KR100929386B1 - Resolution Evaluation System for Digital Cameras Adopting High Speed Serial Communication Standards - Google Patents

Abstract

An apparatus for evaluating the resolution of a digital camera employing a high speed serial communication standard is disclosed. According to an aspect of the present invention, an apparatus for evaluating resolution of a digital camera according to a high speed serial communication standard from a digital camera includes a video data capture unit configured to capture and output received digital video data; An image data storage unit for storing the captured and output digital image data; An image processor extracting RGB color data for each pixel from the captured digital image data, and converting RGB color data to obtain luminance data for each pixel; A graph implementation unit for graphing luminance values in two or three dimensions using luminance data for each pixel; And an image capturing control unit which drives a focus lens to capture an image of the digital camera, adjusts the focus of the image, captures the image while the focus is adjusted, and white balances the captured image. Therefore, the objective resolution of the digital imaging apparatus digitally transmitted by the high speed serial communication standard such as IEEE1394 can be evaluated, and in particular, the performance evaluation of the digital imaging apparatus at the research or manufacturing site, the performance of the adjustment process, the quality assurance process, etc. In performing the above, resolution evaluation can be easily performed.

Description

Apparatus for evaluating resolution of digital camera adopting high speed serial communication standard}

1 is a view schematically showing an example of a conventional analog resolution system for evaluating the performance of a CCD camera.

2 is a block diagram illustrating a digital camera and a resolution evaluation apparatus according to the present invention connected thereto.

3 is an example of an image of a resolution evaluation chart to be evaluated by the resolution evaluation apparatus according to the present invention.

4 is an example in which the captured image is displayed by the graph implementation unit 240 as a 3D luminance distribution graph.

5 is an example in which the graph implementation unit 240 detects an edge in a horizontal direction (x direction) and displays it in a 3D graph.

6 illustrates an example in which the graph implementation unit 240 detects an edge in a vertical direction (y direction) and displays it in a 3D graph.

7 is a flowchart illustrating an example of a method of measuring edge resolution by detecting an edge from an image of the resolution evaluation chart illustrated in FIG. 3 in the graph implementation unit 240.

8 is an example of a screen for setting the threshold of the luminance level and the luminance difference for detecting the edge by the user interface.

Fig. 9 is a graph showing edge changes of 300 TV bone lines.

Fig. 10 is a graph showing the edge change of the 500 TV bone line.

11 is an example of a gray scale chart to be evaluated by the resolution evaluation apparatus according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for evaluating the resolution of a digital camera, wherein the digital image signal is transmitted to a device such as a PC by a high speed serial communication such as IEEE 1394 (Institute of Electrical and Electronics Engineers 1394) and / or Universal Serial Bus 2.0 (USB2.0). It relates to a resolution evaluation apparatus of a digital camera for transmitting the.

Imaging devices (CCTVs, real imagers, camcorders, etc.) that display images taken by CCD (Charge Coupled Device) cameras are rapidly digitizing, and recently, analog image data In addition, a technology for transmitting a digital image to an external device such as a PC and displaying or performing additional image processing is becoming common. Digital signals are transmitted from digital cameras and transmitted, and external devices such as a PC receive the images using DirectX, which is a codec (codec, coder / decoder) that meets the specifications of the transmitted digital images. Output or store digital image data. Here, Direct X is a set of multimedia application program interfaces (APIs) developed by Microsoft Corporation in the United States, and includes various media such as two-dimensional and three-dimensional figures, voices, and moving images. Allows an application program that uses direct access to a hardware device to process at high speed.

In particular, with the development of high speed serial communication interface technologies such as IEEE 1394 and USB2.0, such a task has been facilitated due to the faster high speed transmission speed. The IEEE 1394 communication standard is emerging as a communication technology for next generation computers, and is hardware and software capable of transmitting data at 400 Mbps, 200 Mbps, or 100 Mbps. According to the IEEE 1394 standard, a digital signal is transmitted as a digital signal itself without being converted into an analog signal. USB connects peripherals in a tree structure as a whole, and is capable of delivering a transmission speed of 12Mbps and a subchannel of 1.5Mbps at low cost.

As the camera becomes digital, the development of a new measurement method for evaluating the performance of a digital camera using digital data transmitted through a high speed serial communication interface is urgent.

1 is a view schematically showing an example of a conventional analog resolution system for evaluating the performance of a CCD camera. In the resolution evaluation system shown in FIG. 1, the resolution evaluation chart 10 is photographed by the CCD camera 20, and transmitted to the oscilloscope 50 and / or the high resolution monitor 60 through the coaxial cable 30. Evaluate the resolution of 20). However, the evaluation of the resolution by visual observation of the monitor 50 is inaccurate and the subjective factor of the evaluator is largely involved. In addition, the resolution evaluation by the oscilloscope 40 can only be evaluated in a limited range in which the function of the oscilloscope 40 is provided. In addition, the resolution evaluation by the conventional method is inefficient when applied to performance evaluation and quality control during the manufacturing process due to the inaccuracy and hassle of the evaluation itself. In addition, there are difficulties in terms of utilization in improving performance of digital cameras by systematic backup and systematic evaluation of data.

In Korean Laid-Open Patent Publication No. 1999-054492 (published Jul. 15, 1999), an image pickup means for outputting an electric signal corresponding to an optically imaged object, and an electric signal output from the image pickup means 1 Signal processing means for generating image data corresponding to a frame, and IEEE 1394 controller for transmitting the image data output from the signal processing means in accordance with a set communication standard, Digital cameras for photographing the subject using an image sensor Disclosed is a digital camera processing apparatus having a high speed serial communication function capable of transmitting large amounts of video data quickly by transmitting image data photographed according to a high speed serial communication standard. However, the device using the conventional IEEE 1394 controller and / or USB controller does not include the resolution measurement and evaluation function of the digital image.

Accordingly, a technical problem of the present invention is to numerically analyze a digital signal transmitted from a digital camera in accordance with IEEE 1394 and USB standards, and to objectively analyze the digital signal, and to easily evaluate the digital camera by three-dimensional or two-dimensional graphics. It is to provide a new resolution evaluation device.

In order to achieve the above technical problem, the resolution evaluation apparatus of the digital camera according to the present invention for evaluating the resolution from the digital image data received by the high speed serial communication standard from the digital camera, to capture and output the received digital image data An image data capture unit; An image data storage unit for storing the captured and output digital image data; An image processor extracting RGB color data for each pixel from the captured digital image data, and converting the RGB color data to obtain luminance data for each pixel; A graph implementer configured to graph luminance values in two or three dimensions using the luminance data of each pixel; And an image capturing control unit configured to adjust a focus of the image by driving a focus lens for capturing an image of the digital camera, to capture an image while the focus is adjusted, and to white balance the captured image.

Hereinafter, with reference to the accompanying drawings the configuration and operation of the resolution evaluation apparatus of the digital camera according to the present invention will be described in detail as follows.

FIG. 2 is a block diagram illustrating a digital camera 100 and a resolution evaluation apparatus 200 according to the present invention. The image capture unit 210, the image data storage unit 220, the image processing unit 230, The graphic implementer 240, the image capturing controller 250, and the high speed serial communication interface 260 are included.

The resolving power evaluation apparatus 200 of the digital camera according to the present invention evaluates the resolving power from digital video data received from the digital camera 100 according to a high speed serial communication standard such as IEEE 1394. IEEE 1394 is a new serial interface standard that has been standardized by the Institute of Electrical and Electronics Engineers (IEEE) .It is not only a computer peripheral device but also a device such as a digital camera, an audio component, a TV, and a video cassette recorder (VCR). It is a high speed serial communication standard developed as an interface for connecting to a PC). Three data rates are specified: 100 Mbps, 200 Mbps, and 400 Mbps. Universal Serial Bus (USB) is a new peripheral interface specification jointly proposed by seven companies including Intel, Microsoft, Compaq, DEC, IBM, Nortel, Canada, and NEC. It is an interface for connecting printers, modems, speakers, and other peripherals to a PC.

The high speed serial communication interface unit 260 interfaces between the resolution evaluation apparatus 200 and the digital camera 100 according to the present invention so as to transmit and receive digital image data according to a high speed serial communication standard. The interface unit 260 is implemented to include an IEEE 1394 controller (not shown) and an IEEE 1394 connector (not shown) for performing communication protocols and data error checks required for digital data transmission and reception.

The image capture unit 210 captures and outputs digital image data received from an external digital camera 100 via a high speed serial communication standard such as IEEE 1394 through the interface unit 260. The image capture unit 210 includes video hardware such as a graphic card (not shown) to capture digital image data. At this time, the image data capture unit 210 may be implemented to capture the received digital image data, convert it into a Windows bitmap format of Microsoft Corporation which is commonly used as a user interface of a PC. have. For example, Microsoft's DirectDraw Class or the like can be used to convert still images into the Windows bitmap format.

The image capturing control unit 250 controls the focus of the image by driving the focus lens for optimal image capturing of the digital camera 100, and controls the image capturing control to capture an image in a state where the focus is adjusted. In order to precisely evaluate the resolution, the image should be optimally taken first. The image capturing control unit 250 is provided to achieve the shooting condition of the optimal image. In addition, the image capturing controller 250 performs a white balance process on the captured image. Here, the white balance is a function to adjust the color balance when shooting based on white in order to prevent the image captured by the color temperature of the light source from changing, and is mounted on a camera such as a digital camera or a video tape recorder (VTR). to be.

The data storage unit 220 stores the digital image data captured and output by the image capturing unit 210 and the two-dimensional or three-dimensional graphed data by the graph implementing unit 240.

The image processor 230 extracts RGB color data for each pixel from the digital image data captured by the image capture unit 210, and converts the RGB color data to obtain luminance data Y for each pixel. . Color models include the RGB color model used in color monitors and color digital cameras, the YIQ color model used in color TV broadcasting, and the YCbCr color model used in digital video components. The evaluation of the resolution of the digital camera is based on the evaluation of the luminance difference Δ. Therefore, as the data of the pixel used for the resolution evaluation in the present invention, the Y value, which is the luminance value of the YIQ color model or the YCbCR color model, is converted from the data using the RGB color model according to the following equation (1).

Y = 0.29900R + 0.58700G + 0.11400B

Here, the luminance value Y has a value between 0 and 255, for example, when the R, G, and B color data are each represented by 256 gray levels.

The graph implementer 240 graphs the luminance value in two or three dimensions using the luminance data for each pixel input from the image processor 230. Here, the graph implementation unit 240 implements a 3D luminance distribution graph by mapping the pixel position of the captured image to the x coordinate in the horizontal direction and the y coordinate in the vertical direction and displaying the magnitude of the luminance data in the z coordinate. . 4 is an example in which the captured image is displayed by the graph implementation unit 240 as a 3D luminance distribution graph. As shown in the figure, the position scale in the x-y coordinate axis direction and the luminance value scale in the z coordinate axis direction can be displayed on the graph.

In addition, when the graph implementation unit 240 expresses the luminance distribution graph, color values may be designated for each luminance level and displayed on the z coordinate as shown in Table 1 so that the user may easily identify and evaluate the luminance distribution graph.

color Black Purple blue sky green yellow Orange Red back Luminance level 0-15 16-40 41-70 71-100 101-150 151-170 171 to 200 201 to 230 231 to 255

In addition, the graph implementation unit 240 maps the pixel position of the captured image to the horizontal x coordinate and the vertical y coordinate in one-to-one, and the luminance difference Δ between pixels adjacent in the horizontal or vertical direction is greater than a predetermined threshold. A large case may be displayed on the z-axis to implement a three-dimensional graph that detects an edge. An edge means a distinct boundary between bright and dark areas of an image, and is an outline identified when the luminance difference Δ between adjacent pixels is larger than a predetermined threshold. FIG. 5 is an example in which the graph implementation unit 240 detects an edge in the horizontal direction (x direction) and displays it in a 3D graph. FIG. 6 illustrates an example in which the graph implementation unit 240 detects an edge in a vertical direction (y direction) and displays it in a 3D graph.

FIG. 7 is a flowchart illustrating an example of a method of measuring edge resolution by detecting an edge from an image of the resolution evaluation chart illustrated in FIG. 3 in the graph implementation unit 240. The luminance difference between adjacent pixels is illustrated in FIG. Calculating step (S10), determining the trend of the edge detected in the line of interest, counting the number of bones (step S20), and determining whether to terminate the edge detection (step S30). It includes.

For edge detection, for example, when edge detection is performed in the horizontal x direction, one line in the x direction belongs to the attention line currently processed, and the current pixel in the y direction currently processed is transferred to the attention pixel. After the edge is detected by calculating the luminance difference? Between the pixel and the pixel of interest, the edge detection is performed using the next pixel in the y direction as the pixel of interest. After the last pixel in the y direction of the line of interest is processed, edge detection is performed using the next line in the x direction as the line of interest.

Referring to the edge detection method in more detail, first, in step S10, the luminance difference Δ of the pixel of interest and the previous pixel is calculated. The luminance difference Δ may be negative or positive. That is, the pixels may progress in the direction in which the image darkens, and the luminance may decrease, or the pixels may progress in the direction in which the image brightens, and the luminance may increase.

In step S20, the count is increased by one when the absolute value of the luminance difference Δ is equal to or greater than a predetermined threshold and the edge of the trend of decreasing brightness and the edge of the trend of increasing brightness are detected in pairs (step S20). For example, if the luminance value of the previous pixel is 250 and the luminance value of the current pixel is 100, the luminance tends to decrease, and the edge is inverted from black to white, and vice versa. A bone is recognized as identified only when the edge inverted from white to black and the edge inverted from black to white are detected in pairs. In this case, the determination of the predetermined threshold may be input by the user through the user interface.

In step S30, it is determined whether edge detection is to be finished. There are various conditions for terminating the edge detection. In the last line in the x direction, the process may end to the last pixel in the y direction. It may also be terminated when the number of bones detected and counted in the line of interest falls below a predetermined number. In this way, the marginal resolution can be measured. In other words, it can be seen that the number of bones counted in the line where the edge detection is completed falls below a predetermined number, and the position of the line where the edge detection is completed can be known. At this time, if the position of the line where the edge detection is completed is identified and the resolution or the number of bones detected at the position is displayed, the user who evaluates the resolution can easily measure the marginal resolution.

The edge detection method described in the above steps S10 to S30 may be performed by changing the x direction and the y direction, or may allow a user who evaluates the resolution to specify the moving direction. In addition, edge detection may be performed by allowing a user to designate a line in the x direction to perform edge detection. In this case, in step S30, edge detection ends when processing of the last pixel of the corresponding line ends, and detection is performed on the line. It may be implemented to indicate the number of bones made. Referring to FIG. 3, which shows an image of a resolution evaluation chart, the scales displayed on the left and right sides of the figure indicate the number of TV copies for resolution evaluation. For example, the scale '3' means that the resolution of the horizontal line is 300 TV, the scale '5' means that the resolution of the horizontal line is 500 TV, and the scale '5' means that the resolution of the horizontal line is 500 It means that it is TV. As a method of designating a line for the user to perform edge detection, the user may designate the number of TV copies.

8 is an example of a screen for setting, by the user interface, a threshold value of luminance difference? That is, '20', which is a threshold value of the luminance difference Δ shown in the drawing, corresponds to a predetermined threshold used in step S20 of FIG. In step S20 of FIG. 7, an edge in which the luminance difference Δ is greater than or equal to -20 when the luminance between adjacent pixels tends to be decreased, and an edge in which the luminance difference Δ is +20 or more when the luminance between adjacent pixels is increased are detected in pairs. If the count is increased by one. 'Analysis' illustrated in FIG. 8 is an example in which a user inputs a desired number such as '20' and '300' to an input prompt of a threshold and an edge and presses the 'Analysis' key to perform a process.

9 and 10 are graphs showing edges detected by designating one line, and FIG. 9 is a graph showing edge changes of 300 TV lines, and FIG. 10 is shown of edge changes of 500 TV lines. One graph. At this time, the line for detecting the edge may be input by the user as shown in FIG. 8. '300' illustrated in FIG. 8 refers to the number of TV copies of a line for graphically displaying the detected edge as shown in FIG. 9 or FIG. 10. That is, as shown in Figure 9 it means that 300 TV lines will be shown as a graph. If the user inputs '500', it means that 500 TV main lines will be shown in a graph as shown in FIG.

11 is an example of a gray scale chart to be evaluated by the resolution evaluation apparatus according to the present invention.

The gamma value of the image can be measured by capturing an image of a gray scale chart evenly distributed with a digital camera and evaluating the luminance value. The gamma value measured as described above may be used to determine and correct a depth of color by comparing luminance values of an image of a color bar chart.

As described above, according to the resolution evaluation apparatus of the digital camera according to the present invention, it is possible to evaluate the objective resolution of the digital imaging apparatus digitally transmitted by a high speed serial communication standard such as IEEE1394. In particular, in performing a performance evaluation, an adjustment process, and a quality assurance process of the digital imaging apparatus at a research or manufacturing site, resolution evaluation can be easily performed.

The present invention is not limited to what has been described above and illustrated in the drawings, and more modifications and variations are possible to those skilled in the art within the scope of the following claims. In particular, in the above-described embodiment has been described mainly on the evaluation of the resolution of the digital camera, in addition, the resolution evaluation apparatus according to the present invention is photographed by a digital camera, such as color depth correction by gamma value evaluation received by a high speed serial communication standard Of course it can be used as a whole to analyze the digital image.

Claims (5)

An apparatus for evaluating the resolution of the digital camera by processing digital image data received by a high speed serial communication standard from the digital camera, An image data capture unit for capturing and outputting the received digital image data; An image data storage unit for storing the captured and output digital image data; An image processor extracting RGB color data for each pixel from the captured digital image data, and converting the RGB color data to obtain luminance data for each pixel; A graph implementer configured to graph a luminance value using the luminance data of each pixel; And A high speed serial communication interface including an image capturing control unit configured to adjust a focus of an image by driving a focus lens for capturing an image of the digital camera, to capture an image while the focus is adjusted, and to white balance the captured image. Resolution evaluation device of the digital camera connected by. The method of claim 1, wherein the image data capture unit, And a digital camera configured to capture the received digital image data, convert the digital image data into a Windows bitmap format, and output the converted digital image data. The method of claim 1, wherein the graph implementer, High-speed serial communication characterized in that the pixel position of the captured image is mapped one-to-one to the horizontal x coordinate and the vertical y coordinate, and the magnitude of the luminance data is displayed on the z coordinate to implement a three-dimensional graph. Device for evaluating the resolution of digital cameras connected by an interface. The method of claim 1, wherein the graph implementer, The pixel position of the captured image is mapped one-to-one to the horizontal x coordinate and the y coordinate in the vertical direction, and the edge is displayed on the z axis when the luminance difference between pixels adjacent in the horizontal or vertical direction is larger than a predetermined threshold. Apparatus for evaluating the resolution of a digital camera connected by a high speed serial communication interface, characterized in that the three-dimensional graph for detecting the. The method of claim 1, wherein the graph implementer, A pixel position corresponding to a horizontal or vertical line of the captured image is mapped one-to-one to an x coordinate, and the edge is detected by displaying a case where the luminance difference between adjacent pixels on the line is larger than a predetermined threshold on the y axis. Apparatus for evaluating the resolution of a digital camera connected by a high speed serial communication interface, characterized in that a two-dimensional graph is implemented.

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