JPH11164191A - Digital camera - Google Patents

Abstract

(57) [Problem] To provide a digital camera capable of operating in a viewfinder mode with a simple configuration without lowering a frame rate even when a subject has low illuminance. Based on information from a light amount detecting unit, a system controller appropriately drives an aperture and a predetermined shutter speed to take in an optical image of an appropriate amount of exposure, and the optical image signal is transmitted to an image sensor. In a digital camera that performs predetermined signal processing and displays an image on the liquid crystal display unit 9 after amplification by the amplifying unit 5 and brightness information from the light amount detecting unit, the aperture is released by the system controller. When the shutter is driven at a speed lower than the predetermined shutter speed, the amplification factor of the amplifying unit is controlled according to the information from the light detecting unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention has a liquid crystal display,
It relates to a digital camera that records an image signal electronically captured by an imaging means such as a CCD in a recording unit such as a memory card.More specifically, an image is displayed on a liquid crystal display unit based on a video signal output from an imaging device. The present invention relates to a digital camera for displaying.

[0002]

2. Description of the Related Art In a conventional finder mode operation of a digital camera, the brightness of an object is determined by using a photometric value obtained from an external photometric sensor or an output level of an image pickup device, so that an aperture value or a shutter speed or the like is determined. Exposure conditions are determined, and control is performed so that an image with appropriate brightness is obtained.

Therefore, when the subject to be imaged is relatively bright, control is performed so that the brightness of the subject becomes appropriate by reducing the aperture diameter, increasing the shutter speed, or the like. On the other hand, when the subject to be imaged is darker than a certain level, the aperture diameter is increased, and when the subject is darker, long-time exposure is performed by controlling the shutter speed to be a long shutter, so that appropriate brightness is obtained. So that it can be imaged.

[0004]

In the above prior art, when a subject to be imaged is dark, long-time exposure is performed so that the brightness becomes appropriate. In this case, since the image signal cannot be read from the image sensor during the exposure, the same image must be output to the liquid crystal finder during the exposure period in the finder mode. There was a problem that it would decrease.

[0005] To solve the problem of the reduction of the frame rate, a device that solves the problem by increasing the gain by a complicated configuration is also provided, but it is known that the cost is high.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to operate the finder mode without reducing the frame rate with a simple configuration even when the subject has relatively low illuminance. Is to be able to

[0007]

In order to solve the above-mentioned problems, the present invention provides a system controller in which a diaphragm and a predetermined shutter speed are appropriately driven by information from light amount detecting means for detecting the brightness of a subject. While taking in an optical image with an appropriate amount of exposure, the optical image is converted into an electric image signal using an image pickup device, and the image signal is amplified by an amplification unit. When the brightness information from the light amount detecting means releases the aperture by the system controller and is driven at a predetermined shutter speed or less (that is, in the case of low illuminance), The amplification factor of the amplifying means is controlled in accordance with information from the light detecting means.

According to the present invention, in the finder mode operation for observing the subject with the finder, if the entire subject has low illuminance, the system controller determines from the output signal from the light quantity detecting means that the quantity of light is insufficient, and When the shutter is released and the shutter speed becomes a long shutter, the frame rate of the finder output is controlled by controlling the signal amplification rate of the amplifier circuit that amplifies the image pickup signal so that the shutter speed does not become the long shutter. An image having a desired brightness can be output to the finder without lowering the brightness, and the digital camera can be enhanced in function.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of the configuration of an embodiment of the present invention, in which the same parts are denoted by the same reference numerals, and in the figure, 1 is an imaging lens, 2 is an aperture, 3 is an imaging device, 4 is a sample hold, and 5 is An amplifier, 6 is an A / D converter, 7 is a signal processing unit, 8 is a D / A converter, 9 is a liquid crystal display unit (finder), 10 is a timing generator, 11 is a system controller, 12 is a recording unit, and 13 is Work buffer,
Reference numeral 14 denotes a photometric element (light amount detecting means), and 15 denotes a video amplifier. Next, the operation in such a configuration will be described. Photographing, transfer of various data, and other processes in the digital camera are controlled by the system controller 11. The system controller 11 includes a CPU,
It is composed of a ROM for storing the execution program, a RAM for storing necessary data, and the like. Here, when observing the subject with the finder, the finder mode is selected by the mode detection means (not shown), whereby the system controller 11 instructs the timing generator 10 and the signal processing unit 7 to be in the finder mode. Instruct. When the finder mode is instructed, the timing generator 10 outputs a CCD drive pulse to the image sensor 3. The driving pulse at this time is different from the driving pulse at the time of capturing an image, and is configured to thin out pixel data in the vertical direction. On the other hand, the signal processing unit 7 performs settings so as to perform processing corresponding to the finder mode. Further, the system controller 11 controls the opening and closing of the aperture 2 based on a signal indicating the brightness of the subject detected by the photometric element 14 and sends a predetermined shutter speed setting code to the timing generator 10. By outputting, the proper exposure is obtained.

With this setting, the subject image is formed on the image sensor of the image pickup device 3 via the image pickup lens 1 and the aperture 2, and an analog video signal is output via the sample hold 4. The analog video signal is amplified by the amplifier 5 so as to have a predetermined signal amplitude, then converted into a digital signal by the A / D converter 6, and then output to the signal processing unit 7. The amplifier 5 is configured to be able to control the gain setting data from the system controller 11, which is a feature of the present invention, so as to have a predetermined gain.

Next, the converted digital signal is generated by a signal processing section 7 to generate image data for liquid crystal display such as a color difference signal and an illuminance signal to generate image data.
It is supplied to the liquid crystal display unit 9 via the A converter 8. Or later,
By repeating the display of the image data on the liquid crystal display unit 9 after the reading of the CCD data, the moving image can be observed in the finder mode.

In the measurement of the illuminance of the object, if the measurement is performed every time a vertical synchronization signal is generated, the processing becomes complicated. Therefore, the system controller 11 observes the output of the vertical synchronization signal (not shown) from the timing generator 10 and determines it in advance. The photometric element 14 is driven each time the vertical synchronization signal is generated X times, and the illuminance of the object is measured.

Next, the amplification factor selection control in the system controller 11 will be described with reference to FIG. As described above, in the finder mode, the system controller 11 drives the photometric element 14 when the vertical synchronizing signal is generated X times. Here, this interval is a period (hereinafter, 10 Vd) for generating 10 vertical synchronization signals.
In the finder operation mode, the system controller 11 drives the photometric element 14 every 10 Vd to obtain a photometric evaluation value. A comparison process is performed between the photometric evaluation value obtained here and amplification factor values of preset brightness thresholds a to e. Note that a to e are specified so that a>b>c>d> e.

Here, a standard format of a normal video camera uses a television system, and an interlace system is used as a scanning system. In this method, a plurality of CCDs are arranged in the vertical and horizontal directions. First, odd lines are scanned in a first field, and even lines are scanned in a second field. One screen (one frame) is scanned in two fields. In order to output a one-frame image, two fields are required, and each field can output only half of the one-frame image. The standard exposure time of a conventional CCD video camera according to this method is 1/60 or 1/30 second according to the United States standard (EIA), and 1/50 or 1/25 second according to the European standard.

In FIG. 2, a time when the subject is in a dark state is a
At this time, the camera is adjusted so that the aperture system is at maximum release and the shutter speed is 1/60 second. Therefore, in a region where (evaluation value ≧ a), the amplifier 5
Is fixed at G0, and exposure control is performed by the aperture and shutter speed.

On the other hand, when (evaluation value <a), the aperture is open as described above, and it is not possible to obtain a good finder image unless the shutter speed is slower than 1/60 second. Can not. However, if the shutter speed is slower than 1/60 second, it will be impossible to output 60 images per second because the exposure time is 1/60 second or more. As a result, the frame rate of the image displayed on the liquid crystal is reduced. Therefore, in the present configuration, when (evaluation value <a), the aperture is released, the shutter speed is fixed at 1/60, and the amplification rate of the amplifier 5 is changed without lowering the frame rate. A good finder image can be obtained.

FIG. 2 shows the relationship between the evaluation value and the threshold value. According to the algorithm shown in FIG. 3, when (b ≦ evaluation value <a), the amplification factor of the amplifier 5 is set to G1, and when (c ≦ evaluation value <b), the amplification factor of the amplifier 5 is set to G2. , (D ≦ evaluation value <c), the amplification factor of the amplifier 5 is set to G3, (e ≦ evaluation value <d), the amplification factor of the amplifier 5 is set to G4, and (evaluation value <e). Time
The amplification factor of the amplifier 5 is set to G5.

After the output signal from the image sensor 3 is amplified by the amplifier 5 having the amplification factor set as described above, the A / A
The data is converted into digital data by the D converter 6 and supplied to the signal processing unit 7.

[0019]

As described above, according to the configuration of the present invention, in the finder mode operation, the brightness is determined based on the output signal from the light amount detecting means, and the aperture diameter is released.
And when the shutter speed becomes a long shutter, by controlling the signal amplification rate of the amplifier circuit that amplifies the image signal so that the shutter speed does not become the long shutter, without lowering the frame rate of the finder output, An image with appropriate brightness can be output to the finder.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a relationship between brightness and an amplification factor according to the present invention.

FIG. 3 is a schematic diagram showing an amplification factor selection processing flow of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Imaging lens 2 Aperture 3 Image sensor 4 Sample hold 5 Amplifier 6 A / D converter 7 Signal processing unit 8 D / A converter 9 Liquid crystal display unit (finder) 10 Timing generator 11 System controller 12 Recording unit 13 Work buffer 14 Photometry Element (light amount detection means) 15 Video amplifier

Claims (1)

[Claims] A system controller drives an aperture and a predetermined shutter speed as appropriate to take in an optical image of an appropriate exposure amount and captures the optical image based on information from a light amount detecting means for detecting the brightness of a subject. A digital camera that converts the image signal into an electric image signal using an element, amplifies the image signal by an amplifying unit, performs predetermined signal processing, and displays an image on a finder; However, when the aperture is released by the system controller and the shutter is driven at a predetermined shutter speed or less, the amplification factor of the amplification unit is controlled in accordance with information from the light detection unit. Digital camera featuring.