JPS61145971A - Image pickup device - Google Patents

Abstract

PURPOSE:To make it possible to pick up an object within a scope of broad luminance in the simple constitution of image without causing blurring due to a manual handling of camera by controlling a image pickup time according to a focal distance and a luminance state of the object. CONSTITUTION:Once a power source switch is turned on, an object luminance information is inputted into an arithmetic control circuit 10 by operating a photometry circuit 8 and after that an optimum shutter speed Tv and a diaphragm value Av are calculated on the basis of object luminance. Furthermore, a control circuit 10 discriminates a focal distance of lens after detecting a condition of switch 9. If the switch 9 is off; that is to say, its lens is in a state of wide angle, it is necessary to wait for releasing. As a sensitivity, in this case, doesn't increase, S/N of image is acceptable. If the switch is on; that is to say, its lens is for a telescopic use, it is essential to decide whether Tv exceeds a blurring limit speed Tvo or not. When Tv is above its limit, it waits for release as it is and if Tv is below the limit, the control circuit 10 allows its sensitivity to be double by improving a gain of a signal processing circuit 6 and a shutter 4 shall be controlled to increase its Tv by one degree through the control circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an imaging device having an imaging system whose sensitivity can be electrically changed.

(Prior Art) In an imaging device capable of telephoto shooting using a zoom lens or an interchangeable lens, when the focal length of the lens is increased, camera shake is likely to occur, especially when the imaging time is relatively long.
This camera shake becomes more likely to occur.

Therefore, in order to prevent camera shake, conventional film cameras use a shutter to shorten the exposure time to solve this problem.

However, solid-state image sensors such as COD and MOS, and image pickup tubes, etc., do not have a high enough sensitivity to release a sufficiently high-speed shutter for all kinds of subjects, and the shutter speed does not need to be that high for non-telephoto shooting. It is also known that camera shake does not occur.

(Objective) It is an object of the present invention to provide an imaging device that can overcome the drawbacks of the prior art as described above.

It is an object of the present invention to provide an imaging device capable of capturing an image of a subject in a wider luminance range with a simple configuration and without camera shake. (Example) The content of the present invention will be explained in detail below with reference to the attached drawings.

Figure 1 is a block diagram of the electrical system of an embodiment of the present invention. In the figure, 1 is an optical system for forming a subject image, 2 is an aperture, and 3 is a division of incident light from the subject into a photometry system and an imaging system. 4 is a shutter, 5 is an image sensor such as a COD image sensor or an image pickup tube, and 6 is a signal processing circuit.
, 6 constitute an imaging means. 7 is the recording section, 8
is a photometric circuit. To simplify the explanation, the optical system of this imaging device uses a zoom lens having only two focal lengths: wide-angle and telephoto, and 100 is a focus switching member. A switch 9 is turned on and off in conjunction with the operation of the focus switching member 100, and is turned off when the camera is in wide-angle mode and on when it is in telephoto mode. Reference numeral 10 denotes an arithmetic control circuit as a control means, which inputs subject brightness from the photometry circuit 8 through line b, for example, and calculates the shutter speed (Tv) and aperture value (Av). Also, calculation
Depending on the determination result, the aperture is controlled through lines a and C and the shutter is controlled, and the gain of the signal system is switched and the display 11 is driven through lines d and e. Note that this circuit is configured to also detect the switching states of the release switch and other switches and control the timing.

The above is a block diagram of an electrical system showing one embodiment of the present invention, and the operation of the arithmetic control circuit 10 will be explained below with reference to the flowchart of FIG. 2.

When a power switch (not shown) is turned on, the photometry circuit 8 is activated at step (3), and object brightness information is input to the arithmetic control circuit IO through line b. Then, at ■, the arithmetic control circuit 10 calculates the optimal Ay and Tv based on the subject brightness.
The arithmetic control circuit 10 detects the state of the switch 9 and determines the focal length of the lens. If the switch 9 is off, that is, in wide-angle mode, press O to wait for release. In this case, the sensitivity is not increased, so the S/N of the image is good.

If the switch 9 is on, that is, in telephoto mode, it is determined in step 2 whether Tv is greater than or equal to the camera shake limit speed Tvo. TV
If Tv is above the camera shake limit, wait for release in [phase], and if Tv is below the camera shake limit, the arithmetic control circuit IO increases the gain of the signal processing circuit 6 to double the sensitivity, and ■ Tv is set to 1 by the arithmetic control circuit.
The shutter 4 is controlled so as to increase the amount by the amount. In this state T
It is determined in (2) whether or not v has exceeded the camera shake limit speed To. If it is more than To, the image quality will be somewhat inferior due to the sensitivity increase, but it will be possible to take pictures without camera shake.For this reason, the arithmetic and control circuit 10 will drive the display 11 to emit light from, for example, a green LED, and display the image. and wait for the release in [phase]. If in (■) it is still below TO, it is not possible to eliminate camera shake even if the sensitivity is increased. Light up the red LED to indicate this, and wait for the release with [phase].

After that, when it is detected that the release button (not shown) has been pressed in [phase], the arithmetic control circuit 10 controls the aperture 2 and the shutter 4.
is driven to expose the image sensor 5 to light, and then the recording section 7 records the image information of the subject on the recording medium at an appropriate timing.

The above is the operation of one embodiment of the present invention shown in FIG.

Here, to simplify the explanation, only the case where the sensitivity increase is doubled has been described, but multiple stages of sensitivity increase states may be provided.

Additionally, in this example, if the shutter speed is not sufficient even if the sensitivity is increased with a telephoto system, an example of a configuration is shown in which the camera shoots at a speed that can cause camera shake, but underexposure is acceptable even if the camera shake is at the limit. If there is a limit, it is of course possible to increase the shutter speed to that extent.

The lens can be a zoom lens built into the imaging device, an interchangeable single focus lens, or an interchangeable zoom lens.In particular, in the case of an interchangeable lens, a mark corresponding to the focal length is placed on the lens side to facilitate imaging. A detection member for detecting this may be provided on the device side.

Furthermore, in the above description, the value Tv expressed by l/T=2TV is used as the shutter speed for the exposure time T by the shutter 4.

Further, as the aperture value, a value Ay expressed by F2=2AV for the F number F is used.

Further, the shutter speed according to the present invention may be the effective accumulation time T' in the image sensor 5 instead of the exposure time T, and since the method of controlling the accumulation time f is well known in the past, I will not specifically discuss it here.

In addition, in order to detect the subject brightness, in this embodiment, for example, SP
Although a photometric circuit 8 including C and the like is provided separately, it is also possible to smooth the luminance component of the output of the image sensor 5 and detect the subject luminance based on this smoothing.

Also, as a method of increasing the sensitivity of the imaging means, the signal processing circuit 6
The gain of the amplifier within the signal processing circuit 6 may be variably controlled, or a plurality of amplifiers with different gains may be provided within the signal processing circuit 6.
Among these amplifiers, the uII image element output may be guided to the recording unit 7 through which amplifier.

It is also possible to change the sensitivity of the image sensor itself.

For example, when an image pickup tube is used as an image pickup device, changing the target voltage changes the sensitivity, and the present invention also includes control of the sensitivity itself of such an image pickup device.

(Effects) As explained above, according to the device of the present invention, when a lens with a relatively long focal length is used, depending on the brightness of the subject, the sensitivity of the image sensor can be electrically increased and the shutter speed can be set to a speed higher than the limit for camera shake. This prevents image deterioration due to camera shake or a subject moving at high speed.

Furthermore, when an image is captured using a lens with a relatively short focal length, the S/N ratio of the image quality can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an electrical system showing an embodiment of the imaging apparatus of the present invention, and FIG. fi42 is a flow chart for explaining the operation example of FIG. 1. 1. Optical system 2. Aperture 3, beam splitter 4, shutter 5, image sensor 6. Signal processing circuit 7, recording section
8. Photometric circuit 9, switch lO9 calculation control circuit 11, display

Claims (1)

[Scope of Claims] Imaging means for converting a subject image into a predetermined electrical signal; an optical system for inputting the image into the imaging means; and a sensitivity of the imaging means depending on the focal length of the optical system and the brightness state of the subject. and a control means for controlling the imaging time;
An imaging device having: