JP2003259400A - Instrument and method for measuring resolution, and image processing apparatus and processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically measure resolution on the basis of an image of a wedge chart imaged by an electronic camera. <P>SOLUTION: The resolution measuring instrument for automatically measuring the resolution of an image, segments a rectangular area image including the wedge chart from an image imaging the wedge chart used for visual measurement of the resolution, decides a ratio of a longitudinal size and a lateral size of the segmented rectangular area image (S501), applies no processing to the image when the image is longitudinally long, applies 90-degree rotation processing to the image when the image is laterally long (S503 to 505), analyzes the rectangular area image subjected to rotation control to decide a resolution critical row position of the wedge chart and calculates the critical resolution from the decided row position. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resolution measuring apparatus and a measuring method capable of automatically measuring the resolution of an image captured by, for example, an electronic camera, and further to an image processing apparatus and a processing method.

[0002]

2. Description of the Related Art In recent years, a subject image is formed on a solid-state image pickup device, for example, a CCD two-dimensional image sensor by an image pickup optical system and converted into an electric signal, and image pickup data of a still image obtained by this is converted into a semiconductor memory or a magnetic field. A so-called electronic camera that records on a recording medium such as a disc is becoming widespread.

Further, the measurement of the resolution of an image picked up by an electronic camera of this type has been conventionally performed by the visual inspection of a trained inspector. FIG. 13 shows a typical ISO 12233 Resol used for visual measurement of this resolution.
It is a motion chart, and the inspector (measuring person)
First, this chart is photographed by the camera to be inspected by matching the image pickup area frame of the camera with the image frame reference line indicated by the vertices of the triangular mark (white triangle or black triangle). Then, the inspector visually checks, for example, the wedge chart a in the photographed chart image to measure the resolution thereof.

The wedge chart a is composed of five black and four white line segments having the same width, and an inspector observes the wedge chart a as an object image from the upper end to the lower end. More specifically, the resolution situation of this black-and-white line was examined, the limit line (row) at which the situation of correct resolution continued was detected, and the resolution indicated by the detected line was added to the left side. Read by scale.

Conventionally, the performance including the optical system and the automatic focusing system has been tested by visual measurement of the resolution, for example, at the time of manufacturing or repair.

[0006]

However, if the resolution of the image taken by the camera to be inspected is visually measured,
There was a problem that the difference between individuals and the situation was extremely large. For example, not only the reading (judgment) error when observing a wedge chart, but in some cases before that, the chart is accurately compared with the image frame of the camera when the chart is imaged based on the image frame reference line. Since it is difficult to adjust to, an error has already occurred.

Although the problem of such a measurement error is extremely important in itself, the conventional measurement method also has another essential problem. That is, in order for the inspector to visually check, it is indispensable to perform output by an image output device (output device) such as a display such as a CRT or LCD or print output by a printer. It is affected by the type and performance of the output device.

For example, if an output device with a low resolution limit is used, it is obvious that the measured resolution value cannot exceed at least the limit value of the output device, but generally the frequency characteristic of the output device is not ideal. Strictly speaking, no matter what kind of good performance output device (believed to be) is used, the resolution measured at that time depends on the characteristics of the output device used for measurement (device dependent). However, there is no change, and only the image pickup device specified by the image data itself recorded by the image pickup device (=
It was not possible to measure marginal capabilities, which were independent of the characteristics of the output device: device-independent).

As an attempt to solve such a problem, a method of directly analyzing recorded image data without using an image output device has been proposed. These are (a) image data of a so-called frequency sweep image such as a multi-burst chart or CZP (circular zone plate) chart, and (b) an image of a black and white step image (also called a knife edge). The Fourier transform data of the data is used to obtain the spatial frequency response (amplitude-frequency characteristic) of the captured image, and the amplitude is a predetermined value (for example, 5% of DC amplitude or 10
%) Is used as the limit resolution, which is called the AR method in the case of (a) and the SFR method in the case of (b).

Although these are certainly device-independent measurements, since they focus on amplitude characteristics, they are strongly affected by false resolution due to aliasing distortion (moiré) that often occurs near the limit resolution, and they are essentially visually observed. It often gives a result that a numerical value that is not resolved at all is resolved, and it has a serious drawback that it cannot be effectively correlated with the evaluation result by the conventional wedge visual method.

Further, apart from the resolution measurement, in the case where the electronic camera performs mixed vertical / horizontal position mixed shooting, the user may convert the mixed vertical / horizontal data according to the subject in order to make it easier to see the shot image on the display. When printing such vertical / horizontal mixed data with a printer, it is necessary to align the orientations on the printing paper depending on the vertically or horizontally long image data, which is a troublesome operation.

The present invention has been made in consideration of such circumstances, and for example, the resolution of an image picked up by an electronic camera or the like is maintained while maintaining the correlation with the conventional wedge visual method, and an output device or measurement is performed. It is an object of the present invention to provide a resolution measuring device and a resolution measuring method that can perform automatic measurement without depending on a person and therefore with high reproducibility.

Further, the present invention is an image processing apparatus and an image capable of automatically aligning the orientation on a printing paper when mixed vertical / horizontal positions are photographed by an electronic camera and when the vertical / horizontal mixed data is matched to the subject. It is intended to provide a processing method.

[0014]

(Structure) In order to solve the above problems, the present invention adopts the following structure.

That is, according to the present invention, in a resolution measuring device for automatically measuring the resolution of an image, a wedge chart used for visually measuring the resolution is a rectangular area including the wedge chart from the imaged image. Image cropping means for cropping an image, image rotation control means for performing a predetermined rotation process on the image based on the aspect ratio of the rectangular area image cropped by the image cropping means, and rotation control by the image rotation control means. A rectangular area image is analyzed to determine a resolution limit row position of the wedge chart, and a resolution calculation unit that calculates a limit resolution from the determined row position is provided.

Further, according to the present invention, in a resolution measuring method for automatically measuring the resolution of an image, a wedge chart used for visually measuring the resolution is a rectangular area including the wedge chart in an imaged image. The rectangular image is subjected to a predetermined rotation process based on the vertical and horizontal ratios of the rectangular area, and then the rectangular image is analyzed to determine the resolution limit row position of the wedge chart, and the determined row position is determined. It is characterized in that the limit resolution is calculated from

The following are preferred embodiments of the present invention.

(1) The rotation control means performs a 90-degree rotation or non-rotation process on the rectangular area image so that the vertical / horizontal length relationship of the rectangular area image is always constant.

(2) The rotation control means converts the rectangular area image into 90
When rotating once, the left rotation or right rotation should be selected based on the image pattern of the rectangular area image.

Further, according to the present invention, in an image processing apparatus for aligning the vertical and horizontal magnitude relations of an image, an input means for inputting image data, a vertical / horizontal ratio of the image data input by the input means, or a processing target. It is characterized by comprising rotation control means for controlling rotation given to an image based on the ratio of the number of vertical and horizontal pixels of a rectangular image, and output means for outputting rotation-controlled image data. .
Here, the rotation control means is characterized by performing a 90-degree rotation process or a non-rotation process on the rectangular image so that the vertical / horizontal length relationship of the rectangular image is always constant.

The present invention also provides an image processing method for aligning the vertical and horizontal size relationships of an image, the step of inputting image data, the aspect ratio of the input image data, or the vertical and horizontal directions of a rectangular image to be processed. Based on the ratio of the number of pixels,
The method is characterized by including a step of controlling rotation applied to the image and a step of outputting rotation-controlled image data.

(Operation) According to the present invention, attention is paid to the continuity of the line segments forming a so-called wedge chart, which is used for visually observing the resolution, and for example, the limit position where the phase of the wedge chart is maintained is determined. By detecting, the resolution limit row position of the wedge chart is determined, and the limit resolution is calculated from the determined row position. As a result, resolution measurement with high reproducibility and theoretically excellent, which is not affected by individual differences or circumstances, is realized.

Here, when the apparatus of the present invention is configured to measure the horizontal resolution by using the wedge chart for horizontal resolution, in order to measure the vertical resolution, 90 images including the wedge chart for vertical resolution are used. It has to be rotated once, which makes it inconvenient. On the other hand, as in the present invention, by performing a predetermined rotation process on the rectangular area image cut out by the image cutting means based on the aspect ratio of the rectangular area image, a wedge chart in either the horizontal direction or the vertical direction can be obtained. However, the resolution can be measured. Therefore,
It is possible to improve usability without requiring the user to perform a rotating operation.

[0024]

DETAILED DESCRIPTION OF THE INVENTION The details of the present invention will be described below with reference to the illustrated embodiments.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
3 is a block diagram showing a configuration of an electronic camera which is a camera to be inspected of the resolution measuring system according to the exemplary embodiment. FIG.

In the figure, 101 is an image pickup lens system including various lenses, 102 is a lens drive mechanism for driving the lens system 101, 103 is an exposure control mechanism for controlling the diaphragm and shutter device of the lens system 101, and 104. Is a filter for low-pass and infrared cut, 105 is a CCD color image pickup device for photoelectrically converting a subject image, 106 is a CCD driver for driving the image pickup device 105, 107 is a pre-process including an A / D converter, etc. Reference numeral 108 is a circuit, 108 is a digital process circuit for performing various digital arithmetic processing including γ conversion, 109 is a card interface, 110 is a memory card, and 111 is an LCD image display system.

Further, in the figure, 112 is a system controller for integrally controlling each part, 113 is an operation switch system including various SWs, 114 is an operation display system for displaying an operation state and a mode state, 115 Is a strobe as a light emitting means, 116 is a lens driver for controlling the lens drive mechanism 102, and 117 is an exposure control mechanism 10.
3, an exposure control driver for controlling the flash unit 115 and the flash unit 115, and a non-volatile memory (EEPROM) 118 for storing various setting information.

On the other hand, FIG. 2 is a block diagram showing the configuration of a personal computer on which the resolution measuring system according to this embodiment operates.

In the figure, 201 is a CPU for centrally controlling each part, 202 is a system memory which is a main memory of this computer, 203 is a magnetic disk device which is an external memory of this computer, and 204 is a user of this computer. A display controller which controls the output of the interface, 205 a keyboard controller which controls the input of the user interface in this computer, 206 a card interface, 20
Reference numeral 7 indicates a memory card. The display controller 204 controls the display data created by the CPU 201 on the CRT 204a and the LCD 204b, and the keyboard controller 205 controls the keyboard 205a and the keyboard 205a.
The operation of the mouse 205b is transmitted to the CPU 201. The resolution measuring system is used in the magnetic disk device 20.
3 is loaded into the system memory 202 from the CPU 20
It is configured as a program executed by 1.

Next, the basic principle of automatic resolution measurement performed by this resolution measuring system will be described.

The inspector first uses the electronic camera, which is the camera to be inspected, to photograph the chart shown in FIG. 3, for example. The image of the photographed chart is the memory card 1
The inspection person removes the memory card 110 from the electronic camera and stores it in the memory card 207.
By reattaching the chart image to the personal computer, the chart image can be taken into the personal computer. It should be noted that the transfer of the image from the electronic camera to the personal computer does not necessarily involve the interposition of a memory card, and may be performed by the communication function if both have a communication function for transmitting and receiving data.

The chart shown in FIG.
33Resolution chart, which is a typical chart used for visual measurement of resolution. And
In this resolution measuring system, a rectangular area a (a1, a2) including a wedge chart is cut out from this chart image. The inspection person cuts out this rectangular area by the CRT.
It is executed by designating a start point and an end point with the mouse 205b at desired positions on the chart image displayed on the 204a or the LCD 204b. The resolution measurement system virtually draws a horizontal line and a vertical line that pass through the specified start point and end point, respectively, and cuts out a portion surrounded by the virtually drawn lines as a rectangular area. To do. FIG. 4 is a diagram showing an example of the rectangular image cut out in this way.

As shown in FIG. 4, in this wedge chart, 5 black and 4 black white bands having the same width are arranged in the horizontal direction. Therefore, if attention is paid to the brightness level only at a certain horizontal position (line), a rectangular wave having a predetermined spatial frequency is obtained. That is, in the vertical (vertical) direction, it can be regarded as a frequency sweep image in which the frequency of the rectangular wave continuously increases from top to bottom.

Supplementally, EIA which is a typical resolution measurement chart similar to the ISO12233 chart.
The JA chart has a hyperbolic function as a frequency sweep because the wedge band is drawn linearly, and is not a linear sweep. The ISO 12233 chart differs from the ISO 12233 chart in that the wedge band bends in a hyperbolic shape as shown in FIG. 4 in order to realize a linear sweep, but both are “wedges” applicable to the present invention.
Is.

It should be noted that it is customary to add a scale representing the corresponding frequency as shown in FIG. 4 because of the relationship conventionally used for visual judgment (sensory evaluation), but the present invention does not rely on visual inspection. This scale is not used because automatic measurement is performed by data analysis.

Here, the term "wedge direction" simply refers to the direction corresponding to the frequency sweep of the wedge (up and down (vertical) direction in FIG. 4). "Wedge length" shall mean the length of the wedge's range of presence in the direction of this wedge.

In the present embodiment, the limit resolution is calculated by analyzing the data of the wedge image taken by the camera to be inspected, but the pixel array of the image to be analyzed captured and recorded at that time is generally orthogonal. It is premised that they are arranged (horizontal, vertical), and images are taken in the same direction as in FIG. 4 (the wedge direction is vertical, and the frequency sweep is from top to bottom). That is, the spatial frequency at the resolution limit is obtained by performing the frequency sweep with the vertical direction as the sub-scanning direction while performing the above-described rectangular wave detection (detection of the number of lines) with the horizontal direction as the main scanning direction.

In the following description of the present embodiment, the recorded image to be analyzed is assumed to be a monochrome image. However, even if this is a color image, the luminance value is calculated from the color signal by a predetermined matrix operation. It may be calculated and used.

The specific procedure will be described below with reference to the flow charts shown in FIGS. 5 and 6 are main flows of resolution measurement in this resolution measurement system.

As described above, the pixel array of the chart image to be analyzed is a general orthogonal array (horizontal and vertical), and the chart image is in the wedge direction of the wedge chart (the direction corresponding to the frequency sweep of the wedge). ) Is taken vertically, and the frequency sweep is assumed to be imaged from top to bottom. In addition, here, the horizontal coordinate i is positive in the right direction and the vertical coordinate j is positive in the downward direction, and the number of vertical pixels of the chart image (entire recorded analysis target image) is PHt, which is cut out from this chart image. The numbers of horizontal and vertical pixels of the rectangular image are defined as Lx + 1 and Ly + 1, respectively. However, +1 is for convenience of using 0 as a coordinate.

Further, the magnification at the time of capturing an image of the chart as shown in FIG. 3 by using the camera to be inspected is irrespective of the image frame reference line provided for the purpose of the original visual measurement by the chart creator.
Any magnification may be used. Furthermore, the recorded image (captured image)
Therefore, when cutting out a predetermined rectangular area as shown in FIG. 4 as a measurement image, it is assumed that the topmost one (black line) of the scale images attached to the wedge is not included. .

First, the image data Y (i, j) of the rectangular image cut out as described above is read (step A1 in FIG. 5), and the wedge type (the number of black lines WCT: 5 or 9 in the case of this chart). And the total image height PHt are read (step A2). The wedge type (the number of WCTs) and the total image height PHt may be values preliminarily input by the inspector from the keyboard 205a.

Here, the wedge chart includes a wedge chart a1 for horizontal resolution measurement and a wedge chart a2 for vertical resolution measurement, but in the present embodiment, the wedge chart a1 for horizontal resolution measurement is processed as it is and vertically. The resolution measuring wedge chart a2 rotates 90 degrees. As a result, in both horizontal and vertical charts,
The same process enables resolution measurement.

Specifically, as shown in FIG. 7, first, the horizontal pixel number Lx and the vertical pixel number Ly of the rectangular image are compared (step S501). If Lx ≦ Ly, that is, if the cut out rectangle is vertically long (vertical / horizontal ≧ 1), it is the wedge chart a1 for horizontal resolution measurement, and therefore the process described below is performed without performing the rotation process. If Lx> Ly, that is, if the cut out rectangle is horizontally long (vertical / horizontal <1), it is a wedge chart a2 for measuring vertical resolution, and therefore a rotation process of 90 degrees is performed.

At this time, in order to determine whether to rotate left 90 degrees or right 90 degrees, the data average value LAv of the left half (L) and right half (R) of the rectangular area is determined prior to the rotation.
RAv is calculated (step S502). Then, the left half area data average value LAv and the right half area data average value RAv are compared (step S503). LAv ≦
If it is RAv, the left side has a lot of black, and therefore the process of rotating the right 90 degrees is performed (step S504). If LAv> RAv, the right side has a lot of black, the process of rotating the left 90 degrees (the right 270 degree rotation). Apply (step S505). Then, when the image is rotated, the number of pixels in the vertical and horizontal directions is exchanged by the parameter rotation, so that the values of Lx and Ly are exchanged and resetting is performed (step S506), and then the subsequent processing is performed.

Regarding the selection of the rotation direction (left and right), as a modified example other than the above example, for example, according to the specifications of the chart to be used, when the wedge type (the number of black lines) is designated to be 5, the clockwise rotation is performed. In the case of a book, counterclockwise rotation may be automatically selected.

Next, the background white level BWL and the background noise level NL are acquired (step A3 to step A in FIG. 5).
4). The background white level BWL is obtained by the overall average of the upper end row of the rectangular image, while the background noise level NL is the average deviation of the minimum three values of the upper end row of the rectangular image (for the minimum three values, the pixel value and the overall average). It is calculated from the difference (= “deviation”) from the value (= NL).

Then, when these data are gathered, the detection processing of the start line WSL of the wedge chart is executed (step A5). Figure 8 shows this wedge start line (W
It is a detailed flow of (SL) detection.

In this process, first, the threshold value ETH0 is set to 5 times the previously obtained background noise level (step B1 in FIG. 8). Then, from the upper end to the lower end, that is, while adding the vertical coordinate j one by one (step B
2) Until the vertical coordinate j reaches the maximum value (Y in step B3), the detection of the first line in which the black-side half amplitude obtained by the average deviation of the minimum three values exceeds the threshold value ETH0 is executed (step B4). .

If the vertical coordinate j reaches the maximum value without detecting the corresponding line (Y in step B3), a message "wedge cannot be detected" is recorded (step B5), and this processing is performed. To finish. On the other hand, when it is detected (Y in step B4), the vertical direction coordinate j is set to the wedge start line (WSL) (step B6), and this processing is ended.

When the wedge start line detection is completed,
A read determination start line D is obtained by adding a predetermined offset value (for example, 3) to the wedge start line WSL.
It is set as tSt (step A6 in FIG. 5). In addition, the threshold value ETH2 for both ends of the wedge chart and the threshold value E for the center
Initialize TH1 (steps A7 to A)
8). The threshold value ETH2 for both ends is set to 1/4 of the black half amplitude of the start row DtSt (obtained by the average deviation of the minimum three values), and the center threshold value ETH1 is also set to the same value as this threshold value ETH2. .

After initializing various parameters (step A9), black line detection in the horizontal direction, which is the main scanning direction in this resolution measurement, is executed (step A10 in FIG. 6). 9 to 11 are detailed flows of the black line detection.

In this process, the number BCT of black lines in the j-th row is set to 0 in step C1 of FIG. 9, and then the final (rightmost) black line is detected in steps C2 to C18. Then, step C19 to step C3 in FIG.
At 6, the 1st (leftmost) black line is detected. After detecting the final (right end) black line and the 1st (left end) black line, the general black line sandwiched between the two black lines is detected in steps C37 to C53 in FIG.

In the final (right end) black line detection, initialization such as setting reference values for wedge right end (decrease) detection and black line (increase) detection and setting the scanning start position on the right end side was performed. After that (step C2 to step C3 in FIG. 9), a decrease determination for detecting the wedge right end (step C4) and an increase determination for detecting the black line (step C5) are performed. If neither the right edge of the wedge nor the black line is detected (N in step C4, N in step C5), either the local minimum value LMn or the local maximum value LMx, which is the reference value for increase / decrease detection, is updated. (Steps C6 to C9), the value of the flag Z indicating the (significant) increase / decrease of the pixel value in that pixel (increase: 1, decrease: 0) is set to the value of the flag of the pixel on the right side (that is, the increase / decrease state is set). Maintain) (Step C1
0), after shifting the scanning position by one pixel to the left (step C12), the processing from step C4 is repeated. In addition,
At the initialization of step C2, the flag of the rightmost pixel is set to increase (1), so the value of this flag continues to increase (1) until the wedge right end is detected.

When the right edge of the wedge is detected (Y in step C4), the local minimum value L, which is the reference value for increasing / decreasing detection, is detected.
Mn and the local maximum value LMx are reset, and the value of the increase / decrease flag Z is set to decrease (0) (step C1).
4). Then, in order to improve the efficiency of the analysis on the next line one pixel below, the scanning start position is optimized (step C15), and then the scanning position is shifted by one pixel to the left (step C12). The processing from C4 is repeated.

On the other hand, when an increase is detected (step C5
Y), and the value of the increase / decrease flag Z is set to increase (1) (step C16). When this flag is set, it is recognized that the flag Z has changed from decrease (0) to increase (1), that is, the last (rightmost) black line has been detected, and this loop is exited (Y in step C11). ), 1 for black line number BCT
Is set and the position BEnd is registered (step C18), and the process moves to the detection of the next 1st (left end) black line.

If the scanning position reaches the left end without detecting the final (right end) black line (Y in step C13), a message "no black line" is recorded (step C17). This process ends.

In the 1st (left end) black line detection, initialization such as setting reference values for wedge left end (decrease) detection and black line (increase) detection and setting the scanning start position to the left end side was performed. After that (step C19 to step C20 in FIG. 10), the decrease determination for detecting the left edge of the wedge (step C21) and the increase determination for detecting the black line (step C22) are executed. If neither the wedge left end nor the black line is detected (N in step C21, N in step C22), the local minimum value LMn or the local maximum value that is the reference value for increase / decrease detection.
Any one of LMx is updated (step C23 to step C26), and the value of the increase / decrease flag Z of that pixel (increase: 1,
Decrease: 0) is set to the value of the flag of the pixel on the left side (that is, the increase / decrease state is maintained) (step C27), and the scanning position is set to 1
After shifting the pixel rightward (step C29), the processing from step C21 is repeated. Since the flag of the leftmost pixel is set to increase (1) in the initialization of step C19, the value of this flag continues to increase (1) until the wedge left end is detected. .

When the left edge of the wedge is detected (Y in step C21), the local minimum value LMn and the local maximum value LMx, which are the reference values for increase / decrease detection, are reset and the value of the increase / decrease flag Z is decreased ( 0) (step C)
31). Then, in order to improve the efficiency of the analysis on the next line under one pixel, the scanning start position is optimized (step C32), and then the scanning position is shifted by one pixel to the right (step C29). The processing from C21 is repeated.

On the other hand, when an increase is detected (step C2
2), local minimum value LMn which is a reference value for increase / decrease detection
And the local maximum value LMx are reset and the value of the increase / decrease flag Z is set to increase (1) (step C3).
3). When this flag is set, it is recognized that the flag Z has changed from decrease (0) to increase (1), that is, the 1st (left end) black line has been detected, and this loop is exited (Y in step C28). ), 2 is set to the number of black lines BCT, and the position BL (1, j) is registered (step C
34), and shifts to the detection of the next general black line.

It should be noted that while the 1st (left end) black line is not detected, the scanning position is at the right end (final black line position BE previously registered.
nd) (Y in step C30), the value of the final (rightmost) black line position BEnd is set to 1st.
(Left edge) Register at black line position BL (1, j) (step C
35), the message "only one black line" is recorded (step C36), and this processing ends.

In the general black line detection, the scanning at the time of detecting the 1st (left end) black line is succeeded, and the pixel on the right side is set as the scanning start position (step C37 in FIG. 11). The reduction determination (step C3) is performed by using the finally reset local minimum value LMn and local maximum value LMx.
8) and increase determination (step C39) are executed. If neither decrease nor increase is detected (N in step C38, N in step C39), the local minimum value LMn
Alternatively, the local maximum value LMx is updated (step C40 to step C43), and the increase / decrease flag Z of the pixel is updated.
Value (increase: 1, decrease: 0) is set to the value of the flag of the pixel next to the left (step C44), and the scanning position is shifted right by one pixel (step C46), and then step C38.
Repeat the process from.

When a decrease is detected (step C3
8), the local minimum value LMn and the local maximum value LMx are reset, and the value of the increase / decrease flag Z is set to decrease (0) (step C31). Then, the scanning position is shifted to the right by one pixel (step C46), and step C3
The processing from 8 is repeated.

On the other hand, when an increase is detected (step C3
9), the local minimum value LMn, and the local maximum value LMx are reset, and the value of the increase / decrease flag Z is set to increase (1) (step C33). When this flag is set, it is recognized that the flag Z has changed from decrease (0) to increase (1), that is, that a general black line has been detected, and this loop is once exited (Y in step C45), Its position BL
(BCT, j) is registered (step C50), and the number of black lines B
After adding 1 to CT (step C51), step C
The processing from 38 is repeated.

This general black line detection is repeated until the scanning position reaches the previously registered final (right end) black line position BEnd, and when it reaches (Y in step C47), this final (right end) black line position is reached. The value of BEnd is set to the black line position BL (BC
T, j) is registered (step C52), a message of "black line detection completed" is recorded (step C53), and this processing ends.

Upon completion of the above black line detection, the number of detected black lines BCT and the previously entered wedge type (number of WC
T) is checked for equality (step A1 in FIG. 6).
1), if equal (Y in step A11), the line ends at L
Check whether y has been reached (step A1)
2). If not reached (N in step A12), the row is updated (step A13), and the threshold values ETH2 for both ends of the wedge chart are reset to 1/4 of the current black side half amplitude (step A14). , Black line detection in step A10 is performed again. If it is reached (step A1)
(Y of 2), this loop is exited, the resolution limit row LML is set to the terminal Ly (step A15), an error of "no lower end in wedge" is displayed (step A16), and the processing from step A30 is started. To do.

On the other hand, when the numbers do not match (N in step A11), it is checked whether or not the central threshold value ETH1 is lowered to 0 (step A17). If it does not reach 0 (N in step A17), If the line is not the read determination start line DtSt (N in step A18), TH set to 1 in the initialization in step A9 in FIG.
After lowering the central threshold value ETH1 by the value variable step ETHS (step A19), the black line detection in step A10 is performed again. If that line is the read determination start line Dt
If it is St (Y in step A18), the process exits from this loop, displays an error of "initial number mismatch" (step A20), and ends this processing.

If the central threshold value ETH1 has reached 0 (Y in step A17), then it is checked whether the TH value varying step ETHS remains at the initial value 1, 1 (step A21). If so (Y in step A21), the resolution limit row LML is set to the row immediately before that row (step A22), and this TH value variable step ETHS is updated to 0 (step A23).

After that, at the time of detecting the black line immediately before (that is, in the line), it is checked whether or not the message "no black line" is recorded (step A24). If not, it is not recorded (N in step A24). If the row is not the terminal Ly (N in step A25), the threshold value ETH2 for both ends of the wedge chart is reset to 1/4 of the current black half amplitude (step A26), and the row is updated ( Step A2
7), black line detection in step A10 is performed again. If this line is the end Ly (Y in step A25), this loop is exited and an error "wedge lower end cannot be detected" is displayed (step A28). If the message "no black line" is recorded (Y in step A24), the wedge lower end row WEL is set to that row (step A29).

Then, after the final detection line is superimposed and drawn on the rectangular image including the wedge chart (step A3).
0), it is checked whether the wedge bottom row WEL is larger than the resolution limit row LML (step A31), and if it is larger (Y in step A31), the number of resolutions is calculated (step A32), and the value is displayed. (Step A33).
This number of resolutions is calculated by the following equation (1) when the number of wedge type WCTs is 5, for example.

[0071]

[Equation 1] If the number of wedge type WCT is 9, the following (2)
It is calculated by the formula.

[0072]

[Equation 2]

In these two equations, the numerator is detected based on the fact that each wedge chart is a so-called linear sweep chart in which the corresponding spatial frequency increases linearly from the upper end (low frequency end) to the lower end (high frequency end). Length of all wedges (total number of lines = WEL-WSL) and length from upper edge of wedge to limit resolution line (number of lines = LML-W)
This is an equation for calculating the corresponding frequency (the number of resolution lines) from the ratio with SL). However, the difference between the two formulas corresponds to the difference in the wedge sweep specifications.

The denominator is a term for correcting the photographing magnification, and the numerator is divided by the relative magnification compared to the original use condition of this Resolution chart. The relative magnification is the reference height of the entire chart (distance between image frame reference lines in the height direction = 20c
m) and wedge length (6 cm) ratio 10/3 is multiplied by the total length of the detected wedge (total number of rows = WEL-WSL) to obtain the chart reference height (corresponding pixel number) on the captured image data. , The total image height of this and the captured image (number of pixels)
Calculated as a ratio with PHt.

If the resolution limit row LML is within 3 rows from the wedge bottom row WEL (Y in step A34),
An error of "all resolution" is displayed (step A35), and this processing ends. The error within 3 lines is that the lower end of the wedge can be used in order to avoid this problem in consideration of the possibility that erroneous measurement may occur near the lower end line due to, for example, the influence of the vertical aperture. This is intended to limit the range to three lines less, and in this regard, the same effect as the offset value (JOFS) in step A6 is expected. Therefore, the value is not limited to 3.

On the other hand, the wedge bottom row WEL is the resolution limit row L.
If it is not larger than ML (N in step A31), since this is a state that cannot occur originally, an error of "unmeasurable" is displayed (step A36), and this processing ends.

The specific execution control of the measurement operation performed by the present resolution measurement system has been described above in detail. Further, in this, a supplementary explanation will be given regarding particularly important points in relation to the characteristics of the present system. To do.

(A) First, since the recorded image data of the camera is processed as it is (without using an output device), device-independent measurement can be performed.

(A) Since the same chart as that of the conventional wedge visual method is used and the same criterion is used in principle, the correlation with the wedge visual method can be secured. It is needless to say that the same numerical value is not always obtained in the visual method because the visual method is performed through the output device and the subjectivity of the evaluator is included.

Here, (a) will be described in detail. The above-mentioned control includes a point at which the same criterion as the principle of the visual determination is achieved. That is, (1) The determination rule for a person skilled in the art to make a visual determination is as follows: a) Seeing from the low frequency side, and "resolving" when the situation of continuous resolution continues, If there is any break, it will be non-resolution. b) Even if the image appears to be resolving at first glance, when black and white is inverted or a plurality of lines are connected, it is a false resolving power, so it is judged as non-resolving power.

That is, It is immediately apparent from the above control flow that the control of this resolution measuring system adopts (a), but regarding (b), an equivalent judgment is realized by focusing on the number of black and white lines. There is. That is, when false resolution occurs (black and white are reversed or a plurality of lines are connected), the number of lines always changes. For example, if a complete reversal (black-and-white reversal) occurs, the number of black lines in five wedges (five black lines) becomes four, and if one black spot connects two black lines to one. The number of black lines is reduced by one and it becomes four. On the contrary, if the original number of wedge lines is always maintained, phase inversion does not occur,
It should be regarded as a resolution in principle.

Therefore, the judgment criterion b) is judged to be resolution only when b ′) the number of visible (detectable) black and white lines and the number of original wedge lines match. Can be replaced with the equivalent criterion.

This resolution measuring system is a) + b ')
Since this is adopted as the judgment rule, it can be said that this is exactly the same standard as that used in the conventional visual judgment.

(2) In the process of visually recognizing a black and white line by a person, an extremely high degree of judgment is made even if the measurer is not aware of it. Specifically, first: ・ The high frequency region of the wedge (the region where the amplitude is small), especially in the vicinity of the critical resolution, the amplitude is extremely small, so the swell that is larger than the local amplitude of the brightness change corresponding to the black and white line (Effects are often added to the edges) or low-frequency luminance change that occurs in the entire wedge due to the effect of shading. For example, one black line value (luminance minimum value) is different from another white line value (luminance maximum). Value) is likely to occur. The human eye recognizes a black and white line in response to a slight local change, including the case where there is such a) waviness and shading.

It is possible to On the other hand, the human eye is able to distinguish b) the level change due to noise or the like and the wedge pattern without being confused with each other.

As a specific example, in the low frequency region of the wedge (region where the amplitude is large), a wavy waveform with a considerably large amplitude is generated near the black and white edge due to the frequency characteristic of the camera (often an edge enhancement process is added). The brightness change (ringing) is accompanied. This may be much larger than the amplitude (luminance change) of the wedge image near the limit resolution, but even in such a case, it is at least sufficiently smaller than the luminance amplitude of the low-frequency wedge image, so Ignores this correctly.

Further, other general noise (random noise or the like) is superimposed on the entire wedge image, but if this is also smaller than the amplitude (luminance change) of the wedge image at the relevant frequency, it is also ignored.

That is, a black and white line is correctly recognized by ignoring a relatively small change with respect to a change in luminance as a wedge image.

On the other hand, in the case of luminance data processing in mechanical automatic measurement, simple level detection and difference detection cannot detect black and white lines corresponding to such advanced recognition of human eyes.

In the present resolution measuring system, as described in the explanation of the above control, ◇ A black-and-white line is used as the maximum value and the minimum value by detecting the change in the brightness data for one line (only the black line is actually used). Therefore, only the decrease exceeding ETH1 from the local maximum value LMx or the increase exceeding ETH1 from the local minimum value LMn is detected as an effective increase / decrease. In other words, the extreme value determination is performed after the change is recognized when the cumulative change exceeds the threshold value ETH1.

Basically, this makes it possible to detect black and white lines as extreme values while eliminating the effects of noise and undulations.

The value of the threshold value ETH1 used for this determination is as follows. Since the threshold value ETH1 is reduced and the detection is repeated only when a predetermined number of lines cannot be detected due to the threshold value of, a) Even if swell or shading is present, a wave (black and white line) can be detected. , Finally (at the critical resolution frequency) E
Since the detection is performed at TH = 0, it is possible to detect even the luminance change in the state where the response becomes the minimum.

B) By adaptively eliminating the influence of noise in accordance with the degree of luminance change (response) of the image in each frequency region, only the wedge pattern can be detected over the entire frequency region.

In this respect as well, it is possible to make a judgment equivalent to the visual judgment, which could not be achieved in the conventional technique.

In the control flow, there are of course other processes that are adopted from the viewpoints of practical accuracy improvement and operation stabilization. For example: By performing from both sides according to a standard different from the above, it is possible to avoid being affected by ringing at both ends of the wedge, and to stably present the wedge as a single black line even in the high frequency part (blurred part) higher than the limit resolution. So that we can detect
No error occurs in the detection of the wedge lower end WEL. This ensures the wedge length detection system.

Setting of the threshold level ETH0 for detecting the wedge start line (WSL) and the threshold level ETH2 for detecting the black lines at both ends in each row (and the threshold level ETH for detecting the general black line)
The initial setting 1) is set based on the data distribution (specifically, the noise level and the black side half-amplitude) that also includes noise related to the pixels in the target area, so each detection should be performed very stably. You can

In general, when the wedge start line substantially extends over a plurality of lines due to a slight inclination of the wedge image, or the presence of vertical ringing caused by the vertical edge-enhanced image processing of the camera causes a malfunction. This may be caused, but this is avoided by adopting a read determination start row DtSt with a slight offset to the wedge start line WSL.

The above can be specifically pointed out.

Thus, this resolution measuring system
A rectangular wave is detected (the number of lines is detected) with the horizontal direction as the main scanning direction, and the spatial frequency at the resolution limit is obtained by performing frequency sweep with the vertical direction as the sub-scanning direction. That is, unlike the conventional method, the resolution is automatically measured without being affected by individual differences or situations. This result is provided in a form visible to the inspector, for example, by displaying the row position of the detected limit resolution on the wedge chart and displaying it, so that it is possible to increase the reliability of the automatically measured resolution. To do.

Further, as shown in the equations (1) and (2), the ratio of the wedge length (wedge bottom row WEL-wedge start row WSL) to the total image height PHt is calculated when the number of resolution lines is calculated. By taking this into consideration, it is not necessary to photograph the chart while being aware of the image frame reference line as in the conventional case.

Further, in this embodiment, since the wedge chart a1 for horizontal resolution measurement is automatically subjected to the 90-degree rotation processing for the wedge chart a2 for vertical resolution measurement, the rectangular image by the user is processed. It is possible to measure the resolution of any of the wedge charts in the horizontal direction and the vertical direction without the need for the rotation operation, and the usability can be improved.

In this case, ISO12233Res
Although the wedge chart provided in the solution chart has been described as an example, the resolution measuring method is not limited to this and is also applicable to, for example, a wedge chart in which a band is drawn linearly, which is provided in the EIAJ-A chart. It is possible.

Further, here, an example in which an image of a chart photographed by an electronic camera is taken into a personal computer via a card and the resolution is automatically measured by the personal computer, that is, this resolution measuring method is executed on the personal computer. However, the present invention is not limited to this, and may be realized as a dedicated resolution measuring device. In addition, if this function is incorporated into the electronic camera itself, for example, when the electronic camera has a plurality of imaging modes with different resolutions, these can be individually measured, or at the time of manufacturing or repair (for example, optical system or automatic Performance tests (including focusing system) can be performed extremely easily.

That is, the present invention is not limited to the above-described embodiment, and can be variously modified in the implementation stage within the scope of the invention. Furthermore, the embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, the problem described in the section of the problem to be solved by the invention can be solved, and the effect described in the section of the effect of the invention can be solved. If you get
A configuration in which this component is deleted can be extracted as an invention.

In addition to this, various embodiments can be considered. The image processing apparatus can be configured to be able to execute each step in the control shown in the above embodiment. That is, this device is a display (eg C) which is a general file interface (eg memory card slot) and GUI (graphical user interface) means.
RT and LCD) and input instruction device (eg keyboard,
The above steps may be sequentially executed by inputting an image obtained by shooting a predetermined wedge chart with a digital camera having a mouse) through a card.

Such an apparatus may be realized as a dedicated apparatus, but it is obvious that a general-purpose personal computer may be configured by incorporating a processing sequence capable of executing the above steps. Further, such a function may be incorporated in the digital camera device itself, and in this case, it is possible to perform the measurement without using the file interface. According to this, for example, when a camera has a plurality of imaging modes having different resolutions, these are individually measured, and a performance test (including an optical system and an automatic focusing system) at the time of manufacturing or repair is performed. Has the advantage that it can be done very easily.

(Second Embodiment) The image rotating mechanism of the present invention can be applied to other than the resolution measurement.
For example, there is a case where the electronic camera performs mixed vertical and horizontal position shooting, and when the vertical and horizontal mixed data matches the subject, the orientation is aligned with the printing paper.

Specifically, in the case where the image taken by the camera is taken in the hard disk of the personal computer and the image is stored, when the image is taken in from the camera, it is assumed that the data is input as the horizontal position (horizontally long image). Also, if the captured image contains a mixture of vertically oriented images, it is complicated to rotate each time the image is viewed. Therefore, the vertically oriented image should be rotated 90 degrees to be vertically oriented (vertical image). There are situations such as saving the data converted to. In such a situation, when trying to efficiently print a plurality of images continuously using a general-purpose printer, it is desirable to match the vertical and horizontal directions of the image with the orientation of the printing paper.
After all, it becomes necessary to align the orientations of all the images with the vertical position or the horizontal position. The present embodiment is extremely effective in such a case.

FIG. 12 shows the basic arrangement of an image processing apparatus according to the second embodiment of the present invention. In the figure, 301 is an input unit for inputting image data, 302 is a rotation processing unit that rotates an image based on the vertical / horizontal ratio of image data, or the ratio of the number of vertical / horizontal pixels of a rectangular image to be processed, and 303 is It is an output unit for outputting the rotation-controlled image data.

A rectangular image such as ABC is input to the input unit 301, and the rotation processing unit 302 determines whether the input image is vertically long or horizontally long. If it is horizontally long, it is rotated as it is, and if it is vertically long, it is rotated by 90 degrees. Apply processing. The judgment of this rotation processing is
This may be performed by comparing the number of horizontal pixels Lx and the number of vertical pixels Ly of the rectangular image as in step S501 shown in FIG. Then, the rotated rectangular image is output from the output unit 303.

With such a configuration, horizontally long images such as A and C are output as A'C 'in the state as they are,
A vertically long image such as B is converted into a horizontally long image B ′ and output. As a result, all output images are horizontally long. As described above, according to the present embodiment, it is possible to automatically align all the images in the vertical position or the horizontal position by determining whether the image is vertically long or horizontally long and rotating the image 90 degrees only in one case.
For the purpose like this example, the direction of 90 degree rotation (left and right)
Since it does not matter, it is possible to adopt, for example, a process of uniformly rotating 90 degrees right.

Here, the personal computer apparatus in which "the above processing method is additionally applied to a general-purpose image viewer software having a printing function to enable the following control" is installed, It is one embodiment of the present invention. In other words, if you select "with automatic rotation" as the print mode in advance, the image data for printing at the time of printing is automatically rotated as necessary, and unified to the vertical position or the horizontal position depending on the paper. However, it has an excellent effect that it is possible to improve printing efficiency with a very simple configuration. Although it is similar to this, the image rotation process is not performed on the data at the time of printing, but is performed on the image data itself to be saved (the rotated image is automatically overwritten or saved under a different name). ).

[0113]

As described above in detail, according to the present invention, attention is paid to the continuity of the line segments which form a so-called wedge chart used for visually observing the resolution, and for example, the phase of the wedge chart is maintained. By detecting the position of the limit to be determined, the resolution limit line position in the wedge chart is determined, and the limit resolution is calculated from the determined line position, so it is not affected by individual differences or situations. Achieve resolution measurement with high reproducibility and in principle. When the wedge chart is imaged and the resolution is automatically measured, the image rotation is automatically controlled by the aspect ratio of the manual area designation of the cutout of the target portion from the entire chart, which improves the workability of the measurement and shortens it. Efficient measurement can be performed in time.

Further, by automatically controlling the image rotation according to the aspect ratio of the image, for example, when mixed vertical / horizontal position data is taken by an electronic camera and then mixed with vertical / horizontal data, the print paper is printed. Since the directions can be automatically aligned, the usability for the user is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an electronic camera which is a camera to be inspected of a resolution measuring system according to a first embodiment.

FIG. 2 is an exemplary block diagram showing the configuration of a personal computer on which the resolution measurement system according to the embodiment operates.

FIG. 3 is an IS used in the resolution measurement system of the embodiment.
The figure which shows O12233 Resolution chart.

FIG. 4 is a view showing an example of a rectangular image cut out by the resolution measurement system of the same embodiment.

FIG. 5 is a diagram showing a first main flow of resolution measurement in the resolution measurement system of the embodiment.

FIG. 6 is a diagram showing a second main flow of resolution measurement in the resolution measurement system of the same embodiment.

FIG. 7 is a diagram showing a flow for explaining image rotation processing in the resolution measuring system of the embodiment.

FIG. 8 is a diagram showing a detailed flow of wedge start line (WSL) detection in the resolution measurement system of the embodiment.

FIG. 9 is a view showing a first detailed flow of black line detection in the resolution measurement system of the embodiment.

FIG. 10 is a diagram showing a second detailed flow of black line detection in the resolution measuring system of the embodiment.

FIG. 11 is a diagram showing a third detailed flow of black line detection in the resolution measuring system of the embodiment.

FIG. 12 is a block diagram showing a basic configuration of an image processing apparatus according to a second embodiment.

FIG. 13: Typical IS used for visual measurement of resolution
The figure which shows O12233 Resolution chart.

[Explanation of symbols] 101 ... Lens system 102 ... Lens drive mechanism 103 ... Exposure control mechanism 104 ... Filter system 105 ... CCD color image sensor 106 ... CCD driver 107 ... Preprocess circuit 108 ... Digital process circuit 109 ... Card interface 110 ... Memory card 111 ... LCD image display system 112 ... System controller (CPU) 113 ... Operation switch system 114 ... Operation display system 115 ... Strobe 116 ... Lens driver 117 ... Exposure control mechanism 118 ... Nonvolatile memory (EEPROM) 201 ... CPU 202 ... System memory 203 ... Magnetic disk device 204 ... Display controller 204a ... CRT 204b ... LCD 205 ... Keyboard controller 205a ... keyboard 205b ... mouse

Claims (10)

[Claims] 1. An image cropping means for cropping a rectangular area image including the wedge chart from an image of a wedge chart used for visually measuring the resolution, and a rectangular area image cropped by the image cropping means. Image rotation control means for performing a predetermined rotation process on the image based on the aspect ratio of the image, and a rectangular area image rotation-controlled by the image rotation control means is analyzed to determine the resolution limit row position of the wedge chart. And a resolution calculation unit that calculates a limit resolution from the determined row position. 2. The image rotation control means performs a 90-degree rotation or non-rotation process on the rectangular area image so that the vertical / horizontal relationship of the rectangular area image is always constant. The resolution measuring device according to claim 1. 3. The image rotation control means, when rotating the rectangular area image by 90 degrees, selects left rotation or right rotation based on an image pattern of the rectangular area image. The resolution measuring device according to claim 2. 4. A rectangular area image including the wedge chart is cut out from an image in which a wedge chart used for visually measuring the resolution is cut out, and the rectangular area image is based on the aspect ratio of the rectangular area image. After performing a predetermined rotation processing on, the resolution measuring method characterized by analyzing the rectangular area image to determine the resolution limit row position of the wedge chart, and calculating the limit resolution from the determined row position. . 5. The resolution measuring method according to claim 4, wherein the rectangular area image is subjected to 90-degree rotation processing or non-rotation processing so that the vertical / horizontal length relationship of the rectangular area image is always constant. . 6. The resolution measuring method according to claim 5, wherein when the rectangular area image is rotated 90 degrees, left rotation or right rotation is selected based on an image pattern of the rectangular area image. 7. Input means for inputting image data, image rotation control means for controlling rotation given to the image based on the aspect ratio of the image data input by said input means, said rotation control An image processing apparatus comprising: an output unit that outputs the generated image data. 8. An input unit for inputting image data, and a rotation applied to the rectangular image based on a ratio of vertical and horizontal pixel numbers of a rectangular image to be processed in the image data input by the input unit. An image processing apparatus, comprising: an image rotation control unit that controls the image rotation control unit; and an output unit that outputs the rotation-controlled image data. 9. A step of inputting image data, a step of controlling a rotation given to the image based on a vertical and horizontal ratio of the input image data, and a step of outputting the rotation-controlled image data. An image processing method comprising: 10. The step of inputting image data, and controlling the rotation applied to the rectangular image based on the ratio of the number of vertical and horizontal pixels of the rectangular image to be processed in the vertical and horizontal directions of the input image data An image processing method comprising: a step; and a step of outputting rotation-controlled image data.