WO2002063871A1

WO2002063871A1 - Digital camera

Info

Publication number: WO2002063871A1
Application number: PCT/JP2002/000904
Authority: WO
Inventors: Seishin Okazaki
Original assignee: Sanyo Electric Co., Ltd.
Priority date: 2001-02-06
Filing date: 2002-02-04
Publication date: 2002-08-15
Also published as: TW548994B; JP2002232766A

Abstract

A digital camera includes a CCD imager (14). A raw image signal of an object picked up by the CCD imager (14) is temporarily stored in an SDRAM (26). The raw image signal stored in the SDRAM (26) is repeatedly read out by a memory control circuit (24). A signal processing circuit (28) performs a signal processing of each of the raw image signals which have been read out and creates a plurality of YUV signals of high resolution. During the signal processing, a white balance adjustment is performed. The gain for the white balance adjustment differs from one raw image signal to another. For this, the high-resolution YUV signals have different image qualities from one another. A JPEG codec (34) compresses each of the plurality of high-resolution YUV signals so as to create a plurality of compressed image signals. A CPU (40) records the created compressed image signals in a recording medium (36).

Description

Digital camera technical field

The present invention relates to a digital camera, and more particularly to, for example, a digital camera that performs signal processing on a captured image signal to generate a recording image signal. Conventional technology

In a digital camera, a subject is photographed by an image sensor, and the photographed image signal is subjected to signal processing such as white balance adjustment, color correction, YUV conversion, and contour correction, thereby generating a recording image signal. The image quality of the recording image signal changes depending on the parameter values used for signal processing, but the desired image quality depends on the nature of the subject and the preference of the operator. I can't decide. For this reason, conventionally, the same subject is photographed a plurality of times, and each photographed signal is subjected to signal processing according to different parameter values. However, in such a conventional technique, it is necessary to photograph a subject a plurality of times, and thus there is a problem that each recorded image is shifted due to camera shake. The problem of camera shake becomes more pronounced as the zoom magnification is increased. Summary of the Invention

Therefore, a main object of the present invention is to provide a novel digital camera.

Another object of the present invention is to provide a digital camera capable of obtaining a plurality of recorded images of the same subject with different image qualities and preventing each recorded image from being shifted due to camera shake. It is.

A digital camera according to the present invention includes: an image sensor for photographing a subject; a memory for storing a photographed image signal corresponding to the subject; reading means for repeatedly reading the photographed image signal from the memory; Signal processing for performing signal processing according to mutually different parameter values on each captured image signal Recording means for recording a plurality of recording image signals generated by the signal processing means on a recording medium.

When a subject is photographed by the image sensor, a photographed image signal corresponding to the photographed subject is stored in the memory. The captured image signal stored in the memory is repeatedly read by the reading means. The signal processing means performs signal processing according to mutually different parameter values on each of the read captured image signals, and the recording means stores a plurality of recording image signals generated by the signal processing means on a recording medium. Record. Since signal processing according to mutually different parameter values is performed, a plurality of recorded images having different image qualities can be obtained for the same subject. Further, since the photographed image signal is stored in the memory and the same photographed image signal is repeatedly read out from the memory card, it is possible to prevent each recorded image from being shifted due to camera shake. When the signal processing means performs white balance adjustment on the captured image signal, the parameter value is an adjustment value of white balance adjustment. At this time, the optimum adjustment value of the white balance adjustment may be calculated by the calculating means, and the adjustment value may be changed by the adjustment value changing means based on the calculated optimum adjustment value. Here, if the adjustment value is changed along the color temperature curve, good image quality can be obtained for any of the recorded images.

More preferably, the zoom magnification of the subject to be photographed is controlled by the control means. At this time, the position of the optical axis method of the zoom lens may be controlled by the control means.

The above objects, 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. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram showing a configuration of one embodiment of the present invention;

FIG. 2 is an illustrative view showing a complementary color filter;

FIG. 3 is a block diagram showing a mating state of the SDRAM;

Figure 4 is a block diagram showing the configuration of the signal processing circuit;

FIG. 5 is an illustrative view showing a plane having a U signal as a horizontal axis and a V axis as a vertical axis, and a color temperature curve existing on this plane; and FIG. 6 is a flow chart showing a part of the operation of the FIG. 1 embodiment; and FIG. 7 is a flow chart showing another part of the operation of the FIG. 1 embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, a digital camera 10 of this embodiment includes a zoom lens 12a and a focus lens 12b, and an optical image of a subject is passed through these lenses 12a and 12b to form a progressive scan CCD imager. Irradiated at 14. A complementary color filter 14a as shown in FIG. 2 is mounted on the light receiving surface of the CCD imager 14, and the amount of charge generated in each pixel reflects the light intensity of the Ye, Cy, G or Mg color.

When the power is turned on, the system controller 40 provides a corresponding status signal to the CPU 40. Then, the CPU 40 activates a signal processing block including the TG 18 and the signal processing circuit 28 and an encoder block including the video encoder 30 and the monitor 32. The TG 18 drives the CCD imager 14 by a thinning-out reading method. As a result, a low-resolution raw image signal (charge) corresponding to the subject image is read from the CCD imager 14 at a predetermined frame rate. The read raw image signal of each frame is supplied to the memory control circuit 24 through the CDSZAGC circuit 20 and the A / D converter 22, and is written to the SDRAM 26 by the memory control circuit 24. A raw image area 26a is formed in the SDRAM 26 as shown in FIG. 3, and a raw image signal of each frame is written in the raw image area 26a.

The signal processing circuit 28 reads the raw image signal stored in the raw image area 26a for each frame through the memory control circuit 24, and converts the read raw image signal into RGB conversion, color separation, white balance adjustment, and key adjustment. Performs a series of processing of correction, YUV conversion, and contour correction. The YUV signal of each frame subjected to the contour correction is written into the display YUV area 26b shown in FIG. 3 by the memory control circuit 24.

On the other hand, the video encoder 30 reads the series of YUV signals written in the display YUV area 26b through the memory control circuit 24, and converts the read YUV signals into a composite image signal. The converted composite image The signal is provided to the monitor 32, whereby a real-time moving image (through image) of the subject is displayed on the screen.

When the operator operates the zoom key 46 while the through image is displayed, a corresponding state signal is given from the system controller 42 to the CPU 40. The CPU 40 drives the zoom lens 12a through the driver 16a, whereby the zoom lens 12a moves in the optical axis direction. When the zoom lens 12a moves to the telephoto side, a telephoto image is displayed on the monitor 32. When the zoom lens 12a moves to the wide side, a wide-angle image is displayed on the monitor 32.

The signal processing circuit 28 is specifically configured as shown in FIG. Since the CCD imager 14 is equipped with the complementary color filter 14a shown in FIG. 2, each pixel of the raw image signal output from the AZD converter 22 is one of Ye, Cy, G, and Mg. This is a signal having one color component. The RGB conversion circuit 28a performs such RGB conversion on the raw image signal to generate an RGB signal in which each pixel has one of R, G, and B color components. In the subsequent color separation circuit 22a, the RGB signal output from the RGB conversion circuit 28b is subjected to color separation, whereby each pixel generates an R GB signal having all the R, G and B color components. Generated.

Among the generated RGB signals, the R signal is supplied to an amplifier correction circuit 28e via an amplifier 28c, the G signal is directly supplied to an amplifier correction circuit 22e, and the B signal is supplied to an amplifier correction circuit 28d via an amplifier 28d. Circuit 28e. In the amplifier 28c, the gain is added to the R signal, and in the amplifier 28b, the gain] 3 is added to the B signal, whereby the white balance is adjusted. The key correction circuit 28e performs key correction on the RGB signal that has been subjected to the white balance adjustment, and supplies the corrected RGB signal to the YUV conversion circuit 28f.

The RGB signal is converted into a YUV signal at a ratio of 4: 2: 2 in the {11} conversion circuit 28f. Among the converted YUV signals, the U signal and the V signal are output as they are, and the Y signal is output through the contour correction in the contour correction circuit 28g.

The Y signal output from the contour correction circuit 28g and the U signal and V signal output from the YUV conversion circuit 28f are also supplied to a thinning circuit 28h. The thinning circuit 28h is activated when a high-resolution raw image signal is output from the CCD imager 14, and performs thinning processing on the high-resolution YUV signal. This allows the monitor A low-resolution YUV signal is generated for display on 32.

The RGB signal output from the color separation circuit 22a is also input to a color evaluation circuit 38 shown in FIG. The color evaluation circuit 38 integrates each of the R signal, the G signal, and the B signal for each frame period to obtain color evaluation values Ir, Ig, and lb. The CPU 40 fetches the color evaluation values Ir, Ig, and Ib obtained for each frame from the color evaluation circuit 38, and based on the color evaluation values Ir, Ig, and Ib, the amplifier 28c and the amplifier 28c. And the gain α and) 3 set to 28 d. This adjusts the white balance of the RGB signal.

When the bracket photographing mode is selected by the mode switching switch 48 and the shutter button 44 is pressed, a corresponding state signal is given from the system controller 42 to the CPU 40. The CPU 40 first performs exposure adjustment and focus adjustment. The desired aperture amount and the desired exposure time are set in the aperture unit (not shown) and the TG 18 by the exposure adjustment, and the position of the focus lens 12b in the optical axis direction is adjusted by the focus adjustment. The focus lens 12b is driven by a dryino 16b.

When the exposure adjustment and the focus adjustment are completed, the main exposure and all-pixel reading are performed by the TG 18, and a high-resolution raw image signal is output from the CCD imager 14. The read raw image signal passes through a CDSZAGC circuit 20 and an AZD converter 22, and is then written by a memory control circuit 24 into a raw image area 26a shown in FIG. The signal processing circuit 28 reads a raw image signal from the raw image area 26a through the memory control circuit 24, and performs the above-described signal processing on the read raw image signal. The RGB signal generated in the course of the series of signal processing is provided to a color evaluation circuit 38, which calculates color evaluation values Ir, Ig and lb based on the supplied RGB signal. The CPU 40 calculates the optimum gains as and 13 s based on the calculated color evaluation values Ir, Ig and Ib, and compares the obtained optimum gains s and β s with the amplifiers 28 c and 28 shown in FIG. Set to d.

The memory control circuit 24 repeatedly reads a high-resolution raw image signal from the raw image area 26a in response to a request from the signal processing circuit 28. On the other hand, the CPU 40 compresses the JPEG codec 34 every time the raw image signal of one frame is subjected to signal processing. Command the compression processing, and change the gains α and 3 to be set for the amplifiers 28 c and 28 d based on the optimum gains as and / 3 s. The gains a and j8 are specifically changed along the color temperature curve shown in FIG. The signal processing circuit 28 generates high-resolution YUV signals of a plurality of frames having different image qualities, and each high-resolution YUV signal is written to the recording YUV area 26c shown in FIG.

The JPEG codec 34 reads the YUV signal of each frame from the recording YUV area 26c through the memory control circuit 24, and performs JPEG compression on the read YUV signal. The compressed YUV signal (compressed image signal) is stored in the compressed image area 26 d shown in FIG. When the compressed image signals of a plurality of frames are accumulated in the compressed image area 26d, the CPU 40 reads these compressed image signals through the memory control circuit 24, and the read compressed image signals are stored in the removable recording medium 3. Record in 6. When all the compressed image signals have been recorded on the recording medium 36, the bracket shooting is completed.

The thinning circuit 28h shown in FIG. 4 is activated during bracket shooting, and a low-resolution YUV signal having a different image quality is output from the thinning circuit 28h for each frame. The low-resolution YUV signal of each frame is written to the display YUV area 26 b shown in FIG. 4, and then read out by the video encoder 30. As a result, the image quality of the still image (freeze image) displayed on the monitor 32 changes every frame period.

The CPU 40 operates according to the flowcharts shown in FIGS. 6 and 7 when the shirt button 45 is pressed in the state where the bracket shooting mode is selected. The program corresponding to this flowchart is stored in the ROM 50.

First, in step S1, the count value N of the counter 40a is set to "0", and exposure adjustment (AE processing) and focus adjustment (AF processing) are performed in steps S3 and S5. When the optimal aperture and the optimal exposure time are set to the aperture unit and TG 18 by the AE processing, and the focus lens 12 b is set to the in-focus position by the AF processing, the main exposure is performed by the TG 1 in step S7. Command 8 The TG 18 performs the main exposure for the set optimal exposure time, and reads out the raw image signal generated by the main exposure from the CCD imager 14 by the all-pixel readout method. Read high The raw image signal having the resolution is written to a raw image area 26 a shown in FIG. 3 through a CDSZAGC circuit 20, an AZD converter 22 and a memory control circuit 24, and then read out by a signal processing circuit 28.

In step SI1, the count value N is determined. If N = 0, the process proceeds to step S13 after waiting for a predetermined time in step S11, and fetches the color evaluation values Ir, Ig and Ib from the color evaluation circuit 38. The raw image signal based on the main exposure is read from the SDRAM 26 by the memory control circuit 24, and subjected to RGB conversion and color separation by the RGB conversion circuit 28a and the color separation circuit 28b shown in FIG. The color-separated RGB signals are integrated by the color evaluation circuit 38 over one frame period. However, since it takes time from the start of the main exposure to the completion of the integration processing, the process waits in step S11 for this time. As a result, the color evaluation values I · r, Ig, and lb captured in step S13 are evaluation values based on the raw image signal obtained by the main exposure. In step S15, the optimum gains s and | 8 s are calculated based on the taken color evaluation values Ir, Ig and Ib.

On the other hand, when N> 0, the process proceeds to step S17, and the gains a and 3 are changed based on the optimum gains s and) Ss. Referring to FIG. 5, when N = l, the optimal gain s and) 3 s are multiplied by “0, 9” and “1.1”, and when N = 2, the optimal gain s and iS s Is multiplied by "0.8" and "1.2", and when N = 3, the optimal gains << s and s are multiplied by "1.1" and "0.9", and N = 4 In case of, multiply the optimal gain s and) 3 s by "1.2" and "0.9". As a result, the gains _α and) 3 are changed along the color temperature curve. In step S19, the optimum gains s and; 8s calculated in step S15 and the gain α changed in step S17) are set to the amplifiers 28c and 28d shown in FIG. When is completed, the process waits for a predetermined time in step S21. During the predetermined time, the raw image signal read from the raw image area 26a after the gain setting is subjected to signal processing by the signal processing circuit 28, and the high-resolution YUV signal and the low-resolution YUV output from the signal processing circuit 28 This corresponds to the time until the signal is written to the recording YUV area 26c and the display YUV area 26b shown in FIG. When the predetermined time has elapsed, the gain set in step S19 A high-resolution YUV signal and a low-resolution YUV signal having an image quality according to a (as) and i3 (3 s) are secured in the SDRAM 26, and a freeze image based on the low-resolution YUV signal is displayed on the monitor 32.

In step S23, the JPEG codec 34 is instructed to perform JPEG compression. The JPEG codec 34 reads the high-resolution YUV signal from the recording YUV area 26, applies JPEG compression to the read high-resolution YUV signal, and converts the compressed image signal into a compressed image area 26d shown in FIG. Write. In step S25, the power counter 40a is incremented, and in the following step S27, the count value N is compared with the maximum value Nmax (= 5). Here, if N <Nmax, the processing of steps S17 to S25 is repeated until N = Nmax.

In step S17, the gains a; and 3) corresponding to the count value N are set in the amplifiers 28c and 28d, and the signal processing circuit 28 generates a high-resolution YUV signal and a low-resolution YUV signal having different image qualities. As a result, the image quality of the freeze image displayed on the monitor 32 changes for each frame, and compressed image signals having different image qualities are accumulated in the compressed image area 26d for each frame period.

When N = Nmax, the process proceeds from step S27 to step S29 to perform a recording process. Specifically, the compressed image signal stored in the compressed image area 26 d is read, and each read compressed image signal is recorded on the recording medium 36. When the recording of the compressed image signal for 5 frames is completed, the routine returns to the upper layer routine. An image file is created for each compressed image signal in the recording medium 36, and an identification number is assigned to each image file in the order of increasing (or decreasing) color temperature.

According to this embodiment, when a subject is photographed by the CCD imager 14, a raw image signal (photographed image signal) of the subject is stored in the SDRAM 26. The raw image signal stored in the SD RAM 26 is repeatedly read by the memory control circuit 24. The signal processing circuit 28 performs signal processing on each of the read raw image signals to generate a plurality of high-resolution YUV signals. In the process of signal processing, white balance adjustment is performed. The gains α and 3 for white balance adjustment differ for each raw image signal. As a result, each generated high resolution YUV signal has a different image quality. The JPEG codec 34 converts the generated high-resolution YUV signal The compressed image signals are separately compressed to generate a plurality of compressed image signals, and the CPU 40 records each of the generated compressed image signals on the recording medium 36.

As described above, since each raw image signal is subjected to signal processing according to different parameter values, a plurality of recorded images having different image qualities can be obtained for the same subject. In addition, since the raw image signal is temporarily stored in the SDRAM 26 and the same raw image signal is repeatedly read from the SDRAM 26, it is possible to prevent a shift in each recorded image due to camera shake. Note that the problem of camera shake becomes more pronounced when a telephoto image is taken with the zoom lens 12a placed on the telephoto side. However, in this embodiment, only one shooting is required, so the position of the zoom lens 12a The problem of camera shake can be solved regardless of.

In the above-described embodiment, a progressive scan type CCD imager is used. However, an in-line race scan type CCD imager may be used instead. Further, a CMOS image sensor may be used instead of the CCD image sensor.

Further, in this embodiment, the complementary color filter is mounted on the light receiving surface of the CCD imager, but a primary color filter may be mounted instead. In this case, the RGB conversion circuit becomes unnecessary.

Further, in this embodiment, the optical zoom is performed by the zoom lens in order to obtain a telephoto image or a wide-angle image. However, a digital zoom may be performed instead of or in addition to the optical zoom.

Further, in this embodiment, the white balance adjustment value (gain or | 8) is changed in order to generate image signals having mutually different image qualities. The saturation can be adjusted by the YUV conversion circuit. For this reason, instead of the white balance adjustment value or together with the white balance adjustment value, at least one of the key correction value, the contour correction value, and the saturation may be changed.

While this invention has been described and illustrated in detail, it is obvious that it is used by way of illustration and example only and should not be construed as limiting, the spirit and scope of the invention being attached to Limited only by the language of the claim.

Claims

The scope of the claims

1. A digital camera with the following:

An image sensor for photographing the subject;

A memory for storing a captured image signal corresponding to the subject;

Reading means for repeatedly reading the photographed image signal from the memory;

Signal processing means for performing signal processing according to mutually different parameter values on each captured image signal read by the reading means;

Recording means for recording a plurality of recording image signals generated by the signal processing means on a recording medium;

2. A digital camera dependent on claim 1,

The signal processing means performs white balance adjustment on the captured image signal,

The parameter value is an adjustment value of the white balance adjustment,

Calculating means for calculating an optimal adjustment value for the white balance adjustment; and

The apparatus further includes an adjustment value changing unit that changes the adjustment value based on the optimum adjustment value.

3. A digital camera dependent on claim 2,

The adjustment value changing means changes the adjustment value along a color temperature curve.

4. A digital camera subject to claim 1,

The image processing apparatus further includes control means for controlling a zoom magnification of the subject.

5. A digital camera subject to claim 4, wherein

A zoom lens that irradiates an optical image of the subject on a light receiving surface of the image sensor;

The control means controls the position of the zoom lens in the optical axis direction.