JPS61124925A - Automatic exposure correcting device - Google Patents

Abstract

PURPOSE:To make an invariably proper exposure adjustment by varying a photometric area according to a color temperature state and a zoom ratio. CONSTITUTION:A zoom ratio detecting circuit 7 detects whether the zoom ratio of a lens part is in its wide-angle or telephoto range and a CCA filter switching detecting circuit 8 detects such a condition that a photograph based upon color temperature is taken. Detection signals of the CCA filter switching detecting circuit 8 and zoom ratio detecting circuit 7 are inputted to a photometric pattern generating device 9, which then outputs a measurement pattern signal and a photometric pattern switching signal. Those signals are inputted to an iris control circuit 10 and a video signal from an image pickup element 4 is amplified by a preamplifier 5, whose signal is inputted to the iris control circuit 10 to control a stop according to the luminance level of each photometric part of a specified photometric pattern. Then, when the luminance signal of each photometric part becomes smaller than that of any other part, the stop 3 is opened by a specific extent to perform servocontrol so that the level of the luminance signal of the specified part is proper.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an automatic exposure compensation device for a video camera or the like, and more particularly to an automatic exposure compensation device that changes an exposure state according to color temperature conditions and/or zoom ratio.

[Prior art]

Conventionally, in video cameras and the like, if there is a high-luminance part in the background of the subject, the subject will be photographed in black, so backlight compensation has been manually activated to correct the exposure. In addition, in such a case, backlight correction can be performed to a certain extent by using a photometry mode such as a center-weighted photometry method. With this center-weighted metering method, the metering range is focused on the center, so even if the brightness at the center of the screen is much lower than the brightness at the periphery, the brightness at the center will be correct. The aperture opens. However, with this configuration, if the size of the subject to be photographed changes depending on the zoom ratio, for example, in the case of telephoto, the subject will be in the center, such as a close-up of a person, and in the case of wide-angle, the entire screen, such as a landscape, will be the subject. In other words, since the size of the subject is not constant, the amount of light at the periphery of the screen changes, and even if you open the aperture by a certain amount to compensate for backlight, you will not be able to obtain a subject with appropriate brightness. Since the brightness distribution differs depending on the shooting environment such as outdoors (in the case of outdoors, there are many high-brightness areas at the top of the screen), there is a drawback that backlight correction cannot be performed properly.

〔the purpose〕

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to relate to an automatic exposure compensation device that can automatically change exposure conditions depending on photographing conditions in order to eliminate the above-mentioned drawbacks.

In order to achieve the above-mentioned purpose, according to the embodiment of the present invention, the photometry area is changed according to the color temperature state and the zoom ratio, so that appropriate exposure adjustment can always be obtained.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a block diagram according to a first embodiment of the present invention.

In the figure, 1 is a lens unit including a zoom mechanism, 2 is a CCA filter that enters and exits the optical path according to the color temperature of the subject, 3 is an aperture, 4 is an image sensor, 5 is a preamplifier, 6 is a signal processing system, and 7 Reference numeral 8 indicates a zoom ratio detection circuit, 8 indicates a CCA filter switching detection circuit, 9 indicates a photometric filter generator, and 10 indicates an iris control circuit.

The zoom ratio detection circuit 7 detects whether the zoom ratio of the lens unit 1 is wide or telephoto, and the CCA filter switching detection circuit 8
Turns on CCA filter 2 (state a in the optical path)
10FF (outside the optical path), that is, generally outdoors,
Detects the condition of shooting at indoor color temperature. When the detection signals of the CCA filter switching detection circuit 8 and the zoom ratio detection circuit 7 are input to the photometric pattern generating device 9, the photometric pattern generating device 9 outputs a measurement pattern signal and a photometric pattern switching signal. The photometric pattern signal is a signal for selecting a photometric pattern, and the photometric pattern switching signal is a signal that conveys switching of the photometric pattern according to the zoom ratio and CCA filter ON10FF. These signals are input to the iris control circuit 10, and the video signal from the image sensor 4 is amplified by the preamplifier 5, and this signal is input to the iris control circuit 10 to determine the brightness level of each photometry part in the specified photometry pattern. When the luminance signal of each photometric part becomes smaller than the luminance signal of other parts, the aperture 3 is opened by a predetermined amount to adjust the level of the luminance signal of the designated part. Control the servo so that

FIG. 2 is a concrete block diagram of the circuit of the photometric pattern generator 9. As shown in FIG. 1) is a clock generator for dividing the horizontal period; 12 is a first counter circuit for counting the horizontal signal HD; 13 is a second counter circuit for counting the vertical signal HD; 14 is the first and second counter circuit; A first counter circuit for obtaining a photometric pattern signal by two counter circuits 12 and 13.
Matrix circuit, 15 is zoom ratio/CCA filter 0N
27th) IJ circuit that obtains output by 10FF,
16 is a comparator that detects zoom tele/wide;
17 is a reference power source.

The first matrix circuit 14 has a zoom ratio detection output, a CCA
A predetermined photometry pattern corresponding to the filter ON10FF is stored. An example is shown in Figure 3. Figure 3 (
a) is a photometry pattern when the zoom is wide and the CCA filter is ON; for example, when the color temperature is wide when shooting outdoors. At this time, the high-brightness area is generally located at the top of the screen, and the shooting target is often a landscape, so downward-weighted metering is used. Figures 3~) are photometry patterns when the CCA filter is ON and the zoom is set to telephoto, or when the CCA filter is OFF and the zoom is set to wide.For example, in the case of outdoor color temperature and telephoto, the shooting target is a close-up of a person in the center of the screen. Because of this, center-weighted metering is used. Furthermore, in indoor color temperature and wide-angle shooting, it is generally thought that far away places are rarely photographed indoors, and most of the time indoors are shot at wide-angles. Also, the brightness difference with the background rarely appears large, and when it does, it is likely when there is a window or white wall all over, so the high brightness part is not necessarily at the top, and therefore the center Use photometry. Figure 3(c)
This is the case when the CCA filter is OFF and zoom telephoto is used.

The idea is the same as in the indoor color temperature and wide-angle case in (b), but the focused photometry area is increased in consideration of the fact that the subject becomes larger due to telephoto.

In FIG.
The wide signal and the CCA filter 0N10vrtv signal are input to the second matrix circuit 15, and the second matrix circuit 15 outputs a signal for selecting the photometry pattern described above (photometry pattern switching signal). This output is input to the iris control circuit 10 and the matrix circuit 14. The matrix circuit 14 selects a photometric pattern stored in the matrix circuit 14 using a signal from the matrix circuit 15. That is, it outputs a pulse that is at a high level only for a predetermined period within the vertical period and a predetermined period within the horizontal period.

This can be obtained by specifying the position on the screen using the counter amounts of the horizontal and vertical signals from the first and second counter circuits 12 and 13. Further, by using this pulse signal, information as to which region, region 1 or region 2, each part of the video signal is located is inputted to the iris control circuit 10 as a photometric pattern signal.

Figure 4 shows the iris control circuit 10 in Figure 1.
It is a concrete block diagram of. 18 is a smoothing circuit that averages the output from the preamplifier 5; 19 is a switch that is switched by a photometric pattern signal that is an information signal of the photometric area obtained from the photometric pattern generator 9; 20, 21 is a smoothing circuit; and 22 is a photometric pattern. 23 is a comparator that compares the luminance signals of two regions; 24 is a variable resistor that sets the threshold for the amount of backlight; 25 is an amplifier; 26 is switched by the signal from the comparator 23. The switch 27 is an amplifier.

The positional information of the photometric area selected by the photometric pattern signal from the photometric pattern generator 9 and the position of the output signal from the preamplifier 5 within the screen are synchronized. That is, when the video signal in area 1 is maintained, the photometric pattern signal outputs information indicating area 1. When the photometric pattern signal is outputting information on area 1, switch 19 is connected to terminal a.
and when outputting information for area 2, connect to the terminal. The signals of the two regions are averaged by smoothing circuits 20 and 21, respectively. The signal in region 2 is further level-adjusted through an attenuator 22 whose attenuation rate is changed by the photometric pattern switching signal. This attenuator 22 has a gain that is inversely proportional to the area of the photometric area, and can cancel level changes that occur when the photometric area 2 increases or decreases. Further, by adding tILEE obtained by the variable resistor 24 to the signal from the region 2, a threshold voltage for backlighting is set. A comparator 23 compares the signal of area 1 with the signal of area 2 where the amount of backlight is set. When comparing the signal in area 1 and the signal in area 2, when the signal in area 2 is larger, the switch 26 is connected to terminal a', the signal from the preamplifier 5 flows directly through the smoothing circuit 18, and the signal is adjusted to an appropriate size by the amplifier 27. The signal is amplified to control the iris. In other words, the auto iris mode is based on average metering over the entire surface.

When region 1 is larger, switch 26 is connected to terminal b', the signal in region 2 flows, and the iris control is performed using the video signal of this portion. In other words, it is partially weighted photometry. As above, CCA filter 0N10FF
Exposure conditions are corrected by switching the metering pattern depending on whether the zoom is telephoto or wide. Further, when the level difference between photometric areas 1 and 2 in each photometric pattern is large, backlight correction is performed. , FIG. 5 is a block diagram of a photometric pattern switching device 9 according to a second embodiment of the present invention. The feature of this second embodiment is that the photometric pattern switching device is performed by a pattern generator including a micro combinator. In the figure, 28 is an A/D conversion circuit that converts a zoom ratio detection signal into a digital signal, and 29 is a pattern generator including a microcomputer that generates a photometric pattern.

The H signal, the ■ signal, the CCA filter 0N10FF signal, and the zoom ratio signal digitally converted by the A/D conversion circuit 28 are input to the pattern generator 29, and a photometry pattern signal and a photometry pattern switching signal are output. It also outputs the photometry pattern so that it can be displayed on the EVF. FIG. 6 shows a specific example.

If a frame such as a hatched area is displayed to specifically indicate the photometry range, the subject can be photographed with appropriate brightness by placing the subject within the frame. Further, by using the pattern generator 29, the photometry range can be continuously changed depending on the zoom ratio. Figure 7,
FIG. 8 shows a photometric pattern as the output of the pattern generator when the CCA filter is ON. In FIG. 7, the vertical axis is time and the horizontal axis is zoom ratio. A@B is a pattern generation line in the horizontal direction, and the area sandwiched between A and 8 is area 2. Similarly, C@D is a vertical pattern generation line, and the region sandwiched between C and D is region 2.

Therefore, as shown in FIG. 8, W is downward-weighted photometry, and ■ is center-weighted photometry, and the photometry area can be changed continuously between these areas, making it possible to handle a larger number of shots.

FIGS. 9 and 10 are diagrams showing changes in the photometry pattern when the CCA filter is OFF, and since the same operation is performed, the explanation will be omitted. In this case, the pattern signal is outputted from the pattern generator so that the larger the zoom ratio is, the wider the photometry area is. In the above embodiments, the color temperature conditions were detected using the CCA filter 0N10FF, but the exposure conditions may be changed according to the outputs of a plurality of color sensors with different spectral characteristics that detect the color temperature. Further, the exposure conditions are not limited to the photometric pattern, but also include the aperture value, shutter time, etc.

〔effect〕

As described above in detail and concretely, according to the present invention, fine exposure control is possible by changing the exposure condition by at least one of color temperature and zoom ratio, and it is possible to photograph a subject with appropriate brightness. becomes.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram of an automatic exposure compensation device according to the present invention;
Fig. 2 is a block diagram of the photometric pattern generator, Fig. 3 is a specific example of the photometric pattern, Fig. 4 is a block diagram of the iris control circuit, and Fig. 5 is a block diagram of another embodiment of the photometric pattern generator. , Fig. 6 is a diagram showing the photometry pattern displayed on the EVF, Fig. 7 is a diagram of the change in the photometry pattern when the OCA filter is ON, Fig. 8 is a diagram of the photometry pattern when the CCA filter is ON, and Fig. 9 is CCA filter OFF
Fig. 10 is a diagram of the photometry pattern when the CCA filter is OFF. In the figure, 7 is a zoom ratio detection circuit, 8 is a CCA filter switching detection circuit, 9 is a photometric pattern generator, 10 is an iris control circuit, 12.13 is a first and second counter circuit, and 14.15 is a first and second counter circuit. 27 trix circuit,
16 is a humpator, 19 is a switch, 22 is an attenuator, 23 is a humpator, 26 is a switch, 28 is A
/D conversion circuit, 29 is a pattern generator. Figure 7 Figure 5 Figure 6 Figure 7 Figure 5 Figure 9 Figure 70

Claims (2)

[Claims] (1) An automatic exposure compensation device that changes exposure conditions according to at least one of the color temperature and zoom ratio of a subject. (2) The automatic exposure compensation device according to claim 1, further comprising display means for displaying information regarding the exposure conditions.