JPH05219451A - Shutter speed controller for solid-state image pickup element - Google Patents

Abstract

PURPOSE:To provide the shutter speed controller for the solid-state image pickup element having many number of steps of the shutter speeds able to be set in which the shutter speed is easily set. CONSTITUTION:This controller is provided with a shutter control signal generating means SC generating a shutter control signal from a shutter control level in response to a current shutter speed till a shutter control level in response to an object shutter speed at the revision of the shutter speed whose level is gradually changed and a shutter speed control circuit 20 generating a reset pulse for a period in response to the result of level comparison of a sawtooth wave signal reset to a reference potential for each vertical period with a reset pulse fed for a vertical blanking period and the shutter control signal, supplying the reset pulse to a solid-state image pickup element 1 and controlling the storage time of the solid-state image pickup element in response to the production period of the reset pulse.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shutter speed control device for a solid-state image pickup device such as a CCD (charge coupled device).

[0002]

2. Description of the Related Art A conventional example of a shutter speed control device for a solid-state image pickup device will be described with reference to FIG. Reference numeral 1 denotes a solid-state imaging device, such as a CCD, whose charge accumulation time can be controlled,
The CCD 1 accumulates image light incident through an image pickup lens (not shown) as a charge for each pixel and outputs it as an electric image pickup signal. The charge accumulation time depends on a reset pulse SUB described later. Controlled. And CC
After the image pickup signal output by D1 is amplified by the amplifier circuit 2, the automatic gain control circuit (AGC circuit) 3 adjusts the gain to a predetermined level. Then, the image pickup signal output from the AGC circuit 3 is supplied to the video signal processing circuit 4, and the video signal processing circuit 4 converts it into a video signal of a predetermined format such as the NTSC system. Then, the converted video signal is output to the output terminal 5
Is supplied from the monitor to various video equipment (not shown) such as a monitor and VTR.

Next, the structure of the shutter control signal generation circuit SC will be described. DC power supply with positive voltage + V1 and negative voltage -V2
Between the DC power supply of the resistor R1 and the tact switch TS1
And a series circuit of the tact switch TS2 and the resistor R2 are connected in series, and the middle point of the connection is the resistor R.
3 is connected to the inverting input terminal of the operational amplifier 12. The tactile switches TS1 and TS2 form a seesaw switch SS. The non-inverting input terminal of the operational amplifier 12 is grounded. A resistor R5 is connected between the output terminal and the inverting input terminal of the operational amplifier 12, and the inverting input terminal is connected to the DC power supply of negative voltage -V3 through the resistor R4. Then, the output voltage from the operational amplifier 12 is supplied to the A / D converter 14 and converted into a digital signal.

In this shutter control signal generation circuit SC,
When the seesaw operator for the tact switches TS1 and TS2 is not operated, the output voltage V _{OUT of the} operational amplifier 12
Becomes, for example, 2.5 V, and the output digital value of the A / D converter 14 becomes, for example, 125. When the seesaw operator is pushed to the tact switch TS1 side for 0 seconds to less than 2 seconds, the output voltage V _OUT of the operational amplifier 12 becomes, for example, 1
V, and the output digital value of the A / D converter 14 is
For example, it becomes 50, and the set speed changes at a speed of, for example, +10 steps / second, and when the pressing time of the seesaw operator becomes 2 seconds or more, only the set speed changes to +20 steps / second. Tactile switch TS
When the switch is pressed to the 2 side for 0 second to less than 2 seconds, the output voltage V _OUT of the operational amplifier 12 becomes 4 V, and the output digital value of the A / D converter 14 becomes 200, for example. The set speed changes at a speed of, for example, -10 steps / second, and when the time for pressing the seesaw operator is 2 seconds or more, only the set speed changes to -20 steps / second.

The shutter control voltage digitized by the A / D converter 14 is supplied to the clear scan processing circuit CS. In the clear scan processing circuit CS, the digitized control voltage is corrected by using the central processing unit and then converted into an analog signal, and the corrected shutter control voltage and the reset pulse supplied during the vertical blanking period are used. Level comparison is performed with the sawtooth wave signal reset to the reference potential every vertical period, and the reset pulse generated in the period corresponding to the comparison result is generated. And
This reset pulse is supplied to the CCD 1 through the amplifier 18, and the CCD 1
Control the storage time of.

[0006]

However, since the seesaw switch is used in the shutter control signal generating circuit of the conventional shutter speed control device for the solid-state image pickup device, the set speed is low at the beginning of the operation of the seesaw switch. If the operation is continued for a long time, the set speed becomes high, which makes it difficult to set the shutter speed, and there are disadvantages that there are few steps of the shutter speed that can be set. In view of such a point, the present invention is to propose a shutter speed control device for a solid-state image sensor in which the shutter speed can be easily set and the shutter speed can be set in many steps.

[0007]

According to the present invention, when a shutter speed is changed, a shutter control signal whose level gradually changes from a shutter control level according to a current shutter speed to a shutter control level according to a target shutter speed is generated. Shutter control signal generating means SC, and the level of the sawtooth wave signal reset to the reference potential every vertical period by the shutter control signal from the shutter control signal generating means SC and the reset pulse supplied during the vertical blanking period. A shutter speed control circuit 20 that generates a reset pulse in a period according to the comparison result, supplies the reset pulse to the solid-state imaging device 1, and controls the accumulation time of the solid-state imaging device 1 according to the generation period of the reset pulse. And have. The shutter control signal generating means SC is composed of a pressure sensitive resistance voltage divider to which a DC voltage is applied.

[0008]

According to the present invention, the shutter control signal from the shutter control signal generating means SC and the sawtooth wave signal from the sawtooth wave generation circuit 30 are level-compared, and a reset is generated in a period according to the comparison result. The pulse is supplied to the solid-state image sensor 1, and the accumulation time of the solid-state image sensor 1 is controlled according to the generation period of the reset pulse.

[0009]

An embodiment of the present invention will be described in detail below with reference to FIG. The configuration of the shutter speed control circuit 20 in FIG. 1 will be described with reference to FIG. Reference numeral 1 denotes a solid-state image sensor such as a CCD whose charge accumulation time can be controlled.
In this CCD 1, image light incident through an imaging lens (not shown) is accumulated as charges for each pixel and is output as an electric imaging signal. The accumulation time of charges is reset as described later. It is controlled by the pulse SUB. Then, after the image pickup signal output from the CCD 1 is amplified by the amplifier circuit 2, the automatic gain adjustment circuit (AGC circuit) 3 adjusts the gain to a predetermined level. Then, the image pickup signal output from the AGC circuit 3 is supplied to the video signal processing circuit 4, and the video signal processing circuit 4 converts it into a video signal of a predetermined format such as the NTSC system. Then, the converted video signal is supplied from the output terminal 5 to various video devices (not shown) such as a monitor receiver and a VTR.

Next, the structure of the shutter control signal generating means SC will be described. DC power supply with positive voltage + V1 and negative voltage -V
A series circuit of resistors R1 and R2 is connected between the two DC power supplies. A seesaw volume 11 is composed of a series circuit of pressure sensitive variable resistors RA and RB. The pressure-sensitive variable resistors RA and RB normally have a resistance value of about 10 MΩ, and the resistance value gradually decreases by applying pressure. This seesaw volume 11 is a case 11a.
The pressure sensitive resistors RA and RB are arranged inside, and the seesaw operator 1
By pressing 1b on the a side and the b side, the resistance values of the pressure sensitive resistors RA and RB are changed respectively.

Both ends of the pressure-sensitive variable resistor RA have terminals T1 and T2.
It is connected in parallel to both ends of the resistor R1 via 2. Both ends of the pressure-sensitive variable resistor RB are connected in parallel to both ends of the resistor R2 via terminals T2 and T3. The connection midpoint of the resistors R1 and R2 is connected to the inverting input terminal of the operational amplifier 12 through the resistor R3. The non-inverting input terminal of the operational amplifier 12 is grounded. A resistor R5 is connected between the output terminal and the inverting input terminal of the operational amplifier 12, and the inverting input terminal is connected to the DC power supply of negative voltage -V3 through the resistor R4. The output voltage from the operational amplifier 12 is A /
It is supplied to the D converter 14 and converted into a digital signal.

This shutter control signal generating means SC can be represented by an equivalent circuit (1) shown in FIG. 5, and this equivalent circuit (1) can be further represented by an equivalent circuit (2) shown in FIG. Therefore, the output voltage V _OUT of the operational amplifier 12 is V _OUT = (V3 / R4 + V2 / RY-V1 / RX) · R
It can be represented by 5. Here, R4 and R5 represent the resistance values of the resistors R4 and R5, respectively. RX represents the sum of the parallel resistance value of the resistance values of the resistors R1 and RA and twice the resistance value of the resistor R3. RY represents the sum of the parallel resistance value of the resistance values of the resistors R2 and RB and twice the resistance value of the resistor R3.

In this shutter control signal generation circuit SC,
When the seesaw operator 11b of the seesaw volume 11 is not operated, the output voltage V _OUT of the operational amplifier 12 is, for example, 2.5 V, and the output digital value of the A / D converter 14 is, for example, 125.

When the a-side of the seesaw operator 11b of the seesaw volume 11 is strongly pressed, the output voltage V _OUT of the operational amplifier 12 gradually changes from 0 V to less than 1 V, and the output digital of the A / D converter 14 is changed. If the value is
It gradually changes from 0 to less than 50, and the set speed changes at a speed of, for example, +20 steps / sec. When the a side of the seesaw manipulator 11b of the seesaw volume 11 is weakly pressed, the output voltage V _OUT of the operational amplifier 12 becomes, for example,
Gradually changes from 1V to less than 2V, and A / D converter 14
The output digital value of gradually changes from 50 to less than 100, and the set speed is +10 steps /
Varies at a rate of seconds. When the b side of the seesaw operator 11b of the seesaw volume 11 is weakly pressed, the operational amplifier 1
The output voltage V _{OUT of} 2 gradually changes from 3 V to less than 4 V, and the output digital value of the A / D converter 14 becomes
For example, it gradually changes from 150 to less than 200, and the set speed changes at a speed of, for example, −10 steps / second. When the b side of the seesaw operator 11b of the seesaw volume 11 is strongly pressed, the output voltage V of the operational amplifier 12 is increased.
_OUT gradually changes from 4V to 5V, A /
The output digital value of the D converter 14 gradually changes from 200 to 250, and the set speed is -20, for example.
Varies at a rate of steps / second

Then, the shutter control voltage digitized by the A / D converter 14 is supplied to the clear scan processing circuit CS.
To the central processing unit 15 of the microcomputer configuration. The central processing unit 15 includes a mode switch 16
Is connected, and the shutter control voltage data is corrected by the adjustment mode instructed by the mode switch 16, and the corrected shutter control voltage data is supplied to the D / A converter 17 as a PWM wave (pulse width modulation wave). It is supplied and converted into an analog voltage signal. In this case, the PWM wave output by the central processing unit 15 is created with a non-linear characteristic with respect to the input shutter control voltage data.

Explaining this non-linear characteristic, P
When the value indicated by the WM wave is D _P , the maximum change amount ΔD _P of this PWM value D _P per unit time is set by the following equation. ΔD _P = k / D _p where k is a constant. By setting the change amount of the PWM value D _P by this equation, the maximum change amount ΔD _P can be increased when the PWM value D _P is a relatively low level value, and can be increased when the PWM value D _P is a relatively high level value. , The maximum change amount ΔD _P can be increased, and when the value is at a relatively high level, the maximum change amount ΔD _P can be suppressed to be small.

Then, a voltage signal obtained by analog-converting this PWM wave which is shutter control voltage data by the D / A converter 17 is supplied to the shutter speed control circuit 20 via the terminal 21. This shutter speed control circuit 2
0 is configured as shown in FIG. 2, the image reading pulse SG is supplied from the terminal 6, and the reset pulse R is supplied from the terminal 7.
S is supplied, and the vertical blanking signal V-B is supplied from the terminal 8.
LK is supplied. The shutter speed control circuit 20 includes a sawtooth wave generation circuit 30. The sawtooth wave generation circuit 30 supplies the output of the constant current source 31 to the inverting side input terminal of the operational amplifier 32, and the non-inverting input terminal of the operational amplifier 32 is grounded via the resistor R1. In this case, the output current value of the constant current source 31 is controlled by the current control circuit 24 described later. Then, the inverting side input terminal of the operational amplifier 32 is connected to the output terminal of the operational amplifier 32 via the capacitor C1. Furthermore, in parallel with the capacitor C1,
The switch 33 is connected. Then, the switch 33 is controlled by the switch control circuit 23.

The switch control circuit 23 is supplied with the image read pulse SG from the terminal 6, and outputs a control signal for turning on the switch 33 each time the image read pulse SG is supplied. In this case, the image reading pulse SG is
The pulse is supplied for each field of the video signal and is supplied at the beginning of each field. Therefore, the switch 33 is turned on for a moment at the beginning of each field.

Further, the vertical blanking signal V-BLK supplied from the terminal 8 is supplied to the current control circuit 24, and the current control circuit 24 increases the output current value by a predetermined value during the vertical blanking period as compared with other periods. The constant current source 31 is controlled as described above.

By constructing the sawtooth wave generating circuit 30 in this manner, the output potential increases every time the switch 33 is turned on, that is, every field, and when the output potential becomes a constant potential, it returns to the original state. A sawtooth signal is obtained. In this case, in this example, the vertical blanking signal V-BL
Since the output current value of the K constant current source 31 is set to be larger than the other periods, as shown in D of FIG. 3, when the output potential increases to a predetermined value or more during the vertical blanking period, this The rate of increase of the potential becomes large, that is, the slope of the potential change becomes steep.

Then, the sawtooth wave is supplied to the inverting side input terminal of the comparator 25 and is supplied to the detection circuit 40. This detection circuit 40 performs peak detection, supplies the output of the sawtooth wave generation circuit 30 to the anode of the diode D1, and the cathode of this diode D1 is the operational amplifier 4
1 to the non-inverting side input terminal. Also, the diode D
The cathode of No. 1 is grounded via the capacitor C2. Further, the output terminal of the operational amplifier 41 is connected to the operational amplifier 4
Connect to the inverting input terminal of 1. Further, the shutter control voltage obtained at the terminal 21 is supplied to the anode of the diode D2 via the resistor R2, and the output terminal of the operational amplifier 41 is connected to the cathode of the diode D2. And further,
The anode of the diode D2 is connected to the non-inverting side input terminal of the comparator 25.

With this configuration, the detection circuit 40
Then, the peak of the sawtooth wave output from the sawtooth wave generation circuit 30 is detected, and the shutter control voltage converges non-linearly to the peak detected level. That is, due to the non-linear characteristic of the diode D2 connected between the input side of the shutter control voltage and the detection circuit 40, as shown in FIG.
When the input voltage (shutter control voltage) V _S obtained at 1 is low level, the potential V _D of the anode of the diode D2 changes following the change of the input voltage V _S. On the other hand, when the input voltage V _S approaches the peak V _P of the sawtooth wave,
Due to the non-linear characteristic of the diode D2, the change in the potential V _D is delayed.

Then, the diode D2 having such characteristics
The shutter control voltage and the sawtooth wave supplied to the anode of the are compared in level by the comparator 25, and a detection signal that changes when the shutter control voltage exceeds the level of the sawtooth wave is obtained. This detection signal is supplied as a gate pulse to one of the input ends of the AND gates 27 and 28, and is supplied from the terminal 7 to AN.
A vertical blanking signal V-BL supplied from the AND of the reset pulse RS supplied to the other input terminal of the D gate 27 and the other input terminal of the AND gate 28 from the terminal 8.
The logical product of the negative theory of K and the AND gate 27 of each
And 28. Then, the logical product outputs of the AND gates 27 and 28 are supplied to one and the other input terminals of the OR gate 29 to obtain an output as a logical sum, and this logical sum output is supplied to the output terminal 22 as a reset pulse SUB. To do.

Then, the reset pulse SUB obtained at the terminal 22 is supplied to the CCD 1 through the drive circuit 18, and the charge accumulated in the CCD 1 is swept out by the reset pulse SUB.

Next, the operation of this embodiment will be described with reference to FIG. 3, focusing on the control of the shutter speed. First,
Imaging is performed in synchronization with the vertical synchronization signal VD shown in A of FIG. Based on the vertical synchronizing signal VD, a vertical blanking signal V-BLK (B in FIG. 3) and an image reading pulse SG
(C in FIG. 3) is created, and the charges accumulated in the CCD 1 are read in a vertical cycle in synchronization with the image reading pulse SG. The sawtooth wave output from the sawtooth wave generation circuit 30 in the shutter speed control circuit 20 is synchronized with the image read pulse SG and the vertical blanking signal V-BLK is generated as shown in D of FIG. In the vertical blanking period when the level is low, the rate of increase of the potential is large.

When the potential of the sawtooth wave is lower than the shutter control voltage V _a or V _D , the output of the comparator 25 becomes high level. Therefore, the width of the high level period of the output of the comparator 25 is continuously (analogously) controlled by the shutter control voltage. Then, for example, when the subject is bright, the shutter control voltage high (as V _b in D in FIG. 3) that when you try to increase the shutter speed, the width of the high-level period of the output of the comparator 25 becomes wider (G in FIG. 3).

The reset pulse RP supplied through the terminal 7 is synchronized with the horizontal synchronizing signal as shown by F or H in FIG. The AND gate 27 allows the reset pulse RS to pass when the output of the comparator 25 is at the high level so that the reset pulse RS is not affected. Further, the AND gate 28 outputs the signal to the terminal 8 when the output of the comparator 25 is high level.
The negative logic of the vertical blanking signal V-BLK shown in FIG.

Therefore, the OR gate 29 lowers the shutter control voltage (V of D in FIG. 3) when the subject is dark, for example.
_Then , if you try to lower the shutter speed,
The width of the high level period of the output of the comparator 25 is narrowed (E in FIG. 3), the high level period of the output of the comparator 25 is the high level period of the vertical blanking signal V-BLK,
That is, when the output is shorter than the so-called video period (hereinafter referred to as the low speed shutter region), the output of the comparator 25 is at the high level,
The reset pulse RS is output as the reset pulse SUB. That is, the OR gate 29 is
The reset pulse SUB controlled by 1H unit is output.

For example, when the shutter control voltage V _a (D in FIG. 3) and the sawtooth wave are compared to obtain a comparison output (E in FIG. 3) of the comparator 25 which is inverted to a low level during the video period. , F of FIG. 3, the output of the reset pulse RS is stopped from the time of the inversion to the low level, and the charge is accumulated in the period T _a until the next rise of the image reading pulse SG. This accumulation time T _a corresponds to the shutter speed.

On the other hand, the shutter control voltage is high and the comparator 2
When the high level period of the output of 5 is longer than the video period (hereinafter referred to as the high speed shutter region), the reset pulse RS is output during the video period, and the output of the comparator 25 becomes high level during the vertical blanking period. The high level reset pulse SUB is output for a corresponding period. That is, O
The R gate 29 outputs a reset pulse SUB that is continuously controlled in the high speed shutter region. For example, by comparing the shutter control voltage V _b (D in FIG. 3) with a sawtooth wave, a comparator 25 that inverts to a low level during the vertical blanking period.
When the comparative output (G in FIG. 3) is obtained, H in FIG.
As shown in, a pulse is output as the reset pulse RS also in the vertical blanking period, and the pulse width changes according to the comparison output. Then, the pulse from the changes to the low level, then the charge period T _b to the image read-out pulse SG rises accumulates. This accumulation time T _b corresponds to the shutter speed.

Thus, the shutter speed control circuit 20 is
For example, when the subject is dark and the shutter speed is low, 1H is set based on the output level of the CCD 1 during the video period.
Drive circuit 18 reset pulse SUB controlled in units
Image reading pulse S after being supplied to the substrate of CCD 1 via the final reset pulse SUB.
The charge accumulation time until G is supplied is controlled in 1H units.

On the other hand, for example, when the subject is bright and the shutter speed is increased, the reset pulse SUB continuously controlled based on the output level of the CCD 1 during the vertical blanking period that does not affect the reading of the image pickup signal. It is supplied to the substrate of the CCD 1 through the drive circuit 18, and the charge accumulation time from the supply of the final reset pulse SUB to the supply of the image reading pulse SG is continuously controlled.

Then, the image pickup signal from the CCD 1 whose charge storage time is controlled according to the shutter speed as described above is supplied to the signal processing circuit 4 through the AGC circuit 3 so that an image conforming to the NTSC system or the like is obtained. It is converted into a signal and this video signal is taken out from the terminal 5.

According to the shutter control signal generating means SC of such an embodiment, when the shutter speed is changed, the level gradually changes from the shutter control level according to the current shutter speed to the shutter control level according to the target shutter speed. Since the level of the shutter control signal changes coarsely at high speed at first and then finely changes at low speed, it is easy to set the shutter speed, and the shutter speed can be set in many steps.

Further, a sawtooth wave to be compared with the shutter control voltage in the high speed shutter region, that is, the vertical blanking period,
Compared to the saw-tooth wave compared in the low speed shutter region, the potential increase rate is large and the slope is steep. Therefore, the resolution in comparison in the high speed shutter region is higher than that in the low speed shutter region.
Therefore, it is possible to control the shutter speed with high accuracy in the high shutter speed range. Further, since the peak of the sawtooth wave is detected and the shutter control voltage is made to converge non-linearly to this peak detected value, when the shutter control voltage is in the vicinity of the peak value of the sawtooth wave, abrupt fluctuations occur. Is suppressed, and the shutter speed does not suddenly fluctuate when the shutter speed is very high. Furthermore, when the central processing unit 1 converts the shutter control voltage data into PWM waves,
Since the conversion is performed with the non-linear characteristic, the accuracy of the shutter speed which is very high is improved from this point as well.

[0036]

According to the present invention described above, it is possible to obtain a shutter speed control apparatus for a solid-state image pickup device in which the shutter speed can be easily set and the shutter speed can be set in many steps.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of a shutter speed control circuit of the embodiment.

FIG. 3 is a timing chart for explaining the operation of the shutter speed control circuit.

FIG. 4 is a curve diagram showing a detection characteristic used for explaining the operation of the shutter speed control circuit.

FIG. 5 is a circuit diagram showing an equivalent circuit (1) of the shutter speed control means of the embodiment.

FIG. 6 is a circuit diagram showing an equivalent circuit (2) of the shutter speed control means of the embodiment.

FIG. 7 is a block diagram showing a conventional example of a shutter speed control device for a solid-state image sensor.

[Explanation of symbols]

 1 CCD SC Shutter Control Signal Generation Means 11 Seesaw Volume 15 Central Processing Unit 20 Shutter Speed Control Circuit 25 Comparison Circuits 27-29 Gate Circuit 30 Sawtooth Wave Generation Circuit 40 Detection Circuit

Claims (2)

[Claims] 1. A shutter control signal generation means for generating a shutter control signal whose level gradually changes from a shutter control level according to a current shutter speed to a shutter control level according to a target shutter speed when the shutter speed is changed, The shutter control signal from the shutter control signal generating means and a reset pulse supplied during the vertical blanking period reset pulse to a reference potential every one vertical period according to the level comparison result of the sawtooth wave signal. And a shutter speed control circuit for controlling the storage time of the solid-state image sensor according to the generation period of the reset pulse by supplying the reset pulse to the solid-state image sensor. Shutter speed controller. 2. The shutter speed control device for a solid-state image pickup device according to claim 1, wherein said shutter control signal generating means is composed of a pressure-sensitive resistance voltage divider to which a DC voltage is applied.