JP4766783B2 - Image processing apparatus and image processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
For example, the present invention appropriately performs an automatic resolution measurement in an oblique direction by rotating an image obtained by capturing a wedge chart without performing pixel information generation for interpolation on an information absent grid point by 45 degrees. The present invention relates to a possible image processing apparatus and image processing method.
[0002]
[Prior art]
In recent years, a subject image is imaged on a solid-state image sensor such as a CCD two-dimensional image sensor by an imaging optical system and converted into an electric signal, and still image data obtained thereby is recorded as in a semiconductor memory or a magnetic disk. So-called electronic cameras that record on a medium are becoming widespread.
[0003]
In addition, the resolution of an image captured by this type of electronic camera is conventionally determined by visual inspection of a skilled inspector. FIG. 9 is a typical ISO12233 Resolution chart used for visual measurement of this resolution. An inspector takes a picture of the chart with a camera to be examined, and visually views, for example, a wedge chart a in the photographed chart image. Measure its resolution.
[0004]
The wedge chart a is composed of line segments of the same width of 5 blacks and 4 whites, and the person inspecting observes the wedge chart a as a subject image from the upper end toward the lower end. More specifically, the resolution state of this black and white line is examined, a limit line (row) in which the line number and the actual line number continue to match is detected, and the resolution indicated by the detected line is set to the left side. Read by the scale attached to. That is, if this wedge chart a is used, the resolution in an oblique 45 degree direction can be measured.
[0005]
However, in this way, when the resolution of the image captured by the camera to be examined is visually measured, the measurement result depends on the characteristics of the image output device used for the measurement, and errors due to individual differences and circumstances are extremely large. Another problem with amplitude is that it is difficult to avoid the influence of moire.
[0006]
[Problems to be solved by the invention]
For this reason, the present inventor newly devised a method for automatically measuring the resolution by directly analyzing the data value of the wedge image captured by the camera under test, and the patent on the same day as the present invention. The technical disclosure was attempted in the application. The analysis of resolution in this new automatic resolution measurement assumes a normal image captured by an electronic camera or the like, and is assumed to be a horizontal and vertical orthogonal lattice image, that is, an image in which each pixel is distributed at orthogonal lattice points. To be done. (In many cases, a “square lattice” having the same horizontal and vertical intervals is used among the orthogonal lattices. This is also assumed in the following description for the sake of simplicity.)
Specifically, for example, in the case of measuring the horizontal resolution, photographing is performed with the wedge direction aligned with the vertical direction (sub-scanning direction), and sequentially from the upper part (low frequency end) to the lower part (high frequency end) of the wedge. This is done by examining the resolution of black and white lines for each horizontal line (line) and detecting the limit line (frequency) where the number of lines and the number of lines of the subject wedge continue to match as the resolution limit. Is done. At that time, the number of white or black lines, which is the resolution state of the black and white lines for each horizontal line (line), is the pixel along that line, that is, in the horizontal direction (direction perpendicular to the wedge direction: main scanning direction). It is obtained by scanning data and analyzing the increase or decrease of the data to obtain the number of local maximum or local minimum values.
[0007]
In the case of measuring the vertical resolution, the direction of the wedge at the time of photographing should be aligned with the horizontal direction, and in the above analysis, the horizontal / vertical scanning (ie, the main scanning direction and the sub-scanning direction) may be reversed. Of course, in practice, the scan is not switched, but the image data to be evaluated is rotated 90 degrees (that is, the horizontal and vertical coordinates of the image are switched), and then the same analysis as above is applied. The “rotation method” is more convenient and preferable. In other words, by finally aligning the wedge direction with the sub-scanning direction at the time of data analysis, it is possible to obtain a measured value having the same physical meaning as “resolution”. Here, such measurement of resolution is referred to as “basic measurement”. By the way, the automatic measurement of resolution by this basic measurement method can be applied in the direction along the pixel arrangement, that is, in the horizontal and vertical directions, but it is difficult to apply in the oblique direction as in the wedge chart a in FIG. There was a problem that there was. This problem will be described with reference to FIGS.
[0008]
FIG. 10 is a diagram for illustrating a situation of oblique resolution. FIG. 10A illustrates an example of low-frequency resolution in which a plurality of pixels correspond to each single black and white line width. ) Shows an example of high-frequency (near limit resolution) resolution in which one pixel corresponds to one monochrome line width. The line from the upper right to the lower left in the figure indicates the direction of the wedge.
[0009]
Now, following the above-mentioned basic measurement concept for such an oblique wedge image, firstly, the wedge direction (rather than the recording pixel arrangement direction) is used as a reference and is simply set in a direction perpendicular thereto. When considering main scanning, there is no particular problem with FIG. 10A, but it does not work with respect to FIG. 10B. For example, the black line is only black on the former line, and the white line is only on the second line, and the original (visually recognized) alternate black and white lines cannot be recognized. Also, even if such an oblique main scan measurement is possible by some device, another processing method different from the above basic measurement was used to evaluate the same “resolution”. Then, it is not preferable from the viewpoint of the reliability of the method and from the viewpoint of practical use.
[0010]
Therefore, secondly, by rotating the image of FIG. 10B by 45 degrees, the above basic measurement is applied, that is, by rotating the image, the direction of the wedge is made coincident with the direction of the pixel array, and data of the basic measurement is obtained. A case where the direction of the wedge is aligned with the sub-scanning direction at the time of analysis can be considered. However, at this time, if the image is simply rotated by 45 degrees, the same difficulty as in the above-described oblique scanning occurs, which does not work well.
[0011]
FIG. 11 shows pixels after virtual rotation, but pixel data originally exists only in (odd / odd) grid points such as ACEMOQ and (even / even) grid points such as HJLSUW. In order to make this analysis (automatic measurement) possible, it is necessary to put it on the orthogonal lattice points in some form. However, the (odd, odd) lattice points and the (even, even) lattice points are arranged in order. As shown in FIG. 12, only black lines (for example, ACE) and white only lines (for example, HJL) are obtained, and the original lines cannot be recognized. It will be.
[0012]
On the other hand, conventionally, in the case of 45 degree image rotation processing, the pixel data originally does not exist (odd / even) or (even / odd) lattice points as new pixels having the interpolation (average) values of the four adjacent pixels. It is customary to produce. Then, if such a interpolation process is applied to FIG. 11 to generate a square lattice pixel, all new generated pixels (BDFGIK...) Have a gray level that is an average value of white and black. According to the above extreme value detection, a black and white line can be detected. However, in terms of the amplitude of the black and white wave, it is clearly reduced to ½ of the original.
[0013]
That is, as shown in FIG. 13, there is a clear difference with respect to the measurement in the horizontal and vertical directions. In addition, these figures are only one specific case different from a live-action image, and in view of the fact that clearly different characteristics can be obtained with respect to such a specific example, an extremely wide variety of live-action images can be obtained. When applied, it cannot be denied that the extreme value (monochrome line) detection may be affected. In fact, the response is often very small near the limit resolution. Therefore, if the black-and-white difference (amplitude) before interpolation has a minimum value of 1 (= digital quantization level), the gray level is Since the data is cut off at the time of calculation and the so-called bit drop occurs and the same data as black is obtained, it is impossible to detect the black and white line.
[0014]
In other words, the existence of such a difference in the end means that the final “measured resolution” can be said to be based on the same physical basis as that measured in the horizontal or vertical direction, or visual recognition. It is very suspicious about whether or not the response can be expected, and it cannot be adopted at all.
[0015]
The present invention has been made in consideration of such circumstances, for example, by rotating an image obtained by capturing a wedge chart by 45 degrees without generating pixel information for interpolation with respect to an information absent grid point. An object of the present invention is to provide an image processing apparatus and an image processing method capable of appropriately executing an automatic resolution measurement in an oblique direction.
[0017]
[Means for Solving the Problems]
In order to achieve the above-described object, an image processing apparatus according to the present invention is an image obtained by capturing a wedge chart used for visual measurement of resolution, and the direction of the wedge is determined by the pixel array grid of the image data. An image processing apparatus for inputting an image captured by tilting 45 degrees with respect to a two-dimensional array direction and generating an image obtained by rotating the input image by 45 degrees, wherein the input image is converted into a wedge direction. Are rotated so as to coincide with the vertical direction which is the sub-scanning direction at the time of resolution measurement, and at this time, two pixels having the pixel value for each pixel of the input image are arranged in the direction of the wedge after rotation. it characterized by comprising an image generating means for generating images that are adjacent.
[0018]
In this image processing apparatus, when a so-called wedge chart used for visually observing the resolution is tilted by 45 degrees and an image picked up is rotated by -45 degrees to generate an image for measurement, each pixel of the original image On the other hand, only the rearrangement of the original pixel information is performed such that two of them are arranged in the continuous direction of the wedges. That is, a new image for measurement is generated without using new pixel information by interpolation using a plurality of pieces of pixel information.
[0019]
This makes it possible to appropriately execute automatic measurement with high reproducibility and in principle excellent resolution by analysis focusing on the continuity of the chart lines even in the direction of 45 degrees obliquely.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings.
[0021]
FIG. 1 is a block diagram showing a configuration of an electronic camera that captures an image processed by an image processing system according to an embodiment of the present invention.
[0022]
In the figure, 101 is an imaging lens system composed of various lenses, 102 is a lens driving mechanism for driving the lens system 101, 103 is an exposure control mechanism for controlling the aperture and shutter device of the lens system 101, 104 is a low-pass Infrared cut filter, 105 a CCD color image pickup device for photoelectrically converting a subject image, 106 a CCD driver for driving the image pickup device 105, 107 a preprocess circuit including an A / D converter, 108 Denotes a digital process circuit for performing various digital arithmetic processing such as γ conversion, 109 denotes a card interface, 110 denotes a memory card, and 111 denotes an LCD image display system. In the figure, 112 is a system controller for comprehensively controlling each part, 113 is an operation switch system composed of various SWs, 114 is an operation display system for displaying an operation state and a mode state, and 115 is a light emitting means. , 116 is a lens driver for controlling the lens driving mechanism 102, 117 is an exposure control driver for controlling the exposure control mechanism 103 and the strobe 115, and 118 is a nonvolatile memory for storing various setting information. (EEPROM).
[0023]
On the other hand, FIG. 2 is a block diagram showing a configuration of a personal computer on which the image processing system according to the embodiment of the present invention operates.
[0024]
In the figure, 201 is a CPU for overall control of each part, 202 is a system memory serving as the main memory of the computer, 203 is a magnetic disk device serving as an external storage of the computer, and 204 is a user interface output in the computer. , A display controller 205 that controls the user interface, a keyboard controller that controls input of a user interface in the computer, 206 a card interface, and 207 a memory card. Further, the display controller 204 controls display of the display data created by the CPU 201 on the CRT 204a and LCD 204b, and the keyboard controller 205 transmits the operation of the keyboard 205a and mouse 205b to the CPU 201. The image processing system is configured as a program that is loaded from the magnetic disk device 203 to the system memory 202 and executed by the CPU 201.
[0025]
Next, the basic principle of image processing (image rotation) executed by the image processing system will be described. FIG. 3 is a main flow of image processing in this image processing system.
[0026]
First, the person inspecting the image captures, for example, a chart shown in FIG. 4 using an electronic camera which is a camera to be inspected. The photographed chart image is stored in the memory card 110. The inspector takes the chart image by removing the memory card 110 from the electronic camera and reinserting it into the personal computer as the memory card 207. The data is taken into the personal computer (step S1).
[0027]
Note that the transfer of images from the electronic camera to the personal computer does not necessarily involve a memory card. For example, if both have a communication function for transmitting and receiving data, the communication function may be used.
[0028]
The chart shown in FIG. 4 is an ISO12233 Resolution chart, which is a representative chart used for visual measurement of resolution. In this image processing system, the rectangular area b including the wedge chart is cut out from the chart image (step S2). FIG. 5 is a diagram illustrating an example of a rectangular image cut out at this time. This image corresponds to FIG. 10 described above.
[0029]
This rectangular area is cut out when the person in charge of inspection designates the start point and the end point with the mouse 205b at desired positions on the chart image displayed on the CRT 204a or the LCD 204b. The image processing system virtually draws a horizontal line and a vertical line that pass through the specified start point and end point, and executes a cut-out as a rectangular area that is surrounded by the virtually drawn lines. To do.
[0030]
Next, the image processing system executes rotation of the cut image by the following calculation (step S3). Here, first, the rotation of this image 45 degrees to the left will be described.
[0031]
First, when the original coordinates are (i, j) (where the existence range of the cut-out image is 0 ≦ i ≦ Lx, 0 ≦ j ≦ Ly) and the generated coordinates are (I, J), the original image For all the pixels of X, two points of XData (I, J) and XData (I, J + 1) with respect to the original pixel data value XData (i, j) of each point (where I = i + j, J = Lx) -I + j). FIG. 6 is a representation of this in the programming language BASIC (the array that stores the data of the generated image is Y).
[0032]
The target signal is a luminance signal or an RGB component signal, and the above calculation is applied to the component signal for each color as it is in the case of the luminance signal.
[0033]
In the case of right rotation, the above-mentioned “I = i + j, J = Lx−i + j” may be replaced with “I = Ly + i−j, J = i + j”.
[0034]
When such processing is performed, as shown in FIG. 7, the black and white lines (wavefronts) to be recognized in the wedge direction maintain their original amplitude without losing continuity in the wedge direction. Therefore, the limit resolution measured by this is equivalent to the vertical and horizontal resolutions measured by the basic measurement method. FIG. 8 shows an image obtained by rotating the image of FIG. 5 45 degrees to the left by this processing (an image generated by the rotation).
[0035]
Next, this image processing system cuts out a predetermined rectangle from the image obtained thereby (step S4). This cutout is executed in the same procedure as in step S2. Then, this image processing system sends the cut out image to the basic measurement processing unit together with a value PHt = √2 × PHt obtained by correcting the vertical pixel number (image height) data PHt of the chart photographed image file, The resolution measurement of the clipped image is executed (step S5). Instead of sending the corrected PHt, the original PHt and the correction flag may be sent together, and the value may be corrected by the basic measurement processing unit. The reason why correction is necessary at this time is that, in the basic measurement process, the shooting magnification of the chart is determined by the number of vertical pixels (image height) of the captured image file and the number of pixels corresponding to the total length (vertical length) of the wedge. Regarding the calculation by the ratio and the calculation of the number of resolutions,
(1) The wedge was tilted 45 degrees.
[0036]
(2) Two vertical pixels are generated from one original pixel during the rotation process.
[0037]
The overall result is that the number of pixels corresponding to the entire length of the rust is √2 times (← cos 45 degrees) as compared with the horizontal and vertical measurement.
[0038]
As described above, it becomes possible to measure the limit resolution accurately and with high reproducibility even in a 45-degree oblique direction.
[0039]
Here, the wedge chart provided in the ISO12233 Resolution chart has been described as an example. However, the present invention is not limited to this. For example, the wedge chart provided in the EIAJ-A chart includes a linearly drawn band chart. Processing methods are applicable.
[0040]
Also, here, an example in which an image of a chart taken by an electronic camera is taken into a personal computer via a card and image processing is executed by the personal computer, that is, an example in which this image processing technique is realized on the personal computer. Although shown, it is not restricted to this, You may implement | achieve as a dedicated image processing apparatus. In addition, if this function is incorporated in the electronic camera itself, for example, when the electronic camera has a plurality of imaging modes with different resolutions, these can be measured individually, or at the time of manufacture or repair (for example, optical system or automatic Performance tests (including focusing systems) can be performed very easily.
[0041]
That is, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention in the implementation stage. Further, 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 requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be obtained as an invention.
[0042]
【The invention's effect】
As described above in detail, according to the present invention, when a so-called wedge chart used for visually observing the resolution is tilted by 45 degrees, an image captured by rotating the image by −45 degrees is generated. In addition, only rearrangement of the original pixel information is performed such that two pixels are arranged in the continuous direction of the wedges for each pixel of the original image. That is, a new image for measurement is generated without using new pixel information by interpolation using a plurality of pieces of pixel information.
[0043]
This makes it possible to appropriately execute automatic measurement with high reproducibility and in principle excellent resolution by analysis focusing on the continuity of the chart lines even in the direction of 45 degrees obliquely.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an electronic camera that captures an image processed by an image processing system according to an embodiment of the present invention.
FIG. 2 is an exemplary block diagram showing the configuration of a personal computer on which the image processing system according to the embodiment operates.
FIG. 3 is a main flow of image processing in the image processing system of the embodiment.
FIG. 4 is a view showing an ISO12233Resolution chart used in the image processing system of the embodiment.
5 is a diagram showing an example of a rectangular image cut out from the ISO 12233 Resolution chart of FIG. 4 by the image processing system of the embodiment.
FIG. 6 is a diagram representing image rotation executed by the image processing system according to the embodiment in the programming language BASIC.
FIG. 7 is a schematic diagram for explaining a pixel arrangement of a rotated image generated by the image processing system of the embodiment.
8 is a diagram illustrating a new image generated by rotating the image in FIG. 5 by the image processing system according to the embodiment;
FIG. 9 is a diagram showing a typical ISO12233 Resolution chart used for visual measurement of resolution.
FIG. 10 is a diagram for illustrating a situation of oblique resolution that has been difficult to apply to automatic resolution measurement.
FIG. 11 is a diagram showing a pixel array after virtual rotation.
FIG. 12 is a diagram showing a pixel arrangement when (odd, odd) lattice points and (even, even) lattice points are arranged in order on orthogonal lattice points.
FIG. 13 is a diagram showing a pixel arrangement when a pixel is generated as a new pixel having an interpolation (average) value of four adjacent pixels at a (odd, even) or (even, odd) lattice point that originally does not have pixel data.
[Explanation of symbols]
DESCRIPTION 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 ... Pre-process circuit 108 ... Digital process circuit 109 ... Card interface 110 ... Memory card 111 ... LCD image Display system 112 ... System controller 113 ... Operation switch system 114 ... Operation display system 115 ... Strobe 116 ... Lens driver 117 ... Exposure control mechanism 118 ... Non-volatile 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 (2)

An image in which a wedge chart used for visual measurement of the resolution is captured, and the image is input with the wedge direction tilted 45 degrees with respect to the two-dimensional array direction of the pixel array grid of the image data. An image processing apparatus for generating an image obtained by rotating the input image by 45 degrees,
The input image is rotated so that the direction of the wedge coincides with the vertical direction which is the sub-scanning direction at the time of resolution measurement, and at that time, the pixel having the pixel value is rotated for each pixel of the input image. the image processing apparatus characterized by comprising an image generating means for generating images which are adjacent one by two in the direction of the wedge. An image in which a wedge chart used for visual measurement of the resolution is captured, and the image is input with the wedge direction tilted 45 degrees with respect to the two-dimensional array direction of the pixel array grid of the image data. An image processing method for generating an image obtained by rotating the input image by 45 degrees,
The input image is rotated so that the direction of the wedge coincides with the vertical direction which is the sub-scanning direction at the time of resolution measurement, and at that time, the pixel having the pixel value is rotated for each pixel of the input image. image processing method characterized by generating the images that are adjacent two by two in the direction of the wedge.

Images