JPS60100010A - Photoelectric converter - Google Patents

Abstract

PURPOSE:To realize a photoelectric conversion of superior performance, by forming a circulation loop of two charge storage units for one light-receiving unit. CONSTITUTION:An optical charge generated in photosensitive picture element units S1-SN is stored in a charge storage unit ST1. When phiSH1 is of high level, the charge stored in the storage unit ST1 is transmitted temporarily to a charge transmission unit GA, and when phiSH1 is inverted to be of low level, a charge Q is stored in a storage unit ST2. When the charges stored in the storage units ST1 and ST2 are transmitted temporarily to charge transmission units GA and GB and phiSH1 is inverted to be of low level, a charge Q of an information on a surrounding light is stored in the storage unit ST2, while a charge Q on an information at the time of projection of a light is inputted to ST1. These operations are repeated sequentially, and the optical informations obtained when the light is projected and those obtained when no light is projected are added up in circulation. Thereby true projection signals of all the photosensitive picture elements can be obtained, and thus a distance to a remote object can be detected with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention projects light toward a subject, receives reflected light from the subject with a light receiver, and detects the distance to a distant subject based on a signal from the light receiver. The present invention relates to an accumulation-type photoelectric conversion device that is effective when doing so.

As disclosed in Japanese Patent Application Laid-open No. 154382/1982, a conventional photoelectric conversion device has two separate charge accumulation sections for one light receiving section, and when light is emitted to the two charge accumulation sections, The signal obtained from the reflected light from the subject when the light is not emitted and the signal obtained from the reflected light from the subject when the light is not emitted (ambient light signal) are accumulated separately, and the difference between the signals of each charge storage section is calculated. The light emitting signal from K-Yoshima was detected, and the distance to the subject was detected using the signal.

However, in this method, the two charge storage sections are configured independently, so if the detection sensitivities of the two charge storage sections differ, it is not possible to accurately remove ambient light information, and the detection ability tends to decrease. was there.

An object of the present invention is to provide a photoelectric conversion device with good performance. A feature of the photoelectric conversion device for achieving the object of the present invention is that two charge storage sections are arranged in a circulating loop for one light receiving section.

More specifically, there is a photosensitive means having a light source for projecting light toward the subject, a light receiving section for receiving reflected light from the subject, and a light source for projecting light when the light source is projecting light and when not projecting light. a first and a second one each storing a signal obtained from said photosensitive means;
a storage section, a signal circulation means for mutually circulating the signals stored in the first and second storage sections, and a register for recording the signals stored in the first and second storage sections, respectively. and a signal transfer means for sequentially transferring the signals stored in the first or second storage section to the register means. More preferably, as in the later-described embodiment of the present invention, the signal obtained by the photosensitive means is an electric charge, and the first and second signals are synchronized with the emission and non-emission of the light source. The second storage unit sequentially stores charges from the photosensitive means. And preferably.

The signal transfer means is a detection means for non-destructively detecting whether or not the signal accumulated in the first or second accumulation section has reached a predetermined value. Based on this, the signals stored in the first or second storage section are sequentially transferred to the register means.

Next, embodiments of the present invention will be described using the respective figures.

FIG. 1 is a block diagram of conventional distance detection when light is projected onto the subject and the distance to the subject is detected using reflected light from the subject. The light source 1, for example, the light emitting diode LE emits light in a modulated manner via the buffer BP by the pulse φIR,
Light is projected onto the subject OB by the light projecting lens LNI, and reflected light is imaged as a projected spot image PS on the photoelectric conversion element SD by the light receiving lens LN2. The distance to the subject is detected by detecting the position of the projected light spot image on the photoelectric conversion element SD. In addition to the projected spot image, optical information as reflected light from the subject is superimposed on the photoelectric conversion element SD.
It is important to efficiently remove ambient light information when accurately detecting object distance.

FIG. 2 is a simplified explanatory diagram of the optical receiver disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 54-154382. For example, charges generated in the photosensitive section S when light is emitted are accumulated in the accumulation section AK, and charges generated in the photosensitive section S when the light is not emitted are accumulated in the accumulation section B.
accumulated in.

The difference between the charges accumulated in these two accumulation sections A and B is calculated by a differential circuit, and only the true light emitting signal is detected.

However, since the storage section A and the storage section B are arranged separately, the differential circuit DI is connected from the storage section A side and the storage section B side.
When converting C charge into voltage and inputting a signal, errors occur due to the characteristics of the conversion system. In this way, storage parts A, H
Due to the difference in sensitivity, if the output sensitivity differs, the output of the differential circuit will no longer correspond to the true light emission signal, especially if the amount of reflected light during light emission is small. becomes difficult.

FIG. 3 is an explanatory diagram of one embodiment of the present invention.

In the figure, 81 to SN are photosensitive pixel parts, ST1 is a first charge storage part, Sr1 is a second charge storage part, SHI,
SN2 is a charge transfer gate DCI.

DC2 is a barrier gate to which a DC voltage is applied, GA
, GB is a charge transfer unit, TCGI, TeO2 is a clear gate for unnecessary charges), FG is a first charge storage unit STI
is accumulated in Floating gates that non-destructively detect charges are arranged in each pixel. A.S.
R is an analog shift register such as a CCD for signal reading, FTI to FT4 are field effect transistors, R1-
R4 is a resistor %CI is a capacitor, OP1 is an operational amplifier to which a reference power supply VRF is applied to a non-inverting input terminal, and FT4 is provided as a feedback device.

PAG is an AGC circuit that generates, for example, signal read information from φP when the maximum value of the output of FC (70 - 50%) reaches a certain reference level.

φP is the output terminal of the AGL circuit PAG, φICGI yφ
SHI rφA, φICG2 rφ'aiii are each I
CGI, S H1゜GA (QB), ICG2, S
This is the control terminal for controlling N2, φ7. φ2 is a control terminal that controls the analog shift register ASR.

In addition, φR8 is a reset terminal that is output from the analog shift register ASR and resets unnecessary charges, and φT is a control terminal for shorting and controlling gate hand RFT4.) *VOUT (1) +VOUT (
2) is the output voltage at the indicated point.

QAI shown inside analog shift register ASH
F GA2 ,...QAN is the photosensitive pixel section S
l, S2,..., signal 1QBI as optical information at the time of light projection generated at SN? GB2-″・・・・・・-Q
BN is the photosensitive source pixel portion 81.82. . . . shows the transfer state of a signal as optical information when no light is emitted, which occurs in the SN. These terminals φICG1+φSHI...
. . . are configured to be controlled by timing pulses shown in FIG.

FIG. 4 is a timing chart and output waveform of the main part of FIG. 3.

When φICGt+φTCG2 is inverted to a low level at a time point, photocharges generated in the photosensitive pixel sections 81 to 8N are accumulated in the charge storage section STI. φIR is high level L
During AX, the light emitting diode LE emits light and forms a projected light spot image PS on the photosensitive pixel, and the charge QLAI, which is the sum of the projected light and ambient light, is accumulated in the storage section STI, and φ8H1 and φA
When φSHI and φA become high level, the charges accumulated in the storage section STI are temporarily transferred to the charge transfer section GA, and when φSHI and φA are inverted to low level, the charges QLAI are accumulated in the accumulation section ST2.

During LBI when φIR is at a low level, the light emitting diode LE is turned off, only ambient light information enters the photosensitive source pixel, and charge QLBI is accumulated in STI.

When φEiH1 and φA become high level, the storage section STI
.

The charge accumulated in 8T2 is transferred to the charge transfer section GA.

When φSHI and φA are temporarily transferred to GB and reversed to low level, the charge QLBI is accumulated in the accumulation section ST2, and the charge QLAI of the information from the previous light emission is input to the accumulation section STI in the interval jD, LA2. At this point, the signal is added to the signal from the current light projection. This operation is sequentially repeated, and the light information when the light is emitted and the light information when the light is not emitted are cyclically added. Further, at time tAK, when one of the outputs of the floating gate FG reaches the reference level, φP is inverted to the high level side and a signal read pulse pulse φSH2 is generated. When the φ8H2 pulse is generated at time tB, the charge QLAI+LA2, that is, QAI, stored in the charge storage section ST2 at the time of light emission is
v GA2 t...p Transfer QAN to analog shift register ASR. Furthermore, time tc teφ8
When the H2 pulse occurs, the charge QLB1+LB during non-light emission
2, that is, Qnt * GB2 +...r QBN
is transferred to analog shift register ASR. Also, at time tcK, in synchronization with the rising edge of the φ1 pulse, the charge Q
AI is read out via a charge-voltage conversion circuit consisting of a field effect transistor FTI and a resistor R1, and the output VOU
A voltage VQAI is generated at T (1). When φ1 is at a low level, the reset pulse φR1l+ goes to a high level, and the information read last time via FT3 is cleared. Repeat this.

Voltages VQBI, VQA2, as sequential image information
VQB2. -1... is read out. Time tc K
When the clock φT is inverted to the high level side, a feedback path for the operational amplifier OPI is formed, and a voltage almost the same as the reference power supply VRF is generated at the output VOUT (2), which corresponds to the difference between the capacitors CIKVQA and VRF. Voltage is stored.

Next, when φT is inverted to a low level and VQBI is read out, the true light emitting signal VQAI -'VQBI, which is the difference in light information between light emitting and non-emitting times of the photosensitive pixel S1, is obtained as shown in the figure. It will be done. By sequentially repeating the reading according to this method, it is possible to obtain true light projection signals of all the light-sensitive pixels S1 to SN.

As described above, when the present invention is used, there is a remarkable effect that distance detection can be performed with high precision even to a distant object by using the same loop method as shown in FIG.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional distance detection system for detecting object distance. FIG. 2 is a simplified explanatory diagram of a conventional light receiving device. FIGS. 3 and 4 are an explanatory diagram and a timing flowchart of an embodiment of the present invention, respectively. In the figure, 81 to SN are photosensitive source pixel portions STI, and Sr1 is the first photosensitive pixel portion STI. second charge storage section SHI,
SN2 is a charge transfer gate, ASR is an analog shift register FG, and floating gate PAG is an AGC circuit.

Claims (3)

[Claims] (1) A light source for projecting light to the subject side, a photosensitive means for receiving reflected light from the subject, and light obtained from the photosensitive means when the light source for projecting emits light and when not projecting light. first and second storage sections for storing signals, respectively; signal circulation means for circulating the signals stored in the first and second storage sections; It is characterized by comprising a register means for recording each of the stored signals, and a signal transfer means for sequentially transferring the signals stored in the first or second storage section to the register means. Photoelectric conversion device. (2) The signal obtained from the photosensitive means is an electric charge, and the electric charge from the photosensitive means is transferred to the first and second storage sections of ThM in synchronization with the emission and non-emission of the light source. The photoelectric conversion device according to claim 1, characterized in that the photoelectric conversion device sequentially accumulates. (3) The signal transfer means. and a detection means for non-destructively detecting whether or not the signal accumulated in the first or second accumulation section has reached a predetermined value; Alternatively, the photoelectric conversion device according to claim 1, wherein the signals stored in the second storage section are sequentially transferred to the register means.