JPH06332027A - Exposure controller and exposure control method - Google Patents

Abstract

PURPOSE:To provide a new exposure controller capable of photographing while blurring a background except an object without the blurring of the object even when photographing the object of high luminance. CONSTITUTION:A diaphragm device 12 is constituted of a transmissivity variable filter, the device is provided with a driving circuit 18 for varying the transmissivity of the filter, and the transmissivity of the diaphragm device and the stopping state of the diaphragm device are varied in accordance with a photographing condition. The transmissivity of the filter is controlled by the driving circuit 18 so that the transmissivity may become the smallest one at normal photographing, and when the luminance of the object is high, the transmissivity of the filter is increased in accordance with the result which is obtained when the stopping state is detected by a diaphragm position detector 19 and also the diaphragm is fully closed, so that the occurrence of a diffraction phenomenon is prevented. Also, at the time of photographing with a background blurred, the diaphragm 12 is fully closed by a driving circuit 7 and also the transmissivity is varied by the driving circuit 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure control device and an exposure control method used for optical equipment such as video cameras.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a part of the configuration of a general video camera. 1 is a photographing lens, 2 is a diaphragm device that regulates the amount of incident light, 3 is an image sensor, 4 is a buffer amplifier, 5 is an exposure control circuit, 6 is an image sensor drive circuit,
Reference numeral 7 is a diaphragm drive circuit. The exposure control circuit 5 controls the aperture control circuit 7 so that the output level of the image sensor 3 becomes constant. The exposure control circuit 5 also outputs a control signal to the image sensor drive circuit 6 to control the exposure time of the image sensor.

[0003]

The above-mentioned conventional video camera has the following problems. That is, when a very bright subject is photographed outdoors on a sunny day, the diaphragm device 2 for adjusting the amount of light incident on the image sensor is in the fully closed state, so that an optical diffraction phenomenon due to the diaphragm occurs. , The image of the subject was sometimes blurred. Further, when the aperture is narrowed down, the depth of field becomes deep, and it is difficult to photograph the background of the subject with blur.

In order to deal with such a problem, the aperture device is conventionally controlled to open by shortening the exposure time of the image pickup device or by attaching a light reduction filter having a low transmittance to the front surface of the taking lens.

However, when the exposure time of the image pickup device is shortened, the amount of light incident on the surface of the image pickup device increases, so that smear or blooming phenomenon peculiar to the image pickup device may occur and the image quality may deteriorate. In addition, when using the neutral density filter, it is necessary to attach the neutral density filter to the lens each time, and when selecting the transmittance of the filter, it is necessary to rely on the judgment of the photographer. .

The object of the present invention is to solve the above-mentioned problems,
Each time the photographer shoots, it is possible to shoot an image with a blurred background other than the main subject as easily as in normal shooting without attaching a neutral density filter to the video camera. An exposure control device and method are provided.

[0007]

In order to solve the above-mentioned problems, in the present invention, the diaphragm blades of the diaphragm device are composed of variable transmittance filters and the diaphragm device transmittance control means for changing the transmittance of the diaphragm device. Is provided and the exposure time of the image sensor is controlled while changing the transmittance of the diaphragm device, so that a blurred image of the background (that is, soft focus) or the like can be easily captured without causing a diffraction phenomenon. I made it possible.

[0008]

According to the exposure control apparatus of the present invention, it is possible to prevent the diffraction phenomenon which occurs in the state where the diaphragm is close to the diaphragm stop, which is a problem in the conventional apparatus.

Further, when a bright subject is photographed, smear or blooming does not occur even if the exposure time of the image pickup element is shortened, and the labor of attaching a neutral density filter at the time of photographing can be saved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exposure control apparatus according to the present invention will be described in detail below with reference to FIGS. 1 to 4.

FIG. 1 is a block diagram showing the configuration of an exposure control device according to the present invention.

In FIG. 1, 3 is an image pickup device mounted on an optical device such as a video camera, 1 is a taking lens, and 4 is provided between the image pickup device 3 and a signal processing circuit and exposure control circuit 5 not shown. A buffer amplifier, 6 an image pickup element drive circuit driven by the output of the exposure control circuit 5, 7 a drive circuit for driving the aperture blades of the aperture device 12, and 12 an aperture diaphragm whose aperture blades are variable transmittance filters. Device, 1
Reference numeral 8 is a drive circuit for applying a voltage to the variable transmittance filter of the diaphragm device to change the transmittance, and 19 is the diaphragm device 1.
A diaphragm position detector for detecting the position of the second diaphragm blade. The transmittance of the diaphragm device 12 can be changed as shown in FIG. 2 by the voltage applied to the electrode connected to the filter. Normally, a voltage equal to or higher than Vb shown in FIG. 2 is applied, and the device is used in a state where the transmittance is minimized. Therefore, the same exposure control as the conventional one can be performed. Here, when the brightness of the subject is increased and the shape of the aperture of the diaphragm device is gradually reduced as shown in FIGS. 3A and 3B, the above-mentioned problematic diffraction may occur. In that case, when the diaphragm position detector 19 detects a small diaphragm state, the transmittance of the diaphragm device is increased, the diaphragm is further closed, and the diaphragm is finally closed while keeping the amount of light incident on the imaging surface constant. ). As a result, it is possible to prevent the occurrence of diffraction due to the small aperture.

On the other hand, when it is desired to always make the depth of field shallow and to blur the background, the aperture is closed from the beginning as shown in FIG. The exposure may be corrected by changing the value as shown in FIG. At this time, the exposure time of the image sensor may be changed at the same time.

[0014]

As described above, in the exposure control device according to the present invention, the diaphragm device is composed of the variable transmittance filter, and the transmittance of the diaphragm device is changed according to the photographing condition. For example, when shooting a high-brightness subject, by closing the diaphragm and changing the transmittance of the diaphragm device, it is possible to prevent the occurrence of a diffraction phenomenon and prevent the image of the object from blurring. It is also possible to shoot an image in which the background other than the subject is appropriately blurred.

Further, when it is desired to take a picture with a shallow depth of field, smear and blooming are prevented by controlling the transmittance of the diaphragm device and the exposure time of the developing element to obtain a good image quality. You can take a picture.

In the above-described embodiment, the diaphragm device has been described on the premise that it is a device of the type that controls the amount of light by mechanically driving the diaphragm blades like the conventional diaphragm device. It goes without saying that may be configured as a device capable of controlling the light amount without mechanical drive.

[Brief description of drawings]

FIG. 1 is a diagram showing a part of the configuration of a video camera equipped with an exposure control device according to the present invention.

FIG. 2 is a diagram showing a relationship between a change in transmittance of a diaphragm device and an applied voltage in the exposure control device of the present invention.

FIG. 3 is a diagram showing changes in the aperture of the diaphragm device in the exposure control device of the present invention.

FIG. 4 is a diagram showing a change in transmittance of a diaphragm device in the exposure control device of the present invention.

FIG. 5 is a diagram showing a part of a configuration of a conventional video camera.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photographing lens 2 ... Aperture device 3 ... Image sensor 4 ... Buffer amplifier 5 ... Exposure control circuit 6 ... Image sensor drive circuit 7 ... Drive circuit 12 ... Variable transmittance diaphragm device 18 ... Drive circuit 19 ... Aperture position detector

Claims (5)

[Claims] 1. An exposure control apparatus comprising: a diaphragm device having a variable transmittance filter; and a transmittance control means for changing the transmittance of the variable transmittance filter. 2. An exposure control device for an optical instrument having an image sensor, comprising a diaphragm device having a transmittance variable filter, diaphragm device driving means for changing the diaphragm state of the diaphragm device, and the transmittance variable device. The transmittance control means for changing the transmittance of the filter, the diaphragm state detecting means for detecting the diaphragm state of the diaphragm device, the diaphragm based on the output of the image pickup device and the output of the diaphragm state detecting means. An exposure control device, comprising: an apparatus drive unit and an exposure control unit that controls the transmittance control unit. 3. An exposure control method in an optical apparatus having an image sensor, comprising: a diaphragm device having a transmittance variable filter, diaphragm device driving means for changing a diaphragm state of the diaphragm device, and a variable transmittance filter. Transmittance control means for changing the transmittance, aperture state detection means for detecting the aperture state of the aperture device, and drive of the aperture device based on the output of the image sensor and the output of the aperture state detection means Means and an exposure control means for controlling the transmittance control means, the exposure control device having the diaphragm device in a fully closed state to change the transmittance of the transmittance variable filter to perform exposure correction. An exposure control method characterized by performing. 4. An exposure control method in an optical apparatus having an image pickup device, comprising: a diaphragm device having a variable transmittance filter, diaphragm device driving means for changing a diaphragm state of the diaphragm device, and the variable transmittance filter. Transmittance control means for changing the transmittance, aperture state detection means for detecting the aperture state of the aperture device, and drive of the aperture device based on the output of the image sensor and the output of the aperture state detection means Means and exposure control means for controlling the transmittance control means, the exposure device having an exposure control means to fully close the diaphragm device and the transmittance of the transmittance variable filter and the exposure time of the image sensor. And an exposure control method characterized by changing. 5. An exposure control method for an optical apparatus having an image pickup device, comprising: a diaphragm device having a transmittance variable filter, diaphragm device driving means for changing a diaphragm state of the diaphragm device, and the transmittance variable filter. Transmittance control means for changing the transmittance, diaphragm state detecting means for detecting the diaphragm state of the diaphragm device, and diaphragm device driving means based on the output of the image sensor and the output of the diaphragm state detecting means. And an exposure control unit that controls the transmittance control unit, and normally, the transmittance of the variable transmission filter is kept at a minimum, and the diaphragm device is in a small diaphragm state. When the diaphragm state detecting means detects that, the exposure control is performed by fully closing the diaphragm device and changing the transmittance of the variable transmittance filter.