JPS6145685A - Signal processing system - Google Patents

Abstract

PURPOSE:To obtain an output capable of arithmetic processing with high accuracy without damaging information quantity of a whole signal by selecting the prescribed part of a picture signal and controlling AGC based upon the area of a signal. CONSTITUTION:Various types of information such as shutter speed and stop value are calculated, supplied through a terminal 3 to an AGC level setting circuit 12 and an area selecting circuit 13 and an AGC threshold and an area to be selected are determined. An selected gate out of analog gates 14A-14E is closed in accordance with a signal from the selecting circuit 13. The signal from a selected area of a CCD line sensor 1 is inputted to comparison circuits 10A-10E and compared with an AGC threshold level. When the output of either of areas reaches the threshold level, the signal is inputted from an OR circuit 11 to a storage completion signal generating circuit 15 and a storage action of the CCD line sensor is completed. In this invention, a prescribed part area of a picture signal is selected and AGC is controlled, an undesirable high contrast part can be removed and the information of a whole signal can not be damaged.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal processing method, preferably a signal processing method suitable for processing image signals.

Conventionally, as a means for forming one image signal, a method is known in which an image is projected onto a sensor such as a CCD or BBD comprising a large number of photoelectric conversion elements, and the photoelectric output is read out to obtain an image signal. However, since the image signal has a wide range of changes in the contrast of the image itself, the output signal is
Since the level changes over a wide range, in many cases, the peak value in the output signal from a sensor such as COD is detected and multiplied by A(, G'C) to obtain one output image signal.

This situation will be explained with reference to FIG. The characteristic curve in the figure shows a signal waveform read out from a sensor such as COD, and the abscissa shows a schematic diagram of the power of each photoelectric conversion element of the line sensor.

As shown in the figure, if there is a high contrast area with high brightness at the left end of the sensor, the sensor detects the peak value of that area and applies AGC to the sensor output, so it is not possible to The sensor output is compressed, so a large output cannot be obtained, and for example, there is a drawback that it is not possible to process the main part of the signal (FIG. 1, calculation area) that should be processed as an image signal.

The object of the present invention is to solve the above-mentioned drawbacks, and its characteristics are that a desired sensor area is selected and the signal output of the selected area is controlled by AGC. The present invention resides in that the above-mentioned drawbacks have been eliminated, and the present invention has been configured to obtain a signal output that allows signal processing, particularly signal arithmetic processing, to be performed with high precision.

Other features of the present invention will become clear by describing specific embodiments of the present invention with reference to the drawings.

Next, an example in which the present invention is applied to a TTL type natural focus detection device for a camera will be described with reference to FIGS. 1 to 3.

In FIG. 1, reference numeral 1 denotes a CCD line sensor which receives image light after passing through a photographing lens (not shown).

2 is the monitor circuit, and 3 is the camera shutter speed.

aperture), a terminal for appropriately calculating the setting information of the focal length of the lens and inputting the calculated output, and 4 a drive circuit that provides signals such as a reset pulse, an accumulation operation completion signal, and a readout pulse to the CCD line sensor.

5 is a focus detection start circuit such as a distance measurement button of the camera;
Reference numeral 6 indicates an arithmetic processing circuit for processing the sensor output and performs focus detection, 7 a determination circuit, 8 a lens drive circuit, and 9 a lens drive motor. As for the line sensor 1, for example, the one shown in Japanese Patent Application Laid-Open No. 59-40610 is used, and as for the automatic focus detection circuit from the readout circuit 4 to the motor 9, there is no W connection delay in the present invention. Although omitted, for example, Japanese Patent Application Laid-Open No. 54-1592
A natural focus detection circuit such as that disclosed in 59 is used.

FIG. 2 shows an example of details of the monitor circuit 2, and in the figure, 10A-10E are comparison circuits.

11 is an OR gate, 12 is an AGC level setting circuit, 1
3 is the selection circuit % 14A to 14E are analog switches,
Reference numeral 15 indicates an accumulation completion signal generating circuit. In the same figure, the COD line sensor l and the arithmetic processing circuit are connected in parallel via the comparison circuit h2, but the CCD
The output of the line sensor is output in time series according to the read pulse from the drive circuit 4 as shown in FIG. 1, and is input to the arithmetic processing circuit 6. The level setting circuit 121 selection circuit is set to terminal 3. Various information 5, such as the focal length of the lens used, the shutter speed of the camera, and the exposure value such as the aperture value, are calculated and input, and the level setting circuit forms a predetermined voltage signal based on the input signals. On the other hand, the selection circuit outputs a selection signal indicating which region of the photoelectric conversion element section of the CCD line sensor is to be selected based on the input signal from the terminal 3 as a gate signal to the analog gate.

In the above configuration, predetermined information is first set.

Setting information such as shutter and aperture value can be determined according to the subject brightness to obtain the appropriate exposure (determined by a known photometry circuit, and lens focal length information is the value of the lens being used, or used in the case of a zoom lens) Set the focal length appropriate for the zoom ratio. These pieces of information are calculated as appropriate, and the calculations are performed based on the following requirements. That is, if the brightness information of the object is small, the storage time of the CCD line sensor needs to be long, and if the focal length of the lens is long.

Just as camera shake tends to occur when taking pictures, during the accumulation period of the CCD line sensor, the image light from the CCD line sensor receives the light that passes through the photographing lens, so slight fluctuations of the camera body can cause pre-shaking in the optical image. As a result, the output signal of the CCD line sensor as well.

This results in a blurred image signal. Therefore, as many image signals as possible to obtain the line sensor output and then perform arithmetic processing, the calculation accuracy will be improved. If the subject brightness is high and the CCD line sensor's storage time is not required, or if the focal length of the lens is short, the image light on the CCD line sensor may fluctuate (for example, due to the camera body (Due to shaking, etc.)
For example, in the case of 1 image signal and 1-, it is sufficient to select only the central part of the field of view of the subject and perform arithmetic processing.

As shown in Figure 4, there are many areas with extremely strong contrast in the field of view of the subject, so if you select only the center, for example, this area will be eliminated and it will take time to process the line sensor output afterwards. will also be shortened.

As mentioned above, various types of information are appropriately calculated and applied to the terminal 3 and applied to the level setting circuit, where the AGC threshold level is applied to the selection circuit 13, and the CCD is set by the same circuit. A signal that selects only a partial area on the line sensor is formed and applied to analogues 14A-14E (for example, the third illustrated calculation area).

At the same time, the selection signal of the selection circuit 13 is applied to the drive circuit 4, and the COD line sensor output of only the selected region among the analogue gates 14A to 14E is outputted from the circuit 1.

On the other hand, the level setting circuit 12 has an analog switch 14A.
The AGC threshold signal was selected by the selection circuit 13 because it was connected to the comparison circuits 10A to 10E via -14E. It is applied to the other input of each comparison circuit which inputs the output lO of the COD line sensor area, and the same level signal and one pixel signal are compared during the accumulation period. When the pixel signal level exceeds the AGC signal, an accumulation completion signal is generated from the generation circuit 15 from one of the comparison circuits 10A to IOE (for example, the Xth pixel signal in FIG. 3) via the OR circuit 11, and is sent to the COD line sensor. , the completion signal is applied %
The accumulation operation of the COD line sensor is completed.

As shown in Fig. 3, the signal obtained as the above result is selected as one calculation area, high contrast areas are excluded, and the image signal of the selected partial area is subjected to peak AGC control at the X-th pixel level. , will be output.

In the above case, the N output value information corresponds to a small subject brightness or a lens with a long focal length is used.
The calculation area can change depending on the degree of each piece of information (as mentioned above, each piece of information is processed as appropriate). Further, the output of the line sensor 1 is appropriately selected within the desired optimum range.

The signal is input to the arithmetic processing circuit 6, and the photographing lens 9 is brought into focus by the lens drive motor 9.

In the embodiment described above, the level setting circuit 12 and the comparison circuit 1
An example in which peak AGC control is performed using 0 is explained [7] However, it goes without saying that average control may be performed instead of peak AGC control, and a known circuit may be used for that circuit.

As described above, according to the present invention, when there is an undesirably high contrast part in one image signal, in order to remove the point where the information amount of the entire signal is damaged by the pixel signal of the image part, Since the partial area is appropriately selected and AGC control is performed based on the single selected area signal, the image signal output is large.

Claims (1)

[Claims] A signal processing method characterized in that the gain of the output signal is controlled based on the output signal of a sensor including a large number of photoelectric conversion elements, and a range of the photoelectric conversion elements is selected and read out.