JP2560791B2 - Imaging device - Google Patents

Description

The present invention relates to an image pickup apparatus in a television camera, a video camera or the like, and more particularly to an aperture control in an image pickup system using an image pickup means such as CCD having an electric shutter function. The present invention relates to an image pickup apparatus in which the shutter speed of the image pickup means is changed in conjunction with the above to substantially expand the dynamic range of aperture control.

(Prior Art) Conventionally, when a subject having a high brightness is photographed by an image pickup apparatus such as a television camera, an appropriate exposure amount may be obtained when a diaphragm value of a photographing system is a maximum diaphragm value or a value close to a close value. In such a case, insert the ND filter provided in the image pickup device at a predetermined position in the shooting system to substantially reduce the aperture value and shift the aperture operation area from the maximum aperture value to the small aperture value. The method of shooting is adopted. However, the image pickup device in which the ND filter is detachably attached to the image pickup system has various problems in photographing. For example, when shooting from news coverage, etc., when moving from indoors with many low-brightness subjects to outdoors with high-brightness, the exposure becomes overexposed. There was a problem that good shooting could not be performed.

(Problems to be Solved by the Invention) The present invention relates to an image pickup apparatus such as a television camera using an image pickup unit such as a CCD having an electric shutter function, which uses an aperture control signal in an image pickup system. The shutter speed control circuit that has the function of controlling or selecting the shutter speed of is used to substantially expand the aperture value control range of the aperture control, and for subjects with a wide luminance range from low-luminance subjects to high-luminance subjects. It is an object of the present invention to provide an imaging device that can easily obtain an appropriate exposure amount.

(Means for Solving Problems) Imaging having an auto iris circuit for controlling an aperture diameter of a diaphragm provided in a photographing system and an imaging means having a shutter function for forming a subject image by the photographing system In the device, the maximum F value and the minimum F value of the diaphragm are controlled by the diaphragm operation unit.
A value is set and stored in the detection circuit, and the shutter speed control circuit determines the F value of the aperture based on the signal from the auto iris circuit and the maximum F value or the minimum F value stored in the detection circuit. It is characterized in that the shutter speed is controlled by using a shutter function provided in the image pickup means so that the value changes between a preset maximum F value and minimum F value.

(Embodiment) FIG. 1 is a block schematic diagram of an embodiment when the present invention is applied to an image pickup apparatus of a television camera.

In the figure, reference numeral 1 denotes a photographing system, which has an aperture 1a.
Reference numeral 2 is a three-primary-color separation prism, 3 is an image pickup means, and imaging plates 3a, 3b, 3c such as CCDs having an electric shutter function corresponding to red, green, and blue arranged on the exit surface of the three-primary-color separation prism 2 are provided. Is made up of. Reference numeral 4 denotes an amplifier circuit, which is a video amplifier 4a corresponding to the three primary color image pickup plates 3a, 3b, and 3c,
It consists of 4b and 4c.

An encoder 5 converts output signals from the video amplifiers 4a, 4b and 4c into predetermined signals.

An iris control circuit 12 controls the aperture of the aperture 1a. 6 is an auto iris circuit, and an amplifier circuit 4
A predetermined aperture value signal is sent to the iris control circuit 12 by using the output signal from the. A detection circuit 7 comprises a minimum F value detection circuit 7a for detecting the minimum aperture value and a maximum F value detection circuit 7b for detecting the maximum aperture value. A shutter speed control circuit 8 controls the shutter speed of the image pickup means 3 automatically and manually. Reference numeral 9 denotes a changeover switch which, when controlling the shutter speed, switches between a mode for performing control in conjunction with the auto iris and a mode for manually selecting the shutter speed. Reference numeral 10 denotes a manual selection unit, which has a mode in which the shutter speed of the image pickup means 3 is manually selected.

 A drive circuit 11 drives and controls the image pickup means 3.

In this embodiment, the light flux from the subject that has passed through the photographing system 1 is separated into three color lights by the three primary color separation prism 2 and is incident on the image pickup plates 3a, 3b and 3c of the image pickup means 3, respectively. The electric signal relating to the subject image output from the image pickup means 3 is input to the encoder 5 and the auto iris circuit 6 which are respectively amplified by the video amplifiers 4a, 4b and 4c of the amplifier circuit 4. Of these, the auto iris circuit 6 outputs an auto iris signal, and this signal is input to the minimum F value detection circuit 7a and the maximum F value detection circuit 7b. In the circuits 7a and 7b, the F value signal, which is each aperture value to be detected, which is arbitrarily set by the aperture operation unit (not shown), is compared with the input signal, and when they match, the F value detection signal is output. To do. The shutter speed control circuit 8 operates by inputting the output signals of the circuits 7a and 7b when the changeover switch 9 is in the shutter speed control mode linked with the auto iris.

2 to 5 show the operation of the shutter speed control circuit 8 at this time, and FIGS.
The horizontal axis in the figure is the time axis and indicates the same time. In FIG. 2, the straight line A is the signal level indicating the open end of the diaphragm.
A straight line B shown by a dotted line is the minimum F value set by the diaphragm operation unit, and shows the signal level of the minimum F value detected by the minimum F value detection circuit 7a. Curve C shows the auto iris signal (F value). A straight line D shown by a dotted line is the maximum F value set by the diaphragm operation unit, and the maximum F value detection circuit 7b shows the signal level of the maximum F value to be detected. Straight line E
Indicates a signal indicating the stop edge of the stop. In FIG. 3, F represents the output signal from the minimum F value detection circuit 7a,
In FIG. 4, G represents the output signal from the maximum F value detection circuit 7b, and in FIG. 5, H represents the shutter speed. When a large amount of exposure light is incident on the image pickup unit 3,
When the auto iris signal C is shifted to the squeezing side E and coincides with the signal level D which is the maximum value of the F value set in advance by the iris operating section (time t1), the maximum F value detecting circuit is provided as shown in FIG. 7b outputs an F value detection pulse, and the shutter speed control circuit 8 which has detected this output pulse shifts the shutter speed to the faster side by using the shutter function provided in the image pickup means, and the auto iris signal C shifts to the open side. . When the exposure amount at this time is large, the auto iris signal C shifts to the aperture stop side E again, and when it coincides with the signal level D which is the maximum F value (time t2), the maximum F value detection circuit 7b.
Outputs the F value detection pulse again, and the shutter speed control circuit 8 shifts the shutter speed to the faster one,
The auto iris signal C shifts to the open side. Next, when the amount of exposure becomes small, the auto iris signal C shifts to the open side, and when it coincides with the signal level B which is the minimum value of the F value set in advance by the diaphragm operation unit (time t3), the minimum F value detection circuit 7a As shown in FIG. 3, the shutter speed control circuit 8 which outputs an F value detection pulse and detects this output pulse
Shifts the shutter speed to the slower side, and the auto iris signal C shifts to the aperture stop side E. Thus, the aperture value is controlled so that the F value fluctuates within a preset range. In the mode in which the selector switch 9 manually selects the shutter speed, the shutter speed control circuit and the auto iris circuit are disconnected, and in this case, the shutter speed output signal provided by the manual selection unit 10 is input to the shutter speed control circuit 8. Becomes a signal,
Shutter speed control signal H based on the obtained input signal
Is output to the drive circuit 11 of the image pickup means 3.

As described above, in the present embodiment, the exposure amount incident on the image pickup unit is appropriately controlled by automatically or manually controlling the shutter speed of the image pickup unit using a signal related to the aperture value of the aperture arranged in the image pickup system, This facilitates obtaining a good image on a subject having a wide luminance range.

(Effects of the Invention) The image pickup apparatus of the present invention enables (a) operation with proper exposure even when subject brightness changes greatly, such as when moving from indoors to outdoors and shooting, and the ND filter is inserted and removed. It is possible to achieve an imaging device that eliminates the hassle of operations and the like.

(B) FIG. 6 is an example showing the relationship between the brightness of the subject and the F value of the aperture when the shutter speed is automatically controlled in the present invention. As shown in the figure, the minimum detection F
Since the aperture can be fixed within a certain range by setting the maximum value and the maximum detected F value, by setting the detection level to a certain specific F value, it is possible to perform imaging in consideration of the depth of focus with priority to the aperture. .

(C) The optical performance of the photographic system is F-number for normal TV cameras, etc.
It is set to be the best within the range of 5.6 to 8. Therefore, by setting the detection level of the F value within the above range, it is possible to always take good images.

It has features such as

[Brief description of drawings]

FIG. 1 is a block schematic diagram of an embodiment when the present invention is applied to an image pickup apparatus of a television camera, FIG. 2 is an explanatory diagram of an auto iris signal, and FIG. 3 is an explanation of an output signal from a minimum F value detection circuit. 4 and FIG. 4 are explanatory diagrams of the output signal from the maximum F value detection circuit, FIG. 5 is an explanatory diagram of changes in shutter speed, and FIG. 6 is an explanatory diagram showing the relationship between the brightness of the subject and the F value. . In the figure, 1 is a photographing system, 1a is a diaphragm, 2 is a three-color separation prism, and 3
Is a photographing means, 4 is an amplification circuit, 5 is an encoder, 6 is an auto iris circuit, 7 is a detection circuit, 8 is a shutter speed control circuit, 9 is a changeover switch, 10 is a manual operation unit, 11 is a drive circuit, and 12 is an iris control. Circuit.

Claims (1)

(57) [Claims] 1. An image pickup apparatus having an auto-iris circuit for controlling an aperture diameter of a diaphragm provided in a photographing system and an image pickup means having a shutter function for forming a subject image by the photographing system. Depending on the part, the maximum F of the diaphragm
The value and the minimum F value are set and stored in the detection circuit, and the shutter speed control circuit is based on the signal from the auto iris circuit and the maximum F value or the minimum F value stored in the detection circuit. An image pickup apparatus characterized by controlling a shutter speed by using a shutter function provided in the image pickup means so that the F value of the aperture changes between a preset maximum F value and minimum F value. .