JP2004274118A - Digital camera apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital camera apparatus for displaying a moving image without lowering a frame rate in a camera-through state. <P>SOLUTION: A digital camera apparatus 1 includes a camera 10 for continuously outputting image data at a fixed speed picture by picture as digital data, a capture P 11 for writing the image data captured from the camera 10 into a memory 15, an image conversion P 12 for converting a format of the image data, the memory 15 and an LCD 14 for reading and displaying the image data captured into the memory 15, does not include an optical finder and confirms an object to be photographed on the LCD 14 before photographing. In such a camera apparatus, the condition of the number of pixels in one picture of image data outputted from the camera at the fixed speed ≥ the number of pixels in an image display area of the LCD > the number of pixels in the image data to be displayed on the LCD is fulfilled and the condition of the number of pixels in the image data to be displayed on the LCD > the number of pixels in image data to be transferred between capture or image conversion and the memory is fulfilled. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a digital camera device for photographing a digital image, and more particularly to a digital camera and a mobile phone which are small, do not have an optical finder, and use a small liquid crystal display device as a finder.
[0002]
[Prior art]
Instead of silver halide photography, semiconductor imaging modules can be used to shoot a subject and electrically record the captured image information. Starting with analog video cameras, digital video recording and digital video recording can be used. A wide variety of products such as an electronic still camera that records a captured still image on a semiconductor device such as a memory card.
[0003]
Also, in recent years, a small camera module is built in a mobile phone, and an image is taken with the mobile phone, and if necessary, transmitted to another type of phone by e-mail or the like. More products are being sent.
[0004]
Specifically, a method in which a folding unit incorporating a detachable digital camera is attached to a mobile phone and a captured image can be displayed by a liquid crystal display device mounted on the mobile phone (for example, see Patent Document 1) ) And a foldable communication terminal device and an image display method capable of displaying an image captured by a camera by using a liquid crystal display device incorporating a camera in a mobile phone. 2).
[0005]
[Patent Document 1]
JP-A-2002-237880 (Page 3, FIG. 4)
[Patent Document 2]
JP-A-2002-300237 (page 5, FIG. 3)
[0006]
[Problems to be solved by the invention]
In the above-mentioned known examples and digital still cameras currently on the market, an image of a subject normally observed using a viewfinder, that is, an image for framing the subject when photographed by the camera, is displayed on a liquid crystal display device equipped with a moving image. It is displayed as an image. In a state where an object is observed on a liquid crystal display device before photographing (hereinafter, referred to as a camera through state), it takes time to perform signal processing for transferring a signal from a high-definition camera sensor to the liquid crystal display device for display. Currently, only a few frames per second of moving images can be displayed. Incidentally, a television signal of the NTSC standard displays 30 frames per second (accurately, an image with half the vertical resolution is displayed at 60 frames per second), and 24 frames per second in a movie.
[0007]
This poses a considerable obstacle to usability in actual shooting.Digital still cameras are usually equipped with an optical viewfinder separately from the liquid crystal display device, and use this to observe and shoot the subject while shooting. It has become.
[0008]
However, when a camera is mounted on a mobile phone, it is important to reduce the size and eliminate projections as much as possible due to the nature of the product of the mobile phone, making it difficult to provide an optical viewfinder. It is a usual method to display a moving image captured by a camera using a device.
[0009]
Here, the liquid crystal display device in the mobile phone is different from the liquid crystal display device (television display device) used in the viewfinder of the video camera. It displays the telephone number and name of the other party at the time, and in order to perform this display, it is necessary to write a display image directly from the CPU that controls the mobile phone, and the image signal from the camera is displayed. There is no dedicated interface, and it is necessary to once send the image captured by the camera to the liquid crystal display device via a bus managed by the CPU.
[0010]
A liquid crystal display device of a mobile phone is generally a small one having a diagonal length of about 2 inches and a number of pixels of about 120 × 160 pixels, and the amount of data passing through the bus managed by the CPU is not so large. It is possible to display a moving image that can be used to some extent (for example, about 5 to 10 frames / second).
[0011]
However, the number of pixels of a camera mounted on a mobile phone increases, and the number of pixels of a liquid crystal display device also changes from the above-mentioned 120 × 160 pixels to a high-definition liquid crystal of QVGA (320 × 240 pixels). In this case, the amount of data passing through the bus managed by the CPU described above increases and the number of display frames per second decreases. A major obstacle has occurred.
[0012]
An example of a format of a signal output from the camera 10 of the digital camera device will be described with reference to FIG.
[0013]
The image data is composed of three signals of luminance (Y) and color difference signals (U, V) for each pixel. These are each composed of 8-bit data, and the relationship between YUV and RGB of the three primary colors is
Y = 0.3R + 0.59G + 0.11B
U = Cr = RY
V = Cb = BY
It is represented by the following equation.
[0014]
FIG. 3A shows a data format called YUV422, where the luminance Y exists one by one for all pixels constituting an image. On the other hand, the color difference signals U and V exist one by one for two pixels of the luminance signal. That is, the elements that make up a certain pixel pixel # 1 of the image are (Y1, U1, V1), the elements that make up Pixel # 2 are (Y2, U1, V1), and the elements that make up pixel # 3 are (Y1, U1, V1). Elements constituting Pixel # 4 are (Y4, U3, V3). That is, in the horizontal resolution, the color difference is １ ／ of the luminance. This is to reduce the amount of information by utilizing the fact that the resolution of human eyes is lower in color resolution than luminance. In this case, the amount of information constituting one pixel is Y (8 bits) + (U (8 bits) + V (8 biy)) / 2 = 16 bits.
[0015]
FIG. 3B shows a data format called YUV420. As in the case of YUV422 shown in FIG. 3A, the luminance Y exists for every pixel constituting the image. On the other hand, the color difference signals U and V exist one by one for two pixels vertically and two pixels horizontally for the luminance signal Y. That is, the chrominance elements forming the pixels pixel # 1-2 and pixel # 321-322 of an image are (U1, V1), and the chrominance elements forming the pixel # 3-4 and the pixel # 323-324 are (U3, V3). ). That is, in the horizontal and vertical resolutions, the color difference is １ ／ of the luminance. In this case, the amount of information forming one pixel is Y (8 bits) + (U (8 bits) + V (8biy)) / 4 = 12 bits.
[0016]
An example of the form of image data captured by the digital camera device will be described with reference to FIG. FIG. 4B is a screen image of the captured image. The image data described in FIG. 3 is arranged in order from the upper left in the horizontal direction, the 320th pixel at the rightmost position, and the next line in the vertical direction. Finally, the lower right corner is the 320 × 240 pixel.
[0017]
FIG. 4A shows a format when the data shown in FIG. 3 is transferred through an 8-bit bus, and is followed by Y1, U1, Y2, and V1, and hereinafter, one line is composed of Y319, V319, Y320, and V320. The minute ends.
[0018]
An example of the time required for signal processing of the digital camera device will be described with reference to the table in FIG. The flow of the signal processing is a flow shown in FIG. 2 described below, and describes two types of the number of pixels of the captured image, 160 × 120 pixels and QVGA (320 × 240 pixels), and the image format is FIG. YUV422 indicated by.
[0019]
When the number of pixels is 160 × 120, the time required to capture the image captured by the camera and output it to the memory is 3.88 ms. Next, the time required to read the image from the memory, convert it to RGB, and output it to the memory is 15.52 ms. Next, the processing time of the LCD driver required to read this data from the memory, perform processing such as OSD, and output the data to the memory is 12 ms. Then, the time for transferring the data in the memory to be displayed on the LCD is 7.68 ms. The sum of these is 39.07 ms, which is the time required to process one frame during camera-through. By reversing this, the theoretically maximum frame rate achievable with this circuit is obtained, which is 25.59 fps here.
[0020]
Next, when the total processing time when an image of 320 × 240 pixels passes through the camera is similarly calculated, the total processing time is 120.30 ms. When this is inverted, it becomes 8.31 fps.
[0021]
A normal television signal is 30 fps (accurately, an image having a half vertical resolution is displayed at 60 fields per second), and a video CD has a speed of 30 fps for a 320 × 240 pixel image. In order to watch the image without being aware of the dropped frames, a frame rate of about 30 fps, at least 15 fps or more is required. On the other hand, in this method, an image of 320 × 240 pixels can be displayed only at about 8 fps, and only a small image as shown in FIG. 12C can be displayed.
[0022]
With reference to FIG. 12, an image of an image displayed on the LCD when the digital camera apparatus displays a moving image through a camera will be described.
[0023]
FIG. 12A shows a state in which the automobile 5 is running from left to right as a subject. FIG. 12B shows an image of each frame when this subject is displayed through the camera at, for example, 10 frames per second (10 fps). Cars running from the left end are G51, G52, G53, G54, G55, G56 and G57.
[0024]
FIG. 12C shows an image of each frame when this subject is displayed through the camera at 5 frames per second (5 fps), which is half of FIG. 12B. In FIG. 12 (b), seven frames are shown, but only four frames (G51, G53, G55, G57) are shown. Among them, only two frames can clearly show the position of the entire subject. Absent. When photographing while looking at a camera through image, if the movement of the subject is only sparse, it is difficult to accurately see the shooting target and shoot when shooting a moving object .
[0025]
Note that a camera for a silver halide photograph optically directly looks at a subject with an optical viewfinder, a single-lens reflex camera, or the like, and does not see such dropped frames. In addition, the digital still camera also has an optical viewfinder and can shoot while directly looking at the subject, so that this problem can be avoided. However, when the digital camera device according to the present invention has a limited shape, such as a mobile phone, it becomes difficult to install an optical viewfinder, and the equipped liquid crystal display device is used. If the photographing is performed using this, only the image as shown in FIG. 12C can be viewed, and a scene where photographing becomes difficult occurs.
[0026]
In order to avoid this problem, there is a method of increasing the speed of the bus managed by the CPU. In particular, in the case of mobile phones, due to the nature of the product, it is possible to secure a sufficient length of standby time and talk time. It is necessary to suppress power consumption as much as possible, and it is not preferable to increase the speed of the bus managed by the CPU. Similarly, it is necessary to use a memory with low current consumption. In this case, even if the speed of the bus is increased, the access speed of the memory is limited, and it becomes difficult to transfer data at high speed.
[0027]
Each still image forming a moving image is called a frame, and its display speed (the number of display frames per second) is called a frame rate, which is expressed in units of fps (frame per second). 30 frames / sec is described as 30 fps.
[0028]
The present invention has been made in view of the above problems, and in a digital camera device that displays captured image data on a liquid crystal display device continuously at a constant speed for each screen as digital data at a frame rate that can maintain a desired moving image quality. It is intended to perform image processing that can be displayed.
[0029]
That is, the present invention makes it possible to display a moving image without lowering the frame rate in a state in which a subject is observed on a liquid crystal display device before shooting, that is, in a so-called camera through state, and the subject is sufficiently observed in the liquid crystal display device. It is an object of the present invention to provide a digital camera device capable of taking a picture while shooting.
[0030]
[Means for Solving the Problems]
In order to solve the above problem, in the present invention, in a camera through state, the resolution of an image passing through a CPU bus is reduced with respect to the number of pixels of an actual captured image or a liquid crystal display image, without reducing the frame rate. indicate.
[0031]
At this time, the image to be actually photographed is photographed without lowering the resolution, and the still image obtained as a result of the photographing is displayed on the liquid crystal display device while maintaining the high resolution. In this case, since a still image is displayed, there is no need to consider the problem of a decrease in frame rate.
[0032]
In addition, as a condition that this method can be applied, the camera's optical system does not need to be focused while directly viewing the photographed image by the user's own eyes by using a fixed focus method, an automatic focusing device, or input of the distance measurement result etc. It is assumed that In this point, particularly, since a camera mounted on a mobile phone is an ultra-small camera, the focal length L of the optical system is extremely short (specifically, L = about 2 to 3 mm), and the depth of the subject is sufficiently deep. Therefore, it is basically possible to use a fixed focus, and this method is useful.
[0033]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a specific example of an embodiment of a digital camera device according to the present invention will be described with reference to the drawings. An example of the system configuration of the digital camera device according to the present invention will be described with reference to the circuit block diagram of FIG. The digital camera device 1 includes a camera 10, a capture circuit 11, an image conversion circuit 12, a built-in RAM 121, an LCD driver 13, a liquid crystal display device (hereinafter also referred to as an LCD) 14, an SRAM 15, a CPU 18, It has a switch 20, an external device interface 21, an external storage interface 22, and a bus interface 23. The capture circuit 11, the image conversion circuit 12, and the built-in RAM 121 are connected to the high-speed bus B2. The LCD driver 13, the LCD 14, the SRAM 15, the CPU 18, the operation switch 20, the external device interface 21, and the external storage interface 22 are connected to a CPU bus B1 managed by the CPU 18. The CPU bus B1 and the high-speed bus B2 are connected via a bus interface 23.
[0034]
The camera 10 is an imaging device that outputs, for example, VGA size 640 × 480 pixel video data.
[0035]
The capture circuit 11 is a circuit that receives YUV422 format image data continuously transmitted from the camera 10 at a constant speed in accordance with an external synchronization signal of the camera 10 and outputs the image data to the memory 15. It has the function of converting the number into 160 × 120 pixels and keeping the VGA size when displaying a still image.
[0036]
The image conversion circuit 12 is a circuit that converts image data in YUV422 format into RGB format.
[0037]
The built-in RAM 121 is composed of a high-speed memory used for temporary storage of photographed images and a work area for image conversion.
[0038]
The LCD driver 13 is a circuit that controls the LCD 14 to display image data in the RGB format on the LCD 14, and has a function of enlarging image data of 160 × 120 pixels to image data of 320 × 240 pixels during camera-through. are doing.
[0039]
The LCD 14 is a device that displays an image in the RGB format with 320 × 120 pixels.
[0040]
The SRAM 15 is a memory that temporarily stores the image data of the YUV422 format and the image data of the RGB format during the camera-through state, and temporarily stores the image data of the YUV422 format when capturing the still image.
[0041]
The CPU 18 controls the entire system of the digital camera device and performs a JPEG encoding process and a JPEG decoding process.
[0042]
The operation switch 20 is a unit for inputting an operation of the device by a user.
[0043]
The external device interface 21 is an interface for connecting the digital camera device to external devices such as a personal computer and a printer.
[0044]
The external storage interface 22 is an interface for connecting the external storage medium 3 such as a memory card for storing captured image data.
[0045]
The bus interface 23 is an interface for connecting the CPU bus B1 and the high-speed bus B2.
[0046]
The CPU bus B1 is a bus managed by the CPU 18.
[0047]
The high-speed bus B2 is a high-speed bus different from the CPU bus B1.
[0048]
An input image from the camera 10 is captured by a capture circuit 11. In the present embodiment, the capture circuit 11, the image conversion circuit 12, and the built-in RAM 121 composed of a high-speed memory used for a temporary storage of a captured image and a work area for image conversion are different from the CPU bus B1 managed by the CPU. High-speed bus B2, and both buses are connected by a bus interface 23.
[0049]
By this method, for example, even when a SRAM having a large number of waits is used, the capture and image conversion processing can be performed at high speed. In this embodiment, the CPU bus B1 and the high-speed bus B2 are different buses. However, the same bus may be used as long as the frame rate of the camera through satisfies the design specification of the camera. Here, by separating the CPU bus B1 and the high-speed bus B2, it is possible to prevent a conflict between CPU processing required for operating the camera device and memory access required for capturing.
[0050]
Image data captured by the camera 10 is captured by the capture circuit 11, and the processing shown in FIG. 2 is performed by the image conversion circuit 12 and the built-in RAM 121 connected to the high-speed bus B2. However, since the amount of information of the image data is large, it is necessary to temporarily store the image data in the SRAM 15 connected to the CPU bus B1 via the bus interface 23 for each processing of each frame.
[0051]
An example of a flow of image data until a captured camera-through image is displayed on a liquid crystal display device in the digital camera device according to the present invention will be described with reference to the processing block diagram of FIG.
[0052]
An imaging device (hereinafter, referred to as a camera) 10 can capture an image having a maximum VGA size (640 × 480 pixels) in number of pixels, and image data captured by the camera is captured by a capture circuit of a digital camera device. 11 is fetched by the capture process P11. Since the image data from the camera 10 is continuously transmitted at a constant speed as shown in FIGS. 3 and 4, a capture process P11 for receiving this data in accordance with an external synchronization signal from the camera is required. become.
[0053]
The image data received in the capture process P11 is VGA size image data in the YUV422 format shown in FIG.
[0054]
In this embodiment, the number of display pixels of the LCD 14 is a QVGA size (320 × 240 pixels), but the number of pixels transferred on the CPU bus B1 during camera through of the digital camera device according to the present invention is 160 × 120. Set as pixel. The conversion of the image size from the VGA size to 160 × 120 pixels is performed in the capture processing P11, but if the camera 10 has the function, it may be used. In this case, the capture process P11 writes the image data received from the camera into the memory 15 without changing the size. In addition, the camera 10 may use both the function of the camera and the function of the capture processing. By performing not only the reduction from the original size but also the size conversion by cutting out, the digital zoom function can be achieved. it can.
[0055]
The image data 151 of 160 × 120 pixels in the YUV422 format, which is taken into the memory 15 by the capture process P11, is read into the image conversion circuit 12 and subjected to the image conversion process P12, and the image data 152 of 160 × 120 pixels in the RGB format is obtained. And output to the memory 15 again. Next, the image data 152 is read by the LCD driver 13 and subjected to an LCD display control process P13. The image data 153 is output to the memory 15 again as pixel image data 153. The image data 153 is output to the LCD 14 by a high-speed memory transfer method such as DMA and displayed.
[0056]
At this time, the image data of 160 × 120 pixels is enlarged to 320 × 240 pixels according to the size of the LCD 14. The enlargement of the pixels is performed by displaying the image data 153 on the memory 15 as a 320 × 240 pixel size by the LCD display control process P13, or by converting the image data 153 of 160 × 120 pixels processed by the LCD display control process P13 into the LCD14. There is a method in which the display is enlarged twice by the internal circuit of FIG. In the latter case, the transfer of the image data on the CPU bus is all 160 × 120 pixels, so that higher speed can be achieved.
[0057]
In this way, the image at the moment when the shutter is pressed in photographing the still image after confirming the image on the LCD 14 is photographed in the VGA size (640 × 480 pixels). The VGA-size still image is captured in the VGA size by the capture process P11, input to the JPEG encoding process P16 via the memory 15, is subjected to image data compression, and is output as a JPEG file 17.
[0058]
Referring to FIG. 2, a flow of processing when a VGA-size still image stored in the JPEG file 17 is displayed on the LCD 14 will be described with reference to FIG.
[0059]
The photographed still image stored in the JPEG file 17 is subjected to JPEG decoding processing P19, transferred to the memory 15 as VGA-sized YUV422 format image data 151, and then converted to 320 × 240 in accordance with the LCD size in processing after image conversion processing P12. The size is converted to pixels and displayed on the LCD. Since the display at this time is a still image, it is not necessary to perform high-speed transfer according to the frame rate at the time of camera-through, and there is no speed problem even if 320 × 240 pixels are transferred.
[0060]
Here, in the block diagram shown in FIG. 1, there are two types of buses, a CPU bus B1 and a high-speed bus B2. During this period, data is exchanged by connecting with the bus interface 23, and the high-speed bus B2 is used. During this period, high-speed operation can be performed according to the bus clock of the high-speed bus, but they cannot be used at the same time, and the total processing time needs to be the sum of the time spent using each bus.
[0061]
With reference to FIG. 6, a method for high-speed camera through display of the digital camera device according to the present invention will be described. FIG. 6 is an example of a block diagram showing the flow of image data. Details of each process are shown in FIG. 2, and the description is omitted here.
[0062]
FIG. 6A shows a conventional case where a captured image is captured with 320 × 240 pixels and each processing is performed at the size in order to display an image of 320 × 240 pixels on an LCD. This is a case where the digital camera apparatus of the present invention sets the capture size in the camera through to 160 × 120 pixels, and after performing each processing at that size, enlarges it to 320 × 240 pixels when displaying on the LCD.
[0063]
In FIG. 6A, the image data between the memory 15 and the capture process P11, the image conversion process P12, the LCD display control process P13, and the LCD 14 are transferred at 320 × 240 pixels, respectively. Use time increases.
[0064]
On the other hand, in the processing method according to the present invention shown in FIG. 6B, since the image data in the camera through is transferred by 160 × 120 pixels, the use time of the CPU bus B1 can be reduced.
[0065]
The enlargement at the time of display on the LCD 14 in FIG. 6B can be achieved by simply arranging the same pixel data in a total of 4 pixels, that is, 2 pixels vertically and horizontally, or, if processing load permits, displaying a smooth image by interpolating between the pixels. May be. The enlargement processing may be performed by LCD display processing. However, if there is a double enlargement processing circuit inside the LCD, the image data on the CPU bus B1 can be reduced to a minimum size of 160 × 120 pixels by using the processing circuit. As a result, processing time can be reduced, and the bus use time can be reduced.
[0066]
An example of a liquid crystal display screen when a camera through image is displayed at high speed in the digital camera device according to the present invention will be described with reference to FIG.
[0067]
FIG. 7A shows a conventional example of a camera-through image displayed on a liquid crystal display device. FIG. 7B is an enlarged view of this.
[0068]
FIG. 7C is an enlarged view of a camera through image of the digital camera device according to the present invention. In the present invention, it can be seen that the resolution is halved compared to FIG. 7B and the pixels are coarse. Although such a coarse image is obtained on the enlarged screen, when the entire screen is viewed as shown in FIG. 7A, it is possible to understand what is shown in the screen. The effect of the present invention is that the image of FIG. 7A is displayed as shown in FIG. 12C, and the image of FIG. This is to display at a high frame rate as shown in FIG. In this case, in contrast to FIG. 7B, it is considerably difficult to focus while looking at the screen in FIG. 7C. The problem is that cameras used in mobile devices have an autofocus function that has a small sensor area, has a fixed focus by using a short focus lens, does not require focusing, or has a control mechanism that closes inside the camera module. By using a method that does not require visual focusing of the camera through image by using a method such as using a user to measure the distance by eye measurement and specifying the number by, for example, a mechanical method of the focus position of the lens in meters. Can be avoided.
[0069]
The processing time for each frame in the digital camera device according to the present invention will be described with reference to the timing chart of FIG.
[0070]
A time T1 in FIG. 8A is a cycle time for each frame at the time of camera through. That is, assuming that the operation is performed at 15 fps, the cycle time T1 = 1/15 = 66.6 ms. The capture of the image data from the camera in the capture processing starts from the vertical synchronization signal S1, and the time required for capture is the capture processing time T2. The capture processing time T2 <the cycle time T1, and the cycle time T1-the capture processing T2 = T4 is a blanking area of a video. The image captured at the time of the frame F1 is subjected to image conversion and transfer to the LCD in the next frame F2. The time required for this is the conversion transfer time T3, and the conversion transfer time T3 <cycle time T1 is an essential condition for each frame to be able to capture and display without failure. Here, the capture processing time T2 and the conversion transfer time T3 are the times required for the entire processing, and these two are performed simultaneously using the same bus.
[0071]
FIG. 8B is an enlarged view of the timing chart shown in FIG. 8A, in which an image to be processed in the frame F3 in the frame F2 in FIG. This is an explanation of the operation of simultaneously performing image conversion and LCD display. All are Lo active, indicating that the processing is being performed when Lo. The processing described here can be observed with a chip select signal indicating access to the memory and a chip select signal indicating writing to the LCD.
[0072]
After the vertical synchronizing signal is input, the capture of the frame F2 is performed at regular intervals for the number of pixels. A value obtained by dividing the frame rate of the camera by the number of pixels, that is, the timing at which image data is sent from the camera one pixel at a time (specifically, assuming that the image data is captured at 15 fps of QVGA pixel data, 1 sec {15 fps} (320 × 240 ) = 0.86 μs), the time required to write it to the memory is much shorter (eg, 100 ns using SRAM), and the total access time to the memory by capture is shorter than the time for one frame. And short.
[0073]
In the gap between the captures, the image conversion F1 of the image captured in the immediately preceding frame F1 and the LCD display F1 are performed. The conversion transfer time T3 shown in FIG. 8A is expressed by the memory access time at the time of capture, and the sum of image conversion and LCD display.
[0074]
An example of a method of changing the number of pixels according to the frame rate in the digital camera device according to the present invention will be described with reference to the flowchart in FIG.
[0075]
By comparing the cycle time T1 shown in FIG. 8 with the conversion transfer time T3 (step S01), if the conversion transfer time T3> cycle time T1 (No), it is determined that a predetermined frame rate cannot be secured, and Reduce the number and reduce the amount of data transferred. At this time, the minimum value of the number of pixels is set so that the image displayed on the LCD screen does not extremely feel a sense of discomfort in reducing the number of pixels, and it is determined whether the current number of display pixels is already the minimum (step S02). When the number of display pixels is already the minimum number of pixels (Yes), the setting is not changed. In this case, since the conversion transfer time T3 required for the image conversion processing and the LCD display processing exceeds the cycle time T1, the image captured at that time is discarded, and the processing for displaying the image at the next capture is performed. Do. If the current number of display pixels is not the minimum number of pixels, a process of reducing the number of pixels (step S03) is performed, and the number of pixels is reduced to make the conversion transfer time T3 equal to or less than the cycle time T1.
[0076]
When the conversion transfer time T3 required for the image conversion processing and the LCD display processing is less than or equal to the cycle time T1 (step S01, Yes), the conversion transfer time T3 required for the processing with respect to the frame rate has a margin, so In order to know whether it is possible to process the image data, it is determined whether or not the current number of display pixels is the maximum (step S04). If the current number of display pixels is equal to or less than the maximum number of pixels (step S04, No), a setting to increase the number of pixels is performed (step S05). At this time, the number of display pixels of the LCD is the maximum number of pixels. If the number of pixels does not exceed the maximum number of pixels, the number of pixels is increased.
[0077]
With reference to the block diagram of FIG. 10, a description will be given of a method of making a decision to change the number of pixels according to the frame rate in the digital camera device according to the present invention.
[0078]
The description of the operation at the time of camera through in the block diagram of FIG. 10 is the same as that of FIG. Here, when the digital camera device according to the present invention has a function of compressing a captured image in the MPEG format, the MPEG encoding processing function P161 is used to reduce the cycle time T1 and the conversion transfer time T3 shown in FIG. A comparison can be made.
[0079]
The MPEG encoding processing function P161 captures and compresses frames coming at regular intervals to create an MPEG file 171. When the compression completion time of the first frame F1 exceeds the capture start time of the next frame F2, the MPEG encoding processing function P161 skips the frame F2 and waits for an image input until the next frame F3. And perform the next compression. Whether the current number of display pixels in FIG. 9 is the minimum or the maximum can be determined by the presence or absence of the skipping of the frame (frame processing time excess / shortness determination signal).
[0080]
A method of displaying an OSD (On Screen Display) in the digital camera device according to the present invention will be described with reference to the block diagram of FIG.
[0081]
As shown in FIG. 7, when the digital camera device according to the present invention performs camera-through at a high frame rate, the resolution of an image displayed on the LCD 14 decreases. At this time, when characters and illustrations are superimposed on the screen by OSD processing, if the OSD with the same resolution as the display image is superimposed before the resolution is reduced, such as at the time of capture, the resolution of the OSD itself displayed on the LCD also decreases. I do.
[0082]
More specifically, when an image of 320 × 240 pixels is photographed and characters and illustrations are to be superimposed and stored, the resolution of the camera through image once decreases to 160 × 120 pixels. Therefore, when the superimposed characters and illustrations are displayed on the LCD through the camera through, the resolution is 160 × 120 pixels, which makes it difficult to read the characters and makes it difficult to see the details of the illustrations. As shown in FIG. 11, in the present invention, characters and illustrations having the same number of pixels as the captured image and the display resolution of the LCD are generated in the OSD process P191, and are generated in the LCD display control process P13 or the LCD 14 immediately before the LCD display. The characters and illustrations are displayed without any resolution degradation on the LCD display during camera-through.
[0083]
Then, on the photographed image, the characters and illustrations generated by the OSD processing P192 are superimposed on the photographed image and JPEG encoding processing P16 is performed to create a JPEG file 17, thereby superimposing the same high-resolution characters and illustrations as the photographed image. It can be performed.
[0084]
【The invention's effect】
According to the present invention described above, in a camera-through state in which a subject is observed with a liquid crystal before photographing, the resolution of an image passing through a CPU bus is reduced with respect to the number of pixels of an actual photographed image or a liquid crystal display image. The display can be performed without lowering the frame rate, and the subject can be photographed while being sufficiently observed with the liquid crystal display device.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an example of a system configuration of a digital camera device according to the present invention.
FIG. 2 is a block diagram illustrating an example of a flow of image data until a camera through image captured by a digital camera device according to the present invention is displayed on a liquid crystal display device.
FIG. 3 is a view for explaining an example of a format of a signal output by a camera of the digital camera device.
FIG. 4 is a diagram illustrating an example of the form of image data captured by a digital camera device.
FIG. 5 is a block diagram illustrating an example of a flow of image data until a stored image captured by the digital camera device according to the present invention is displayed on a liquid crystal display device.
FIG. 6 is a block diagram illustrating an example of a flow of image data showing a method for performing high-speed camera through display of a digital camera device.
FIG. 7 is a view for explaining an example of a liquid crystal display screen when a camera-through image of the digital camera device is displayed at a high speed.
FIG. 8 is a timing chart illustrating an example of a processing time for each frame of the digital camera device according to the present invention.
FIG. 9 is a flowchart illustrating an example of a method of changing the number of pixels according to the frame rate of the digital camera device according to the present invention.
FIG. 10 is a block diagram illustrating an example of a method for making a determination to change the number of pixels according to the frame rate of the digital camera device according to the present invention.
FIG. 11 is a block diagram illustrating an example of an OSD display method of the digital camera device according to the present invention.
FIG. 12 is a diagram illustrating an example of a camera-through display of a moving image of the digital camera device.
FIG. 13 is a table showing an example of time required for signal processing of the digital camera device.
[Explanation of symbols]
1 Digital camera device
3 External storage media
5 subject
10 Camera
11 Capture circuit
12 Image conversion circuit
13 LCD driver
14 LCD
15 Memory (SRAM)
17 JPEG files
171 MPEG file
18 CPU
20 Operation switch
21 External device interface
22 External storage interface
23 Bus Interface
B1 CPU bus
B2 Express Bus
P11 Capture processing
P12 Image conversion processing
P13 LCD display control processing
P16 JPEG encoding process
P161 MPEG encoding process
P191, P192 OSD processing

Claims (13)

A camera having an interface for continuously outputting captured image data as digital data one screen at a time at a constant speed, an interface for receiving a signal from the camera, and a capture circuit having a function of writing the captured image data to a memory; It has a memory for writing data and a liquid crystal display device for reading and displaying the image data captured in the memory, and does not have an optical finder for visually confirming a substantially same shooting range as an object to be shot by a camera at the time of shooting, In a digital camera device for confirming a subject to be photographed by the liquid crystal display device before photographing,
A digital camera device, wherein the number of pixels of one screen of image data output from the camera at a constant speed ≧ the number of pixels of an image display area of the liquid crystal display device> the number of pixels of image data displayed on the liquid crystal display device. . The digital camera device according to claim 1,
An image conversion circuit for converting the format of the image data, wherein the number of pixels of the image data displayed on the liquid crystal display device> the number of pixels of the image data transferred between the capture circuit or the image conversion circuit and the memory; Digital camera device. The digital camera device according to claim 1 or 2,
A digital camera device wherein image data displayed on a liquid crystal display device is enlarged and displayed on the liquid crystal display device. The digital camera device according to any one of claims 1 to 3,
The number of pixels of the image data to be captured and stored ≧ the number of pixels of the image display area of the liquid crystal display device, and the number of pixels of the image data when the stored image data is displayed on the liquid crystal display device = the image display area of the liquid crystal display device A digital camera device characterized in that the number of pixels is: The digital camera device according to any one of claims 1 to 4,
A digital camera device, wherein the number of pixels of image data displayed on a liquid crystal display device is variable. The digital camera device according to claim 5,
The number of pixels of the image data to be displayed on the liquid crystal display device is, if the speed required for transfer and display to the liquid crystal display device is slower than the speed at which the camera continuously outputs one screen at a time, A digital camera device characterized in that it is reduced. The digital camera device according to claim 6,
The number of pixels of the image data to be displayed on the liquid crystal display device increases when the speed required for transfer and display to the liquid crystal display device is faster than the speed at which the camera continuously outputs one screen at a time at a constant rate. A digital camera device characterized by causing the digital camera device to: The digital camera device according to claim 6,
A digital camera, wherein a lower limit of the number of pixels of image data to be displayed on the liquid crystal display device is set in advance, and when the number of pixels of the image data reaches the lower limit, the number of pixels of image data is not reduced. apparatus. The digital camera device according to claim 7,
A digital camera device wherein the upper limit of the number of pixels of image data displayed on the liquid crystal display device is the number of pixels of an image display area of the liquid crystal display device. The digital camera device according to any one of claims 6 to 9,
The comparison between the speed at which the camera continuously outputs one screen at a time and the speed required for transfer and display to the liquid crystal display device is based on the time required for outputting one screen from the camera and the time required for the liquid crystal display device. A digital camera device characterized by performing comparison with the time required for transfer and display. The digital camera device according to any one of claims 6 to 9,
The comparison between the speed at which the camera continuously outputs one screen at a time at a constant speed and the speed required for transfer and display to the liquid crystal display device is based on the time required for outputting one screen from the camera and the time required for the digital camera device. A digital camera device wherein the comparison is made with the time required for moving image compression processing. The digital camera device according to claim 3,
Characters and illustrations can be superimposed on image data to be captured and stored, and at the time of photography, the number of display pixels of the characters and illustrations = the number of pixels in the image display area of the liquid crystal display device A digital camera device characterized by the above-mentioned. The digital camera device according to claim 12,
A digital camera device, wherein the number of pixels of characters and illustrations to be superimposed on image data to be photographed and stored = the number of pixels of image data to be photographed and stored.

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