Patent Grant
6933494
This invention relates to optical sensor heads and, more particularly, to an optical sensor heads for radiating light beams to moving objects and the optical sensor system using the same.
A typical example of the optical sensor system is disclosed in Japan Patent Application laid-open No. 9-152871. Japan Patent Application No. hei 7-313185 was laid open as the Japan Patent Application laid-open No. 9-152871. A U.S. Patent Application was filed claiming the Priority Right on the basis of the Japan Patent Application, and U.S. Pat. No. 5,804,816 was assigned to the U.S. Patent Application.
The prior art optical sensor system is used in a keyboard musical instrument for monitoring the keys. The prior art optical sensor system includes shutter plates respectively attached to the keys, light radiating optical sensor heads and light receiving optical sensor heads. The light radiating optical sensor heads are alternated with the light receiving optical sensor heads, and light beams are radiated from both side surfaces of each light radiating sensor head to the light receiving optical sensor heads disposed on both sides thereof. The light beams across the trajectories of the shutter plates. While a player is depressing the key, the shutter plate is moved along the trajectory, and gradually interrupts the light beam. The shutter motion results in reduction of the amount of light incident on the light receiving optical sensor, and a controller determines the present key position on the basis of the amount of incident light.
The light radiating optical head 120 is made of transparent synthetic resin such as acrylic resin, and broken down into a body portion 120a and a light output portion 120b. The body portion 120a has a generally rectangular parallelepiped shape, and is formed with a guide groove 120c. The optical fiber 140 is inserted into the guide groove 120c. The optical fiber 140 is made of transparent synthetic resin such as acrylic resin, and is of the order of 0.5 millimeter thick. The optical fiber 140 has a light output end 122, and the light output end 122 is held in contact with an inner surface partially defining the groove 120c. The guide groove 120c has a centerline, which is coincident with the center axis of the optical fiber 140, and the light is radiated from the light output end 122 toward the light output portion 120b.
The light output portion 120b projects from the body portion 120a, and is formed with convex lenses 121L/121R. The convex lenses 121L/121R are symmetrical with respect to the extension of the centerline of the groove 120c, and have reflection surfaces 123b/123c. The reflection surfaces 123b/123c are diverged from an edge line 123a, and the optical axes of the convex lenses 121L/121R and the center axis of the optical fiber 140 intersect the edge line 123a. The light proceeds to the reflection surfaces 123b/123c, and is split into two light beams R at the edge line 123a. The reflection surfaces 123b and 123c are spaced from the extension line of the center axis of the optical fiber 140 by 45 degrees so that the two light beams R are respectively directed toward the convex lenses 121L/121R through the reflection on the surfaces 123c/123b.
The light receiving optical sensor head 130 is also made of the transparent synthetic resin, i.e., acrylic resin, and is also broken down into a body portion 130a and a light input portion 130b. The body portion 130a and light input portion 130b are corresponding to the body portion 120a and light output portion 120b, respectively. The optical fiber 150 is made of acrylic resin, and is of the order of 0.5 millimeter. The optical fiber 150 is held in contact at an ling input end 132 with an inner surface of the body portion 130a, and is connected at the other end to a light detecting device (not shown). The light input portion 130b has convex lenses 131L/131R, and the reflection surface 133b intersects the other reflection surface 133c at an edge line 133a.
The convex lens 121R is virtually split into two halves 121Ra and 121Rb with respect to a virtual plane defined by the edge line 123a and optical axis of the convex lens 121R. The arrangement of the convex lenses 131L, 131R, reflection surfaces 133c/133b and optical fiber 150 is same as that of the convex lenses 121L, 121R, reflection surfaces 123c/123b and optical fiber 140. For this reason, the convex lens 131L is virtually split into halves 131La and 131Lb without respect to the virtual plane defined by the optical axis of the convex lens 131L and the edge line 133a.
The light radiating optical sensor heads 120 and light receiving optical sensor heads 130 are produced through a molding process. Molding die units are prepared for the light radiating optical sensor heads 120 and light receiving optical sensor heads 130, respectively, and acrylic resin is injected into the molding die units for forming the acrylic resin into the light radiating sensor heads 120 and light receiving sensor heads 130.
The light proceeds as follows. The light is output from the light output end 122 of the optical fiber 140, and proceeds to the reflection surfaces 123b/123c. The light is split into two light beams at the edge line 123a, and the two light beams are incident on the reflection surfaces 123b/123c. The light beams change their directions at 90 degrees through the reflection on the surfaces 123b/123c, and proceed to the convex lenses 121R/121L, respectively.
The light beams similarly behave so that description is focused on the rightward proceeding light beam R. The light beam R passes through the half 121Ra of the convex lens 121R, and the convex lens 121 makes the rays of the light beam R parallel to one another. The light beam R rightward proceeds toward the light receiving optical sensor head 130, and is incident on the haft 131La of the convex lens 131L.
The light beam R proceeds toward the reflection surface 133c through the light input portion 130b, and is reflected on the surface 133c. The rays of the reflected light beam are concentrated on the light input end 132 of the optical fiber 150. The light is propagated through the optical fiber 150 to the light detecting device, and is converted to photo-current.
If any obstacle is not on the optical path of the light beam R, the amount of incident light is maximized. However, when the shutter plate enters the optical path, the amount of incident light is reduced depending upon the position of the shutter plate. Thus, the present shutter position has the influence on the amount of photo-current.
As described hereinbefore, the light radiating optical sensor heads 120 and light receiving optical sensor heads 130 are formed through the molding process. The light radiating optical sensor heads 120 are geometrically identical with one another, and the light receiving optical sensor heads 130 are also geometrically identical with one another. If the light receiving optical sensor heads 130 are exactly disposed at the target positions on both sides of each light radiating optical sensor head 120, the amount of incident light at each light receiving optical sensor head 130 is to be equalized to the amount of incident light at another light receiving optical sensor head 130. In other words, the optical sensor system is to be installed without any calibration. However, the amount of incident light is dispersed among the light receiving optical sensor heads 130. The manufacturer individually measures the amount of photo-current for the light receiving optical sensor heads 130, and calibrates the light detecting devices. Thus, a problem is encountered in the prior art optical sensor heads 120/130 in the poor uniformity in the optical characteristics.
Another document is U.S. Pat. No. 5,804,816. The prior art optical sensor head is split into two parts, and one of the parts is formed with a pair of prisms. Although the prisms have respective reflection surfaces, U.S. Pat. No. 5,804,816 is silent to the shape of the edge between the reflection surfaces.
It is therefore an important object of the present invention to provide an optical sensor head, which exhibits good uniformity in optical characteristics.
It is also an important object of the present invention to provide an optical sensor system, which is installed without complicated calibration work.
The present inventors contemplated the problems inherent in the prior art optical sensor heads, and found the reflecting surfaces 123b/123c not to form a sharp edge line 123a. The dull edge line 123a caused the light to be irregularly reflected as indicated by broken lines R1/R2 in
Since the edge line 133a was also differently shaped, part of the incident light might be reflected on the edge line 133a to the light input end 132. The shape at the edge line 123a was different among the light radiating optical sensor heads 120, and, accordingly, the amount of irregular reflection was not presumable. Similarly, the edge line 133a was unintentionally shaped, and the amount of light undesirably incident on the light input end 132 was not controllable.
The irregular shapes of the edge lines 123a/133a were unavoidable in so far as the optical sensor heads 120/130 were produced through the molding process. The present inventors concluded that the optical sensor heads required a means for suppressing the irregularly reflected light.
In accordance with one aspect of the present invention, there is provided an optical sensor head comprising a body portion having an optical path for light, and a head portion connected to the body portion, formed with reflection surfaces extending from an edge on the optical path in different directions for splitting the light into plural beams through reflection thereon and having a stray light reducing member for reducing the amount of stray light unavoidably produced at the edge.
In accordance with another aspect of the present invention, there is provided an optical sensor head comprising a body portion having an optical path for light, and a head portion connected to the body portion, formed with reflection surfaces extending from an edge on the optical path in different directions for splitting the light into plural beams through reflection thereon and having a stray light controller for making the amount of stray light at the edge predictable.
In accordance with yet another aspect of the present invention, there is provided an optical sensor system for converting present positions of moving objects to electric signals comprising a light emitting unit for emitting light, at least one light radiating optical sensor head connected through an optical fiber to the light emitting unit and including a body portion offering an optical path to the light and a head portion connected to the body portion, formed with reflection surfaces extending from an edge on the optical path in different directions for splitting the light into light beams through reflection thereon and having a suppressing member for reducing fluctuation of the amount of the light beams, at least two light receiving optical sensor heads sideward spaced from the at least one light radiating optical sensor head for permitting the moving objects to pass through gaps, and respectively receiving the light beams, and a light detecting unit connected through optical fibers to the at least two light receiving optical sensor heads, respectively, and converting the light beams to the electric signals.
The features and advantages of the optical sensor heads and optical sensor system will be more clearly understood from the following description taken in conjunction with the accompanying drawings, in which
First Embodiment
Referring to
The shutter plates 1b are respectively secured to moving objects such as, for example, keys 1a incorporated in a keyboard musical instrument. The keyboard musical instrument is of a composite musical instrument between an acoustic piano and an electronic piano. The composite keyboard musical instrument is named “silent piano”. The silent piano largely comprises an acoustic piano, i.e., either grand or upright piano, a hammer stopper and an electronic tone generating system. The silent piano has at least an acoustic mode and a silent mode.
While the hammer stopper is staying at a free position, the hammer stopper keeps itself out of the trajectories of the hammers, and permits a pianist to play a music passage through the acoustic piano tones. The pianist is assumed to change the hammer stopper to the blocking position. The hammer stopper enters the trajectories of the hammers. While the pianist is fingering on the keyboard, the depressed keys actuate the associated action units, and the actuated action units make the associated hammers driven for rotation as usual. However, the hammers rebound on the hammer stopper before striking the strings. Thus, any acoustic tone is never generated. Instead, the electronic tone generating system generates electronic tones.
In detail, the optical sensor system 1 is provided for the keyboard. The shutter plates 1b are secured to the lower ends of the keys 1a. A standard acoustic piano has eighty-eight keys 1a, and, accordingly, eighty-eight shutter plates 1b downward project from the associated keys 1a. An array of light radiating optical sensor heads 20 and light receiving optical sensor heads 30 is provided under the array of keys 1a. The total number of optical sensor heads 20/30 is eighty-eight plus one. The light radiating optical sensor heads 20 are alternated with the light receiving optical sensor heads 30. Each of the light radiating optical sensor heads 20 sideward radiates two light beams toward the adjacent light receiving optical sensor heads 30, and the light receiving optical sensor heads 30 receives the light beams from the adjacent light radiating optical sensor heads 20. Plural time slots are selectively assigned to the light radiating optical sensor heads 20 in such a manner that any light receiving optical sensor head 30 does not concurrently receives two light beams from the adjacent light radiating optical sensor heads 20. Each light beam laterally extends across the trajectory of associated one of the shutter plates.
When the pianist depresses one of the keys 1a, the depressed key 1a is downwardly moved together with shutter plate 1b, and the light beam is gradually interrupted with the shutter plate 1b. The overlapped area between the light beam and the shutter plate 1b is increased, and the amount of light incident on the associated light receiving optical sensor head 30 is gradually decreased. The variation of incident light is reported from the optical sensor system 1 to a controller 1c, which is incorporated in the electronic tone generating system. The controller 1c specifies the depressed key, and calculates the velocity. The controller 1c produces a music data code representative of the depressed key 1a, and a tone generator 1d, which also forms a part of the electronic tone generating system, produces a digital tone signal on the basis of the music data code. The digital tone signal is converted to an analog audio signal, which in turn is converted to an electronic tone through a sound system 1e. Thus, the silent piano generates the electronic tones instead of the acoustic piano tones.
The components 2, 3, 10, 19, 20 and 30 are hereinafter described in more detail. The optical fibers 2 are made of transparent synthetic resin such as, for example, acrylic resin, and are 0.5 millimeter thick. The optical fibers 2 form bundles FB1, and the bundles FB1 of optical fibers 2 are respectively connected to light output ports A, B, C, D, E, F, G, H, I, J, K and L of the light emitting unit 11. The optical fibers 2 are separated from each other at the other end portions, and are connected to the light radiating optical sensor heads 2, respectively. The light output ports A to L are respectively assigned the time slots, and the light emitting unit 10 sequentially radiates the light from the light output ports A to L into the bundles FB1 of optical fibers 2. The light is incident onto the bundles BF1 of optical fibers 2. The light is propagated through the individual optical fibers 2, and reaches the light emitting optical sensor heads 20. Thus, the optical fibers 2 offer the optical paths for the outward journey to the light.
The optical fibers 3 are also made of transparent synthetic resin such as, for example, acrylic resin, and are 0.5 millimeter thick. The optical fibers 3 are respectively connected to the light receiving optical sensor heads 30, and form plural bundles FB2. Each of the bundles FB2 consists of the optical fibers 3, which respectively receive the incident light from the associated light receiving optical sensor heads 30 at different time slots. In other words, each bundle FB2 does not include two optical fibers 3 concurrently propagating the incident line to the light detecting unit 19. The bundles FB2 of optical fibers 3 are connected to the light detecting unit 19. Thus, the optical fibers 3 offer optical paths for the homeward journey to the light.
The light emitting unit 10 includes an optical coupler 11/12 and plural light emitting devices 13 such as, for example, light emitting diodes. The light emitting devices 13 are respectively associated with the light output ports A to L, and the controller sequentially energizes the light emitting devices 13 so as to distribute the light to the light output ports A to L in the respective time slots. The optical coupler is broken down into an optical plug 11 and a device holder 12. The light emitting devices 13 are secured to the device holder 12. The optical plug 11 is formed with the light output ports A to L, and the bundles FB1 of optical fibers 2 are snugly received in the light output ports A to L, respectively. The optical plug 11 is assembled with the device holder 12. Then, the light emitting devices 13 are respectively opposed to the bundles FB1 of optical fibers 2.
The light detecting unit 19 includes plural light detecting devices 19a such as, for example, photo-transistors. The light detecting devices 19a are respectively assigned to the bundles FB2 of optical fibers 3, and convert the light to electric charge. The amount of electric charge is proportional to the amount of incident light so that the shutter position is represented by the potential level of the electric signal supplied from the light detecting unit 19 to the controller 1c. The optical fibers 3 of each bundle FB2 radiate the light to the associated light detecting device 19a in the different time slots. For this reason, the controller 19 is able to determine what key 1a is moved on the basis of the combination of the light emitting device 13 and light detecting device 19a. The control method for the light emitting unit 10 and light detecting unit 19 is disclosed in Japan Patent Application laid-open No. hei 9-152871.
The light radiating optical sensor heads 20 are made of transparent synthetic resin such as, for example, acrylic resin, and are shaped through a molding process. For this reason, the light radiating optical sensor heads 20 are identical with one another. Description is made on one of the light radiating optical sensor heads 20 with reference to
Although the light radiating optical sensor head 20 is monolithic, the light radiating optical sensor head 20 is imaginarily broken down into a light output head portion 20a and a body portion 20b. The light radiating optical sensor head 20 is symmetrical with respect to a plane 20c of symmetry.
The light output head portion 20a is formed with a pair of prisms 23 and convex lenses 21L/21R. The pair of prisms 23 are held in contact with one another at an edge line 23a, and have respective reflection surfaces 23b/23c. The reflection surfaces 23b/23c are merged with each other at the edge line 23a, and gradually spaced from each other along the plane of symmetry 20c. In other words, the distance between the plane of symmetry 20c and the reflection surfaces 23b/23c is increased. The reflecting surfaces 23b/23c are inclined at 45 degrees with respect to the plane of symmetry 20c. In other words, the reflection surfaces 23b and 23c are spaced from each other by 90 degrees.
The convex lenses 21R and 21L sideward project from the prisms 23, respectively. Each of the convex lenses 21R/21L is imaginarily split into two halves 21Ra/21Rb or 21La/21Lb with respect to a plane of symmetry 21s. The plane 21s of symmetry intersects the plane 20c of symmetry at the edge line 23a. The half 21Ra of the convex lens 21R and the half 21La of the other convex lens 21L are mirror finished. However, the other halves 31Rb and 21Lb are roughened like textured surfaces. The textured surfaces 21Rb/21Lb cause the light scattered through the irregular reflection/refraction. For this reason, the amount of light passing through the halves 21Rb/21Ib is drastically reduced.
The body portion 20b is formed with pits 20d and 20e, and the pits 20d/20e are open on the reverse surface 20f of the body portion 20b. The pit 20d is connected to the other pit 20e through a guide hole 20h. The guide hole 20h has a centerline, which extends on the plane 20c of symmetry, and the guide hole 20h is approximately equal in diameter to the optical fiber 2. A mouth 22 projects into the pit 20e, and a concave is defined in the mouth 22. The concave is converged from the entrance to the bottom. Although the entrance is larger in diameter than the optical fiber 2, the bottom is approximately equal in diameter to the optical fiber 2. The concave has a centerline substantially coincident with the centerline of the guide hole 20h.
The optical fiber 2 is connected to the light radiating optical sensor head 20 as follows. An assembling worker roughly aligns the optical fiber 2 with the guide hole 20h, and inserts the optical fiber 2 through the pit 20d into the guide hole 20h. The assembling worker further pushes the optical fiber 2 into the guide hole 20h. Then, the leading end of the optical fiber 2 reaches the mouth 22. The assembling worker further pushes the optical fiber 2. Then, the mouth 22 is resiliently deformed, and is pinched in the mouth 22. The leading end of the optical fiber 2 is brought into contact with the bottom surface of the mouth 22, and the resiliently deformed mouth 22 keeps the optical fiber 2 held in contact with the bottom surface. For this reason, the light enters the body portion, and proceeds to the light output head portion 20a along the plane 20c of symmetry.
Turning back to
The light receiving optical sensor head 30 is also symmetrical with respect to a plane 30c, and is imaginarily broken down into a light input head portion 30a and a body portion 30b. A pair of prisms 33 and convex lenses 31L/31R are formed in the light input head portion 30a. The pair of prisms 33 are held in contact with one another at an edge line 33a, and have respective reflection surfaces 33b/33c. The reflection surfaces 33b/33c are merged with each other at the edge line 33a, and gradually spaced from each other along the plane of symmetry 30c. In other words, the distance between the plane of symmetry 30c and the reflection surfaces 33b/33c is increased. The reflecting surfaces 33b/33c are inclined at 45 degrees with respect to the plane of symmetry 30c. In other words, the reflection surfaces 33b and 33c are spaced from each other by 90 degrees.
The convex lenses 31R and 31L sideward project from the prisms 33, respectively. Each of the convex lenses 31R/31L is imaginarily split into two halves 31Ra/31Rb or 31La/31Lb with respect to a plane of symmetry, which intersects the plane 30c of symmetry at the edge line 33a. In this instance, the halves 31Lb/31Rb are also roughened like the textured surfaces 21Rb/21Lb. The textured surfaces 31Lb/31Rb make the incident light irregularly reflected on and refracted therein so that the amount of light incident is drastically reduced.
The textured surfaces 21Lb/21Rb and 31Rb/32Lb are transferred from the molding die unit to the convex lenses 21L/21R and 31R/31L in the molding process. The molding die units have curved inner surfaces corresponding to the convex lenses 21L/21R and convex lenses 31R/31L. The curved surfaces are partially mirror finished and partially textured. When the synthetic resin is solidified in the molding die units, the texture pattern is transferred to the halves 21Rb/21Lb of the light radiating optical sensor heads 20 and the halves 31Rb/31Lb of the light receiving optical sensor heads 30. Thus, the manufacturer easily roughens the halves of the convex lenses 21R/21L and 31R/31L.
The body portion 30b is formed with pits, and the pits are open on the reverse surface of the body portion 30b. The pits are connected to each other through a guide hole as similar to the pits 20d and 20e. The guide hole has a centerline, which extends on the plane 30c of symmetry, and the guide hole is approximately equal in diameter to the optical fiber 3. A mouth 32 projects into the pit, and a concave is defined in the mouth 32. The concave is converged from the entrance to the bottom. Although the entrance is larger in diameter than the optical fiber 3, the bottom is approximately equal in diameter to the optical fiber 3. The concave has a centerline substantially coincident with the centerline of the guide hole. Thus, the light receiving optical sensor heads 30 are identical in shape with the light radiating optical sensor heads 20.
The optical sensor system 1 behaves as follows. When the optical sensor system 1 is energized, the controller 1c starts to sequentially supply a key scan pulse signal to the associated light emitting devices 13 in the time slots, and repeats the distribution of the key scan pulse signal. The controller 1c further starts to convert the potential level of the electric signals respectively output from the light detecting devices 19a to digital codes, and checks the digital codes to see whether or not a pianist depresses or releases any one of the keys 1a.
The key scan pulse signal causes the light emitting devices 13 to emit the light toward the light output ports A to L, and the light enters the bundles FB1 of optical fibers 2. The light output port L is assumed to be connected through the optical fiber 2 to the light radiating optical sensor head 20 disposed at the second position from the left in FIG. 2. When the rightmost light emitting device 13 is energized with the key scan pulse signal, the light enters the optical fibers connected to the light output port L, and are propagated through the optical fibers 2 to the light radiating optical sensor heads 20. The light reaches the light radiating optical sensor head 20 at the second position, and the light enters the body portion 20b of the light radiating optical sensor head 20. The light proceeds to the pair of prisms 23 and is split into two light beams respectively incident on the reflection surfaces 23b/23c. The light beams are reflected on the reflection surfaces 23b/23c, respectively, and are directed to the convex lenses 21R and 21L, respectively.
The light beams are radiated from the halves 21Ra/21La of the convex lenses 21R/21L, and the convex lenses 21R/21L make the rays of the light beams parallel. The light beams proceed to the adjacent light receiving optical sensor heads 30 on both sides of the light radiating optical sensor head 20, and are incident onto the light input head portions 30a of the light receiving optical sensor heads 30, respectively. The convex lenses 31L/31R concentrate the light beams on the optical fibers 3, and the incident light enters the optical fibers 3. The incident light is propagated through the optical fibers 3 to the associated light detecting devices 19a, and the light detecting devices 19a convert the incident light to the electric signals. The electric signals are supplied from the light detecting unit 19 to the controller 1c.
Although the reflection surfaces 23b and 23c are designed sharply to cross each other at the edge 23a, the edge 23a is unavoidably rounded in the molding, and the shape around the edge 23a is uncontrollable. In other words, it is rare to find the rounded edges 23a strictly identical with each other. The light is scattered at the rounded edge 23a as indicated by arrows AR1 (see FIG. 4A), and the scattered light, i.e., stray light partially reaches the half 21Rb of the convex lens 21R. The amount of the stray light is different between the light radiating optical sensor heads 20. Although most of the incident light was directed to the half 131Lb of the convex lens 131L in the prior art light radiating optical sensor head 130, the light radiating optical sensor head 20 reduces the amount of stray light directed to the half 31Lb of the convex lens 31 by virtue of the textured surface 21Rb. In detail, the light incident on the half 21Rb is irregularly reflected on and refracted in the textured surface 31Rb as indicated by arrows AR2, and only part of the incident light D is directed to the half 31Lb of the convex lens 31L. The amount of light D is much less than the amount of light directed to the half 31La of the convex lens 31L, and the amount of light less fluctuates at the light detecting devices 19a.
The light D reaches the half 31Lb of the convex lens 31L as similar to the light G (see FIG. 4B). The light D/G is irregularly reflected on and refracted in the half 31Lb/31Rb of the convex lens 31L/31R, and only small part E of the incident light is directed to the edge 33a. The edge 33a is unavoidably rounded in the molding process, and the shape of the edge 33a is uncontrollable. Nevertheless, the amount of light E is extremely small part of the incident light G. The incident light G/D is extremely small part of the light incident on the half 21Rb of the convex lens 21R, and the amount of the light E is extremely small part of the light G. Thus, even though part of the light E is reflected on the rounded edge 33a toward the optical fiber 3, the amount of light incident onto the optical fiber 3 is negligible. For this reason, the optical sensor system according to the present invention does not require the calibration for the electric signals representative of the present positions of the shutter plates 1a.
As will be understood from the foregoing description, even though the stray light is unavoidable in the light radiating optical sensor heads 20, the light radiating optical sensor heads 20 make the amount of light D/G reduced through the irregular reflection on and irregular refraction in the textured surfaces 20Lb/20Rb of the convex lenses 21L/21R. Moreover, the light receiving optical sensor heads 30 further reduces the amount of light E through the irregular reflection on and irregular refraction in the textured surfaces 31Lb/31RB of the convex lenses 31L/31R. Although an extremely small part of the stray light is incident onto the light input ends 32 of the optical fibers 3, the fluctuation of the incident light is ignoreable between every two optical fibers 3, and the calibration is not required for the optical sensor system according to the present invention.
Second Embodiment
A difference between the light radiating optical sensor heads 20A and the light radiating optical sensor heads 20 is a photo-shield member 41. In detail, the light radiating optical sensor head 20A has convex lenses 21L/21R as similar to the light radiating optical sensor head 20, and the convex lenses 21L/21R have at least mirror finished halves 21La/21Ra. The other halves are covered with the photo-shield member 41. The photo-shield member 41 is made of photo-shield material, and is secured to the light output head portion 20a. In this instance, the photo-shield member 41 is formed from a sheet of metal.
The photo-shield member 41 does not permit the halves 21Lb/21Rb to radiate the stray light toward the light receiving optical sensor heads. In case where the photo-shield members 41 are provided for the light receiving optical sensor heads, the photo-shield members 41 perfectly prevent the light receiving optical sensor heads from the stray light and environmental light incident onto the halves 31Rb/31Lb.
Thus, the photo-shield members 41 perfectly prevent the light receiving optical sensor heads from the stray light so that the manufacturer can install the optical sensor system in the keyboard musical instrument without strict calibration.
Third Embodiment
Turning to
A difference between the light radiating optical sensor head 20U and the light radiating optical sensor head 20 is a notch formed at the edge 23a. The notch 24 penetrates into the pair of prisms 23U over the planes SP of symmetry, which virtually divide the convex lenses 21L/21R into halves 21La/21Ra and other halves 21KbU/21RbU. The notch 24 has a U-letter shaped cross section. A small projection, which is corresponding to the notch 24, may be formed in a molding die unit (not shown) so as to form the notch 24 in the molding process. In this instance, the halves 21RbU/21LbU are roughened like the textured surface. However, the halves 21RbU/21LbU may be mirror finished in another instance.
It is possible to well control the shape of the notch 24 through the molding process. A molding die unit is formed with a groove, and a projection, which is corresponding to the notch 24, is inserted into the groove. The groove and, accordingly, the projection are located at the boundary between the inner surfaces corresponding to the reflection surfaces of the prisms 23U, and the projection is well finished. The notch 24 is fairly wide and deep so that the manufacturer can form the projection at target geometry. The well finished surface configuration of the projection is transferred from the molding die unit to the optical sensor heads 20U. Although the light is reflected on the round surfaces, the amount of reflection incident on the halves 21LbU/21RbU is constant among the light radiating optical sensor heads 20U. Even though part of the reflection is incident onto the light input end 32, the amount of incident light less fluctuates so that the strict calibration is not required for the optical sensor system.
The notch may have a cross section different from the U-letter shape.
As will be understood, although the notches 24/25/26 do not reduce the stray light incident onto the light input ends 32 of the light receiving optical sensor heads, the notches 24/25/26 are effective against the fluctuation in the amount of incident light, because the shapes of notches 24/25/26 are well controlled through the molding process. The approach employed in the third embodiment and modifications thereof is different from the approach employed in the first and second embodiment. Nevertheless, the concept of the first and second embodiments and the concept of the third embodiment and modifications thereof are fallen within a superordinate concept that the fluctuation in the amount of light incident onto the optical fibers 3 is to be suppressed.
Fourth Embodiment
Turning to
One of the parts 40a/40b includes a prism 43a and a convex lens 43b, which are respectively corresponding to one of the prisms 23 and convex lens 21R. The prism 43a has a reflection surface 43c, and the reflection surface 43c crosses a split surface 43d of the part 40a at an edge 43e. The reflection surface 43c inclines at 45 degrees from an extension of the split surface 43d, and the edge 43e is sharp. The split surface 43d has a predetermined length. The convex lens 43b is symmetrical with a plane 43f of symmetry, and is virtually split into halves 43h and 43j. The half 43h is mirror finished, and the other half 43j is roughened like the textured surface. However, both halves 43h/43j may be mirror finished.
On the other hand, the other part 40b includes a prism 42a, a body portion 42b and a convex lens 42c. The body portion 42b is similar to the body portion 20b, and is symmetrical with respect to a plane 40c of symmetry. The part 40b has a split surface 42d, which is coplanar with the plane 40c of symmetry, and the split surface 42d has the predetermined length. The prism 42a has a reflection surface 42e, and the reflection surface 42e crosses the split surface 42d at an edge 42aa. The edge 42aa is sharp. The reflection surface 42e inclines at 45 degrees with respect to the plane 40c of symmetry. The lens 42c is symmetrical with a plane 42f of symmetry, and is virtually split into halves 42h and 42j. The half 42h is mirror finished, and the other half is roughened like the textured surface. However, both halves 42h and 42j may be mirror finished. Both of the parts 40a and 40b are produced through the molding process.
The parts 40a/40b are assembled into the light radiating optical sensor head 40 as follows. First, adhesive compound is spread over the split surfaces 42d/43d. The split surface 42d is faced to the split surface 43d, and is pressed to the split surface 43d. Then, the edge 43e is brought into coincident with the edge 42aa as shown in
As will be understood from the foregoing description, the light radiating optical sensor head 40 has the edge 43e/42aa formed at the crossing line between the reflection surfaces 42e/43c by separating it into plural parts. The light radiating optical sensor head 40 is based on a concept that the stray light is to be reduced by making the edge 43e/42aa sharp. Although the concept employed in the fourth embodiment is different from the concept employed in the first and second embodiments and the concept employed in the third embodiment, the light radiating optical sensor head 40 is also fallen within the superordinary concept that the fluctuation in the amount of light incident onto the optical fibers 3 is to be suppressed.
Although particular embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention.
For example, the keyboard musical instrument does not set any limit on the scope of the present invention. The optical sensor system may be incorporated in another sort of keyboard musical instrument such as, for example, an automatic player piano, another sort of musical instrument such as, for example, electronic stringed instrument and electronic wind instrument and another sort of electronic good such as, for example, industrial machinery.
In the first embodiment, both light radiating and light receiving optical sensor heads have the textured surfaces 21Lb/21Rb and 31Lb/31Rb. However, either light radiating optical sensor heads 30 or light receiving optical sensor heads may have the textured surfaces 21Lb/21Rb or 31Lb/31Rb in so far as the fluctuation is admittable in an application of the optical sensor system.
The textured surfaces are a mere example of the roughened surfaces. Any sort of roughened surfaces is available for the optical sensor heads 20/30 in so far as the amount of stray light is reduced through the irregular reflection and/or irregular refraction.
In the second embodiment, the light receiving optical sensor heads 30 may have the halves 31Lb/31Rb roughened as similar to those of the first embodiment. Otherwise, the light receiving optical sensor heads 30 may have the photo-shield members 41 instead of the roughened halves 31Lb/31Rb.
A photo-shield layer may be adhered to, coated on or deposited on the halves 21Lb/21Rb. For example, black paint may be spread on the halves 21Rb/21Lb.
The photo-shield member or layer may be semi-transparent. Even though part of the stray light passes through the semi-transparent member or layer, the manufacturer can install the optical sensor system in an application without strict calibration in so far as the fluctuation is acceptable.
In the modifications shown in
The cross sections of the notches 24/25/26 do not set any limit to the technical scope of the present invention. The light radiating optical sensor heads 20U/20K/20V may have the roughened halves of the convex lenses. Otherwise, the photo-shield members 41 may be provided for the light radiating optical sensor heads 20U/20K/20V.
In the fourth embodiment, the light radiating optical sensor head 40 is split into the two parts 40a/40b. However, the light radiating optical sensor head 40 may be split into more than two parts. For example, the light radiating optical sensor head 40 may be split into three portions 42a/42c, 42b and 40a.
The transparent optical fibers 2/3 do not set any limit to the technical scope of the present invention. If the light emitting unit 10 emits infrared light and, accordingly, the light detecting unit 19 converts the infrared light to electric charge, the optical fibers 2 and 3 are colored.
The photo-shield member 41 may be implemented by a non-transparent cover plate 41f shown in FIG. 10.
Claim languages are correlated with the system components and parts as follows. The body portion 20b and 42b and the head portions 20a and 30a/ the combination of prisms and convex lenses 42a, 43a, 42c and 43b serve as a body portion and a head portion, respectively, and the textured surfaces 21Lb/21Rb/31Lb/31Rb, the photo-shield member 41 and the sharp edge 43e/42aa are corresponding to a stray light reducing member. The body portion and the head portion shown in
The entire disclosure of Priority Document. 2002-123744 is incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2002-123744 | Apr 2002 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5783818 | Manabe et al. | Jul 1998 | A |
| 5804816 | Yamamoto et al. | Sep 1998 | A |
| 5909028 | Yamamoto | Jun 1999 | A |
| Number | Date | Country | |
|---|---|---|---|
| 20030201386 A1 | Oct 2003 | US |
