JPH03106275A - Solid state image pickup device - Google Patents

Abstract

PURPOSE:To accurately decide exposure in accordance with the state of a target even if the target is arranged at any position of a screen by dividing a receiving screen into plural areas and deciding the exposure from the respective states of the plural divided areas. CONSTITUTION:A video signal X(t) obtained from a CCD 1 is inputted to prescribed period integrating circuits 31 to 34 at respective timings of divided signals DS1 to DS4 and their integration values I1(t) to I4(t) are respectively applied to comparators 41 to 44. The comparators 41 to 44 compare the integration values I1(t) to I4(t) with the upper limit value VH and lower limit value VL of a proper exposure range and applies the compared results to an arithmetic circuit 8. The combination of four evaluation values is stored in a decoder 50, an exposure accelerating signal OPEN or an exposure suppressing signal CLOSE outputted from the decoder 50 is applied to a timing control circuit 6 and the expansion/contraction of the accumulation period of optical charge of the CCD 1 is controlled. Even when the target is not positioned at the center part of the screen, the exposure can be accurately decided.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a solid-state imaging device equipped with an automatic exposure control function.

(Example) Prior Art Conventionally, in an imaging device using a COD solid-state imaging device, it has been proposed to electronically control exposure by utilizing the driving principle of a CCD. For example, JP-A-63-2476
In Publication No. 4, in the middle of the photoelectric conversion period of each vertical scanning period of the CCD, the photocharges accumulated in the imaging section up to that point are transferred and discharged, and the photocharges obtained by photoelectric conversion are transferred during the remaining photoelectric conversion period. By accumulating it, we control the expansion and contraction of the accumulation period. That is, by changing the photocharge discharge timing in accordance with the COD exposure amount, the photocharge accumulation period is controlled to expand or contract in accordance with the illuminance of the subject. In such an exposure control means, it is desired to accurately detect the exposure amount of the CCD, and various exposure amount detection methods (photometry methods) have been considered. For example, in Japanese Patent Application No. 63-35663 filed by the present applicant, the exposure amount is determined by integrating the video signal obtained from the CCD in units of one screen and comparing the integrated value with two values, an upper limit value and a lower limit value. It is determined whether it is within the appropriate range. Figure 6 shows solid-state imaging with automatic exposure control function? FIG. 7 is a block diagram of the device, and FIG. 7 is a timing diagram of its operation.

The COD (1) photoelectrically converts the received image for a certain period of time and outputs a continuous image signal (X, t) for each screen, which is pulse-driven by a clock generation circuit (7) to be described later. Video signal X obtained from COD (1)
, t, is subjected to processing such as sample hold and gamma correction in the signal processing circuit (2), and is output to an external device as a video signal Y , t). In addition, the video signal
t:l is input to the comparison circuit (4). Integral value I (t
, increases as time t passes, as shown in FIG.
At timing t1 of every cycle (IV) of the horizontal scanning period, the signal is taken into the comparator circuit (4), and the integrating circuit <3) is reset to become the reference level. In the comparison circuit (4),
Upper limit value VH and lower limit value VL of the appropriate exposure range (VL<
Vl1) and the integral value I(tl) at timing t■ are compared, and the judgment data ED is input to the decoder (5>).
If higher, the decoder (5>) outputs the exposure suppression signal CLOS
E is supplied to the timing control circuit (6>), and conversely, when it is lower than vL as shown by the broken line B, the decoder (5) supplies the exposure promotion signal OPEN to the timing control circuit (6).Then, the integral value I(tl ) is between vL and Vw, the decoder (5> does not generate any signals and the timings of the timing control circuit (6) do not change.The timing control circuit (6>) It generates a readout timing signal FT that determines the readout timing of photocharges and a discharge timing signal BT that determines the discharge timing of photocharges. The readout timing signal FT is based on the vertical scanning signal V.
The discharge timing signal BT has a timing pulse (A) for each blanking period D, and the discharge timing signal BT has a timing pulse (A) at a predetermined timing of the vertical scanning period. This timing pulse (mouth) is passed to the decoder (
The generation timing is delayed by each cycle (IH) of the horizontal scanning signal HD by the exposure suppression signal CLOSE from 5>, and is advanced by each IH by the exposure promotion signal OPEN,
The discharge timing of the photocharge is variably set. That is, the read clock φ and the discharge clock φ. generated by the clock generation circuit (7). are the timing pulses of the read timing signal FT (a) and the timing pulses of the discharge timing signal BT (b) 4.1 correspondingly, the clock pulses (c),
(2) The clock pulse of the discharge clock φ, (2) The clock pulse of the read clock φ, (c)
Photocharges are accumulated during the period L up to this point. Therefore, C.C.D.
(1) The exposure amount becomes smaller and the integral value 1 (tl) becomes V
, the timing at which the clock pulse (2) of the discharge clock φ9 is generated becomes earlier, and the photocharge accumulation period L becomes longer. Conversely, when the exposure amount of C O D (1) increases and the integral value I(tl) becomes larger than v8, the timing of generation of the clock pulse (2) becomes delayed and the accumulation period L becomes shorter. (c) Problems to be Solved by the Invention In the solid-state imaging device as described above, the COD photocharge accumulation period is controlled to expand or contract depending on the illuminance of the subject, and the COD
However, when photographing a subject with its back to the light source, the subject itself may appear dark even though the exposure level is within the appropriate range. this is,
If the illuminance of the subject is extremely low compared to the background illuminance, the high-level video signal representing the background will be suppressed, so even if the video signal representing the subject is at an appropriate level, it will be suppressed. In order to prevent such unnecessary suppression of video signals, in general video cameras, etc., the video signals in the center of the screen are selectively extracted, and the video signals in the center of the screen are The device is configured to measure exposure.

In other words, with a normal video camera, the subject is often located in the center of the screen because the operator operates the camera to capture the subject in the center of the screen, and it is only necessary to detect the amount of exposure in that center. It turns out.

However, with fixed-position cameras such as surveillance cameras and doorbells, the subject is not necessarily located in the center of the screen, and the subject's exposure is detected by detecting the exposure from the video signal in the center. It wasn't necessarily possible. Therefore, an object of the present invention is to detect an accurate amount of exposure regardless of the position of the subject, and to perform exposure control so that the video signal representing the subject is always kept at an appropriate level. <2) Means for Solving the Problems The present invention is intended to solve the above-mentioned problems, and includes a solid-state image sensor that photoelectrically converts a received light image at predetermined intervals to obtain a continuous video signal for each screen, and a light receiving device. An integrating circuit that divides the screen into a plurality of regions and integrates the above-mentioned video signals corresponding to each region, and compares the integrated value of this integrating circuit for each screen with the upper and lower limits of the appropriate exposure range, and calculates the above-mentioned values. A comparator circuit that evaluates the exposure amount of the divided areas as three values: excessive, appropriate, and insufficient; an arithmetic circuit that receives the evaluation value of this comparison circuit to obtain the number of appropriate exposure areas and also calculates the sum of each evaluation value; an exposure control circuit that generates an exposure suppression signal or an exposure promotion signal according to the number of exposure areas and the sum of the evaluation values; The present invention is characterized by comprising a drive circuit that expands with an exposure promotion signal.

(*) Effect According to the present invention, since the exposure amount is determined based on the state of each of the plurality of divided areas, no matter where the subject is located on the screen, the exposure amount can be determined accurately according to the situation of the subject. A judgment is made.

(to) Example An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of the solid-state imaging device of the present invention, showing a case where the exposure state is determined from video signals from four regions. In this figure, the CCD (1), signal processing circuit (2), timing control circuit (6), and clock generation circuit (7) are the same as in FIG. 6, and their explanation will be omitted. The video signal X(t)I obtained from CCD (1) and the divided signal DS. -DS. are taken into the integration circuits (31> to (34)) for a predetermined period at each timing, and the integral values h(1) to I4(t) are input to the comparison circuits (41> to (44)
are given to each. As shown in FIG.
), the video signal
(t) and accumulates it in a capacitor (303), and the potential of this capacitor (303) changes to the transistor (305).
) and a resistor (306) to the comparison circuit via a source follower circuit. And vertical scanning signal VD
The capacitor (303) is reset and lowered to the ground potential every vertical scanning period by a reset signal RS synchronized with .

The comparison circuits (41>~(44>) are the integration circuits (31>~(44>)
The integrated values 1f(t) to I4(t) from 34) are compared with the upper limit value Vi and lower limit value V, of the appropriate exposure range, and the comparison result is provided to the arithmetic circuit (8). These comparison circuits include two differential amplifiers (401 and 402) that compare the integral values I+(1-) to Ia(t) with VM and vL, respectively, and their comparison outputs at each timing of the reset signal RS. Consists of output pritubprop (403>(404),
Output the 2-bit signals L, ~L4 and obtain the integral value L('I-
) ~ I 4 (t) judgment results as underexposure '0, 0, .
Proper exposure '01', overexposure '1, 1. It is expressed as one of the three values. These 2-bit signals L, ~L4 are input to the arithmetic circuit (8), and '0' and '0' are input to 'o' and 'o' respectively.
,1, is "1", and '1,1, is "2"
is given as the evaluation value. The arithmetic circuit (8) adds the four evaluation values to obtain comprehensive evaluation data ED, and outputs the number of evaluation values 1"1" indicating appropriate exposure as appropriate number data QD. Therefore, the exposure state of C O D (1) is represented by the evaluation data ED and the appropriate number data QD. That is, a total of 3' (81) combinations of the four evaluation values for the signals L, ~L4 are possible, but for each signal L, ~L4,
If 4 is replaced and it is equivalent, for example, r0120
If J and '2100 are equivalent, there will be 15 ways shown in FIG. This figure shows the sum of evaluation values (evaluation data ED)
'oooo, to r2 when changes by 1
It shows the flow up to 222J, and everything is expressed by evaluation data ED and appropriate number data QD. For example, the ED is 5
If QD is 1, it indicates '0122J, and the same <E
Even if D is 5, if QD is 3, it will indicate '1112'. A combination number of these four evaluation values, a decoder (50
), and one of the evaluation data ED and the appropriate number data QD is specified. Therefore, as shown by the broken line in FIG. 3, by providing data to the decoder (50) as data for promoting the exposure amount (OPEN), data for fixing it (HOLD), and data for suppressing it (CLOSE), the specified If the combination of evaluation values is OPEN, the exposure promotion signal O
If it is at PEN or CLOSE, the decoder (50) outputs the exposure suppression signal CLOSE, and if it is at }10LD, it does not output any signal. OPENSHOLD like this, C
The LOSE classification is basically OPEN if the evaluation data ED is small, CLOSE if it is large, and HOLD if the appropriate number data QD is large, and the details can be set as necessary. Then, the exposure promotion signal OP outputted from the decoder (50)
EN or the exposure suppression signal CLOSE is given to the timing control circuit (6), and the storage period of the photocharge of COD (1) is controlled to be expanded or contracted in the same way as in FIG.

According to the above-mentioned means, unlike the conventional means in which the exposure amount is determined only based on the evaluation data ED, for example, even if ED is 3, if QD is 3, it is determined that the exposure is appropriate. , if QD is 1, there may be cases where it is determined that the exposure is insufficient.

FIG. 4 shows an example of a screen dividing method when the solid-state imaging device of the present invention is adopted in a doorbell, and FIG.
Each divided signal DS when the screen is divided as shown in the figure. ~D
S. This is a timing diagram. The screen is divided vertically into three parts, and the central part of the screen is equally divided into four parts horizontally, resulting in a total of six areas. Of these, the video signals corresponding to areas ■ and ■ are integrated to obtain an integral value 1t(t), and the same area ■
Integral value act 1 (JyI act). We obtain I 4(t). As described above, from the regions ■ to ■ and ■ excluding the region ■, the integral values I, (t) to I. (t) and performs automatic exposure control as shown in FIG.

In the case of a doorbell, the sky is always reflected at the top of the screen, so the area ■ where the sky is visible, where there is a large difference in brightness, is not used to determine the exposure amount. This kind of screen division is actually done by each integrating circuit (31).
This is done by setting the timing of taking in the video signal X (t) to (34), and the four types of divided signals DS! ~DS. It is divided according to That is,
During the period of scanning the area ■, the divided signal DS. ~DS.
becomes “0” during the horizontal scanning period, and each integration circuit (31〉~
(34> does not receive the video signal X(t), and continues ■
In period I during which ~■ is scanned, the divided signal DS. -DS. sequentially becomes ``1,'' and the video signal
(t) is each integrating circuit (31〉~(
34>. Then, during the period (■) in which the area (■) is scanned, the divided signal DS. -DS. during the horizontal scanning period.
1'', and the video signal
In each of the integrating circuits (31) to (34), video signals X, t) corresponding to areas ■ to ■ are accumulated, respectively, and
The video signal X (t) corresponding to each integrating circuit (31) to
It is accumulated in <34). As described above, in addition to providing four integration circuits (31) to (34) to obtain four integral values, one integration circuit is provided, and this integration circuit is connected to four fields over four fields.
By setting the timing (divided signals) to sequentially capture the video signals of different regions and changing the arithmetic circuit (8) from parallel input to serial input, the same operation as shown in Figure 1 is possible. In this case, the response speed is slow because four fields are required to determine the exposure amount, but the circuit scale can be significantly reduced, making it extremely effective for use in inexpensive and compact solid-state imaging devices. In the above embodiment, the case where the exposure amount is determined by obtaining four integral values from four types of areas was exemplified, but three
It is also possible to determine the exposure amount by obtaining integral values from each type of area or five or more types of areas. (G) Effects of the Invention According to the present invention, even in surveillance cameras, door phones, etc. where the subject is not necessarily located in the center of the screen, accurate exposure determination can be made, and the exposure is always adjusted according to the subject. It is possible to realize automatic exposure control and improve the image quality of the playback screen.

[Brief explanation of drawings]

1 to 5 relate to the present invention, FIG. 1 is a block diagram, FIG. 2 is a circuit diagram of an integrating circuit and a comparison circuit, FIG. 3 is a diagram showing combinations of evaluation values, and FIG. 4 is a diagram showing a combination of evaluation values. A diagram showing an example of screen division, and FIG. 5 is a timing diagram for performing the division shown in FIG.
FIG. 6 is a schematic diagram of a conventional solid-state imaging device, FIG. 7 is an operation timing diagram thereof, and FIG. 8 is a diagram showing changes in integral values over time. (1>...COD, (2)...signal processing circuit,
(3) (31>~<34>...integrator circuit, (4
)(41) to <44>...Comparison circuit, (5)(5
0)...Decoder, (6>...Timing control circuit, circuit. (7)...Clock generation circuit, (8)...Calculation

Claims (3)

[Claims] (1) A solid-state image sensor that photoelectrically converts the image it receives at predetermined intervals to obtain continuous video signals for each screen, and divides the light-receiving screen into multiple areas and integrates the video signals corresponding to each area, respectively. an integrating circuit; a comparison circuit that compares the integrated value of this integrating circuit for each screen with an upper limit value and a lower limit value of an appropriate exposure range and evaluates the exposure amount of each divided area as three values: excessive, appropriate, and insufficient; An arithmetic circuit that receives the evaluation value of this comparison circuit to obtain the number of appropriate exposure areas and the sum of each evaluation value, and outputs an exposure suppression signal or an exposure promotion signal according to the number of appropriate exposure areas and the sum of the evaluation values. A solid-state imaging device comprising: an exposure control circuit that generates photoelectric conversion, and a drive circuit that shortens an effective photoelectric conversion period of the solid-state imaging device for each predetermined period using the exposure suppression signal and extends it using the exposure promotion signal. (2) Sequentially capture video signals within one vertical scanning period into an appropriate number of the above-mentioned integrating circuits at different timings, accumulate video signals corresponding to the plurality of divided regions in each integrating circuit, and obtain a plurality of integral values. 2. The solid-state imaging device according to claim 1, wherein the images are obtained during the same vertical scanning period. (3) Video signals are taken into one of the integration circuits at different timings for each vertical scanning period, and video signals corresponding to the plurality of divided areas are sequentially accumulated in the integration circuit over a plurality of vertical scanning periods. 2. The solid-state imaging device according to claim 1, wherein a plurality of integrated values are continuously obtained in each vertical scanning period.