Projection optical system

Abstract

The projection optical system uses a plurality of wavelengths or a wavelength band within a wavelength range from a visible region to a near ultraviolet region. The double-telecentric projection optical system includes: a first lens group with a positive power; a second lens group with a negative power, including a predetermined lens or lenses; and a third lens group with a positive power, including a stop and at least two positive lenses satisfying a predetermined condition relating to refractive index. The projection optical system satisfies a predetermined condition relating to a composite focal length of the first lens group and the second lens group, and a focal length of the third lens group.

Description

This application is based on Japanese Patent Application No. 2009-140843 filed on Jun. 12, 2009, in Japanese Patent Office, the entire content of which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a projection optical system with a double telecentricity in which a principal ray is almost parallel with the optical axis at both of the incident side and the outgoing side of the optical system.

BACKGROUND

In a double-telecentric optical system, its magnification almost does not change even when the optical system shifts in the optical axis direction compared with an object plane or an image plane. Therefore, a double-telecentric projection optical system is preferably used in a situation that such the characteristic is required. For example, when a double-telecentric optical system is used as a projection optical system, it can reduce an influence of a distortion caused by a displacement of the focal position and an influence of a warp of the object plane and the image plane (projection plane). When it is used as an inspection optical system, it enables precise inspection by providing deep depth of field even if an object has an uneven surface, and further enables to avoid a positioning error of an imaging element such as CCD.

As such the projection optical system, there has been known an achromatic lens system achromatized for g-line, h-line and i-line (for example, U.S. Pat. No. 5,159,496). The lens system includes a stop, a front lens system arranged at the front of the stop, and a rear lens system arranged at the rear of the stop. In the lens system, two meniscus lenses with negative power whose concave surfaces face the stop, are arranged in each of the front lens system and the rear lens system. Further, there has been known a double-telecentric projection optical system with a magnification of about 1× which is achromatized for g-line, h-line and i-line, and includes a front lens group and a rear lens group arranged to be almost symmetrical about a pupil plane (for example, JP-A No. 2002-14281). There has further been known a double-telecentric optical system with a magnification of about 3× at the enlargement side (for example, JP-A No. 2004-354805).

In view of various uses for a double-telecentric projection optical system, a double-telecentric projection optical system preferably uses a plural wavelength bands at the same time or uses one of the plural wavelength bands while the wavelength band are changed at need. At this case, the projection optical system is needed to be achromatized for the plural wavelength bands to be used.

However, in the achromatic lens system described in U.S. Pat. No. 5,159,496, longitudinal chromatic aberration is insufficiently corrected, which results in a unsatisfactory property. The double-telecentric projection optical system described in JP-A No. 2002-14281 has a problem in its large chromatic aberration. The double-telecentric optical system described in JP-A No. 2004-354805 has a sufficient property for a single wavelength but has a slight difficulty as an optical system using plural wavelengths.

SUMMARY

A double-telecentric projection optical system as an embodiment of the present invention is a double-telecentric projection optical system comprising, in order from a enlargement side: a first lens group with a positive power, including a first lens arranged at a closest position to the enlargement side in the projection optical system; a second lens group with a negative power, including a lens or lenses which start with a negative lens that is a first negative lens to satisfy |Hn/Y|<0.75 from the enlargement side in the projection optical system, and which end with a lens that is the first to satisfy Ln/L1a>0.15 from the enlargement side among the negative lens and lenses at the rear of the negative lens in the projection optical system; and a third lens group with a positive power, including a stop and lenses at the rear of the second lens group. The lenses in the third lens group include at least two positive lenses satisfying 0.662<0.00055×νh+P. The projection optical system uses a plurality of wavelengths or a wavelength band covering a predetermined range each of which is within a wavelength range from a visible region to a near ultraviolet region. The projection optical system satisfies the following expression.1<|f12/f3|<5  (1)

Herein, Hn is a height (mm) of an outermost off-axis principal ray, measured from an optical axis when the outermost off-axis principal ray passes through an enlargement-side surface of an n-th lens,

Y is a maximum image height (mm) at the enlargement side,

Ln is a distance of an air space between an n-th lens and an (n+1)-th lens,

L1a is a distance from an apex of an enlargement-side surface of the first lens to a surface of the stop,

νh is defined as (Nh−1)/(Ni−Ng),

P is defined as P=(Ni−Nh)/(Ni−Ng),

Nh is a refractive index at h-line,

Ni is a refractive index at i-line,

Ng is a refractive index at g-line,

f12 is a composite focal length (mm) of the first lens group and the second lens group, and

f3 is a focal length (mm) of the third lens group,

where each of the n-th lens for Hn and Ln is an n-th lens to be arranged from the enlargement side in the projection optical system and each n is independently an integer of one or more.

These and other objects, features and advantages according to the present invention will become more apparent upon reading of the following detailed description along with the accompanied drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements numbered alike in several Figures, in which:

FIG. 1 is a cross sectional view showing a structure of a double-telecentric projection optical system of Example 1;

FIGS. 2 a to 2d are drawings showing spherical aberration and astigmatism of the projection optical system of Example 1;

FIGS. 3 a and 3b are drawings showing distortion and chromatic aberration of magnification of the projection optical system of Example 1;

FIG. 4 is a cross sectional view showing a structure of a double-telecentric projection optical system of Example 2;

FIGS. 5 a to 5d are drawings showing spherical aberration and astigmatism of the projection optical system of Example 2;

FIGS. 6 a and 6b are drawings showing distortion and chromatic aberration of magnification of the projection optical system of Example 2;

FIG. 7 is a cross sectional view showing a structure of a double-telecentric projection optical system of Example 3;

FIGS. 8 a to 8d are drawings showing spherical aberration and astigmatism of the projection optical system of Example 3;

FIGS. 9 a and 9b are drawings showing distortion and chromatic aberration of magnification of the projection optical system of Example 3,

FIG. 10 is a cross sectional view showing a structure of a double-telecentric projection optical system of Example 4;

FIGS. 11 a to 11d are drawings showing spherical aberration and astigmatism of the projection optical system of Example 4; and

FIGS. 12 a and 12b are drawings showing distortion and chromatic aberration of magnification of the projection optical system of Example 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereafter, although embodiments of the present invention will be described in details, the present invention is not limited to the embodiments.

One embodiment of the present invention is a projection optical system with a double telecentricity which uses a plurality of wavelengths or a wavelength band covering a predetermined range each of which is within a wavelength range from a visible region to a near ultraviolet region. The projection optical system with a double telecentricity comprises, in order from a enlargement side to a reducing side: a first lens group with a positive power, including a first lens arranged at a closest position to the enlargement side in the projection optical system; a second lens group with a negative power, including a lens or lenses which start with a negative lens that is a first negative lens to satisfy |Hn/Y|<0.75 from the enlargement side in the projection optical system, and which end with a lens that is the first to satisfy Ln/L1a>0.15 from the enlargement side among the negative lens and lenses at the rear of the negative lens in the projection optical system; and a third lens group with a positive power, including a stop and lenses at the rear of the second lens group, where the lenses in the third lens group include at least two positive lenses satisfying 0.662<0.00055×νh+P. The projection optical system satisfies the following expression (1).1<|f12/f3|<5  (1)

Herein, Hn is a height (mm) of an outermost off-axis principal ray, measured from an optical axis when the outermost off-axis principal ray passes through an enlargement-side surface of an n-th lens,

Y is a maximum image height (mm) at the enlargement side,

Ln is a distance of an air space between an n-th lens and an (n+1)-th lens,

L1a is a distance from an apex of an enlargement-side surface of the first lens to a surface of the stop,

νh is defined as (Nh−1)/(Ni−Ng),

P is defined as P=(Ni−Nh)/(Ni−Ng),

Nh is a refractive index at h-line,

Ni is a refractive index at i-line,

Ng is a refractive index at g-line,

f12 is a composite focal length (mm) of the first lens group and the second lens group, and

f3 is a focal length (mm) of the third lens group.

In these definition, each of the n-th lens for Hn and Ln is an n-th lens to be arranged from the enlargement side in the projection optical system and each n is independently an integer of one or more.

The term “enlargement side” represents a side of the projection optical system at which an outermost off-axis principal my is higher than that at the other side, between both sides of the projection optical system. The term “reduction side” represents a side of the projection optical system at which an outermost off-axis principal ray is lower than that at the other, between the both sides of the projection optical system.

The term “double-telecentricity” represents a condition that each of the outermost off-axis principal rays at the both sides of the projection optical system forms an angle of 2° or less with the optical axis.

Such the lens-group construction exhibits an efficiently corrected chromatic aberration with maintaining a telecentricity. When the projection optical system employs a plurality of the above positive lenses, the secondary spectrum can be reduced efficiently, and chromatic aberration, especially a longitudinal chromatic aberration can be sufficiently corrected. When the projection optical system satisfies the above expression (1) relating to a focal length, aberrations, especially a spherical aberration can be corrected, while the telecentricity and a desired projection magnification are sufficiently maintained. Since the projection optical system employs a double-telecentric system, rays travel the optical system smoothly and occurrence of aberrations can be minimized.

When a value of the expression (1) is less than the lower limit, the projection optical system easily diverges rays excessively under a projection with a desired projection magnification, which makes maintaining telecentricity difficult. When the value of the expression (1) exceeds the upper limit, the projection optical system easily converges rays excessively under a projection with a desired projection magnification, which makes maintaining telecentricity difficult, too.

As for the above conditional expression, the following range is preferable.1.5<|f12/f3|<4.5  (1′)

The double-telecentric projection optical system preferably satisfies the following expression.0.04<|f1/f12|<0.6  (2)

In the expression, f1 is a focal length (mm) of the first lens group.

By forming the first lens group so as to satisfy the expression (2), the telecentricity is easily ensured.

When a value of the expression (2) is lower than the upper limit, the telecentricity can be easily maintained, because the first lens group does not have an excessively weak power. When the value of the expression (2) exceeds the lower limit, curvature of field is sufficiently corrected, because the first lens group does not have an excessively strong power.

As for the above conditional expression, the following range is preferable.0.05<|f1/f12|<0.5  (2′)

The double-telecentric projection optical system preferably satisfies the following expression.0.01<|f2/f12|<0.5  (3)

In the expression, f2 is a focal length (mm) of the second lens group.

By providing strong negative power for the first lens group so as to satisfy the expression (3), Petzval sum can be reduced with maintaining a sufficient telecentricity. Therefore, curvature of field can be reduced.

When a value of the expression (3) is lower than the upper limit, curvature of field can be sufficiently corrected, because the second lens group does not have an excessively weak power. When the value of the expression (3) exceeds the lower limit, desired projection magnification can be maintained, because composite power of the first lens group and the second lens group does not become excessively weak.

As for the above conditional expression, the following range is preferable.0.02<|f2/f12|<0.4  (3′)

The double-telecentric projection optical system preferably satisfies the following expression.0.25<|f2/f1|<0.8  (4)

By providing strong negative power for the second lens group so as to satisfy the expression (4), Petzval sum can be reduced with maintaining a sufficient telecentricity. Therefore, curvature of field can be reduced.

When a value of the expression (4) is lower than the upper limit, curvature of field can be sufficiently corrected, because the second lens group does not have an excessively weak power. When the value of the expression (4) exceeds the lower limit, the telecentricity can be easily maintained, because the first lens group does not have an excessively weak power.

As for the above conditional expression, the following range is preferable.0.3<|f2/f1|<0.75  (4′)

In the double-telecentric projection optical system, it is preferable that each of the at least two positive lenses satisfying 0.662<0.00055×νh+P in the third lens group satisfies the following expression.|Hn_min/Y|<0.3  (5)

In the expression, Hn_min is smaller one (mm) of a height of an outermost off-axis principal ray measured when the outermost off-axis principal ray passes through an enlargement-side surface of each of the at least two positive lenses and a height of an outermost off-axis principal ray measured when the outermost off-axis principal ray passes a reduction-side surface of each of the at least two positive lenses.

By arranging the positive lenses satisfying |Hn_min/Y|<0.3 at a position where the principal ray passes lower position so as to satisfy the expression (5), longitudinal chromatic aberration can be corrected more efficiently.

As for the above conditional expression, the following range is preferable.|Hn_min/Y|<0.25  (5′)

In the double-telecentric projection optical system, it is preferable that the third lens group includes at least three positive lenses and at least two negative lenses. This structure allows the double-telecentric projection to correct longitudinal chromatic aberration more efficiently with maintaining a telecentricity.

In the double-telecentric projection optical system, it is preferable that the first lens arranged at the closest position to the enlargement side in the first lens group is a biconvex positive lens. This structure allows the double-telecentric projection to maintain a telecentricity easily.

In the double-telecentric projection optical system, it is preferable that the first lens group includes at least two positive lenses. This structure allows the double-telecentric projection to maintain a telecentricity easily, although the total dimension of the optical system is short.

In the double-telecentric projection optical system, it is preferable that the first lens includes a positive lens, a negative lens, a positive lens which are arranged in order from the enlargement side. This structure allows the double-telecentric projection to maintain a telecentricity easily and to correct distortion effectively.

The double-telecentric projection optical system preferably satisfies the following expression.0.1<LB/TL<0.5  (6)

In the expression, LB is a backside length of the projection optical system at a reduction side and

TL is a total length of the projection optical system.

When a value of the expression (6) is lower than the upper limit, various aberrations can be properly corrected, because the backside length at a reduction side of the projection optical system does not become excessively long. Further, the total size of the optical system does become large. When the value of the expression (6) exceeds the lower limit, members such as a lens-holding member do not interfere with the projection optical system.

As for the above conditional expression, the following range is preferable.0.1<LB/TL<0.4  (6′)

EXAMPLES

Examples of the double-telecentric projection optical system relating to the above embodiment will be described below.

In the examples, the following symbols are used. In the following descriptions, an “n-th lens” means the n-th lens to be arranged from the enlargement side in a projection optical system, where each n is independently an integer of one or more.

i: Surface number

R: Curvature radius (mm)

d: Axial distance of surfaces (mm)

H: Height (mm) of an outermost off-axis principal ray, measured from an optical axis when the outermost off-axis principal ray passes through an n-th lens

Hn: Height (mm) of an outermost off-axis principal ray, measured from an optical axis when the outermost off-axis principal ray passes through an enlargement-side surface of an n-th lens

Y: Maximum image height (mm) at the enlargement side

Ln: Distance of an air space between an n-th lens and an (n+1)-th

L1a: Distance from an apex of an enlargement-side surface of the first lens to a surface of the stopνh=(Nh−1)/(Ni−Ng)P=(Ni−Nh)/(Ni−Ng)

Ni: Refractive index at i-line (365 nm)

Nh: Refractive index at h-line (405 nm)

Ng: Refractive index at g-line (436 nm)

f12: Composite focal length (mm) of the first lens group and the second lens group

f1: Focal length (mm) of the first lens group

f2: Focal length (mm) of the second lens group

f3: Focal length (mm) of the third lens group

LB: Backside length of the projection optical system at the reduction side

TL: Total length of the projection optical system

Hn_min: Smaller one (mm) of a height of an outermost off-axis principal ray measured when the outermost off-axis principal ray passes through an enlargement-side surface of an n-th lens and a height of an outermost off-axis principal ray measured when the outermost off-axis principal ray passes a reduction-side surface of the n-th lens

Example 1

Example 1 will be described below.

Table 1 shows lens-surface data of the projection optical system of Example 1.

TABLE 1
i	R	d	Ni	Nh	Ng	νh	P	H
0	Object or
	Image plane
		51.490
1	101.069							15.00
		5.395	1.636137	1.622592	1.615047	29.5	0.642
2	−327.642							14.77
		95.224
3	−35.405							3.11
		2.594	1.636137	1.622592	1.615047	29.5	0.642
4	−101.451							3.00
		11.252
5	47.870							2.04
		3.005	1.449860	1.446451	1.444423	82.1	0.627
6	−46.719							1.83
		4.966
7	−32.339							1.22
		3.192	1.535785	1.529768	1.526214	55.4	0.629
8	40.970							1.01
		3.223
9	136.729							0.72
		3.317	1.449860	1.446451	1.444423	82.1	0.627
10	−50.706							0.52
		2.079
11	Stop							0.32
		1.467
12	40.673							0.18
		2.825	1.449860	1.446451	1.444423	82.1	0.627
13	−32.111							0.01
		4.104
14	−29.234							0.41
		3.170	1.535785	1.529768	1.526214	55.4	0.629
15	−51.005							0.62
		42.731
16	57.655							4.83
		3.372	1.636137	1.622592	1.615047	29.5	0.642
17	−78.648							4.92
		3.156
18	−38.448							4.93
		2.838	1.504063	1.498983	1.495964	61.6	0.627
19	50.668							5.09
		9.220
20	−28.426							6.11
		3.137	1.504063	1.498983	1.495964	61.6	0.627
21	113.361							6.73
		77.168
22	705.694							27.54
		8.956	1.504063	1.498983	1.495964	61.6	0.627
23	−93.561							28.20
		0.650
24	691.691							28.69
		5.098	1.636137	1.622592	1.615047	29.5	0.642
25	130.000							28.98
		4.489
26	182.778							29.75
		8.593	1.511760	1.507205	1.504507	69.9	0.628
27	−128.267							29.96
		76.870
28	Object or							30.00
	Image plane

FIG. 1 is a cross sectional view showing a structure of the double-telecentric projection optical system of Example 1.

As shown in FIG. 1, the projection optical system of Example 1 has a 13-element structure. In Table 1, lens surfaces numbered 27 and 26 as surface number i represent the first lens L1 arranged at the closest position to the enlargement side. Lens surfaces numbered 2 and 1 as surface number i represent the thirteenth lens L13 arranged at the closest position to the reducing side.

In Example 1, the maximum image height Y at the enlargement side is 30.00. A first negative lens to satisfy |Hn/Y|<0.75 from the enlargement side in the projection optical lens is the fourth lens L4. Distance L1a from an apex of the enlargement-side surface of the first lens L1 to the surface of the stop is 180.975. A first lens to satisfy Ln/L1a>0.15 from the enlargement side among lenses from the forth lens L4 to the lens closest to the reducing side, is the sixth lens L6.

In other words, as shown in FIG. 1, there are arranged, in order from the enlargement side to the reducing side, first lens group including the first lens L1 through the third lens L3, second lens group Gr2 including the fourth lens L4 through the sixth lens L6, and third lens group Gr3 including the seventh lens L7 through the thirteenth lens L13.

In third group Gr3, positive lenses satisfying 0.662<0.00055×νh+P are three lenses of the eighth lens L8, the ninth lens L9 and the eleventh lens L11.

Table 2 shows values of Hn_min and Hn_min/Y of the eighth lens L8, the ninth lens L9 and the eleventh lens L11 which are positive lenses satisfying 0.662<0.00055×νh+P in third group Gr3 of Example 1.

	TABLE 2
	Hnmin	Hnmin/Y
	Eighth lens	0.01	0.0003
	Ninth lens	0.52	0.0173
	Eleventh lens	1.83	0.0610

As can be seen from Table 2, these lenses satisfy the expression (5): |Hn_min/Y|<0.3.

FIGS. 2 a to 2d are drawings showing spherical aberration and astigmatism of the projection optical system of Example 1. In FIG. 2a, a solid line represents spherical aberration at g-line is, a dashed line represents spherical aberration at i-line, and an alternate long and short dash line represents spherical aberration at h-line. FIG. 2b shows astigmatism at g-line, FIG. 2c shows astigmatism at h-line, and FIG. 2d shows astigmatism at i-line. In the astigmatism diagrams, a solid line represents astigmatism on a meridional image plane, and a dashed line represents astigmatism on a saggital image plane.

FIGS. 3 a and 3b are drawings showing distortion and chromatic aberration of magnification of the projection optical system of Example 1. FIG. 3a shows distortion at h-line. In the diagram showing chromatic aberration of magnification, a solid line represents the chromatic aberration at g-line, and a dashed line represents the chromatic aberration at i-line.

Example 2

Example 2 will be described below.

Table 3 shows lens-surface data of the projection optical system of Example 2.

TABLE 3
i	R	d	Ni	Nh	Ng	νh	P	H
0	Object or
	Image plane
		66.200
1	245.031							20.00
		5.202	1.636658	1.622941	1.615298	29.2	0.642
2	−179.327							19.90
		78.371
3	−75.265							10.28
		4.257	1.636658	1.622941	1.615298	29.2	0.642
4	−147.618							10.18
		0.860
5	138.208							10.06
		4.283	1.636658	1.622941	1.615298	29.2	0.642
6	−240.639							9.77
		0.860
7	105.412							9.55
		4.175	1.535785	1.529768	1.526214	55.4	0.629
8	46.916							8.95
		32.863
9	−43.820							5.93
		3.826	1.559693	1.550656	1.545503	38.8	0.637
10	5557.109							5.88
		1.901
11	96.365							5.84
		6.252	1.449860	1.446451	1.444423	82.1	0.627
12	−53.333							5.66
		3.679
13	−49.540							5.31
		3.011	1.535785	1.529768	1.526214	55.4	0.629
14	133.388							5.23
		4.785
15	−3314.774							5.15
		4.902	1.449860	1.446451	1.444423	82.1	0.627
16	−56.522							5.10
		0.860
17	229.240							5.04
		4.411	1.449860	1.446451	1.444423	82.1	0.627
18	−95.061							4.85
		0.860
19	76.624							4.75
		5.036	1.449860	1.446451	1.444423	82.1	0.627
20	−173.093							4.36
		10.701
21	73.327							2.97
		4.581	1.449860	1.446451	1.444423	82.1	0.627
22	−401.582							2.52
		10.226
23	−120.595							0.98
		3.664	1.535785	1.529768	1.526214	55.4	0.629
24	53.357							0.64
		4.657
25	Stop							0.01
		73.674
26	92.740							10.32
		5.614	1.636658	1.622941	1.615298	29.2	0.642
27	−104.161							10.51
		4.724
28	−66.176							10.53
		2.925	1.504063	1.498983	1.495964	61.6	0.627
29	54.198							10.80
		11.990
30	−42.826							12.53
		3.087	1.504063	1.498983	1.495964	61.6	0.627
31	−181.634							13.55
		68.421
32	537.808							35.37
		11.036	1.511760	1.507205	1.504507	69.9	0.628
33	−117.093							36.10
		0.871
34	−466.904							36.64
		4.527	1.636658	1.622941	1.615298	29.2	0.64
35	232.981							37.49
		6.170
36	656.500							38.63
		11.433	1.511760	1.507205	1.504507	69.9	0.628
37	−124.549							39.23
		1.027
38	1832.967							39.73
		7.298	1.636658	1.622941	1.615298	29.2	0.642
39	−500.318							39.90
		107.622
40	Object or							40.00
	Image plane

FIG. 4 is a cross sectional view showing a structure of the double-telecentric projection optical system of Example 2.

As shown in FIG. 4, the projection optical system of Example 2 has a 19-element structure. In Table 3, lens surfaces numbered 39 and 38 as surface number i represent the first lens L1 arranged at the closest position to the enlargement side. Lens surfaces numbered 2 and 1 as surface number i represent the nineteenth lens L19 arranged at the closest position to the reducing side.

In Example 2, the maximum image height Y at the enlargement side is 40.00. A first negative lens to satisfy |Hn/Y|<0.75 from the enlargement side in the projection optical lens is the fifth lens L5. Distance L1a from an apex of the enlargement-side surface of the first lens L1 to the surface of the stop is 212.798. A first lens to satisfy Ln/L1a>0.15 from the enlargement side among lenses from the fifth lens L5 to the lens closest to the reducing side, is the seventh lens L7.

In other words, as shown in FIG. 4, there are arranged, in order from the enlargement side to the reducing side, first lens group including the first lens L1 through the fourth lens L4, second lens group Gr2 including the fifth lens L5 through the seventh lens L7, and third lens group Gr3 including stop through the nineteenth lens L19.

In third group Gr3, positive lenses satisfying 0.662<0.00055×νh+P are five lenses of the ninth lens L9, the tenth lens L10, the eleventh lens L11, the twelfth lens L12, and the fourteenth lens L14.

Table 4 shows values of Hn_min and Hn_min/Y of the ninth lens L9, the tenth lens L10, the eleventh lens L11, the twelfth lens L12, and the fourteenth lens L14 which are positive lenses satisfying 0.662<0.00055×νh+P in third group Gr3 of Example 2.

	TABLE 4
	Hnmin	Hnmin/Y
	Ninth lens	2.52	0.0630
	Tenth lens	4.36	0.1090
	Eleventh lens	4.85	0.1213
	Twelfth lens	5.10	0.1275
	Fourteenth lens	5.66	0.1415

As can be seen from Table 4, these lenses satisfy the expression (5): |Hn_min/Y|<0.3.

FIGS. 5 a to 5d are drawings showing spherical aberration and astigmatism of the projection optical system of Example 2. In FIG. 5a, a solid line represents spherical aberration at g-line is, a dashed line represents spherical aberration at i-line, and an alternate long and short dash line represents spherical aberration at h-line. FIG. 5b shows astigmatism at g-line, FIG. 5c shows astigmatism at h-line, and FIG. 5d shows astigmatism at i-line. In the astigmatism diagrams, a solid line represents astigmatism on a meridional image plane, and a dashed line represents astigmatism on a saggital image plane.

FIGS. 6 a and 6b are drawings showing distortion and chromatic aberration of magnification of the projection optical system of Example 2. FIG. 6a shows distortion at h-line. In the diagram showing chromatic aberration of magnification, a solid line represents the chromatic aberration at g-line, and a dashed line represents the chromatic aberration at i-line.

Example 3

Example 3 will be described below.

Table 3 shows surface data of the projection optical system of Example 3.

TABLE 5
i	R	d	Ni	Nh	Ng	νh	P	H
0	Object or
	Image plane
		64.000
1	76.927							6.67
		4.206	1.511760	1.507205	1.504507	69.9	0.628
2	−67.734							6.56
		1.187
3	101.948							6.40
		3.499	1.607243	1.599721	1.595297	50.2	0.630
4	29.703							6.08
		2.475
5	22.475							6.06
		5.126	1.449860	1.446451	1.444423	82.1	0.627
6	−89.735							5.68
		4.363
7	−32.612							5.01
		3.042	1.607243	1.599721	1.595297	50.2	0.630
8	32.076							4.86
		3.213
9	32.210							4.95
		4.673	1.449860	1.446451	1.444423	82.1	0.627
10	−37.667							4.84
		3.297
11	21.482							4.43
		5.607	1.449860	1.446451	1.444423	82.1	0.627
12	−266.587							3.74
		2.397
13	30.000							3.21
		3.914	1.449860	1.446451	1.444423	82.1	0.627
14	98.222							2.56
		4.441
15	−23.554							1.50
		1.971	1.607243	1.599721	1.595297	50.2	0.630
16	20.293							1.25
		7.374
17	Stop							0.07
		16.966
18	102.855							2.66
		3.425	1.636137	1.622592	1.615047	29.5	0.642
19	−46.494							2.95
		25.172
20	−20.007							5.48
		2.641	1.636137	1.622592	1.615047	29.5	0.642
21	99.268							6.10
		30.651
22	−100.605							15.79
		5.600	1.511760	1.507205	1.504507	69.9	0.628
23	−33.715	5.600						16.48
		17.803
24	222.698							19.62
		8.817	1.504063	1.498983	1.495964	61.6	0.627
25	−111.344							20.00
		36.684
26	Object or							20.00
	Image plane

FIG. 7 is a cross sectional view showing a structure of the double-telecentric projection optical system of Example 3.

As shown in FIG. 7, the projection optical system of Example 3 has a 12-element structure. In Table 3, lens surfaces numbered 25 and 24 as surface number i represent the first lens L1 arranged at the closest position to the enlargement side. Lens surfaces numbered 2 and 1 as surface number i represent the twelfth lens L12 arranged at the closest position to the reducing side.

In Example 3, the maximum image height Y at the enlargement side is 20.00. A first negative lens to satisfy |Hn/Y|<0.75 from the enlargement side in the projection optical lens is the third lens L3. Distance L1a from an apex of the enlargement-side surface of the first lens L1 to the surface of the stop is 116.676. A first lens to satisfy Ln/L1a>0.15 from the enlargement side among lenses from the third lens L3 to the lens closest to the reducing side, is the third lens L3.

In other words, as shown in FIG. 7, there are arranged, in order from the enlargement side to the reducing side, first lens group including the first lens L1 through the second lens L2, second lens group Gr2 including just the third lens L3, and third lens group Gr3 including the fourth lens L4 through the twelfth lens L12.

In third group Gr3, positive lenses satisfying 0.662<0.00055×νh+P are five lenses of the sixth lens L6, the seventh lens L7, the eighth lens L8, the tenth lens L10, and the twelfth lens L12.

Table 4 shows values of Hn_min and Hn_min/Y of the sixth lens L6, the seventh lens L7, the eighth lens L8, the tenth lens L10, and the twelfth lens L12 which are positive lenses satisfying 0.662<0.00055×νh+P in third group Gr3 of Example 3.

	TABLE 6
	Hnmin	Hnmin/Y
	Sixth lens	2.56	0.1280
	Seventh lens	3.74	0.1870
	Eighth lens	4.84	0.2420
	Tenth lens	5.68	0.2840
	Twelfth lens	6.56	0.3280

As can be seen from Table 6, four lenses of the sixth lens L6, the seventh lens L7, the eighth lens L8, and the tenth lens L10 satisfy the expression (5): |Hn_min/Y|<0.3.

FIGS. 8 a to 8d are drawings showing spherical aberration and astigmatism of the projection optical system of Example 3. In FIG. 8a, a solid line represents spherical aberration at g-line is, a dashed line represents spherical aberration at i-line, and an alternate long and short dash line represents spherical aberration at h-line. FIG. 8b shows astigmatism at g-line, FIG. 8c shows astigmatism at h-line, and FIG. 8d shows astigmatism at i-line. In the astigmatism diagrams, a solid line represents astigmatism on a meridional image plane, and a dashed line represents astigmatism on a saggital image plane.

FIGS. 9 a and 9b are drawings showing distortion and chromatic aberration of magnification of the projection optical system of Example 3. FIG. 9a shows distortion at h-line. In the diagram showing chromatic aberration of magnification, a solid line represents the chromatic aberration at g-line, and a dashed line represents the chromatic aberration at i-line.

Example 4

Example 4 will be described below.

Table 7 shows surface data of the projection optical system of Example 4.

TABLE 7
i	R	d	Ni	Nh	Ng	νh	P	H
0	Object or
	Image plane
		112.095
1	−793.311							21.15
		6.563	1.636658	1.622941	1.615298	29.2	0.642
2	−165.667							21.21
		26.525
3	151.259							19.34
		8.772	1.666450	1.650811	1.642171	26.8	0.644
4	−306.210							18.72
		23.524
5	−226.630							14.19
		5.463	1.580215	1.572874	1.568579	49.2	0.631
6	−1497.218							13.63
		13.406
7	110.359							11.40
		3.776	1.535939	1.529930	1.526387	55.5	0.629
8	76.205							10.85
		10.543
9	−100.143							9.57
		7.561	1.612806	1.605502	1.601204	52.2	0.630
10	−253.339							9.19
		43.424
11	−543.179							4.85
		7.348	1.559693	1.550656	1.545503	38.8	0.637
12	344.977							4.40
		3.661
13	356.339							4.08
		5.949	1.449860	1.446451	1.444423	82.1	0.627
14	−141.036							3.70
		5.224
15	−87.489							3.15
		5.777	1.619384	1.606803	1.599765	30.9	0.641
16	472.182							2.86
		2.628
17	546.900							2.65
		7.818	1.449860	1.446451	1.444423	82.1	0.627
18	−111.868							2.21
		1.073
19	423.091							2.12
		6.819	1.449860	1.446451	1.444423	82.1	0.627
20	−139.396							1.68
		0.242
21	174.206							1.66
		6.129	1.449860	1.446451	1.444423	82.1	0.627
22	−435.992							1.23
		0.242
23	134.903							1.20
		6.688	1.449860	1.446451	1.444423	82.1	0.627
24	−580.217							0.71
		5.886
25	Stop							0.07
		11.122
26	−331.959							1.13
		2.991	1.580215	1.572874	1.568579	49.2	0.631
27	123.445							1.33
		134.723
28	174.752							17.08
		6.620	1.666450	1.650811	1.642171	26.8	0.644
29	−5362.359							17.25
		63.451
30	−98.453							20.25
		8.509	1.474480	1.469610	1.466690	60.3	0.625
31	117.788							21.51
		14.049
32	−70.216							23.47
		5.269	1.535939	1.529930	1.526387	55.5	0.629
33	−195.345							25.62
		8.521
34	−71.893							27.38
		10.708	1.535939	1.529930	1.526387	55.5	0.629
35	−244.969							32.71
		21.237
36	−191.503							42.69
		13.223	1.666450	1.650811	1.642171	26.8	0.644
37	−104.607							45.74
		0.834
38	3565.595							49.91
		20.872	1.535939	1.529930	1.526387	55.5	0.629
39	−153.927							52.39
		0.242
40	337.037							54.42
		19.260	1.512054	1.507470	1.504754	69.5	0.628
41	−469.965							54.88
		167.827
42	Object or							55.00
	Image plane

FIG. 10 is a cross sectional view showing a structure of the double-telecentric projection optical system of Example 4.

As shown in FIG. 10, the projection optical system of Example 4 has a 20-element structure. In Table 7, lens surfaces numbered 41 and 40 as surface number i represent the first lens L1 arranged at the closest position to the enlargement side. Lens surfaces numbered 2 and 1 as surface number i represent the twentieth lens L20 arranged at the closest position to the reducing side.

In Example 4, the maximum image height Y at the enlargement side is 55.00. A first negative lens to satisfy |Hn/Y|<0.75 from the enlargement side in the projection optical lens is the fourth lens L4. Distance L1a from an apex of the enlargement-side surface of the first lens L1 to the surface of the stop is 341.632. A first lens to satisfy Ln/L1a>0.15 from the enlargement side among lenses from the fourth lens L4 to the lens closest to the reducing side, is the sixth lens L6.

In other words, as shown in FIG. 10, there are arranged, in order from the enlargement side to the reducing side, first lens group including the first lens L1 through the third lens L3, second lens group Gr2 including the fourth lens L4 through the sixth lens L6, and third lens group Gr3 including the seventh lens L7 through the twentieth lens L20.

In third group Gr3, positive lenses satisfying 0.662<0.00055×νh+P are five lenses of the ninth lens L9, the tenth lens L10, the eleventh lens L11, the twelfth lens L12, and the fourteenth lens L14.

Table 8 shows values of Hn_min and Hn_min/Y of the ninth lens L9, the tenth lens L10, the eleventh lens L11, the twelfth lens L12, and the fourteenth lens L14 which are positive lenses satisfying 0.662<0.00055×νh+P in third group Gr3 of Example 4.

	TABLE 8
	Hnmin	Hnmin/Y
	Ninth lens	0.71	0.0129
	Tenth lens	1.23	0.0224
	Eleventh lens	1.68	0.0305
	Twelfth lens	2.21	0.0402
	Fourteenth lens	3.70	0.0673

As can be seen from Table 8, these lenses satisfy the expression (5): |Hn_min/Y|<0.3.

FIGS. 11 a to 11d are drawings showing spherical aberration and astigmatism of the projection optical system of Example 4. In FIG. 11a, a solid line represents spherical aberration at g-line is, a dashed line represents spherical aberration at i-line, and an alternate long and short dash line represents spherical aberration at h-line. FIG. 11b shows astigmatism at g-line, FIG. 11c shows astigmatism at h-line, and FIG. 11d shows astigmatism at i-line. In the astigmatism diagrams, a solid line represents astigmatism on a meridional image plane, and a dashed line represents astigmatism on a saggital image plane.

FIGS. 12 a and 12b are drawings showing distortion and chromatic aberration of magnification of the projection optical system of Example 4. FIG. 6a shows distortion at h-line. In the diagram showing chromatic aberration of magnification, a solid line represents the chromatic aberration at g-line, and a dashed line represents the chromatic aberration at i-line.

Table 9 shows parameters of the projection optical systems and values of expressions (1) to (4), and (6), of Examples 1 to 4.

TABLE 9
Parameter or Expression	Example 1	Example 2	Example 3	Example 4
Magnification	−2.0	−2.0	−3.0	−2.6
NA	0.020	0.033	0.020	0.050
Maximum image height	30.00	40.00	20.00	55.00
at the enlargement side Y
f3	150.55	147.17	63.77	404.31
f2	−43.74	−91.02	−26.52	−47.95
f1	116.10	134.91	64.18	111.75
f12	317.62	293.21	205.21	1634.71
Expression (1) |f12/f3|	2.11	2.05	3.22	4.04
Expression (2) |f1/f12|	0.37	0.46	0.31	0.07
Expression (3) |f2/f12|	0.14	0.31	0.13	0.03
Expression (4) |f2/f1|	0.38	0.67	0.41	0.43
L1a	180.975	212.798	116.676	341.632
TL	315.222	417.023	177.463	556.672
LB	51.490	66.200	64.000	112.095
Expression (6) LB/TL	0.163	0.159	0.361	0.201

Table 9 shows that the projection optical systems of Examples 1 to 4 satisfy all the expressions (1) to (4), and (6).

As can be seen from the above Examples, embodiments of the present invention can provide a double telecentric projection optical lens which maintains image forming property in an excellent condition, and is achromatized for plural wavelength bands within a range from the visible range to near ultraviolet range.

Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention hereinafter defined, they should be construed as being included therein.

Claims

1. A projection optical system with a double telecentricity comprising, in order from a enlargement side: a first lens group with a positive power, including a first lens arranged at a closest position to the enlargement side in the projection optical system;a second lens group with a negative power, including a lens or lenses which start with a negative lens that is a first negative lens to satisfy |Hn/Y|<0.75 from the enlargement side in the projection optical system, and which end with a lens that is the first to satisfy Ln/L1a>0.15 from the enlargement side among the negative lens and lenses at the rear of the negative lens in the projection optical system; anda third lens group with a positive power, including a stop and lenses at the rear of the second lens group, where the lenses in the third lens group include at least two positive lenses satisfying 0.662<0.00055×νh+P,wherein the projection optical system uses a plurality of wavelengths or a wavelength band covering a predetermined range each of which is within a wavelength range from a visible region to a near ultraviolet region, andthe projection optical system satisfies the following expression: 1<|f12/f3|<5,where Hn is a height (mm) of an outermost off-axis principal ray, measured from an optical axis when the outermost off-axis principal ray passes through an enlargement-side surface of an n-th lens,Y is a maximum image height (mm) at the enlargement side,Ln is a distance of an air space between an n-th lens and an (n+1)-th lens,L1a is a distance from an apex of an enlargement-side surface of the first lens to a surface of the stop,νh is defined as (Nh−1)/(Ni−Ng),P is defined as P=(Ni−Nh)/(Ni−Ng),Nh is a refractive index at h-line,Ni is a refractive index at i-line,Ng is a refractive index at g-line,f12 is a composite focal length (mm) of the first lens group and the second lens group, andf3 is a focal length (mm) of the third lens group,where each of the n-th lens for Hn and Ln is an n-th lens to be arranged from the enlargement side in the projection optical system and each n is independently an integer of one or more.

2. The projection optical system of claim 1, wherein the projection optical system satisfies 0.04<|f1/f12|<0.6,where f1 is a focal length of the first lens group.

3. The projection optical system of claim 2, wherein the projection optical system satisfies 0.1<LB/TL<0.5,where LB is a backside length of the projection optical system at a reduction side andTL is a total length of the projection optical system.

4. The projection optical system of claim 2, wherein the projection optical system satisfies 0.01<|f2/f12|<0.5,where f2 is a focal length of the second lens group.

5. The projection optical system of claim 4, wherein the projection optical system satisfies 0.25<|f2/f1|<0.8.

6. The projection optical system of claim 5, wherein each of the at least two positive lenses satisfying 0.662<0.00055×νh+P in the third lens group satisfies the following expression: |Hnmin/Y|<0.3,where Hnmin is smaller one (mm) of a height of an outermost off-axis principal ray measured when the outermost off-axis principal ray passes through an enlargement-side surface of each of the at least two positive lenses and a height of an outermost off-axis principal ray measured when the outermost off-axis principal ray passes a reduction-side surface of each of the at least two positive lenses.

7. The projection optical system of claim 6, wherein the projection optical system satisfies 0.1<LB/TL<0.5,where LB is a backside length of the projection optical system at a reduction side andTL is a total length of the projection optical system.

8. The projection optical system of claim 1, wherein the projection optical system satisfies 0.01<|f2/f12|<0.5,where f2 is a focal length of the second lens group.

9. The projection optical system of claim 8, wherein the projection optical system satisfies 0.25<|f2/f1|<0.8.

10. The projection optical system of claim 1, wherein the projection optical system satisfies 0.25<|f2/f1|<0.8.

11. The projection optical system of claim 10, wherein each of the at least two positive lenses satisfying 0.662<0.00055×νh+P in the third lens group satisfies the following expression: |Hnmin/Y|<0.3,where Hnmin is smaller one (mm) of a height of an outermost off-axis principal ray measured when the outermost off-axis principal ray passes through an enlargement-side surface of each of the at least two positive lenses and a height of an outermost off-axis principal ray measured when the outermost off-axis principal ray passes a reduction-side surface of each of the at least two positive lenses.

12. The projection optical system of claim 1, wherein each of the at least two positive lenses satisfying 0.662<0.00055×νh+P in the third lens group satisfies the following expression: |Hnmin/Y|<0.3,where Hnmin is smaller one (mm) of a height of an outermost off-axis principal ray measured when the outermost off-axis principal ray passes through an enlargement-side surface of each of the at least two positive lenses and a height of an outermost off-axis principal ray measured when the outermost off-axis principal ray passes a reduction-side surface of each of the at least two positive lenses.

13. The projection optical system of claim 1, wherein the third lens group includes at least three positive lenses and at least two negative lenses.

14. The projection optical system of claim 13, wherein the first lens arranged at the closest position to the enlargement side in the first lens group, is a biconvex positive lens.

15. The projection optical system of claim 14, wherein the first lens group includes at least two positive lenses.

16. The projection optical system of claim 15, wherein the first lens group includes a positive lens, a negative lens, and a positive lens, in order from the enlargement side.

17. The projection optical system of claim 1, wherein the first lens arranged at the closest position to the enlargement side in the first lens group, is a biconvex positive lens.

18. The projection optical system of claim 1, wherein the first lens group includes at least two positive lenses.

19. The projection optical system of claim 18, wherein the first lens group includes a positive lens, a negative lens, and a positive lens, in order from the enlargement side.

20. The projection optical system of claim 1, wherein the projection optical system satisfies 0.1<LB/TL<0.5,where LB is a backside length of the projection optical system at a reduction side andTL is a total length of the projection optical system.