JPH0465585B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an imaging device that controls an aperture or a gain according to the output level of a portion of an imaging screen.

(Prior art) Conventionally, this type of device obtains a photometric signal by weighting the signal of a part of the object field in a predetermined luminance signal distribution of the object field within a predetermined photometric field of view. It is known to perform exposure control by adjusting the aperture of a diaphragm disposed in front of the imaging surface so that the level of this photometric signal is constant. However, especially when a solid-state image sensor is used as an image sensor and also used as a photometric element, the dynamic range of the solid-state image sensor is narrow, so even if the luminance signal is weighted, highly accurate exposure control is not possible. It is often inappropriate. Moreover, the control required for weighting is complicated, making it unsuitable for miniaturization. In addition, conventional methods correct the reference level by smoothing the gate pulses used to define the photometry area, but since shading and dark current unevenness occur in imaging devices, errors occur when the photometry area is changed. There are drawbacks that arise.

(Purpose) The present invention has been made in view of the above points,
It is an object of the present invention to provide a new and advantageous imaging device that can satisfactorily eliminate the above-mentioned disadvantages of conventional photometry methods.

(Examples) The present invention will be described in detail below based on Examples.

FIG. 1 shows an example of the configuration of an imaging device according to the present invention, in which 1 is a photographic lens, 2 is an aperture, and 3 is an image sensor as an imaging means. The light enters the light receiving surface of the image sensor 3 and is photoelectrically converted there. 4 is a preamplifier circuit;
Reference numeral 5 denotes a process amplifier circuit, and the scanning signal (imaging signal) from the image sensor 3 is amplified and processed by the preamplifier circuit 4 and the process amplifier circuit 5, and then outputted to an output terminal 6 as a standard television signal, that is, a video signal. be done. Reference numeral 8 denotes a synchronization signal generation circuit, and scanning within the image pickup device 3 is performed based on vertical and horizontal synchronization signals 9 from the synchronization signal generation circuit 8. Reference numeral 10 denotes a photometric visual field selection circuit as a selection means, which generates a mask signal 11 for selectively passing only a portion corresponding to a predetermined photometric visual field based on the vertical and horizontal synchronizing signals 9. Reference numeral 7 denotes a modulation circuit that masks the luminance signal Y from the process amplifier circuit 5 with a mask signal 11 from the photometric field selection circuit. 14 is an arithmetic circuit as a signal processing means for obtaining a photometric signal by smoothing (that is, averaging) or integrating the output of the modulation circuit 7; This is a memory circuit serving as a memory means for storing correction data corresponding to the area and position of a predetermined photometric visual field selected by the selection signal 12. 15 is a gain control circuit as a correction means for amplifying the photometric signal from the arithmetic circuit 14 by a gain determined by the correction data from the storage circuit 13; 16 is a gain control circuit that amplifies the photometric signal from the arithmetic circuit 14 by a gain determined by the correction data from the storage circuit 13; This is an adjustment circuit as an adjustment means for adjusting the aperture amount of the process amplifier 5 or the gain of the process amplifier 5.

In the above configuration, the modulation circuit 7 includes, for example, an amplitude modulation circuit or a gate circuit. The arithmetic circuit 14 includes, for example, a smoothing circuit, an average value circuit, an integrating circuit, and the like. A variable gain amplifier circuit is added to each of the modulation circuit 7 and the arithmetic circuit 14, and a signal proportional to the area of the photometric field of view (not weighted) is obtained from the photometric field of view selection circuit 10 or the memory circuit 13. The gain may also be controlled. The storage circuit 13 can also be configured with, for example, a ROM (Read Only Memory) that stores gain control values corresponding to the type of predetermined photometric field of view. Note that the arithmetic circuit 14 is
For example, when configured with a smoothing circuit, each smoothing constant is determined depending on a predetermined photometric field of view, so it may be configured with a plurality of smoothing circuits.

Next, FIG. 2 is an embodiment diagram showing an example of a photometric field of view according to the present invention. FIG. 3 is an embodiment showing the input/output characteristics of the gain control circuit 15 based on the embodiment of FIG. 2. In FIG. A ₁ and b ₁ in Fig. 2 indicate, for example, average photometry and partial photometry, and their areas are a ₁ :
When b ₁ =10:1, the gains of the gain control circuit shown in FIG. 3 should be set to gain characteristic lines a ₂ and b ₂ that are inversely proportional to the area, respectively. Here, the slope of a ₂ and b ₂ is 1:10. However, in the present invention, the gain characteristic lines of a ₃ and b ₃ are set with unique weights assigned to the photometric visual field patterns of a ₁ and b ₁ , respectively. Therefore, the slopes of a ₃ and b ₃ are not proportional at all. Of course, although FIGS. 2 and 3 above show examples with two types of photometric fields of view, the present invention can also be applied to cases where there are three or more types of photometric fields of view.

In this case, as in the embodiment shown in FIG. 3, the storage means stores the gain of the gain control circuit, that is, the correction data corresponding to the slope shown in FIG. 3, for each photometric field of view. Since the gains of the gain control circuits 15 read out by the selection signals 12 of the selection circuits 10 are adjusted, the photometry level in each photometry field can be finely adjusted.

In particular, with this configuration, even if the device has significant shading, the memory circuit 13
If data for correcting the error is stored in advance, the error can be easily corrected even when the photometric field of view is changed.

In addition, since the brightness level is generally relatively high above the field of view, if the photometric field of view includes the upper part, for example, by storing data to correct the gain slightly higher in the memory circuit 13, it is possible to correct the backlight situation. You can prevent things from happening.

In addition, in the present invention, when switching the photometric field of view for a subject with a uniform brightness distribution, the exposure level or sensitivity level will differ, but it is certain that this will not cause any inconvenience for actual general subjects. I was caught.

(Effects) A storage means is provided to store correction data in advance for each photometric field of view, and as the photometric field of view is switched, the photometric information is corrected using the correction data, so the size and position of the photometric field of view are It is possible to correct shading errors, errors due to dark current unevenness, errors due to backlighting, etc., for which accurate photometric information is obtained according to the situation.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an example of the configuration of an imaging device, FIG. 2 is a diagram showing an example of a photometric field of view, and FIG. 3 is a diagram showing gain characteristics corresponding to the photometric field of view shown in the second figure. 1 is a lens, 2 is an aperture, 3 is an imaging device as an imaging means, 4 is a preamplifier circuit, 5 is a process amplifier circuit, 7 is a modulation circuit, 8 is a synchronization circuit, 9 is a vertical and horizontal synchronization signal, 10 is 11 is a mask signal, 12 is a selection signal, 13 is a memory circuit as a memory means, 14 is an arithmetic circuit as a signal processing means, 15 is a gain control circuit as a correction means, and 16 is a photometric visual field selection circuit as a selection means. This is an adjustment circuit.

Claims (1)

[Scope of Claims] 1. Imaging means for converting an optical image formed on an imaging surface into an electrical signal; selection means for selecting a part of the imaging surface as a photometric area; and selection by the selection means. gain control means for performing predetermined signal processing on the output signal of the imaging means corresponding to the photometry area corresponding to the selected photometry area and outputting a control signal for controlling the aperture; An imaging device comprising: storage means for storing gain correction information; and correction means for correcting the output of the gain control means according to the gain correction information in the storage means.