JPS5999880A - Image pickup device - Google Patents

Abstract

PURPOSE:To attain suitable photographic pickup to flush and exposure correction by opening a loop of an automatic gain control circuit at flush pickup and making the gain to a prescribed value to reflect correctly the intension of a photographer. CONSTITUTION:An output of a CCD101 as an image pickup means is inputted to an automatic gain control circuit AGC102, the output is changed by an output of the CCD101 to control it to almost constant level. The output of the AGC102 is processed by a signal processing circuit 103 and inputted to a recorder 108. Further, the AGC102 is provided with a control terminal 105 connected to a switch 104 interlocked with an exposure storage button, a control terminal 110 connected to a switch 107 interlocked with an exposure correction switch, and a control terminal 106 controlling the flush circuit. Then, the potential at a terminal 106 is brought to the vicinity of a ground potential, the circuit of the AGC102 is opened, allowing to reflect correctly the intension of the photographer and to attain suitable pickup to the flush and exposure correction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an imaging device that converts a subject image into an electrical signal using an imaging device such as an imaging tube or a CCD.

<Description of Prior Art> Conventionally, in an imaging device using an imaging device such as an image pickup tube or a CCD, the dynamic range of the imaging device is narrow, and the output level of the imaging device changes significantly even with a slight exposure shift. . Therefore, in order to electrically correct this, an automatic gain control circuit (hereinafter referred to as AGC) is used to keep the level of the signal transmitted to the signal processing and recording circuit almost constant regardless of the magnitude of the output from the image sensor. I was keeping it. However, with such a device, if you try to memorize the exposure (AE lock) or make exposure compensation when shooting against the light, the AG
It has the disadvantage that these operations cannot be performed because C cancels it out. Furthermore, it has the disadvantage that it cannot cope with cases where the photometric conditions before photography and the exposure conditions during photography are completely different, such as in flash photography.

<Object of the Invention> The present invention has been made in view of the drawbacks of the above-mentioned conventional device.
The object of the present invention is to provide an imaging device that can always accurately reflect the photographer's intentions, even in exposure-compensated iE photography and flash photography.

<Description of Examples> Hereinafter, the content of the present invention will be explained in detail with reference to the drawings. Figure 1 is a control circuit diagram showing one embodiment of the present invention. In the figure, 1 is a battery that is an E source, a two-digit oscillation booster circuit, and 3 is a main capacitor connected in parallel with this. ] A series circuit consisting of the lamp 4 and the resistor 5, and a series circuit consisting of the flash discharge tube 9 and the light amount control circuit 1o are connected. Furthermore, a series circuit of a resistor 6 and a base-emitter of a transistor 7 is connected in parallel with the resistor 5. 8 is a synchro circuit, and 11 is a photometric circuit. 1 to 11 above are circuits of a known flashlight emitting device, and 2 shown in blocks.
, 8, 10, 11, etc., can be easily constructed using known circuit means, so a detailed explanation of the contents will be omitted.

101 is a COD as an imaging means and its output is AGC1
The power connected to 02 is 1, and the AGC 102 has a gain of 10
1, and is controlled so that the output of the AGC 102 is approximately at a constant level regardless of the magnitude of the output of the image sensor 101. The output of the AGC 102 is input to a signal processing circuit 103, and is further recorded in a recording bag @108.

AGC102 has #'13 control terminals 105°106.
There are 110. The terminal 105 is connected to the ground potential via a switch 104 that is turned on in conjunction with an AE lock button (not shown) provided in the device operation section (not shown), and when this terminal 105 is grounded, the gain of the AGC 102 is is terminal 1
It is fixed to the value immediately before 05 is grounded. Terminal 106 is connected to the collector of transistor 7 and
Alternatively, when the terminal 106 drops to near the ground potential by turning on the switch 107, the gain of the AGC 102 is fixed to a certain constant value that is completely unrelated to the previous value. terminal 1
10 is connected to a switch 107 linked to an exposure compensation switch, and is input to a control terminal 110 of the AGC 102.

FIG. 2 is a detailed circuit diagram of the AGC 102 of this embodiment.

In the figure, PI is an input terminal.

PO is the output terminal, AMP is the amplifier, RG is the smoothing circuit, S
H is a sample hold circuit, SL is a fixed level voltage output circuit, MX is a multiplexer, and Q is an impedance conversion FET.

R1 and R2 are voltage dividing resistors.

During normal shooting, the multiplexer MX is connected to the smoothing circuit R.
G is selected, a voltage corresponding to the output signal level f from the CCD is transmitted to FETQ 72, and the gain is automatically controlled. 1st AG and C carry out normal operation.

Then, the AE lock button is pressed, Z) and the terminal 106 are grounded, the sample hold circuit SH bolds the output of the smoothing circuit RG at that time, and the output of the multiplexer MX beam and sample hold circuit SH becomes Th F E T
Q IC is transmitted.

Therefore, the AGC benefit is fixed at the moment the AE lock button is pressed. Note that the Zumble timing may be slightly shifted as long as it is before or after the button is pressed.

Also, during flash photography, the multiplexer MX (
In order to transmit the output of the M constant level output circuit SL to the FETQ, the gain of the AGC is fixed to a predetermined value.

Further, during exposure correction, the terminal 110 is grounded, and the multiplexer MX divides the output of the smoothing circuit RG by resistors R1 and R2 at a predetermined ratio and transmits the value to the FETQ.

With this configuration, the gain of the AGC is shifted by a predetermined amount.

Furthermore, by configuring the resistor R2 as a variable resistor, the exposure correction amount, that is, the gain shift amount can be varied.

One embodiment of the present invention has the above-mentioned configuration, and its operation will be explained below.

First, the case of AE lock will be explained.

For example, if you want to take a picture of a person etc. with backlight, approach the person and point the lens at the person to avoid backlight.
When the switch button is pressed, the switch 104 is turned on with the interlock j-, and the AGC control terminal 105 is grounded. Therefore,
The gain of the ACC 102 is fixed at a value that provides appropriate exposure for the person. Even if you move away from the person and incorporate the person as part of the overall scene, the exposure will be adjusted to the main subject, ignoring the overall exposure, and the AGC102
Since the gain of A remains fixed, a signal corresponding to the proper exposure of the person is obtained from the output of A (C1O2), and the AGC becomes obstructed by the AE lock.

Next, we will discuss the case of flash photography.

When the flash is connected and a power switch (not shown) is turned on, the booster circuit 2 operates and the main capacitor 3 is charged. When the charging voltage of the main capacitor 3 reaches a sufficient value for light emission, the neon lamp 4 lights up and the resistor 6
A current flows through K, which supplies the base current to transistor 7, turning on transistor 7, which causes AG
The C control terminal 106 becomes close to the ground potential, and the AGC 10
The gain of 2 is fixed at a constant value. On the other hand, a current flows through the resistor 5, and the voltage generated across the resistor 5 causes the synchro circuit 8 to
becomes operational. In this state, a photographing operation is performed, and when a synchro switch (not shown) is turned on, the synchro circuit 8 operates to trigger the flash discharge tube 9 and start flash emission. The light reflected from the subject is photoelectrically converted and integrated by the photometry circuit, and when this becomes equivalent to the appropriate exposure amount, the light control circuit 10
to stop the light emission.

The amount of flash light from the flash is controlled so that the amount of exposure of the subject is appropriate, and the gain of the AGC 102 is also controlled to an appropriate value, so that appropriate photographs can be taken even in flash photography.

Next, the case of exposure compensation will be described. AE lock is convenient and accurate when you can get close to the subject and meter the subject with the subject in full screen, but there are some subjects that you cannot get close to, and in such cases, you need to adjust the gain from a value that will give an appropriate overall exposure level. By shifting, exposure compensation is performed to properly capture the desired subject. In this case, the switch 107 is turned on in conjunction with the exposure correction, the potential of the terminal 110 is set to the ground level 17, and the gain of the AGC 102 is shifted so as to obtain the correct output for the appropriate exposure amount. By doing this, the gain is shifted with respect to the appropriate gain for the entire scene, and the target object can be imaged with appropriate exposure.

<Description of Effects> As explained above, by controlling the AGC according to the shooting mode, it is possible to take pictures that are suitable for people who use AE lock, flash, and exposure compensation.

[Brief explanation of the drawing]

FIG. 1 is a control circuit diagram of the single-image device of this embodiment. FIG. 2 is a detailed circuit diagram of the AGC 102. In the figure, 1 is a CCD, and i02 is AGC. 103 is a signal processing circuit, 104 is a switch that is turned on in conjunction with AE lock, 107 is a switch that is turned on in conjunction with exposure compensation, and AMP is an amplifier. RG is a smoothing circuit, and SL is a 1IIil constant level output circuit. SH indicates a sample hold circuit, MXH-multiplexer, voltage dividing resistors R1 and R2, and Q indicates 1·'ET, respectively. Applicant Keyanon Co., Ltd.

Claims (3)

[Claims] (1) In an imaging device having an imaging means that converts a subject image into an electrical signal, and an automatic gain control circuit that automatically controls the gain of the electrical signal, the control loop of the automatic gain control circuit is opened during flat shooting. , an imaging device characterized in that the gain is set to a predetermined value. (2) An imaging apparatus having an imaging means for converting a subject image into an electrical signal and an automatic gain control circuit for automatically controlling the gain of the electrical signal is provided with a switch for fixing the C1 exposure, and the operation of the switch is An imaging apparatus characterized in that the gain of the control circuit is fixed to a value before and after the switch is activated in conjunction with the gain of the control circuit. (3) An imaging device having an imaging means for converting a subject image into an electrical signal, and an automatic gain control circuit for automatically controlling the gain of the electrical signal, the imaging device having an operating member for correcting exposure, and operating the operating member. An imaging device characterized in that the gain of the control circuit is shifted by.