JPH036542A - Image pickup device - Google Patents

Abstract

PURPOSE:To simplify the circuit constitution by generating a gain control signal for a variable gain control circuit and a stop control signal for a driving part to drive a stop, and adding an offset in a stop opening direction. CONSTITUTION:The device consists of means 23 and 25 which generate the gain control signal for the variable gain control circuit 5, means 23 and 26 which generates the stop control signal for the driving part 9 for driving the stop 2, and a means 28 which adds the offset in the opening direction of the stop 2. Then gain control operation for an AGC amplifier 5 is as fast as or faster than stop control operation and the stop control signal for the driving part 9 is given the offset in the opening direction of the stop 2, so the stop control operation is performed in a stationary state preferentially to the gain control. Consequently, the stop 2 and AGC amplifier 5 are controlled with the one control signal and the circuit constitution is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an imaging device that automatically controls an aperture value and performs AGC control of the level of an imaging signal.

[Summary of the invention]

The present invention includes an aperture that limits the amount of incident light that enters the image sensor, and a variable gain control circuit that corrects the signal level of the image signal from the bridge image element, and includes an output signal or an input signal of the variable gain control circuit. In an imaging device that controls the gain of an aperture and a variable gain control circuit based on the level of a signal, means for forming a gain control signal for the variable gain control circuit, and aperture control for a drive unit for driving the aperture. By providing means for forming a signal and means for adding an offset in the direction in which the aperture opens, the aperture control is controlled by AG.
This imaging device operates preferentially to CI11'4B and has a simple circuit configuration.

[Conventional technology]

2. Description of the Related Art In imaging devices such as television cameras, devices are known that include an automatic aperture control device and an AGC circuit and automatically control an imaging signal to an appropriate level. FIG. 4 shows an example of such a conventional imaging device.

Imaging light that has passed through a lens 1 and an aperture 2 is incident on a solid-state imaging device 3 such as a CCD. The light-receiving surface of the solid-state image sensor 3 is provided with color filters of three primary colors or complementary colors. Signal components of each pixel of the solid-state image sensor 3 are supplied to a sample-and-hold circuit 4, and an imaging signal is output from the sample-and-hold circuit 4 at the timing of rask scanning.

This image pickup signal is supplied to the AGC amplifier 5 and the detection circuit 6. The detection circuit 6 extracts the average value of the image signal. The output signal of the detection circuit 6 is supplied to the comparison circuit 7,
A comparison output corresponding to the difference between the average value of the imaging signal and the reference voltage source 8 is formed from the comparison circuit 7, and this comparison output is sent to the drive unit 9.
is supplied to

The drive unit 9 includes a motor for varying the aperture 2 and a drive circuit thereof. The higher the level of the imaging signal is, the larger the value of the aperture 2 is, and the imaging signal output from the sample and hold circuit 4 is controlled to be below a predetermined signal level.

The output signal of the AGC amplifier 5 is taken out as an imaging output and is also supplied to the detection circuit 10.

The average value of the output signal of the AGC amplifier 5 is obtained from the detection circuit 10, and this average value and the reference voltage source 11 are connected to the comparison circuit 12.
is supplied to A gain control signal for controlling the gain of the AGC amplifier 5 is generated from the comparator circuit 12 .

In an imaging device in which automatic aperture control and AGC control are applied to an image signal, aperture control is usually given priority over AGC control in order to improve the S/N ratio of the image signal. In other words, even if the aperture 2 is opened to the maximum, the gain of the AGC amplifier 5 is controlled to be large (when the object is dark (when the amount of light is insufficient)).

[Problem to be solved by the invention]

The conventional imaging device shown in FIG.
In order to control the GC amplifier 5, a detection circuit 6.10, a comparison circuit 7.11, and a reference voltage source 8.12 are required, respectively, and the circuit configuration has the disadvantage of being complicated.

In order to solve this problem, the applicant of the present application has already proposed an imaging device that can control the aperture and AGC amplifier with one control signal, as shown in Japanese Patent Application No. 63-208825. There is.

An object of the present invention is to provide an improved imaging device based on the previously proposed system.

[Means to solve the problem]

The present invention includes an aperture 2 that limits the amount of incident light that enters the image sensor 3 and a variable gain control circuit 5 that corrects the signal level of the image signal from the image sensor 3. An imaging device configured to control the gains of the aperture 2 and the variable gain control circuit 5 based on the level of the output signal or the input signal, comprising: means 23, 25 for forming a gain control signal for the variable gain control circuit 5; 2, and means 28 for adding an offset in the direction in which the diaphragm 2 opens.

(Function) The gain control operation for the AGC amplifier 5 is said to be equal to or faster than the aperture control operation.The aperture control signal for the drive unit 9 for driving the aperture 2 Therefore, on a regular basis, the aperture control operation takes priority over the gain control.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. In Figure 1, 1 is the lens system, 2 is the aperture,
3 indicates a solid-state image sensor such as a COD. The opening state of the diaphragm 2 can be controlled by a drive unit 9 consisting of a motor and a drive circuit, and an diaphragm control signal SCI is supplied to the drive unit 9.

The output signal of the solid-state image sensor 3 is supplied to a sample hold circuit 4, and the sample hold circuit 4 outputs an image signal at the timing of the rask scan.

The output signal of the sample hold circuit 4 is supplied to the AGC amplifier 5. The gain of the AGC amplifier 5 is controlled by the AGC control signal SC2 so that its output signal has a predetermined level. The output signal of the AGC amplifier 5 is output as an imaging signal and is also supplied to the A/D converter 21. The output signal of the A/D converter 21 is supplied to an integrating circuit 22. The integrating circuit 22 digitally integrates the image pickup signal converted into a digital signal, and an output signal corresponding to the average value of the I-most image signal is obtained from the integrating circuit 22.

The output signal of the integrating circuit 22 is supplied to a comparing circuit 23 and compared with reference data REF from a reference data generating circuit 24. Comparison circuit 23 is provided to compare the output signal of integration circuit 22 and reference data REF from reference data generation circuit 24 . The output signal of comparison circuit 23 is supplied to integration circuits 25 and 26. The output signal of the integrating circuit 25 is supplied to the D/A converter 27.
An analog AGC III control signal SC2 is generated from the AGC control signal SC2, and the gain of the AGC amplifier 5 is controlled by the AGC control signal SC2.

The output signal of the integration circuit 26 is supplied to the addition circuit 28, and the bias signal Da is added to the output signal of the integration circuit 26 in the addition circuit 28. The output signal of the adder circuit 28 is supplied to a D/A converter 29. The D/A converter 29 generates an aperture control signal SCI, and the aperture control signal SCI is supplied to the drive unit 9. The bias signal Da may be added on the output side of the D/A converter 29.

An example of the drive section 9 will be explained with reference to FIG. For example, a DC motor is provided to drive the aperture 2. 3
1 represents the rotor of the DC motor, 32 represents the drive coil, and 33 represents the control coil. When signals with the polarities shown in FIG. 2 are applied to the drive coil 32 and control coil 33, the motor is driven in the direction in which the diaphragm 2 opens.

The aperture control signal SCI from the D/A converter 29 is connected to the resistor 34.
The signal is supplied to one input terminal of the operational amplifier 35 via. A DC power supply 37 is connected to the other input terminal of the operational amplifier 35 via a resistor 36. This DC power supply 37
provides the bias signal Db to the operational amplifier 35. A resistor 38 and a capacitor 39 are inserted between one input terminal and an output terminal of the operational amplifier 35. The operational amplifier 35 generates an output signal corresponding to the difference between the aperture control signal SCI and the bias signal Db, and the output signal of the operational amplifier 35 is supplied to one terminal of the drive coil 32.

The output signal of operational amplifier 35 is supplied to one input terminal of operational amplifier 41 via resistor 40 .

The other input terminal of this operational amplifier 41 is connected to a DC power supply 3.
A bias signal Db is supplied from 7.

Between one input terminal and the output terminal of the operational amplifier 41,
A resistor 42 and a capacitor 43 are inserted. The output signal of the operational amplifier 41 is supplied to the other end of the drive coil 32 . One end of the control coil 33 is supplied with an aperture control signal SCI via a resistor 34, and the other end is supplied with a resistor 3.
A bias signal Db via 6 is supplied.

An example of the values of each element of the drive section 9 is shown below.

Resistor 34, Resistor 36: lOkΩ, Resistor 38: IMΩ, Capacitor 39, Capacitor 43: 0. IF resistance 40,
Ω in the resistor 42 j 22, and the human power signal V of the operational amplifier 35 in the drive section 9 described above.
The driving direction of the aperture 2 is determined by the magnitude relationship of a and vb. In other words, when (Vb>Va), the motor rotates at low speed in the direction in which the diaphragm 2 opens, and when (Vb<Va), the motor rotates at low speed in the direction in which the diaphragm 2 closes, and (Va =V
In case b), the motor is stationary. The diaphragm 2 has a mechanical limit value in both the opening direction and the closing direction.

In one embodiment of the present invention, the bias signal Da (considered to be converted into an analog value) and the bias signal Db
are not equal, and these bias signals are (Da<D
b), and an offset of the amount (Db-Da) is added to one input signal Va of the operational amplifier 35. In other words, this offset is in the direction in which the aperture 2 opens. Even if the gain control operation has priority over the aperture control operation in a transient state due to the offset, the aperture control operation has priority over the gain control operation in a steady state. In a transient state, the response speed of the AGC control loop is slightly faster than the response speed of the aperture control loop, so the gain control operation takes priority over the aperture control operation.

In FIG. 3A, 50 indicates a gain change of the AGC amplifier 5 with respect to the gain control signal SC2.

When the subject is bright and the level of the imaging signal from the AGC amplifier 5 is high, the gain is fixed to G+*in. Furthermore, when the subject is dark, the level of the imaging signal is low, and the level of the ACCM control signal SC2 is also low, and at this time, the gain G of the AGC amplifier 5 is increased so as to increase the level of the imaging signal. When the subject is darker,
The gain of the AGC amplifier 5 is fixed at the maximum G max.

In the above embodiment, the operation over time when the subject changes from a bright object to a dark object will be described with reference to FIG. 3B. In FIG. 3B, the solid line 51 indicates the F value of the aperture (
When the F number is minimum, the aperture is opened to the maximum extent, and when the F number is maximum, the aperture is opened to the maximum extent.

At the timing tl, the subject is bright, the gain of the AGC amplifier 5 is set to the minimum value Ga1n, and the level of the imaging signal is controlled to a predetermined level with the aperture 2 in a predetermined aperture state. At timing t2, when the subject changes to a dark one,
The gain is increased by the gain control signal SC2, and the aperture 2 is controlled in the open direction. Since the response speed of the AGC loop is fast, the gain increases faster than the change in the aperture 2. However, there is the above-mentioned offset. Therefore, the gain control signal S
When C2 becomes zero, the aperture control motor does not stop and continues to be driven in the opening direction. The F value of aperture 2 is Fs
At timing t3 when in reaches, the aperture stops changing mechanically. At or after timing t3, the gain is controlled to an appropriate value, and the level of the imaging signal is controlled to a predetermined level.

Unlike the example shown in FIG. 3B, when the aperture 2 is not opened to the maximum, the gain is set to Gs+in in a steady state, and the level of the imaging signal is controlled by the aperture 2 to a predetermined level. In this way, the aperture control operation is performed preferentially over the AGC operation.

In addition, depending on the average value of one image, aperture 2 or AGC
In addition to forming the control signal for the amplifier 5, one image may be divided into a plurality of regions, the average value of the imaging signal of each region may be calculated, and weighting may be performed according to the region. For example, the adverse effects of backlight may be removed by increasing the weight of the average value in the central region. Further, digital control may be performed by software processing of a microcomputer, or, of course, control signals for the aperture and AGC amplifier may be formed by analog circuits.

〔Effect of the invention〕

According to this invention, since the aperture control signal has an offset in the direction in which the aperture opens, the aperture control operation is performed preferentially over the AGC operation. Further, since the present invention controls the aperture and the AGC amplifier with one control signal,
It has the advantage of a simple circuit configuration.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a connection diagram of an example of the drive unit of the embodiment of the invention, and Fig. 3 is a route diagram used to explain the operation of the embodiment of the invention. , FIG. 4 is a block diagram of a conventional evacuation device. Explanation of main symbols in the drawings 2: Diaphragm, 3: Solid-state image sensor, 5: AGC amplifier, : Drive unit, 8: Adder circuit for adding bias signal, : Drive coil, : Control coil.

Claims (1)

[Scope of Claims] An aperture that limits the amount of incident light that enters the image sensor, and a variable gain control circuit that corrects the signal level of the image signal from the image sensor, the output of the variable gain control circuit In the imaging device, the gain of the aperture and the variable gain control circuit is controlled based on the level of a signal or an input signal, comprising: means for forming a gain control signal for the variable gain control circuit; and a means for driving the aperture. An imaging device comprising: means for forming an aperture control signal for a drive unit for the purpose of the image capture; and means for adding an offset in the opening direction of the aperture.