JP2008141229A - Lens performance evaluation apparatus and lens evaluation performance method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens performance evaluating device and a lens performance evaluation method for evaluating lens performance appropriately by removing the effect of deterioration in luminance amplitude automatically. <P>SOLUTION: The lens performance evaluating device extracts a predetermined number of pieces of luminance amplitude from pieces (A', C') of larger luminance amplitude sequentially to evaluate the lens performance appropriately by removing the influence of the deterioration in the luminance amplitude, and averages the predetermined number of pieces of luminance amplitude to evaluate the lens performance. A portion B', where the luminance amplitude has not deteriorated, is not used, thus evaluating the lens performance appropriately. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a lens performance evaluation apparatus and a lens performance evaluation method for evaluating the lens performance of a photographic lens provided in an imaging apparatus.

  There is a lens performance evaluation device that forms an image of a test chart on an image sensor with a photographic lens, generates image data representing the test chart, and evaluates the performance of the photographic lens based on the generated image data (see, for example, Patent Document 1). .

  This Patent Document 1 includes black and white stripes extending in a predetermined first direction and arranged in a second direction perpendicular to the first direction, and the pitch of the black and white stripes is different in the second direction. A photographing lens is prepared by preparing a test chart having a wedge-shaped test pattern and measuring the luminance amplitude on the image data in each of a plurality of scanning lines arranged in the first direction by photographing the test chart. Techniques have been proposed for automatically measuring the critical resolution, which is a performance evaluation value.

  By the way, when photographing a test chart, if the positional relationship between the arrangement of stripes on the test chart and the arrangement of a large number of light receiving elements constituting the imaging device included in the photographing apparatus is broken, the luminance amplitude may not be measured correctly. is there.

  FIG. 1 is a diagram showing a configuration of a lens performance evaluation apparatus that evaluates lens performance based on image data representing a test chart photographed by a photographing apparatus. FIG. 2 shows the lens performance evaluation apparatus that evaluates lens performance. It is a figure which shows the luminance amplitude detected based on the image data which a test chart represents when performing.

  FIG. 2A shows the luminance amplitude when a correct positional relationship is obtained between the arrangement of the stripes on the test chart 10 and the arrangement of a large number of light receiving elements included in the imaging device included in the imaging device 11. FIG. 2B shows a case where a correct positional relationship is not obtained between the arrangement of the stripes on the test chart 10 and the arrangement of a large number of light receiving elements constituting the imaging element included in the imaging device 11. The luminance amplitude is shown. In the figure, an array of black and white stripes is shown next to the item name “block”, and an array of light receiving elements constituting the image sensor is shown next to the item name “pixel”. The luminance amplitude is shown next to the item name.

  The configuration of the lens performance evaluation apparatus will be described with reference to FIG.

  FIG. 1 shows a test chart 10 that constitutes a lens performance evaluation apparatus, an imaging apparatus 11 that is an object to be inspected, and a personal computer 12.

  As shown in FIG. 1, image data representing an image obtained by photographing a test chart 10 by a photographing device 11 which is an object to be inspected is supplied to a personal computer (hereinafter referred to as a PC) 12, and the photographing device 11 is provided in the PC 12. The performance of the taking lens is evaluated.

  As shown in FIG. 1, when the test chart 10 is captured with the imaging lens provided in the imaging apparatus 11, the arrangement of the black and white stripes on the test chart 10 includes a number of light receiving elements that constitute the imaging element included in the imaging apparatus 11. If there is an arrangement, the correct luminance amplitude can be obtained for each scanning line based on the image data obtained by photographing (see FIG. 2A).

  However, a position where two adjacent light receiving elements among the many light receiving elements constituting the imaging element overlap both the black and white of the stripe on the test chart 10 (in FIG. 2, the black line and the position where the pixel is not broken are described. If the luminance amplitude is detected on the PC 12 based on the image data, the luminance amplitude (gray, which is an intermediate color between black and white) is displayed as shown in FIG. Become smaller). This does not occur so much on the low frequency side of the spatial frequency, that is, where the stripe pitch (arrangement interval) is coarse, but it may occur more when the high frequency side, that is, the stripe pitch becomes fine.

  If the luminance amplitude shown in FIG. 2 (a) and the luminance amplitude shown in FIG. 2 (b) repeatedly appear every predetermined scanning line when a high-frequency test pattern on the test chart is captured, the luminance amplitude is The lens performance will vary, making it impossible to evaluate the lens performance.

  According to the technique of Patent Document 1, the PC sets the test chart and causes the PC to input the position of the test pattern in the test chart, so that the PC evaluates the lens performance based on the image data representing the test pattern. Although it is configured, the luminance amplitude shown in FIG. 2 (a) and the luminance amplitude shown in FIG. 2 (b) appear alternately when the pitch of the test pattern becomes fine.

  Further, when processing such as contour enhancement is performed on the photographing apparatus 11 side, or if there is a pixel defect in the image sensor provided in the photographing apparatus 11, the PC 12 is based on the image data supplied from the photographing apparatus 11 to the PC 12. When trying to evaluate lens performance, the brightness of the highlighted part appears larger than the other part, or the brightness of the pixel defect appears larger than the other part. An evaluation value as if it is high resolution (hereinafter referred to as false resolution) may be obtained. In addition, a high resolution part may be created in a part of the image by the image processing in the photographing apparatus 11, and in that case, an evaluation value as if the high resolution is apparently obtained. There is.

  Furthermore, since the test chart 10 is photographed by the photographing device 11 and the photographed image data is supplied to the PC 12 and the photographing lens included in the photographing device 11 is evaluated by the PC, the white balance changes depending on the state of the illumination light at the time of photographing. The evaluation value may vary due to a change in luminance amplitude on the image data.

Further, as described above using the technique of Patent Document 1, if the configuration is such that the operator inputs the position of the test pattern in the test chart, there is also a problem that the work for performing the evaluation becomes complicated.
JP 2003-009190 A

  In view of the above circumstances, the present invention is a lens performance evaluation apparatus in which the influence of false resolution and the influence of illumination light at the time of shooting is automatically removed and the lens performance is correctly evaluated, and the operator sets a test chart. After that, an object of the present invention is to provide a lens performance evaluation apparatus and a lens performance evaluation method in which lens performance is automatically evaluated.

A first lens performance evaluation apparatus of the present invention that achieves the above object is based on image data representing a test chart obtained by imaging a test chart on an image sensor with a photographing lens. In a lens performance evaluation device that evaluates performance,
The test chart has a test pattern consisting of black and white stripes extending in a predetermined first direction and arranged in a second direction perpendicular to the first direction,
Luminance amplitude measuring means for measuring the luminance amplitude on the image data in each of a plurality of scanning lines in which the test pattern is arranged in the first direction;
An average amplitude calculating unit is provided for detecting a predetermined number of luminance amplitudes in descending order of the luminance amplitude measured by the luminance amplitude measuring unit and averaging the predetermined number of luminance amplitudes.

  According to the first lens performance evaluation apparatus of the present invention, a predetermined number of luminance amplitudes are detected in descending order of luminance amplitude measured by the luminance amplitude measuring means, and the predetermined number of luminance amplitudes are averaged. The In the conventional lens performance evaluation apparatus, if what has been described with reference to FIG. 2 has occurred, the lens performance could not be properly evaluated. According to the first lens performance evaluation apparatus of the present invention, A predetermined number of luminance amplitudes are detected in order from the one with the largest luminance amplitude by the amplitude calculating means, and the predetermined number of luminance amplitudes are averaged to calculate the evaluation value resolution, so that each scanning line is spaced at a predetermined interval. Even if a decrease in luminance amplitude as shown in FIG. 2B is detected, the luminance amplitude of the scanning line where the decrease is detected is not used for calculation of the evaluation value.

  For this reason, even if the luminance amplitude shown in FIG. 2 (a) and the luminance amplitude shown in FIG. 2 (b) appear alternately, only the luminance amplitude representing the correct lens performance on the side of FIG. 2 (a) is extracted. The lens performance is evaluated correctly.

  As described above, a lens performance evaluation apparatus that automatically evaluates the lens performance automatically after setting the test chart is realized.

  Here, the average amplitude calculation means excludes scanning lines having a luminance amplitude exceeding a predetermined limit amplitude, extracts a predetermined number of luminance amplitudes from the measured luminance amplitude in descending order, and extracts the predetermined number of luminance amplitudes. It is preferable to average the luminance amplitude.

  As described above, when edge enhancement processing is performed on the imaging device side, or when there is a pixel defect in the image sensor provided in the imaging device, the luminance amplitude changes greatly regardless of the black and white stripes. Therefore, it is preferable to average a predetermined number of luminance amplitudes after excluding scanning lines having luminance amplitudes exceeding a predetermined limit amplitude.

Further, the second lens performance evaluation apparatus of the present invention that achieves the above object is based on image data representing a test chart obtained by imaging a test chart on an image sensor with a photographing lens. In a lens performance evaluation device that evaluates the performance of a lens,
In the test chart, a plurality of test patterns each having a position recognition marker are distributed, and one of the plurality of test patterns has a first test pattern marker of another test pattern. A first marker that is larger than the marker,
Storage means for storing relative positions of other markers from the first marker;
Marker position recognition that recognizes the position of the first marker based on the image data and recognizes the position of another marker based on the recognition position of the first marker and the relative position stored in the storage means Means,
Lens performance evaluation means for performing lens performance evaluation using a test pattern specified by the marker based on the marker position recognized by the marker position recognition means.

  According to the second lens performance evaluation apparatus of the present invention, the marker position recognizing unit recognizes the position of the first marker, and the first marker recognizing position and the relative stored in the storage unit. The position of another marker is recognized based on the position, and the lens performance is evaluated using the test pattern specified by the marker based on the marker position recognized by the marker position recognition means.

  Then, even if the operator does not input the position of the test pattern, the position of the test pattern on the test chart is specified by the marker position recognition means, and the measurement of the luminance amplitude by the test pattern specified by the marker is automatically performed. And it will be done in a short time.

  As described above, a lens performance evaluation apparatus is realized in which lens performance is automatically evaluated after an operator simply sets a test chart.

  Here, it is preferable that the plurality of test patterns have the same or similar shape on the test chart and are distributed in a plurality of directions.

  Some photographing apparatuses have a zoom lens as a photographing lens. In that case, the shooting angle of view of the test chart changes and the shooting range of the test chart changes.

  As described above, when the test pattern has the same or similar shape on the test chart and is distributed in a plurality of directions, the lens performance of the zoom lens is correctly evaluated.

Further, the third lens performance evaluation apparatus of the present invention that achieves the above object is based on image data representing the test chart obtained by imaging the test chart on the image sensor with the imaging lens. In the lens performance evaluation device that evaluates the performance of
The test chart has a test pattern consisting of black and white stripes extending in a predetermined first direction and arranged in a second direction perpendicular to the first direction,
Luminance value measuring means for measuring the luminance value on the image data at a plurality of scanning lines extending in the direction across the stripe of the test pattern;
Evaluation value calculating means for calculating an evaluation value correlated with the standard deviation of the luminance values at a plurality of points measured by the luminance value measuring means.

  As described above, when the contour enhancement processing is performed on the photographing apparatus side, an overshoot occurs in the edge portion of the luminance amplitude, and an evaluation value as if it is apparently high resolution may be obtained. is there. Further, when an image of the portion where the overshoot occurs is viewed, both sides of the portion where the overshoot occurs may appear blurred. In this case, it is problematic to determine that the resolution is high.

  Therefore, in the third lens performance evaluation apparatus of the present invention, the evaluation value calculation unit is improved so as to calculate an evaluation value correlated with the standard deviation of the luminance values at a plurality of points measured by the luminance value measurement unit. is doing.

  By improving in this way, for example, when there is a value far from the average when referring to the standard deviation, the influence of that value is suppressed and the evaluation value as the entire waveform is obtained, and the lens performance is evaluated. Since it is performed, more accurate evaluation will be performed.

  As described above, the lens performance evaluation apparatus is realized in which the influence of the false resolution is automatically removed and the lens performance is correctly evaluated.

Here, the evaluation value calculation means uses the average value of a plurality of brightness values measured by the brightness measurement means as a, the reference white level as b, the reference black level as c, and the brightness value. MAX is the maximum value that can be taken, MIN is the minimum value that can be taken as the brightness value, and d ₁ , d ₂ ,... , d _m, the average value greater luminance value than a of the luminance values of a plurality of points, deviation e ₁ from the average _{value, e} 2, _..., when the e _n,
Variable group _{(F × e 1, F ×} e 2, ..., F × e n, G × d 1, G × d 2, ..., G × d m)
However, F = (MAX−a) / (b−a)
G = (a-MIN) / (ac)
It is.
Is preferably calculated as the evaluation value.

  According to this calculation, the evaluation value can be obtained appropriately, and the lens performance can be evaluated appropriately.

The fourth lens performance evaluation apparatus of the present invention that achieves the above object is based on image data representing the test chart obtained by imaging the test chart on the image sensor with the photographing lens. In a lens performance evaluation device that evaluates performance,
The test chart has a gray patch,
White balance adjusting means for adjusting white balance based on the image data on the gray patch;
And lens performance evaluation means for evaluating the performance of the photographing lens based on the image data adjusted by the white balance adjustment means.

  As described above, depending on the illumination state when the test chart is photographed, the white balance may change and the luminance amplitude on the image data may change.

  Therefore, in the fourth lens performance evaluation apparatus of the present invention, a gray patch is provided on the test chart, and the white balance is adjusted by the white balance adjusting means based on the image data on the gray patch, and the white balance adjusting means is used. The configuration is such that the taking lens is evaluated based on the image data after adjusting the white balance.

  With such a configuration, the white balance is adjusted based on the image data on the gray patch, and the brightness value is calculated based on the image data after the white balance is adjusted. Performance evaluation will be performed correctly.

  As described above, a lens performance evaluation apparatus is realized in which the influence of illumination light at the time of shooting is automatically removed and the lens performance is correctly evaluated.

Here, the test chart is a lens performance evaluation test pattern and a pair of gray patches formed in a plurality of locations separated from each other,
The white balance adjusting means has lens performance based on each test pattern paired with each gray patch based on each image data in which white balance is adjusted based on each of the plurality of gray patches constituting the plurality of pairs. It is preferable to evaluate.

  With the above configuration, the white balance is adjusted based on the gray patch that forms a pair with the test pattern, and the luminance amplitude is detected from the test pattern based on the image data in which the white balance is adjusted, and the lens performance is evaluated.

  Then, since the luminance amplitude is accurately detected based on the image data after the white balance is adjusted based on the gray patch closest to the test pattern, the lens performance is evaluated more correctly.

The fifth lens performance evaluation apparatus of the present invention that achieves the above object is characterized by the performance of the photographic lens based on image data representing the test chart obtained by imaging the test chart on the image sensor with the photographic lens. In a lens performance evaluation apparatus for evaluating
The test chart includes a plurality of test patterns which are formed of black and white stripes extending in a predetermined first direction and arranged in a second direction perpendicular to the first direction, and the pitches of the black and white stripes are different. And
Luminance amplitude measuring means for measuring the luminance amplitude for each test pattern;
When the luminance amplitudes of the plurality of test patterns measured by the luminance amplitude measuring means are compared, the test pattern with a fine pitch has a luminance amplitude larger than the test pattern with a coarser pitch than the test pattern. Further, the image processing apparatus is characterized by comprising false resolution removing means for invalidating the luminance amplitude of the test pattern having a fine pitch.

  Empirically, it is known that the peak value of the luminance amplitude of the test pattern with a fine pitch is smaller than the peak value of the luminance amplitude of the test pattern with a coarse pitch.

  However, the image capturing apparatus shown in FIG. 1 has an image processing unit, and image processing is performed on the image data generated by the image pickup device by capturing the test chart with the image capturing lens included in the image capturing apparatus. Occasionally, the image processing may create an apparently high resolution portion in a part of the image. When this high resolution portion is detected by the luminance detecting means, a luminance amplitude having a large peak value is detected on the fine pitch side and erroneous evaluation is performed.

  Therefore, in the sixth lens performance evaluation apparatus of the present invention, the luminance amplitudes of the plurality of test patterns measured by the luminance amplitude measuring unit are measured by the false resolution removing unit so that the correct evaluation is performed. When the compared test pattern having a fine pitch has a luminance amplitude larger than that of the test pattern having a coarser pitch than the test pattern, processing for invalidating the luminance amplitude of the test pattern having a fine pitch is performed.

  As described above, the lens performance evaluation apparatus is realized in which the influence of the false resolution is automatically removed and the lens performance is correctly evaluated.

The first lens performance evaluation method of the present invention is as follows.
In a lens evaluation method for forming an image data representing a test chart by imaging a test chart on an imaging element with a photographing lens, and evaluating the performance of the photographing lens based on the image data,
The test chart has a test pattern consisting of black and white stripes extending in a predetermined first direction and arranged in a second direction perpendicular to the first direction,
An imaging step for generating image data in a state in which the arrangement direction of the light receiving elements constituting the imaging element is inclined with respect to the first direction;
A luminance amplitude measuring step for measuring the luminance amplitude on the image data in each scanning line extending in the second direction and extending in the second direction;
And an average amplitude calculating step of detecting a predetermined number of luminance amplitudes in descending order of the luminance amplitude measured in the luminance amplitude measuring step and averaging the predetermined number of luminance amplitudes.

  Here, the average amplitude calculating step excludes scanning lines having a luminance amplitude exceeding a predetermined limit amplitude, and extracts a predetermined number of luminance amplitudes in descending order from the measured luminance amplitude. It is preferable to average the luminance amplitude.

The second lens performance evaluation method of the present invention is as follows.
In a lens performance evaluation method for forming a test chart on an image sensor with a photographic lens and generating image data representing the test chart, and evaluating the performance of the photographic lens based on the image data,
In the test chart, a plurality of test patterns each having a position recognition marker are distributed, and one of the plurality of test patterns has a first test pattern marker of another test pattern. A first marker that is larger than the marker,
A storage step of storing relative positions of other markers from the first marker;
Marker position recognition that recognizes the position of the first marker based on the image data and recognizes the position of another marker based on the recognition position of the first marker and the relative position stored in the storage means Steps,
And a lens performance evaluation step for performing lens performance evaluation using a test pattern specified by the marker based on the marker position recognized in the marker position recognition step.

  Here, it is preferable that the plurality of test patterns have the same or similar shape on the test chart and are distributed in a plurality of directions.

The third lens performance evaluation method of the present invention is as follows.
In a lens performance evaluation method for imaging a test chart on an image sensor with a photographic lens to generate image data representing the test chart, and evaluating the performance of the photographic lens based on the image data,
The test chart has a test pattern consisting of black and white stripes extending in a predetermined first direction and arranged in a second direction perpendicular to the first direction,
A luminance value measuring step for measuring a luminance value on the image data at a plurality of scanning lines extending in a direction crossing the stripe in the test pattern;
An evaluation value calculating step of calculating an evaluation value correlated with the standard deviation of the luminance values at a plurality of points measured by the luminance value measuring means.

Here, in the evaluation value calculation step, an average value of a plurality of luminance values measured by the luminance measuring means is a, a standard white level is b, a standard black level is c, and a luminance value MAX is the maximum value that can be taken, MIN is the minimum value that can be taken as the brightness value, and d ₁ , d ₂ , ..., d _m, the average value greater luminance value than a of the luminance values of a plurality of points, the deviation from the average value e _{1, e} 2, _..., when the e _n,
Variable group _{(F × e 1, F ×} e 2, ..., F × e n, G × d 1, G × d 2, ..., G × d m)
However, F = (MAX−a) / (b−a)
G = (a-MIN) / (ac)
It is.
Is preferably calculated as the evaluation value.

In the fourth lens performance evaluation method of the present invention, a test chart is imaged on an image sensor with a photographic lens to generate image data representing the test chart, and the photographic lens of the photographic lens is generated based on the image data. In the lens performance evaluation method for evaluating performance,
The test chart has a gray patch,
A white balance adjustment step for adjusting white balance based on the image data on the gray patch;
And a lens performance evaluation step for evaluating the performance of the photographing lens based on the image data adjusted by the white balance adjustment step.

Here, the test chart is a lens performance evaluation test pattern and a pair of gray patches formed in a plurality of locations separated from each other,
In the white balance adjustment step, the lens performance based on each test pattern paired with each gray patch is determined based on each image data in which the white balance is adjusted based on each of the plurality of gray patches constituting the plurality of pairs. It is preferable that it is a step to evaluate.

In the fifth lens performance evaluation method of the present invention, a test chart is imaged on an image sensor with a photographing lens to generate image data representing the test chart, and the performance of the photographing lens is determined based on the image data. In the lens performance evaluation method to be evaluated,
The test chart includes a plurality of test patterns which are formed of black and white stripes extending in a predetermined first direction and arranged in a second direction perpendicular to the first direction, and the pitches of the black and white stripes are different. And
A luminance amplitude measuring step for measuring the luminance amplitude for each test pattern;
When the luminance amplitudes of the plurality of test patterns measured in the luminance amplitude measuring step are compared, and the test pattern with a fine pitch has a larger luminance amplitude than the test pattern with a coarser pitch than the test pattern. And a false resolution removing step of invalidating the luminance amplitude of the test pattern having a fine pitch.

  As explained above, the effects of false resolution and the effects of lighting conditions at the time of shooting are automatically removed, and the lens performance evaluation device that evaluates the lens performance correctly, and the operator only sets the test chart. Thereafter, a lens performance evaluation apparatus and a lens performance evaluation method for automatically evaluating the lens performance are realized.

  Embodiments of the present invention will be described below.

  3 and 4 are diagrams showing test charts constituting a part of the evaluation apparatus according to the embodiment of the present invention.

  In the following description, it is assumed that the lens performance is evaluated by a lens performance evaluation apparatus having the same configuration as the lens performance evaluation apparatus shown in FIG.

  First, the test chart 10 ′ shown in FIG. 3 will be described.

  The test chart 10 ′ shown in FIG. 3 has gray patches 101G to 106G, and pairs of the gray patches 101G to 106G and a plurality of test patterns 101T to 106T for lens performance evaluation are separated at a plurality of locations. It is formed. The plurality of test patterns 101T to 106T have the same or similar shape on the test chart 10 'and are distributed in a plurality of directions. Evaluation of the lens performance at the tele end and the wide end of the zoom lens is performed by any one of these test patterns.

  A test chart 10 'shown in FIG. 3 is a plurality of test patterns 101T to 106T, each of which is specified by a position recognition marker 107, and one of the test patterns 101T to 106T. The marker M1 of the first test pattern 101T is the first marker M1 having a larger dimension than the marker 107 of the other test pattern. The position of another marker is specified by the first marker of the test pattern having the first marker M1 having a large dimension, and the lens performance is evaluated. In the following description, the test pattern 101T including the first marker may be described as a reference pattern.

  The test chart shown in FIG. 3 is formed with test patterns for measuring the resolution in the vertical, horizontal, and oblique 45 degrees directions, and the horizontal lines, vertical lines, and diagonal lines of each of the plurality of test patterns extend. Each direction corresponds to a second direction according to the present invention, and each direction in which black and white stripes are arranged corresponds to a first direction according to the present invention.

  The test chart 10 'is photographed, image data representing the chart is generated by the photographing device 11 (see FIG. 1), and the generated image data is supplied to the PC 12 (see FIG. 1). The lens performance is evaluated.

  The PC 12 is provided with storage means (not shown), and the storage means stores the relative positions of the other markers 107 from the first marker M1. The storage means also stores a shooting lens performance evaluation program. When the program is executed, image data is guided from the shooting device 11 to the PC 12 and the shooting lens performance evaluation is performed by the PC 12 based on the image data. It is configured to be performed.

  The program in the storage means provided in the PC 12 recognizes the position of the first marker M1 based on the image data, and based on the recognition position of the first marker and the relative position stored in the storage means. A processing step for performing marker position recognition processing for recognizing the marker position, a processing step for performing white balance processing, and the like are described, and the lens performance based on the image data generated by the photographing apparatus 11 by the PC 12 according to the procedure of the program. Evaluation is performed. Here, based on the recognition position of the first marker recognized by performing the marker position recognition processing of the first marker M1 on the test chart shown in FIGS. The lens performance is evaluated using the test pattern specified by.

  Here, with reference to FIG. 4, the configuration will be described by taking up the reference pattern 101T which is one of the test patterns 101T to 106T arranged in the same or similar form.

  FIG. 4 is a diagram showing a test pattern configuration of the reference pattern 101T. Other test patterns have the same configuration, but the size of the central first marker M1 is different from other markers.

  The position of the first marker M1 and the relative position of other markers with respect to the position of the first marker M1 are stored in the storage unit inside the PC 12.

  One of the test patterns in FIG. 4 shows a plurality of scan lines that scan the test pattern along the first direction of the test pattern 1010T, and the luminance amplitude is detected for each of the plurality of scan lines. It is shown that a performance evaluation is performed. The luminance amplitude is similarly detected for other test patterns.

  Here, the features of the present embodiment will be described with reference to FIG.

  FIG. 5 is a diagram for explaining the detection of luminance amplitude for each scanning line performed by the PC 12.

  As it is, there is a problem that the luminance amplitude shown in FIG. 2B appears by all means when a high-frequency side, that is, a fine pitch test pattern in the test pattern 1010T portion of FIG. 4 is captured. Therefore, the applicant of the present invention has made the PC12 corresponding to the luminance amplitude measuring means referred to in the present invention, by slightly tilting the arrangement direction of the stripes of the test pattern 1010T in this portion so that the positional deviation from the light receiving element appears remarkably. The lens performance is evaluated by detecting a predetermined number of luminance amplitudes (in FIG. 5, two A ′ and C ′) and averaging the predetermined number of luminance amplitudes in descending order of the measured luminance amplitude. Improved to do.

  In this way, even if the luminance amplitude decreases as shown in FIG. 2B, the portion where the luminance amplitude decreases is ignored, and only the portion of the luminance amplitude shown in FIG. Evaluation is performed.

  What has been described above will be described together in a flowchart.

  FIG. 6 is a flowchart for explaining luminance amplitude detection processing performed by the PC 12. In this example, the processing of the flow in FIG. 6 corresponds to the lens performance evaluation method.

  In step S601, the image capturing apparatus 11 is instructed to receive image input and output image data. In step S602, the position of the first marker is recognized based on the image data. In the next step S603, the position of the other marker is recognized based on the recognition position of the first marker and the relative position of the other marker stored in the storage means. In the next step SS604, the measurement position is determined (see FIG. 4). In the next step S605, the test pattern is scanned a plurality of times while shifting the test pattern between both markers one pixel at a time (see FIGS. 4 and 5).

  When a plurality of luminance amplitudes are obtained by a plurality of scans in step S505, the luminance amplitudes are compared in the next step S606, and a predetermined number of luminance amplitudes are extracted in descending order. In step S607, the average of the predetermined number of luminance amplitudes extracted is calculated, and in step S608, the resolution, which is the evaluation value, is calculated and displayed, and the process of the flow ends.

  If this flow is processed, even if a waveform with a small luminance amplitude is obtained when a high-frequency side, that is, a test pattern with a narrow array interval, is captured, only the large waveform portion is extracted and the luminance amplitude is detected correctly. The lens performance is correctly evaluated.

  As described above, the lens performance evaluation apparatus and the lens performance evaluation method are realized in which the lens performance is automatically evaluated after the operator simply sets the test chart.

  FIG. 7 is a diagram for explaining the second embodiment.

  In the first embodiment, the influence of the decrease in luminance amplitude is removed. However, if there is a pixel defect or the like, a value having a luminance amplitude larger than a predetermined value is detected. Therefore, in the second embodiment, detection is performed due to a pixel defect or the like. It is also possible to perform processing for excluding the luminance amplitude.

  The process is the same as that in FIG. 6 except that the processes in steps S6051 and S6061 are added.

  The process up to step S605 is the same as the process of FIG. 6, and when there is a scan line having a luminance amplitude exceeding a predetermined limit amplitude in step S6051, the process of excluding the scan line is performed in step S6051. The improvement is made so that a predetermined number of luminance amplitudes are extracted in descending order from the luminance amplitude measured in step S6061.

  When the processing of the flow of FIG. 7 is performed, erroneous evaluation due to the influence of a pixel defect or the like is eliminated.

  Further, as described above, when the contour enhancement processing is performed on the photographing apparatus 11 (see FIG. 1) side, an evaluation value as if the high resolution is apparently caused by overshooting at the edge portion of the luminance amplitude. May be obtained. Further, when an image of the portion where the overshoot occurs is viewed, both sides of the portion where the overshoot occurs may appear blurred. In this case, it is problematic to determine that the resolution is high.

  Therefore, in the third embodiment, the PC 12 (see FIG. 1) calculates an evaluation value correlated with the standard deviation of the measured luminance values at a plurality of points.

  8, 9, and 10 are diagrams for explaining the third embodiment.

  FIG. 8 is a diagram illustrating a monochrome reference patch, and FIG. 9 is a diagram illustrating luminance amplitude.

  The black-and-white reference patch shown in FIG. 8 is provided on the test chart, and using the measured value of the luminance amplitude of the reference patch, as shown in FIG. ) Is taken into consideration so that the luminance amplitude is detected and correct evaluation can be performed.

Here, the PC 12 as the evaluation value calculation means has an average value of a plurality of luminance values a, a reference white level b, a reference black level c, and a maximum value that can be taken as a luminance value. MAX (here, 1024 because the PC performs processing in 10-bit processing unit), the minimum value that can be taken as the luminance value is MIN (here, 0), and the luminance value smaller than the average value a among the luminance values of the plurality of points. D ₁ , d ₂ ,..., D _m , and deviations of the luminance values larger than the average value a among the plurality of luminance values from the average value, e _1, e _2, ..., when the _{e n,}
Variable group _{(F × e 1, F ×} e 2, ..., F × e n, G × d 1, G × d 2, ..., G × d m)
However, F = (MAX−a) / (b−a)
G = (a-MIN) / (ac)
It is.
Is calculated as an evaluation value.

  When evaluating with simple luminance amplitude, if there is overshoot or undershoot, only the luminance amplitude of that part tends to be evaluated, but according to the above formula, the evaluation value indicating the magnitude of the luminance amplitude as a whole waveform is Can be calculated.

  What has been described above will be described in a flow.

  FIG. 10 is a flowchart showing a procedure of processing relating to evaluation of lens performance performed by the PC 12.

  The process is the same as that of FIG. 6 except that the processes of steps S6051 and S6071 are added.

  In step S6051, the brightness of the reference patch (see FIG. 9) is measured, the standard deviation is calculated using the formula of FIG. 10 in step S6071, and the evaluation value (resolution) is calculated in step S608. Yes.

  In this way, the lens performance evaluation apparatus can calculate a correct evaluation value after removing the influence of overshoot and undershoot.

  FIG. 11 is a diagram for explaining the fourth embodiment.

  Although described as the fourth embodiment, in the first to third embodiments, the luminance amplitude is accurately detected after the luminance is corrected by the white balance adjustment described in the fourth embodiment. It is.

  The process is the same as that in FIG. 6 except that the processes in steps S6041 to S6044 are added.

  As described above, when the white balance changes depending on the illumination state at the time of shooting, the luminance amplitude changes. Therefore, improvements are made so that the correct luminance amplitude can be obtained even if the white balance changes.

  In step S6041, the RGB values of the gray patch in the image data generated by the photographing apparatus are read. In the next step S6042, white balance adjustment is performed using these values.

  If the white balance adjustment is performed by multiplying each of the red (R) and blue (G) values by gain so that the green (G) value becomes the reference value in step S6042, the next step S6043 After adjusting the white balance for each area, proceed to the next step. In step S6044, the brightness is calculated by the following equation using the values of R, G, and B after the white balance is adjusted.

Luminance = 0.3 x R + 0.6 x G + 0.1B
Thereafter, the processing from step S605 to step S608 is performed, and the lens performance evaluation is completed.

  In this way, the brightness is calculated based on the gray patch closest to the test pattern, so even if the white balance of a part of the image changes due to the partial lighting condition at the time of shooting Can be detected.

  As described above, the lens performance evaluation apparatus is realized in which the influence of the illumination light at the time of shooting is automatically removed and the lens performance is correctly evaluated.

  Finally, the processing when image processing is performed in the image processing unit in the photographing apparatus and the test pattern with a fine pitch exhibits a larger luminance amplitude than the test pattern with a coarser pitch than the test pattern will be described. Keep it.

  FIG. 12 is a diagram for explaining the fifth embodiment.

  6 is the same as FIG. 6 except that step S6052 is added to the flowchart of FIG.

  When it is detected in step S6052 that the luminance amplitude peak obtained by scanning on the fine pitch side is larger than the luminance amplitude of the coarse test pattern, processing for invalidating the luminance amplitude of the fine pitch test pattern is performed. Is doing.

  In this way, even if an image processing circuit in the imaging apparatus generates an image as if it were high resolution, erroneous evaluation is not performed under the influence of the portion (false resolution). .

  As described above, the lens performance evaluation apparatus is realized in which the influence of the false resolution is automatically removed and the lens performance is correctly evaluated.

It is a figure which shows the structure of the lens performance evaluation apparatus which evaluates a lens performance based on the image data showing the test chart image | photographed with the imaging device. It is a figure which shows the brightness | luminance amplitude detected based on the image data which a test chart represents, when a lens performance evaluation apparatus evaluates lens performance. It is a figure which shows the test chart which comprises a part of lens performance evaluation apparatus which is one Embodiment of this invention. It is a figure which shows the test pattern structure of the reference pattern 101T. It is a figure explaining the detection of the luminance amplitude for every scanning line performed by PC. It is a flowchart explaining the detection process of the luminance amplitude which PC performs. It is a figure explaining 2nd Embodiment. It is a figure explaining 3rd Embodiment. It is a figure explaining 3rd Embodiment. It is a flowchart which shows the procedure of the process regarding evaluation of the lens performance which PC performs. It is a figure explaining 4th Embodiment. It is a figure explaining 5th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens performance evaluation apparatus 10 Test chart 101G-106G Gray patch 101T-106T Test pattern M1 1st marker 107 Marker 11 Imaging device 12 Personal computer (PC)

Claims (18)

In a lens evaluation device that evaluates the performance of the photographing lens based on image data representing the test chart obtained by imaging a test chart on an imaging element with a photographing lens.
The test chart has a test pattern composed of black and white stripes extending in a predetermined first direction and arranged in a second direction perpendicular to the first direction,
Luminance amplitude measuring means for measuring the luminance amplitude on the image data in each of a plurality of scanning lines in which the test pattern is arranged in the first direction;
Lens performance comprising: an average amplitude calculating means for detecting a predetermined number of luminance amplitudes in order from the one having the largest luminance amplitude measured by the luminance amplitude measuring means and averaging the predetermined number of luminance amplitudes Evaluation device.   The average amplitude calculation means excludes scanning lines having a luminance amplitude exceeding a predetermined limit amplitude, and extracts a predetermined number of luminance amplitudes from the measured luminance amplitude in descending order to obtain the predetermined number of luminance amplitudes. The lens performance evaluation apparatus according to claim 1, wherein the lens performance evaluation apparatus performs averaging. In a lens performance evaluation apparatus that evaluates the performance of the photographic lens based on image data representing the test chart obtained by imaging a test chart on an image sensor with a photographic lens.
In the test chart, a plurality of test patterns each having a position recognition marker are dispersedly arranged, and one of the plurality of test patterns has a first test pattern marker of another test pattern. A first marker that is larger than the marker,
Storage means for storing relative positions of other markers from the first marker;
Marker position recognition that recognizes the position of the first marker based on the image data and recognizes the position of another marker based on the recognition position of the first marker and the relative position stored in the storage means Means,
A lens performance evaluation apparatus comprising: lens performance evaluation means for performing lens performance evaluation using a test pattern specified by the marker based on the marker position recognized by the marker position recognition means.   The lens performance evaluation apparatus according to claim 3, wherein the plurality of test patterns have the same or similar shape on the test chart and are distributed in a plurality of directions. In a lens performance evaluation apparatus that evaluates the performance of the photographic lens based on image data representing the test chart obtained by imaging a test chart on an imaging device with a photographic lens.
The test chart has a test pattern composed of black and white stripes extending in a predetermined first direction and arranged in a second direction perpendicular to the first direction,
Brightness value measuring means for measuring brightness values on the image data at a plurality of scanning lines extending in a direction crossing the stripe in the test pattern;
An apparatus for evaluating lens performance, comprising: evaluation value calculating means for calculating an evaluation value correlated with a standard deviation of the luminance values at a plurality of points measured by the luminance value measuring means. The evaluation value calculation means can take an average value of a plurality of brightness values measured by the brightness measurement means as a, a reference white level as b, a reference black level as c, and a maximum possible brightness value. MAX is the value, MIN is the minimum value that can be taken as the luminance value, and d ₁ , d ₂ ,..., _Dm are the deviations from the average value of the luminance values smaller than the average value a among the plurality of luminance values. the average value greater luminance value than a of the luminance values of a plurality of points, the deviation from the average value e _1, e 2, _..., when the e _n,
Variable group _{(F × e 1, F ×} e 2, ..., F × e n, G × d 1, G × d 2, ..., G × d m)
However, F = (MAX−a) / (b−a)
G = (a-MIN) / (ac)
It is.
The lens performance evaluation apparatus according to claim 5, wherein the standard deviation is calculated as the evaluation value. In a lens performance evaluation apparatus that evaluates the performance of the photographic lens based on image data representing the test chart obtained by imaging a test chart on an image sensor with a photographic lens.
The test chart has a gray patch,
White balance adjusting means for adjusting white balance based on image data on the gray patch;
A lens performance evaluation device, comprising: lens performance evaluation means for evaluating the performance of the photographing lens based on the image data adjusted by the white balance adjustment means. The test chart is a lens performance evaluation test pattern and a pair of gray patches formed at a plurality of locations separated from each other,
The white balance adjusting means has lens performance based on each test pattern paired with each gray patch based on each image data in which white balance is adjusted based on each of the plurality of gray patches constituting the plurality of pairs. The lens performance evaluation apparatus according to claim 7, wherein the evaluation is performed. In a lens performance evaluation apparatus that evaluates the performance of the photographic lens based on image data representing the test chart obtained by imaging a test chart on an image sensor with a photographic lens.
The test chart includes a plurality of test patterns which are formed of black and white stripes extending in a predetermined first direction and arranged in a second direction perpendicular to the first direction, and the pitches of the black and white stripes are different. And
Luminance amplitude measuring means for measuring the luminance amplitude for each test pattern;
When the luminance amplitudes of the plurality of test patterns measured by the luminance amplitude measuring unit are compared, the test pattern with a fine pitch has a luminance amplitude larger than the test pattern with a coarser pitch than the test pattern. A lens performance evaluation apparatus comprising false resolution removing means for invalidating the luminance amplitude of the test pattern having a fine pitch. In a lens evaluation method for forming a test chart on an image sensor with a photographic lens to generate image data representing the test chart, and evaluating the performance of the photographic lens based on the image data,
The test chart has a test pattern composed of black and white stripes extending in a predetermined first direction and arranged in a second direction perpendicular to the first direction,
A photographing step for generating image data in a state in which the arrangement direction of the light receiving elements constituting the imaging element is inclined with respect to the first direction;
A luminance amplitude measuring step for measuring a luminance amplitude on the image data in each of the scanning lines in which the test pattern is arranged in the first direction;
A lens performance evaluation comprising: an average amplitude calculating step of detecting a predetermined number of luminance amplitudes in order from the one having the largest luminance amplitude measured in the luminance amplitude measuring step and averaging the predetermined number of luminance amplitudes Method.   In the average amplitude calculating step, a scanning line having a luminance amplitude exceeding a predetermined limit amplitude is excluded, and a predetermined number of luminance amplitudes are extracted in descending order from the measured luminance amplitude to obtain the predetermined number of luminance amplitudes. The lens performance evaluation method according to claim 10, wherein averaging is performed. In a lens performance evaluation method for forming an image data representing a test chart by imaging a test chart on an imaging element with a photographing lens, and evaluating the performance of the photographing lens based on the image data,
In the test chart, a plurality of test patterns each having a position recognition marker are dispersedly arranged, and one of the plurality of test patterns has a first test pattern marker of another test pattern. A first marker that is larger than the marker,
A storage step of storing a relative position of another marker from the first marker;
Marker position recognition that recognizes the position of the first marker based on the image data and recognizes the position of another marker based on the recognition position of the first marker and the relative position stored in the storage means Steps,
A lens performance evaluation method comprising: a lens performance evaluation step for performing lens performance evaluation using a test pattern specified by the marker based on the marker position recognized in the marker position recognition step.   The lens performance evaluation method according to claim 12, wherein the plurality of test patterns have the same or similar shape on the test chart and are distributed in a plurality of directions. In a lens performance evaluation method for imaging a test chart on an image sensor with a photographic lens to generate image data representing the test chart, and evaluating the performance of the photographic lens based on the image data,
The test chart has a test pattern composed of black and white stripes extending in a predetermined first direction and arranged in a second direction perpendicular to the first direction,
A luminance value measuring step of measuring a luminance value on the image data at a plurality of scanning lines extending in a direction across the stripe of the test pattern;
A lens performance evaluation method comprising: an evaluation value calculation step of calculating an evaluation value correlated with a standard deviation of the luminance values at a plurality of points measured by the luminance value measuring means. In the evaluation value calculation step, the average value of the luminance values measured at the luminance measuring means is a, the reference white level is b, the reference black level is c, and the maximum value that can be taken as the luminance value. MAX is the value, MIN is the minimum value that can be taken as the luminance value, and d ₁ , d ₂ ,..., _Dm are the deviations from the average value of the luminance values smaller than the average value a among the plurality of luminance values. the average value greater luminance value than a of the luminance values of a plurality of points, the deviation from the average value e _1, e 2, _..., when the e _n,
Variable group (F × e ₁ , F × e ₂ ,..., F × e _n , G × d ₁ , G × d ₂ , ..., G × _d m)
However, F = (MAX−a) / (b−a)
G = (a-MIN) / (ac)
It is.
The lens performance evaluation method according to claim 14, wherein the standard deviation is calculated as the evaluation value. In a lens performance evaluation method for forming an image data representing a test chart by imaging a test chart on an imaging element with a photographing lens, and evaluating the performance of the photographing lens based on the image data,
The test chart has a gray patch,
A white balance adjustment step for adjusting white balance based on image data on the gray patch;
A lens performance evaluation method comprising: a lens performance evaluation step for evaluating the performance of the photographing lens based on the image data adjusted by the white balance adjustment step. The test chart is a lens performance evaluation test pattern and a pair of gray patches formed at a plurality of locations separated from each other,
In the white balance adjustment step, lens performance based on each test pattern paired with each gray patch is based on each image data in which white balance is adjusted based on each of the plurality of gray patches constituting the plurality of pairs. The lens performance evaluation method according to claim 16, wherein the lens performance evaluation method is an evaluation step. In a lens performance evaluation method of forming an image data representing a test chart by imaging a test chart on an image sensor with a photographic lens, and evaluating the performance of the photographic lens based on the image data,
The test chart includes a plurality of test patterns which are formed of black and white stripes extending in a predetermined first direction and arranged in a second direction perpendicular to the first direction, and the pitches of the black and white stripes are different. And
A luminance amplitude measuring step for measuring the luminance amplitude for each test pattern;
When the luminance amplitudes of the plurality of test patterns measured in the luminance amplitude measuring step are compared, the test pattern with a fine pitch has a luminance amplitude larger than the test pattern with a coarser pitch than the test pattern. And a false resolution removing step of invalidating the luminance amplitude of the test pattern having a fine pitch.

Images