .beta. and .gamma.:
.beta.+.gamma.=.theta. (28)
and the following equation defines the relationship between the angles and .gamma. and .alpha..sub.3 :
.alpha..sub.3 =90.degree.-.gamma. (29)
The following equation is obtained from the equations (27), (28) and (29):
.alpha..sub.3 -90.degree.+(.phi.-.theta.)/2 (30)
The aforementioned equation (5) is obtained by taking the tangent of the both sides of the equation (30):
tan .alpha..sub.3 =l/tan {(.theta.-.phi.)/2} (5)
That is, the mirror optical system M can be implemented so as to provide desired irradiance S(H), similar to the case of the lens optical system L, by forming the reflection surface F.sub.3 of the mirror optical system M in accordance with the equation (5).
Further, it is evident that the same irradiance distribution as the mirror optical system M hereinbefore described can be obtained by using a Fresnel mirror FM, by forming a Fresnel optical surface F.sub.s in accordance with the aforementioned equation (5), as shown in FIG. 12.
Examples 1 to 27 which illustrate the present invention will now be discussed in accordance with the following classification wherein the examples are broadly classified into a lens optical system and a mirror optical system. These examples further illustrate the preferred embodiments within the scope of the present invention.
Lens Optical Svstem
(1) lens octical svstem includinc an aspheric surface lens . . . L
(i) for contact or proximity exposure ... L1
(ii) for projection . . . L2
(2) lens optical system includinc a Fresnel lens . . . LF
(i) for contact or proximity exposure . . . FL1
(ii) for projection . . . FL2
Mirror Optical Svstem
(1) mirror optical system including an aspheric surface mirror . . . M
(i) for contact or proximity exposure . . . M1
(ii) for projection . . . M.sub.2
(2) mirror octical svstem including a Fresnel mirror . . . FM
(i) for contact or proximity exposure . . . FM1
(ii) for projection . . . FM.sub.2
Examples 1-27 will be illustrated by using the parameters as hereinafter described, lens or mirror data on the basis of parameter values and ray tracing views according to respective lens or mirror optical systems.
The various parameters are represented by the following symbols:
(A) In the case of a lens optical svstem (see FIG. 3 to FIG. 5)
A: distance between a light source LS and a plane F.sub.1 of incidence
B: distance between an outgoing plane F.sub.2 and a surface P to be irradiated
D: thickness of a lens L
f: focal length of the lens optical system in a paraxial region
n: refractive index of the lens L
H irradiation height on the surface P to be irradiated
.theta.: angle which an outgoing ray from the light source LS makes with an optical axis Z
.phi.: angle which an outgoing ray from the outgoing plane F.sub.2 of the lens L makes with the optical axis Z
.alpha..sub.2 : angle which the outgoing plane F.sub.2 at an outgoing height R.sub.2 makes with the optical axis Z
D.sub.2 : sag at the outgoing height R.sub.2, which is a distance between the foot of a perpendicular dropped to the optical axis Z from the outgoing plane F.sub.2 at the outgoing heiqht R.sub.2 and the top of the outgoing plane F.sub.2
E: efficiency factor for all radiant flux from the light source LS
In these examples, the plane of incidence is formed using a spherical or flat surface, and hence values as to symbols .alpha..sub.1, R.sub.1 and D.sub.1 in FIG. 3 are not shown.
(B) In the case of a mirror optical system (see FIG. 10 to FIG. 12)
A: distance between a light source LS and a reflecting surface F.sub.3
B: distance between the reflecting F.sub.2 and a surface P to be irradiated
H: irradiation height on the surface P to be irradiated
.theta.: angle which an outgoing ray from the light source LS makes with an optical axis Z
.phi.: angle which a reflected ray from the reflecting surface F.sub.3 makes with the optical axis Z
.alpha..sub.3 : angle which the reflecting surface F.sub.3 makes with the optical axis Z
R.sub.3 : reflective height of the reflected ray on the reflecting surface F.sub.3
D3: sag at the outgoing height R.sub.3, which is a distance between the foot of a perpendicular dropped to the optical axis Z from the plane F.sub.3 at the reflective height R.sub.3 and the top of the reflecting surface F.sub.3
E: efficiency factor for all radiant flux from the light source LS
The reflection factor of each mirror optical system is adapted to satisfy K(.beta.) 0.9.
Further it is assumed that radiant intensity distribution is uniform and hence J(.theta.) 1 when the light source LS is a point light source, and J(.theta.)=cos .theta. is applied when the light source LS is a surface illuminant. In the following description, it is assumed that the size of the surface illuminated is negligible.
EXAMPLE 1
In this example a lighting optical system comprising lens optical system L was used in a close contact or proximity exposure system in which irradiance on a surface P was uniform all over the surface P. The operating parameters and lens data are shown in Table 1 and a ray tracing view in accordance with this lens L is shown in FIG. 13.
In this example, the incidence plane F.sub.1 of this lens L was a spherical surface when was convex toward a point light source LS and the outgoing plane F.sub.2 thereof was an aspheric surface. In FIG. 13, the symbol M.sub.O denotes a spherical mirror for forward reflecting of a ray emitted backward from the point light source LS.
TABLE 1______________________________________A = 30 mm B = 600 mm D = 80 mm f = 200 mmE = 55% n = 1.5 R.sub.1 = 400 mmH (mm) .theta. (deg) .phi. (deg) .alpha..sub.2 (deg) R.sub.2 (mm) D.sub.2 (mm)______________________________________ 25.0 3.0 1.9 92.0 4.3 0.0 50.0 6.1 3.9 94.1 8.7 0.3 75.0 9.2 5.8 96.1 13.1 0.6100.0 12.4 7.8 98.1 17.5 1.2125.0 15.5 9.7 100.2 21.9 1.9150.0 18.6 11.6 102.2 26.2 2.8175.0 21.7 13.4 104.2 30.6 3.8200.0 24.9 15.2 106.2 34.9 5.0225.0 28.1 17.0 108.2 39.2 6.3250.0 31.3 18.7 110.2 43.5 7.8275.0 34.5 20.4 112.1 47.8 9.5300.0 37.8 22.0 113.8 52.2 11.3325.0 41.1 23.6 115.5 56.5 13.3350.0 44.4 25.1 116.9 61.0 15.5375.0 47.8 26.5 118.1 65.7 17.9400.0 51.2 27.9 118.8 70.6 20.6425.0 54.6 29.2 119.0 76.0 23.6450.0 58.1 30.3 118.4 82.3 27.1475.0 62.7 31.3 116.3 90.6 31.4500.0 65.3 31.8 111.1 103.8 37.2______________________________________
EXAMPLE 2
In this example an optical lighting system comprising an optical lens system L was used in a contact or proximity exposure system in which irradiance on a surface P to be irradiated was uniform all over the surface P. The operating parameters and lens data are shown in Table 2 and a ray tracing view in accordance with this lens L is shown in FIG. 14.
In this example, the incidence plane F.sub.1 of lens L was a flat surface and the outgoing plane F.sub.2 thereof was an aspheric surface. A light source LS is formed by a surface light source which emits light only toward the lens L.
TABLE 2______________________________________A = 30 mm B = 500 mm D = 100 mm f = 600 mmE = 94% n = 1.5H (mm) .theta. (deg) .phi. (deg) .alpha..sub.2 (deg) R.sub.2 (mm) D.sub.2 (mm)______________________________________ 25.0 2.7 2.3 90.9 4.6 0.0 50.0 5.5 4.6 91.8 9.3 0.1 75.0 8.3 6.9 92.8 14.1 0.3100.0 11.1 9.2 93.9 18.8 0.6125.0 14.0 11.4 95.0 23.6 0.9150.0 16.8 13.6 96.3 28.5 1.4175.0 19.8 15.7 97.8 33.5 2.0200.0 22.8 17.7 99.4 38.5 2.8225.0 25.8 19.7 101.2 43.7 3.7250.0 28.9 21.7 103.2 49.0 4.9275.0 32.1 23.5 105.4 54.4 6.2300.0 35.5 25.2 107.9 60.1 7.9325.0 39.0 26.9 110.6 65.9 10.0350.0 42.6 28.4 113.7 72.0 12.4375.0 46.6 29.9 117.1 78.4 15.5400.0 50.8 31.2 120.9 85.4 19.4425.0 55.4 32.3 125.2 93.1 24.4450.0 60.6 33.1 130.2 102.3 31.5475.0 66.9 33.5 136.3 114.6 43.2500.0 75.6 32.1 145.6 139.2 73.9______________________________________
EXAMPLE 3
In this example an optical lighting system comprising an optical lens system L was used in a contact or proximity exposure system in which irradiance on a surface P to be irradiated was uniform all over the surface P. The operating parameters and lens data are shown in Table 3 and a ray tracing view in accordance with this lens L is shown in FIG. 15.
In this example, the incidence plane F.sub.1 of this lens L was a spherical surface which was concave toward a light source LS and the outgoing plane F.sub.2 thereof was an aspheric surface. The light source LS was formed by a surface light source which emits light only toward the lens L.
TABLE 3______________________________________A = 40 mm B = 500 mm D = 100 mm f = 900 mmE = 94% n = 1.5 R.sub.1 = -400 mmH (mm) .theta. (deg) .phi. (deg) .alpha..sub.2 (deg) R.sub.2 (mm) D.sub.2 (mm)______________________________________ 25.0 2.7 2.2 91.3 5.3 0.0 50.0 5.5 4.4 92.7 10.6 0.2 75.0 8.3 6.7 94.1 16.0 0.5100.0 11.1 8.9 95.7 21.5 1.0125.0 14.0 11.0 97.3 26.9 1.6150.0 16.9 13.1 99.1 32.5 2.4175.0 19.8 15.2 101.0 38.1 3.4200.0 22.8 17.1 103.2 43.8 4.6225.0 25.8 19.0 105.6 49.7 6.1250.0 29.0 20.9 108.3 55.6 8.0275.0 32.2 22.6 111.3 61.7 10.1300.0 35.6 24.3 114.7 68.0 12.8325.0 39.1 25.8 118.5 74.4 16.0350.0 42.8 27.3 122.8 81.0 19.9375.0 46.7 28.6 127.7 87.9 24.8400.0 50.9 29.8 133.3 95.0 30.9425.0 55.5 30.8 139.8 102.5 38.7450.0 60.8 31.7 147.5 110.4 49.5475.0 67.2 32.1 157.3 118.8 65.6500.0 76.0 32.0 171.0 127.2 95.7______________________________________
EXAMPLE 4
In this example an optical liqhting system comprising an optical lens system L was used in a projection system in which irradiance on a surface P to be irradiated was higher in the peripheral portion of the surface P. The operating parameters and lens data are shown in Table 4 and a ray tracing view in accordance with lens L is shown in FIG. 16.
In this example, the incidence plane F.sub.1 of this lens L was a flat surface and the outgoing plane 7 F.sub.2 thereof was an aspheric surface. A spherical mirror M.sub.O was placed in the rear of a point light surface LS.
In this example, it is assumed that the effective half field angle of an image-formation lens (not shown) is 26.6.degree., and relative irradiance on the surface P to be irradiated is set as shown in Table 4 to unify the irradiance of an image surface.
TABLE 4______________________________________A = 40 mm B = 500 mm D = 80 mm f = 400 mmE = 67% n = 1.5 .alpha..sub.2 D.sub.2 relativeH (mm) .theta. (deg) .phi. (deg) (deg) R.sub.2 (mm) (mm) irradiated______________________________________ 25.0 3.0 2.2 91.6 5.6 0.0 1.00 50.0 6.0 4.4 93.3 11.2 0.3 1.00 75.0 9.1 6.6 95.0 16.9 0.7 1.01100.0 12.1 8.7 96.7 22.6 1.3 1.01125.0 15.2 10.8 98.6 28.4 2.0 1.03150.0 18.4 12.9 100.6 34.2 3.0 1.04175.0 21.6 14.9 102.7 40.1 4.2 1.06200.0 24.8 16.9 105.0 46.1 5.7 1.08225.0 28.2 18.8 107.5 52.1 7.5 1.10250.0 31.6 20.6 110.1 58.3 9.6 1.12275.0 35.1 22.3 113.0 64.5 12.1 1.15300.0 38.6 23.9 115.9 70.9 15.0 1.18325.0 42.3 25.5 119.1 77.5 18.4 1.22350.0 46.2 26.9 122.2 84.3 22.4 1.26375.0 50.2 28.2 125.9 91.4 27.2 1.30400.0 54.3 29.4 129.4 98.9 33.0 1.34425.0 58.6 30.4 133.1 107.1 40.2 1.39450.0 63.2 31.2 136.9 116.5 49.7 1.44475.0 68.0 31.6 140.9 128.1 63.0 1.50500.0 73.0 31.3 145.4 144.2 84.6 1.56______________________________________
EXAMPLE 5
In this example an optical lighting system comprising an optical lens system L was used in a projection system in which irradiance on a surface P to be irradiated was higher in the peripheral portion of the surface P. The operating parameters and lens data are shown in Table 5 and a ray tracing view in accordance with lens L is shown in FIG. 17.
In this example, the incidence plane F.sub.1 of lens L was a spherical surface which is concave toward a point light source LS and the outgoing plane F.sub.2 thereof was an aspheric surface. A spherical mirror MO is placed in the rear of a point light surface LS.
Also in this example, relative irradiance on the surface P to be irradiated is as shown in Table 5 to unify the irradiance of an image surface, as is similar to example 4.
TABLE 5______________________________________A = 30 mm B = 400 mm D = 150 mm f = 700 mmE = 85% n = 1.5 R.sub.1 = -400 mm .alpha..sub.2 D.sub.2 relativeH (mm) .theta. (deg) .phi. (deg) (deg) R.sub.2 (mm) (mm) irradiated______________________________________ 25.0 3.4 2.4 92.2 7.9 0.1 1.00 50.0 6.8 4.8 94.4 15.8 0.6 1.00 75.0 10.2 7.2 96.7 23.8 1.3 1.01100.0 13.6 9.6 99.1 31.8 2.4 1.02125.0 17.1 11.9 101.7 39.8 3.9 1.03150.0 20.7 14.1 104.5 47.9 5.8 1.04175.0 24.3 16.2 107.5 55.9 8.1 1.06200.0 28.0 18.3 110.7 64.0 10.9 1.08225.0 31.7 20.2 114.2 72.1 14.2 1.10250.0 35.6 22.0 118.0 80.2 18.2 1.12275.0 39.5 23.8 122.2 88.2 22.8 1.15300.0 43.6 25.4 126.6 96.2 28.3 1.18325.0 47.9 26.9 131.4 104.1 34.7 1.22350.0 52.3 28.3 136.5 111.8 42.1 1.26375.0 56.9 29.5 142.0 119.5 51.0 1.30400.0 61.7 30.6 147.8 126.9 61.6 1.34425.0 66.8 31.4 154.2 134.1 74.7 1.39450.0 72.1 32.1 161.3 141.0 91.4 1.44475.0 77.8 32.5 169.2 146.8 113.7 1.50500.0 83.9 32.7 178.2 150.2 144.4 1.56______________________________________
Example 6
In this example an optical lighting system comprising a lens optical system L was used in a projection system in which irradiance on a surface P to be irradiated was higher in the peripheral portion of the surface P. The operating parameters and lens data are shown in Table 6 and a ray tracing view in accordance with lens L is shown in FIG. 18.
In this example, the incidence plane F.sub.1 of lens L was a spherical surface which is convex toward a point light source LS and the outgoing plane F.sub.2 of outgoing thereof was an aspheric surface. The light source LS was a surface light source which emits light only toward the lens L.
Also in this example, relative irradiance on the surface P to be irradiated is as shown in Table 6, as is similar to example 4.
TABLE 6______________________________________A = 25 mm B = 600 mm D = 50 mm f = 500 mmE = 87% n = 1.5 R.sub.1 = 600 mm .alpha..sub.2 R.sub.2 D.sub.2 relativeH (mm) .theta. (deg) .phi. (deg) (deg) (mm) (mm) irradiated______________________________________ 25.0 2.3 2.1 90.3 2.3 0.0 1.00 50.0 4.7 4.3 90.7 4.7 0.0 1.00 75.0 7.1 6.4 91.1 7.2 0.0 1.01100.0 9.5 8.5 91.6 9.6 0.1 1.02125.0 12.0 10.6 92.2 12.1 0.2 1.03150.0 14.5 12.6 92.9 14.7 0.3 1.04175.0 17.1 14.7 93.8 17.3 0.4 1.06200.0 19.7 16.6 94.9 20.1 0.6 1.08225.0 22.4 18.5 96.1 22.9 0.9 1.10250.0 25.2 20.4 97.6 25.9 1.3 1.12275.0 28.2 22.2 99.3 29.0 1.7 1.15300.0 31.3 23.9 101.2 32.2 2.3 1.18325.0 34.5 25.6 103.5 35.7 3.1 1.22350.0 38.0 27.2 105.9 39.5 4.1 1.26375.0 41.7 28.6 108.7 43.6 5.3 1.30400.0 45.7 30.0 111.8 48.1 7.0 1.34425.0 50.2 31.3 115.1 53.3 9.3 1.39450.0 55.2 32.4 118.6 59.7 12.5 1.44475.0 61.3 33.3 121.8 68.7 17.8 1.50500.0 69.0 33.1 122.3 88.1 30.2 1.56______________________________________
EXAMPLE 7
In this example an optical lighting system comprising a Fresnel lens FL was used in a contact or proximity exposure system in which irradiance on a surface P to be irradiated was uniform all over the surface P. The operating parameters and lens data are shown in Table 7 and a ray tracing view in accordance with this Fresnel lens FL is shown in FIG. 19.
The light source LS was a point light source.
TABLE 7______________________________________A = 125 mm B = 500 mm f = 278 mm n = 1.491R.sub.2 (mm) .alpha..sub.2 (deg) .theta. (deg) .phi. (deg) H (mm)______________________________________ 10 94.2 4.6 2.5 31.9 20 98.4 9.1 5.0 63.4 40 106.5 17.7 9.5 123.4 60 114.2 25.6 13.2 177.6 80 121.3 32.6 16.2 224.8100 127.6 38.7 18.3 264.9125 134.5 45.0 19.9 306.3150 140.4 50.2 20.8 339.5200 149.7 58.0 20.6 388.0250 156.6 63.4 18.9 420.8300 162.0 67.4 16.1 440.0350 166.1 70.4 12.5 461.0400 169.0 72.7 8.4 474.1500 172.3 76.0 -0.9 492.6560 173.0 77.4 -6.8 500.5______________________________________
EXAMPLE 8
In this example an optical lighting system comprising a Fresnel lens FL was used in a contact or proximity exposure system in which irradiance on a surface P to be irradiated is uniform all over the surface P. The operating parameters and lens data are shown in Table 8 and a ray tracing view in accordance with this Fresnel lens FL is shown in FIG. 20.
In this example, parameters values A, B and f were selected so that an outgoing angle .phi. from the Fresnel lens FL had a small angle, approximately parallel light.
According to this example, a declination angle on the surface P was within 3.degree. and hence the surface P can be irradiated by light which is almost parallel light, although the optical path length becomes longer than that in example 17 hereinafter described. Therefore, a small gap between a pattern original and a photosensitive material, will not result in lowering of resolution or misregistration. The light source LS was a point light source.
TABLE 8______________________________________A = 340 mm B = 1360 mm f = 389 mm n = 1.491R.sub.2 (mm) .alpha..sub.2 (deg) .theta. (deg) .phi. (deg) H (mm)______________________________________ 25 97.5 4.2 0.5 37.5 50 104.7 8.4 1.0 74.6 75 111.7 12.4 1.5 110.8100 118.1 16.4 1.9 145.8125 124.1 20.2 2.3 179.2150 129.4 23.8 2.6 210.9175 134.2 27.2 2.8 240.8200 138.5 30.5 2.9 268.7250 145.7 36.3 2.9 318.8300 151.3 41.4 2.6 361.7400 159.2 49.6 1.2 429.2500 164.0 55.8 -0.9 478.4556 166.0 58.6 -2.4 500.1______________________________________
EXAMPLE 9
In this example an optical lighting system comprising a Fresnel lens FL was used in a contact or proximity exposure system in which irradiance on a surface P to be irradiated was uniform all over the surface P. The operating parameters and lens data are shown in Table 9 and a ray tracing view in accordance with this Fresnel lens FL is shown in FIG. 21.
This example is useful when the Fresnel lens FL must be kept away from a light source LS to prevent deleterious effects due to heat from light source LS.
According to this example, the declination angle was relatively small, for example 12.8.degree., the optical path length was small, for example 800 mm, while a 1000 mm effective area was uniformly irradiated. The light source LS was a point light source.
TABLE 9______________________________________A = 400 mm B = 400 mm f = 600 mm n = 1.491R.sub.2 (mm) .alpha..sub.2 (deg) .theta. (deg) .phi. (deg) H (mm)______________________________________ 25 94.9 3.6 1.2 33.3 50 99.7 7.1 2.3 66.3 75 104.6 10.6 3.4 98.7100 109.4 14.0 4.3 130.3150 118.9 20.6 5.8 190.3200 128.0 26.6 6.4 245.1250 136.5 32.0 6.3 294.1300 143.9 36.9 5.3 337.3350 150.3 41.2 3.6 375.2400 155.5 45.0 1.2 408.2500 162.6 51.3 -5.4 462.1591 165.8 55.9 -12.8 500.0______________________________________
EXAMPLE 10
In this example an optical lighting system comprising a Fresnel lens FL was used in a contact or proximity exposure system in which irradiance on a surface P to be irradiated was uniform all over the surface P. The operating parameters and lens data are shown in Table 10 and a ray tracing view in accordance with this Fresnel lens FL is shown in FIG. 22.
In this example, the diameter of the area which was irradiated was set at 7.78 mm, and the distance B of the gap between the Fresnel lens FL and the surface P to be irradiated was set at 100 mm. This example is useful when irradiating a relatively small area from relatively far away. The light source LS was a point light source.
TABLE 10______________________________________A = 10 mm B = 100 mm f = 9.4 mm n = 1.491R.sub.2 (mm) .alpha..sub.2 (deg) .theta. (deg) .phi. (deg) H (mm)______________________________________0.5 96.2 2.9 -0.2 0.181.0 102.2 5.7 -0.4 0.361.5 108.1 8.5 -0.6 0.542.0 113.6 11.3 -0.7 0.713.0 123.5 16.7 -1.1 1.054.0 131.8 21.8 -1.5 1.376.0 144.2 31.0 -2.3 1.938.0 152.4 38.7 -3.2 2.4010.0 158.0 45.0 -4.1 2.7712.5 162.6 51.3 -5.4 3.1315.0 165.6 56.3 -6.6 3.4117.5 167.6 60.3 -7.9 3.6320.0 169.0 63.4 -9.2 3.8021.5 169.6 65.1 -10.0 3.89______________________________________
EXAMPLE 11
In this example an optical lighting system comprising a Fresnel lens FL was used in a contact or proximity exposure system in which irradiance on a surface P to be irradiated was uniform all over the surface P. The operating parameters and lens data are shown in Table 11 and a ray tracing view in accordance with this Fresnel lens FL is shown in FIG. 23.
In this example, a spherical mirror M.sub.O was placed in the rear of a point light source LS.
TABLE 11______________________________________A = 120 mm B = 480 mm f = 350 mm E = 63% n = 1.5H (mm) .theta. (deg) .phi. (deg) .alpha..sub.2 (deg) R.sub.2 (mm)______________________________________ 25 3.2 2.1 92.3 6.8 50 6.5 4.3 94.5 13.8 75 9.8 6.4 96.8 20.9100 13.1 8.5 99.2 28.1125 16.5 10.5 101.6 35.5150 19.8 12.5 104.2 43.2175 23.1 14.4 106.8 51.3200 26.5 16.2 109.5 59.9225 29.9 17.9 112.3 69.1250 33.3 19.6 115.3 79.0275 36.8 21.0 118.4 89.8300 40.3 22.4 121.7 101.7325 43.8 23.6 125.2 115.1350 47.3 24.5 128.8 130.4375 51.0 25.2 132.8 148.2400 54.6 25.6 137.0 169.3425 58.4 25.5 141.6 195.2450 62.2 24.8 146.8 227.8475 66.1 23.0 152.8 270.9500 70.0 19.3 159.7 331.1______________________________________
EXAMPLE 12
In this example an optical lighting system comprising a Fresnel lens FL was used in a contact or proximity exposure system in which irradiance on a surface P to be irradiated was uniform all over the surface P. The operating parameters and lens data are shown in Table 12 and a ray tracing view in accordance with this Fresnel lens FL is shown in FIG. 24.
In this example, a light source LS was formed by a surface light source which emits light only toward the Fresnel lens FL.
TABLE 12______________________________________A = 130 mm B = 500 mm f = 650 mm E = 89% n = 1.5H (mm) .theta. (deg) .phi. (deg) .alpha..sub.2 (deg) R.sub.2 (mm)______________________________________ 25 2.7 2.1 91.1 6.1 50 5.4 4.3 92.2 12.3 75 8.1 6.4 93.4 18.5100 10.8 8.5 94.6 24.9125 13.6 10.5 96.0 31.5150 16.4 12.5 97.5 38.3175 19.2 14.5 99.1 45.4200 22.1 16.3 100.9 52.9225 25.1 18.1 103.0 60.9250 28.1 19.8 105.3 69.5275 31.2 21.4 107.9 78.9300 34.4 22.8 110.8 89.2325 37.8 24.1 114.1 100.9350 41.3 25.2 117.9 114.3375 45.0 26.0 122.2 130.1400 49.0 26.6 127.3 149.5425 53.3 26.6 133.4 174.4450 58.1 25.7 141.0 208.9475 63.6 23.0 150.8 262.6500 70.6 14.5 164.0 369.7______________________________________
EXAMPLE 13
In this example, the declination angle on surface P to be irradiated was reduced to 0.degree. by placing a second Fresnel lens FL.sub.2 in the rear of a first Fresnel lens FL.sub.1. This example is useful for a proximity exposure device or the like which needs high accuracy in pattern printing size.
The operating conditions and Fresnel lens data are shown in Table 13 and a ray tracing view in accordance with these Fresnel lenses FL.sub.1 and FL.sub.2 is shown in FIG. 25.
In Table 13, B was the gap between the first and second Fresnel lenses FL.sub.1 and FL.sub.2, n was the refractive index of the second Fresnel lens FL.sub.2, .alpha.' was an angle which the Fresnel optical surface of the second Fresnel lens FL.sub.2 made with an optical axis, and .phi.' was a declination angle on the surface P to be irradiated, which corresponds to an outgoing angle from the second Fresnel lens FL.sub.2.
In this example, the plane of incidence of the second Fresnel lens FL.sub.2 was uniformly irradiated by the first Fresnel lens FL.sub.1, and parallel light was emitted by the second Fresnel lens FL.sub.2. The luminous flux density of this parallel light can be kept at a constant value even if a gap C between the second Fresnel lens FL.sub.2 and the surface P to be irradiated varies, and hence the gap C can be arbitrarily selected.
According to this example, therefore, an area to be irradiated, which was 1000 mm in diameter, can be uniformly irradiated all over the area while setting an optical path length at a small value (841 mm
TABLE 13______________________________________A = 210 mm B = 631 mm f = 350 mm n = n' = 1.491 .alpha..sub.2 .theta.R (mm) (deg) (deg) .phi. (deg) H (mm) .alpha.' (deg) .phi.' (deg)______________________________________ 46 105.1 12.4 4.9 99.5 99.8 0 92 119.0 23.7 8.8 189.6 107.5 0138 130.9 33.3 11.4 265.1 112.4 0184 140.6 41.2 12.7 325.6 114.7 0230 148.2 47.6 12.8 373.2 115.0 0276 154.3 52.7 12.1 410.7 113.7 0322 159.0 56.9 10.6 440.5 111.0 0368 162.7 60.3 8.7 464.4 107.3 0414 165.6 63.1 6.3 483.9 102.7 0460 167.8 65.5 3.6 500.0 97.4 0______________________________________
EXAMPLE 14
In this example a second Fresnel lens FL.sub.2 was placed in the rear of the first Fresnel lens FL.sub.1 according to the present invention. This example is useful for the lighting optical system of a proximity exposure device, as was similar to example 13.
The operating conditions and Fresnel lens data are shown in Table 14 and a ray tracing view in accordance with these Fresnel lenses FL.sub.1 and FL.sub.2 is shown in FIG. 26.
In Table 14, f.sub.1 was a focal length on an optical axis of the first Fresnel lenses FL.sub.1, and f.sub.2, was a focal length on an optical axis of the second Fresnel lens FL.sub.2.
In this practical example, a spherical mirror M.sub.O was placed in the rear of a point light source LS.
TABLE 14______________________________________A = 120 mm B = 480 mm C = 100 mm f.sub.1 = 350 mmf.sub.2 = 663 mm E = 63% n = n' = 1.5H (mm) .theta. (deg) .phi. (deg) .alpha..sub.2 (deg) R.sub.2 (mm) .alpha.' (deg)______________________________________ 25 3.29 2.16 92.3 6.90 85.69 50 6.58 4.31 94.5 13.85 81.43 75 9.88 6.43 96.8 20.90 77.27100 13.19 8.52 99.2 28.12 73.27125 16.51 10.56 101.6 35.56 69.45150 19.84 12.53 104.2 43.29 65.86175 23.19 14.44 106.8 51.40 62.50200 26.55 16.26 109.5 59.97 59.40225 29.95 17.99 112.3 69.13 56.57250 33.37 19.61 115.3 79.02 54.01275 36.82 21.10 118.4 89.82 51.73300 40.30 22.44 121.7 101.77 49.73325 43.83 23.61 125.2 115.18 48.04350 47.39 24.58 128.8 130.47 46.69375 51.01 25.29 132.8 148.25 45.71400 54.69 25.66 137.0 169.40 45.20425 58.42 25.58 141.6 195.22 45.31450 62.23 24.83 146.8 227.86 46.33475 66.11 23.03 152.8 270.92 48.87500 70.08 19.38 159.7 331.13 54.36______________________________________
EXAMPLE 15
In this example an optical lighting system comprising a Fresnel lens FL was used in a projection system in which irradiance on a surface P to be irradiated was higher in the peripheral portion of the surface P. The operating parameters and lens data are shown in Table 15 and a ray tracing view in accordance with this Fresnel lens FL is shown in FIG. 27.
In this practical example, a spherical mirror M.sub.O was placed in the rear of a point light source LS.
TABLE 15______________________________________A = 120 mm B = 480 mm f = 450 mm E = 68% n = 1.5 relativeH (mm) .theta. (deg) .phi. (deg) .alpha..sub.2 (deg) R.sub.2 (mm) irradiated______________________________________ 25 3.0 2.2 91.6 6.3 1.00 50 6.0 4.4 93.3 12.7 1.00 75 9.1 6.6 95.0 19.3 1.00100 12.2 8.7 96.8 25.9 1.02125 15.3 10.8 98.8 32.9 1.03150 18.4 12.8 100.8 40.1 1.04175 21.6 14.8 103.1 47.7 1.06200 24.9 16.7 105.6 55.8 1.08225 28.2 18.4 108.3 64.5 1.10250 31.7 20.1 111.3 74.1 1.12275 35.2 21.6 114.5 84.6 1.15300 38.8 22.9 118.1 96.4 1.18325 42.5 24.1 122.1 110.0 1.22350 46.3 25.0 126.4 125.8 1.26375 50.3 25.6 131.2 144.8 1.30400 54.5 25.7 136.6 168.3 1.34425 58.8 25.2 142.7 198.6 1.39450 63.4 23.6 149.7 239.9 1.44475 68.2 19.9 157.9 300.5 1.50500 73.3 11.7 166.9 400.5 1.56______________________________________
EXAMPLE 16
In this example an optical lighting system comprising a Fresnel lens FL was used in a projection system in which irradiance on a surface P to be irradiated was higher in the peripheral portion of the surface P, as was similar to example 15. The operating parameters and Fresnel lens data are shown in Table 16 and a ray tracing view in accordance with this Fresnel lens FL is shown in FIG. 28.
The light source LS of this practical example was formed by a surface light source which emits light only toward the Fresnel lens FL.
TABLE 16______________________________________A = 100 mm B = 600 mm f = 650 mm E = 86% n = 1.5 relativeH (mm) .theta. (deg) .phi. (deg) .alpha..sub.2 (deg) R.sub.2 (mm) irradiated______________________________________ 25 2.3 1.9 90.7 4.1 1.00 50 4.7 3.9 91.5 8.2 1.00 75 7.1 5.9 92.3 12.4 1.01100 9.5 7.8 93.2 16.7 1.02125 11.9 9.8 94.2 21.1 1.03150 14.4 11.6 95.4 25.7 1.04175 17.0 13.5 96.7 30.5 1.06200 19.6 15.3 98.2 35.6 1.08225 22.3 17.0 99.9 41.0 1.10250 25.1 18.7 101.9 46.8 1.12275 28.0 20.2 104.2 53.2 1.15300 31.0 21.7 106.8 60.2 1.18325 34.2 23.1 109.8 68.1 1.22350 37.7 24.4 113.3 77.2 1.26375 41.3 25.5 117.3 88.0 1.30400 45.3 26.4 122.0 101.2 1.34425 49.7 27.0 127.5 118.1 1.39450 54.7 27.2 134.2 141.4 1.44475 60.6 26.3 142.7 177.5 1.50500 68.0 22.7 154.6 284.1 1.56______________________________________
EXAMPLE 17
In this example a second Fresnel lens FL.sub.2 was placed in the rear of a first Fresnel lens FL.sub.1 according to the present invention and a pattern original OG was placed on a surface P to be irradiated, just behind the second Fresnel lens FL.sub.2, so that the image of the pattern original OG was projected on an image surface P' through an image-formation lens IL.
The operating conditions and Fresnel lens data are shown in Table 17 and a ray tracing view in accordance with these Fresnel lenses FL.sub.1 and FL.sub.2 is shown in FIG. 29.
n Table 17, B was the gap between the first and second Fresnel lenses FL.sub.1 and FL.sub.2, C was the a gap between the second Fresnel lens FL.sub.2 and the image-formation lens IL, n' was the refractive index of the second Fresnel lens FL.sub.2, .alpha.' was an angle which the Fresnel optical surface of the second Fresnel lens FL.sub.2 makes with an optical axis, and .phi.' was a declination angle on the surface of the original OG.
According to this example, the plane of incidence of the second Fresnel lens FL.sub.2 was uniformly irradiated by the first Fresnel lens FL.sub.1 and, therefore, the riginal OG placed ]ust in the rear of the second Fresnel lens FL.sub.2 can be uniformly irradiated. The second Fresnel lens FL.sub.2 converged light at the entrance pupil of the image-formation lens IL placed in the rear of the second Fresnel lens FL.sub.2 Thus, an ideal Koehler illumination system was implemented.
The light source LS of this practical example was formed by a point light source.
TABLE 17______________________________________A = 220 mm B = 720 mm f = 335 mm n = 1.51C = 1000 mm n' = 1.491 .alpha..sub.2 .theta.R (mm) (deg) (deg) .phi. (deg) H (mm) .alpha.' (deg) .phi.' (deg)______________________________________ 47.5 105.7 12.2 4.1 99.2 100.0 -5.7 95 119.8 23.4 7.5 189.1 122.1 -10.7 142.5 131.6 32.9 9.6 264.8 129.4 -14.8190 141.0 40.8 10.7 325.8 133.1 -18.0 237.5 148.4 47.2 10.7 374.0 134.7 -20.5285 154.0 52.3 10.0 412.0 134.9 -22.4 332.5 158.4 56.5 8.7 442.3 134.3 -23.9380 161.8 59.9 6.9 446.7 133.1 -25.0 427.5 164.5 62.8 4.7 486.6 131.4 -25.9475 166.5 65.2 2.2 503.0 129.3 -26.7______________________________________
EXAMPLE 18
In this example a second Fresnel lens FL.sub.2 was placed in the rear of the first Fresnel lens FL.sub.1 according to the present invention. This example is useful for the lighting optical system of a projection device, as is similar to example 17.
The operating conditions and Fresnel lens data are shown in Table 18 and a ray tracing view in accordance with these Fresnel lenses F.sub.1 and FL.sub.2 is shown in FIG. 30.
In this example, a spherical mirror M.sub.O was placed in the rear of a point light source LS.
TABLE 18______________________________________A = 120 mm B = 480 mm C = 1000 mm f.sub.1 = 350 mmf.sub.2 = 399 mm n = n' = 1.5 E = 63% relativeH .theta. .phi. .alpha..sub.2 .alpha.' irradi-(mm) (deg) (deg) (deg) R.sub.2 (mm) .phi.' (deg) (deg) ated______________________________________ 25 3.29 2.16 92.3 6.90 -1.43 97.1 1.000 50 6.58 4.31 94.5 13.85 -2.86 104.1 1.000 75 9.88 6.43 96.8 20.90 -4.29 110.1 1.000100 13.19 8.52 99.2 28.12 -5.71 116.4 1.000125 16.51 10.56 101.6 35.56 -7.13 121.7 1.000150 19.84 12.53 104.2 43.29 -8.53 126.4 1.000175 23.19 14.44 106.8 51.40 -9.93 130.5 1.000200 26.55 16.26 109.5 59.97 -11.31 134.0 1.000225 29.95 17.99 112.3 69.13 -12.68 137.0 1.000250 33.37 19.61 115.3 79.02 -14.04 139.6 1.000275 36.82 21.10 118.4 89.82 -15.38 141.8 1.000300 40.30 22.44 121.7 101.77 -16.70 143.6 1.000325 43.83 23.61 125.2 115.18 -18.00 145.1 1.000350 47.39 24.58 128.8 130.47 -19.29 146.3 1.000375 51.01 25.29 132.8 148.25 -20.56 147.2 1.000400 54.69 25.66 137.0 169.40 -21.80 147.7 1.000425 58.42 25.58 141.6 195.22 -23.03 147.9 1.000450 62.23 24.83 146.8 227.86 -24.23 147.5 1.000475 66.11 23.03 152.8 270.92 -25.41 146.4 1.000500 70.08 19.38 159.7 331.13 -26.57 143.9 1.000______________________________________
EXAMPLE 19
In this example an optical lighting system comprising a mirror optical system M was used in a contact or proximity exposure system in which irradiance on a surface P to be irradiated was uniform all over the surface P. The operating conditions and mirror data are shown in Table 19 and a ray tracing view in accordance with this mirror optical system M is shown in FIG. 31.
The light source LS was formed by a point light source.
TABLE 19______________________________________A = 50 mm B = 800 mm f = 70 mm E = 76%H (mm) .theta. (deg) .phi. (deg) .alpha..sub.3 (deg) R.sub.3 (mm) D.sub.3 (mm)______________________________________ 25.0 4.8 1.4 88.3 4.2 0.0 50.0 9.7 2.9 86.9 8.5 0.2 75.0 14.6 4.4 84.8 12.9 0.5100.0 19.6 5.8 83.1 17.4 1.0125.0 24.6 7.3 81.3 22.1 1.6150.0 29.6 8.7 79.5 27.0 2.5175.0 34.7 10.1 77.6 32.2 3.5200.0 39.9 11.5 75.7 37.8 4.8225.0 45.2 12.8 73.7 43.8 6.5250.0 50.7 14.1 71.7 50.5 8.6275.0 56.2 15.3 69.5 58.0 11.2300.0 61.9 16.5 67.2 66.5 14.6325.0 67.9 17.6 64.8 76.4 18.9350.0 74.0 18.6 62.3 88.1 24.8375.0 80.4 19.5 59.5 102.5 32.8400.0 87.2 20.2 56.5 120.7 44.2425.0 94.4 20.7 53.1 144.9 61.3450.0 102.2 20.8 49.3 179.0 88.7475.0 110.7 20.2 44.7 230.9 137.3500.0 120.2 17.8 38.7 318.2 235.7______________________________________
EXAMPLE 20
In this example an optical lighting system comprising a mirror optical system M was used in a contact or proximity exposure system n which irradiance on a surface P to be irradiated was uniform all over the surface P, as was similar to example 19. The operating conditions and mirror data are shown in Table 20 and a ray tracing view in accordance with this mirror optical system M is shown in FIG. 32.
The light source LS was a surface light source which emits light only toward the mirror M. The size of the surface light source was assumed to be negligible.
TABLE 20______________________________________A = 50 mm B = 800 mm f = 120 mm E = 84%H (mm) .theta. (deg) .phi. (deg) .alpha..sub.3 (deg) R.sub.3 (mm) D.sub.3 (mm)______________________________________ 25.0 2.7 1.6 89.4 2.4 0.0 50.0 5.5 3.2 88.8 4.8 0.0 75.0 8.3 4.8 88.2 7.3 0.1100.0 11.1 6.4 87.6 9.8 0.2125.0 14.0 8.0 87.0 12.3 0.3150.0 16.8 9.5 86.3 15.0 0.4175.0 19.7 11.1 85.6 17.7 0.6200.0 22.7 12.6 84.9 20.6 0.9225.0 25.8 14.1 84.1 23.6 1.1250.0 28.9 15.6 83.3 26.7 1.5275.0 32.1 17.0 82.4 30.2 1.9300.0 35.4 18.4 81.4 33.8 2.4325.0 38.9 19.8 80.4 37.9 3.1350.0 42.6 21.1 79.2 42.4 3.9375.0 46.5 22.3 77.9 47.5 4.9400.0 50.7 23.5 76.4 53.4 6.3425.0 55.3 24.7 74.6 60.5 8.1450.0 60.5 25.7 72.5 69.5 10.7475.0 66.8 26.6 69.8 81.8 14.9500.0 75.4 27.1 65.8 102.3 23.3______________________________________
EXAMPLE 21
In this example an optical lighting system comprising a mirror optical system M was used in a contact or proximity exposure system in which irradiance on a surface P to be irradiated was uniform all over the surface P, as was similar to example 19. The operating parameters and mirror data are shown in Table 21 and a ray tracing view in accordance with this mirror optical system M is shown in FIG. 33.
The light source LS was a surface light source which emits light only toward the mirror M and was negligible in size. The declination angle was smaller than 3.degree. and hence this example can be utilized in a proximity exposure system.
TABLE 21______________________________________A = 455 mm B = 900 mm f = 526 mm E = 68%H (mm) .theta. (deg) .phi. (deg) .alpha..sub.3 (deg) R.sub.3 (mm) D.sub.3 (mm)______________________________________ 25.0 2.4 0.3 88.9 19.7 0.1 50.0 4.9 0.6 87.8 39.5 0.7 75.0 7.4 0.9 86.7 59.4 1.6100.0 9.9 1.3 85.6 79.6 3.0125.0 12.5 1.5 84.5 100.0 4.7150.0 15.0 1.8 83.3 120.7 6.9175.0 17.6 2.1 82.2 141.8 9.6200.0 20.3 2.3 81.0 163.5 12.8225.0 22.9 2.5 79.7 185.8 16.5250.0 25.7 2.6 78.4 208.8 21.0275.0 28.4 2.7 77.1 232.7 26.1300.0 31.3 2.7 75.7 257.6 32.1325.0 34.3 2.7 74.2 283.8 39.1350.0 37.3 2.5 72.6 311.4 47.4375.0 40.5 2.3 70.8 340.7 57.1400.0 43.9 1.9 68.9 372.2 68.6425.0 47.4 1.2 66.9 406.4 82.4450.0 51.3 0.4 64.5 444.0 99.4475.0 55.4 -0.8 61.8 486.1 120.6500.0 60.1 -2.6 58.6 534.4 148.2______________________________________
EXAMPLE 22
In this example an optical lighting system comprising a mirror optical system M was used in a projection system in which irradiance on a surface P to be irradiated was higher in the peripheral portion of the surface P. The operating parameters and mirror data are shown in Table 22 and a ray tracing view in accordance with this mirror optical system M is shown in FIG. 34.
This example utilized an image-formation lens, the effective field angle of which is defined to be 45.degree., and was adapted to unify the irradiance of an image surface.
TABLE 22______________________________________A = 50 mm B = 800 mm f = 75 mm E = 72%H R.sub.3 D.sub.3 relative(mm) .theta. (deg) .phi. (deg) .alpha..sub.3 (deg) (mm) (mm) irradiated______________________________________ 25.0 4.2 1.5 88.6 3.7 0.0 1.00 50.0 8.6 3.0 87.2 7.5 0.2 1.00 75.0 12.9 4.5 85.8 11.3 0.4 1.01100.0 17.3 6.0 84.3 15.3 0.7 1.01125.0 21.7 7.5 82.8 19.4 1.2 1.02150.0 26.2 8.9 81.3 23.8 1.8 1.03175.0 30.9 10.4 79.7 28.3 2.5 1.04200.0 35.6 11.8 78.0 33.3 3.5 1.06225.0 40.5 13.1 76.3 38.6 4.7 1.07250.0 45.5 14.5 74.4 44.5 6.2 1.09275.0 50.7 15.7 72.5 51.1 8.2 1.15300.0 56.1 17.0 70.4 58.5 10.7 1.13325.0 61.8 18.1 68.1 67.2 14.0 1.15350.0 67.8 19.2 65.7 77.4 18.3 1.18375.0 74.1 20.1 63.0 90.0 24.4 1.20400.0 80.8 20.9 60.0 105.8 33.0 1.23425.0 88.1 21.5 56.7 126.8 45.9 1.27450.0 96.1 21.8 52.8 156.1 66.7 1.30475.0 104.9 21.4 48.2 200.7 103.5 1.34500.0 115.0 19.7 42.3 276.7 179.1 1.38______________________________________
EXAMPLE 23
In this example an optical lighting system comprising a mirror optical system M was used in a projection system in which irradiance on a surface P to be irradiated was higher in the peripheral portion of the surface P, as was similar to example 2. Operating conditions and mirror data are shown in Table 23 and a ray tracing view in accordance with this mirror optical system M is shown in FIG. 35.
This example utilized an image-formation lens, the effective field angle of which was defined to unify the irradiance of an image surface.
The light source LS was formed by a surface light source which emits light only toward the mirror M and was negligible in size.
TABLE 23______________________________________A = 50 mm B = 800 mm f = 150 mm E = 84%H R.sub.3 D.sub.3 relative(mm) .theta. (deg) .phi. (deg) .alpha..sub.3 (deg) (mm) (mm) irradiated______________________________________ 25.0 2.4 1.6 89.5 2.1 0.0 1.00 50.0 4.9 3.2 89.1 4.3 0.0 1.00 75.0 7.4 4.8 88.7 6.4 0.0 1.01100.0 9.9 6.5 88.2 8.7 0.1 1.02125.0 12.4 8.1 87.8 11.0 0.2 1.03150.0 15.0 9.6 87.3 13.3 0.3 1.04175.0 17.7 11.2 86.7 15.8 0.4 1.06200.0 20.4 12.7 86.1 18.4 0.5 1.08225.0 23.2 14.3 85.5 21.1 0.7 1.10250.0 26.2 15.7 84.7 24.1 1.0 1.12275.0 29.2 17.2 83.9 37.2 1.3 1.15300.0 32.5 18.6 83.0 30.7 1.7 1.18325.0 35.9 20.0 82.0 34.6 2.2 1.22350.0 39.5 21.3 80.8 38.9 2.0 1.26375.0 43.5 22.5 79.5 43.9 3.7 1.30400.0 47.8 23.7 77.9 49.7 4.9 1.34425.0 52.6 24.8 76.1 56.9 6.5 1.39450.0 58.2 25.8 73.7 66.2 9.0 1.44475.0 65.1 26.6 70.7 79.3 13.2 1.50500.0 75.0 27.0 65.9 102.7 22.6 1.56______________________________________
EXAMPLE 24
In this example an optical lighting system comprising a Fresnel mirror FM was used in a contact or proximity exposure system in which irradiance on a surface P to be irradiated was uniform all over the surface P. Operating conditions and mirror data are shown in Table 24 and a ray tracing view in accordance with this Fresnel mirror FM is shown in FIG. 36.
A light source LS was assumed to be formed by a point light source which has uniform radiant intensity J(.theta.).
TABLE 24______________________________________A = 150 mm B = 600 mm f = 2000 mm E = 40%H (mm) .theta. (deg) .phi. (deg) .alpha..sub.3 (deg) R.sub.3 (mm)______________________________________ 25 1.9 1.9 89.9 5.0 50 3.9 3.7 89.9 10.2 75 5.9 5.6 89.8 15.6100 8.0 7.4 89.6 21.3125 10.3 9.2 89.4 27.3150 12.7 10.9 89.1 33.9175 15.2 12.5 88.6 40.9200 17.9 14.1 88.0 48.6225 20.8 15.6 87.4 57.0250 23.8 17.0 86.6 66.1275 26.9 18.3 85.6 76.2300 30.2 19.5 84.6 87.3325 33.6 20.5 83.4 99.6350 37.1 21.5 82.1 113.5375 40.7 22.2 80.7 129.3400 44.5 22.8 79.1 147.6425 48.4 23.0 77.3 169.1450 52.4 23.0 75.2 195.0475 56.5 22.4 72.9 227.2500 60.8 21.0 70.1 268.7______________________________________
EXAMPLE 25
In this example an opticaI lighting system comprising a Fresnel mirror FM was used in a contact or proximity exposure system in which irradiance on a surface P to be irradiated was uniform all over the surface P, as was similar to the twenty-fourth practical example. Operating parameters and mirror data are shown in Table 25 and a ray tracing view in accordance with this Fresnel mirror FM is shown in FIG. 37.
The light source LS was formed by a surface illuminant which emitted light only toward the mirror M and was negligible in size.
TABLE 25______________________________________A = 100 mm B = 800 mm f = 220 mm E = 78%H (mm) .theta. (deg) .phi. (deg) .alpha..sub.3 (deg) R.sub.3 (mm)______________________________________ 25 2.6 1.4 89.3 4.6 50 5.3 2.9 88.7 9.3 75 8.0 4.3 88.1 14.1100 10.7 5.7 87.5 18.9125 13.4 7.1 86.8 23.9150 16.2 8.5 86.1 29.1175 19.0 9.9 85.4 34.5200 21.8 11.2 84.7 40.1225 24.8 12.5 83.8 46.2250 27.7 13.8 83.0 52.6275 30.8 15.0 82.1 59.7300 34.0 16.2 81.0 67.4325 37.2 17.2 79.9 76.1350 40.7 18.2 78.7 86.1375 44.3 19.1 77.3 97.7400 48.2 19.8 75.7 111.9425 52.4 20.2 73.9 129.8450 57.0 20.2 71.6 154.1475 62.3 19.5 68.6 190.6500 68.7 16.8 64.0 257.5______________________________________
EXAMPLE 26
In this example an optical lighting system comprising a Fresnel mirror FM was used in a projection system in which irradiance on a surface P to be irradiated was higher in the peripheral portion of the surface P. Operating parameters and mirror data are shown in Table 26 and a ray tracing view in accordance with this Fresnel mirror FM is shown in FIG. 38.
This example used an image-formation lens, the effective field angle of which was assumed to be 45.degree., and was adapted to unify the irradiance of an image surface.
A light source LS was formed by a point light source which is assumed to be uniform in radiant intensity J(.theta.).
TABLE 26______________________________________A = 150 mm B = 600 mm f = 2000 mm E = 37% relativeH (mm) .theta. (deg) .phi. (deg) .alpha..sub.3 (deg) R.sub.3 (mm) irradiated______________________________________ 25 2.4 1.3 89.4 6.4 1.00 50 4.9 2.6 88.8 13.0 1.01 75 7.4 3.9 88.2 19.6 1.01100 10.0 5.2 87.6 26.5 1.02125 12.6 6.5 86.9 33.6 1.03150 15.2 7.7 86.2 41.0 1.05175 18.0 8.9 85.4 48.8 1.06200 20.8 10.1 84.6 57.1 1.08225 23.7 11.2 83.7 66.1 1.10250 26.8 12.2 82.7 75.8 1.13275 29.9 13.2 81.6 86.5 1.16300 33.2 14.1 80.4 98.3 1.19325 36.6 14.9 79.1 111.6 1.22350 40.2 15.5 77.6 126.7 1.26375 43.9 16.0 76.0 144.4 1.30400 47.7 16.3 74.2 165.4 1.35425 51.8 16.3 72.2 191.0 1.39450 56.1 15.8 69.8 223.4 1.45475 60.6 14.6 66.9 266.4 1.50500 65.3 12.2 63.4 326.9 1.56______________________________________
EXAMPLE 27
In this example an optical lighting system comprising a Fresnel mirror FM was used in a projection system in which irradiance on a surface P to be irradiated was higher in the peripheral portion of the surface P. The operating parameters and mirror data are shown in Table 27 and a ray tracing view in accordance with this Fresnel mirror FM is shown in FIG. 39.
A light source LS was formed by a surface light source which emitted light only toward the mirror M and was negligible in size.
TABLE 27______________________________________A = 100 mm B = 800 mm f = 260 mm E = 82% relativeH (mm) .theta. (deg) .phi. (deg) .alpha..sub.3 (deg) R.sub.3 (mm) irradiated______________________________________ 25 2.4 1.4 89.5 4.2 1.00 50 4.8 2.9 89.0 8.4 1.00 75 7.2 4.4 88.5 12.8 1.01100 9.7 5.9 88.0 17.2 1.01125 12.2 7.3 87.5 21.7 1.03150 14.8 8.7 86.9 26.4 1.04175 17.4 10.1 86.3 31.4 1.06200 20.1 11.5 85.6 36.6 1.08225 22.9 12.8 84.9 42.2 1.10250 25.8 14.1 84.1 48.3 1.12275 28.8 15.3 83.2 55.0 1.15300 31.9 16.5 82.2 62.4 1.18325 35.3 17.6 81.1 70.8 1.22350 38.8 18.6 79.8 80.5 1.26375 42.6 19.4 78.3 92.2 1.30400 46.8 20.1 76.6 106.8 1.34425 51.5 20.4 74.4 125.9 1.39450 56.9 20.3 71.7 153.4 1.44475 63.3 19.0 67.8 199.4 1.50500 72.1 13.3 60.6 309.7 1.56______________________________________
Although the above Examples 1-18 have been described with respect to a lens optical system which has a spherical incidence plane surface, the plane of incidence may be an aspheric surface as is similar to the outgoing plane F.sub.2 of the lens optical system.
Further, the light source LS may be a secondary light source formed by converging means such as another reflecting mirror.
Although the present invention has been described and illustrated in connection with preferred embodiments thereof, many other variations and modifications will now become apparent to those skilled in the art without departing from the scope of the invention. It is preferred therefore that the present invention be limited not by the specific disclosure herein, but only by the appended claims.

Number	Date	Country	Kind
62-193330	Jul 1987	JPX
63-153305	Jun 1988	JPX

Number	Name	Date
4242725	Douma et al.	Dec 1980
4853749	Sorensen	Aug 1989
5010465	Endo et al.	Apr 1991

Lighting optical system

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