JP2001264014A - Optical sensor and three-dimensional shape measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized, low-priced optical sensor, capable of measuring the distance to an object with high accuracy in a short time, and to provide a three-dimensional shape measuring instrument. SOLUTION: When intensity-modulated light enters the optical sensor 9, a photoelectric transducing part PD of each pixel 90 transduces photoelectrically the incoming light into a signal current, a voltage conversion part Cj-MR converts the signal current into a voltage signal which is opposite in polarity and inversely proportional to the storage of charge, and a smoothing circuit MSF-C-R smooths the voltage signal. Since the current-voltage conversion has the effect of doubling the amplitude of the current from the transduction part PD, highly accurate detection can be performed, even if the amplitude of the current from the transduction part PD is minute. Each read-out means 91-92 reads out the voltage signal smoothed by the smoothing circuit of each of a plurality of signal generating means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical sensor and a three-dimensional shape measuring device for measuring a distance to a target object, and particularly to a small and inexpensive, short-time and highly accurate distance measuring device for a target object. The present invention relates to an optical sensor and a three-dimensional shape measurement device capable of performing the measurement.

[0002]

2. Description of the Related Art As a method for measuring a three-dimensional shape, two methods, a passive method and an active method, have been proposed. The passive method is a method of measuring a shape without radiating energy to a target object, and the active method is a method of measuring a shape by radiating some energy to a target object and detecting its reflection.

In the passive method, there is a stereo method as one of the methods for measuring the distance of a plurality of points to a target object. The stereo method is a method in which two cameras are installed at a certain interval, and the distance to a target object is measured by a trigonometric method from the parallax of two obtained images. This method has the advantage that it can measure the distance to a distant place if it can be captured as an image, but it has a serious problem that it is not possible to perform three-dimensional measurement of the entire surface with a smooth surface without patterns There is a point. In addition, since the optical axes of the two cameras cannot be matched in principle, there is a disadvantage that an area (occlusion) where the distance cannot be measured occurs.

In the active method, there is a light cutting method as one of the methods for measuring the distance of a plurality of points to a target object. This light cutting method is a method of irradiating a target object with slit light at a certain angle, and measuring the distance to the target object by triangulation from an image taken from another angle. This method has the advantage that it can be realized with a relatively simple configuration, but the slit light has to be scanned in small angle units, and an image is taken each time, so that the measurement time becomes longer. There is. In order to solve this problem, there is a spatial coding method as a method applying the light sectioning method. This spatial coding method measures the distance with a small number of projections by coding the pattern of the projection light instead of irradiating the slit light many times, but the number of samples in the horizontal direction is n. Then, since it is necessary to perform log ₂ n times (n = 512 points and nine times) of imaging, there is a problem that the measurement time becomes long. Also,
Area where the distance cannot be measured because the optical axis of the projector and the imager cannot be matched in principle (occlusion)
However, there is a drawback that the problem occurs.

[0005] In the active method, as one of the methods capable of measuring the distance of a plurality of points by one imaging, a phase distribution measuring method of irradiating an intensity-modulated light to a target object and measuring a phase distribution of a reflected light thereof. There is. As a conventional phase distribution measurement method, for example, reference 1 “SPIE Vol. 2588, 1995,
Papers on pages 126-134 (An new active 3
D-Vision system basedon rf-modulation interferomet
ry light) "and Patent No. 2690673 and SPIE Vol. 2748, 1996, pp. 47-59," The Emergi.
ng Versatility ofa Scannless Range Imager ".

FIG. 5 shows a conventional three-dimensional shape measuring apparatus disclosed in Document 1. This three-dimensional shape measuring apparatus 100
A modulation / demodulation signal generator 104 for performing intensity modulation on light emitted from a light source 101A to a plane modulator 103 using a crystal such as a Pockels cell via a condenser lens 102;
A projection lens 106 for irradiating the target object 6 with the intensity-modulated light 105a in a plane, and an imaging lens 1 reflected by the target object 6
07, a modulation / demodulation signal generator 104 for demodulating the intensity of the reflected light 105b incident on a plane demodulator 108 using a crystal such as a Pockels cell, and a CCD camera 109 for imaging the optical signal subjected to the intensity demodulation. And In such a configuration, the light emitted from the light source 101A is incident on the plane modulator 103 by the condenser lens 102 and is subjected to intensity modulation based on the signal of the modulation / demodulation signal generator 104. The intensity-modulated light 105a is projected onto the target object 6 by the projection lens 106.
The reflected light 105b from the target object 6 is
, And after being subjected to intensity demodulation based on the signal of the modulation / demodulation signal generator 104,
An image is formed on the camera 109. The grayscale image captured by the CCD camera 109 includes phase information resulting from the distance to the target object 6. By processing the grayscale image by the computer 110, the distance data of the target object 6 can be obtained by one imaging.

FIG. 6 shows a conventional three-dimensional shape measuring apparatus described in Japanese Patent No. 2690673. The difference from FIG. 5 is that the semiconductor laser 101B is used as a light source, the intensity modulation is performed directly by the semiconductor laser 101B without using a modulator using a crystal such as a Pockels cell, The third point is that demodulation is performed by the image intensifier 111 without using a demodulator using a crystal. Modulation / demodulation signal generator 10
The light subjected to intensity modulation based on the signal of No. 4 is emitted from the semiconductor laser 101B, and then is projected onto the target object 6 by the projection lens 106. The reflected light 105b from the target object 6 is imaged by the imaging lens 107 on the image intensifier 111. The signal from the modulation / demodulation signal generator 104 is converted into a high-voltage signal by the high-voltage drive circuit 112 and input to the gain controller terminal of the image intensifier 111, and the reflected light whose intensity is demodulated is imaged by the CCD camera 109. . CCD
The grayscale image captured by the camera 109 includes phase information resulting from the distance to the target object 6. By processing the grayscale image by the computer 110, the distance data of the target object 6 can be obtained by one imaging.

[0008]

However, according to the conventional three-dimensional shape measuring apparatus shown in FIG.
Since a modulator / demodulator using a crystal such as a Pockels cell is used for the plane demodulator 108, there is a disadvantage that the apparatus becomes very expensive. Since the aperture of the modulator / demodulator using this crystal is as small as about several millimeters, the light radiated from the light source 101A and the light reflected by the target object 6 are adjusted to the aperture by the condenser lens 102,
The light must be condensed using 107, and there is a disadvantage that the device becomes large.

Further, the conventional three-dimensional shape measuring apparatus shown in FIG. 6 has a disadvantage that the apparatus becomes very expensive because the image intensifier 111 is used. Also, this image intensifier 1
In order to drive 11, it is necessary to intensity-modulate a high voltage signal of several hundred volts, so that there is a disadvantage that the drive circuit becomes complicated. Further, since the image intensifier 111 is larger than the CCD camera 109, there is a drawback that the entire apparatus becomes large.

On the other hand, in a sensor capable of detecting light, a two-dimensional M which is a typical two-dimensional sensor for miniaturization.
It is conceivable to use an OS image sensor or a two-dimensional CCD image sensor, but these image sensors are
Since it has only the function of integrating the signal charge for the accumulation time, there is no demodulation function necessary for distance measurement.
It cannot be used as an optical sensor of a three-dimensional shape measuring device.

Accordingly, it is an object of the present invention to provide an optical sensor and a three-dimensional shape measuring apparatus which are small and inexpensive, and can measure the distance to a target object in a short time and with high accuracy.

[0012]

In order to achieve the above object, the present invention provides a photoelectric conversion unit for photoelectrically converting incident light into a signal current, and a voltage conversion unit for converting the signal current into a voltage signal in a non-linear manner. A plurality of signal generators arranged two-dimensionally having a smoothing circuit for smoothing the voltage signal, and reading out the voltage signals smoothed by the smoothing circuit of the plurality of signal generators Means for providing an optical sensor. According to the above configuration, since the capacitor whose junction capacitance decreases as the voltage between the terminals of the voltage converter increases, the amplitude of the current from the photoelectric converter is doubled when the voltage is converted. Therefore, even if the amplitude of the current from the photoelectric conversion unit is very small, highly accurate detection is possible.

[0013] In order to achieve the above object, the present invention provides a light emitting means for emitting an intensity-modulated light intensity-modulated at a predetermined frequency toward an object, and a light-emitting means for reflecting light from the object and the intensity-modulated light. A three-dimensional shape measuring apparatus comprising: an optical sensor that receives a synthesized light and outputs a detection signal; and an image processing unit that calculates a distance to the object based on the detection signal to form a distance image. The sensor has a photoelectric conversion unit that photoelectrically converts the intensity-modulated light into a signal current, a voltage conversion unit that converts the signal current into a voltage signal in a non-linear manner, and a smoothing circuit that smoothes the voltage signal. A three-dimensional shape measuring apparatus comprising: a plurality of signal generating means arranged two-dimensionally; and a reading means for reading out the voltage signal smoothed by the smoothing circuit of the plurality of signal generating means. To Subjected to.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a three-dimensional shape measuring apparatus according to a first embodiment of the present invention. The apparatus 1 includes a modulation signal generator 2 for generating a modulation signal, a semiconductor laser 3 for emitting illumination light 4a composed of laser light based on the modulation signal from the modulation signal generator 2, and an illumination from the semiconductor laser 3. A projection lens 5 for irradiating light 4a toward a target object 6, an imaging lens 7 for forming an object light 4b reflected by the target object 6 on an optical sensor 9 via an optical filter 8, and a semiconductor laser 3. Of the illumination light 4a is transmitted, and the rest is reflected as the reference light 4c.
, A first liquid crystal shutter 11 </ b> A disposed between the target object 6 and the optical filter 8, the half mirror 10 and the optical filter 8.
And a distance calculator 14 that two-dimensionally calculates distance data on the surface shape of the target object 6 based on the output signal of the optical sensor 9.
And a computer 15 that includes a CPU, a ROM, a RAM, and the like, controls each unit of the device 1, and displays a calculation result of the distance calculation unit 14.

The semiconductor laser 3 emits illumination light 4 a composed of laser light intensity-modulated based on the modulation signal from the modulation signal generator 2 and intensity modulation based on a steady signal from the modulation signal generator 2. It emits illumination light 4a consisting of unprocessed stationary light. This stationary light is
It has a light intensity that matches the average intensity of the intensity-modulated illumination light 4a.

First and second liquid crystal shutters 11A, 11A
1B, for example, can control the transmittance in the range of 0 to 100% by controlling the applied voltage for each pixel. Note that the shutters 11A and 11B do not have to be provided for each pixel, and may have the same transmittance for all pixels. Alternatively, a mechanical shutter may be used as the shutter to shut off all at once.

FIG. 2 shows the optical sensor 9. This optical sensor 9 has a plurality of (six in the figure) pixels 90 (90-11, 90-12, 90-13,..., 90) arranged two-dimensionally.
-21, 90-22, 90-23,...) And a vertical selection transistor 91 (MSL11, MSL11) provided for each pixel 90.
SL12, MSL13, ..., MSL21, MSL22, MS
L23,...) And horizontal selection transistors 92 (MSL1, MSL2, MSL3,...) Provided for each row.
And a vertical shift register 93 that outputs a drive pulse to each vertical selection transistor 91 via a horizontal signal line 93a.
And a horizontal shift register 94 that outputs a drive pulse to each horizontal selection transistor 92 via a vertical signal line 94a.
And a video amplifier 97 that is grounded via a load resistor 96 and amplifies and outputs a voltage signal read from each pixel to the common line 95.

The pixel 90 has a photodiode PD for photoelectrically converting incident light into a signal current corresponding to the light intensity, and one end connected to the photodiode PD and the other end grounded and arranged in a reverse bias. A varactor diode Cj functioning as a non-linear capacitor at the time of reverse bias; a P-type reset MOS transistor MR having a drain connected to the photodiode PD to accumulate charges in the varactor diode Cj; An n-type MOS transistor MSF connected to Vdd and having a gate connected to the photodiode PD to amplify the output voltage of the varactor diode Cj;
Connected in parallel to the source of the MOS transistor MSF,
A capacitor C and a resistor R forming a smoothing circuit for smoothing the voltage signal of the MOS transistor MSF are provided.

FIGS. 3A and 3B are diagrams for explaining the operation of one pixel 90. FIG. 3A shows the configuration of one pixel 90, and FIG. 3B shows the current (photodiode) of the photodiode PD. (C) shows the output voltage V1 of the varactor diode Cj, and (d) shows the voltage signal V2 smoothed by the smoothing circuit. The varactor diode Cj is an element utilizing the characteristic that the width of the depletion layer in the PN junction expands as the reverse voltage increases, and as a result, the junction capacitance decreases. I do. Therefore, there is an effect that the amplitude of the photodiode current Ipd is doubled when the voltage is converted, and high-precision detection is possible even if the amplitude of the photodiode current Ipd is minute. The capacitance C of the varactor diode Cj
_j is represented by the following equation (1). C _j = C _o (1 + V _r / Φ _o ) ^-r (1) where C _o is the junction capacitance when V _r = 0, V _r is the reverse bias voltage, Φ _o is the diffusion potential, and r is This is the impurity concentration near the junction. For example, the impurity concentration r near the junction of the varactor diode Cj is set to −3 to enhance the non-linearity so that the photodiode current Ipd can be detected even with a small amplitude.

Gate voltage V of MOS transistor MSF
1 becomes the reverse bias voltage _Vr . As an operation, first, the reset MOS transistor MR is turned on, thereby accumulating charges in the varactor diode Cj.
Then, the output voltage V1 of the varactor diode Cj is
After making the threshold voltage Vth1 of the S transistor MSF equal, the reset MOS transistor MR is turned off. Next, charges are stored in the varactor diode Cj by the photodiode current Ipd. The output voltage V1 of the varactor diode Cj at this time gradually increases with time, that is, changes according to the following equation (2). V1 = Vth1 + Δt × Ipd / C _j (2) At this time, the capacitance C _j of the varactor diode Cj increases as the output voltage V1 (= reverse bias voltage V _r ) increases and the expression (1)
, The output voltage V1 further increases according to equation (2). Therefore, the amount of change in signal strength appears larger than when a linear capacitor is used.

Therefore, when the photodiode PD is irradiated with the intensity modulated light superimposed on the DC offset light, the photodiode PD generates a current waveform corresponding to the waveform of the intensity modulated light. FIG. 6B shows the waveform of the photodiode current Ipd when the photodiode PD is separately irradiated with the DC offset light and two intensity-modulated lights having different amplitude intensities with respect to the DC offset component. Is shown. The solid line indicates the DC offset component, and the dotted line indicates the intensity modulated light. The voltage between the terminals of the varactor diode Cj is set to MO by the reset MOS transistor MR.
After the resetting to the threshold voltage Vth1 of the S transistor MSF, when the photodiode current Ipd occurs, the photodiode current Ipd is amplified by the varactor diode Cj according to the above equations (1) and (2). It is converted to a signal V1.

The output voltage of the varactor diode Cj (= M
The waveform of V1, which is the gate voltage of the OS transistor MSF, rises nonlinearly and increases as shown in FIG.
A pulsating waveform is shown upward in each cycle with respect to the offset, and the threshold voltage Vth2 (V
th2> Vth1). The output voltage V1 of the varactor diode Cj is amplified by being input to the gate of the MOS transistor MSF, and the amplified signal is amplified by a smoothing circuit of a capacitor C and a resistor R as shown in FIG. Smoothed. Smoothed voltage waveform V2
Indicates a voltage value which is lower than the output voltage V1 of the varactor diode Cj by the threshold voltage Vth1 of the MOS transistor MSF functioning as a source follower, and is also current amplified. Finally, the smoothed signal is sent to the output terminal 97a at a predetermined timing by the vertical selection transistor 91. The difference between the DC offset and the smoothed voltage waveform V2 shown in FIG.
It corresponds to the amplitude of pd and thus the amplitude of the intensity modulated light.

FIGS. 4A to 4D show waveform profiles of intensity-modulated light for explaining the operation of the three-dimensional shape measuring apparatus 1 according to the first embodiment. (1) Detection of object light 4b composed of stationary light Here, the object light 4b composed of stationary light is detected. That is, the computer 15 controls the current signal mixer of the modulation signal generator 2 to output only the DC signal from the DC current source to the semiconductor laser 3. The semiconductor laser 3 emits illumination light 4a composed of stationary light. Computer 1
Reference numeral 5 denotes a state where the first liquid crystal shutter 11A is opened and the second liquid crystal shutter 11B is closed according to a control signal to the first and second liquid crystal shutters 11A and 11B. A part of the illumination light 4a from the semiconductor laser 3 passes through the half mirror 10 and is projected on the target object 6 by the projection lens 5, and the object light 4b reflected by the target object 6 is optically reflected by the imaging lens 7. An image is formed on the optical sensor 9 via the filter 8.

The object light 4b from the target object 6 is photoelectrically converted into a current signal by the photodiode PD, the current signal is converted into a voltage signal by the varactor diode Cj, and the voltage signal is amplified by the MOS transistor MSF. And the voltage signal is the capacitor C
And smoothed by the smoothing circuit of the resistor R and stored in the capacitor C as a charge signal. The charge signal stored in the capacitor C is read out in the same manner as in a normal MOS image sensor. That is, the vertical shift register 93
And vertical drive transistors 91 (MSL11, MSL12, M
SL13, ..., MSL21, MSL22, MSL23, ...
.) And the horizontal selection transistor 92 (MSL1, MSL)
L2, MSL3,...) Are sequentially turned on, and the charge signal smoothed by the smoothing circuit of each pixel 90 is read out to the common line 95 as a voltage signal.

The read voltage signal is supplied to a video amplifier 9
7 and amplified by the distance calculation unit 14 from the output terminal 97a.
Sent to The read output signal is output to a distance calculation unit 14.
Is stored for each pixel 90. The value of the output signal stored for each pixel 90 is the value of the object light 4 shown in FIG.
b corresponding to the amplitude (C _n · aE), and its values are represented by A11 and A1.
2, ... The pixel 90 operates at a high frequency of 30 to 100 MHz, which is the modulation frequency of the intensity-modulated light, whereas the vertical selection transistor 91 (MS
L11, MSL12, MSL13, ..., MSL21, MSL
22, MSL23,...) And horizontal selection transistor 9
2 (MSL1, MSL2, MSL3,...) Can operate at a low frequency such as a video rate.

(2) Detection of reference light 4c composed of stationary light Here, the reference light 4c composed of stationary light is detected. That is, the computer 15 controls the current signal mixer of the modulation signal generator 2 to output only the DC signal from the DC current source to the semiconductor laser 3. The semiconductor laser 3 emits illumination light 4a composed of stationary light. Computer 1
Reference numeral 5 indicates that the first liquid crystal shutter 11A is closed and the second liquid crystal shutter 11B is opened according to control signals to the first and second liquid crystal shutters 11A and 11B. A part of the illumination light 4 a from the semiconductor laser 3 is reflected by the half mirror 10 and is irradiated on the optical sensor 9 via the optical filter 8. The reference light 4c is photoelectrically converted by the photodiode PD into a signal current, and the signal current is read out as a voltage signal in the same manner as when the object light 4b composed of the stationary light is detected. The value of the output signal stored for each pixel 90 in the distance calculation unit 14 corresponds to the amplitude (bE) of the reference light 4c shown in FIG.
...

(3) Detection of Combined Light of Illumination Light 4a and Reference Light 4c Consisting of Intensity Modulated Light Here, the combined light of illumination light 4a and reference light 4c composed of intensity modulated light is detected. That is, the computer 15
Controls the current signal mixer of the modulation signal generator 2 to combine the modulation current from the modulation current source with the DC current from the DC current source and output the combined laser current to the semiconductor laser 3. Semiconductor laser 3
Emits illumination light 4a composed of intensity-modulated light as shown in FIG. Further, the computer 15 opens the first and second liquid crystal shutters 11A according to control signals to the first and second liquid crystal shutters 11A and 11B. Part of the illumination light 4a from the semiconductor laser 3 is transmitted through the half mirror 10, and the rest is reflected by the half mirror 10. The illumination light 4a transmitted through the half mirror 10 is projected onto the target object 6 and reflected by the target object 6 in FIG.
Is formed on the optical sensor 9 by the imaging lens 7 via the optical filter 8. On the other hand, the reference light 4c as shown in FIG. 4C reflected by the half mirror 10 is projected on the optical sensor 9 via the optical filter 8. Accordingly, a combined light, as shown in FIG. 4D, composed of the object light 4b and the reference light 4c is incident on the optical sensor 9. The combined light incident on one pixel 90 is converted into a signal current by the photodiode PD, and the signal current is read out as a voltage signal through the video amplifier 97 as described above. The read output signal is stored in the distance calculation unit 14 for each pixel 90. These pixels 9
The output signal values stored for each 0 are represented by P1-11, P1-12,.
And

(4) Calculation by the Distance Calculation Unit 14 The calculation by the distance calculation unit 14 will be described in detail below. Assuming that the angular frequency of the intensity modulation of the illumination light 4a from the semiconductor laser 3 is ω and the maximum and minimum values of the modulation are 2E and 0, FIG. 4A emitted from the semiconductor laser 3
Light intensity I _o of the illumination light 4a, as shown in the following formula (3)
It is represented as I _o = E (sin ωt + 1) (3) If the distance to the target object 6 is 0 to 2.5 m, the required modulation frequency is 30 MHz. Half mirror 1
Assuming that a light transmittance of 0 is a and a reflection coefficient at a certain point on the target object 6 is Cn, the point is incident on a point n imaged on the optical sensor 9 as shown in FIG. The intensity of the object light 4b is represented by the following equation (4). A _n = C _n · aE {sin (ωt + φ _n ) +1} (4) where φ _n is a phase delay caused by a flight distance of the light incident on the optical sensor 9 from the light source, and Laser 3 ~
Assuming that the distance between the target object 6) + (the target object 6 and the optical sensor 9) is L, then φ _n = ωL / C. Here, C represents the speed of light.

On the other hand, assuming that the reflectance of the half mirror 10 is b and the optical path length from the semiconductor laser 3 via the half mirror 10 to the optical sensor 9 is sufficiently smaller than the wavelength of the modulated wave, the optical sensor Reference light 4c on point n of 9
Is expressed as in the following equation (5). B _n = bE (sinωt + 1) (5) The intensity Pn of the combined light at the point n on the optical sensor 9 is obtained by calculating the expression (4) for obtaining the light intensity of the object light 4b and the light intensity of the reference light 4c. Expression (6) is obtained by adding the expression (5) to be obtained. _{P n = A n + B n} = C n · aE {sin (ωt + φ n) +1} + bE (sinωt + 1) = C n · aE {sinωtcosφ n + cosωtsinφ n +1} + bE (sinωt + 1) = (C n · a + b) E + (C _{n · aEcosφ n + bE) sinωt} + C n · aEsinφ n cosωt = (C n · a + b) E + √ {(C n · aEcosφ n + bE) 2 + (C n · aEsinφ n) 2} · sin (ωt + θ) = ( _{C n · a + b) E} + √ {(C n · aE) 2 + (bE) 2 + 2C n · abE 2 cosφ n} · sin (ωt + θ) ··· (6) _{However, tanθ = C n · aEsinφ n} / (C _n · aEcosφ _n + bE)

[0030] Equation (6) is, DC components (Cna + b) E, and the high frequency component _{√ {(C n · aE)} 2 + (bE) 2 + 2C n · abE 2
cos φ _n ｝ · sin (ωt + θ). When the peak value of P _n and P _p, P _p is expressed by the following equation (7). P _p = C _n · aE + bE + {(C _n · aE) ² + (bE) ² + 2C _n · abE ² cosφ _n } (7)

[0031] Thus the peak value P _p and the object beam 4b of the combined light
If it is possible to detect the amplitude C _n · aE, the reference beam amplitude bE, it is possible to calculate the phase delay phi _n with distance information. A signal corresponding to the amplitude of the object beam 4b (A11, A
12) is A, and among signals (B11, B12, ...) corresponding to the amplitude of the reference light 4c and peak signals (Pp-11, Pp-12, ...) of the combined light. When a signal corresponding to the pixel 90 corresponding to the signals a and B and P _p, equation (7) can be expressed as the following equation (8). P _p = A + B + √ (A ² + B ² + 2ABcosφ _n ) (8) For this reason, the predetermined values stored in the distance calculation unit 14 are substituted for P _p , A, and B, and the distance calculation unit 14 φ _n
Is calculated, and a distance image is obtained according to φ _n = ωl / C (where C is the speed of light). By performing this for all pixels 90, a distance image at all pixels 90 can be obtained.

According to the first embodiment, the following effects can be obtained. (A) The peak value of the signal current obtained by photoelectrically converting the intensity-modulated light is converted into a voltage signal as if apparently amplified, and the voltage signal was amplified and smoothed. If the smoothed voltage signal is read once, a signal corresponding to the amplitude value of the intensity-modulated light can be obtained, so that the speed of reading the image can be increased and the distance to the object 6 can be measured with high accuracy. Becomes possible. (B) A varactor diode that enables a small, inexpensive, and high-speed operation of an optical sensor without the need for expensive means such as a crystal light intensity demodulator or an image intensity fire that has been conventionally used as a means for demodulating light. Since it is constituted by Cj, it is possible to measure the distance to the object 6 in a short time at a small size and at low cost. (C) A luminance image can be obtained from the signal obtained by the operation of detecting the object light 4b composed of the stationary light. Further, the peak value of the output of the optical sensor when the intensity modulated light is used may be used as the luminance image. Accordingly, both the distance image and the luminance image can be obtained by one optical sensor 9 and the two images have one-to-one correspondence with the pixels 90, so that the subsequent image processing can be easily executed. it can.

Next, a second embodiment of the present invention will be described. This second embodiment is different from the first embodiment in that
Only the distance calculation unit 14 is different, and the other configuration is the same as that of the first embodiment. By transforming equation (7), the following equation (9) is obtained. _{P p - (C n · aE} + bE) = √ {(C n · aE) 2 + (bE) 2 + 2C n · abE 2 cosφ n} ··· (9) the left side of _{P p - (C n · aE} + bE) is 4D, it is an amplitude component of the combined light. Therefore, even when detecting the amplitude component instead of the peak value P _p of the combined light Motomari phase difference phi _n of the reference beam 4c and the object beam 4b, the distance can be calculated. The distance calculator 14 calculates the amplitude component of the combined light based on the equation (9). That is, the peak value of the combined light is obtained in the same manner as in the procedure of the first embodiment. next,
The object light 4 is irradiated with the stationary light, the object light 4b and the reference light 4c are simultaneously irradiated on the photodiode PD, and the intensity of the combined light (DC offset light) of the stationary light is obtained. Note that this value may be obtained by individually obtaining the DC offset components of the object light 4b and the reference light 4c, and adding the two. The difference between the peak value of the combined light and the intensity value of the DC offset light, that is, the amplitude component of the combined light is calculated. The amplitude component of the combined light obtained as described above and the components corresponding to the amplitudes of the reference light 4c and the object light 4b obtained in the first embodiment are substituted into Expression (9), and the phase difference φ _n is calculated by the distance calculation unit. Calculate at 14. According to the second embodiment, effects similar to those of the first embodiment can be obtained.

The present invention is not limited to the above-described embodiment, but can be variously modified. For example, in the above-described embodiment, a semiconductor laser is used as a light source. However, since a coherent light is not required in principle, a general light source such as a xenon lamp or a strobe can be used.

[0035]

As described above, according to the present invention, since the voltage converter is configured so that the junction capacitance decreases as the reverse voltage increases, the amplitude of the current from the photoelectric converter can be reduced. This has the effect of doubling the current, and enables high-precision detection even if the amplitude of the current from the photoelectric conversion unit is very small. Therefore, the distance to the target object can be measured with high accuracy. In addition, since the signal generating means can be constituted by a varactor diode that is small and inexpensive and can operate at high speed, it is possible to measure the distance to the target object in a short time at a small size and at low cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a three-dimensional shape measuring apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an optical sensor according to the first embodiment.

FIG. 3 is a diagram schematically showing charge transfer from charge generation of the optical sensor according to the first embodiment.

FIG. 4 is a waveform profile of intensity-modulated light according to the first embodiment.

FIG. 5 is a configuration diagram of a conventional three-dimensional shape measuring apparatus.

FIG. 6 is another configuration diagram of a conventional three-dimensional shape measuring apparatus.

[Explanation of symbols]

 Reference Signs List 1 3D shape measuring device 2 Modulation signal generator 3 Semiconductor laser 4a Illumination light 4b Object light 4c Reference light 5 Projection lens 6 Target object 7 Imaging lens 8 Optical filter 9 Optical sensor 10 Half mirror 11A First liquid crystal shutter 11B First 2 liquid crystal shutter 14 distance calculation unit 15 computer 90 pixel 91 vertical selection transistor 92 horizontal selection transistor 93 vertical shift register 93a horizontal signal line 94 horizontal shift register 94a vertical signal line 95 common line 96 load resistance 97 video amplifier PD photodiode Cj varactor Diode MR Reset MOS transistor MSF MOS transistor C Capacitor R Resistance

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 31/10 H01L 27/14 A 5J084 // H04N 5/335 31/10 G F-term (Reference) 2F065 AA06 AA53 BB05 DD06 FF01 GG03 GG06 GG08 JJ03 JJ18 JJ26 LL21 LL30 LL53 NN08 NN13 QQ12 QQ24 QQ31 QQ33 SS02 SS13 2F112 AA09 BA05 BA10 CA08 DA28 GA10 4M118 AA02 AB01 CA02 FA06 FA34 EX03 G03 C02X00 HX40 5F049 MA01 NB07 RA02 RA06 UA20 5J084 AA05 AA13 AB16 AD05 BA04 BA36 BB01 BB20 BB24 BB35 CA07 CA23 CA31 DA01 EA04 EA05 EA31 FA03

Claims (6)

[Claims] A photoelectric conversion unit configured to photoelectrically convert incident light into a signal current; a voltage conversion unit configured to nonlinearly convert the signal current into a voltage signal; and a smoothing circuit configured to smooth the voltage signal. An optical sensor comprising: a plurality of two-dimensionally arranged signal generating means; and a reading means for reading out the voltage signal smoothed by the smoothing circuit of the plurality of signal generating means. 2. The varactor diode, wherein one end of the voltage conversion unit is connected to the photoelectric conversion unit and the other end is grounded and arranged in a reverse bias, and functions as a non-linear capacitor at the time of the reverse bias. The optical sensor according to claim 1, wherein the optical sensor is provided. 3. The varactor diode, wherein one end of the voltage conversion unit is connected to the photoelectric conversion unit, and the other end is grounded and arranged in a reverse bias. The varactor diode functions as a non-linear capacitor at the time of reverse bias. A reset MOS transistor having a drain connected to the photoelectric conversion unit and accumulating charge in the varactor diode, wherein the smoothing circuit has a drain connected to a power supply, a gate connected to the photoelectric conversion unit, A MOS transistor for amplifying an output voltage of a varactor diode;
The optical sensor according to claim 1, further comprising a capacitor and a resistor connected in parallel to a source of the transistor and configured to smooth a voltage signal of the MOS transistor. 4. A light emitting means for emitting an intensity-modulated light having been intensity-modulated at a predetermined frequency toward an object, and receiving a combined light of the reflected light from the object and the intensity-modulated light to generate a detection signal. In a three-dimensional shape measuring apparatus having an optical sensor for outputting and an image processing unit for calculating a distance to the object based on the detection signal to form a distance image, the optical sensor outputs the intensity-modulated light as a signal. A plurality of two-dimensionally arranged photoelectric conversion units that photoelectrically convert the current into a current, a voltage conversion unit that non-linearly converts the signal current into a voltage signal, and a smoothing circuit that smoothes the voltage signal A three-dimensional shape measuring apparatus, comprising: signal generating means; and reading means for reading out the voltage signal smoothed by the smoothing circuit of the plurality of signal generating means. 5. The light emitting means selectively emits the intensity modulated light and the stationary light, and the image processing means reads the voltage read by the reading means based on the emission of the intensity modulated light. The three-dimensional shape measuring apparatus according to claim 4, wherein the distance is calculated from a signal and the voltage signal read by the reading unit based on emission of the stationary light. 6. The image processing apparatus according to claim 4, wherein the image processing unit forms a luminance image from the voltage signal read by the reading unit based on the emission of the stationary light. 3D shape measuring device.