JP2507163Y2 - Video camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a video camera, and more particularly to a technology for backlight compensation by controlling an iris of the video camera.

[Prior Art] FIG. 5 shows an example of a circuit configuration of a video camera.

In the figure, image light from a subject (not shown) passes through an image pickup lens 1 and an iris 2 and then an image pickup device 3, for example,
It is supplied to the CCD solid-state image sensor. The output signal of the image sensor 3 is supplied to a sample hold circuit (S / H circuit) 4, and the S / H circuit 4 outputs an image signal.

The image pickup signal output from the S / H circuit 4 is supplied to the level detector 5 which constitutes the auto iris controller,
The detection signal is supplied to the iris driver 7 via the pre-controller 6. Then, the driver 7 supplies an iris drive voltage to the iris 2 to drive the iris 2. 6a is a semi-fixed resistor for presetting a reference value and the like.

FIG. 6 is a diagram showing the relationship between the iris drive voltage and the light quantity. In the normal mode, the iris drive voltage is changed as shown by the solid line a in the figure. As a result, below a predetermined illuminance, for example below 200 lux,
The iris drive voltage is maximized and the iris 2 is controlled to open.

In the backlight mode (backlight correction mode),
A control signal SCB is supplied from the terminal 8 to the pre-controller 6 so that the iris drive voltage changes as shown by the broken line b in FIG. That is, the iris drive voltage is uniformly increased regardless of the light amount level. In this case, in the normal mode, the iris drive voltage becomes maximum at the portion la where the iris operation is performed, and the iris operation is not performed.

The image pickup signal output from the S / H circuit 4 is supplied to the AGC amplifier 9. The output signal of the AGC amplifier 9 is supplied to the level detector 10 which constitutes the AGC circuit, and the detection signal thereof is supplied to the pre-controller 11. It should be noted that this detection signal changes so as to increase as the level of the output signal of the AGC amplifier 9 decreases.

An AGC control voltage is supplied from the pre-controller 11 to the AGC amplifier 9 to control its gain. Note that 11
a is a semi-fixed resistor for presetting the reference value and the like.

FIG. 7 is a diagram showing the relationship between the AGC control voltage and the light amount. In normal mode, as shown by the solid line a in FIG.
The control voltage is changed. As a result, when the iris 2 is opened, the AGC operation is performed except for the portion where the light amount level is below a predetermined level.

In the sensitivity up mode, the control signal SCG is supplied from the terminal 12 to the pre-controller 11 so that the AGC control voltage changes as shown by the broken line b in FIG. In this case, the AGC control voltage is uniformly increased regardless of the light amount level. In this case, AGC in normal mode
In the portion of lb where the operation is performed, the AGC control voltage becomes maximum and the AGC operation is not performed.

FIG. 8 shows the relationship between the signal level of the image pickup signal output from the AGC amplifier 9 and the light amount. Solid line a in FIG.
Shows the case of the normal mode, and the broken line b in the figure shows the case of the backlight mode and the sensitivity up mode in which the control signals SCB and SCG are supplied to the terminals 8 and 12.

Further, the image pickup signal output from the AGC amplifier 9 is supplied to the process circuit 13, and from this process circuit 13, the luminance signal Y and the color difference signals (red difference signal RY, blue difference signal B-
Y) is output.

The luminance signal Y output from the process circuit 13 is supplied to the encoder 16 via the γ correction circuit 14 and the amplifier 15,
A synchronization signal is added by this encoder 16.

Color difference signals RY and BY output from the process circuit 13
Is supplied to an encoder 16 and is subjected to quadrature two-phase modulation by the encoder 16 to form a carrier color signal C (color subcarrier frequency is 3.58 MHz, for example).

The luminance signal Y and the chrominance signal C output from the encoder 16 are supplied to the adder 17 and added, and the video signal output from the adder 17 is output via the amplifier 18 to a line output terminal.
Derived to 19.

The brightness signal Y output from the encoder 16 is also supplied to the electronic viewfinder 20.

[Problems to be Solved by the Invention] According to the example of FIG. 5, when the control signal SCB is supplied to the terminal 8 to set the backlight mode, the iris drive voltage increases and the iris 2 is controlled to open. Therefore, backlight compensation is performed. Further, when the control SCG is supplied to the terminal 12 to enter the sensitivity increasing mode, the AGC control voltage is increased and the gain of the AGC amplifier 9 is controlled to be increased, so that the sensitivity is increased.

By the way, in the example of FIG. 5, when the backlight mode is set, the iris drive voltage is uniformly increased regardless of the light amount level, and the following inconvenience occurs. For example, in a subject with high contrast (the surrounding brightness is high with respect to the dark part and the light amount level is large), the dark part is unlikely to be bright, and the effect of backlight compensation cannot be sufficiently obtained. For a subject with low contrast (the surrounding brightness is low with respect to the dark part and the light amount level is low), for example, the sixth
Corresponding to the part of la in the figure, the iris 2 becomes open, and it becomes too bright overall.

Further, in the sensitivity up mode, the AGC control voltage is uniformly increased irrespective of the light quantity level, so that the same inconvenience as in the above backlight mode occurs.

Therefore, in this invention, it is an object to make particularly good backlight correction.

[Means for Solving the Problems] The present invention provides an iris arranged on the front surface side of an image sensor, a level adjuster for adjusting the level of an image signal from the image sensor, and an output signal level of the level adjuster. A level detector for detection, a drive circuit for generating an iris drive signal for driving the iris according to the detection signal from the level detector, an AGC amplifier for adjusting the level of the image pickup signal from the image sensor, and an AGC amplifier AG to control the gain of
A level controller that controls the level of the C control voltage and a dynamic range controller that controls the dynamic range of the AGC control voltage are provided, and the level adjuster reduces the level of the image pickup signal to reduce the level of the image pickup signal to the iris drive signal. Backlight compensation operation that changes the level of the
The C control voltage is controlled according to the level of the image pickup signal, and the sensitivity increasing operation for expanding the dynamic range of the AGC control voltage by the dynamic range controller is controlled by one control signal.

[Operation] In the above-described configuration, when the backlight is corrected, the opening of the iris 2 is controlled according to the level of the image pickup signal, that is, the light amount level of the subject. Therefore, the opening of the iris 2 is uniformly controlled regardless of the light amount level. The inconvenience as in the past does not occur. For example, in a subject with high contrast, the iris 2 is widened to make the dark portion brighter. Also, for example, for subjects with low contrast,
The aperture of the iris 2 is made smaller and the overall brightness is suppressed.

Further, since the switches for setting the backlight mode and the sensitivity up mode can be used together, the number of switches can be reduced, and the operation can be extremely simplified.

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this example, the image pickup signal from the S / H circuit 4 is the amplifier 21
Is supplied to the level detector 5 which constitutes an auto iris controller. The gain of the amplifier 21 can be switched between 0 dB and -6 dB.

In the backlight and sensitivity up mode, the control signal SC is supplied from the terminal 22 to the amplifier 21. The gain of the amplifier 21 is 0 dB in the normal mode and -6 dB in the backlight and sensitivity up mode.

With the above configuration, in normal mode, the amplifier 21
The gain of is set to 0 dB. So in this mode,
The iris drive voltage changes as shown by the solid line a in FIG. This is the same state as the normal mode in the example of FIG. 5 (see the solid line a in FIG. 6).

On the other hand, in the backlight and sensitivity up mode, the gain of the amplifier 21 is set to -6 dB. Therefore, in this mode, the iris drive voltage changes as shown by the broken line b in the figure. That is, the iris drive voltage is increased according to the light amount level.

Further, in this example, the output signal of the level detector 10 forming the AGC circuit is supplied to the pre-controller 11 via the cathode / anode of the diode 23, the resistor 24 and the connection switch 25.

In the backlight and sensitivity up mode, the control signal SC is supplied from the terminal 22 to the connection switch 25. And
The connection switch 25 is turned off in the normal mode and turned on in the backlight and sensitivity up mode. As a result, in the backlight and sensitivity up mode, the detection signal of the level detector 10 is supplied as a control signal to the pre-controller 11 via the connection switch 25,
The AGC control voltage is increased according to the light amount level. Then, when the light amount level is reduced and the AGC control voltage is saturated, the diode 23 is turned off, which is substantially the same as the normal mode in which the connection switch 25 is off.

Further, the output signal of the pre-controller 11 is supplied to the AGC amplifier 9 as the AGC control voltage via the low illuminance gain controller 26.

In the backlight and sensitivity up mode, the control signal SC is supplied from the terminal 22 to the gain controller 26. In the gain controller 26, the dynamic range of the AGC control voltage is left unchanged in the normal mode, while the dynamic range is expanded after the AGC control voltage is saturated in the backlight and sensitivity up modes.

In the above configuration, the control signal SC is not supplied to the terminal 22 in the normal mode. Therefore, the connection switch 25
Is turned off and the gain controller 26
The dynamic range of the control voltage is not expanded.
Therefore, in this mode, the AGC control voltage changes as shown by the solid line a in FIG. This is the same state as the normal mode in the example of FIG. 5 (see the solid line a in FIG. 7).

On the other hand, in the backlight and sensitivity up mode, the control signal SC is supplied to the terminal 22. Therefore, the connection switch 25 is turned on so that the AGC control voltage is at the level of the image pickup signal,
Therefore, the gain of the AGC amplifier 9 is increased according to the light amount level. In this case, when the light amount level decreases as the level of the AGC control voltage becomes saturated, the diode 23 is turned off and the state becomes the same as in the normal mode. Further, the dynamic range of the AGC control voltage is expanded in the gain controller 26, and the AGC control voltage is further increased and the gain of the AGC amplifier 9 is further increased in the low illuminance portion lc where the light amount level is small.

FIG. 4 shows the relationship between the signal level of the image pickup signal output from the AGC amplifier 9 and the amount of light. Solid line a in FIG.
Shows the case of the normal mode, and the broken line b in the figure shows the case of the backlight in which the control signal SC is supplied to the terminal 22 and the sensitivity up mode.

As described above, according to this example, when the backlight is corrected, the opening of the iris 2 is controlled to be larger as the light amount level of the subject is larger. Therefore, the opening of the iris 2 is uniformly controlled regardless of the light amount level. Such inconvenience does not occur, and stable backlight compensation can be performed.

Further, according to this example, when the sensitivity is increased, the gain of the AGC amplifier 9 is controlled to increase as the light intensity level of the subject increases, so that the sensitivity is not increased unnecessarily and stable sensitivity is maintained. You can improve.

Further, in the low illuminance portion lc, the gain of the AGC amplifier 9 is further increased, so that it is possible to satisfactorily image a low illuminance subject.

Further, in both the backlight mode and the sensitivity up mode, the control signal SC may be supplied to the terminal 22.
That is, by supplying the control signal SC to the terminal 22, the backlight correction is performed when the light amount is equal to or more than the predetermined light amount, and the sensitivity is increased when the light amount is less than the predetermined light amount (see the broken line b in FIG. 4).
Therefore, according to this example, a switch for setting the backlight mode and the sensitivity up mode can be used together. As a result, the number of switches is reduced and the labor for processing is reduced, so that the cost can be reduced accordingly.

In the above-described embodiment, the gain of the amplifier 21 is set to -6 dB in the backlight and sensitivity up mode, but it is not limited to this value. The point is that in this mode, the level of the image pickup signal is suppressed and the iris 2 is controlled to open according to the light amount level.

[Effects of the Invention] As described above, according to the present invention, the opening of the iris is controlled according to the light amount level of the subject during backlight compensation, so that the opening of the iris 2 is uniformly controlled regardless of the light amount level. The inconvenience of the prior art does not occur, and stable backlight compensation can be performed.

Further, since the switches for setting the backlight mode and the sensitivity up mode can be used together, the number of switches can be reduced, and the operation can be extremely simplified.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIGS. 2 to 4 are diagrams for explaining the same, FIG. 5 is a block diagram of a conventional example,
FIG. 6 to FIG. 8 are diagrams for explaining this. 2 …… Iris 3 …… Image sensor 5, 10 …… Level detector 6, 11 …… Pre-controller 7 …… Iris driver 9 …… AGC amplifier 13 …… Process circuit 16 …… Encoder 21 …… Amplifier 23 …… Diode 24 …… Resistor 25 …… Connection switch 26 …… Low light gain controller

Claims (1)

(57) [Scope of utility model registration request] 1. An iris arranged on the front side of an image pickup device, a level adjuster for adjusting the level of an image pickup signal from the image pickup device, and a level detector for detecting the level of an output signal of the level adjuster. , A drive circuit that generates an iris drive signal for driving the iris according to the detection signal from the level detector, an AGC amplifier that adjusts the level of the image pickup signal from the image pickup device, and a gain of the AGC amplifier A level controller for controlling the level of the AGC control voltage for controlling the AGC control voltage and a dynamic range controller for controlling the dynamic range of the AGC control voltage are provided, and the level adjuster reduces the level of the imaging signal. Backlight correction operation for changing the level of the iris drive signal with respect to the level of the image pickup signal, and the AGC control voltage for the image pickup signal by the level controller. And a sensitivity increasing operation for expanding the dynamic range of the AGC control voltage by the dynamic range controller and controlling with a single control signal.