JPH07209694A - Automatic iris camera - Google Patents

Abstract

PURPOSE:To obtain appropriate exposure even for brightness in a range which can not be covered by an electronic shutter alone in a camera having an automatic iris function. CONSTITUTION:In this camera, the exposure is adjusted by a liquid crystal shutter 1 and the electronic shutter 2. A light quantity detection part 4 detects a light quantity from a subject to set the liquid crystal shutter to a normal mode or a polarized mode in accordance with the light quantity. By concurrently using the shutter 1 and the shutter 2, the appropriate exposure is obtained even in the range which can not be covered by the shutter 2 alone, for example, a highlight part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera having an auto iris function, and more particularly to an auto iris camera having a so-called electronic shutter auto iris function.

[0002]

2. Description of the Related Art As is well known, in cameras such as silver halide cameras and monitor cameras for monitoring, it is required to adjust the amount of incident light according to the brightness of a subject and photograph an appropriate image.

As is well known in conventional cameras, an aperture is provided to adjust the amount of light, and the aperture is adjusted according to the brightness of the subject to adjust the amount of light incident on the camera. Such adjustment of the diaphragm is usually performed automatically. That is, the amount of incident light is detected by the sensor, and the state of the diaphragm is adjusted accordingly. The amount of incident light has been adjusted by using such adjustment of the aperture together with control of the opening / closing time of the shutter.

There is also known a camera using a so-called electronic shutter for controlling the incident time of light from a subject in a wide range and adjusting the light amount. In such a camera, the CCD is used in the same way as the normal shutter speed.
Depending on the brightness of the subject,
By setting 0, 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000, 1/10000 second, the amount of accumulated charge was controlled and the auto iris function was used.

[0005]

However, the brightness of the subject is distributed in the range of 0 to about 150,000 lux depending on the type of the subject. On the other hand, the shutter speed range of the electronic shutter is about 1/50 to 1/10000 as described above.
It takes about a second and cannot cover all the brightness of the subject as described above. For example, there has been a problem that a very bright highlight portion cannot be properly exposed.

The present invention has been made in view of the above-mentioned problems, and by interlocking with the shutter speed of an electronic shutter, an image is taken with an appropriate incident light amount for a wide range of brightness of a subject. It is an object to provide an auto iris camera that can.

[0007]

According to the present invention, an auto iris camera having an auto iris function for automatically adjusting the amount of incident light in accordance with the brightness of a subject can adjust the light receiving time according to the brightness of the subject. The electronic shutter means set in a number of stages, the light quantity adjusting means composed of liquid crystal whose light transmittance changes according to the applied voltage, the light quantity detecting means for detecting the incident light quantity, and each means The control means controls the electronic shutter means according to the incident light quantity detected by the light quantity detecting means to set the light receiving time, and changes the voltage applied to the liquid crystal of the light quantity adjusting means. Then, the transmittance of the liquid crystal is set.

[0008]

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 shows an embodiment of an auto iris camera according to the present invention. As shown in the figure, the camera has a liquid crystal shutter 1, an electronic shutter 2, a film 3, a light amount detection unit 4, and a control unit 5. It should be noted that components not related to the features of the present invention, such as lenses, are not shown.

The liquid crystal shutter 1 is a light quantity adjusting means, is arranged in an incident light path, and adjusts the quantity of incident light.
The liquid crystal shutter 1 is composed of a pair of transparent electrodes 11 and 12 and a liquid crystal 13 sandwiched between the transparent electrodes 11 and 12. When the voltage applied between the transparent electrodes 11 and 12 is changed by the control voltage sent from the control unit 5 which will be described later, the liquid crystal 13 is changed to the normal mode or the polarized mode according to the change, and the transparency of the liquid crystal 13 is changed. The liquid crystal shutter 1 has an iris function by changing the light transmittance of the liquid crystal 13 in this way.

The electronic shutter 2 sets the light receiving time in a number of stages according to the brightness of the subject, and the light receiving time is, for example, 1/60, 1/125, 1/250, 1/500, 1 /. 1000, 1/2000, 1
The shutter is set to / 4000, 1/10000 second. The film 3 is a silver salt film in this embodiment, but in the case of an electronic camera or the like, a CCD may be used instead of the film. In that case, the exposure time of the CCD may be controlled by the electronic shutter 2.

The light amount detecting section 4 is a light amount detecting means for detecting the amount of incident light, and for example, a CdS cell is used. The control unit 5 supplies a control voltage for setting the mode of the liquid crystal shutter 1 to the transparent electrodes 11 and 12 of the liquid crystal shutter 1 according to the light amount detection signal sent from the light amount detection unit 4, and at the same time, opens and closes the electronic shutter 2. The control unit outputs a control signal to be controlled to the electronic shutter 2.

According to this camera, the quantity of incident light is detected by the quantity of light detecting section 4, the mode of the liquid crystal shutter 1 is set from the control section 5 according to the detected quantity of light, and the opening / closing time of the electronic shutter 2 is set. Control. Therefore, even when an appropriate exposure amount cannot be obtained only by controlling the shutter speed by the electronic shutter 2, it is possible to obtain an appropriate exposure amount by using the liquid crystal shutter 1 together.

[0013]

According to the present invention, the exposure amount is adjusted by using the light amount adjusting means composed of liquid crystal together with the electronic shutter means. Therefore, it has an auto iris function that can obtain an appropriate exposure amount even in a range that cannot be covered by using only the electronic shutter.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an auto iris camera according to the present invention.

[Explanation of symbols]

 1 liquid crystal shutter 2 electronic shutter 3 film 4 light amount detector 5 controller

Claims (1)

[Claims] 1. An auto-iris camera having an auto-iris function for automatically adjusting the amount of incident light according to the brightness of a subject, wherein the camera sets the light-receiving time in a number of stages according to the brightness of the subject. An electronic shutter means, a light quantity adjusting means composed of a liquid crystal whose light transmittance changes according to an applied voltage, a light quantity detecting means for detecting an incident light quantity, and a control means for controlling each of the above means. The control unit controls the electronic shutter unit according to the incident light amount detected by the light amount detection unit to set the light receiving time, and a voltage applied to the liquid crystal of the light amount adjustment unit. An auto iris camera characterized by changing the transmittance of the liquid crystal.