JPS6017712A - Differential type sensor device - Google Patents

Abstract

PURPOSE:To reduce an influence of a noise, and to obtain a focus detecting signal whose S/N ratio is remarkably good, by constituting a charge accumulating means for an operation, and a gate means, of a process of an MOS, and constituting an operating part as one body with a differential type sensor part. CONSTITUTION:Charge quantities A, B generated in two photoelectric converting parts A1, B1 by a reflected light from an object to be photographed, by a projection, and charge quantities A0, B0 generated by a circumferential light when the projection is stopped are shown conceptionally, and the sums A+A0, B+B0 of the respective charge quantities are accumulated in the first and the second charge accumulating parts A2, B2 from the respective photoelectric converting parts A1, B1, respectively. Also, at the time of nonprojection, the charges A0, B0 generated in the photoelectric converting parts A1, B1 are accumulated in the third and the fourth charge accmulating parts A3, B3, respectively. As for these accumulated charges, a difference is taken by a differential circuit, by which only the charge quantities A, B of a reflected light component by a projection are detected, and as a result, at the time of A=B, for instance, it is decided that a lens system of a distance detecting system is at a focused position, and at the time of A>B, and A<B, it is decided that said system is in a front focus state and a rear focus state, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a differential sensor device, and particularly relates to a differential sensor device that emits two lights onto a subject, receives the reflected light from the subject by a light receiving means, and uses a signal from the light receiving means to detect the subject. The present invention relates to a differential sensor device that is effective when used for distance detection.

Conventionally, non-storage type photoelectric conversion elements such as silicon photodiodes have been used as photoelectric conversion elements for distance detection, but since the output signals generated by these photoelectric conversion elements are very small, it is difficult to eliminate circuit noise during amplification. The influence was large, and it was not possible to obtain a very good S,/Nk, and the measurable detection distance was also short.

An object of the present invention is to provide a differential sensor device that has good signal readout characteristics and can obtain signals with a high S/N ratio, and a further object is to obtain a preferable signal output when used in a distance detection system. It will be done. The purpose is to provide a differential sensor device.

The main features of the differential sensor device for achieving the purpose of the present invention are a light source for projecting light onto the subject, and a first sensor for receiving reflected light from the subject, whose charge amount changes depending on the amount of incident light.
and a second photoelectric conversion section, and the light source is emitting light. The first and second charge storage sections each accumulate the entire charge generated in the second photoelectric conversion section, and the total charge generated in the first and second photoelectric conversion sections accumulates for a certain period when the light source does not emit light. The difference between the information stored in the first charge storage part and the information stored in the third charge storage part is determined by the difference between the information stored in the first charge storage part and the information stored in the third charge storage part. The difference between the information stored in the fourth charge storage section and the information stored in the fourth charge storage section is calculated via the charge storage means and the gate means. More preferably, the information stored in the first charge storage section and the information stored in the third charge storage section are the information stored in the second charge storage section and the information stored in the fourth charge storage section. The difference between the information given and the difference? Embodiments of the present invention will be described below with reference to each figure.

FIGS. 1(a), 1(b), and 1(e) are explanatory diagrams of storage type photoelectric conversion means used in a differential type sensor device.

Figure 1 (a) shows the amount of charge generated in the two photoelectric conversion units A4 + B by the reflected light from the subject when the light is emitted from the light source, and the amount of charge generated by the ambient light when the light emission is completely stopped. The generated charge amounts Ao and Bok are shown conceptually, and the sum of each charge amount is A + Ao.

B + Bo is the first
．． i2 charge storage section A2. Charges A are accumulated in B2 and generated in the photoelectric conversion unit A41BH when no light is emitted. +BO is accumulated in the third and fourth charge accumulation sections As and Bs, respectively.

By taking the difference between these accumulated charges in the differential circuit of the present invention, only the charge amounts A and B of the reflected light components due to the projection of light are detected, as shown in FIG. 1(b), and as a result, as shown in FIG. (C
) When the electric charges A and B are A=H, for example, the lens system of the distance detection system determines that it is the in-focus position, and when A>B it is in the front focus state, and when A<H it is in the back focus state. to decide. At this time, it is preferable to maintain the value of the charge 1ffl A + B at a constant value, since the slope of A-B near the in-focus position becomes approximately constant, and the focusing accuracy can be maintained constant.

FIG. 2 is an explanatory diagram of an embodiment of the photoelectric conversion section of the photoelectric conversion means used in the differential sensor device. AS and BS are the first
．． A second photoelectric conversion unit, AL.

BL is the first stage that accumulates the interest of the reflected light and ambient light when the light is emitted. The second charge storage parts AD and BD store the entire ambient light when no light is emitted. Fourth charge storage unit ICG1. IC
G2 is an integral clear gate, S, for clearing the charges generated from the photoelectric conversion units AS and BS when φICG is at a high level.
Hl.

5) 12 is a charge transfer gate, and when φ8H1 is at a high level, charges generated from the photoelectric conversion units AS and BS? Charge storage section A
When φ8H2 is at a high level, the charges generated from the photoelectric conversion units AS and BS are accumulated in the charge accumulation units AD and BD. Di-D4, L1 to L3 are charge transfer parts, and clock pulses φ1. By φ2, all charges G2 accumulated in the charge storage section are transferred to the voltage conversion section BC, and signal reading is performed.

Charges accumulated in AL and BL and AD and BD (A+Al
l+)+(B+BO) and Ao+Bo are read out non-destructively via floating gates FGI and FGZ.
(A0Ao) + (B
+ Bo) (Ao + Bo) -A + B
A signal VA+B is output. When the appearance of VA+H reaches the standard], read out all of I-100.

FIG. 3 is an explanatory diagram of one embodiment of an electric circuit for fully driving the photoelectric conversion means, and FIG. 4 is a timing chart of the main parts of FIG.

Time t. When the power switch sw is turned on, the power source E1 is applied to each part, the oscillator O8C starts oscillating, and the constant voltage power source REQ outputs Vc f. At the same time, in synchronization with the rising pulse of OSC, the output of the AND gate A N I) is inverted to a high level for a short time determined by the capacitor C20 and the resistor R20, so the one-shot circuit ONI generates all the one-shot pulses, and the OR gate OR6 at time t
. -t2, unnecessary charge accumulation 11a of the photoelectric conversion section in the storage type photoelectric conversion element is performed. Also during this time R8T
Flip-flops RFI and RF5 are also reset.

In addition, capacitor C40 and resistor R4 (1)
AN3. After the initial setting of the D flip-flop 1) F' 1 through OR gates OR8 and OR9, the pulse from OS C is divided and the clock pulse φ1
°φ2 is generated, and unnecessary items in the charge storage section and transfer section are cleared. Also, since the transistor Tri is turned on by the high level signal of the OSC, the light emitting element LD emits light with the current regulated by the resistor R1, and the light emitting lens LN1'
The reflected light is projected onto the subject OB through the light receiving lens LN.
An image is formed on the photoelectric conversion element via 2e. When a reflected light image is formed at the center of the contact position of the photoelectric conversion units A1 and Bl, the outputs of the photoelectric conversion units A, , and B become equal, and the distance detection system is configured such that, for example, the photographing lens is in the focused position. has been done. At time t, when the output of the one-shot ONI is inverted to a low level, the reflected light signal when light is emitted when O8'C is at a high level is reflected from the charge storage section AL.

When BL and OSC are at a low level, signals at the time of non-emission are alternately stored in charge storage parts AD and BD.

At the same time, the output of AN3 is inverted to a low level, so the supply of pulses to the DPI is cut off, and φ2 is held at a high level and φ1 is held at a low level to accumulate charges. VAA at time t3
When the 3B signal exceeds the reference voltage determined by resistors R2 and R3, the output of the comparator CPI is inverted to the high level side, so at time t4, the R8T flip-flop RFI is set via the OR gate OR1 in synchronization with the rising edge of the OSC pulse. , one-shot ON2 generates all one-shot pulses, sets φICGe to high level, and completes storage of image information in the storage type optical '1°C conversion means. Time 1. D in
RF5 is set in synchronization with the rise of FO's Q output,
Since the one-shot circuit ON4 generates all one-shot pulses, the pulses are supplied to DF1 via the AND gate AN10y, so that φ1. φ2 is turned on and off, and the stored image information is read out. In synchronization with the rising edge of OH2, the pulse control circuit PCK is driven, and at time t
When AteφA pulse occurs, sample and hold circuit SD
Information VAD stored in AD is read out at I.

When the φB pulse occurs at time tB, the information VAL stored in AL is read out, and the information VAL - VAD is held in the sample hold circuit SD3 via the differential amplifier circuit DA5'. When a φC pulse occurs at time tQ, the sample and hold circuit SDI outputs the information stored in BD (tl).
is read out. When φD pulse 5 occurs at time tD, the information VB stored in BL is sent to the sample hold circuit SD2.
L is read out, and the information of VBL - VBD is held in the sample and hold circuit SD4 via the differential amplifier circuit DA5'e, and at the same time, the information of (VAL - VAD ) - ( VBL-
VBD ) information is detected and held. Based on this information, the photographing lens is driven to the in-focus position via the control circuit CKTk. Note that the image information output to the charge voltage converter is cleared by setting φR8' to high level after each sample hold and hold at time t6.
is reset in synchronization with the rise of the Q output of the DFO.

- The same operation as t6 is repeated thereafter.

In these conventional examples, all calculations of information output in a time-series manner are performed via a sample-and-hold circuit and a differential amplifier circuit, but these circuits are complex, and in order to perform high-precision calculations, It requires 3 forces to be constructed using bipolar transistors, and it is difficult to construct it integrally with the differential sensor section.

The present invention performs these calculations with high precision using a charge storage means and a gate means with a simple circuit configuration, and fourth, presents a structure in which these calculation circuits can be integrated into a differential sensor circuit. It is something to do.

The fifth circuit 1 is a 6-air circuit according to an embodiment of the present invention.

CNT is a drive circuit for driving the photoelectric conversion means SPD of FIG. 3, PDK corresponds to the pulse control circuit PCK of FIG. 3, and gate means AGI-AG3, B
GI to BG3, fully controls CGI.

C50 to C54 are charge storage means consisting of capacitors, F
GI and FG2 are field effect transistors, which together with resistors R50 and R51 constitute a source follower circuit.

VCI and VO2 are appropriate reference voltages.

Figure 6 is a timing chart of the main parts of Figure 5. Using this, the entire operation of Figure 5 will be explained in detail. When the VAD information is output from 10 according to the time, the analog gates AGI and AG3 are on and AC3 is off, so the voltage information of VAD -MCI is stored in the capacitor C50.

At time tA1, analog gates AGI and AG3 are turned off, A
When C3 turns on, the VOTI terminal outputs VOTI (A)
is VOTI (A) = VO2-(VAD -VCI
).

When the VAL information is output from ■0 at time tB, the analog gate AGI is on and AC3 and AC3 are off, so the voltage information of VAL - VO2 is stored in the capacitor C51 and at the same time the VOTI terminal is output. VOTI(
B) is VOTI (B) = VOTI (A) + VAL
-VC2=VAL -VAD + VCl and changes as shown in FIG.

In other words, it can be seen that an output of the difference between VAL and VADO can be obtained based on the reference voltage yc12.

Also, at time tB, analog gate BGI is activated at the same time.

BG3 is on and BG2 is off, so VOTI(B)
The voltage information of VAL -VAD is stored in the capacitor C52 via a source follower circuit consisting of rGl and a5o.

The offset voltage of the source follower circuit is included as a bias term, so it is ignored.

At time tB1, analog gate BG2 is turned on, BGI, B
Since G3 is turned off, the output from the VOT2 terminal is VOT2(B) VO'r2(B) = VO2-(VAL-VAD
).

When information on VBD is output from VO at time tC, since analog gates AGI and AC3 are on and AC3 is off, capacitor C501 stores voltage information on VBD-VCI.

At time tcx, analog gates AGI and AG3 are turned off, A
When C3 is turned on, the output VOTI(C) of the VOT1 terminal is VOTI(C) = VO2-(VBD-Vat)
becomes.

When the VBL information is output at time tD, the analog gate AGI is on and AC3 and AC3 are off, so the voltage information of VBL - VO2 is stored in the capacitor C51, and at the same time the VOTI terminal output yo'rt (1 )) is VOTx (D) = VoTt (C) + VBL - VC
2=VBL-VBD-1-Vct.

Also, the AND gate BGI is on, BG2, BG
Since FG2.3 is off, the VOTI (D) information is FG2.
Through the source follower circuit consisting of R51, VBL -VBD +VQ1- VO2 (D voltage information is stored in the capacitor C53, and at the same time, the output VOT2 (
D) is VO'l'2(D) =VOT2(B) 10VB
L-VBD+VC1-VC2=(VBL-■D) -
(VAI, -VAD) becomes +VC1, and the reference voltage y
As a cs'2 standard, the true light emission signal obtained by subtracting the ambient light signal when no light is emitted from the sum signal of the light emission signal of the B sensor section and the ambient light signal, and the light emission signal of the A sensor section and the ambient light ( It is possible to output the difference r between the sum signal of No. g and the true light emitting signal obtained by subtracting the surrounding source signal at the time of non-light emitting.

Furthermore, it goes without saying that the arithmetic circuit comprising the capacitor and the gate means is not limited to this embodiment, and that various modifications can be considered.

The difference between the true light emission signals of the A sensor and the B sensor output to the terminal VO'r2 is sampled and held by the sample and hold pulse φCGI to the capacitor C54 via a source follower circuit consisting of a field effect transistor FG2 and a resistor R51. The focus is adjusted by the open side single circuit CKT.

Although the explanation of this embodiment is based on the voltage calculation type, it is clear that the configuration of the present invention is also applicable to the charge calculation type.

Further, the present invention is an arithmetic method suitable for arithmetic processing of information outputted in a time-series manner.

As described above, the differential type sensor device of the present invention can be constructed by the processes of the charge storage means for calculation and the gate means 'rhoS, so the calculation section can be configured integrally with the differential type sensor section to reduce the influence of noise. There is a remarkable feature that it is possible to obtain a focus detection signal with significantly improved S/H.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (C) are explanatory diagrams of an accumulation-type photoelectric conversion means used in the differential sensor device l according to the present invention, and FIG. 2 is an illustration of one of the photoelectric conversion means used in the present invention. An explanatory diagram of the embodiment, FIG. 3 shows the photoelectric conversion means used in the present invention? FIG. 4 is an explanatory diagram of one embodiment of an electric circuit for driving, and FIG. 4 is a timing chart of the main part of FIG. 3. FIG. 5 is an explanatory diagram of an electric circuit according to an embodiment of the present invention, and FIG. 6 is a timing chart of the main part of the electric circuit shown in FIG. In the figure, Al,, Bl are photoelectric conversion parts, A2 r A3
T B2 + B3 is a charge storage section, A + B r A
o l Bo indicates the total amount of charge. Patent applicant: Canon Co., Ltd.

Claims (2)

[Claims] (1) A light source for projecting light onto the subject, and a first light source for receiving reflected light and sound from the subject, whose charge amount changes depending on the amount of incident light.
and a 20th photoelectric conversion unit, a photoelectric conversion means having a first and a second photoelectric conversion unit, each of which accumulates all charges generated in the first and second photoelectric conversion units while the light source emits light; For a certain period of time when no light is emitted by the light source, the first. Ii2
It has a third and a fourth charge storage section each storing charges generated in the photoelectric conversion section, and information stored in the first charge storage section and information stored in the third charge storage section. and the difference between the information stored in the second charge storage section and the information stored in the fourth charge storage section through the charge storage means and the gate means. Differential type sensor device. (2) The information stored in the first charge storage section and the third charge storage section
The difference between the information stored in the second charge storage section and the information stored in the fourth charge storage section? A differential sensor device according to claim 1, characterized in that the calculation is performed through charge storage means and gate means.