JP2003204474A - Digital still camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital still camera which is capable of focusing correctly on a certain subject even if EVF is used. <P>SOLUTION: A digital still camera is equipped with an imaging optical system which images a subject, an imaging device 5 which converts and optical image imaged by the imaging optical system into electrical signals, an imaging device drive means 8 which generates timing for driving the imaging device 5, an A/D converter 10 converting the output of the imaging device 5 into digital image data, a storage medium 14 which stores the digital image data converted by the A/D converter 10, and a control means 17 which controls the whole. A monitoring means 20 is provided for monitoring image signals imaged by the imaging device 5, and an imaging area change means is provided for changing an imaging area which is read out from the imaging device 5, corresponding to the resolution of the monitoring means 20. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital still camera for storing image information digitally in a storage medium. 2. Description of the Related Art In recent years, digital still cameras configured to store image information in a storage medium such as a memory card instead of printing an image on a film have been put to practical use. FIG. 3 is a block diagram showing a conventional configuration example of a digital still camera. An optical image of a subject (not shown) obtained through an optical imaging system including a photographing lens 1, a focus lens 2, an aperture (iris) 3, and the like is transmitted through an imaging lens 4 onto an image sensor, for example, a CCD 5. Is imaged.
The focus lens 2 and the aperture 3 are driven by a lens drive circuit 6 and an iris drive circuit 7 via actuators such as step motors, respectively. [0005] The CCD 5 photoelectrically converts the formed optical image into an electric signal (a charge amount corresponding to the amount of light; the same applies hereinafter), and outputs an analog image signal by a transfer pulse from the CCD drive circuit 8. This analog image signal is a CD
Noise is reduced by an S (correlated double sampling) circuit 9 and an AGC circuit (automatic gain control circuit) having the same configuration.
Amplified at 9. The output of the CDS / AGC circuit 9 is A / D
It enters the converter 10 and is converted into digital image data. The digital image data output from the A / D converter 10 enters a subsequent process circuit 11. The process circuit 11 performs luminance processing and color processing on the input digital image data, and converts the digital image data into a digital video signal (for example, a luminance signal and a color difference signal). At the time of storage in a storage medium, the digital video signal enters a compression / expansion circuit 12 and the compression / expansion circuit 1
In step 2, data compression is performed. The compressed digital video signal enters the recording circuit 13. The recording circuit 13
A storage medium such as a RAM, for example, a memory card 1
4 stores a digital video signal, and the digital video signal is recorded. When reproducing an image signal, the compressed digital video signal stored in the memory card 14 is read out and returned to the compression / expansion circuit 12 via the recording circuit 13. The compression / expansion circuit 12 performs an expansion process for restoring the input compressed digital video signal. After that, the restored digital video signal is converted into an analog signal by the D / A converter 15. The video signal returned to the original analog image signal by the D / A converter 15 is output to the outside via the output circuit 16 as an NTSC video signal. The CPU 17 controls the operation of the entire circuit. A video signal is output simultaneously with turning on the power, and the output is output to an EVF (Electronic View Finder).
A digital still camera has also been developed in which the image is stored in the memory card 14 when the focus is adjusted and the release is released while watching. FIG. 4 is a block diagram showing a main part of another conventional configuration example of a digital still camera. The same components as those in FIG. 3 are denoted by the same reference numerals. In the conventional example shown in the figure, an imaging optical system, a CDS / AGC circuit 9, an A / D converter 10,
The configuration such as the process circuit 11 and the output circuit 16 is the same as the conventional example of FIG. However, in this example, the subject image being captured is viewed at a video rate (1/60 sec).
F20 is provided. The focus adjustment is performed while the subject image is monitored by the EVF 20, and the release switch is turned on. In this type of digital still camera, AE (automatic exposure) / AF (autofocus) control using a video signal is performed. For this reason, when the release switch S1 is on (the release button is half-pressed), the AE signal and the AF signal are output from the output circuit 16, and the CPU 17 controls the aperture shutter speed and the focus based on these signals. Also, the compression / expansion circuit 1
It is also conceivable to obtain an AF signal using DCT (discrete cos transform) in the second section. In a conventional digital still camera of this type, after converting an image signal photoelectrically converted by a CCD into digital image data, a luminance signal and a color difference signal are calculated based on the digital image data. After subjecting the color difference signal to predetermined image processing, video signal data is output (for example, see Patent Document 1). Further, the level of the luminance signal before gamma correction is compared with a predetermined threshold, and a suppression gain according to the comparison result and a gamma-corrected R
There is one that obtains an output RGB signal by multiplying the signal by a GB signal (for example, see Patent Document 2). [Patent Document 1] Japanese Patent Application Laid-Open No. H5-211653 (2nd
[Patent Document 2] Japanese Patent Application Laid-Open No. 5-244623 (3rd page)
(Page, page 4, FIG. 1) In a digital still camera that focuses on an EVF, it is difficult to find a correct focus position when the resolution of the EVF is low. . When the resolution of the EVF is low, a sum of data of a plurality of pixels of the CCD 5 becomes one pixel of the EVF as shown in FIG. Therefore, even if the image is focused, the fine pattern disappears on the EVF side, resulting in a blurred image. The present invention has been made in view of such a problem, and an object of the present invention is to provide a digital still camera capable of correctly focusing even when using an EVF. According to the present invention, there is provided an image pickup optical system for picking up an image of a subject, an image pickup device for converting a light image from the image pickup optical system into an electric signal, and Imaging device driving means for generating a timing for driving the imaging device; an A / D converter for converting an output of the imaging device into digital image data; and storing the digital image data converted by the A / D converter. In a digital still camera including a storage medium and control means for controlling the entire operation, a monitor means for monitoring an image signal picked up by the image pickup element is provided, and an image pickup area read out from the image pickup element according to the resolution of the monitor means Characterized in that an imaging area changing means for changing the image quality is provided. According to this structure, the image pickup area read from the image pickup device is changed according to the resolution of the monitor means. Therefore, even when EVF is used,
Focus can be adjusted correctly. Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. 3 and 4 are denoted by the same reference numerals. In the figure, a memory 18 stores digital image data output from the A / D converter 10. The memory 18 is also connected to the process circuit 11 so that the process circuit 11 can read and process the image data stored in the memory 18 as needed. The image of the subject formed on the CCD 5 through the imaging optical system (photographing lens 1, focus lens 2, aperture 3, imaging lens 4) is photoelectrically converted into an electric signal.
Then, the transfer pulse from the CCD drive circuit 8 is output as an analog image signal. The output analog image signal is reduced in noise by a CDS (correlated double sampling) circuit 9 and further amplified by an AGC circuit (automatic gain control circuit) 9 having the same configuration. CDS / AGC circuit 9
Is input to the A / D converter 10 and is converted into digital image data (digital image signal). The digital image data output from the A / D converter 10 enters a process circuit 11 and a memory 18. As the memory 18, for example, a field memory or a frame memory is used. The process circuit 11 performs various types of image processing, converts a digital image signal into a digital video signal, and outputs the digital video signal. The output of the process circuit 11 is converted into an analog signal by the D / A converter 15,
The video signal is output via the output circuit 16. At the same time, the output of the output circuit 16 is also input to the EVF 20 so that the captured image is displayed. The memory 18 stores one or more images. The CPU 17 controls the components of each circuit. In this embodiment, the CDS / AGC circuit 9 is used at the subsequent stage of the output of the CCD 5, but the configuration may be replaced with another circuit or may be omitted. The operation of the device configured as described above will be described below. In a digital still camera that focuses on the EVF 20, when the resolution of the EVF 20 is low, it is difficult to find a correct focus position. EVF2
When the resolution of 0 is low, the sum of data of a plurality of pixels of the CCD 5 becomes one pixel of the EVF 20 as shown in FIG. Therefore, even if the image is focused on the imaging side, the fine pattern disappears on the EVF 20 side, resulting in a blurred image. In order to solve this problem, signals corresponding to the number of pixels corresponding to the resolution of the EVF 20 may be extracted.
FIG. 2B shows a state in which signals corresponding to the number of pixels corresponding to the resolution of the EVF 20 are extracted from the CCD 5. In other words, a part of the area of the CCD 5 is taken out as it is and the EV
This is the input image of F20. In this way, the fine pattern on the CCD side can be reproduced on the EVF 20 side. FIG. 1 shows the hardware configuration at this time.
The case of using the configuration described above will be described. With such a configuration, the timing of driving the CCD is manipulated, and out of the CCD output signals, the signal of the pixel of only the area to be focused is taken out according to the size of the EVF 20, and the EVF 20 is output.
Can be realized by inputting it into As for the read timing of the CCD 5, an unnecessary area may be transferred at a high speed, and a necessary area may be extracted in accordance with the drive timing of the EVF 20. Accordingly, the resolution of the video signal output to the EVF 20 becomes the same as the resolution obtained by the imaging system. In this case, of the image signals fetched into the memory 18, only the area necessary for focus detection is read from the memory 18 and passed through the process circuit 11 and the like to the EVF2.
Enter 0. This configuration may be used when the EVF 20 can be driven only at the same timing as the drive timing of the CCD 5 or when driven at the same timing. If the drive timing of the EVF 20 is configured to be controllable, the control on the CCD 5 side is not performed and the EV 5 is controlled.
If all controls are performed on the F20 side, the configuration becomes simpler. Of course, there is no problem if control of CCD driving, memory driving, and EVF 20 driving are combined or used at the same time. Here, with such a configuration, the size (area) of the image actually captured and the image viewed by the EVF 20
Will change. Therefore, this configuration can be selected at the time of performing the focus adjustment, and the EVF 20 normally displays the entire area imaged by the CCD. As described above in detail, according to the present invention, it is possible to provide a digital still camera capable of correctly focusing even when using an EVF.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is an explanatory diagram of an EVF resolution. FIG. 3 is a block diagram showing a conventional configuration example of a digital still camera. FIG. 4 is a block diagram showing a main part of another conventional configuration example of a digital still camera. [Description of Signs] 1 photographing lens 2 focus lens 3 aperture (iris) 4 imaging lens 5 CCD 6 lens drive circuit 7 iris drive circuit 8 CCD drive circuit 9 CDS / AGC circuit 10 A / D converter 14 memory circuit 15 D / A converter 16 output circuit 17 CPU 18 memory 20 EVF

Continuation of front page    (72) Inventor Masaaki Tsuchida             2970 Ishikawacho, Hachioji-shi, Tokyo Konica shares             In the formula company (72) Inventor Shuji Hayashi             2970 Ishikawacho, Hachioji-shi, Tokyo Konica shares             In the formula company (72) Inventor Katsuya Nagaishi             2970 Ishikawacho, Hachioji-shi, Tokyo Konica shares             In the formula company (72) Inventor Kazuo Shiozawa             2970 Ishikawacho, Hachioji-shi, Tokyo Konica shares             In the formula company (72) Inventor Tadaaki Yoneda             2970 Ishikawacho, Hachioji-shi, Tokyo Konica shares             In the formula company (72) Inventor Jun Takayama             2970 Ishikawacho, Hachioji-shi, Tokyo Konica shares             In the formula company F term (reference) 5C022 AA13 AB21 AC03 AC12 AC42                       AC69

Claims (1)

Claims: 1. An imaging optical system for imaging a subject, an imaging device for converting a light image from the imaging optical system into an electric signal, and an imaging device for generating timing for driving the imaging device Driving means, an A / D converter for converting the output of the image sensor into digital image data, a storage medium for storing the digital image data converted by the A / D converter, and control for controlling the overall operation A digital still camera comprising: means for monitoring an image signal picked up by the image sensor; and an image area changing means for changing an image area read from the image sensor according to the resolution of the monitor means. A digital still camera characterized by the following.