JP4017419B2 - Digital camera - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital camera, and more particularly to a digital camera that records, for example, an image signal of a subject photographed through a focus lens.
[0002]
[Prior art]
Many recent digital cameras have an autofocus function. According to this autofocus function, when the focus adjustment area (generally near the center of the screen (all shooting areas)) is aligned with the subject and the shutter button is pressed halfway, that is, when halfway pressed, the subject is automatically focused. Fit. When the shutter button is further pressed, that is, when the shutter button is fully pressed, shooting is performed. Therefore, even a person unfamiliar with the camera operation can shoot in focus with relative ease.
[0003]
[Problems to be solved by the invention]
However, even with an autofocus function, it is difficult to capture a fast-moving subject with accurate focus. Also, it is not easy to shoot such a subject with a favorite composition (for example, in the center of the screen). In particular, when the subject moves around at random, such as a child who runs around, this tendency becomes prominent, and there is a problem in that a chance to take a photo opportunity at a corner may be missed.
[0004]
Therefore, a main object of the present invention is to provide a digital camera capable of accurately capturing a photo opportunity.
[0005]
[Means for Solving the Problems]
The digital camera according to the present invention is output from the photographing means for photographing the subject through the focus lens, the focus information creating means for creating the focus lens focusing information for the subject based on the image signal outputted from the photographing means , and the photographing means. position information generation means for generating position information of the subject in imaged region based on the image signal, a weighted addition on the position information created by a position information creating means and focusing information created by the focusing information creating means subjecting the adding means, and Ru with a recording means for performing recording processing on the image signal output from the imaging means based on a result of comparison between the obtained sum value and the threshold value by weighted addition of the adding means.
[0006]
[Action]
In the present invention, the image signal of the subject photographed through the focus lens is output from the photographing means. Based on this image signal, the focus information creating means creates focus information, and the position information creating means creates position information. The adding means weights and adds the focus information created by the focus information creating means and the position information created by the position information creating means. The recording means performs a recording process on the image signal output from the photographing means based on the comparison result between the addition value obtained by the weighted addition of the adding means and the threshold value.
[0008]
Weighted with further may be provided with a ratio changing means for arbitrarily changing the ratio of the weight for each of the focus information and the position information in addition. In this way, it is possible to arbitrarily set how much emphasis is placed on each of the degree of focusing and the position of the subject when performing shooting.
[0009]
Moreover, you may further provide the threshold value change means for changing a threshold value arbitrarily. That is, the threshold value that serves as a criterion for determining whether or not to perform shooting may be arbitrarily set.
[0010]
【The invention's effect】
According to the present invention, since photographing is performed based on the degree of focus lens focusing on the subject and the position of the subject in the photographing region, even a moving subject can be photographed with an accurate focus and a favorite composition. That is, the photo opportunity can be accurately captured.
[0011]
The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.
[0012]
【Example】
Referring to FIG. 1, a digital camera 10 of this embodiment has a built-in CCD (Charge Coupled Device) type solid-state imaging device (hereinafter simply referred to as a CCD) 14 into which an optical image of a subject is incident through a focus lens 12. is doing. The CCD 14 exposes an optical image of a subject in accordance with a timing signal supplied from a timing generator (hereinafter referred to as TG) 16 and outputs charges accumulated by the exposure as an image signal.
[0013]
That is, when a power switch (not shown) is turned on, the CPU 18 enters the photographing mode in response to this. In this shooting mode, the CPU 18 instructs the TG 16 to repeat pre-exposure and thinning-out reading. In response to this command, the TG 16 executes the pre-exposure in synchronization with the vertical synchronization signal generated by itself, and outputs the part of the charge accumulated by the pre-exposure in the next frame period. Is supplied to the CCD 14. As a result, a low resolution image signal is output from the CCD 14 for each frame. The output image signal of each frame is input to a CDS (Correlated Double Sampling) / AGC (Automatic Gain Control) circuit 20.
[0014]
The CSD / AGC circuit 20 sequentially performs correlated double sampling processing and amplification processing on the input image signal. Then, the processed image signal is input to the A / D converter 22. The A / D converter 22 converts the input image signal into image data that is a digital signal, and inputs the converted image data to the signal processing circuit 24. Note that the operations of the CSD / AGC circuit 20 and the A / D converter 22 are also controlled by timing signals different from those described above provided from the TG 16.
[0015]
The signal processing circuit 24 performs a series of processes such as color separation, white balance adjustment, gamma correction, and YUV conversion on the input image data, and inputs the generated YUV data to the video encoder 26. The video encoder 26 converts the input YUV data into an NTSC composite image signal and inputs the composite image signal to the liquid crystal monitor 28. As a result, a real-time moving image (through image) of the subject is displayed on the screen of the liquid crystal monitor 28.
[0016]
In this state, when the shutter button 30 is pressed, the CPU 18 enters a photographing process, and performs focus adjustment and exposure adjustment as the beginning. That is, the CPU 18 first instructs the TG 16 to repeat pre-exposure and all-pixel reading. In response to this command, the TG 16 performs pre-exposure in synchronization with the vertical synchronization signal and supplies a timing signal to the CCD 14 so that all charges accumulated by the pre-exposure are output in the next frame. As a result, a high-resolution image signal is output from the CCD 14 for each frame, and the image signal of each frame is sent to the signal processing circuit 24 via the CDS / AGC circuit 20 and the A / D converter 22 as described above. Entered.
[0017]
The signal processing circuit 20 performs the above-described color separation, white balance adjustment, and YUV conversion on the input image data to generate YUV data. Then, Y (luminance) data forming the YUV data is input to the luminance evaluation circuit 32 and the focus evaluation circuit 34. The luminance evaluation circuit 32 calculates a luminance evaluation value representing the degree of luminance of the subject image by integrating the input Y data for each frame. On the other hand, the focus evaluation circuit 34 calculates a focus evaluation value representing the degree of focus of the focus lens 12 with respect to the subject by integrating the high frequency component of the Y data for each frame (contrast detection method). The calculated luminance evaluation value and focus evaluation value are input to the CPU 18.
[0018]
The CPU 18 controls the focus driver 36 based on the focus evaluation value, and sets the focus lens 12 to the in-focus position. At the same time, the CPU 18 calculates the optimum exposure period based on the luminance evaluation value, and sets the optimum exposure period in the TG 16.
[0019]
After completing such focus adjustment and exposure adjustment, the CPU 18 proceeds to the main photographing operation. Specifically, the main exposure for one frame and the reading of all pixels are instructed to the TG 16 and the compression processing is instructed to the compression / decompression circuit 38. In response to a command from the CPU 18, the TG 16 executes main exposure according to the set optimum exposure period and supplies a timing signal to the CCD 14 so as to output all charges accumulated by the main exposure. As a result, a high-resolution image signal for one frame is output from the CCD 14, and this image signal is input to the signal processing circuit 24 via the CDS / AGC circuit 20 and the A / D converter 22. In the signal processing circuit 24, the above-described series of processing is executed, and YUV data generated thereby is input to the compression / decompression circuit 38. The compression / decompression circuit 38 compresses the input YUV data by a JPEG (Joint Photographic Expert Group) system in response to a compression processing command from the CPU 18. Then, the JPEG image file generated by this compression process is recorded on the memory card 40.
[0020]
The image (JPEG image file) recorded in the memory card 40 in this way can be reproduced in the reproduction mode. That is, when the playback mode is entered by operating the menu key 42, the CPU 18 instructs the compression / decompression circuit 38 to read and decompress the JPEG image file. In response to this command, the compression / decompression circuit 38 reads out the JPEG image file from the memory card 40 and decompresses the read JPEG image file back to the original YUV data. The YUV data is transferred to the video encoder 26 via the signal processing circuit 24, where it is converted into an NTSC composite image signal. The converted composite image signal is input to the liquid crystal monitor 28, whereby a reproduced image is displayed on the screen of the liquid crystal monitor 28.
[0021]
In the playback mode, playback images can be displayed one by one, or a plurality of playback images can be displayed in a multi display. In this manner, the display mode of the reproduced image can be selected by operating the menu key 42. However, since this is not directly related to the gist of the present invention, further detailed description is omitted here.
[0022]
By the way, the digital camera 10 of this embodiment has a moving object automatic photographing function suitable for photographing a fast-moving subject or a randomly moving subject. According to this moving object automatic photographing function, it is possible to photograph the moving subject with a composition in which the moving subject is accurately focused and placed near the center of the screen. In order to realize this, the digital camera 10 of this embodiment includes an imaging condition evaluation circuit 50 to which the Y data described above is input from the signal processing circuit 24. FIG. 2 shows a detailed configuration of the imaging condition evaluation circuit 50.
[0023]
As shown in FIG. 2, the imaging condition evaluation circuit 50 includes an object position evaluation circuit 52, a focus rate conversion circuit 54, and a ratio conversion circuit 56. Among these, the object position evaluation circuit 52 includes the above-described Y data. Is entered. The object position evaluation circuit 52 calculates a position evaluation value representing the position of the subject on the screen (imaging area) based on the input Y data. Here, the object position evaluation circuit 52 will be described in detail with reference to FIGS.
[0024]
Referring to FIG. 3, the object position evaluation circuit 52 includes a contour extraction circuit 70, a binarization circuit 72, a centroid detection circuit 74, and a position determination circuit 76. The Y data input to the object position evaluation circuit 52 is first subjected to contour extraction processing in the contour extraction circuit 70. Specifically, the contour extraction circuit 70 calculates the contour of the subject from the Y data based on a well-known inter-frame difference method (a method for obtaining the difference between the image data of the current frame and the image data of the previous frame). Extract. The contour data indicating the extracted contour is binarized by the binarization circuit 72, and the binary data is input to the centroid detection circuit 74. The center of gravity detection circuit 74 calculates the center of gravity G of the subject from the input binary data, and inputs the center of gravity data indicating the calculated center of gravity G to the position determination circuit 76.
[0025]
As shown in FIG. 4, the position determination circuit 76 divides the entire area of the screen into ten concentric rectangular areas 80, 80,. Numerical values from “1” to “10” are assigned to areas 80, 80,. Then, it is determined in which rectangular area 80 the center of gravity G of the subject (human in the figure) is located, and the numerical value assigned to the rectangular area 80 is output as the above-described position evaluation value. Therefore, the closer the subject (center of gravity G) is to the center O of the screen, the larger the numerical value of the position evaluation value. When there are a plurality of subjects, the average value of the numerical values assigned to the rectangular area 80 where each subject (center of gravity G) is located is used as the position evaluation value. This position evaluation value is input to the multiplication circuit 58 shown in FIG.
[0026]
On the other hand, the focus evaluation value is input from the focus evaluation circuit 34 to the focus rate conversion circuit 54. The focus rate conversion circuit 54 converts the input focus evaluation value into a numerical value from “1” to “10”, and inputs the converted evaluation value to a multiplication circuit 60 different from the above. The focus rate conversion circuit 54 outputs a larger focus evaluation value as the focus rate is higher.
[0027]
Weighting data is input from the CPU 18 to the ratio conversion circuit 56. The weighted data includes two numerical values α and β that are added to each other and become “1”. One of the numerical values α is input to the multiplication circuit 58 on the side where the position evaluation value is input, and the other numerical value β Is input to the multiplication circuit 60 on the side where the converted focus evaluation value is input. The numerical values α and β can be arbitrarily set by operating the menu key 42.
[0028]
The multiplication circuit 58 multiplies the position evaluation value and the numerical value α, and inputs the multiplication result to the addition circuit 62. Similarly, the other multiplication circuit 60 also multiplies the input focus evaluation value and the numerical value β, and inputs the multiplication result to the addition circuit 62. The adder circuit 62 adds the multiplication results input from the multiplication circuits 58 and 60 and inputs the addition result to the determination circuit 64.
[0029]
In addition to the addition result by the addition circuit 62, determination level data (threshold value data) is also input from the CPU 18 to the determination circuit 64. The determination circuit 64 compares these addition results with the threshold value indicated by the determination level data. Here, when the addition result is equal to or greater than the threshold value, the determination circuit 64 outputs determination data of F = 1. On the other hand, when the addition result is smaller than the threshold value, the determination circuit 64 outputs determination data F that F = 0. This determination data F is input to the CPU 18.
[0030]
When the determination data F input from the imaging condition evaluation circuit 50 is F = 1, the CPU 18 executes the actual imaging operation. That is, the main exposure for one frame and the reading of all pixels are commanded to the TG 16 and the compression processing is commanded to the compression / decompression circuit 38. As a result, a high-resolution image signal for one frame is output from the CCD 14, and this image signal is input to the signal processing circuit 24 via the CDS / AGC circuit 20 and the A / D converter 22 and converted into YUV data. Is done. The YUV data is compressed by the compression / decompression circuit 38, and the compressed JPEG image file is recorded in the memory card 40.
[0031]
Such a series of operations by the imaging condition evaluation circuit 50 and the operation of the CPU 18 when the determination data F output by the imaging condition evaluation circuit 50 is F = 1 are set in the moving body imaging mode by operating the menu key 42. This is executed for the first time when the shutter button 30 is fully pressed in the selected moving body shooting mode. That is, after the shutter button 30 is fully pressed in the moving body shooting mode, shooting is actually executed when the subject is caught near the center of the screen and the subject is in focus.
[0032]
It should be noted that, when performing shooting in the moving body shooting mode, which of the subject position and the degree of focus should be emphasized can be arbitrarily set by operating the weighting data described above with the menu key 42. In addition, the criteria for determining whether the shooting is executed when the subject position and the degree of focusing (strictly speaking, the result of weighted addition according to the above-described numerical values α and β) are reached are determined by the menu key. 42 can be arbitrarily set by operating the above-described determination level data.
[0033]
A specific operation of the CPU 18 in the moving body shooting mode will be described with reference to FIG. A control program for controlling the operation of the CPU 18 in accordance with each process shown in this flowchart is stored in a program memory 18a in the CPU 18.
[0034]
That is, the CPU 18 first determines in step S1 whether or not the moving body shooting mode has been canceled by operating the menu key 42. If it is determined that the moving body shooting mode has been canceled, the CPU 18 ends the series of processes shown in FIG. 5 and exits the moving body shooting mode (for example, shifts to the shooting mode or the playback mode). On the other hand, if the moving body shooting mode has not been canceled, the CPU 18 proceeds to the next step S3.
[0035]
In step S3, the CPU 18 determines whether or not the shutter button 30 has been fully pressed. When it is determined that the button has been fully pressed, the CPU 18 proceeds to step S5, and determines whether or not the determination data F input from the imaging condition evaluation circuit 50 is F = 1. If it is determined in step S3 that the shutter button 30 has not been fully pressed, the CPU 18 returns to step S1.
[0036]
When it is determined in step S5 that the determination data F is F = 1, the CPU 18 proceeds to step S7 and instructs the TG 16 to perform main exposure and all pixel readout. In step S9, the compression / decompression circuit 38 is instructed to perform compression processing, and the process returns to step S1.
[0037]
On the other hand, when the determination data F is not F = 1 in step S5, that is, when F = 0, the CPU 18 proceeds to step S11. In step S11, it is determined whether the moving body shooting mode has been canceled by operating the menu key 42. When it is determined that the moving body shooting mode has been canceled, the moving body shooting mode is exited. If the moving body shooting mode has not been canceled, the process returns to step S5.
[0038]
As can be seen from the above description, according to the digital camera 10 of this embodiment, when the moving body shooting mode is used, shooting is automatically executed according to the position of the subject and the degree of focusing. Therefore, for example, even when a child running around randomly is photographed as a subject, the subject can be photographed with a favorite composition (here, the composition where the subject is located near the center) and with an accurate focus. That is, the photo opportunity can be accurately captured. The effectiveness of the moving body shooting mode is particularly effective when the focal length of the focus lens 12 is long (that is, when the shooting area is narrow and it is difficult to capture a moving subject). In addition, when shooting in the moving body shooting mode, it is desirable to fix the digital camera 10 to a tripod.
[0039]
In this embodiment, the CCD 14 is used as means for converting the optical image of the subject into an image signal. However, other imaging elements or imaging tubes such as a CMOS (Complementary Metal Oxide Semiconductor) type may be used. Further, although the memory card 40 is used as a recording medium for recording photographed image data (JPEG image file), other recording media such as a magneto-optical disk may be used.
[0040]
In the contour extraction circuit 70 of FIG. 3, the inter-frame difference method is used to extract the contour of the subject, but other contour extraction methods such as a background difference method and an expansion / erosion processing method may be adopted. . In the position determination circuit 76, the screen is divided into ten rectangular areas 80, 80,... As shown in FIG. Further, the rectangular areas 80, 80,... Are formed concentrically with the center O of the screen as the center, but the rectangular areas 80, 80,. May be. Moreover, you may divide | segment into the area of shapes other than a rectangle.
[0041]
The imaging condition evaluation circuit 50 can be configured by a DSP (Digital Signal Processor). Further, the imaging condition evaluation circuit 50 (each circuit 52 to 64) can be configured by pure hardware. Further, the CPU 18 can realize the same function as the imaging condition evaluation circuit 50.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an embodiment of the present invention.
2 is a block diagram showing a detailed configuration of an imaging condition evaluation circuit in FIG. 1. FIG.
3 is a block diagram showing a detailed configuration of an object position evaluation circuit in FIG. 2. FIG.
4 is an illustrative view for explaining the operation of the position determination circuit in FIG. 3; FIG.
FIG. 5 is a flowchart showing the operation of the CPU in the embodiment of FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Digital camera 12 ... Focus lens 14 ... CCD type solid-state image sensor 18 ... CPU
34 ... Focus evaluation circuit 40 ... Memory card 50 ... Imaging condition evaluation circuit

Claims (3)

A photographing means for photographing a subject through a focus lens;
Focusing information creating means for creating focusing information of the focus lens with respect to the subject based on an image signal output from the photographing means;
Position information creating means for creating position information of the subject in the photographing region based on the image signal output from the photographing means;
Adding means for performing weighted addition on the focus information created by the focus information creating means and the position information created by the position information creating means; and
A digital camera comprising recording means for performing recording processing on an image signal output from the photographing means based on a comparison result between an addition value obtained by weighted addition of the adding means and a threshold value . Further comprising, claim 1 digital camera according to the ratio changing means for arbitrarily changing the ratio of the weight for each of the focus information and the position information in the weighted addition. Further comprising, according to claim 1 or 2 digital camera according to the threshold changing means for arbitrarily changing the threshold value.

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