JP2006029912A - Optical mobile information detector, encoder and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical mobile information detector, an encoder and electronic equipment capable of suppressing occurrence of dropout and accurately detecting information concerning the position. <P>SOLUTION: Emission light from LD1 is converted by CL2 into a parallel light flux, transmitted through a diaphragm and split into a first light flux 5 and a second light flux 6 by BS4. The first light flux 5 irradiates a reflection surface of an object to be measured 9 at OL8, and the second light flux 6 irradiates the reflection surface of the object to be measured 9 at OL8 by way of a mirror 7. As the reflection surface of the object to be measured 9 has a cross sectional shape corresponding to the isosceles sides of an isosceles triangle with base angles of θ, the first light flux 5a and the second light flux 5b can be specularly reflected to the direction perpendicular to the bottom of the isosceles triangle. By the specular reflection light of the first light flux 5a and the second light flux 5b, interference light with relatively large light intensity can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical movement information detection apparatus, an encoder, and an electronic apparatus, and irradiates a laser beam to a moving object to be measured and receives reflected light including a frequency shift of light according to the moving speed of the object to be measured. The present invention relates to a Doppler-type optical movement information detection device, an encoder, and an electronic device that detect the speed of the object to be measured.

  In general, when the light source and the observer are moving relative to each other, the light from the light source undergoes a change in frequency due to the Doppler effect. A laser Doppler velocimeter (hereinafter referred to as LDV (Laser Doppler Velocimeter)) utilizes this phenomenon, and irradiates a moving measurement object with a laser beam, thereby performing Doppler of scattered light from the measurement object. The frequency shift is measured, and the moving speed of the object to be measured is measured. Such LDV was published by Yeh and Cummins in 1964 (Appl. Phys. Lett. 4-10 (1964) 176) and is now widely known and put into practical use.

  FIG. 9 shows a conventional LDV optical system. In FIG. 9, 101 is a laser diode (hereinafter referred to as LD (Laser Diode)) that is a semiconductor laser, 102 is a photodiode (hereinafter referred to as PD (Photo Diode)) that is a light receiving element, and 103 is a diffraction grating. , 104 is a collimator lens (hereinafter referred to as CL), 105 is a mirror, 106 is a condenser lens, 107 is a first light beam of + 1st order diffracted light by the diffraction grating 103, and 108 is -1st order diffracted light by the diffraction grating 103. A second light beam 113 is an object to be measured.

  In the optical system configured as described above, the laser light emitted from the LD 101 is converted into a parallel light beam by the CL 104, and then divided into ± first-order diffracted light at a diffraction angle of θ by the diffraction grating 103, so that the first and second light beams are obtained. 107 and 108. The first and second light beams 107 and 108 are respectively reflected by the mirror 105, then enter the surface of the object to be measured 113 at an incident angle θ, and are scattered by the object to be measured 113. Overlap each other. The first and second light beams 107 and 108 scattered by the object to be measured 113 have undergone Doppler frequency shift and are slightly different from the oscillation frequency of the LD 101. For this reason, the interference wave of the said 1st and 2nd light beams 107 and 108 produces a beat. This beat is called a beat signal. The moving speed of the DUT 113 can be obtained by heterodyne detection of the beat frequency of the beat signal by the PD 102. Hereinafter, a method for obtaining the moving speed of the DUT 113 will be described in detail.

Now, assuming that the direction in which the DUT 113 moves (rightward in FIG. 9) is the positive direction, the first light beam 107 is subjected to a −f _d Doppler frequency shift, and the first light beam 108 is subjected to a + f _d Doppler frequency shift. The apparent frequency of the first luminous flux 107 is (f ₀ −f _d ), and the apparent frequency of the second luminous flux 108 is (f ₀ + f _d ). However, f ₀ is the oscillation frequency of the LD101. At this time, since the electric field of the light emitted from the LD 101 can be expressed as E ₀ · cos (2πf ₀ t), the first light beam 107 can be expressed by the following Equation 1, and the second light beam 108 is It can be represented by the following formula 2.

In Equations 1 and 2 above, f ₀ is the frequency of the emitted light from the LD 101, E ₀ is the amplitude of the emitted light from the LD 101, E _A is the amplitude of the first light beam 107, and E _B is the amplitude of the second light beam 108. , Φ _A is the phase of the first light beam 107, and φ _B is the phase of the second light beam 108.

と表すことができる。ただし、式３で左辺の＜＞は時間平均を表す。このように、光の周波数よりも大幅に小さい上記干渉波の周波数は、上記ＰＤ１０２で測定することができる。 Since the frequency of light is generally about 100 THz (10 ¹⁴ Hz), the frequency information of Formula 1 and Formula 2 cannot be directly measured. For this reason, heterodyne detection is generally used as described above. That is, since f0 >> fd holds, the interference wave of the light of the formulas 1 and 2 is

It can be expressed as. However, <> on the left side in Equation 3 represents a time average. As described above, the frequency of the interference wave that is significantly smaller than the frequency of light can be measured by the PD 102.

  FIG. 10 is a diagram of the object to be measured 113 moving at the moving speed V when two light beams enter the object to be measured 113 at angles α and β, respectively, and receive scattered light at the position of angle γ. .

Strictly speaking, the amount of frequency shift due to the Doppler effect is obtained by using the Lorentz transformation based on relativity, but when the moving speed V is sufficiently smaller than the light speed c, it can be obtained approximately as follows. The relative velocities V _A1 and V _B1 of the light from the light sources A and B and the moving object are expressed by the following equations 4 and 5.

The apparent frequencies f _A1 and f _B1 of the light viewed from the object to be measured 113 are expressed by the following equations 6 and 7.

The respective scattered (reflected) light and the relative velocities V _A2 and V _B2 of the object 113 to be measured are expressed by the following equations 8 and 9.

Therefore, the light frequencies f _A2 and f _B2 viewed from the observation point can be expressed by the following equations 10 and 11.

The difference between the frequency frequencies f _A2 and f _{B2 of} Equations 10 and 11 and the frequency f ₀ (= c / λ) of the incident light is the Doppler frequency shift amount f _d . Now, the beat frequency 2f _d (see Equation 3) of the two light beams measured at the observation point is expressed by the following Equation 12 because c >> V.

Therefore, it can be seen that the beat frequency 2f _d does not depend on the position of the observation point (angle: γ). In FIG. 10, assuming that α = β = θ, in the general LDV optical system of FIG.

Accordingly, the moving speed V of the DUT 113 can be obtained by measuring the frequency 2f _d represented by the expression 3 and calculating it using the expression 13.

Equation 13 can also be considered geometrically as follows. FIG. 11 is an enlarged view of a region where the two light beams (first and second light beams 107 and 108) in FIG. 9 overlap. The two light beams intersect with each other at an angle 2θ, and the broken line in the figure indicates a part of the equiwavefront of each light beam. The distance between the broken line and the broken line is the light wavelength λ. Further, when the band-like region is a bright portion of the interference fringes and the interval is Δ, this Δ is expressed as the following Expression 14.

As shown in FIG. 11, when the object 114 passes through the interference fringes vertically at the moving speed V, the frequency f, which is the number of the object 114 crossing the interference fringes per unit time, is expressed as the following Expression 15. Is done.

Therefore, it is equal to the beat frequency 2f _{d of} Equation 13.

  However, the above relationship is established under ideal conditions. More specifically, this is true when there is no phase disturbance when the incident laser light is reflected by the object to be measured, and the reflectance of the object to be measured is constant regardless of the location. In reality, when a moving object to be measured is continuously measured, for example, a signal missing state in which the amplitude of the beat signal becomes very small as shown in FIG. 12 appears. Such a state is called a dropout. When this dropout occurs, there is a problem that it becomes a signal insensitive state and movement information of the object to be measured cannot be detected.

  JP-A-4-25792 (Patent Document 1) discloses a Doppler velocimeter that solves such a problem. This speedometer determines that a dropout has occurred when the Doppler signal level falls below a certain value. Then, until the signal returns again and the level of the Doppler signal reaches a certain value or more, a signal having a constant strength having the same frequency as the frequency immediately before the dropout is generated is generated. Interpolate the signal. In this way, a drop in detection accuracy when dropout occurs is prevented.

  In another conventional speedometer (Japanese Patent Laid-Open No. 7-229911: Patent Document 2), scattered light from the same region is detected by a plurality of detectors, and a dropout is generated in a signal from one detector. When it occurs, it switches to a signal from another detector. This reduces the probability that speed detection will be impossible due to the occurrence of a signal insensitive state.

  However, the conventional Doppler velocimeter that complements the signal at the time of dropout interpolates with the signal immediately before the dropout, so if there is a change in the moving speed of the object to be measured during the dropout, the measured value will have an error. Occurs and becomes inaccurate. Therefore, as the dropout period becomes longer, the error becomes larger, and there is a problem that high-precision measurement cannot be performed.

In addition, the conventional speedometer using multiple detectors makes it impossible to measure when dropouts occur at the output of all detectors at the same time, and erroneously determines that the object to be measured is in the “stop” state. There is a problem of being done.
JP-A-4-25792 JP-A-7-229911

  Therefore, an object of the present invention is to provide an optical movement information detection device, an encoder, and an electronic apparatus that can suppress the occurrence of dropout and can detect information about a position with high accuracy.

In order to solve the above problems, the optical movement information detection device of the present invention is
A semiconductor light emitting device that emits coherent light;
A light branching element that splits the light emitted from the semiconductor light emitting element into a first light flux and a second light flux;
An object to be measured having at least two reflecting surfaces for reflecting the first luminous flux and the second luminous flux in substantially the same direction;
A first optical system for guiding the first and second light fluxes onto the reflecting surface;
A light receiving element that receives interference light obtained by the reflected light of the first light flux and the reflected light of the second light flux;
A second optical system for guiding the reflected light of the first light flux and the reflected light of the second light flux to the light receiving element;
And a signal processing circuit for processing a signal from the light receiving element and calculating a moving speed of the object to be measured.

  According to the above configuration, the first light beam and the second light beam are reflected by at least two reflecting surfaces of the object to be measured, so that the phase (wavefront) of each light beam is hardly disturbed. Therefore, uniform interference light can be obtained by the first and second light beams, and the movement speed of the object to be measured can be detected with high accuracy by detecting the change in the intensity of the interference light as a beat signal.

In the optical movement information detecting device according to an embodiment, an incident angle of the first light beam with respect to a direction perpendicular to the moving direction of the object to be measured is 2α, and the second light beam with respect to a direction perpendicular to the moving direction of the object to be measured. When the incident angle is 2β,
The reflecting surfaces of the object to be measured are at least two reflecting surfaces each having an angle of α and β with respect to the moving direction of the object to be measured.

  According to the embodiment, since the specularly reflected light of the first and second light beams can be reflected in substantially the same direction, an interference signal can be obtained efficiently.

  In the optical movement information detection device of one embodiment, the reflection surface of the object to be measured has a shape that periodically changes in the moving direction of the object to be measured.

  According to the embodiment, since the reflection surface has a shape that periodically changes in the moving direction of the object to be measured, the interference light of the first and second light beams reflected by the reflection surface is continuously generated. Can be obtained stably. Therefore, highly accurate measurement can be performed over a long time and a long distance.

  In the optical movement information detecting device according to one embodiment, α and β are substantially the same, and two adjacent reflecting surfaces are equal to each other in an isosceles triangle in a cross section in the moving direction of the object to be measured. It has a shape corresponding to two sides.

  According to the embodiment, when calculating the movement information of the object to be measured based on the reflected light from the reflection surface, only one angle information is necessary in the processing of the signal processing circuit. Therefore, the calculation by the signal processing circuit can be simplified.

  In the optical movement information detection device of one embodiment, the reflection surface of the object to be measured has irregularities that undulate in a range smaller than the wavelength of the emitted light of the semiconductor light emitting element.

  According to the embodiment, the unevenness of the reflecting surface is undulated in a range smaller than the wavelengths of the first and second light beams incident on the reflecting surface, so that the phase of the reflected light of the light beam is disturbed. There is no. Therefore, a continuous and stable beat signal can be obtained.

  In one embodiment of the optical movement information detecting device, the reflection surface of the object to be measured is an optical mirror.

  According to the above embodiment, a stable beat signal can be obtained reliably and continuously.

  In the optical movement information detecting device according to an embodiment, the first and second light beams are more than half the length of the base of the isosceles triangle on the reflection surface of the object to be measured. Has a large irradiation dimension.

  According to the embodiment, the irradiation size of the first and second light fluxes on the reflecting surface is larger than ½ of the length of the base of the isosceles triangle that is the shape in the cross section of the reflecting surface. The first and second light beams can be positively reflected in a predetermined direction with certainty.

  In the optical movement information detecting device of one embodiment, the first and second light fluxes have an irradiation dimension substantially equal to a length of a base of the isosceles triangle on the reflecting surface of the object to be measured. Have.

  According to the embodiment, since the light amounts of the first and second light beams reflected by the reflecting surface can be made substantially the same, a signal with a high S / N (signal / noise ratio) can be obtained.

  In the optical movement information detection device of one embodiment, the base angle of the isosceles triangle is 30 °.

  According to the embodiment, since the isosceles triangle shape in the cross section of the reflecting surface has a base angle of 30 °, the first and second light beams can be efficiently guided to the light receiving element. Therefore, it is possible to reduce the amount of emitted light of the semiconductor light emitting element necessary for obtaining a predetermined signal intensity, and to reduce the power consumption of the optical movement information detecting device.

  The optical movement information detection device according to an embodiment includes a pinhole that allows the reflected light of the first and second light beams to pass between the reflection surface of the object to be measured and the light receiving element.

  According to the embodiment, when there is an error in the incident angle of the light beam to the reflection surface or the angle that the reflection surface has with respect to the traveling direction of the object to be measured, the specularly reflected light reflected by the reflection surface Deviation occurs in the traveling direction. Here, only the light that should be incident on the light receiving element out of the shifted specularly reflected light can be extracted by the pinhole, so even if the error occurs, a beat with a relatively good S / N is obtained. A signal can be obtained.

  Instead of the pinhole, for example, a lattice or a slit may be provided.

  In the optical movement information detecting device according to an embodiment, the first and second light fluxes have substantially the same amount of light.

  According to the above embodiment, since the light amounts of the first and second light beams are substantially equal to each other, a signal having a good S / N can be obtained.

When the reflected light of the first and second light fluxes is expressed by the following expressions 16 and 17, the optical movement information detecting device of one embodiment relates to the following expression 18 with respect to the reflected light of the first and second light fluxes. The relationship is established.
A · cos ((w ₀ −w _d ) t) (16)
B · cos ((w ₀ −w _d ) t−6π / λ · Ltan θ) (17)
−2 / 3π + 2 (n−1) π <6π / λ · Ltanθ <2 / 3π + 2 (n−1) π (18)
Here, A is the light intensity of the first light beam, B is the light intensity of the second light beam, w ₀ is the frequency of the light from the semiconductor light emitting element, w _d is the Doppler frequency deviation, t is the time, and λ is The wavelength of light from the semiconductor light emitting element, L is ½ the length of the base of the isosceles triangle of the reflecting surface of the object to be measured, θ is the base angle of the isosceles triangle, and n is a natural number. is there.

  According to the embodiment, satisfying the equations 16 to 18 restricts the phase difference between the reflected lights of the first and second light fluxes within a predetermined range, so that the interference light of the reflected light is weakened. It is prevented. Therefore, since the light having a relatively high intensity can be received by the light receiving element, the movement information of the object to be measured can be detected with high accuracy.

The optical movement information detection device of one embodiment
With respect to the reflected light of the first and second light beams, the following expressions 19 and 20 are satisfied.
A ≠ B (19)
3L / λ · tan θ <(2m−1) (20)
Here, m is a natural number.

  According to the above embodiment, the reflected lights of the first and second light beams are reliably prevented from canceling out and disappearing due to the relationship of the above equations 19 and 20. Therefore, this optical movement information detection device can reliably perform a stable information detection operation.

  An encoder of the present invention includes the optical movement information detection device.

  According to the above configuration, an encoder capable of stably detecting the position and speed of the object to be measured with high accuracy can be obtained.

  In the encoder according to an embodiment, the reflecting surface is arranged in an annular shape on the object to be measured.

  According to the embodiment, a rotary encoder that detects the speed and position of the rotating object to be measured can be formed by arranging the reflecting surface in an annular shape on the object to be measured.

  In an optical movement information detecting device according to an embodiment, the object to be measured is formed of a Si (silicon) wafer, and a reflection surface of the object to be measured is formed by anisotropic etching.

  According to the embodiment, by performing anisotropic etching along the surface orientation of the Si wafer, the object to be measured has a predetermined inclination angle accurately and has a relatively small surface unevenness. Can be easily formed.

The optical movement information detecting device of the present invention is
A semiconductor light emitting device that emits coherent light;
A first light branching element that splits light emitted from the semiconductor light emitting element into a first light flux and a second light flux;
A second optical branching element that splits the first luminous flux into third and fourth luminous fluxes;
A third light branching element that splits the second light flux into fifth and sixth light fluxes;
An object to be measured having at least four reflecting surfaces for reflecting the third and fourth light beams in substantially the same direction and reflecting the fifth and sixth light beams in substantially the same direction;
A first optical system for guiding the third and fourth light fluxes to a first position on the reflecting surface;
A second optical system for guiding the fifth and sixth light beams to a second position on the reflecting surface;
A first light receiving element that receives interference light obtained by the reflected light of the third light beam and the reflected light of the fourth light beam;
A second light receiving element that receives interference light obtained by the reflected light of the fifth light beam and the reflected light of the sixth light beam;
A third optical system for guiding the reflected light of the third light flux and the reflected light of the fourth light flux to the first light receiving element;
A fourth optical system for guiding the reflected light of the fifth light flux and the reflected light of the sixth light flux to the second light receiving element;
And a signal processing circuit for processing signals from the first and second light receiving elements to calculate a moving speed of the object to be measured.

  According to the above configuration, two of the four reflecting surfaces of the object to be measured reflect the third and fourth light beams to obtain interference light, and the four reflecting surfaces of the object to be measured. The other two reflecting surfaces can reflect the fifth and sixth light beams to obtain interference light. Therefore, two-dimensional movement information can be detected with high accuracy with respect to the object to be measured.

  In the optical movement information detecting device of one embodiment, the reflection surface of the object to be measured has a shape in which protrusions having a quadrangular prism shape are periodically arranged.

  According to the embodiment, the reflection surface of the object to be measured has a shape in which the protrusions having the side surfaces of the quadrangular prism shape are periodically arranged, so that the third and fourth light beams are reflected in substantially the same direction. In addition, the fifth and sixth light beams can be reflected in substantially the same direction.

  In the optical movement information detecting device of one embodiment, the reflection surface of the object to be measured has a shape in which depressions having a quadrangular prism-shaped side surface are periodically arranged.

  According to the embodiment, since the reflection surface of the object to be measured has a shape in which depressions having a quadrangular prism side surface are periodically arranged, the third and fourth light beams can be reflected in substantially the same direction. At the same time, the fifth and sixth light beams can be reflected in substantially the same direction.

  In one embodiment of the optical movement information detecting device, the first and second light receiving elements are formed on the same substrate.

  According to the embodiment, by forming the first and second light receiving elements on the same substrate, the optical movement information detecting device can be reduced in size and the cost can be reduced.

  In the optical movement information detecting device according to an embodiment, the light receiving element and the signal processing circuit are formed on the same substrate.

  According to the embodiment, by forming the light receiving element and the signal processing circuit on the same substrate, the optical movement information detecting device can be miniaturized and the cost can be reduced.

  The electronic apparatus of the present invention includes the optical movement information detection device.

  According to the above configuration, since the optical movement information detection device capable of detecting the movement information of the object to be measured with high accuracy is provided, an electronic apparatus capable of controlling the operation relating to the object to be measured with high accuracy can be obtained.

  The electronic device of the present invention includes the encoder.

  According to the above configuration, since the encoder capable of detecting the movement information of the object to be measured with high accuracy is provided, an electronic apparatus capable of controlling the operation relating to the object to be measured with high accuracy can be obtained.

  As described above, the optical movement information detecting apparatus of the present invention divides the semiconductor light emitting element that emits coherent light and the light emitted from the semiconductor light emitting element into the first light flux and the second light flux. An optical branching element, an object to be measured having at least two reflecting surfaces that reflect the first and second light beams in substantially the same direction, and the first and second light beams are guided onto the reflecting surface. A first optical system; a light receiving element that receives interference light obtained by the reflected light of the first light flux and the reflected light of the second light flux; the reflected light of the first light flux; and the reflected light of the second light flux. A second optical system that leads to the light receiving element; and a signal processing circuit that processes a signal from the light receiving element and calculates a moving speed of the object to be measured. Since interference light is obtained, the change in the intensity of this interference light is used as the beat signal. By detecting Te, it can detect the moving speed of the object to be measured with high accuracy.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

(First embodiment)
FIG. 1 is a schematic configuration diagram showing a Doppler velocimeter (LDV) as an optical movement information detecting device according to a first embodiment of the present invention. In FIG. 1, only the main components of the optical component and the trajectory of the light beam are shown, and the components that hold the optical component are not shown. Here, as the light source, a light emitting diode (hereinafter referred to as LED (Light Emitting Diode)), a semiconductor laser (hereinafter referred to as LD (Laser Diode)), or the like can be used, and a beat due to interference of two light beams is easily generated. For this, LD is desirable. However, for example, an LED such as a current confined LED may be used as long as it has coherence within the optical path length of the optical system. In the first embodiment, an LD is used.

  In the present embodiment, light emitted from the LD 1 is converted into a parallel light beam by a collimator lens (hereinafter referred to as CL) 2. In general, the intensity distribution of the light emitted from the LD has a Gaussian distribution around the optical axis and becomes an elliptical far field pattern (FFP). For this reason, if the emitted LD light is irradiated to the detection point as it is, unevenness of the light intensity is generated on the detection point, and the intensity of the interference fringes is not uniform, making it difficult to detect the beat signal with high accuracy. Become. Therefore, in the present embodiment, for example, a circular diaphragm 3 is provided in order to cut a portion having a low light intensity outside the light beam to form a circular light beam having a uniform light intensity. Further, in the present embodiment, the polarization direction of the emitted light from the LD is described as a direction perpendicular to the paper surface in order to handle it as an S wave, but is not limited thereto.

  The light that has passed through the diaphragm 3 is split into a first light beam 5 and a second light beam 6 by a beam splitter (hereinafter referred to as BS) 4 as an example of an optical branching element. The traveling direction of the second light beam 6 is changed by the mirror 7, and enters the condenser lens (hereinafter referred to as OL) 8 in parallel with the first light beam 5. The second light beam 6 is applied to the same spot as the first light beam 5 on the reflection surface of the object 9 to be measured arranged at the focal length of the OL 8. Here, the reflection surface of the object to be measured 9 has a shape corresponding to two sides having the same length of an isosceles triangle in a cross section parallel to the moving direction of the object to be measured 9. The first and second light beams 5 and 6 incident on the OL 8 have optical axes parallel to each other and are perpendicular to the base of the isosceles triangle.

  In FIG. 1, OL8 is used as means for irradiating the first and second light fluxes 5 and 6 to the same spot on the reflection surface of the object 9 to be measured. However, for example, a mirror or the like may be used.

  The two light beams 5 and 6 irradiated to the object to be measured 9 are regularly reflected in substantially the same direction by two adjacent reflecting surfaces of the object to be measured 9. The direction of regular reflection is a direction substantially perpendicular to the base of the isosceles triangle. As a result, interference occurs between the two light beams 5 and 6. The interference light (interference signal) is converted into an electrical signal by the light receiving element 10 after passing through the OL 8. This electric signal is processed by a signal processing circuit unit (not shown), and the speed of the device under test 9 is calculated.

FIG. 2 is an example of a waveform measured in an LDV including the optical system of this embodiment and the device 9 to be measured. In FIG. 2, the horizontal axis is time, and the vertical axis is the output of the light receiving element 10. In this embodiment, the specularly reflected light component of the reflected light is received, so that the wave front is distorted compared to the case of irradiating the substantially uniform reflecting surface as in the conventional LDV of FIG. There is almost no. The diffused light received by the conventional LDV has a light phase difference caused by the optical path length difference due to the unevenness of the reflecting surface. If light is considered as an infinitely thin bundle of light beams, each of the light beams is considered to have a different phase. Since the aggregate of these light beams can be considered as an infinite series sum with different EA and φA in the above formula 1, for example, if the reflected light from the first light beam 5 is the first reflected light, this first reflected light Can be expressed as in Equation 21 below.

Similarly, when the reflected light of the second light beam 6 is the second reflected light, the second reflected light can be expressed as in the following Expression 22.

Therefore, the interference (beat) signal due to the first and second reflected lights is expressed by the following Expression 23.

When Expression 23 is expanded, it becomes m × n sums of the beat signals of Expression 3 above. As a result, they can be synthesized so as to be represented by one trigonometric function. However, since the object to be measured 9 is moving, the reflection point changes from moment to moment for each light beam, so that the surface reflectance changes with time. Therefore, the coefficients EA and EB representing the amplitude also change with time, and φm and ψn representing the phase of each light beam also change with time due to the unevenness of the reflecting surface. Therefore, the above equation 23 can be rewritten as the following equation 24.

  With respect to the interference light changing in this way, in the conventional LDV, the amplitude and phase change with time, so that the surface shape of the object to be measured 9 is such that E (t), which is the sum of the luminous fluxes, is almost zero. When the condition is satisfied, a dropout state occurs as in the waveform shown in FIG. As a result, the conventional LDV cannot detect the speed.

  On the other hand, in the LDV of the present embodiment, the reflection surface of the DUT 9 has an angle corresponding to the incident angle of the incident light beam, and the reflection surface is a smooth surface with few irregularities. Therefore, the reflected light beam reflected by the reflecting surface is reflected in a predetermined direction (in the present embodiment, the direction perpendicular to the base of the isosceles triangle) with almost no disturbance in phase. In the reflected light beam, the phase terms φm and ψn all have constant values in the above formulas 21 and 22. If the phase is a constant value, the reflectance of the surface of the object to be measured 9 is uneven, the object to be measured 9 moves, or the amplitude coefficients of the equations 21 and 22 change over time. However, the amplitude never theoretically becomes zero. In the LDV from which the experimental result of FIG. 2 is obtained, the surface of the reflection surface of the DUT 9 is uniformly formed, so that the amplitude coefficient hardly changes with time. Therefore, a beat signal with almost no change in amplitude over time can be obtained.

  In this way, since an inclination angle is provided on the surface of the object to be measured 9 and a light beam is incident in accordance with this angle, dropout can be prevented, so that an LDV signal can be detected with high accuracy for each pulse. can do. In addition, since the shape of the reflection surface of the DUT 9 is periodically continuous within the measurement range with respect to the moving direction, a stable signal can be continuously measured.

  In FIG. 1, the shape of the reflecting surface of the DUT 9 is a periodic structure in which isosceles triangles having a low angle of θ are continuously connected to form isosceles sides. Correspondingly, the incident angle of the first and second light beams 5 and 6 is set to 2θ. At this time, as shown by the above equation 13, one of the parameters required for calculating the velocity can be omitted, such as the angle of the reflecting surface and the incident angle. Therefore, the signal processing circuit unit can be simplified.

  Furthermore, the incident angles of the first and second light beams 5 and 6 on the reflecting surface may be set symmetrically. Accordingly, when the first and second light beams 5 and 6 are superimposed on the object 9 to be measured using a lens, the normal lens 8 is used and the first and second light beams 5 and 6 are parallel to the lens 8. It is sufficient to make it incident. In addition, when using the mirror or the like to change the traveling directions of the two light beams 5 and 6 and superimposing them on the object 9 to be measured, the mirror is inclined at the same angle with respect to the object 113 to be measured. Therefore, the apparatus configuration can be simplified.

Further, when the wavelength of the incident light on the reflecting surface is λ and the uneven step on the reflecting surface of the DUT 9 is d, the light reflection on the reflecting surface is satisfied by satisfying the relationship of d <λ. Can be specularly reflected. Here, since the phases of the first and second light beams 5 and 6 are aligned, the value of (φ _A −φ _B ) in the above equation 3 does not change with time, and as a result, a signal having a stable intensity is obtained. Can be obtained. Such a reflection surface of the DUT 9 can be formed by an optical mirror having the above-mentioned isosceles triangle structure, a Si wafer, or the like. In particular, by performing anisotropic etching using the surface orientation of a Si wafer, reflection surfaces having a V-shaped cross section and having a predetermined angle with each other can be accurately formed.

  Further, as shown in FIG. 1, with respect to the isosceles triangle formed by the reflecting surface of the object to be measured 9 in the cross section, when the base length is 2L, the object to be measured is caused by the incident first and second light beams 5 and 6. The diameter of the beam spot formed on 9 is set to be larger than L. In particular, the beam spot diameter is preferably 2L. By making the beam spot diameter larger than L, it is possible to always obtain the same amount of reflected light from both the right-upward reflecting surface and the right-down reflecting surface in FIG. If it is small, a time zone in which only one light beam is reflected occurs). Therefore, an interference signal can be obtained stably. In particular, when the beam spot is 2L, the reflected light amount of the first light beam is always equal to the reflected light amount of the second light beam, so that an interference signal with a good S / N can be obtained.

  Further, as shown in FIG. 3, the low angle θ of the isosceles triangle formed by the reflecting surface of the DUT 9 is 30 °, and the incident angles of the first and second light beams 5 and 6 are the isosceles 3. When the angle is 60 ° with respect to the direction perpendicular to the base of the square, all the incident light beams 5 and 6 are regularly reflected vertically. Therefore, all the energy of the light incident on the object to be measured 9 can be changed to an interference signal, so that the amount of laser light necessary to obtain a signal with a predetermined intensity can be reduced, and the power consumption of the LDV device can be reduced. Can be planned. When the base angle of the isosceles triangle is smaller than 30 °, the component of the first light beam 5 incident on the right-down reflecting surface in FIG. 3 is reflected vertically, while the component incident on the right-up sloping surface is emitted. Since it is reflected at the angle 3θ, it does not contribute to the interference signal. Similarly, for the second light beam 6, the component incident on the right-upward reflecting surface in FIG. 3 is reflected in the vertical direction, but the component incident on the lower-right reflecting surface is reflected at the exit angle 3θ, and the interference signal Does not contribute to generation.

Further, in the first embodiment, the S / N ratio can be maximized as apparent from Equation 3 by equalizing the light amounts of the first light beam 5 and the second light beam 6. Among the interference signals detected by the light receiving element 10, in Equation 3, the first term is a DC noise component and the second term is an AC signal component, but the AC / DC value is maximized. This is when E _A = E _B , and when the light amounts of the first light beam 5 and the second light beam 6 are equal.

  The above description is based on the condition that the incident angles of the light beams 5 and 6 and the angle of the reflecting surface of the object 9 to be measured are set accurately. However, when an optical system is actually assembled and a reflecting surface is produced on the object 9 to be measured, the incident angle of the light beams 5 and 6 and the angle of the reflecting surface of the object 9 are slightly different from the design values. Arise.

  For example, as shown in FIG. 4A, the incident angle of both light beams 5 and 6 is 2θ, and the shape of the reflecting surface of the DUT 9 is an isosceles triangle having a reflecting surface with a base angle of θ ′ in the cross section. A case will be described. At this time, as shown in FIG. 4A, the two light beams 5 and 6 incident on the reflecting surface do not reflect at right angles to the base of the isosceles triangle, but shift in the direction corresponding to the angle θ ′ of the slope. Reflect. As a result, the reflected light of the first and second light beams 5 and 6 has a portion that overlaps and a portion that does not overlap. FIG. 4A shows the shape of reflected light on a plane including the light receiving surface of the light receiving element 10 on the side opposite to the object 9 to be measured with respect to the light receiving element 10. The broken line is the outline of the reflected light of the first light beam 5, and the solid line is the outline of the reflected light of the second light beam 6. The shaded region 10 s is a region corresponding to the light receiving region of the light receiving element 10. As shown in FIG. 4A, the light receiving element 10 simultaneously receives a portion where both reflected light beams overlap and a portion where the reflected light beams do not overlap, and the light beams in the non-overlapping portions have no light interference. Therefore, in the output signal photoelectrically converted by the light receiving element 10, a DC component is generated by light in a portion where there is no interference, and noise is generated.

  On the other hand, as shown in FIG. 4B, by installing a pinhole 11 at an appropriate position between the DUT 9 and the light receiving element 10, the opposite of the DUT 9 with respect to the light receiving element 10 in FIG. As shown in the figure, only the portion where the reflected light beams overlap can be made incident on the light receiving element 10. As a result, since the DC noise component from the light receiving element 10 can be removed, a signal having a good S / N can be obtained even when there is an error in the incident angle of the first and second light beams 5 and 6 and the inclination angle of the reflecting surface. Can do.

  FIG. 5 is a diagram showing a locus of light rays when the first light beam 5 is reflected by the object 9 to be measured. The first light beam 5 has a beam diameter of 5d and is incident on the reflection surface of the object 9 to be measured. The cross section of the reflection surface of the DUT 9 has a shape in which two isosceles triangles are connected in FIG. Of the two isosceles triangles, with respect to the right isosceles triangle in FIG. 5, a part of the first slope 9a corresponding to the right-downward side and the second slope 9b corresponding to the left-downward side are all. The first light beam 5 is incident on the. Further, with respect to the left isosceles triangle in FIG. 5, the first light beam 5 is incident on a part of the third inclined surface 9 c corresponding to the lower right side, which is an inclined surface connected to the second inclined surface 9 b. Hereinafter, of the first light beam 5, the part of the light beam incident on the first slope 9a is referred to as a first light beam part 5a, and the part of the light beam incident on the third slope 9c is referred to as a second light beam part 5b.

  As shown in FIG. 5, the range in which the first light beam portion 5a is incident on the first inclined surface 9a is between point E and point A, and the second light beam portion 5b is incident on the third inclined surface 9c. The range to be performed is between point B and point F. A point C includes a line extending toward the second light flux portion, and the first light flux portion 5a of the second light flux portion 5b, when the first light flux portion 5a is reflected by the first inclined surface 9a. The intersection with the side boundary. The point D is a point where the second light beam portion 5b reflected at the point B which is the end of the third inclined surface 9c reaches the height of the apex of the isosceles triangle on the reflecting surface.

Of the first light beam 5 incident on the reflecting surface of the object 9 to be measured, the first light beam portion 5a and the third light beam portion 5c reflected by the first inclined surface 9a and the third inclined surface 9c are the bottom surfaces of the isosceles triangle. Reflected in a direction perpendicular to the direction. The first light flux portion 5a and the second light flux portion 5b are reflected light traveling with different phases φ _I and φ _II , respectively. These phase differences φ _I −φ _II correspond to the optical path difference between the first light beam portion 5a and the second light beam portion 5b, and correspond to the distance of CB + BD. This distance d is expressed by the length L and the base angle θ of the base of the isosceles triangle as shown in the following Expression 25.

Therefore, the reflected light of the first light flux part 5a and the second light flux part 5b is expressed as the following Expressions 26 and 27.

Here, A and B are the light intensities of the first light flux part 5a and the second light flux part 5b, ω ₀ is each frequency of the light, and ω _d is the Doppler frequency due to reflection by the moving object 9 to be measured. It is a shift.

ここで、ｎは自然数である。 The first light flux portion 5a and the second light flux portion 5b of the first light flux 5 are strengthened or weakened according to the phase difference due to interference, but the phase difference between the two light fluxes satisfies the condition of the following equation (28). When satisfy | filling, the 1st light beam part 5a and the 2nd light beam part 5b do not weaken each other.

Here, n is a natural number.

  Therefore, when the above equation 28 is satisfied, a stable LDV interference signal can be obtained.

  The first light beam 5 has been described above, but the same applies to the second light beam 6. When A = B and 6π / λ · Ltanθ = π, the two light beams 5 and 6 cancel each other and disappear completely. By avoiding such a state, that is, by setting L and θ that determine the shape of the reflecting surface and λ of the emission wavelength of LD1 so that 6π / λ · Ltanθ = π does not hold, interference The signal never becomes undetectable.

  The LDV as the movement information detecting device in the present embodiment detects the speed of the object 9 to be measured. However, in the signal processing stage, it is possible to easily obtain the displacement amount from the speed information by capturing the time information. it can. Thereby, for example, in an electronic device that is widely used, an encoder that detects the paper feed amount of a printer or a copier can be configured. Particularly, since the LDV interference fringe interval is generally several μm level, a resolution of μm level can be obtained as a displacement meter, and the resolution can be further increased to submicron by signal processing. Furthermore, as shown in FIG. 6, a reflection surface is formed on the object 9 to be measured, in which a rising slope 9 e and a falling slope 9 f are alternately arranged in a ring shape. Thereby, an encoder capable of detecting the rotational speed and position of the DUT 9 with high accuracy can be formed.

(Second Embodiment)
FIG. 7 is a schematic configuration diagram showing a Doppler velocimeter (LDV) as an optical movement information detecting device according to the second embodiment of the present invention. In FIG. 7, only the main components of the optical component and the locus of the light beam are shown, and components that hold the optical component are omitted. In FIG. 7, the same reference numerals as those used in the first embodiment are attached to the same parts as those in the first embodiment, and detailed description thereof is omitted. In addition, although the coordinate axes of the x, y, and z axes are shown in the drawing, this is an example of coordinate axes, and does not limit the orientation of components such as a lens or the polarization direction of laser light.

  In the LDV of the present embodiment, light emitted from the LD 1 in the z-axis direction is converted into circular collimated light by the CL 2 and the diaphragm 3. Then, by the BS 4a as the first light branching element, the light beam is split into a first light beam 5a that travels straight in the z-axis direction and a second light beam 5b that is reflected and travels in the y-axis direction. The first light beam 5a that has passed through the BS 4a is then split into a third light beam 6a that travels straight in the z-axis direction and a fourth light beam 6b that is reflected and travels in the x-axis direction by the BS 4b as the second optical branching element. Is done. The traveling direction of the fourth light beam 6b is converted from the x-axis direction to the z-axis direction by the first mirror 17a.

  The second light beam 5b reflected by the BS 4a is converted into a fifth light beam 7a that travels straight in the y-axis direction and a sixth light beam 7b that is reflected and travels in the z-axis direction by the BS 4c as the third light branching element. Divided. The traveling direction of the fifth light beam 7a that has passed through the BS 4c is converted from the y-axis direction to the z-axis direction by the second mirror 17b. Thereby, the third to sixth light beams 6a, 6b, 7a, 7b are all parallel to the z-axis. The third light beam 6a and the fourth light beam 6b are incident on the first OL 8a, while the fifth light beam 7a and the sixth light beam 7b are incident on the second OL 8b. Each light beam that has passed through both lenses 8a and 8b forms a beam spot at a different point on the measurement object 9 placed at the focal length of the lens. As shown in the enlarged schematic diagram shown in the circular area of the broken line in FIG. 7, on the surface of the object 9 to be measured, protrusions having quadrangular prism-shaped side surfaces are continuously and repeatedly arranged in the xy plane. A reflecting surface having such a shape is formed. Thus, the third light beam 6a and the fourth light beam 6b incident along the plane parallel to the xz plane are incident from the + x direction and the −x direction, respectively, and are directed to the −x direction and the + x direction of the object 9 to be measured. The reflected surface is regularly reflected in the z-axis direction. This specularly reflected light is interfered and becomes an interference signal 12a, which is detected by the first light receiving element 10a.

  Further, the fifth light beam 7a and the sixth light beam 7b incident along the plane parallel to the yz plane are incident from the + y direction and the −y direction, respectively, and are directed to the −y direction and the + y direction of the object 9 to be measured. The reflection surface causes regular reflection in the z-axis direction. This specularly reflected light is interfered and becomes an interference signal 12b, which is detected by the second light receiving element 10b.

  As described above, in the LDV of the second embodiment, the speed in the x-axis direction of the DUT 9 can be obtained from the interference signal 12a detected by the first light receiving element 10a and detected by the second light receiving element 10b. The velocity in the y-axis direction of the DUT 9 can be obtained from the interference signal 12b. Therefore, the two-dimensional movement information of the device under test 9 can be detected.

  FIG. 8 is a schematic configuration diagram of a Doppler velocimeter (LDV) as a modification of the optical movement information detection device of the second embodiment. In FIG. 8, only the main components of the optical component and the locus of the light beam are shown, and the components for holding the optical component are omitted. In FIG. 8, the same components as those of the LDV of FIG. 7 are denoted by the same reference numerals as those of FIG. 7, and detailed description thereof is omitted.

  In this embodiment, the optical system is the same as that of the LDV in FIG. 7, but the reflection surface of the DUT 9 is formed by a plurality of depressions having quadrangular prism side surfaces as schematically shown in FIG. 8. This is different from the LDV of FIG. Two-dimensional movement information can be detected by the reflection surface formed by the plurality of depressions, as in the LDV of FIG.

  In the second embodiment and the modification thereof, the interference signal 12a for detecting movement information in the x-axis direction and the interference signal 12b for detecting movement information in the y-axis direction are collected using, for example, a lens or a diffraction grating. Thus, the first light receiving element 10a and the second light receiving element 10b can be formed on the same semiconductor substrate. Thereby, LDV can be reduced in size and cost can be reduced.

  Further, in each of the above embodiments, the number of components is increased by forming the light receiving element 10 and a signal processing circuit unit (not shown) for processing a signal detected by the light receiving element 10 on the same semiconductor substrate. And the LDV can be reduced in size and cost.

  In addition, although LDV of each said embodiment detects the moving speed of the to-be-measured object 9, it calculates a displacement easily from speed information by taking in time information in the signal processing by a signal processing circuit. Can do. In particular, since the LDV according to the present invention can prevent a signal insensitive state due to dropout, movement information for each pulse can be measured by a pulse count or the like. Therefore, the movement information of the object 9 to be measured can be detected with very high accuracy. Since the LDV interference fringe spacing is several μm, the resolution as a displacement meter can be set to the μm level, and the resolution can be increased to the submicron level by signal processing. Therefore, it is optimal as a high resolution encoder.

  In each of the above embodiments, the optical system has been described by way of example. However, in all the embodiments, the optical system is not limited to the above-described one, and any optical system can be used as long as the same effect can be obtained. Good.

It is a schematic block diagram which shows the optical movement information detection apparatus of 1st Embodiment of this invention. It is a figure which shows an example of the waveform measured in the optical movement information detection apparatus of FIG. It is a figure which shows a reflective surface of a to-be-measured object, and a part of optical system regarding the optical movement information detection apparatus of FIG. It is a figure which shows a mode that the shift | offset | difference produced in the incident angle of the light beam to a reflective surface. It is a figure which shows a mode that the shift | offset | difference produced in the incident angle of the light beam to a reflective surface, when providing a pinhole in an optical system. It is a figure which shows the locus | trajectory of the light ray when a 1st light beam reflects with a to-be-measured object. It is a figure which shows the to-be-measured object in which the reflective surface was arrange | positioned cyclically | annularly. It is a schematic block diagram which shows the optical movement information detection apparatus of 2nd Embodiment of this invention. It is a schematic block diagram which shows the optical movement information detection apparatus of the modification of 2nd Embodiment. It is a figure which shows the optical system of the conventional LDV. It is a figure explaining the positional relationship of a to-be-measured object, an observation point, and a light source. FIG. 10 is an enlarged view showing a portion where two light beams in FIG. 9 overlap. It is a figure which shows an example of the waveform measured in the conventional optical movement information detection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Collimator lens 3 Aperture 4 Beam splitter 5 1st light beam 6 2nd light beam 8 Condensing lens 9 Measured object 10 Light receiving element 11 Pinhole 12 Interference signal

Claims (23)

A semiconductor light emitting device that emits coherent light;
A light branching element that splits the light emitted from the semiconductor light emitting element into a first light flux and a second light flux;
An object to be measured having at least two reflecting surfaces for reflecting the first luminous flux and the second luminous flux in substantially the same direction;
A first optical system for guiding the first and second light fluxes onto the reflecting surface;
A light receiving element that receives interference light obtained by the reflected light of the first light flux and the reflected light of the second light flux;
A second optical system for guiding the reflected light of the first light flux and the reflected light of the second light flux to the light receiving element;
An optical movement information detection apparatus comprising: a signal processing circuit that processes a signal from the light receiving element and calculates a movement speed of the object to be measured. In the optical movement information detection device according to claim 1,
When the incident angle of the first light beam with respect to the direction perpendicular to the moving direction of the object to be measured is 2α, and the incident angle of the second light beam with respect to the direction perpendicular to the moving direction of the object to be measured is 2β,
The optical movement information detection device according to claim 1, wherein the reflection surface of the object to be measured is at least two reflection surfaces each having an angle of α and β with respect to the moving direction of the object to be measured. In the optical movement information detection device according to claim 1,
The optical movement information detection device according to claim 1, wherein the reflection surface of the object to be measured has a shape that periodically changes in a moving direction of the object to be measured. In the optical movement information detection device according to claim 2,
Α and β are substantially the same as each other, and two adjacent reflecting surfaces have shapes corresponding to two equal sides of an isosceles triangle in a cross section in the moving direction of the object to be measured. An optical movement information detecting device. In the optical movement information detection device according to claim 1,
The optical movement information detection apparatus according to claim 1, wherein the reflection surface of the object to be measured has irregularities that undulate in a range smaller than the wavelength of the emitted light of the semiconductor light emitting element. In the optical movement information detection device according to claim 5,
An optical movement information detecting device, wherein the reflection surface of the object to be measured is an optical mirror. In the optical movement information detection device according to claim 4,
The optical system characterized in that the first and second light fluxes have an irradiation dimension on the reflecting surface of the object to be measured that is larger than ½ of the length of the base of the isosceles triangle on the reflecting surface. Movement information detection device. In the optical movement information detection device according to claim 7,
The optical movement information detecting device characterized in that the first and second light fluxes have an irradiation dimension on the reflecting surface of the object to be measured that is substantially equal to the length of the base of the isosceles triangle on the reflecting surface. . In the optical movement information detection device according to claim 4,
An optical movement information detecting device characterized in that a base angle of the isosceles triangle is 30 °. In the optical movement information detection device according to claim 1,
An optical movement information detecting apparatus comprising a pinhole for allowing the reflected light of the first and second light beams to pass between a reflection surface of the object to be measured and the light receiving element. In the optical movement information detection device according to claim 1,
The optical movement information detecting apparatus according to claim 1, wherein the first and second light beams have substantially the same light amount. In the optical movement information detection device according to claim 1,
When the reflected light of the first and second light beams is expressed by the following formulas 1 and 2, the relationship of the following formula 3 is established with respect to the reflected light of the first and second light beams. Movement information detection device.
A · cos ((w ₀ −w _d ) t) (1)
B · cos ((w ₀ −w _d ) t−6π / λ · Ltanθ) (2)
−2 / 3π + 2 (n−1) π <6π / λ · Ltanθ <2 / 3π + 2 (n−1) π (3)
Here, A is the light intensity of the first light beam, B is the light intensity of the second light beam, w ₀ is the frequency of the light from the semiconductor light emitting element, w _d is the Doppler frequency deviation, t is the time, and λ is The wavelength of light from the semiconductor light emitting element, L is ½ the length of the base of the isosceles triangle of the reflecting surface of the object to be measured, θ is the base angle of the isosceles triangle, and n is a natural number. is there. In the optical movement information detection device according to claim 12,
An optical movement information detecting device characterized in that the following expressions 4 and 5 are satisfied with respect to the reflected light of the first and second light beams.
A ≠ B (4)
3L / λ · tan θ <(2m−1) (5)
Here, m is a natural number.   An encoder comprising the optical movement information detection device according to claim 1. The encoder according to claim 14,
The encoder is characterized in that the reflecting surface is arranged in an annular shape on the object to be measured. In the optical movement information detection device according to claim 1,
An optical movement information detecting apparatus, wherein the object to be measured is formed of a Si wafer, and a reflection surface of the object to be measured is formed by anisotropic etching. A semiconductor light emitting device that emits coherent light;
A first light branching element that splits light emitted from the semiconductor light emitting element into a first light flux and a second light flux;
A second optical branching element that splits the first luminous flux into third and fourth luminous fluxes;
A third light branching element that splits the second light flux into fifth and sixth light fluxes;
An object to be measured having at least four reflecting surfaces for reflecting the third and fourth light beams in substantially the same direction and reflecting the fifth and sixth light beams in substantially the same direction;
A first optical system for guiding the third and fourth light fluxes to a first position on the reflecting surface;
A second optical system for guiding the fifth and sixth light beams to a second position on the reflecting surface;
A first light receiving element that receives interference light obtained by the reflected light of the third light beam and the reflected light of the fourth light beam;
A second light receiving element that receives interference light obtained by the reflected light of the fifth light beam and the reflected light of the sixth light beam;
A third optical system for guiding the reflected light of the third light flux and the reflected light of the fourth light flux to the first light receiving element;
A fourth optical system for guiding the reflected light of the fifth light flux and the reflected light of the sixth light flux to the second light receiving element;
An optical movement information detection apparatus comprising: a signal processing circuit that processes signals from the first and second light receiving elements to calculate a movement speed of the object to be measured. The optical movement information detection device according to claim 17,
2. The optical movement information detecting apparatus according to claim 1, wherein the reflection surface of the object to be measured has a shape in which protrusions having quadrangular prism-shaped side surfaces are periodically arranged. The optical movement information detection device according to claim 17,
The optical movement information detection apparatus according to claim 1, wherein the reflection surface of the object to be measured has a shape in which depressions having a quadrangular prism-shaped side surface are periodically arranged. The optical movement information detection device according to claim 17,
The optical movement information detecting apparatus, wherein the first and second light receiving elements are formed on the same substrate. In the optical movement information detection device according to claim 1,
The optical movement information detecting apparatus, wherein the light receiving element and the signal processing circuit are formed on the same substrate.   An electronic apparatus comprising the optical movement information detection device according to claim 1.   An electronic device comprising the encoder according to claim 14.

Images