JP2014155063A - Chart for resolution measurement, resolution measurement method, positional adjustment method for camera module, and camera module manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly perform positional adjustment (angular adjustment) of a lens unit, and to shorten a time for manufacturing a camera module.SOLUTION: A chart for resolution measurement (100) for measuring resolution by each image height in a camera module comprising a lens unit and an imaging sensor comprises: marker figures (105, 106) for detecting the center coordinates of the chart (100); and a striped pattern for resolution measurement (110) obtained by alternately arranging black linear patterns (110a) and white linear patterns (110b) in the whole plane surface of the chart (100).

Description

  The present invention relates to a technology for measuring the resolution and adjusting the positional relationship between a lens unit and an imaging sensor in a camera module mounted on a small electronic device such as a mobile phone or a smartphone, and more specifically, measuring the resolution. The present invention relates to a resolution measurement chart, a resolution measurement method, a position adjustment method in a camera module, and a camera module manufacturing method.

  A camera module mounted on a cellular phone, a smartphone, or the like is an integrated lens unit incorporating a photographing lens and an image sensor incorporating an image sensor such as a CCD or CMOS, and is small in a small electronic device. It is miniaturized so that it can be installed in the housing. Today, in such a camera module, the number of pixels of an image sensor is increasing as in the case of a digital camera or the like.

  By the way, since the aperture ratio of the image sensor decreases as the number of pixels increases, it is necessary to strictly adjust the position of the imaging lens and the image sensor in order to obtain an image with a resolution corresponding to a high number of pixels.

  However, in the lens unit, the photographing lens is housed in a cylindrical lens barrel that holds the photographing lens. However, there is a manufacturing variation in the fixing position of the photographing lens with respect to the lens barrel. Is not necessarily parallel to the central axis.

  Therefore, even if the imaging sensor is assembled to such a lens unit so that the central axis of the lens barrel and the normal of the imaging surface of the imaging element are parallel, the photographic lens accommodated in the lens barrel And the normal of the imaging surface of the image sensor are not parallel (in other words, the optical axis of the imaging lens and the imaging surface of the image sensor are not perpendicular).

  If the optical axis of the photographic lens and the normal of the imaging surface of the image sensor are not parallel, the center of the photographed image is in focus, but the part out of the center is out of focus (described later) Half blurring phenomenon). As a result, the total performance is out of specification.

  In order to avoid such problems, the resolution by image height of the image formed on the imaging surface of the image sensor through the lens unit is dynamically measured by changing the tilt of the lens unit when manufacturing the camera module. A method of adjusting the position of the lens unit with respect to the image sensor using the measured resolution according to image height is effective. Dynamically measuring the resolution means measuring while changing the distance (relative distance) between the lens unit and the image sensor.

  For example, Patent Document 1 discloses a method of adjusting and fixing a lens unit with respect to an image sensor to an optimum angle using a camera module manufacturing apparatus. Patent Documents 2 to 5 disclose a method for detecting a specific marker in a resolution measurement chart.

Japanese Patent No. 4960307 JP-A-2005-198103 JP 2003-043328 A JP 2007-104296 A JP 2007-096699 A

  However, the conventional technique has a problem that it takes time to adjust the position (angle adjustment) of the lens unit, and thus, it takes time to manufacture the camera module. This will be described.

  The resolution according to image height of the image formed on the image sensor is obtained by photographing the image height graphic arranged on the resolution measurement chart with the image sensor and analyzing the image data. The resolution of the image is represented by the spatial frequency response (SFR) of the image. The graphic by image height on the resolution measurement chart is a predetermined figure defined as an image height position on the imaging plane in a state (in the imaging area) where the resolution measuring chart is imaged on the imaging plane of the imaging device. It is arranged to be located at the coordinates.

  However, in the adjustment of the position of the lens unit, the resolution at different image heights is measured while changing the distance (relative distance) between the lens unit and the imaging sensor. The imaging area changes.

  That is, in a state where the imaging sensor is separated from the lens unit, the imaging area of the imaging sensor is narrower than the resolution measurement chart, and a part of the resolution measurement chart forms an image (the imaged image portion is captured). Area part). Then, by moving the imaging sensor closer to the lens unit, the imaging area gradually increases and eventually becomes wider than the resolution measurement chart (the outer edge of the resolution measurement chart enters the imaging area). .

  As described above, if the distance between the image sensor and the lens unit is changed, the imaging area of the image sensor also changes accordingly. Therefore, the predetermined coordinates (fixed coordinates) on the image plane are used as the measurement range for the image height resolution. If it is fixed as, it is possible to obtain the resolution according to the image height only from the limited figure according to the image height that has entered the measurement range. For this reason, conventionally, the image height-specific figure that has entered the imaging area is tracked, the coordinates on the image plane where the image height-specific figure exists are specified, and the image height resolution is measured using this as the measurement range. Yes.

  However, in order to track the figure according to image height and specify the existing coordinates, it is necessary to perform a search for the entire imaging area, which takes time. As a result, as described above, it takes time to adjust the position of the lens unit with respect to the image sensor.

  Also, the coordinates on the image plane where the figure by image height exists in the shooting area is specified and this is used as the measurement range, so the position where the resolution by image height is actually measured is the image for which you really want to obtain the resolution. It will not be high. For this reason, a calculation for estimating the image height position to be truly obtained is also required, which takes time.

  And this problem cannot be solved even if it has the technique of above-mentioned patent documents 1-5. For example, Patent Document 1 does not relate to speeding up the process of adjusting and fixing the lens unit to the optimum angle with respect to the image sensor, and therefore, the time required to dynamically measure the resolution when manufacturing the camera module. There is no description of a configuration for shortening (hereinafter, dynamic resolution measurement time).

  Also, with the technique for dynamically measuring resolution described in Patent Document 1, the resolution can be measured only at a position of a graphic by image height that is arranged in advance on a resolution measurement chart that is a subject. Therefore, at the time of measuring the resolution, as described above, the graphic according to the image height is traced in accordance with the movement of the lens unit, and the obtained resolution is not at the image height position to be truly obtained.

  Further, Patent Documents 2 to 5 describe techniques for detecting and tracking a specific marker on a chart. However, even if a mark arranged on the chart is tracked, the image height position and resolution on the imaging device are described. The difference from the image height position on the measurement chart cannot be solved.

  An object of the present invention is to make it possible to adjust the position (angle adjustment) of a lens unit at high speed, and to shorten the manufacturing time of a camera module.

  In order to solve the above problems, a resolution measurement chart according to an aspect of the present invention is a resolution measurement chart for measuring resolutions according to image heights in a camera module including a lens unit and an imaging sensor. , A stripe pattern in which a marker figure for detecting the center coordinates of the resolution measurement chart, a black linear pattern, and a white linear pattern are alternately arranged over the entire plane of the resolution measurement chart And a resolution measurement pattern.

  In order to solve the above-described problem, a resolution measurement method according to an aspect of the present invention uses a resolution measurement chart according to an aspect of the present invention to determine resolutions by image height of a camera module that is a resolution measurement target. A resolution measuring method for measuring, the step of inputting image data of a chart image obtained by photographing the resolution measurement chart with a camera module, and the image data of the chart image or more fixed coordinates in an imaging sensor of the camera module An image extraction step for extracting image data of each measurement range for each image height, a rearrangement process for rearranging the image data of each measurement range extracted in order from the smallest pixel value, and the rearranged image data And an SFR calculating step for obtaining SFR from the above.

  In order to solve the above problems, a position adjustment method in a camera module according to an aspect of the present invention uses a resolution measurement method according to an aspect of the present invention to obtain a focal length for each image height of the camera module. The positions of the lens unit and the image sensor provided in the camera module are adjusted based on the obtained focal lengths by image height.

  In order to solve the above-described problem, a method for manufacturing a camera module according to an aspect of the present invention includes a method for adjusting the position of a lens unit and an imaging sensor in the position adjustment method in the camera module according to an aspect of the present invention. It is characterized by being used for.

  According to the aspect of the present invention, it is possible to perform the position adjustment (angle adjustment) of the lens unit at high speed, and in turn, it is possible to shorten the manufacturing time of the camera module.

It is a top view of the chart for resolution measurement which is one embodiment concerning the present invention. It is a schematic cross section of a camera module. It is a block diagram of the measurement system which measures SFR of a camera module. It is a top view of SFR chart ISO12233 which is a typical chart for resolution measurement used conventionally. It is drawing explaining correction when the photographic lens is tilted to the left inside the lens barrel. It is drawing explaining correction when a photographic lens is tilted to the right inside the lens barrel. It is explanatory drawing which shows the relative relationship between a lens unit and an imaging sensor, the taken-out image, SFR value, and the relative distance of a lens unit and an imaging sensor, and SFR in the SFR measurement using the conventional chart for resolution measurement. It is explanatory drawing which shows the relationship between the luminance value of an adjacent pixel, and SFR value. It is explanatory drawing which shows the positional relationship of the figure according to image height imaged on an image sensor according to the relative distance of a lens unit and an image sensor, when SFR is measured using the conventional chart for resolution measurement. . It is a graph showing the relationship between the position (VCM position) of the lens unit with respect to the image sensor and the SFR measured using a conventional resolution measurement chart. It is explanatory drawing which shows the procedure which detects the image which image | photographed the figure according to image height from the imaging area which the imaging sensor image | photographed, when the conventional chart for resolution measurement is used. It is explanatory drawing which shows another procedure which detects the image which image | photographed the figure according to image height from the imaging area which the imaging sensor image | photographed when the conventional chart for resolution measurement was used. It is drawing explaining the reason why the striped pattern in the resolution measurement chart is inclined. FIG. 2 shows images within the measurement range at each distance position when the imaging sensor is moved with respect to the lens unit, and a case where the resolution measurement chart of FIG. 1 is used and a case where the conventional resolution measurement chart is used. It is explanatory drawing which compares and shows. It is explanatory drawing which shows the procedure which measures SFR in each image height position using the chart for resolution measurement which is this Embodiment shown in FIG. It is explanatory drawing which shows the process implemented in the process 3 in FIG. 15, and rearranges the cut-out image data about the X side. 2 is a graph showing the relationship between the position of a lens unit (VCM position) with respect to an imaging sensor at a certain image height position and SFR measured using the resolution measurement chart of FIG. 1.

  Although embodiments of the present invention will be described in detail, technical matters which are the premise of the present invention, such as how to adjust the positions of an image sensor and a lens unit, will also be described.

1) Position Adjustment of Lens Unit with respect to Image Sensor First, the position adjustment of the lens unit with respect to the image sensor will be described. FIG. 2 is a schematic cross-sectional view of the camera module. As shown in FIG. 2, the small camera module 1 has a lens unit 2 driven by a VCM (not shown) on an image sensor 3 in which an image sensor 12 such as a CCD or CMOS is incorporated as a basic structure. Be placed. The lens unit 2 includes a cylindrical lens barrel 11 that holds the photographing lens 10, and the photographing lens 10 is accommodated therein.

  As described above, the relationship between the lens unit 2 and the VCM outer shape reference position cannot be vertical due to manufacturing assembly errors. As a result, in the assembly of the camera module 1 based on the standard VCM outer shape reference, the image pickup device 12 is used. The normal line of the imaging plane and the optical axis of the photographing lens 10 in the lens unit 2 are not parallel to each other, and an angle error is included.

  The angle error between the normal of the imaging surface of the image sensor 12 and the optical axis of the photographic lens 10 directly varies in focus distance, and the in-focus position between the center of the imaging surface and the periphery of the imaging surface. The focal position moves back and forth, and a phenomenon called so-called single blur occurs.

  In order to correct such a one-sided blur phenomenon, an operation of tilting the image sensor 3 is performed based on the amount of image plane tilt of the photographing lens 10 in the lens unit 2. The image plane inclination amount is obtained by performing a reverse calculation with a trigonometric function from the focal distance for each image height and the pixel pitch distance on the image sensor 3 in the measurement range for each image height. By giving the image unit tilt angle obtained by the trigonometric function to the lens unit 2 or the image sensor 3, the focal lengths for the respective image heights are aligned, and the normal of the image formation surface of the image sensor 3 and the optical axis of the photographing lens 10 are obtained. Becomes parallel and one-sided blur is eliminated.

  FIG. 3 is a block diagram of a measurement system for measuring the resolution by image height (SFR) of the camera module. As shown in FIG. 3, the resolution for each image height is obtained by photographing the resolution measurement chart 7 with the camera module 1, and using the photographed image (chart image) for SFR calculation software (resolution measurement). The program) 5 is sent to a personal computer (PC) 4 in which the program 5 is installed, and the image is analyzed. At this time, the imaging plane of the image sensor 12 in the image sensor 3 and the resolution measurement chart 7 are positioned so as to be substantially parallel.

  The resolution measurement chart 7 shown in FIG. 3 illustrates an example in which three graphics M1, M2, and M3 according to image height are arranged. Conventionally, as the resolution measurement chart 7, the SFR chart shown in FIG. ISO12233 and similar charts are used. The present invention proposes a completely new resolution measurement chart, which will be described later.

  FIG. 5 is a view for explaining correction when the taking lens 10 is tilted to the L (left) side inside the lens barrel 11. In the figure, images obtained by photographing three graphics M1, M2, and M3 according to image height arranged on the resolution measurement chart 7 by the camera module 1 within a rectangular frame indicated by reference numerals 20 and 21 (imaging device). 12) m1, m2 and m3 formed on the 12 image planes.

  When the taking lens 10 is tilted to the L side inside the lens barrel 11, as shown in a rectangle 20, among the images m1, m2, and m3 taken by the image height-dependent figures M1, M2, and M3, CT (center) The image m1 positioned on the right side is a just-focus image, while the image m2 positioned on the L side is a defocused image focused after the imaging plane, and the image m3 positioned on the R (right) side is The defocused image is focused before the image plane.

  Such three images m1 to m3 are analyzed, and the respective resolutions according to image height are measured as described later, and the inclination of the lens unit 2 is adjusted based on them. Note that a rectangle indicated by reference numeral 30 indicates an area in which an image for measurement is extracted from the chart photographed image after measuring the image height-specific resolution from the images m1 to m3, and is a measurement range.

  In this case, the lens unit 2 is rotated so as to lift the L side. By performing such correction, the lens barrel 11 itself is tilted, but the optical axis of the photographing lens 10 inside thereof and the normal line of the imaging surface of the image sensor 12 become parallel. Further, after the correction, the images m1, m2, and m3 obtained by photographing the three image height-specific graphics M1, M2, and M3 are all just-focus images as shown in the rectangle 21.

  FIG. 6 is a view for explaining correction when the taking lens 10 is tilted to the R side inside the lens barrel 11. When the photographing lens 10 is inclined to the R side inside the lens barrel 11, as shown in a rectangle 22, among the images m1, m2, and m3 obtained by photographing the image height-specific figures M1, M2, and M3, the lens is located at the CT. The image m1 is a just-focus image, but the image m2 positioned on the L side is a defocused image focused before the imaging plane, and the image m3 positioned on the R side is higher than the imaging plane. The defocused image is focused later.

  Similar to the above, the three images m1 to m3 are analyzed, and the inclination of the lens unit 2 is adjusted. In this case, correction is performed by rotating the lens unit 2 so as to lift the R side. After the correction, the images m1, m2, and m3 obtained by photographing the three image height-specific graphics M1, M2, and M3 are all just-focus images as shown in the rectangle 23.

2) SFR Measurement Principle Next, the SFR (Spatial Frequency Response) measurement principle used as the image resolution will be briefly described. The SFR measurement method is defined in ISO12233. FIG. 7 is a diagram illustrating the relative relationship between the lens unit and the imaging sensor, the extracted image, the SFR value, and the relationship between the relative distance between the lens unit and the imaging sensor and SFR in the SFR measurement using the conventional resolution measurement chart. FIG.

  For the measurement of SFR, the measurement system shown in FIG. 3 is used, and the positional relationship between the camera module 1 and the resolution measurement chart 7 is fixed. The image sensor 3 is moved from a distant position to a close position with respect to the lens unit 2, and during the movement, a graphic by image height on the resolution measurement chart 7 is photographed at each position.

  SFR is obtained by taking out image data of one side in an image obtained by photographing a figure according to image height, and performing frequency decomposition (Fourier transform) on a change in luminance in a unit pixel. If the extracted image data of one side is in a focused state, the boundary between the black portion and the white portion becomes clear (see the intermediate position). On the other hand, when the focus is not achieved, the boundary between the black portion and the white portion becomes unclear, and a gray region exists at the boundary portion. The more out of focus, the thicker the gray area is (see the farthest and farthest positions).

  FIG. 8 is an explanatory diagram showing the relationship between the luminance value and SFR value of adjacent pixels. As shown in FIG. 8, the SFR value becomes 1.0 when the difference in luminance value between adjacent pixels is maximum (high contrast), and becomes smaller than 1.0 as the difference becomes smaller. It is 0.0 when there is no difference (low contrast).

  As shown in FIG. 7, when the SFR value is measured while changing the relative distance, it is very low at the position where the imaging sensor 3 and the lens unit 2 are farthest (relative distance is maximum), and increases as it approaches. It becomes the highest at the intermediate position where the focus is achieved, and becomes lower again after the in-focus position. Such an SFR value is measured for each image obtained by photographing a graphic by image height, and a focal length by image height is obtained.

3) Problems of Conventional Resolution Measurement Chart Next, problems of the conventional resolution measurement chart 7 will be described. FIG. 9 is an explanatory diagram showing the positional relationship of graphics according to image height formed on the image sensor in accordance with the relative distance between the lens unit and the image sensor. As shown in FIG. 9, when the lens unit 2 and the image sensor 3 are separated and far from each other, the distance between the surrounding four images m12 to m15 with respect to the image m11 obtained by photographing the graphic according to the image height located at the center is long. On the other hand, when the lens unit 2 and the image sensor 3 are close to each other, the distance between the surrounding four images m12 to m15 with respect to the center image m11 is close. When the distance between the lens unit 2 and the imaging sensor 3 is intermediate, the distances between the four surrounding images m12 to m15 with respect to the central image m11 are also intermediate.

  FIG. 10 is a graph showing the relationship between the position of the lens unit (VCM position) relative to the image sensor and the SFR measured using the conventional resolution measurement chart, and is measured from the five images m11 to m15 in FIG. SFR is shown. From such a graph, the optimum height of the lens unit 2 (relative distance to the image sensor 3) for each position by image height can be acquired.

  By the way, as shown in FIG. 9, even if the figure according to image height is accurately arranged on the resolution measurement chart 7 as the subject, the position of the image formed on the image sensor 3 is the same as that of the image sensor 3 and the lens. It depends on the distance to unit 2. In such a case, if the predetermined coordinates on the image plane are fixed as the measurement range of the resolution according to the image height, the resolution according to the image height can be obtained only from the image of the limited figure according to the image height that has entered the measurement range. I can't. For this reason, conventionally, a captured image of a figure according to image height is traced, a coordinate on an image plane on which the image exists is specified, and this is used as a measurement range to measure the resolution according to image height.

  However, in order to specify the coordinates on the image plane where the figure by image height in the shooting area exists, and to set this as the measurement range and the resolution by image height resolution, the position where the resolution by image height is actually measured is Therefore, the image height position where the resolution is truly desired is not obtained. For this reason, a calculation for estimating the image height position to be truly obtained is also required, which takes time.

  In addition, in order to track the figure by image height and specify the existing coordinates, it is necessary to perform a search for all areas of the imaging area, which takes time. This will be described in detail. FIG. 11 and FIG. 12 are explanatory diagrams illustrating a procedure for detecting an image obtained by photographing a graphic according to image height from an imaging area photographed by the imaging sensor. Among these, FIG. 11 detects the center of gravity of an image obtained by photographing a figure according to image height, and FIG. 12 detects a corner of an image obtained by photographing the figure according to image height.

  In FIG. 11, images m11 to m15 obtained by photographing five graphics according to image height in the resolution measurement chart 7 by the camera module 1 are shown in a rectangular frame indicated by reference numeral 30. In addition, a marker graphic for specifying the position of the graphic according to the image height is also arranged near the five graphic images according to the image height in the resolution measurement chart 7, and the images mg1 and mg2 obtained by photographing the marker graphic are also provided. Have been filmed.

  Step 1 (P1): Images mg1 and mg2 obtained by photographing marker figures are detected by pattern matching. In FIG. 11, a general barycentric mark is used as the marker graphic.

  Step 2 (P2): Approximate positions of the images m11 to m15 obtained by photographing the image height-specific figures are determined from the center coordinates (X in the figure) of the images mg1 and mg2 obtained by photographing the marker figures.

  Step 3 (P3): The coordinates of the same color as each image are detected in each of the images m11 to m15 based on the approximate positions of the images m11 to m15 obtained in the step 2 (painting operation).

  Step 4 (P4): In each of the images m11 to m15, the coordinates of the same color as each image are averaged to obtain the respective gravity center positions of the images m11 to m15, and the coordinates of each of the images m11 to m15 are specified.

  In FIG. 12, images m16 and m17 obtained by photographing two graphics according to image height in the resolution measurement chart 7 by the camera module 1 are shown in a rectangular frame denoted by reference numeral 31. In addition, a marker graphic for specifying the position of the graphic according to the image height is also arranged near the two graphic according to the image height in the resolution measurement chart 7, and the images mg1 and mg2 obtained by photographing the marker graphic are also provided. Have been filmed.

  Step 1 (P1): Images mg1 and mg2 obtained by photographing marker figures are detected by pattern matching. In FIG. 12, a general barycentric mark is used as the marker graphic.

  Step 2 (P2): Approximate positions of the images m16 and m17 obtained by photographing the image height-dependent graphic are determined from the central coordinates (X in the figure) of the images mg1 and mg2 obtained by photographing the marker graphic.

  Step 3 (P3): The approximate positions of the images m16 and m17 obtained in the step 2 are searched in the direction of 45 degrees, and the coordinates of different colors are detected in the images m16 and m17.

  Step 4 (P4): The coordinates of different colors are continuously detected in each of the images m16 and m17 while moving in the direction of 135 degrees from the approximate positions of the images m16 and m17 obtained in the step 2.

  Step 5 (P5): In the search operation, the farthest detected coordinate in each of the images m16 and m17 is specified as the corner coordinate of each of the images m16 and m17.

  As described above, in order to track the graphic according to image height and specify the existing coordinates, it is necessary to search for all areas of the imaging area, which takes much time.

4) One Embodiment of the Present Invention In the present invention, even if the position (relative distance) of the lens unit 2 with respect to the image sensor 3 changes and the image area changes accordingly, the resolution at different image heights is fixed coordinates. It becomes possible to measure. This is made possible by the resolution measurement chart proposed by the present invention.

  FIG. 1 is a plan view of a resolution measurement chart according to an embodiment of the present invention. As shown in FIG. 1, a resolution measurement chart 100 according to an embodiment has a resolution measurement pattern 110 disposed in the entire area together with marker figures 105 and 106 for detecting the center coordinates of the resolution measurement chart 100. It is a thing.

  The marker graphics 105 and 106 are used to detect the center coordinates of the resolution measurement chart 100. When the resolution measurement chart 100 is photographed, the coordinates of the images mg105 and mg106 (see FIG. 14) obtained by photographing the marker figures 105 and 106 are detected and used to detect the center coordinates of the resolution measurement chart 100.

  The resolution measurement pattern 110 is a striped pattern in which black linear patterns 110a and white linear patterns 110b are alternately arranged over the entire area of the resolution measurement chart. Each of the black linear pattern 110a and the white linear pattern 110b is a linear pattern having a constant line width. In other words, the resolution measurement pattern 110 is a striped pattern in which a plurality of black linear patterns 110a are arranged at a predetermined interval on a white background, and a white linear pattern is formed between the two black linear patterns 110a. Pattern 110b is formed.

  Here, the black linear pattern 110a and the white linear pattern 110b are inclined at an inclination of, for example, 15 ° with respect to a rectangular measurement range cut out from the captured image of the resolution measurement chart 100. This is to increase the accuracy of contrast detection. This will be described with reference to FIG. FIG. 13 is a diagram for explaining the reason why the striped pattern in the resolution measurement chart is inclined.

  By inclining the black linear pattern 110a and the white linear pattern 110b, as shown in FIG. 13A, the edge portion that changes from black to white in the resolution measurement chart is the pixel on the image sensor 3. Opportunities that overlap with the dead zone between the pixels can be reduced. As a result, the contrast detection accuracy can be increased. On the other hand, as shown in FIG. 13B, when no inclination is given, all edge portions may overlap between pixels on the image sensor 3 (dead zone). Yeah. In this case, although the gray portion described above actually exists, the gray portion is not detected. Therefore, if the contrast is high, an erroneous determination is made. Such an erroneous determination can be avoided by providing an inclination.

  In the resolution measurement pattern 110, the width of each of the black linear pattern 110a and the white linear pattern 110b is obtained by photographing the boundary between the black linear pattern 110a and the white linear pattern 110b. Any device capable of measuring SFR may be used.

  For example, the width of the black linear pattern 110a and the width of the white linear pattern 110b may be such that the area in the measurement range for measuring the resolution by image height is about 30%. With such a width, the black linear pattern 110a and the white linear pattern 110b are always included in the measurement range even if the lens unit 2 and the image sensor 3 are in the most distant positional relationship. Since the boundary is entered, the SFR can be measured from the image obtained by photographing the resolution measurement pattern 110. In the resolution measurement chart 100 of FIG. 1, the same width is used for the black linear pattern 110a and the white linear pattern 110b, but they may be different.

  A procedure for measuring the resolution at each image height position using the resolution measurement chart 100 according to the present embodiment will be described below with reference to FIGS. FIG. 14 shows images within the measurement range at each distance position when the imaging sensor is moved with respect to the lens unit. The case of using the resolution measurement chart of FIG. 1 and the conventional resolution measurement chart are used. It is explanatory drawing shown in comparison with the case where it had. FIG. 15 is an explanatory diagram showing a procedure for measuring the SFR at each image height position using the resolution measurement chart according to the present embodiment shown in FIG. FIG. 16 is an explanatory diagram showing a process of rearranging the cut-out image data on the X side, which is performed in step 3 in FIG. FIG. 17 is a graph showing the relationship between the position of the lens unit with respect to the imaging sensor and the SFR measured using the resolution measurement chart of FIG. 1 at a certain image height position.

  For the measurement of SFR, a measurement system similar to FIG. 3 is used, and a resolution measurement chart 100 is used instead of the resolution measurement chart 7. The positional relationship between the camera module 1 and the resolution measurement chart 100 is fixed. The image sensor 3 is moved from a distant position to a close position with respect to the lens unit 2, and the resolution measurement chart 100 is photographed at each distance position (far, middle, close) during the movement, and the photographed image (chart) From the image), an image within each measurement range determined by fixed coordinates is cut out according to each image height position.

  In FIG. 14, rectangular areas indicated by reference numerals 131 to 135 are SFR measurement ranges. The measurement range 131 is a measurement range for measuring the SFR at the center of the captured image (chart image). The measurement ranges 132 to 135 are set corresponding to the image height positions that are distant from the radial direction with the central measurement range 131 as the center. These measurement ranges 131 to 135 are fixed coordinates in the image sensor 3.

  As shown in FIG. 14, at the farthest position between the image sensor 3 and the lens unit 2, the shooting area is narrow, and the marker images mg105 and mg106 obtained by shooting the marker figures 105 and 106 are in the shooting area. As the separation distance between the image sensor 3 and the lens unit 2 becomes smaller, the photographing area becomes wider, and the photographing area becomes the largest at a close position where the separation distance becomes smaller. Compared to the case of being far away, the marker images mg105 and mg106 are smaller and located sufficiently inside than the case of the imaging area.

  In the figure according to image height, which is a rectangular image used in the conventional resolution measurement chart 7, the images m11 to m15 obtained by photographing the figure according to image height are classified according to the image height located in the center in accordance with the change of the photographing area. The positions of images m12 to m15 other than the image m11 obtained by photographing the figure change. For this reason, in order to fit the images m12 to m15 within the measurement range, the measurement range is changed and the graphic according to image height is tracked.

  On the other hand, in the case of the resolution measurement pattern 110 composed of the striped pattern arranged in the entire area of the resolution measurement chart 100, the number of striped patterns that fall within the measurement range changes with the change of the shooting area (FIG. 14). The resolution measurement pattern 100 is always located in the measurement ranges 131 to 135 (see the enlarged images in the measurement range 135 at each of the far and near positions). Therefore, even if the shooting area changes, there is no need to change the measurement range, and the measurement range can be fixed coordinates.

  In this manner, the image data of the image in the measurement range (fixed coordinates) defined as the high position is cut out from the image data of the image in the shooting area, and the resolution by image height is obtained. Specifically, it is performed through the steps shown in FIG.

  Step 1 (P1): An image obtained by photographing the marker graphic is detected from the image data of the image in the photographing area by pattern matching. In the resolution measurement chart 100, a general barycentric mark is used as a marker graphic.

  Step 2 (P2): Image data to be measured is cut out from the measurement range of fixed coordinates at each image height position.

  Step 3 (P3): The image data that has been cut out is rearranged by rearranging the X-side array data in ascending order. The X-side arrangement is a direction along the arrangement direction (a direction crossing the stripe pattern) of the black linear pattern 110a and the white linear pattern 110b.

  The rearrangement in step 3 will be described with reference to (a) to (c) of FIG. FIG. 16 is an explanatory diagram showing a process of rearranging the cut out image data on the X side.

  As shown in FIG. 16A, the cut-out image data is represented by array data corresponding to the luminance data of each pixel. FIG. 16A shows a part of the image in the measurement range 135 in FIG. 14 scanned in one direction, pixel coordinates on the X axis, and luminance on the Y axis.

By rearranging such image data in the order of the X side arrangement data, it becomes analysis data, and is a shape data obtained by cutting out the edges of a rectangular image with constant light and darkness as shown in FIG. become.
FIG. 16B shows an image after the X-side array data is rearranged in ascending order. FIG. 16B shows a plurality of white lines obtained by collecting a plurality of black line images obtained by photographing the black linear pattern 110a in the image within the measurement range 135 in FIG. 14 and photographing the white linear pattern 110b. The images are grouped together, and the gray line images appearing at the boundary between the black line image and the white line image are grouped together. The gray line image changes its thickness in accordance with the amount of focus shift, and becomes thinner in a focused state and thicker in a defocused state.

  By performing such rearrangement, it is possible to obtain constant analysis data regardless of the image pattern. That is, the image in the measurement range 135 and the image in the measurement range 133 in FIG. 14 are a series of black → gray → white regardless of the number and inclination of the black linear patterns 110a included in the image. It is possible to obtain constant analysis data based on color change.

  Step 4 (P4): The analysis data sorted in Step 3 is rotated by a predetermined amount. This is for enabling processing by a conventionally used SFR calculation program. In the conventional SFR calculation program. When the monochrome pattern on the image matches the pixel, the image in the measurement range read from the image obtained by photographing the graphic with different image heights is rotated by 8 ° in order to prevent a problem that the resolution increases in a pseudo manner. Therefore, in order to use the conventional SFR calculation program, the rotation angle is chucked and the analysis data needs to be rotated. FIG. 17 is a graph showing the relationship between the lens unit position with respect to the imaging sensor and the SFR measured using the resolution measurement chart of FIG. 1 at a certain image height position.

  Step 5 (P5): Finally, a defocus measurement process is performed to determine the focal length of each image height position (focal length for each image height). As described above, the calculated focal length and each image height position are determined. An image plane tilt angle is obtained by performing a reverse calculation with a trigonometric function from the pixel pitch distance on the image sensor 3.

  After that, the image plane tilt angle obtained in this way is given to the lens unit 2 or the image sensor 3 as described above, the focal lengths for the respective image heights are aligned, and the normal of the image plane of the image sensor 3 and the photographic lens. Adjustment is made so that the optical axis of 10 is parallel (corrects one blur).

  As described above, in the present embodiment, the resolution measurement chart 100 in which the resolution measurement pattern 110 including the striped pattern is arranged on the entire plane as the resolution measurement chart for measuring the resolution by image height. Use. As a result, the image data of the measurement range of the fixed coordinates determined as the image height position is extracted from the image data obtained by photographing the resolution measurement chart 100, so that the focal length of each image height position (the focal length for each image height). ).

  Since the measurement range can be fixed coordinates, there is no need to search the entire shooting area as in the case where the measurement range changes, and it is possible to measure at the true image height position, so it is also necessary to correct the focal length In addition, the positional relationship between the lens unit 2 and the image sensor 3 can be adjusted at high speed.

  In addition, as described above, by sorting and rotating the image data taken out at the measurement positions according to the image height, the image data can be processed with the same SFR calculation program as the current method, and compatibility can be maintained.

[Summary]
A resolution measurement chart according to an aspect of the present invention is a resolution measurement chart (100) for measuring resolutions according to image heights in a camera module (1) including a lens unit (2) and an imaging sensor (3). The marker graphic (105, 106) for detecting the center coordinates of the resolution measurement chart, the black linear pattern (110a), and the white linear pattern (110b) are used for the resolution measurement. And a striped resolution measurement pattern (110) alternately arranged over the entire plane of the chart.

  According to the above configuration, when the image data of the measurement range at the image height position is extracted from the image data obtained by photographing the resolution measurement chart, the measurement range for each image height can be set as a fixed coordinate. As a result, it is not necessary to search the entire shooting area as in the case where the measurement range changes, and since it is possible to measure at the image height position that is truly desired, there is no need to correct the focal length, and the lens can be moved at high speed. The positional relationship between the unit and the image sensor can be adjusted.

  A resolution measurement method according to an aspect of the present invention uses a resolution measurement chart (100) according to an aspect of the present invention to measure resolution for each image height of a camera module (1) that is a resolution measurement target. In the measurement method, the step of inputting image data of a chart image obtained by photographing the resolution measurement chart with the camera module (1), and the image data of the chart image and the fixed coordinates in the imaging sensor of the camera module are predetermined. An image extraction step for extracting image data of each measurement range for each image height, a rearrangement step for rearranging the extracted image data for each measurement range in order of pixel values, and rearranged image data And an SFR calculating step for obtaining SFR from the above.

  According to the said structure, the resolution according to image height can be easily measured using the chart for resolution measurement of this invention.

  In this case, it is more preferable to further include a rotation step of rotating the rearranged image data by a predetermined angle, and in the SFR calculation step, the rearrangement is performed on the rotated image data.

  With this configuration, it is possible to use a conventionally used SFR arithmetic processing program.

  The position adjustment method in the camera module (1) according to one aspect of the present invention is obtained by determining the focal length for each image height of the camera module (1) using the resolution measurement method according to one aspect of the present invention. The positions of the lens unit (2) and the imaging sensor (3) provided in the camera module are adjusted based on the focal length for each image height.

  The manufacturing method of the camera module (1) according to one aspect of the present invention is the same as the position adjustment method in the camera module (1) according to one aspect of the present invention, in which the positions of the lens unit (2) and the imaging sensor (3) are determined. It is characterized by being used in the adjusting step.

  According to the above-described position adjustment method in the camera module and the camera module manufacturing method using the same, the positional relationship between the lens unit and the image sensor can be adjusted in a short time, and the time required for manufacturing the camera module can be shortened. .

[Example of software implementation]
Steps 1 to 5 in FIG. 13 are performed by a control block (not shown) of the personal computer (PC) 4, but are realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like. Alternatively, it may be realized by software using a CPU (Central Processing Unit).

  In the latter case, the apparatus that performs Steps 1 to 5 in FIG. 13 stores a CPU that executes instructions of a program that is software that realizes each function, and the program and various data are readable by a computer (or CPU). In addition, a ROM (Read Only Memory) or a storage device (these are referred to as “recording media”), a RAM (Random Access Memory) for expanding the program, and the like are provided. And the objective of this invention is achieved when a computer (or CPU) reads the said program from the said recording medium and runs it. As the recording medium, a “non-temporary tangible medium” such as a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, or the like can be used. The program may be supplied to the computer via an arbitrary transmission medium (such as a communication network or a broadcast wave) that can transmit the program. The present invention can also be realized in the form of a data signal embedded in a carrier wave in which the program is embodied by electronic transmission.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can be used for manufacturing a camera module mounted on a mobile phone, a smartphone, or the like.

DESCRIPTION OF SYMBOLS 1 Camera module 2 Lens unit 3 Image sensor 4 Personal computer 10 Shooting lens 11 Lens barrel 12 Image sensor 30 Measurement range 100 Resolution measurement charts 105 and 106 Marker figure 110 Resolution measurement pattern

Claims (5)

A resolution measurement chart for measuring resolution according to image height in a camera module including a lens unit and an imaging sensor,
A marker figure for detecting the center coordinates of the resolution measurement chart;
A resolution measurement chart comprising: a striped resolution measurement pattern in which a black linear pattern and a white linear pattern are alternately arranged over the entire area of the resolution measurement chart. A resolution measurement method for measuring a resolution for each image height of a camera module that is a resolution measurement object using the resolution measurement chart according to claim 1,
Inputting image data of a chart image obtained by photographing the resolution measurement chart with a camera module;
An image extracting step of extracting image data of each measurement range for each image height determined in advance by fixed coordinates in the image data of the chart image or an image sensor of the camera module;
A rearrangement step of rearranging the image data of each extracted measurement range by rearranging the pixel values in ascending order;
And a SFR calculation step for obtaining SFR (Spatial Frequency Response) from the rearranged image data.   The resolution measuring method according to claim 2, further comprising a rotating step of rotating the rearranged image data by a predetermined angle, wherein the rearrangement is performed on the rotated image data in the SFR calculating step.   The focal length for each image height of the camera module is determined using the resolution measuring method according to claim 2, and the lens unit and the imaging unit provided in the camera module based on the calculated focal length for each image height A position adjustment method in a camera module, characterized by adjusting a position with a sensor.   A method for manufacturing a camera module, wherein the camera module position adjusting method according to claim 4 is used in a step of adjusting a position between a lens unit and an image sensor.