JP2011237270A - Optical sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve miniaturization and cost reduction of an optical sensor by reducing the number of chemical components and simplifying a structure.SOLUTION: An optical sensor 1 for detecting vibration comprises: a light source 2; a polarization beam splitter 3; an objective lens 4; a wavelength plate unit 5; and one light receiving element 6. The miniaturization of the optical sensor, simplification of structure and assembly, and cost reduction are achieved by integrating a 1/4 wavelength plate 7 with a vibration plate 8 in the wavelength plate unit. The light receiving element 6 is arranged by making an optical axis x2 to be parallel to and slightly deviated from an optical axis x1 of reflection light of the vibration plate. According to such an arrangement, a beam spot shape made incident on the light receiving element is projected to a position obtained by making the center c to be slightly deviated and separated from the center O of the light receiving surface 6a. An amount of light detected from the light receiving element is increased or decreased depending on the displacement of the vibration plate.

Description

  The present invention relates to an optical sensor for detecting, for example, fluid pressure and sound pressure, displacement of a measurement surface, vibration, and the like.

  Conventionally, in an optical pickup for reproducing or recording information from an optical disk such as a CD, a knife edge method, an astigmatism method, a critical angle method, Optical methods such as Foucault method are adopted. Various methods and apparatuses for measuring the position, displacement, and surface roughness of a measurement object using these techniques have been proposed.

  For example, in order to measure a minute displacement or surface roughness of an object using the knife edge method, a laser beam is projected onto a measurement object so as to be focused on the surface, and the reflected light is received by a two-divided diode. A measuring instrument is known (see, for example, Patent Document 1). In this optical system, a knife edge is arranged in the middle of the optical path, and the cross section of the reflected beam incident on the two-divided diode becomes a semicircle. When the surface of the object to be measured is shifted backward from the focal position, the reflected beam is shifted downward from the two-divided diode, and when it is shifted forward, it is shifted upward. The displacement amount of the object surface can be obtained.

  Also, an optical displacement sensor that measures the surface shape and surface roughness of the measurement surface using the astigmatism method projects the laser beam as a minute spot onto the measurement surface, and passes the reflected light through a cylindrical lens. A point aberration is given, and the center of the beam spot is made incident on the center of the four-divided light receiving element (see, for example, Patent Documents 2 and 3). When the measurement surface is at the focal position of the laser beam, the output signal of each light receiving element is equal, but when the measurement surface is shifted backward or forward, the output signal of the light receiving element at one diagonal position is the other diagonal. It becomes larger than the output signal of the light receiving element at the position. Therefore, by calculating the displacement signal of the measurement surface from the output signal of each light receiving element, the displacement amount from the focal position of the measurement surface can be obtained.

Japanese Patent Laid-Open No. 7-4914 JP-A-5-231848 JP-A-8-29664

  However, each of the above-described conventional optical sensors has a problem that the number of optical components is large, the size is large, and the structure is complicated and expensive.

  Accordingly, the present invention has been made in view of the above-described conventional problems, and an object thereof is to reduce the number of optical components, simplify the structure, and realize light that can be downsized and reduced in cost. To provide a sensor.

  In order to achieve the above object, the optical sensor of the present invention includes a light source, a photodetector, and a first optical system that condenses the emitted light from the light source so as to be focused on the reflection surface of the measurement object; And a second optical system for condensing the reflected light from the reflecting surface on the light receiving surface of the photodetector, and the light receiving surface of the photodetector is arranged in parallel with and shifted from the optical axis of the reflected light The shift amount is determined such that only a part of the beam spot shape of the reflected light is always incident on the light receiving surface.

  Thereby, the beam spot shape on the light receiving surface of the photodetector changes depending on the position on the optical axis of the reflecting surface of the measurement object. Therefore, the amount of light detected from the photodetector increases or decreases in accordance with the displacement of the reflecting surface from the in-focus position, and thus the amount of displacement of the reflecting surface of the measurement object is obtained by detecting the change in the amount of light. be able to.

  In one embodiment, the first optical system includes a polarizing beam splitter that transmits or reflects light emitted from a light source, an objective lens that focuses the emitted light on a reflection surface of a measurement object, and a polarized beam of the objective lens. A quarter wave plate disposed on the opposite side of the splitter. As a result, the first linearly polarized light separated by the polarization beam splitter is converged by the objective lens, and is converted from linearly polarized light to circularly polarized light by the quarter wavelength plate, and reflected from the measurement object. The light is incident on the surface, is reflected as circularly polarized light in the reverse direction, is again converted into second linearly polarized light by the quarter-wave plate, and is incident on the photodetector.

  In another embodiment, the optical sensor can further be provided with a diaphragm as a measurement object, so that it can be used to measure vibration due to fluid pressure or sound pressure.

  According to still another embodiment, the quarter wavelength plate and the diaphragm are integrated, so that the number of optical components is reduced as compared with the prior art, and the optical path length from the diaphragm to the photodetector is shortened. In addition, when the optical sensor is assembled, the alignment between the quarter-wave plate and the diaphragm can be omitted, and the alignment between them and the other optical system can be completed only once. Therefore, the entire apparatus can be miniaturized, the structure and assembly can be simplified, and a more accurate and reliable optical sensor can be obtained at low cost.

(A) is a block diagram of the first embodiment of the photosensor according to the present invention, and (B) is a diagram showing the beam shape on the light receiving element. (A)-(F) figure is sectional drawing which shows the structure of a wavelength plate unit from which each differs. The block diagram of 2nd Example of the optical sensor by this invention. The block diagram of 3rd Example of the optical sensor by this invention. (A)-(C) is a diagram showing the shape of a beam spot incident on a four-divided light receiving element when the diaphragm is at different positions, and (D) is a diagram showing a displacement signal of the diaphragm.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the accompanying drawings, the same or similar components are denoted by the same or similar reference numerals.

  FIG. 1A shows the configuration of the first embodiment of the optical sensor according to the present invention. The optical sensor 1 of the present embodiment is for detecting vibrations, and includes a light source 2 composed of a laser diode, a flat polarizing beam splitter 3, an objective lens 4, a wave plate unit 5, and light detection. One light receiving element 6 is provided as a part. The wave plate unit 5 is a unitary combination of a quarter wave plate 7 made of a quartz plate and a metal diaphragm 8. The quarter-wave plate 7 and the diaphragm 8 are formed such that the peripheral edge portion on one side is thick in a short cylindrical shape for reinforcement, and the short cylindrical portions are butted together and joined together.

  The polarizing beam splitter 3, the objective lens 4, and the wave plate unit 5 are disposed on the same optical axis x 1 that is orthogonal to the optical axis of the light source 2 with the quarter wave plate 7 on the objective lens side. The light receiving element 6 is made of, for example, a photodiode, and its optical axis x2 is arranged in parallel with the optical axis x1 of the polarization beam splitter 3 or the like and shifted by a slight distance d therefrom.

  The light source 2 is connected to a drive circuit 9 which is a power source and controls the output of the emitted laser light. The light receiving element 6 is connected to a signal processing circuit 10 that processes the output signal and outputs a displacement signal of the diaphragm 8. The signal processing circuit 10 includes, for example, a photoelectric converter and a differential amplifier.

  In the optical sensor 1, the laser light L emitted from the light source 2 as divergent light is reflected by the polarization beam splitter 3 with the linearly polarized component of S-polarized light, converged by the objective lens 4 and incident on the wave plate unit 5. The laser light L incident on the wave plate unit is converted from linearly polarized light to circularly polarized light when passing through the quarter wave plate 7 and projected on the surface of the vibration plate 8 to be reflected as circularly polarized light in the reverse direction. Is done. The reflected light from the surface of the diaphragm 8 passes through the quarter-wave plate 7 again and is converted into P-polarized linearly polarized light, converged by the objective lens 4, transmitted through the polarizing beam splitter 3, and diffused after being imaged. Then, it enters the light receiving element 6.

  FIG. 1B shows the shape of a beam spot incident on the light receiving surface 6 a of the light receiving element 6. The optical axis x2 of the light receiving element 6 is arranged so as to be shifted from the optical axis x1 of the polarization beam splitter 3 as described above. Therefore, the beam spot shape m is projected at a position where the optical axis x1 passes through the center c, that is, at a position away from the center O of the light receiving surface 6a by a distance d.

  As shown in FIG. 1A, the diaphragm 8 is arranged so that the laser light L is focused on the reflecting surface 8a when in the non-displaced state. At this time, the reflected light R0 from the reflecting surface 8a follows the same optical path as that at the time of incidence, reaches the polarization beam splitter 3 while maintaining the same beam cross section as at the time of incidence, passes through this, and enters the light receiving element 6. .

  When the diaphragm 8 is displaced from the non-displacement position S0 toward the optical axis direction, that is, to the position S1 on the ¼ wavelength plate 7 side, the laser light L is reflected on the reflection surface 8a before the focal position S0. Therefore, the reflected light R1 follows the inner optical path from the time of incidence, reaches the polarization beam splitter 3 with a beam cross section somewhat narrower than that at the time of incidence, passes through this, and enters the light receiving element 6. Since the reflected light R1 forms an image before the reflected light R0, the beam spot shape m1 on the light receiving surface 6a appears concentrically and larger than the original beam spot shape m.

  When the diaphragm 8 is displaced from the non-displacement position S0 to the rear side in the optical axis direction, that is, to the position S2 on the opposite side of the quarter wavelength plate 7, the laser light L is reflected to the reflecting surface 8a behind the focal position S0. Accordingly, the reflected light R2 follows the optical path outside the incident time, reaches the polarizing beam splitter 3 with a beam section somewhat thicker than the incident light, passes through this, and enters the light receiving element 6. Since the reflected light R2 forms an image behind the reflected light R0, the beam spot shape m2 on the light receiving surface 6a appears concentrically and smaller than the original beam spot shape m.

  Therefore, the distance d, which is the deviation between the center c of the light receiving surface 6a and the center O of the beam spot shape, always has only a part of the beam spot shape on the light receiving surface 6a regardless of the position on the optical axis of the diaphragm 8. Set to enter. As a result, the beam spot shape on the light receiving surface 6a changes depending on the position of the diaphragm 8 as described above. Accordingly, the amount of light detected from the light receiving element 6 increases or decreases in accordance with the displacement of the diaphragm 8, and the amount of displacement of the diaphragm 8 can be obtained by detecting the change in the amount of light.

  In the optical sensor 1 of this embodiment, the number of optical components is significantly smaller than that of the conventional one. In addition, by using the wave plate unit 5 in which the quarter wave plate 7 and the vibration plate 8 are integrated, the optical path length from the vibration plate 8 to the light receiving element 6 can be significantly shortened. Further, when the optical sensor 1 is assembled, it is not necessary to align the quarter-wave plate 7 and the diaphragm 8, and only one alignment between them and the objective lens 4 is required. As a result, the entire apparatus can be downsized, the assembly of the optical sensor 1 can be simplified, and a highly accurate and reliable apparatus can be obtained at a lower cost.

2A to 2F show wave plate units having various structures different from those of the first embodiment. Waveplate unit 5 ₁ of FIG. 2 (A) is a combination of the diaphragm ₈₁ of the non-metal in the same quarter-wave plate 7 and the first embodiment. Diaphragm ₈₁ is made of a thin plate of glass or quartz or the like, the peripheral portion of one surface side is formed thickly short cylindrical for reinforcement. One side of the quarter-wave plate 7 side of the diaphragm _81, the reflective surface is subjected to metal film is formed. Diaphragm ₈₁ is joined together against the 1/4-wavelength plate 7 a short cylindrical portion together.

Waveplate unit 5 ₂ in FIG. 2 (B) is a combination of the diaphragm ₈₂ of thin tabular same quarter-wave plate 7 and the first embodiment. The diaphragm ₈₂ is a metal plate, is formed of a non-metallic plate such as a hard film or a glass plate. When the diaphragm ₈₂ is such as rigid film or glass plate, the reflecting surface is subjected to metal film is formed on one side of the quarter-wave plate 7 side. The diaphragm ₈₂ is bonded together with 1/4-wave plate 7 in its short cylindrical portion.

Waveplate unit ₃ in FIG. 2 (C) are those in the quarter-wave plate ₇₁ of thin tabular combining same diaphragm 8 in the first embodiment. Quarter-wave plate ₇₁ is formed, for example, a film-like resin material plate. Quarter-wave plate ₇₁ is joined integrally with the diaphragm 8 at the short cylindrical portion.

Figure 2 waveplate unit _{5 4} (D) is a combination of a waveplate unit _{5 1} 3 1/4 wave plate ₇₁ of (C) and FIG. 3 (A). 1/4 wavelength plate ₇₁ and the wavelength plate unit 5 _1, are joined together by butt short cylindrical portion together.

The wave plate unit 5 of the first embodiment and the wave plate units 5 _{1 to} 5 ₄ of FIGS. 2A to 2D are preferably provided with antireflection films on both sides of the quarter wave plate, respectively. . Further, the 1/4 the outer surface of the wave plate 7, 7 _1, can be attached to a thin glass plate 11. By this glass plate 11, the quarter-wave plate can be reinforced to relieve the stress received from the antireflection film and to eliminate the influence of vibration from the diaphragm.

Waveplate unit _{5 5} in FIG. 2 (E) is 1/4-wavelength plate _{7 2} also serves as a diaphragm. Quarter-wave plate 7 _2, as in the first embodiment, consists of a quartz plate, the peripheral portion of one surface side is formed thickly short cylindrical for reinforcement. Quarter-wave plate 7 ₂ of the outer surface i.e. said one side of the short cylindrical portion opposite subjected to metal film 12, the reflective surface is formed. The 1/4 inner surface of the wave plate 7 _2, it is preferable that anti-reflection film.

Waveplate unit _{5 6} of FIG. 2 (F), similar to FIG. 2 (E), 1/4-wavelength plate _{7 3} also serves as a diaphragm. Quarter-wave plate 7 ₃ are formed of the same resin material plate and FIG. 2 (C), the subjected to metal film 12 on the outer surface thereof, the reflecting surface is formed. The inner surface peripheral edge portion of the quarter-wave plate 7 _3, reinforcing members 13 of the short cylindrical metal or glass material is bonded together. The inner surface of the quarter-wave plate 7 _3, it is preferable to an antireflection film.

Also, 1/4-wave plate 7, 7 ₂ is preferably formed by a quartz plate of excellent X-cut or Y-cut to the input angle dependence. Furthermore, 1/4-wave plate 7, 7 _2, by a fundamental wave (zero-order) mode, excellent wavelength dependence is obtained.

  FIG. 3 shows the configuration of a second embodiment of the vibration detecting photosensor according to the present invention. The light sensor 21 of the present embodiment includes a light source 2 composed of a laser diode, a flat polarizing beam splitter 3, an objective lens 4, a wave plate unit 5, and one light detection unit arranged in the same manner as in the first embodiment. In addition to the light receiving element 6, a collimator lens 22 is further provided between the light source 2 and the polarization beam splitter 3 on the same optical axis. A drive circuit 9 is connected to the light source 2, and a signal processing circuit 10 is connected to the light receiving element 6. Instead of the wave plate unit 5, the wave plate units of FIGS. 2A to 2F can be used.

  In the optical sensor 21, the laser light L emitted from the light source 2 is converted into parallel light by the collimating lens 22, the S-polarized linearly polarized component is reflected by the polarization beam splitter 3, and converged by the objective lens 4 to be converged by the wave plate unit. 5 is incident. The laser light L incident on the wave plate unit is converted from linearly polarized light to circularly polarized light when passing through the quarter wave plate 7 and projected on the surface of the vibration plate 8 to be reflected as circularly polarized light in the reverse direction. Is done. Reflected light from the surface of the diaphragm 8 passes through the quarter-wave plate 7 again and is converted into P-polarized linearly polarized light, converted into parallel light by the objective lens 4, and transmitted through the polarizing beam splitter 3 to receive the light receiving element 6. Is incident on.

  The diaphragm 8 is arranged so that the laser light L is focused on the reflecting surface 8a when the diaphragm 8 is in a non-displaced state. At this time, the reflected light from the reflecting surface 8 a follows the same optical path as that at the time of incidence, maintains the same beam cross section as at the time of incidence, passes through the polarization beam splitter 3, and enters the light receiving element 6. The beam spot shape incident on the light receiving surface of the light receiving element 6 is projected at a position where the optical axis x1 passes through the center, that is, at a position away from the center of the light receiving surface by a distance d.

  When the diaphragm 8 is displaced from the non-displacement position S0 toward the optical axis direction, that is, to the position S1 on the ¼ wavelength plate 7 side, the laser light L is reflected on the reflection surface 8a before the focal position S0. The reflected light R follows the inner optical path from the time of incidence, passes through the polarization beam splitter 3 with a beam cross section somewhat narrower than that at the time of incidence, and enters the light receiving element 6. In this case, the beam spot shape on the light receiving surface of the light receiving element 6 is smaller than the original beam spot shape.

  When the diaphragm 8 is displaced from the non-displacement position S0 to the rear side in the optical axis direction, that is, to the position S2 on the opposite side of the quarter wavelength plate 7, the laser light L is reflected to the reflecting surface 8a behind the focal position S0. The reflected light R follows the optical path outside the incident time, passes through the polarization beam splitter 3 with a beam cross section somewhat thicker than the incident time, and enters the light receiving element 6. In this case, the beam spot shape on the light receiving surface of the light receiving element 6 is larger than the original beam spot shape.

  Also in this embodiment, since the shape of the beam spot incident on the light receiving surface of the light receiving element 6 changes depending on the position of the diaphragm 8 as described above, the amount of light detected from the light receiving element 6 depends on the displacement of the diaphragm 8. Increase or decrease correspondingly. Therefore, the displacement amount of the diaphragm 8 can be obtained by detecting the change in the light amount.

  Also in the present embodiment, the number of optical components is significantly reduced as compared with the prior art. Furthermore, the wavelength plate unit 5 in which the quarter wavelength plate 7 and the diaphragm 8 are integrated can significantly shorten the optical path length from the diaphragm 8 to the light receiving element 6. The alignment between the plate 7 and the diaphragm 8 is not necessary, and the alignment between the plate 7 and the objective lens 4 can be performed only once. Therefore, the entire apparatus can be miniaturized, the structure and the assembly can be simplified, and a more accurate and reliable optical sensor can be obtained at a lower cost.

  FIG. 4 shows the configuration of a third embodiment of the vibration detection photosensor according to the present invention. The optical sensor 31 of this embodiment includes a light source 2 composed of a laser diode, a collimating lens 22, a flat polarizing beam splitter 3, an objective lens 4, and a wave plate unit 5 arranged in the same manner as in the second embodiment. A quadrant light receiving element 32 as a detection unit is used, and a cylindrical lens 33 is disposed between the quadrant light receiving element and the polarization beam splitter 3. The four-divided light receiving element 32 and the cylindrical lens 33 are disposed on the same optical axis as that of the polarization beam splitter 3. For example, a quadrant photodiode is used as the quadrant light receiving element 32. Instead of the wave plate unit 5, the wave plate units of FIGS. 2A to 2F can be used.

  In the optical sensor 21, the laser light L emitted from the light source 2 is converted into parallel light by the collimating lens 22, the S-polarized linearly polarized component is reflected by the polarization beam splitter 3, and converged by the objective lens 4 to be converged by the wave plate unit. 5 is incident. The laser light L incident on the wave plate unit is converted from linearly polarized light to circularly polarized light when passing through the quarter wave plate 7 and projected on the surface of the vibration plate 8 to be reflected as circularly polarized light in the reverse direction. Is done. Reflected light from the surface of the diaphragm 8 passes through the quarter-wave plate 7 again and is converted into P-polarized linearly polarized light, converted into parallel light by the objective lens 4, transmitted through the polarizing beam splitter 3, and the cylindrical lens 33. , And astigmatism is given, and enters the four-divided light receiving element 32.

  The diaphragm 8 is arranged so that the laser light L is focused on the reflecting surface 8a when the diaphragm 8 is in a non-displaced state. At this time, the reflected light R from the reflecting surface 8a follows the same optical path as that at the time of incidence, passes through the polarization beam splitter 3 while maintaining the same beam cross section as that at the time of incidence, and converges on the cylindrical lens 33 to form an image. Thereafter, the light enters the four-divided light receiving element 32. FIG. 5A shows the beam spot shape M0 incident on the light receiving surface 32a of the four-divided light receiving element at this time. The beam spot shape M0 is a circle with its center placed at the center of the four-divided light receiving element 32.

  When the diaphragm 8 is displaced from the non-displacement position S0 toward the optical axis direction, that is, to the position S1 on the ¼ wavelength plate 7 side, the laser light L is reflected on the reflection surface 8a before the focal position S0. The reflected light R follows an inner optical path from the time of incidence, passes through the polarization beam splitter 3 with a beam cross section somewhat narrower than that at the time of incidence, converges on the cylindrical lens 33, and forms an image. 32 is incident. FIG. 5B shows the beam spot shape M1 incident on the light receiving surface 32a of the four-divided light receiving element at this time. The beam spot shape M1 is a horizontally long ellipse whose center is located at the center of the four-divided light receiving element 32.

  When the diaphragm 8 is displaced from the non-displacement position S0 to the rear side in the optical axis direction, that is, to the position S2 on the opposite side of the quarter wavelength plate 7, the laser light L is reflected to the reflecting surface 8a behind the focal position S0. The reflected light R follows an optical path outside the incident light, passes through the polarization beam splitter 3 with a beam cross section somewhat thicker than the incident light, converges on the cylindrical lens 33, and forms an image. 32 is incident. FIG. 5C shows a beam spot shape M2 incident on the light receiving surface 32a of the four-divided light receiving element at this time. The beam spot shape M2 is a vertically long ellipse whose center is placed at the center of the quadrant light receiving element 32.

  As shown in the figure, the output signals of the light receiving elements of the four-divided light receiving element 32 are Va, Vb, Vc, and Vd from their positions. At this time, the displacement signal V0 of the diaphragm 8 is expressed by V0 = (Va + Vd) − (Vb + Vc). FIG. 5D shows the displacement amount of the diaphragm 8 with the zero point on the horizontal axis as the focal position of the laser beam L, and the displacement signal V0 on the vertical axis. The displacement signal V0 is an S-order curve in which a certain range changes substantially linearly on both sides of +/− with respect to the zero point. Therefore, the displacement amount of the diaphragm 8 can be obtained from the displacement signal V0 within this linear range.

  Also in this embodiment, the wave plate unit 5 in which the quarter wave plate 7 and the vibration plate 8 are integrated reduces the number of optical components compared to the conventional one, and the optical path length from the vibration plate 8 to the light receiving element 6 is greatly increased. Therefore, when the optical sensor 1 is assembled, the alignment of the quarter-wave plate 7 and the diaphragm 8 is unnecessary, and the alignment between the objective lens 4 and the quarter-wave plate 7 can be completed only once. Therefore, the entire apparatus can be miniaturized, the structure and the assembly can be simplified, and a more accurate and reliable optical sensor can be obtained at a lower cost.

  Each of the above embodiments is an optical sensor for vibration detection, and is provided with a diaphragm for this purpose. However, the present invention can be used to measure the position and displacement of the measurement object separate from the optical sensor, the vibration of the surface to be measured, and the like. In that case, the wave plate unit may be replaced with a single quarter wave plate, the vibration plate may be omitted, and the laser light may be set to be focused on the surface to be measured of the measurement object.

  Various configurations other than the above-described embodiment are conceivable as an optical system for condensing and projecting laser light on the diaphragm and an optical system for causing reflected light from the diaphragm to enter the light receiving element. For example, the linearly polarized component of the laser light emitted from the light source and transmitted through the polarizing beam splitter can be projected onto the diaphragm, and the reflected light can be reflected by the polarizing beam splitter and incident on the photodetector. .

  The present invention is not limited to the above embodiments, and can be implemented with various modifications or changes within the technical scope thereof. For example, in the first and second embodiments, as long as the displacement of the diaphragm can be detected as a change in the amount of light, the light detection unit can be configured with a plurality of light receiving elements. The polarizing beam splitter can be a prism type. Various known light sources other than the laser diode can be used as the light source.

DESCRIPTION OF SYMBOLS 1, 21, 31 ... Optical sensor, 2 ... Light source, 3 ... Polarizing beam splitter, 4 ... Objective lens, 5 ... Wave plate unit, 6 ... Light receiving element, 6a, 32a ... Light receiving surface, 7 ... 1/4 wavelength plate, DESCRIPTION OF SYMBOLS 8 ... Diaphragm, 9 ... Drive circuit, 10 ... Signal processing circuit, 8a ... Reflecting surface, 11 ... Glass plate, 12 ... Metal film, 13 ... Reinforcing member, 22 ... Collimator lens, 32 ... Quadrant light receiving element, 33 ... Cylindrical lens.

Claims (4)

A light source, a light detector, a first optical system that focuses light emitted from the light source so as to be focused on the reflection surface of the measurement object, and light reception by the light detector from the reflection surface A second optical system for focusing on the surface,
The light receiving surface of the photodetector is arranged with its optical axis parallel to and shifted from the optical axis of the reflected light, and the amount of shift is always only a part of the beam spot shape of the reflected light. An optical sensor that is determined to be incident on a surface.   The first optical system transmits or reflects the outgoing light from the light source, an objective lens that condenses the outgoing light on the reflecting surface of the diaphragm, and the polarizing beam splitter of the objective lens 2. The optical sensor according to claim 1, further comprising a quarter-wave plate disposed on the opposite side of the optical sensor.   The optical sensor according to claim 1, further comprising a diaphragm as the measurement object.   4. The optical sensor according to claim 3, wherein the quarter-wave plate is integrated with the diaphragm.

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