JP2588696B2 - Automatic exposure compensation device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an automatic exposure correction device such as a video camera.
In particular, the present invention relates to an automatic exposure correction device that changes an exposure state according to a color temperature condition and / or a zoom ratio.

(Prior art)

Conventionally, in a video camera or the like, if a subject has a high-luminance portion in the background, the subject is photographed in black, so that backlight compensation has been manually operated to correct the exposure. In such a case, if the photometry mode is a center-weighted photometry method or the like, the backlight can be corrected to some extent. In this center-weighted metering method, the metering range is fixed at the center, so that, for example, even when the brightness at the center of the screen is very small compared to the brightness at the periphery, the brightness at the center is appropriate. The aperture opens. However, with such a configuration, when the image varies depending on the zoom ratio of the subject to be photographed,
For example, in the case of telephoto, a subject such as a person's top is at the center, and on the wide side, the entire screen such as a landscape is a subject. That is, since the size of the subject is not constant, the amount of light in the peripheral portion in the screen changes, and even if the stop is opened by a certain amount for backlight correction or the like, a subject with appropriate luminance cannot be obtained. The luminance distribution differs depending on the shooting environment, such as outdoors (there are many bright areas at the top of the screen in the case of outdoors), so that backlight compensation is not properly performed.

〔Purpose〕

Therefore, an object of the present invention is to provide an automatic exposure compensating apparatus capable of automatically changing an exposure condition according to a photographing condition in order to eliminate the above-mentioned defect.

In order to achieve the above object, according to the present invention, an image pickup state of a subject is identified according to a color temperature correction state and a zoom ratio, and a pattern of a photometry area is controlled, so that an appropriate exposure adjustment is always obtained. .

〔Example〕

Hereinafter, embodiments of the present invention will be described specifically and in detail with reference to the drawings.

FIG. 1 is a block diagram according to a first embodiment of the present invention. In the figure, reference numeral 1 denotes a lens unit including a zoom mechanism, 2 denotes a CCA filter for color temperature conversion or correction which enters and exits in an optical path according to the color temperature of a subject, 3 denotes an aperture, 4 denotes an image sensor, 5 denotes a preamplifier, Reference numeral 6 denotes a signal processing system, 7 denotes a zoom ratio detection circuit, 8 denotes a CC filter switching detection circuit, 9 denotes a photometric pattern generator, and 10 denotes an iris control circuit.

A zoom ratio detection circuit 7 detects whether the zoom ratio of the lens unit 1 is wide or telephoto, and a CCA filter switching detection circuit 8
ON / OFF of CCA filter 2 (in the optical path)
(A state outside the optical path), that is, a condition in which photographing is generally performed at an outdoor or indoor color temperature is detected. When the detection signals from the CCA filter switching detection circuit 8 and the zoom ratio detection circuit 7 are input to the photometric pattern generator 9, the photometric pattern generator 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 for notifying the switching of the photometric pattern according to the zoom ratio and the ON / OFF of the CCA filter. 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. This signal is input to the iris control circuit 10 and the luminance level of each photometric portion in the specified photometric pattern When the luminance signal of each photometric portion becomes smaller than the luminance signals of the other portions, the aperture 3 is opened by a predetermined amount so that the level of the luminance signal of the designated portion becomes appropriate. Perform servo control.

FIG. 2 is a specific block diagram of the circuit of the photometric pattern generator 9. 11 clock generator for dividing the horizontal period, 12 a first counter circuit for counting a horizontal signal H _D, 13 second for counting the vertical signal V _D
A counter circuit 14 is a first matrix circuit for obtaining a photometric pattern signal by first and second counter circuits 12 and 13, and 15 is a second matrix circuit for obtaining an output by zoom ratio / CCA filter ON / OFF. Reference numeral 16 denotes a comparator for detecting the tele wide of the zoom, and reference numeral 17 denotes a reference power supply.

The first matrix circuit 14 stores a predetermined photometric pattern corresponding to a zoom ratio detection output and a CCA filter ON / OFF. FIG. 3 shows an example. FIG. 3A shows a photometric pattern when the zoom is wide and the CCA filter is ON, for example, when the color temperature is wide at outdoor shooting.
At this time, in general, the high-brightness part is often located at the upper part of the screen, and there are many scenery and the like as photographing targets. Fig. 3 (b) shows the CCA filter on and the zoom set to tele.
Alternatively, this is a photometry pattern when the CCA filter is OFF and the zoom is wide. For example, in the case of an outdoor color temperature and telephoto, the center-weighted photometry is performed because the photographing target performs a person-up at the center of the screen. In general, when shooting indoors at a wide temperature and color temperature, indoors are rarely shot at distant places, and almost wide shooting is considered. In addition, the luminance difference from the background is rarely large, and if there is a luminance difference, it is conceivable that the window or white wall is on the entire surface, so the high luminance part is not necessarily at the top, so Center-weighted metering. FIG. 3C shows the case where the CCA filter is OFF and the zoom telephoto is set. The concept is the same as that of the case (b) of indoor color temperature and wide, but the weighted photometric area is increased in consideration of the fact that the subject becomes larger by the amount of telephoto.

In FIG.
The wide signal and the CCA filter ON / OFF signal are input to the second matrix circuit 15, and the second matrix circuit 15 outputs a signal for selecting the above-described photometric pattern (a photometric pattern switching signal). This output is input to the iris control circuit 10 and the matrix circuit 14. Matrix circuit
In 14, the matrix circuit 14 uses signals from the matrix circuit 15.
Select the photometric pattern stored in. That is, a pulse which becomes high level for a predetermined period in the vertical period and a predetermined period in the horizontal period is output. This can be obtained by specifying the position on the screen by the counter amount of the horizontal signal and the vertical signal from the first and second counter circuits 12 and 13. In addition, the pulse signal inputs to the iris control circuit 10 information as to which of the areas 1 and 2 each part of the video signal is located as a photometric pattern.

FIG. 4 shows the iris control circuit 10 in FIG.
FIG. 3 is a specific block diagram of FIG. 18 is a smoothing circuit for averaging the output from the preamplifier 5, 19 is a switch which is switched by a photometric pattern signal which is an information signal of a photometric area obtained from the photometric pattern generator 9, 20 and 21 are smoothing circuits, 2
Reference numeral 2 denotes an attenuator whose attenuation rate varies according to a photometric pattern switching signal; 23, a comparator for comparing luminance signals in two regions; 24, a variable resistor for setting a threshold for reverse light quantity; 25, an amplifier; and 26, a comparator. A switch which is switched by a signal 23, and an amplifier 27.

The position information in the screen of the position information of the photometry area selected by the photometry pattern signal from the photometry pattern generator 9 and the output signal from the preamplifier 5 are synchronized. That is, when the video signal in the area 1 is maintained, the photometric pattern signal outputs information indicating that the area 1 is in effect. When the photometric pattern signal outputs information of the area 1, the switch 19 is connected to the terminal a.
When the information of the area 2 is output, the terminal b is connected. The signals in the two regions are averaged by the smoothing circuits 20 and 21, respectively. The level of the signal in the area 2 is further adjusted through an attenuator 22 whose attenuation rate changes according to a photometric pattern switching signal. The attenuator 22 has a gain that is inversely proportional to the area of the photometry area, and can cancel the level change accompanying the increase and decrease of the photometry area 2. Further, a threshold voltage which causes backlight is set by adding the voltage obtained by the variable resistor 24 to the signal from the area 2. The signal in the area 1 by the comparator 23 and the area 2 in which the reverse light amount is set
Compare with the signal of When the signal of the area 1 is compared with the signal of the area 2, when the area 2 is larger, the switch 26 is connected to the terminal a '.
The signal of the preamplifier 5 flows directly through the smoothing circuit 18 and is amplified by the amplifier 27 to a signal of an appropriate magnitude to perform iris control. That is, the auto iris mode based on the entire surface average photometry is performed. When the area 1 is larger, the switch 26 is connected to the terminal b ', a signal in the area 2 flows, and iris control is performed on the video signal in this area. That is, partial weighted metering is performed. As above
The exposure condition is corrected by switching the photometric pattern according to the CCA filter ON / OFF, zoom telephoto, and wide. When the level difference between the photometric areas 1 and 2 in each photometric pattern is large, backlight correction is performed.

FIG. 5 is a block diagram of the photometric pattern switching device 9 according to the second embodiment of the present invention. The feature of the second embodiment is that the switching of the photometric pattern is performed by a pattern generator including a microcomputer. In the figure, reference numeral 28 denotes an A / D conversion circuit for converting a detection signal of a zoom ratio into a digital signal, and reference numeral 29 denotes a pattern generator including a microcomputer for generating a photometric pattern.

H signal, V signal, CCA filter ON / OFF to pattern generator 29
A signal and a zoom ratio signal digitally converted by the A / D conversion circuit 28 are input, and a photometric pattern signal and a photometric pattern switching signal are output. It also outputs the metering pattern so that it can be displayed on the EVF. FIG. 6 shows a specific example. If a frame such as a hatched portion is displayed and the photometry range is specifically shown, a subject having an appropriate luminance can be obtained by allowing the subject to fall within the frame during photographing. Further, by using the pattern generator 29, the photometric range can be continuously changed according to the zoom ratio. FIG. 7, FIG.
The figure shows the photometric pattern as the output of the pattern generator when the CCA filter is ON. In FIG. 7, the vertical axis represents time, and the horizontal axis represents the zoom ratio. A and B are horizontal pattern generation lines, and a region sandwiched between A and B is a region 2. Similarly, CD
Is a vertical pattern generation line, and a region sandwiched between C and D is a region 2 portion. Accordingly, as shown in FIG. 8, W is the lower-weighted metering, and T is the center-weighted metering, and the metering area can be changed continuously during this period, so that more photographing can be handled.

FIG. 9 and FIG. 10 are diagrams showing a change in the photometric pattern when the CCA filter is OFF, and the same operation is performed, so that the description will be omitted. In this case, a pattern signal is output from the pattern generator so that the photometry area becomes wider as the zoom ratio increases.

(Effect)

According to the present invention as described above in detail and specifically,
Correcting the exposure adjustment operation by controlling the pattern of the photometry area by identifying the imaging state of the subject according to the color temperature correction state by the color temperature correction unit and the state of the zoom ratio set by the zoom unit, It is possible to always perform optimal exposure control according to the imaging state, such as outdoor, indoor, wide or telephoto.

[Brief description of the drawings]

FIG. 1 is a block diagram of an automatic exposure compensator according to the present invention.
FIG. 2 is a block diagram of a photometric pattern generator, FIG. 3 is a specific example of a photometric pattern, FIG. 4 is a block diagram of an iris control circuit, and FIG. 5 is a block diagram of another embodiment of the photometric pattern generator. 6, FIG. 6 is a view showing a photometric pattern on the EVF, FIG. 7 is a diagram showing a change in the photometric pattern when the CCA filter is ON, FIG. 8 is a photometric pattern when the CCA filter is ON, and FIG. 9 is a CCA filter. FIG. 10 is a diagram showing a change in the photometric pattern when the CCA filter is OFF, and FIG. 10 is a diagram showing a photometric pattern when the CCA filter is OFF. In the figure, 7 is a zoom ratio detecting circuit, 8 is a CCA filter switching detecting circuit, 9 is a photometric pattern generator, 10 is an iris control circuit, 12 and 13 are first and second counter circuits, and 14 and 15 are first and second. A 2 matrix circuit, 16 is a comparator, 19 is a switch, 22 is an attenuator, 23 is a comparator, 26 is a switch, 28 is an A / D conversion circuit, and 29 is a pattern generator.

Claims (1)

(57) [Claims] 1. An exposure control means for detecting the brightness of a subject corresponding to a photometric area set in a screen and naturally adjusting an exposure state, and correcting a color temperature of illumination light illuminating the subject. A color temperature correction unit; a zoom unit that changes a photographing magnification of the subject; and a state of color temperature correction by the color temperature correction unit and an imaging state of the subject according to a zoom ratio state set by the zoom unit. Automatic exposure correction, comprising: an identification unit that performs the exposure adjustment operation performed by the exposure adjustment unit by controlling a pattern of the photometry area according to an output of the identification unit. apparatus.