JPH10210347A - Ae control signal processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for the development of software used for AE control and to reduce the number of parts by permitting a signal processing circuit, which digitally processes the output signal of an image-pickup element to calculate an automatic exposure(AE) control signal from a video signal and generating a timing signal for controlling the shutter speed and the output gain of the image-pickup element, based on the signal. SOLUTION: In an AR control signal processor 3, a signal processing circuit 5 processes the inputted digital signal and sends the video signal to a signal detection circuit 7. The signal detection circuit 7 detects the AE control signal required for AE control among the video signals and selects and outputs it. The AE control signal is inputted to a timing signal generation circuit 10, and the timing signal generation circuit 10 outputs a shutter speed signal, a gain- adjusting signal and the timing signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing device (signal processor) mainly used for a video camera using an image pickup device, and more particularly to an automatic exposure (A).
The present invention relates to an AE control signal processor having a control function of E (Auto Exposure).

[0002]

2. Description of the Related Art In a video camera, an AE control for automatically changing an exposure by changing a shutter speed and a gain according to a change of a subject is indispensable. The conventional AE control is realized using a circuit as shown in FIG.

In FIG. 5, reference numeral 101 denotes a CCD (charge coupled d).
evice), which converts the input light into an analog electric signal and outputs it. From the output analog signal, C
A necessary signal is extracted by a DS (correlated double sampling) 102, and the extracted signal is input to the video signal processing device 103. The video signal processing device 103 is connected to an external microcomputer or other controller 104, and based on a signal including information necessary for AE control input from the video signal processing device 103, 10
4 performs calculations and outputs signals to the CCD and CDS.
By these two signals, the shutter speed of the CCD and the CD
The gain of S is controlled, and AE control is thereby performed.

[0004] However, the above-mentioned conventional AE control system has the following problems. That is, in the AE control system described above, a controller such as a microcomputer is required, and development of software for AE control is indispensable. When a controller is used, the number of components to be used increases. Therefore, it takes time and expense for software development, and the cost of the entire AE control system increases.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the need for developing software used for AE control and to reduce the number of parts, thereby reducing the cost of the entire system. An AE control signal processor which enables the following is provided.

[0006]

An AE control signal processor according to the present invention comprises: a signal detection circuit for calculating an AE control signal from a video signal by a signal processing circuit for digitally processing an output signal of an image sensor; And a timing signal generating circuit for adjusting the shutter speed of the image sensor based on the output signal and the output gain of the image sensor.

That is, in the AE control signal processor of the present invention, AE control can be performed by hardware using a signal detection circuit and a timing signal generation circuit included in the AE control signal processor. Therefore, the AE control signal processor of the present invention does not require a microcomputer or other controller for AE control, and therefore does not require software development for that purpose. At the same time, it is possible to reduce the number of parts,
As a result, the cost of the entire system can be reduced.

It is preferable that the signal detection circuit adds the input signal for each field and then compresses the signal to form an AE control signal. The reason why the input signal is compressed is that there is a great merit that the calculation speed can be increased by reducing the number of input signals because AE control does not require very fine data. .

Further, the timing signal generating circuit is
A shutter speed control circuit that outputs an enable signal when the shutter speed is stabilized as a result of decoding the E control signal, selecting one of a number of shutter speeds and adjusting the shutter speed for a plurality of fields, and responding to the enable signal. And a gain adjustment circuit that changes the output gain to determine the optimum gain.

Further, the gain adjusting circuit may adjust the output gain according to the enable signal. In this case, the gain may be increased or decreased according to the enable signal. Further, the gain adjustment circuit may control a CDS that extracts a necessary signal from an output of the image sensor.

The timing signal generating circuit may include a clock generating circuit for generating a clock for each circuit, so that the operation of each circuit may be adjusted.

In this manner, if the shutter speed is controlled by the CCD and the gain level is controlled by the CDS, the same AE control as in the related art can be realized without using the controller.

The AE control signal processor may be provided with an interface circuit for exchanging signals with an externally provided controller. However, in the case of the present invention, the controller does not make a determination regarding AE control. In this case, if a controller is provided, control using a microcomputer can be performed as in the related art, and the range of applications is widened.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an AE control signal processor according to the present invention will be described with reference to FIGS.

FIG. 1 is a schematic diagram showing the application of the AE control signal processor of the present invention to a video camera system. 1 is a CCD, 2 is a CDS, 3
Is an AE control signal processor.

The CCD 1 converts the input light into an analog signal and outputs the analog signal to the CDS 2. The CDS 2 extracts necessary signals from the input analog signals and performs preprocessing for converting the analog signals into digital signals. CDS2
The signal processed and output in is input to the AE control signal processor 3. The AE control signal processor 3 outputs a shutter speed signal to the CCD 1 based on the signal input from the CDS 2 and outputs a gain adjustment signal to the CDS 2.
E control is realized.

FIG. 2 is a block diagram showing the AE control signal processor 3 shown in FIG. 1 in detail.
Based on this, an embodiment of the AE control signal processor 3 of the present invention will be described in more detail.

The analog signal extracted by the CDS 2 is input to an A / D converter 4. The A / D converter 4 converts an input analog signal into a digital signal. The digital signal output from the A / D converter 4 is input to the signal processing circuit 5. The signal processing circuit 5
It processes the input digital signal and outputs a video signal.
The video signal is divided into two parts, one is converted again into an analog signal by the D / A converter 6 and sent to the recording system, and the other is sent to the signal detection circuit 7 for use in AE control.

The signal detection circuit 7 detects an AE control signal required for AE control from the video signal, selects it, and outputs it. The detection and output of the AE control signal are performed for each field.
Specifically, the signal detection circuit 7 includes an addition circuit 8 and a data conversion circuit 9 as shown in FIG.
The video signal is added by the adder circuit 8 to form a 24-bit data signal. Then, the 24-bit data signal is further input to the data conversion circuit 9, where it is compressed into an 8-bit data signal. Such signal compression is performed because the signal has little relation to the recording system, and thus does not need to be calculated in detail, and it is preferable to give priority to the calculation speed by reducing the number of data digits. The signal compression in this case is performed as shown in FIG. That is, the lower 3 bits of the 24-bit data are converted to 8 bits.
The data is sequentially converted so as to correspond to the lower one bit of the bit data. The data conversion performed by the data conversion circuit 9 is not particularly limited to this method, and the bit length of the data does not need to be as described above. All of these should be set arbitrarily according to the characteristics of the system.

The AE control signal, which is an 8-bit signal output from the data conversion circuit 9, is input to a timing signal generation circuit 10. The timing signal generation circuit 10 outputs a shutter speed signal, a gain adjustment signal, and a timing signal as described below.
The timing signal generation circuit 10 includes a shutter speed control circuit 11, a gain adjustment circuit 12, and a clock generation circuit 13, as shown in FIG. The AE control signal output from the data conversion circuit 9 is input to the shutter speed control circuit 11 among them. The shutter speed control circuit 11 codes an AE control signal to determine which shutter speed is to be selected from among 256 predetermined shutter speeds, and outputs a shutter speed signal to the CCD 1. Here, the predetermined shutter speed is 256
The stage is the shutter speed control circuit 11
Is an 8-bit AE control signal. The shutter speed is between 1 / 10,000 seconds and 1/4. When this operation is repeated several times, that is, after several fields have elapsed, the shutter speed is determined to be a constant speed by the feedback effect. When the shutter speed is determined to be constant, the shutter speed control circuit 11 outputs an enable signal to the gain adjustment circuit 12. The gain adjustment circuit 12 to which the enable signal has been input gradually increases the gain. Then, when a few fields have passed and an appropriate gain has been reached, the gain adjustment circuit 12 determines the gain. In the present embodiment, the gain can be adjusted with 8 bits, and when the value is changed one bit at a time to obtain an appropriate gain, a gain adjustment signal is output. Then, the gain adjustment signal is converted into an analog signal by a D / A converter (not shown) and then input to the CDS 2. As described above, the shutter speed and the gain are adjusted, and the exposure is automatically adjusted accordingly. The clock generation circuit 13 generates a clock required for each circuit such as the signal processing circuit 5 and the signal detection circuit 7.

Further, an interface circuit 14 can be provided to communicate with a controller (not shown) provided outside the AE control signal processor 3, so that the present invention can be applied to a conventional device or can be applied.

[0022]

Since the present invention is configured as described above, AE control can be performed by the signal processor alone without using a controller. In this sense, the AE control signal processor of the present invention can be called a self AE control signal processor. Therefore, according to this signal processor, there is no need to develop software used for AE control, and it is possible to reduce the number of components, and as a result, it is possible to suppress the cost of the entire system.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an AE control signal processor according to the present invention applied to a video camera system.

FIG. 2 is a block diagram showing an AE control signal processor according to the present invention.

FIG. 3 is a block diagram showing a signal detection circuit and a timing signal generation circuit according to the present invention.

FIG. 4 is a conceptual diagram showing a data conversion method performed by the data conversion circuit according to the present invention.

FIG. 5 is a block diagram showing a conventional AE control circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CCD 2 CDS 3 AE control signal processor 4 A / D converter 5 Signal processing circuit 6 D / A converter 7 Signal detection circuit 8 Addition circuit 9 Data conversion circuit 10 Timing signal generation circuit 11 Shutter speed control circuit 12 Gain adjustment circuit 13 Clock Generation circuit 14 Interface circuit 101 CCD 102 CDS 103 AE control signal processor 104 Controller

Claims (6)

[Claims] 1. A signal detection circuit for calculating an AE control signal from a video signal output by a signal processing circuit for digitally processing an output signal of an image sensor, and adjusting a shutter speed of the image sensor based on the AE control signal. An AE control signal processor comprising: a timing signal generation circuit for adjusting an output gain of the imaging device. 2. The AE control signal processor according to claim 1, wherein the signal detection circuit adds the input signal for each field and then compresses the signal into an AE control signal. 3. A timing signal generating circuit decodes an AE control signal, selects one of a number of shutter speeds, and adjusts the shutter speed for a plurality of fields, and outputs an enable signal when the shutter speed is stabilized. A shutter speed control circuit, a gain adjustment circuit that changes an output gain according to the enable signal and determines an optimum gain,
3. The AE control signal processor according to claim 2, comprising: 4. The AE control signal processor according to claim 3, wherein the gain adjustment circuit adjusts an output gain according to the enable signal. 5. The AE control signal processor according to claim 3, wherein the gain adjustment circuit controls a CDS for sampling an output of the image sensor. 6. The timing signal generating circuit includes a clock generating circuit for generating a clock for each circuit.
The AE control signal processor according to any one of the above items.