WO2023145688A1 - Imaging device test chart and evaluation method, and recording medium - Google Patents

Abstract

The present invention provides: an imaging device test chart and evaluation method that make it possible to easily evaluate the resolution of an imaging device; and a recording medium.　A test chart (10) comprises a base member (11) and first indicator groups (12) which include indicators (13) that are a plurality of types of symbols of differing sizes and that are formed on the base member (11) and/or size symbols (14) that indicate the size of the indicators (13). The first indicator groups (12) are provided in a center region (11A) that includes the center of the base member and in a peripheral region (11B) that is positioned further outward than the center region (11A).

Description

Imaging device test chart, evaluation method, and recording medium

The present invention relates to a test chart and evaluation method for an imaging device, and a recording medium.

An imaging device that captures an image of a subject using an imaging lens and an image sensor is widely used. In the evaluation system described in Patent Literature 1, a computer or the like evaluates the performance of an imaging device using a test chart image obtained by imaging a test chart including a plurality of characters with an imaging device. Also, an evaluation image is generated that expresses the evaluation of the evaluation unit at each position on the test chart image in color, and the evaluation image is displayed on the display unit side by side with the test chart image or superimposed on the test chart image.

In addition, in the inspection sheet of the imaging device described in Patent Document 2, the resolution inspection chart and the color inspection chart are formed on the same base member. The resolution inspection chart and color inspection chart of this inspection sheet are imaged by an imaging device to be inspected, and the image obtained by this imaging is inspected.

WO2018/051949 JP-A-2006-74556

An embodiment according to the technology of the present disclosure provides a test chart and an evaluation method for an imaging device that can easily evaluate the resolution of the imaging device, and a recording medium.

A first aspect of the technology of the present disclosure includes a base member and an index group, and the index group is arranged in a central region including the center of the base member and a peripheral region located outside the central region. be. The index group is formed on the base member and is a test chart of the imaging device including indices that are symbols of different sizes and/or size symbols that indicate sizes of the indices.

A second aspect of the technology of the present disclosure is a first mark frame including a first mark frame surrounding a group of indicators arranged in a central area and a second mark frame surrounding a group of indicators arranged in a peripheral area. 4 is a test chart for the imaging device of the embodiment;

A third aspect according to the technology of the present disclosure is a test chart of the imaging device of the first aspect or the second aspect in which the index group is arranged along an arc at a constant distance from the center of the base member. A fourth aspect of the technology of the present disclosure is the test chart of the imaging device of the first aspect or the second aspect in which the index group is arranged along the radial direction from the center.

A fifth aspect of the technology of the present disclosure is the same as the first aspect to the fourth aspect, in which at least two indicators and/or size symbols of the same size are arranged at positions where the distances from the center are substantially the same. 4 is a test chart for an imaging device according to any one aspect;

In a sixth aspect of the technology of the present disclosure, the index group includes a first index group in which indexes whose size increases stepwise are arranged in a first direction, and an index whose size increases step by step is arranged in the first direction. 10 is a test chart of the photographing device according to any one of the first to third aspects including a second index group arranged in a second direction different from the direction.

A seventh aspect according to the technology of the present disclosure is the third to sixth aspects, including the second aspect and the second aspect, in which the area of the base member excluding the area surrounded by the mark frame is plain. 4 is a test chart of the imaging device according to any one aspect of . According to an eighth aspect of the technology of the present disclosure, the resolution can be measured by analyzing captured image data when an image is captured by an imaging device in an area other than the area surrounded by the mark frame in the base member. 10 is a test chart of an imaging apparatus according to any one of third to sixth aspects including the second aspect in which a pattern for evaluating resolution is formed, and the second aspect.

A ninth aspect of the technology of the present disclosure is a test chart of an imaging device according to any one of the first to eighth aspects, in which the index and the corresponding size symbol are arranged adjacent to each other. be. A tenth aspect of the technology of the present disclosure is a test chart of an imaging device according to any one of the first to ninth aspects in which the size symbol is the number of points.

An eleventh aspect of the technology of the present disclosure is a test chart for an imaging device according to any one of the first to tenth aspects, wherein the size of the index is 5 or more and 28 or less. . Furthermore, a twelfth aspect of the technology of the present disclosure is a test chart for the photographing device according to any one of the first aspect to the tenth aspect, wherein the size of the index is 7 or more and 17 or less. is. According to a thirteenth aspect of the technology of the present disclosure, the index group includes a first number of indices having a size larger than a first threshold, and a second number of indices having a size smaller than the first threshold greater than the first number. It is a test chart of the imaging device according to any one of the first to twelfth aspects. A fourteenth aspect of the technology of the present disclosure is a test chart for an imaging device according to any one of the first to thirteenth aspects, wherein the index group includes a full-size index corresponding to the size symbol. be.

According to a fifteenth aspect of the technology of the present disclosure, when an area including the center of the smallest rectangular frame surrounding the first index group is set as the central area of the first index group, the first index group A first to a fourteenth aspect, wherein a plurality of central regions of the groups are arranged at equal intervals in the third direction or the fourth direction, and a plurality of the first index groups are arranged without overlapping each other. 4 is a test chart of the imaging device according to any one aspect of .

A test chart for an imaging device of a sixteenth aspect according to the technology of the present disclosure includes a first index group arranged in a central area, a first index group arranged in a peripheral area, indices included, and/or sizes FIG. 10 is a test chart of the photographing device according to any one of the first to fifteenth aspects having the same symbols; FIG.

According to a seventeenth aspect of the technology of the present disclosure, the first index group arranged in the central region and the first index group arranged in the peripheral region include first indices and/or different size symbols. 14 is a test chart of the photographing device according to any one of modes 1 to 15;

According to an eighteenth aspect of the technology of the present disclosure, the first index group arranged in the peripheral area includes an index larger in size and/or a size symbol than the first index group arranged in the central area. 4 is a test chart of the photographing device according to the aspect of .

A nineteenth aspect of the technology of the present disclosure is an evaluation method for imaging the test chart with an imaging device and evaluating the resolution of the imaging device using the captured image data, wherein the test chart is imaged with the imaging device. At this time, one or more test charts are imaged according to the angle of view of the imaging device, and the resolution is determined based on the readable minimum size index and/or the size symbol among the first index group imaged by the imaged image data. is an evaluation method for evaluating

A twentieth aspect according to the technology of the present disclosure is the evaluation method of the nineteenth aspect, in which when the test charts are captured by the imaging device, the number of test charts corresponding to the angle of view of the imaging device is arranged side by side.

A twenty-first aspect of the technology of the present disclosure is a recording medium on which image data of the test chart is recorded.

According to the present invention, it is possible to simply evaluate the resolution of an imaging device.

FIG. 4 is a front view of a test chart of the imaging device according to the first embodiment; FIG. 4 is an enlarged front view enlarging the vicinity of the central region of the test chart; FIG. 4 is an explanatory diagram for explaining the arrangement of index groups by enlarging a part of the test chart; It is the enlarged front view (A) which expanded the center area|region of a test chart, and the enlarged front view (B) which expanded the peripheral area|region of a test chart. 1 is a perspective view of a camera system and a test chart when evaluating the resolution of the camera system; FIG. 1 is a block diagram showing the configuration of a camera system; FIG. It is the front which shows an example of a test chart image. It is an enlarged view in which a part of the test chart image is enlarged, and is an enlarged view (A) corresponding to the central area of the test chart and an enlarged view (B) corresponding to the peripheral area of the test chart. It is a front view of a test chart of the imaging device in the first modification. FIG. 11 is a front view of a test chart of an imaging device in a second modified example; FIG. 11 is a front view of a test chart of an imaging device in a third modified example; FIG. 11 is a front view of a test chart of the imaging device according to the second embodiment; FIG. 11 is a front view of a test chart of an imaging device in a fourth modified example; FIG. 21 is a front view of a test chart of an imaging device in a fifth modified example; FIG. 12 is a front view of a test chart of the imaging device according to the third embodiment; FIG. 21 is a front view of a test chart of an imaging device in a sixth modified example; FIG. 21 is a front view of a test chart of an imaging device in a seventh modified example; FIG. 11 is a front view of a test chart of an imaging device according to a fourth embodiment; FIG. 21 is a front view of a test chart of an imaging device in an eighth modified example; FIG. 20 is a front view of a test chart of an imaging device in a ninth modified example; FIG. 21 is a front view of a test chart of an imaging device in a tenth modified example; 1 is a perspective view of a camera system and a test chart when evaluating the resolution of the camera system using a telephoto interchangeable lens; FIG. 1 is a perspective view of a camera system and a test chart when evaluating the resolution of the camera system using a standard interchangeable lens; FIG. 1 is a perspective view of a camera system and a test chart when evaluating the resolution of the camera system using a wide-angle interchangeable lens; FIG.

[First embodiment]
FIG. 1 is a front view of a test chart 10 showing one embodiment of the present invention. The test chart 10 has a base member 11 and a first index group 12 . The base member 11 is, for example, a rectangular sheet of A3 size, which is plain paper for a printer. Further, in order to match the screen of the captured image captured by the camera system 100 described later, the test chart 10 uses the long side direction as the horizontal direction and the short side direction as the vertical direction. The same applies to subsequent embodiments.

The first indicator group 12 is formed on the base member 11 and includes indicators 13 that are symbols of a plurality of types of different sizes, and size symbols 14 that indicate sizes of the indicators 13 . Here, "formed on the base member 11" means that characters, symbols, symbols, and shapes are represented by printing on one surface of the base member 11. FIG. In the test chart 10 of the example shown in FIG. 1, there are 5 rows in the X-axis direction (the long side direction of the base member 11) and 5 columns in the Y-axis direction (the short side direction of the base member 11), a total of 25 first indicators. A group 12 is formed.

Hereinafter, descriptions such as the first index group 12, the second index group 12A, the third index group 12B, the first index group 12C, 12D, . . . 12A, 12B, 12C, 12D, . . . The index group arranged at the position of will be explained.

The area surrounded by broken lines in FIG. 1 is a central area 11A including the center CP0 on the base member 11, and the first indicator group 12 is arranged in this central area 11A. The index 13 surrounded by the dashed line and the size symbol 14 are one first index group 12 in this embodiment. In the following description, the term "center" also includes "substantially the center" including errors. Although the base member 11 actually has a thickness, the center CP0 on the base member 11 is the center of a two-dimensional plane when the portion where the first index group 12 is written is viewed from above. Further, the first index group 12 is also arranged in the peripheral area 11B located outside the central area 11A, that is, outside the area surrounded by the dashed line in FIG. In FIG. 1, for convenience of explanation, a dot indicating the center CP0 and a dashed line indicating the central region 11A are arranged, but in reality, such dots and dashed lines may be omitted.

FIG. 2 is an enlarged view of a portion including the center region 11A of the test chart 10 of the example shown in FIG. The index 13 is a symbol as described above, and the symbol here includes characters and codes. In this embodiment, the index 13 includes an alphabet, that is, one of the 26 uppercase and lowercase letters in English, and brackets [ ], which are symbols surrounding characters. A size symbol 14 is a number indicating a size. The index 13 and the corresponding size symbol 14 are arranged side by side.

The size symbol 14 is the number of points. The number of points referred to here is, for example, the number of points of the JIS standard and the size. Also, the line width is proportional to the size. In the present embodiment, the first index group 12 includes the index 13 from 2 points to 28 points and the size symbol 14 indicating the size of the index 13, that is, the number of points.

As shown in FIG. 2, for example, an indicator 13 having a size of 28 points and a size symbol 14 indicating the size of the indicator 13 are arranged at a position of a distance L11 from the center CP0 of the base member 11. As shown in FIG. Further, for example, an index 13 having a size of 8 points and a size symbol 14 indicating the size of the index 13 are arranged at a position of a distance L12 from the center CP0. Thus, in the test chart 10, at least two indicators 13 and size symbols 14 of the same size are arranged at positions where the distances from the center CP0 of the base member 11 are the same. As a result, when determining the resolution of the camera system 100, which will be described later, even if it is difficult to determine one of the indicators 13 having the same size and having the same distance from the center CP0, the other indicators 13 are checked. You may be able to make the right decision. It should be noted that "the distance is the same" means that the distance is substantially the same. Here, “substantially the same” means a range in which it can be determined that the image heights are substantially the same. Note that "the index 13 or the size mark 14 is arranged at a specific position" means that the reference position of the index 13 or the size mark 14 is determined and the reference position is arranged at the specific position. For example, when the center position of the smallest rectangle surrounding one index 13 or size symbol 14 is set as a reference position, and the reference position is placed at a specific position, it means that "the index 13 or size symbol 14 It means "to be distributed to". That is, "the index 13 or the size symbol 14 is arranged at a specific position" does not necessarily mean that the black portion of the index 13 or the size symbol 14 is positioned at the specific position. Also, the "distance from the center CP0" is the distance from the center CP0 to the reference position. For example, the distance from the center CP0 to the center position of the smallest rectangle surrounding one index 13 or size symbol 14 is the "distance from the center CP0".

Also, the brackets [] included in the index 13 are full-size indexes corresponding to size symbols. Note that the full-size index 13 is not limited to the brackets [ ] described above, and means symbols of the maximum size that can be expressed when the number of points is determined, such as ( )/.

When determining the resolution of the camera system 100, which will be described later, it is necessary to determine the minimum size index 13 that can be read from the captured image captured by the camera system 100. For this reason, it is preferable that the size of the index 13 is at least two types (multiple types). Furthermore, in order to determine the resolution step by step, the size of the index 13 is preferably 5 or more and 28 or less, more preferably 7 or more and 17 or less. In addition, the index 13 may be arranged by changing the size by one point, but from the viewpoint of efficient arrangement, it is possible to use the index 13 that differs in size by one point for characters of a predetermined value (for example, 10 points) or less. Preferably, characters larger than a predetermined value (e.g. 10 points) are indexed 13 that differ in size by 2 points, and characters larger than another predetermined value (e.g. 20 points) are indexed 13 that are different in size by 4 points. is preferred.

In addition, with respect to the indices 13 included in the first index group 12, the number (second number) of indices smaller in size than the threshold with a certain threshold (first threshold) as the boundary is the index in which the size is larger than the threshold. Preferably, the number is greater than 13 (the first number). In the evaluation method using the test chart 10, the smaller the readable index 13, the higher the resolution of the imaging device. Because you can.

FIG. 3 is an enlarged view of a portion of the test chart 10 of FIG. 1 with a minimum rectangular frame 15 (a frame indicated by a two-dot chain line) surrounding the first index group 12 . If the area including the center CP1 of the smallest rectangular frame 15 surrounding the first index group 12 is the central area of the first index group 12, the center CP1 of the first index group 12 is in the X-axis direction (third direction ) at equal intervals L21 and in the Y-axis direction (fourth direction) at equal intervals L22, and the plurality of first index groups 12 are arranged without overlapping each other. It should be noted that the equidistant intervals between the central regions may be the equidistant intervals between the centers CP1, or the equidistant intervals between the other points included in the central region. In FIG. 3, for convenience of explanation, a point indicating the center CP1 and the smallest rectangular frame 15 surrounding the first index group 12 are arranged, but they may not actually be present.

FIG. 4 is an enlarged view (FIG. 4(A)) enlarging the central area in the test chart 10 of FIG. 1 and an enlarged view (FIG. 4(B)) enlarging the peripheral area. Note that the peripheral area shown in FIG. 4B is specifically an area including the first index group 12 positioned at the left corner of the test chart 10, that is, at the topmost and leftmost position.

In the test chart 10, the first index group 12 consists of a second index group 12A in which the indexes 13 whose size increases step by step are arranged in the positive direction (first direction) of the X axis, and a second index group 12A whose size increases step by step. and a third index group 12B in which the indices 13 are arranged in the negative direction (second direction) of the X-axis. As a result, more indicators 13 and size symbols 14 can be efficiently arranged on the base member 11 . Here, the positive direction of the X-axis is the direction from the left side to the right side of the base member 11, and the negative direction of the X-axis is the direction from the right side to the left side of the base member 11, which is the positive direction of the X-axis. in the opposite direction. The first direction in which the indicators 13 included in the second index group 12A are arranged may be different from the second direction in which the indicators 13 included in the third indicator group 12B are arranged.

As shown in FIG. 4A, the sizes of the indices 13 included in the first index group 12 arranged in the central region range from 2 points to 28 points, and the characters used for the indices 13 range from a to z. , capital letters A, B, G, H, U, and parentheses [ ]. On the other hand, as shown in FIG. 4B, the sizes of the indices 13 in the first index group 12 arranged in the peripheral area range from 2 points to 28 points, and the characters used for the indices 13 range from a to z. , capital letters A, G, I, P, U, and W, and parentheses [ ]. ing. That is, the first index group 12 arranged in the central area and the first index group 12 arranged in the peripheral area have the same size of the included indexes 13 and the same size symbols 14, but the characters used for the indexes 13 are the same. different.

The first index group 12 arranged in the central area and the first index group 12 arranged in the peripheral area are not limited to this, and the indexes 13 and/or the size symbols 14 included in the first index group 12 are the same. or the indices 13 and/or size symbols 14 included may be different.

When determining the resolution of the camera system 100, which will be described later, it is necessary to determine the minimum readable size index 13. If the indices 13 and the size symbols 14 included in the first index group 12 arranged in the central region and the first index group 12 arranged in the peripheral region are the same, and the arrangement order is also the same, The user may memorize the indices and the size symbols 14 included in the first index group 12, including the arrangement order. Therefore, the user may feel as if he or she has read the size index 13 that has been stored once, and may make an erroneous judgment. On the other hand, in the test chart 10, as described above, the first index group 12 arranged in the central area and the first index group 12 arranged in the peripheral area use different characters for the indexes 13. Therefore, the minimum readable size index 13 can be accurately determined.

As shown in FIG. 5, when evaluating the resolution of the camera system 100, the camera system 100 images the test chart 10. FIG. The camera system 100 obtains a test chart image 20 that is a captured image of the test chart 10 . Note that the test chart image 20 in FIG. 5 shows what is displayed on the display unit 104 of the camera system 100 . In this case, the imaging optical system 112 (see FIG. 6) of the camera system 100 is opposed to the surface of the test chart 10 on which the first index group 12 is formed. Then, the camera system 100 is evaluated using the test chart image obtained by imaging the test chart 10 . Note that the camera system 100 corresponds to an imaging device in the claims.

The camera system 100 includes a camera body 101 and an interchangeable lens 102. The camera system 100 is a so-called mirrorless single-lens digital camera. As the interchangeable lens 102, there are a plurality of types, such as a standard lens, a wide-angle lens, and a telephoto lens, as will be described later.

The camera body 101 includes a release switch 103, a display section 104, operation buttons 105, and the like. A mount 106 (see FIG. 6) is provided on the front surface of the camera body 101 . A plurality of types of interchangeable lenses 102 are selectively attached to the mount 106 . An imaging device 107 (see FIG. 6) is provided behind the mount 106 .

The display unit 104 is used to display live view images, captured images, setting menus, and the like. A touch panel 108 is laminated on the surface of the display unit 104, and the touch panel 108 and the plurality of operation buttons 105 are used for various setting operations. The display unit 104 is composed of, for example, an LCD panel. Input instructions from the release switch 103, the operation button 105, and the touch panel 108 are transmitted to the body control unit 131 (see FIG. 3).

As shown in FIG. 6, the interchangeable lens 102 includes a lens barrel section 111, an imaging optical system 112, a focus ring 113, an aperture operation ring 114, a zoom ring 115, a lens mount 116, and the like. The lens barrel portion 111 has a cylindrical shape and accommodates an imaging optical system 112 therein, and a lens mount 116 is provided at the rear end thereof. The imaging optical system 112 forms an image of subject light on the imaging element 107 when the interchangeable lens 102 is attached to the camera body 101 . The imaging device 107 captures the light emitted from the interchangeable lens 102 .

The lens mount 116 is detachably coupled to the mount 106 of the camera body 101 . The lens mount 116 is provided with a lens-side signal contact 116A. Inside the mount 106, a body-side signal contact 106A is provided. When the lens mount 116 of the interchangeable lens 102 is coupled to the mount 106 of the camera body 101, the lens-side signal contact 116A comes into contact with the body-side signal contact 106A, electrically connecting the interchangeable lens 102 and the camera body 101. Connecting.

The interchangeable lens 102 includes an imaging optical system 112, a focus ring 113, an aperture operation ring 114, a zoom ring 115, and the like, as well as a lens control unit 117, a motor driver 118, motors 119 and 121, a zoom mechanism 122, sensors 123 and 124, and the like. Prepare.

The lens control unit 117 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores programs and parameters used by the CPU, and a RAM (Random Access Memory) that is used as a work memory for the CPU. (not shown), etc., and controls each part of the interchangeable lens 102 . A motor driver 118 and sensors 123 and 124 are connected to the lens controller 117 .

The imaging optical system 112 includes a plurality of lenses including a focus lens 125 and a variable magnification lens 126, an aperture unit 127, and the like. The focus lens 125 is driven by the motor 119 to move in the direction of the optical axis L to adjust the shooting distance. The diaphragm unit 127 moves a plurality of diaphragm blades 127A by driving the motor 121 to change the amount of light incident on the image pickup device 107 . A motor driver 118 controls driving of the motors 119 and 121 based on the control of the lens control section 117 .

The zoom mechanism 122 is a manual zoom mechanism that converts the rotational movement of the zoom ring 115 into linear movement to move the variable power lens 126 . The zoom lens 126 is driven by the zoom mechanism 122 to move in the direction of the optical axis L to change the angle of view. Note that the zoom mechanism 122 is not limited to this, and may have a configuration in which the rotation position of the zoom ring 115 is detected by a sensor, and the zoom lens 126 is moved by a motor or the like according to information on the rotation direction and rotation amount.

The camera main body 101 includes the above-described release switch 103, display unit 104, operation buttons 105, imaging device 107, touch panel 108, etc., as well as a main body control unit 131, a shutter unit 132, a motor driver 133, a shutter motor 134, an image memory 135, and the like. , an image data processing unit 136 , an AF (Autofocus) processing unit 137 , a display control unit 138 , a card I/F (Interface) 139 , etc. These are connected by a bus line 141 .

The body control unit 131 includes a CPU, a ROM that stores programs and parameters used by the CPU, and a RAM that is used as a work memory for the CPU (none of which is shown). The body control unit 131 controls each part of the camera body 101 and the interchangeable lens 102 connected to the camera body 101 . A shutter signal is input from the release switch 103 to the body control unit 131 . Also, the body side signal contact 106A is connected to the body control section 131 .

The body control unit 131 transmits to the lens control unit 117 a control signal for moving the focus lens 125 in accordance with information about the rotation direction and amount of rotation of the focus ring 113 detected by the lens control unit 117 . The lens controller 117 controls the motor driver 118 based on the control signal to move the focus lens 125 .

The body control unit 131 operates the aperture unit 127 according to the rotational position information of the aperture operation ring 114 detected by the lens control unit 117, and transmits a control signal for changing the aperture diameter to the lens control unit 117. The lens control unit 117 controls the motor driver 118 based on the control signal from the body control unit 131, and controls the aperture diameter of the aperture unit 127 so that the aperture value corresponding to the rotational position of the aperture operation ring 114 is obtained. .

The shutter unit 132 is arranged between the mount 106 and the imaging device 107 . The shutter unit 132 is provided so as to be able to block the optical path between the imaging optical system 112 and the imaging device 107, and changes between an open state and a closed state. The shutter unit 132 is in an open state during live view image and moving image shooting. The shutter unit 132 temporarily changes from an open state to a closed state during still image shooting. This shutter unit 132 is driven by a shutter motor 134 . A motor driver 133 controls driving of the shutter motor 134 .

The imaging element 107 is driven and controlled by the main body control section 131 . The imaging element 107 constitutes an imaging section together with the shutter unit 132, the image data processing section 136, and the like. The imaging unit performs imaging with the interchangeable lens 102 attached to the mount 106 . The imaging device 107 is, for example, an APS-C (Advance Photo System-classic) size CMOS (Complementary Metal Oxide Semiconductor) image sensor, and is composed of a plurality of pixels (not shown) arranged in a two-dimensional matrix. has a light-receiving surface. Each pixel includes a photoelectric conversion element, and photoelectrically converts a subject image formed on the light receiving surface by the interchangeable lens 102 to generate an imaging signal. In addition, the image sensor 107 has an electronic shutter function, and the shutter speed (charge accumulation time) can be adjusted.

The imaging device 107 also includes signal processing circuits (none of which are shown) such as a noise elimination circuit, an auto gain controller, and an A/D conversion circuit. The noise removal circuit applies noise removal processing to the imaging signal. The auto gain controller amplifies the level of the imaging signal to an optimum value. The A/D conversion circuit converts the imaging signal into a digital signal and outputs the digital signal from the imaging element 107 to the bus line 141 . The output signal of the image sensor 107 is image data (so-called RAW data) having one color signal for each pixel.

The image memory 135 stores one frame of image data output to the bus line 141 . The image data processing unit 136 reads one frame of image data from the image memory 135 and performs known image processing such as matrix calculation, demosaicing, γ correction, luminance/color difference conversion, and resizing. The AF processing unit 137 calculates an AF evaluation value, which is an integrated value of high frequency components, from image data for one frame. This AF evaluation value corresponds to the contrast of the image. In the AF mode, the body control unit 131 determines the position of the focus lens 125 ( focus position). The body control unit 131 moves the focus lens 125 to the detected in-focus position. In this way, focus adjustment is automatically performed without user's operation.

The display control unit 138 sequentially inputs image data for one frame image-processed by the image data processing unit 136 to the display unit 104 . The display unit 104 sequentially displays the live view images at regular intervals. The card I/F 139 is incorporated in a card slot (not shown) provided in the camera body 101, and electrically connects with the memory card 142 inserted into the card slot. The card I/F 139 stores the image data image-processed by the image data processing unit 136 in the memory card 142 . Further, when reproducing and displaying the image data stored in the memory card 142 , the card I/F 139 reads out the image data from the memory card 142 .

An evaluation method for evaluating the resolution of the camera system 100 using the test chart 10 will be described. First, as described above, the imaging optical system 112 (see FIG. 6) of the camera system 100 is opposed to the surface of the test chart 10 on which the first index group 12 is formed, and an image is captured. The user adjusts the imaging distance (the distance between the test chart 10 and the camera system 100) while watching the live view image displayed on the display unit 104, for example. In this case, the user adjusts the imaging distance according to the imaging angle of view of the camera system 100 in order to capture the test chart 10 in the full screen of the captured image.

Also, the user rotates the focus ring 113 to adjust the focus, or rotates the aperture operation ring 114 to adjust the aperture value. Also, the shutter speed of the shutter unit 132 is adjusted by operating the operation button 105 of the camera body 101 . At this time, it is preferable to set the exposure value, which is the combination of the aperture and shutter speed, to the standard value.

After adjusting the imaging distance, the user presses the release switch 103 . When a shutter signal is input from the release switch 103, the body control unit 131 controls the shutter unit 132, the image sensor 107, the image data processing unit 136, and the like to generate a test chart image, which is a captured image of the test chart 10. 20 (see FIGS. 5 and 7). The test chart image 20 obtained by imaging is, for example, stored in the memory card 142 and then reproduced and displayed on the display unit 104 .

Then, the user evaluates the camera system 100 using the test chart image 20 displayed on the display unit 104 . Alternatively, a display may be prepared separately from the camera system 100, connected to the camera system 100, and the test chart image may be displayed on the display for evaluation.

7 shows an example of a test chart image 20 obtained by imaging the test chart 10 with the camera system 100. FIG. The user identifies the smallest size indicator 13 that can be read from the test chart image 20 . It can be determined that the resolution is so high that the small-sized index 13 can be read. Also, since the size symbol 14 corresponding to the index 13 has the same number of points as the index 13, it can be read in the same manner as the index 13, and the user identifies the size of the read index 13, that is, the number of points. be able to.

8A and 8B are enlarged views of a part of the test chart image 20. FIG. 8A corresponds to the central area of the test chart 10 (see FIG. 4A), and FIG. , and an enlarged view corresponding to the peripheral area of the test chart 10 (see FIG. 4B). The user preferably enlarges the test chart image 20 displayed on the display unit 104 or the display as shown in FIGS. 8A and 8B to read it.

As described above, in the evaluation method using the test chart 10, when the test chart image 20 is obtained, the test chart 10 is displayed on the full screen of the captured image. As a result, it is clear that the optical axis L of the imaging optical system 112 and the position of the center CP0 of the test chart 10 match. That is, the portion of the test chart image 20 corresponding to the central region (that is, the image near the center CP0) corresponds to the resolution performance near the optical axis L of the imaging optical system 112 . On the other hand, it can be seen that the portion corresponding to the peripheral area in the test chart image 20 (the image of the portion outside the central area) corresponds to the resolution performance at the image height away from the optical axis L of the imaging optical system 112 .

As shown in FIG. 8(A), in the test chart image 20 corresponding to the central area, the minimum size index 13 that can be read is the index 13 of 5 points. Then, as shown in FIG. 8B, in the test chart image 20 corresponding to the peripheral area, the minimum readable index 13 is the index 13 of 6 points.

A simple relationship between the minimum size index 13 that can be read and the resolution performance (high resolution) of the imaging device is as follows.
2 points or less: excellent 3 points or less: excellent 4-5 points: standard 6 points or more: problem with resolution

Comparing the results read from the test chart image 20 with the above relationship, it can be seen that the resolution of the camera system 100 is normal near the optical axis L, and that there is a problem with the resolution in the image height portion away from the optical axis L. I understand. In this manner, by reading the test chart image 20 obtained by imaging the test chart 10 including the first index group 12 including the plurality of types of indexes 13 and the size symbol 14 indicating the size of the index 13, the imaging apparatus resolution can be easily evaluated.

Furthermore, by using a conversion formula from the minimum size of the index 13 read from the test chart image 20, a specific resolution value can be known. A discussion of conversion to resolution follows. As a premise, first, the print resolution on the test chart 10 is calculated. The printing resolution is the resolution required to correctly reproduce symbols of a certain number of points when printing symbols such as characters. It has the relationship of (1).
Y=9/P (1)
In other words, if the print resolution is equal to or higher than Y that satisfies this formula (1), the symbol with the number of points P can be reproduced correctly. By using this formula (1), it can be substituted for the resolution of the test chart 10 itself.

Conventionally, the resolution (lines/mm) of an imaging device equipped with an imaging optical system was evaluated by measuring the extent to which alternately arranged black and white lines could be separated and photographed. . This is to evaluate the imaging performance of the imaging optical system, and to evaluate how finely an image can be formed on the imaging device. However, with such a conventional evaluation method, when measuring whether the alternating black and white lines can be separated and copied, it is necessary to perform analysis using dedicated software, etc., which is extremely time-consuming. rice field.

Therefore, in the present invention, the test chart image 20 is obtained by capturing the test chart 10 in which the first index group 12 is formed on the base member 11 so as to fill the screen of the captured image. The test chart 10 is formed with indices 13 of various sizes and size symbols 14 that can be converted into resolution (lines/mm). As described above, the smallest sized indicium 13 that can be read from the test chart image 20 is identified. In order to convert the minimum size read from the test chart image 20 into the resolution, it is multiplied by the reduction magnification at which the test chart 10 as the object is imaged on the imaging device 107 . The size of the test chart 10 exemplified in this embodiment is A3 size, and the width is 420 mm. On the other hand, the imaging element 107 in the camera system 100 has a sensor width of 23.5 mm for the above-described APS-C size, so the reduction magnification of the image of the test chart 10 formed on the imaging element 107 is 420/23.5=17. .87. It should be noted that even with image sensors other than the APS-C size, the reduction ratio may be inversely proportional to the sensor width. 0.67, and a medium format image sensor has a sensor width of 43.8 mm, so the reduction ratio should be 420/43.8=9.59.

Then, by multiplying the above formula (1) for converting the number of points into the print resolution by the reduction ratio, the resolution on the imaging device on which the test chart 10 is imaged=the resolution of the imaging device can be obtained. In the above example, the APS-C size image pickup device 107 was able to read the index 13 with the point number P of 5 in the A3 size test chart 10 and the size symbol from the test chart image 20, so the resolution of the camera system 100 is ( 9/5)×(420/23.5)=32.2 (lines/mm).

As described above, in the test chart and evaluation method of the present invention, the minimum size of the index 13 that can be read from the test chart image 20 and a simple conversion formula are used to calculate the resolution of the imaging device, and the resolution can be easily calculated. can be evaluated.

[First modification]
In the above-described first embodiment, the first index groups 12 in the test chart 10 are arranged at equal intervals in the X-axis direction and the Y-axis direction without overlapping, but the present invention is not limited to this. Instead, as in the test chart 30 shown in FIG. 9, the index 13 and the size symbol 14 are arranged adjacently without a space in the X-axis direction, and the first index group 12 is spaced apart in the Y-axis direction. may be placed. That is, a plurality of first index groups 12 that are adjacently repeated from one end of the base member 11 to the other end in the X-axis direction are spaced apart in the Y-axis direction (29 rows in the example shown in FIG. 9). are distributed. In the above description, for convenience of explanation, the terms "without spacing" and "adjacent to each other" were used, but in FIG. . In other words, "without spacing" and "adjacent" include cases where there is a slight gap, and cases where the index 13 or size symbol 14 partially overlaps to the extent that individual characters can be read. is included. On the other hand, there is a clear gap of a predetermined value or more between the indexes 13 or size symbols 14 in the Y-axis direction. The same applies to the following. Note that the test chart 30 is the same as that of the first embodiment except for the arrangement of the first index group 12, so the description is omitted. Also, the types of the indices 13 and the size symbols 14 are the same as in the first embodiment. The sizes of the indices 13 included in the first index group 12 range from 6 points to 24 points.

Also, in the test chart 30, as in the first embodiment, at least two indexes 13 of the same size and size symbols 14 are arranged at positions where the distances from the center CP0 of the base member 11 are the same. Further, in the test chart 30, as in the first embodiment, the first index group 12 includes the second indexes in which the indexes 13 whose size increases step by step are arranged in the positive direction (first direction) of the X-axis. It includes a group 12A and a third index group 12B in which the indices 13 whose size increases stepwise are arranged in the negative direction (second direction) of the X-axis. In FIG. 9, for convenience of explanation, a point indicating the center CP0 is arranged, but in reality such a point may be omitted.

In this first modification, by using a test chart 30 that includes a first index group 12 that includes indicators 13 that are symbols of a plurality of types of different sizes and size symbols 14 that indicate sizes of the indicators 13, the first As in the embodiment, it is possible to easily evaluate the resolution of the imaging device. Further, similar effects can be obtained in the following second and third modifications.

[Second modification]
As a modification of the first embodiment, the first index group 12 may be arranged as in a test chart 35 shown in FIG. In the test chart 35, as in the first modified example, the index 13 and the size symbol 14 are arranged adjacently with no space in the X-axis direction, and the first index group is spaced in the Y-axis direction. 12, the interval between the first index groups 12 in the Y-axis direction is narrower than in the first modified example. In addition, the first index groups 12 that are adjacent and repeated from one end of the base member 11 to the other end in the X-axis direction are arranged at intervals in the Y-axis direction (70 rows in the example shown in FIG. 10). are distributed. Note that the test chart 35 is the same as that of the first embodiment except for the arrangement of the first index group 12, and the description thereof is omitted. Also, the types of the indices 13 and the size symbols 14 are the same as in the first embodiment. Note that the sizes of the indicators 13 included in the first indicator group 12 are smaller than those in the first modification, and range from 3 points to 10 points.

In addition, in the test chart 35, the indicators 13 and size symbols 14 of the same size are repeatedly arranged not only in the X-axis direction but also in the direction D that is inclined at the inclination angle α with respect to the X-axis direction. The direction D is parallel to the direction from the center CP0 of the base member 11 toward the four corners of the base member 11 . In addition, in FIG. 10, a point indicating the center CP0 is arranged for convenience of explanation, but such a point may be omitted in practice.

[Third Modification]
In the above-described first embodiment, the first index group 12 formed on the base member 11 includes the index 13, which is a symbol of a plurality of different sizes, and the size symbol 14 indicating the size of the index 13. However, the present invention is not limited to this, and as shown in FIG. 11, the first index group 12 may be composed only of size symbols 14 indicating a plurality of different sizes. In this case, the size symbol 14 also serves as the index 13 . That is, it can be determined that the resolution is so high that the size symbol 14 of a small size can be read. Then, the resolution of the imaging device can be simply evaluated from the minimum size of the size symbol 14 that can be read.

[Second embodiment]
In the second embodiment described below, in addition to the configuration of the first embodiment, a test chart in which mark frames are formed on the base member 11 will be exemplified. FIG. 12 is a front view of a test chart 40 showing an example of the second embodiment. In addition to the base member 11 and the first index group 12, the test chart 40 includes a first mark frame 41 and second mark frames 42A and 42B. The first mark frame 41 and the second mark frames 42A and 42B are rectangular frames formed on the base member 11 by printing or the like, similar to the first index group 12 . Note that the configurations of the base member 11 and the first index group 12 are the same as those of the first embodiment, and the description thereof will be omitted. In addition, the first index groups 12 are arranged in a plurality without overlap in the X-axis direction and the Y-axis direction at regular intervals, as in the first embodiment.

The first mark frame 41 surrounds the first index group 12 arranged in the central area 11A. The second mark frames 42A, 42B surround the first index group 12 arranged in the peripheral area 11B. The definitions of the central region 11A and the peripheral region 11B are the same as in the first embodiment. The second mark frame 42A is positioned outside the four corners of the first mark frame 41. As shown in FIG. The second mark frame 42B is positioned further outside the second mark frame 42A and at the four corners of the base member 11 . As a result, when reading the test chart image 20 obtained by capturing the test chart 40, the portion corresponding to the central region (that is, the image near the center CP0) and the portion corresponding to the peripheral region (image of the portion outside the central region) but easy to find.

In this second embodiment, a first index group 12 including indexes 13 which are symbols of different sizes of a plurality of types and size symbols 14 indicating sizes of the indexes 13, a first mark frame 41 and a second mark. By using the test chart 40 having the frames 42A and 42B, in addition to the effects of the first embodiment, the user can search the first mark frame 41 and the second mark frames 42A and 42B as marks. , the portion corresponding to the central area of the test chart 40 and the portion corresponding to the peripheral area of the first index group 12 can be easily found. That is, when the user evaluates the resolution of the imaging device, for example, the resolution can be easily adjusted for the position of the image height desired to be evaluated, such as near the optical axis L of the imaging optical system 112 or a position away from the optical axis L. can be evaluated.

[Fourth Modification]
In the above-described second embodiment, a configuration is illustrated in which a mark frame is added to a test chart in which a plurality of first index groups 12 are arranged at equal intervals in the X-axis direction and the Y-axis direction without overlapping. However, the present invention is not limited to this, and as shown in FIG. A mark frame may be added to the test chart (that is, the test chart 30 shown in FIG. 9) on which the first index group 12 is arranged.

A test chart 43 shown in FIG. 13 includes a first mark frame 44 and second mark frames 45A and 45B in addition to the base member 11 and the first index group 12. The first mark frame 44 and the second mark frames 45A and 45B are rectangular frames formed on the base member 11 by printing or the like, like the first index group 12 . Also, the first index group 12 has the same arrangement as the test chart 30 in the first modified example. Also, the types of each index 13 and size symbol 14 are the same as those of the test chart 30 .

The first mark frame 44 surrounds the first index group 12 arranged in the central area 11A, like the first mark frame 41 in the second embodiment. The second mark frames 45A, 45B surround the first index group 12 arranged in the peripheral area 11B. The definitions of the central region 11A and the peripheral region 11B are the same as in the first and second embodiments. The second mark frame 45</b>A is positioned outside the four corners of the first mark frame 44 . The second mark frame 45B is positioned further outside the second mark frame 45A and at the four corners of the base member 11 .

The first index group 12 surrounded by the first mark frame 44 includes indexes 13 of 6 points to 24 points and size symbols 14 corresponding to the indexes 13 . Similarly, the first index group 12 surrounded by the second mark frames 45A and 45B also includes 6-point to 24-point indexes 13 and size symbols 14 . In addition, in FIG. 13, a point indicating the center CP0 is arranged for convenience of explanation, but such a point may be omitted in practice.

In this fourth modification, a first index group 12 including indexes 13 that are symbols of different sizes of a plurality of kinds and size symbols 14 indicating sizes of the indexes 13, a first mark frame 44 and a second mark By using the test chart 43 having the frames 45A and 45B, as in the second embodiment, when the user evaluates the resolution of the imaging device, for example, near the optical axis L of the imaging optical system 112 or the light It is possible to simply evaluate the resolution of the position of the image height desired to be evaluated, such as the position away from the axis L. Moreover, the same effect can be obtained in the following fifth modified example.

[Fifth Modification]
As a modification of the second embodiment, the first index group 12 and the mark frames may be arranged as in a test chart 46 shown in FIG. In addition to the base member 11 and the first index group 12, the test chart 46 includes a first mark frame 47 and second mark frames 48A and 48B. The first index group 12 has the same arrangement as the test chart 35 of the second modified example. Also, the types of each index 13 and size symbol 14 are the same as those of the test chart 46 .

The first mark frame 47 surrounds the first index group 12 arranged in the central area 11A, like the first mark frame 41 in the second embodiment. The second mark frames 48A, 48B surround the first index group 12 arranged in the peripheral area 11B. The definitions of the central region 11A and the peripheral region 11B are the same as in the first and second embodiments. The second mark frame 48A is positioned outside the four corners of the first mark frame 47. As shown in FIG. The second mark frame 48B is positioned further outside the second mark frame 48A and at the four corners of the base member 11 . In addition, in FIG. 14, a point indicating the center CP0 is arranged for convenience of explanation, but such a point may be omitted in practice.

Further, as in the third modified example, the test chart provided with the first index group 12 formed on the base member 11 and composed only of the size symbols 14 indicating a plurality of types of different sizes may be used in the second embodiment. A first marker frame and a second marker frame similar to may be added.

[Third Embodiment]
In the third embodiment described below, a test chart is illustrated in which the area except the area surrounded by the mark frame is plain from the configuration of the second embodiment. FIG. 15 is a front view of a test chart 50 showing an example of the third embodiment. The test chart 50 includes a base member 11, a first index group 12, a first mark frame 51, and second mark frames 52A and 52B. The first mark frame 51 and the second mark frames 52A and 52B are rectangular frames formed on the base member 11 by printing or the like, like the first index group 12 .

The first mark frame 51 surrounds the first index group 12 arranged in the central area 11A, like the first mark frame 41 in the second embodiment. The second mark frames 52A, 52B surround the first index group 12 arranged in the peripheral area 11B, like the second mark frames 42A, 42B in the second embodiment. The arrangement of the first mark frame 51 and the second mark frame 52A is the same as the first mark frame 41 and the second mark frame 42A in the second embodiment. The second mark frame 52B is arranged outside the second mark frame 52A and in addition to the four corners of the base member 11, and also near the center of the four sides of the base member 11. As shown in FIG. The definitions of the central region 11A and the peripheral region 11B are the same as in the first and second embodiments.

In the test chart 50, the area of the base member 11 other than the area surrounded by the first mark frame 51 and the second mark frames 52A and 52B is plain, that is, nothing is formed. By using such a test chart 46, in addition to the effects of the first and second embodiments, the user is able to It becomes unnecessary to look at the area, and the first index group 12 of the part corresponding to the central area of the test chart 46 and the part corresponding to the peripheral area can be easily found.

[Sixth Modification]
As a modification of the third embodiment, as in a test chart 53 shown in FIG. 16, the first mark frame 51 and the second mark frames 52A and 52B are arranged in the same arrangement as in the third embodiment. , and the configuration of the first index group 12 may be changed. That is, the first index group 12 (hereinafter referred to as the first index group 12C) surrounded by the first mark frame 51 (arranged in the central region 11A) and the second mark frames 52A and 52B The sizes of the indices 13 and the size symbols 14 included in the first index group 12 (hereinafter referred to as the first index group 12D) surrounded (arranged in the peripheral region 11B) are changed.

Specifically, the first index group 12C includes indexes 13 from 2 points to 20 points and size symbols 14 corresponding to the sizes of the indexes 13 . On the other hand, the first index group 12D includes indexes 13 of 2 points to 28 points and size symbols 14 corresponding to the sizes of the indexes 13. FIG. That is, the first index group 12D includes the index 13 and the size symbol 14 that are larger in size than the first index group 12C.

In an imaging device equipped with an imaging optical system, it is common that the resolution at the image height away from the optical axis L of the imaging optical system is lower than the resolution near the optical axis L. That is, it is clear that the minimum size of the index 13 that can be read from the test chart image obtained by imaging with the imaging device is larger in the peripheral area 11B than in the central area 11A. Accordingly, the first index group 12D includes an index 13 and a size symbol 14 having a size larger than those of the first index group 12C, in accordance with such characteristics of the imaging optical system.

Thus, the test chart 53 includes the first index group 12C that matches the characteristics of the imaging optical system, and the first index group 12D that includes the index 13 larger in size than the first index group 12C and the size symbol 14. Therefore, in addition to the effect of the above-described third embodiment, it is possible to easily evaluate the resolution by supporting a wider variety of imaging apparatuses from those with low resolution to those with high resolution.

[Seventh Modification]
As a modification of the third embodiment, as in a test chart 55 shown in FIG. The first mark frame 51 and the second mark frames 52A and 52B may be provided, and the area except the area surrounded by the first mark frame 51 and the second mark frames 52A and 52B may be plain. good. In this case, the size symbol 14 also serves as the indicator 13 as in the third modification. The first index group 12C includes size symbols 14 from 2 points to 20 points. On the other hand, the first index group 12D includes size symbols 14 from 2 points to 28 points. As a result, the same effects as those of the sixth modification can be obtained.

Further, as in the fourth and fifth modifications described above, the configuration of the test chart in which the first index group 12 and the first mark frame and the second mark frame are arranged is different from that of the third embodiment. Similarly, the area of the base member 11 excluding the area surrounded by the first mark frame 51 and the second mark frames 52A and 52B may be plain.

[Fourth embodiment]
In the first to third embodiments, the first index group 12 and the indexes 13 and size symbols 14 that make up the first index group 12 are arranged in parallel with the X-axis direction. However, the first index group 12 including the index 13 and the size symbol 14 may be tilted. FIG. 18 is a front view of a test chart 60 showing an example of the fourth embodiment.

As shown in FIG. 18, a test chart 60 of the fourth embodiment includes a base member 11, a first index group 12E arranged in a central area 11A, and first index groups 12F to 12I arranged in a peripheral area 11B. , a first mark frame 61, and second mark frames 62A to 62D. The definitions of the central region 11A and the peripheral region 11B are the same as in the first to third embodiments.

The first index group 12E and the indexes 13 and size symbols 14 that make up the first index group 12E are arranged parallel to the X-axis direction, as in the first index group 12 of the first to third embodiments. . Also, the first index group 12E-12I includes the index 13 and the size symbol 14 of the same size as the first index group 12 of the first to third embodiments. The first mark frame 61 surrounds the first index group 12E.

The first index group 12F is arranged outside the first index group 12E, near the long side of the base member 11, and at the same position in the X-axis direction as the first index group 12E. The first index group 12F and the indices 13 and size symbols 14 that constitute the first index group 12F are arranged parallel to the X-axis direction, as in the first index group 12E. The second mark frame 62A surrounds the first index group 12F. The first mark frame 61 and the second mark frame 62A are arranged in parallel with the X-axis direction in alignment with the first index groups 12E and 12F.

The first index group 12G is arranged outside the first index group 12E, near the short side of the base member 11, and at the same position in the Y-axis direction as the first index group 12D. The first index group 12G and the indexes 13 and size symbols 14 that constitute the first index group 12G are arranged in parallel with the Y-axis direction, that is, in a direction orthogonal to the X-axis direction. The second mark frame 62B surrounds the first index group 12G. The second mark frame 62B is arranged parallel to the Y-axis direction in alignment with the first index group 12G.

The first index group 12H and the first index group 12I are arranged outside the first index group 12E along radial directions D1 to D4 extending from the center CP0 of the base member 11 toward the four corners of the base member 11. . Also, the first index group 12I is located outside the first index group 12H on the base member 11 . That is, the first index group 12H and the first index group 12I, and the indices 13 and the size symbols 14 that constitute the first index group 12H and the first index group 12I are arranged obliquely with respect to the X-axis direction. . The second mark frames 62C and 62D are arranged to be tilted with respect to the X-axis direction in accordance with the first index group 12H and the first index group 12I.

Note that the first index group 12F and the first index group 12G are located outside the first index group 12E and extend from the center CP0 of the base member 11 in a direction parallel to the X-axis direction or a direction parallel to the Y-axis direction. (that is, radial direction). Also, the first index group 12H and the first index group 12I are arranged along arcs 63A and 63B (arcs indicated by chain double-dashed lines in the figure) at constant distances R1 and R2 (R1<R2) from the center CP0 of the base member 11. It can also be said that they are distributed along the line. In FIG. 18, the indexes 13 and the size symbols 14 included in the first index group 12H or the first index group 12I are arranged on a straight line, but the indexes 13 and the size symbols 14 are arranged on a curved line along an arc. Also good.

In addition, in the test chart 60, the area of the base member 11 other than the area surrounded by the first mark frame 61 and the second mark frames 62A to 62D is plain and has nothing. This is preferable from the viewpoint that the user does not have to look at the area other than the area surrounded by the first mark frame 61 and the second mark frames 62A to 62D.

When the test chart image is displayed on the display unit 104 or the display and the minimum size index 13 is read, the user may rotate the screen to confirm the index 13 and the size symbol 14 . In such a case, since the first index group 12F to the first index group 12I are arranged along the radial direction from the center CP0 in the test chart 60, they can be easily found, and the resolution can be simplified. can be evaluated to

[Eighth modification]
As a modification of the fourth embodiment, as in a test chart 65 shown in FIG. 19, the first index groups 12E to 12I, the first mark frame 61, and the first index group 12E to 12I are arranged in the same arrangement as in the fourth embodiment. 2 mark frames 62A to 62D may be arranged and the configuration of the first index groups 12E to 12I may be changed. That is, the sizes of the indexes 13 and size symbols 14 included in the first index group 12E and the first index groups 12F to 12I are changed (that is, the sizes are changed in the same manner as in the sixth modification). ) Specifically, the first index group 12E includes the indexes 13 from 2 points to 20 points and the size symbols 14 corresponding to the sizes of the indexes 13 . On the other hand, the first index group 12F to 12I includes indexes 13 of 2 points to 28 points and size symbols 14 corresponding to the sizes of the indexes 13 . That is, the first index group 12E includes an index 13 and a size symbol 14 having sizes larger than those of the first index groups 12F to 12I. This makes it possible to obtain the same effects as in the sixth modification in addition to the effects in the fourth embodiment.

[Ninth Modification]
As another modification, as in the above-described third and fourth embodiments, the area excluding the area surrounded by the first mark frame and the second mark frame in the base member 11 is not plain. A pattern for resolution evaluation may be formed in this region. A test chart 70 shown in FIG. 20 includes a base member 11, a first index group 12, a first mark frame 51, and second mark frames 52A and 52B similar to the test chart 50 in the third embodiment. , and the arrangement of the first mark frame 51 and the second mark frames 52A and 52B are the same as those of the third embodiment.

In the test chart 70, the resolution evaluation pattern 71 is formed in the area of the base member 11 excluding the area surrounded by the first mark frame 51 and the second mark frames 52A and 52B. The resolution evaluation pattern 71 is the same as that formed on a conventional test chart, and is capable of measuring the resolution by analyzing captured image data. It is similar to the resolution chart provided. As a result, in addition to the same effects as those of the above-described embodiments, the resolution of the camera system 100 can be known by analyzing the test chart image obtained by imaging the test chart 70 with the camera system 100 using software or the like.

[Tenth Modification]
A test chart 75 shown in FIG. 21 includes a base member 11 similar to the test chart 60 in the fourth embodiment, a first index group 12E arranged in a central area 11A, and a first indicator group 12E arranged in a peripheral area 11B. 1 index group 12F-12I, first mark frame 61, and second mark frame 62A-62D, first index group 12F-12I, first mark frame 61, and second mark frame 62A 62D are the same as in the fourth embodiment.

In the test chart 75, the resolution evaluation pattern 71 is formed in the area of the base member 11 excluding the area surrounded by the first mark frame 61 and the second mark frames 62A to 62D. The resolution evaluation pattern 71 is similar to that shown in FIG.

[Fifth embodiment]
In the above-described first to fourth embodiments, when evaluating the resolution of the camera system 100 as an imaging device, the evaluation method is described only when one interchangeable lens 102 is attached to the camera body 101. However, the present invention However, in the fifth embodiment described below, when any one of a plurality of selectively attached interchangeable lenses 102 is attached to the camera body 101, that is, when a plurality of interchangeable lenses 102 are different A method for evaluating the resolution of the camera system 100 for the state of .

In the following, an evaluation method for evaluating resolution using the test chart 10 in the first embodiment will be described as an example, but other second to fourth embodiments and first to tenth modifications can also be used to evaluate the resolution by a similar evaluation method. In the following description, the same test chart 10 is used when the telephoto, standard, and wide-angle interchangeable lenses 102A to 102C are attached to the camera body 101 and the resolution is evaluated. When using the telephoto, standard, and wide-angle interchangeable lenses 102A to 102C, different test charts may be used.

For example, as shown in FIGS. 22 to 24, three types of interchangeable lenses 102A to 102C, telephoto, standard, and wide-angle, may be attached to the camera body 101 to evaluate the resolution. In this case, in particular, in order to capture a single test chart 10 in full screen with the wide-angle interchangeable lens 102C, the test chart 10 must be very close, and the shortest imaging distance of the wide-angle interchangeable lens 102C sometimes falls below On the other hand, preparing a large-sized test chart 10 only for the wide-angle interchangeable lens 102C is time-consuming and troublesome. Therefore, especially when using a plurality of types of interchangeable lenses 102 including a wide-angle interchangeable lens 102, an evaluation method for evaluating the resolution of the camera system 100 by arranging a plurality of test charts 10 corresponding to the angle of view will be described below. to state.

First, as shown in FIG. 22, when the telephoto interchangeable lens 102A is attached to the camera body 101 and used, one test chart 10 is used to evaluate the resolution. This is because when the telephoto interchangeable lens 102 is used, since the imaging angle of view is very narrow, one test chart 10 can be imaged over the entire screen with a sufficient imaging distance. That is, resolution can be evaluated by the same evaluation method as in the first to fourth embodiments. As the telephoto interchangeable lens 102A, for example, a lens with a focal length of 18-135 mm and an aperture value of F3.5-5.6 is used. set to 6. In this case, the camera system 100 using the telephoto interchangeable lens 102A obtains a test chart image 20A of the test chart 10. FIG. Note that the test chart image 20A in FIG. 22 shows what is displayed on the display unit 104 of the camera system 100. As shown in FIG. Then, as described above, the minimum size index 13 that can be read from the test chart image 20A is identified. In the portion corresponding to the central area 11A, the index of the minimum readable size is 3 points, and in the portion corresponding to the peripheral area 11B, the index of the minimum readable size is 6 points. Area; (9/3) x (420/23.5) = 53.6 (lines/mm), peripheral area; (9/6) x (420/23.5) = 26.8 (lines/mm) becomes.

As shown in FIG. 23, when the standard interchangeable lens 102B is attached to the camera body 101 and used, the resolution is evaluated by arranging five test charts 10 corresponding to the angle of view. This is because even the standard interchangeable lens 102B may have a wide imaging angle of view depending on the model, and it may be difficult to photograph one test chart 10 in full screen. The test charts 10 are arranged one at the center and four test charts 10 are arranged outside the four corners. In other words, an object three times as large in the vertical and horizontal directions as in the case of using one test chart 10 is imaged. As a result, five test charts 10 can be captured in full screen at an imaging distance corresponding to the angle of view of the standard interchangeable lens 102 .

Then, the camera system 100 using the standard interchangeable lens 102 captures the five test charts 10 arranged in this manner over the entire screen of the captured image to obtain the test chart image 20B. Note that the test chart image 20B in FIG. 23 shows what is displayed on the display unit 104 of the camera system 100. As shown in FIG. Identify the smallest size indicator 13 that can be read from the test chart image 20B. Since an object with three times the size is imaged, the number of points of the minimum size that can be read from the test chart image 20B is reduced to 1/3. can be converted into numbers. From the converted points, the resolution can be easily evaluated in the same manner as in the first to fourth embodiments.

Assuming that the number of points of the minimum size that can be read from the test chart image obtained by imaging the five test charts 10 arranged as described above is P ₀ , P ₀ /3 is P and the above formula (1) should be substituted for Further, the resolution of the camera system 100 equipped with the standard interchangeable lens 102B can be obtained by multiplying the above equation (1) by the reduction ratio corresponding to the sensor width.

As the standard interchangeable lens 102B, for example, a lens with a focal length of 18-55 mm and an aperture value of F2.8-4 is used. A distance of 55 mm and an aperture value of F4.0 were set. In this case, the minimum readable size index is 8 points in the portion corresponding to the test chart 10 in the center, and the minimum readable size index is 14 points in the portion corresponding to the test chart 10 outside the four corners. When substituted into the conversion formula, the center; (9/(8/3)) x (420/23.5) = 60.3 (books/mm), the four corners outside; (9/(14/3)) x ( 420/23.5)=34.5 (lines/mm).

As shown in FIG. 24, when the wide-angle interchangeable lens 102C is attached to the camera body 101 and used, nine test charts 10 corresponding to the angle of view are arranged to evaluate the resolution. This is because the wide-angle interchangeable lens 102C has a wider imaging field angle than the standard interchangeable lens 102B. The test charts 10 are arranged one at the center, four on the outside of the four corners, and four on the outside of the four corners. In other words, an object whose dimensions in the vertical direction and the horizontal direction are five times as large as when one test chart 10 is used is imaged. As a result, nine test charts 10 can be captured in full screen at an imaging distance corresponding to the angle of view of the wide-angle interchangeable lens 102 .

Then, the camera system 100 using the wide-angle interchangeable lens 102C captures the nine test charts 10 arranged in this manner over the entire screen of the captured image to obtain the test chart image 20C. Note that the test chart image 20C in FIG. 24 shows what is displayed on the display unit 104 of the camera system 100. As shown in FIG. Identify the smallest size indicator 13 that can be read from the test chart image 20C. Since an object five times the size is imaged, the number of points of the minimum size that can be read from the test chart image 20C is reduced to 1/5. can be converted into numbers. From the converted points, the resolution can be easily evaluated in the same manner as in the first to fourth embodiments.

Assuming that the number of points of the minimum size that can be read from the test chart image obtained by imaging the nine test charts 10 arranged as described above is P ₀ , P ₀ /5 is P and the above formula (1) should be substituted for Further, the resolution of the camera system 100 equipped with the wide-angle interchangeable lens 102C can be obtained by multiplying the above equation (1) by a reduction ratio corresponding to the sensor width.

As the wide-angle interchangeable lens 102C, for example, a lens with a focal length of 16 to 55 mm and an aperture value of F2.8 is used. , and the aperture value was set to F2.8. In this case, the minimum readable size index is 14 points in the portion corresponding to the test chart 10 in the center, and the minimum readable size index is 18 points in the portion corresponding to the test chart 10 outside the four corners. When substituted into the conversion formula, the center; (9/(14/5)) x (420/23.5) = 57.4 (lines/mm), the four corners outside; (9/(18/5)) x ( 420/23.5)=44.7 (lines/mm).

In this way, when evaluating the resolution of the camera system 100 using a plurality of types of interchangeable lenses 102, the resolution is evaluated according to each interchangeable lens 102 by arranging a plurality of test charts 10. be able to. Also, even when an interchangeable lens 102 with a wide imaging angle of view is used, it is not necessary to use a dedicated test chart, and the resolution can be easily evaluated only by arranging a plurality of test charts 10.例文帳に追加

In each of the above embodiments, the number of points of the JIS standard is used as the number of points, but the number of points of the DTP (Desktop Publishing) standard may be used instead. In the case of this DTP standard, 1 point is defined as 0.3528 mm. Therefore, since the dimension of one point is smaller than that of the JIS standard, it can be said that the resolution of the DTP standard is higher even if the number of read points is the same. Therefore, by multiplying the conversion formula of the above formula (1) by 0.3528/0.3514, a proper resolution can be obtained.

In each of the above-described embodiments, an example in which characters, symbols, symbols, and shapes are represented by printing on one surface of the base member 11 is given as "formed on the base member 11." , The present invention is not limited to this, but includes using a display as the base member 11 and displaying characters, symbols, symbols, and shapes on the display.

In addition, the test charts of the above-described embodiments use not only the index groups formed on the base member 11, but also the image data of the test charts of the above-described embodiments recorded on a recording medium. good too. Examples of recording media for recording image data of the test chart include semiconductor memory, HDD (Hard Disk Drive), CD (Compact Disc), DVD (Digital Versatile Disc), Various recording media such as Blu-ray (registered trademark) Disc (Blu-ray Disc) can be used. As the semiconductor memory, for example, USB (Universal Serial Bus) memory, SD (Secure Digital) memory, SSD (Solid State Drive), etc. can be used.

In each of the above embodiments, a mirrorless single-lens type digital camera was described as an example, but the present invention can also be applied to other imaging devices such as single-lens reflex digital cameras, compact type digital cameras, and smartphones. Moreover, each of the above-described embodiments is an example of the present invention, and each embodiment can be combined as appropriate.

10 Test chart 11 Base member 11A Central region 11B Peripheral region 12 Index group 12A First index group 12B Second index group 12C-12I Index group 13 Index 14 Size symbol 15 Smallest rectangular frame 20 Test chart images 20A-20C Test chart Images 30, 35, 36, 40 Test chart 41 First mark frames 42A, 42B Second mark frame 43 Test chart 44 First mark frames 45A, 45B Second mark frame 46 Test chart 47 First mark frame 48A, 48B Second mark frame 50 Test chart 51 First mark frame 52A, 52B Second mark frame 53, 55, 60 Test chart 61 First mark frame 62A to 62D Second mark frame 65, 70 Test Chart 71 Resolution evaluation pattern 75 Test chart 100 Camera system 101 Camera body 102 Interchangeable lens 102A Telephoto interchangeable lens 102B Standard interchangeable lens 102C Wide-angle interchangeable lens 103 Release switch 104 Display unit 105 Operation button 106 Mount 106A Body side Signal contact 107 Imaging device 108 Touch panel 111 Lens barrel 112 Imaging optical system 113 Focus ring 114 Aperture operation ring 115 Zoom ring 116 Lens mount 116A Lens side signal contact 117 Lens control unit 118 Motor driver 119, 121 Motor 122 Zoom mechanism 123, 124 Sensor 125 Focus lens 126 Magnifying lens 127 Aperture unit 127A Aperture blade 131 Body control unit 132 Shutter unit 133 Motor driver 134 Shutter motor 135 Image memory 136 Image data processing unit 137 AF (Autofocus) processing unit 138 Display control unit 139 Card I/ F (Interface)
141 Bus line 142 Memory card CP0 Center CP1 Center D Directions D1 to D4 Radial direction L Optical axis L11 Distance L12 Distance L21 Distance L22 Distance R1, R2 Distance

Claims (21)

a base member;
a first indicator group formed on the base member and including indicators that are symbols of different sizes and/or size symbols indicating sizes of the indicators;
A test chart for an imaging device in which the first index group is arranged in a central area including the center of the base member and a peripheral area located outside the central area. a first mark frame surrounding the first index group arranged in the central area;
2. A test chart for an imaging device according to claim 1, further comprising a second mark frame surrounding said first index group arranged in said peripheral area. The test chart for the imaging device according to claim 1 or 2, wherein the first index group is arranged along an arc at a constant distance from the center of the base member. The test chart for the imaging device according to claim 1 or 2, wherein the first index group is arranged along a radial direction from the center. The test chart for the imaging device according to any one of claims 1 to 4, wherein at least two of the indicators and/or the size symbols of the same size are arranged at positions where the distances from the center are substantially the same. The first index group is
a second indicator group in which the indicators whose size increases stepwise are arranged in a first direction;
a third index group in which the indexes whose size increases stepwise are arranged in a second direction different from the first direction;
The test chart of the imaging device according to any one of claims 1 to 3, comprising: An area of the base member other than the area surrounded by the first mark frame and the second mark frame is plain. A test chart of the imaging device according to the paragraph. When an area of the base member excluding the area surrounded by the first mark frame and the second mark frame is imaged by an imaging device, the resolution may be measured by analyzing captured image data. 7. The test chart for an imaging device according to claim 2, or any one of claims 3 to 6, wherein a pattern for evaluating resolution is formed. The test chart for the imaging device according to any one of claims 1 to 8, wherein the index and the corresponding size symbol are arranged side by side. The test chart for the imaging device according to any one of claims 1 to 9, wherein the size symbol is the number of points. The test chart for the imaging device according to any one of claims 1 to 10, wherein the sizes of the indicators are 5 or more and 28 or less. The test chart for the imaging device according to any one of claims 1 to 10, wherein the sizes of the indicators are 10 or more and 17 or less. The first index group is
including a first number of the indicators having a size greater than a first threshold;
13. The test chart for an image pickup apparatus according to claim 1, further comprising a second number of said indicators smaller in size than said first threshold than said first number of said indicators. The test chart for the imaging device according to any one of claims 1 to 13, wherein the first index group includes full-size indexes corresponding to the size symbols. When a region including the center of the smallest rectangular frame surrounding the first index group between the plurality of first index groups is defined as the central region of the first index group, the first index group 15. Any one of claims 1 to 14, wherein a plurality of central regions of the index group are arranged at regular intervals in a third direction or a fourth direction, and the plurality of first index groups are arranged without overlapping each other. A test chart of the imaging device described in . The first index group arranged in the central area and the first index group arranged in the peripheral area have the same index and/or the same size symbol. A test chart for the imaging device according to any one of the items. 16. The first index group arranged in the central area and the first index group arranged in the peripheral area are different in the included indexes and/or the size symbols. 2 is a test chart of the imaging device according to item 1; 18. The imaging apparatus according to claim 17, wherein the first index group arranged in the peripheral area includes the index larger in size than the first index group arranged in the central area and/or the size symbol. test chart. An evaluation method for imaging the test chart according to any one of claims 1 to 18 with an imaging device and evaluating the resolution of the imaging device using the captured image data,
When imaging the test chart with the imaging device, imaging one or more of the test charts according to the angle of view of the imaging device;
An evaluation method for evaluating the resolution based on the index of the minimum readable size and/or the size symbol in the first index group imaged from the captured image data. The evaluation method according to claim 19, wherein when the test chart is imaged by the imaging device, the number of test charts corresponding to the angle of view of the imaging device is arranged side by side. A recording medium on which image data of the test chart according to any one of claims 1 to 18 is recorded.

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