JP2992174B2 - Video camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera, for example, a video camera for controlling the iris of a digital camera. The present invention relates to a video camera in which is controlled in an appropriate state.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a conventional video camera. In FIG. 5, reference numeral 21 denotes a CCD (Charge Coupled Device), 22 denotes an iris, and 23 denotes an AGC (Automatic Camera).
tic GainControl: Automatic gain control) circuit, 24 is A / D
A conversion circuit, 25 is a timing generation circuit, 26 is a block-by-block accumulation circuit, 27 is a maximum value detection circuit, 28 is a photometric value calculation circuit, 29 is a D / A conversion circuit, 30 is an operation (OP) amplifier, and 31 is an iris. The drive circuit 32 is a backlight correction switch.

An A / D converter 24 converts the digital signal into a digital signal, and a block-by-block accumulation circuit 26 and a maximum value detection circuit 27 output accumulated data for each block and the maximum value of the entire screen. The timing generation circuit 25 is a circuit for generating a timing control signal for a block. As an example, FIG. 2 shows the division of a 4 × 4 block, and the description will be made based on this. In the photometric value calculation circuit 28, the weighted photometric value is obtained by multiplying the 16 block accumulated data by a coefficient and adding them together. For example, by increasing the coefficient in the lower part, lower priority photometry is performed. This value and the value output from the maximum value detection circuit 27 are multiplied by a coefficient and added to obtain a total photometric value. Increasing the specific gravity of the maximum value approaches the peak photometry, and decreasing the specific gravity results in the weighted average photometry. This photometric value is D
/ A conversion circuit 29 converts the reference voltage and the OP amplifier 30
The iris and AGC control output can be obtained by the comparison.

[0004]

However, in the conventional method, since the photometry is performed on the entire screen, the person becomes dark especially in a backlight state, and the operator inserts a backlight correction SW to correct this. Since the reference voltage needs to be changed and the amount of change is a fixed value, there is a drawback that proper correction may not be performed. In addition, there is also a disadvantage that a person becomes overexposed in a spot light (excessive light state).

The present invention has been made in view of such circumstances, and a video camera which automatically determines whether a screen state is backlit or over-lit and controls an iris to an appropriate state. It is intended to provide.

[0006]

According to the present invention, there is provided an A / D converter for converting a video signal obtained by an image sensor into a digital signal, and an A / D converter obtained by the A / D converter. Accumulating means for dividing the image data of one screen composed of digital signals into a plurality of blocks and accumulating the image data of each block to form accumulated data for each block; A calculating means for multiplying the accumulated data and the maximum value of each block by a desired coefficient to form the added photometric value data; and Reference brightness setting means for judging the light state from the data of the block and changing the photometry reference value, and control means for controlling an iris and an automatic gain control circuit based on the photometry value data and the reference brightness. It is obtained by comprising the.

[0007]

The image signal obtained by the image pickup device is converted into a digital signal by A / D conversion means, and the image data for one screen composed of the obtained digital signal is divided into a plurality of blocks, and the block data is obtained by the accumulation means. Each image data is accumulated to form accumulated data. The accumulated data and the maximum value in one screen are each multiplied by a predetermined coefficient and added to form photometric value data. It is determined from the data of the block whether the central part of the screen is in a backlight state or an over-light state, and the photometric reference value is changed. By controlling the iris and the AGC based on the photometric data and the reference luminance, an appropriate iris operation can be realized.

[0008]

Embodiments will be described below with reference to the drawings. FIG. 1 is a block diagram for explaining an embodiment of a video camera according to the present invention. In the drawing, reference numeral 1 denotes a CCD (Charge C).
oupled Device: charge-coupled device), 2 is an iris, 3 is an AGC (Automatic Gain Control) circuit, 4 is an A / D conversion circuit, 5 is a timing generation circuit, 6
Is an accumulation circuit for each block, 7 is a maximum value detection circuit, 8 is a photometric value calculation circuit, 9 is a D / A conversion circuit, 10 is an OP amplifier,
11 is an iris drive circuit, 12 is a backlight / over-light detection circuit, 13 and 14 are block data averaging circuits, 15 is a comparator, and 16 is a reference value generation circuit.

In this embodiment, as shown in FIG. 2, a captured two-dimensional image is divided into 16 blocks, luminance data included in each of the blocks is added, and a maximum value is calculated and photometry is performed. Data. The signal is converted into a digital signal by the A / D conversion circuit 14, and the block-by-block accumulation circuit 6
The maximum value detection circuit 7 outputs the accumulated data for each block and the maximum value of the entire screen. Timing generation circuit 5
Is a circuit for generating a block timing control signal. The photometric value calculation circuit 8 multiplies the 16 block accumulated data by a coefficient and adds them to obtain a load photometric value. For example, by increasing the coefficient in the lower part, lower priority photometry is performed. The value output from the maximum value detection circuit 7 is multiplied by a coefficient and added to the photometric value to obtain a total photometric value.

On the other hand, the block-by-block accumulation circuit 6 and the maximum value detection circuit 7 also output data to the backlight / excessive light detection circuit 12. A typical example of the backlight state is a state in which the person in the center sinks dark as shown in FIG. Also,
The over-directed light state is the reverse of this, in which the surroundings are completely dark and the person is floating white. Backlight / excessive light detection circuit 12
In such a state, the blocks f, g, j, k, n, and o are compared with other blocks according to the data of each block and the location of the maximum value, and if it is determined that the block is dark, the backlight is corrected by the comparison value. As described above, the data is changed in the reference value generating circuit 16 as shown in FIG. 4, and in the case of over-direct light, the reverse operation is performed. This determination may be made by a circuit or a microcomputer. The photometric value output from the photometric value calculation circuit 8 is converted by the D / A conversion circuit 9 and compared with the reference voltage output from the reference value generation circuit 16 by the OP amplifier 10 to obtain an appropriate iris and AGC control output. Can be

[0011]

As is apparent from the above description, the present invention has the following effects. That is, the backlight or over-directed light state is automatically detected based on the accumulated data and the maximum value data for each block to change the reference voltage, so that appropriate iris control can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of a video camera according to the present invention.

FIG. 2 is a diagram showing an example of block division of a two-dimensional image captured according to the present invention.

FIG. 3 is a diagram showing an image in a backlight state according to the present invention.

FIG. 4 is a diagram showing an image in a backlight state according to the present invention.

FIG. 5 is a configuration diagram of a conventional video camera.

[Explanation of symbols]

1 ... CCD (Charge Coupled Device), 2 ... Iris, 3 ... AGC (Automatic Gain Con
trol: automatic gain control) circuit, 4 ... A / D conversion circuit, 5 ...
Timing generation circuit, 6: block-by-block accumulation circuit, 7: maximum value detection circuit, 8: photometric value calculation circuit, 9: D / A conversion circuit, 10: OP amplifier, 11: iris drive circuit, 12
... Backlight / excessive light detection circuit, 13, 14 block data averaging circuit, 15 comparator, 16 reference value generation circuit.

Claims (1)

(57) [Claims] An A / D converter for converting a video signal obtained by an image sensor into a digital signal, and image data for one screen consisting of the digital signal obtained by the A / D converter are divided into a plurality of blocks. Accumulating means for forming accumulated data for each block by accumulating image data of each block; detecting means for detecting a maximum value in one screen; The arithmetic means for multiplying the values by desired coefficients and forming the added photometric value data, and judging from the data of the block whether the central portion of the screen is in a backlit state or an over-directed state, and a photometric reference value is determined. A video camera comprising: reference brightness setting means for changing; and control means for controlling an iris and an automatic gain control circuit based on the photometric value data and the reference brightness.