Camera testing device and method for testing focusing characteristics of a camera

Abstract

The present application relates to a camera testing apparatus and method for testing the focus characteristics of a camera. A method for testing the focus characteristics of a camera may include: setting a camera so that the camera is aligned with a first chart configured to provide a first scene for testing, so that the camera focuses on the first chart set at a first distance from the camera; measuring blur in an image of a second chart captured at a second distance from the camera, the second chart configured to provide a second scene for testing; and evaluating a phase difference range (PDR) of the camera based on the measured blur and blur calculated using a circle of confusion (CoC) model.

Description

Technical Field

[0001] Various embodiments generally relate to a camera testing apparatus capable of testing camera characteristics. Background Art

[0002] Image sensing devices are devices used to capture optical images by converting light into electrical signals using photosensitive semiconductor materials that react to light. With the recent development of various industries such as the automotive, medical, computer, and communications industries, the demand for high-performance image sensing devices is increasing in various devices such as smartphones, digital cameras, game consoles, the Internet of Things (IoT), robots, security cameras, and medical micro cameras.

[0003] Image sensing devices can be roughly divided into CCD (charge coupled device) image sensing devices and CMOS (complementary metal oxide semiconductor) image sensing devices. CCD image sensing devices provide higher image quality than CMOS image sensing devices, but have a larger size and consume more power than CMOS image sensing devices. In contrast, CMOS image sensing devices have a smaller size and consume less power than CCD image sensing devices. In addition, since CMOS image sensing devices are manufactured using CMOS manufacturing technology, light sensing elements and signal processing circuits can be integrated into a single chip, which makes it possible to manufacture small-sized image sensing devices at low cost. For these reasons, CMOS image sensing devices are being developed for many applications, including mobile devices. Summary of the Invention

[0004] Various embodiments relate to a camera testing apparatus that can evaluate the focusing characteristics of various cameras.

[0005] In an embodiment, a method for testing focus characteristics of a camera may include: setting a camera to align the camera and a first chart configured to provide a first scene for testing, so that the camera focuses on the first chart at a first distance from the camera; measuring blur in an image of a second chart captured at a second distance from the camera, the second chart configured to provide a second scene for testing; and evaluating a phase difference range (PDR) of the camera based on the measured blur and blur calculated by a circle of confusion (CoC) model.

[0006] In an embodiment, a camera testing apparatus includes: a first chart configured to provide a first scene for testing and disposed at a first distance from a camera; a second chart configured to provide a second scene for testing and disposed at a second distance from the camera; and a camera tester configured to: set a camera to align the camera and the first chart so that the camera is focused on the first chart; measure blur of the second chart; and evaluate a phase difference range (PDR) of the camera based on the measured blur and blur calculated by a circle of confusion (CoC) model.

[0007] According to the present embodiment, the camera test apparatus can evaluate the focus characteristics of even an FF (fixed focus) module rather than an AF (auto focus) module, which enables testing of the focus characteristics without the burden of cost, time period, and parts supply requirements.

[0008] Furthermore, various effects directly or indirectly understood through this document can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a block diagram illustrating an example of a camera testing apparatus according to some embodiments of the disclosed technology.

[0010] Figure 2 is a diagram illustrating an example of a camera based on some embodiments of the disclosed technology.

[0011] Figure 3 is a flowchart illustrating an example of a method for testing focus characteristics of a camera using a camera testing apparatus according to some embodiments of the disclosed technology.

[0012] Figure 4A An arrangement of a camera and a first chart at an infinite position is illustrated.

[0013] Figure 4B An arrangement of the camera and the second chart in a macro position is illustrated.

[0014] Figure 5 A circle of confusion (CoC) model for theoretically calculating the diameter of a blur circle is illustrated.

[0015] Figure 6 A method for calculating the phase difference range (PDR) is illustrated. DETAILED DESCRIPTION

[0016] Hereinafter, various embodiments will be described with reference to the accompanying drawings. However, it should be understood that the present disclosure is not limited to specific embodiments, but includes various modifications, equivalents and / or alternatives. The embodiments of the present disclosure can provide various effects that can be directly / indirectly recognized by the present disclosure.

[0017] Figure 1 is a block diagram illustrating an example of a camera testing apparatus according to some embodiments of the disclosed technology. Figure 2 This is an example of some embodiments based on the disclosed technology. Figure 1 Figure 1 shows an example of a camera.

[0018] Reference Figure 1 The camera testing device 10 implemented based on some embodiments of the disclosed technology is used to test various characteristics (eg, optical characteristics) of a camera 100 .

[0019] In some implementations, the camera testing apparatus 10 may include a camera 100 (or a camera holder to be connected to the camera 100 ), a chart 200 , a collimating lens (CL) 300 , and a camera tester 400 .

[0020] The camera 100 is a target to be tested by the camera test apparatus 10. The camera 100 is mounted on the camera test apparatus 10, and the camera test apparatus 10 holds the camera 100 during testing of the camera 100.

[0021] Examples of the camera 100 include a digital camera for capturing still images and a digital video camera for capturing videos. For example, the camera 100 may be a DSLR (digital single-lens reflex) camera, a mirrorless camera, or a mobile phone (e.g., a smartphone). The camera 100 may include any device having a lens and an imaging element that can generate an image by converting light of an optical image of an object into an electrical signal.

[0022] In some implementations, the camera 100 may include a fixed focus (FF) module that focuses light from a scene or object within a lens module (e.g., Figure 2 The lens module 120 shown in FIG. 1 and the image plane (eg, Figure 2 10). Other camera designs may differ from FF module designs by including an autofocus (AF) module having an actuator for moving the relative position of the lens module 120 and the pixel array 110 to adjust the distance between the lens module and the image plane. Various actuators may be implemented, including, for example, a voice coil motor (VCM). Unlike the AF module, the "fixed" distance between the lens module and the image plane in the FF module may indicate that the FF module cannot adjust the camera focus.

[0023] Because the AF module includes a VCM to adjust the camera focus, tests for evaluating the AF module's focusing characteristics are performed by moving the VCM. However, accurate testing requires the AF module to have various test-related functions as well as a VCM for autofocus, and there may be difficulties in procuring the components of the AF module (e.g., the VCM). Therefore, manufacturing the AF module (e.g., requiring active alignment calibration and VCM calibration) may cost considerable time and money. Furthermore, it is difficult to test or evaluate the camera's focusing characteristics before assembling the components of the AF module.

[0024] However, the camera test apparatus 10 according to some embodiments of the disclosed technology can evaluate the focus characteristics of the FF module instead of the AF module, thereby saving time and money spent on testing using the AF module.

[0025] The focus characteristic may indicate a characteristic related to the focus of the camera 100 , such as a phase difference range (PDR) as will be discussed below.

[0026] Reference Figure 2 , the camera 100 may include a lens module 120 , a pixel array 110 , a pixel driving circuit 130 , and a pixel readout circuit 140 .

[0027] The pixel array 110 may include a plurality of unit pixels arranged in n rows and m columns, where n and m are integers equal to or greater than 2. In an embodiment, the plurality of unit pixels may be arranged in a 2D pixel array including rows and columns. In another embodiment, the plurality of unit pixels may be arranged in a 3D pixel array.

[0028] The plurality of unit pixels may generate electrical signals on a unit pixel basis or on a pixel group basis, and the unit pixels within each pixel group may share at least a specific internal circuit.

[0029] Each of the plurality of unit pixels can detect light passing through the lens module 120 and generate a pixel signal corresponding to the luminous intensity of the light. For example, the pixel array 110 can receive a drive signal including a row selection signal, a pixel reset signal, and a transfer signal from the pixel driving circuit 130. The drive signal can be used to select a unit pixel of the pixel array 110 to perform an operation corresponding to the row selection signal, the pixel reset signal, or the transfer signal.

[0030] The multiple unit pixels may include image detection pixels for acquiring color images and phase difference detection pixels for acquiring phase difference information. The image detection pixels may be arranged according to a specific rule or pattern (e.g., a Bayer pattern), and each image detection pixel generates a pixel signal by detecting light corresponding to a specific color (e.g., red, blue, or green). The phase difference detection pixels can acquire two images and detect the phase difference by calculating how much the two images are offset from the optical axis.

[0031] For example, pixels for acquiring two images can be implemented as paired pixels including two adjacent pixels sharing an on-chip lens, or as semi-shielded pixels, which include: a pixel that is constructed to include a light-shielding layer set on half (e.g., the left half) of the light receiving area of ​​the pixel; and another pixel that is constructed to include a light-shielding layer set on the other half (e.g., the right half) of the light receiving area of ​​the other pixel, and the pixel and the other pixel are arranged together in the pixel array 110.

[0032] The lens module 120 may collect light received from a scene and transmit the collected light to the pixel array 110. The lens module 120 may include one or more lenses arranged around an optical axis. The lens module 120 may have a predetermined curvature so that the pixel array 110 can detect a scene corresponding to a predetermined field of view (FOV).

[0033] As described above, the camera 100 may include a fixed focus (FF) module or correspond to a fixed focus (FF) module. In this case, the distance between the lens module 120 and the image plane (e.g., the light receiving surface of the pixel array 110) on which the image of the collected light is formed may be fixed.

[0034] In some implementations, the pixel drive circuit 130 may enable the pixel array 110 to perform specific operations on the unit pixels included in the corresponding row in response to receiving command and control signals from the timing controller 150. In an embodiment, the pixel drive circuit 130 may select one or more unit pixels arranged at one or more rows of the pixel array 110. The pixel drive circuit 130 may generate a row select signal based on the row address signal of the timing controller 150 to select one or more rows from the plurality of rows. The pixel drive circuit 130 may sequentially enable a pixel reset signal and a transfer signal for the pixels corresponding to the selected one or more rows. Thus, a reference signal and an image signal, which are analog signals generated by the corresponding unit pixels of the selected row, may be sequentially transmitted to the pixel readout circuit 140. The reference signal may be an electrical signal provided to the pixel readout circuit 140 when the sensing node (e.g., a floating diffusion node) of the unit pixel is reset, and the image signal may be an electrical signal provided to the pixel readout circuit 140. Such electrical signals correspond to photocharges generated by the unit pixel and accumulated in the sensing node. The reference signal indicates the unique reset noise of the pixel, and the image signal indicates the intensity of the incident light. In this patent document, the reference signal and the image signal may be referred to as pixel signals.

[0035] The pixel readout circuit 140 can use a correlated double sampling (CDS) scheme to remove undesirable pixel offset values ​​such as fixed pattern noise by sampling the pixel signal twice to remove the difference between the two samples (e.g., a reference signal and an image signal). Through CDS, the pixel readout circuit 140 can remove undesirable offset values ​​by comparing the pixel output voltages acquired before and after the accumulation of photocharges generated by the incident light in the sensing node, thereby measuring the pixel output voltage based only on the incident light. In an embodiment, the pixel readout circuit 140 can sequentially sample and hold the reference signals and image signals provided to the plurality of column lines from the pixel array 110, respectively. That is, the pixel readout circuit 140 can sample and hold the levels of the reference signal and the image signal corresponding to each column of the pixel array 110.

[0036] The pixel readout circuit 140 may include an analog-to-digital converter (ADC) for converting the signal sampled by the CDS into a digital signal. In one embodiment, the pixel readout circuit 140 may include a ramp comparison ADC. The ramp comparison ADC may include: a comparison circuit configured to compare the analog pixel signal with a ramp signal that ramps up and down; and a counter configured to perform a counting operation until the voltage of the ramp signal matches the voltage of the analog pixel signal.

[0037] The pixel readout circuit 140 may include an output buffer that temporarily holds column-based image data provided from the ADC and outputs the held data. The output buffer may temporarily store the image data output from the ADC in response to receiving a control signal from the timing controller 150. The output buffer may operate as an interface configured to compensate for a difference in transmission rate (or processing speed) between the camera 100 and another device connected to the camera 100.

[0038] The pixel readout circuit 140 may include a column driver to select a column of the output buffer based on a control signal from the timing controller 150 and sequentially output image data temporarily stored in the selected column of the output buffer. In an embodiment, the column driver may receive a column address signal from the timing controller 150 to select a column of the output buffer based on the column address signal, so that the image data IDATA is output from the selected column of the output buffer to the outside of the camera 100.

[0039] The timing controller 150 may generate clock signals required for the operation of each component of the camera 100, control signals for timing control, row address signals for selecting rows, and column address signals for selecting columns, and provide the generated signals to the corresponding components. In embodiments, the timing controller 150 may include a logic control circuit, a phase-locked loop (PLL) circuit, a timing control circuit, a communication interface circuit, and the like.

[0040] Return to reference Figure 1 , chart 200 can provide a scene that can be used to test camera 100 (such as the focusing characteristics of camera 100). In one example, the "scene" provided by chart 200 can include a scene created by chart 200 or stored in chart 200 for camera testing purposes. The distance between chart 200 and camera 100 can be adjusted by camera tester 400.

[0041] The chart 200 may be a first chart ( Figure 4A 200-1) or the second chart ( Figure 4B 200-2 in the following). Figure 4A and Figure 4B A first graph 200 - 1 and a second graph 200 - 2 are described.

[0042] The collimating lens (CL) 300 can convert the real distance between the camera 100 and the chart 200 into a virtual distance by correcting the path of light received from the chart 200. For example, even if the real distance between the camera 100 and the chart 200 is only about 20 cm, since the CL 300 is provided between the camera 100 and the chart 200, the virtual distance between the camera 100 and the chart 200 can become 1 m from the viewpoint of the camera 100.

[0043] The ability of the CL 300 to convert a real distance into a virtual distance (i.e., distance conversion performance) may be determined based on the performance of the CL 300 and the distance between the chart 200 and the CL 300. The distance conversion performance may be calculated and stored in advance by the camera tester 400, and the camera tester 400 may adjust the positions of the chart 200 and the CL 300 by referring to the distance conversion performance so that the camera 100 and the chart 200 have the necessary virtual distance.

[0044] The camera tester 400 can test the optical characteristics of the camera 100, or specifically, the focusing characteristics, and control the camera 100, the chart 200, and the CL 300 in order to perform the test. Figure 3 , and the following figures describe example operations of the camera tester 400 .

[0045] Figure 3 is a flowchart illustrating an example of a method for testing focus characteristics of a camera using a camera testing apparatus according to some embodiments of the disclosed technology. Figure 4A An arrangement of the camera and the first graph with an infinite distance therebetween is illustrated. Figure 4B An arrangement of the camera and the second graph with a micro distance therebetween is illustrated. Figure 5 A circle of confusion (CoC) model for theoretically calculating the diameter of a circle of confusion is illustrated. Figure 6 A method for calculating the phase difference range (PDR) is illustrated.

[0046] Reference Figure 3 At S10 , the camera tester 400 may set the camera 100 to adjust the focus of the camera 100 to focus on the first chart 200 - 1 set at an infinite position corresponding to an infinite distance. The infinite distance may be a predetermined evaluation distance required by the user of the camera 100 .

[0047] At S10, the graph 200 is a first graph 200-1. The first graph 200-1 can provide a first scenario suitable for easily determining whether the camera 100 is focused on the graph 200 (in focus). For example, the first graph 200-1 can be a spatial frequency response (SFR) graph, an edge SFR (eSFR) graph, a line graph, or a television (TV) line graph. Here, the word "aligned" can indicate that light from an object point is nearly as convergent as possible in the image. For example, the focus of collimated light parallel to the axis coincides with the image plane.

[0048] Reference Figure 4A , the camera tester 400 may adjust the positions of the first chart 200-1 and the CL 300 so that the distance between the camera 100 and the first chart 200-1 becomes infinite distance. Then, the camera tester 400 may adjust the settings of the camera 100 so that the camera 100 focuses on the first chart 200-1 located at the position corresponding to the infinite distance. The settings of the camera 100 may include settings (or alignments) for adjusting the distance between the lens module 120 and the pixel array 110. Since the camera 100, which is a fixed focus (FF) module, does not include a voice coil motor (VCM), the distance between the lens module 120 and the pixel array 110 is not automatically adjustable, but can be manually or mechanically adjusted (e.g., manual screw adjustment).

[0049] The camera tester 400 can operate the camera 100 to acquire image data IDATA while adjusting the distance between the lens module 120 and the pixel array 110. Furthermore, the camera tester 400 can analyze the image data IDATA to determine the distance between the lens module 120 and the pixel array 110 at which the camera 100 focuses on the first chart 200-1. Whether the camera 100 focuses on the first chart 200-1 can be determined based on whether the contrast of the image data IDATA is maximized. That is, the camera tester 400 can search for the distance between the lens module 120 and the pixel array 110 at which the contrast of the image data IDATA is maximized, and fix the lens module 120 at the position at which the contrast of the image data IDATA is maximized. Therefore, when the setup is completed at S10, the camera 100 can adjust the focus to the first chart 200-1 at an infinite position corresponding to an infinite distance.

[0050] Return to reference Figure 3 At S20, the camera tester 400 may move the chart 200 to a macro position corresponding to the macro distance. The macro distance may be a predetermined evaluation distance requested by a user of the camera 100. In one example, the macro distance may have a value smaller than the infinite distance.

[0051] After S20, the graph 200 is a second graph 200-2. The second graph 200-2 may provide a second scenario suitable for more easily measuring the degree of blur that occurs when the camera 100 is out of focus. For example, the second graph 200-2 may be a diamond graph, a vine graph, a bar graph, or a checkerboard graph.

[0052] In another embodiment, as the process proceeds from S10 to S20 , the type of the chart 200 is not changed from the first chart 200 - 1 to the second chart 200 - 2 , but one of the charts 200 - 1 and 200 - 2 may continue to be used.

[0053] Reference Figure 4B , the camera tester 400 may adjust the position of the second chart 200-2 so that the distance between the camera 100 and the second chart 200-2 becomes a micro distance. The micro distance may be a distance (eg, 10 cm) that can be realized as a real distance between the camera 100 and the second chart 200-2 without the CL 300. Figure 4B As shown, the CL 300 may not be disposed between the camera 100 and the second graph 200-2. In another embodiment, when the micro distance exceeds a distance that can be realized as a real distance between the camera 100 and the second graph 200-2, different from Figure 4B In the configuration shown in , the CL 300 may be disposed between the camera 100 and the second chart 200 - 2 .

[0054] Return to reference Figure 3 At S30 , the camera tester 400 may measure blur indicating the degree to which the camera 100 is out of focus with respect to the second chart 200 - 2 disposed at a micro distance from the camera 100 .

[0055] In some implementations of the disclosed technology, as will be discussed below, calculations associated with theoretical blurring using a circle of confusion (CoC) model can be performed.

[0056] Figure 5 The diagram illustrates a path along which light rays emitted from a point Pi of the first chart 200-1 at the infinite position INF pass through the lens module 120 of the camera 100 and reach the image plane IP of the camera 100. Since the camera 100 is focused (in focus) on the first chart 200-1 at the infinite position INF, the light rays emitted from the point Pi of the first chart 200-1 may converge to the first point P1 of the image plane IP. It is assumed that no blur occurs when the camera 100 is in focus.

[0057] Figure 5 The diagram also illustrates the path along which light emitted from a point Pm on the second chart 200-2, positioned at the macro position MAC, passes through the lens module 120 of the camera 100 to the image plane IP of the camera 100. Since the focus of the light emitted from the point Pm on the second chart 200-2, positioned at the macro position MAC, is located before the image plane IP (i.e., in a back-focus state), the light emitted from the point Pm on the second chart 200-2 can be incident on the second point P2 and the third point P3 on the image plane IP. Since the image plane IP is a plane corresponding to the pixel array 110, the shape of the light emitted from the point Pm on the second chart 200-2 incident on the image plane IP can correspond to a circle on the plane. Therefore, the circle that appears on the image plane IP due to defocus can be defined as a blur circle. As the defocus state of the camera 100 becomes more severe, the diameter c of the blur circle can increase.

[0058] The diameter c of the blur circle can be calculated by the following equation 1:

[0059]

[0060] Where S1 is the first distance, S2 is the second distance, and f is the focal point.

[0061] In Equation 1, the first distance S1 may indicate the distance between the infinite position INF and the center of the lens module 120 (or the distance between the first graph 200-1 and the camera 100), and the second distance S2 may indicate the distance between the macro position MAC and the center of the lens module 120 (or the distance between the second graph 200-2 and the camera 100).

[0062] The focal length f indicates the distance between the center of the lens module 120 and a point Pf at which light rays perpendicularly incident on the camera 100 at both ends of the lens module 120 pass through the lens module 120 and then intersect. The focal length f may be predetermined according to characteristics (eg, curvature) of the lens module 120.

[0063] That is, when the first distance S1, the second distance S2, and the focal length f are determined, the diameter c of the circle of confusion can be theoretically calculated. The diameter of the circle of confusion calculated arithmetically can be defined as the first diameter c. However, due to various factors (e.g., alignment errors of the lens module 120), the second diameter c', which is the diameter of the circle of confusion measured by the camera 100, may differ from the theoretically calculated diameter c of the circle of confusion.

[0064] Return to reference Figure 3 At S30, the camera tester 400 may extract the circle of confusion from the image data IDATA of the camera 100 that has imaged the second chart 200-2 set at the macro position MAC, and measure the diameter of the extracted circle of confusion to measure the circle of confusion. The diameter of the circle of confusion actually measured may be defined as a second diameter c'. Here, blur may indicate the diameter of the circle of confusion.

[0065] The theoretically calculated first diameter c of the circle of confusion can be converted into a first phase difference. The first phase difference can be a value obtained by theoretically calculating how far apart light rays emitted from a point Pm at the macro position MAC are from each other on a pixel basis when incident on the image plane IP through the lens module 120. In embodiments, the first phase difference can correspond to a value obtained by dividing the first diameter c of the circle of confusion by the width of a pixel included in the pixel array 110. In some embodiments of the disclosed technology, it is assumed that the multiple pixels included in the pixel array 110 have the same width.

[0066] At S40, the camera tester 400 may convert the second diameter c' of the circle of confusion that has been actually measured into a second phase difference. The second phase difference may be a value obtained by actually measuring how far apart light rays emitted from a point Pm at the macro position MAC are from each other on a pixel basis when incident on the image plane IP through the lens module 120. In an embodiment, the camera tester 400 may calculate the second phase difference by dividing the second diameter c' of the circle of confusion by the width of a pixel included in the pixel array 110.

[0067] Reference Figure 6In some embodiments of the disclosed technology, a phase difference range (PDR) may indicate a range from a minimum phase difference to a maximum phase difference. As the graph 200 moves from the infinite position INF to the macro position MAC, the phase difference may gradually increase. The minimum phase difference may indicate the phase difference corresponding to the blur of the first graph 200-1 at the infinite position INF. The maximum phase difference may indicate the phase difference corresponding to the blur of the second graph 200-2 at the macro position MAC.

[0068] The phase difference corresponding to the blur of the first chart 200 - 1 located at the infinite position INF may be set so that the camera 100 focuses on the first chart 200 - 1 located at the infinite position INF, and thus the phase difference corresponding to the blur of the first chart 200 - 1 located at the infinite position INF may correspond to 0.

[0069] In some implementations, a first PDR PDR1 may be calculated based on the first phase difference PD1 calculated above. The first PDR PDR1 may indicate a PDR corresponding to a case where the first phase difference PD1 is theoretically obtained, and thus the first PDR PDR1 may correspond to the difference between the first phase difference PD1 as the maximum phase difference and 0 as the minimum phase difference. Therefore, the first PDR PDR1 may have the same value as the first phase difference PD1.

[0070] The camera tester 400 may calculate a second PDR PDR2 based on the second phase difference PD2. The second PDR PDR2 may indicate a PDR corresponding to a case where the second phase difference PD2 is acquired through actual measurement, and thus the second PDR PDR2 may correspond to the difference between the second phase difference PD2 as the maximum phase difference and 0 as the minimum phase difference. Therefore, the second PDR PDR2 may have the same value as the second phase difference PD2.

[0071] In an embodiment, the first diameter c of the circle of confusion, the first phase difference PD1 , and the first PDR PDR1 may be pre-calculated by the camera tester 400 before performing a test on the camera 100 and stored in the camera tester 400 .

[0072] At S60, the camera tester 400 may evaluate the PDR of the camera 100 according to the comparison result between the first PDR PDR1 and the second PDR PDR2. Figure 6 As shown, when the second PDR PDR2 exceeds the first PDR PDR1, the camera tester 400 may evaluate that the PDR of the camera 100 has passed. Conversely, when the second PDR PDR2 is less than the first PDR PDR1, the camera tester 400 may evaluate that the PDR of the camera 100 has failed.

[0073] This is because a design margin can be provided during subsequent processing (eg, VCM installation) of the camera 100 only when the second PDR PDR2 based on a value actually measured by the camera 100 is greater than the first PDR PDR1 based on a theoretically calculated value.

[0074] Furthermore, in some implementations, steps S40 , S50 , and S60 are included in the step of evaluating the PDR of the camera 100 based on the blur c′ actually measured at S30 and the blur c calculated by the CoC model.

[0075] The method of testing the camera 100 based on some embodiments of the disclosed technology can obtain the PDR of a camera in which a VCM is not installed, thereby reducing the cost and time required to obtain the PDR.

[0076] In some embodiments of the disclosed technology, the PDR of camera 100 is evaluated by setting camera 100 so that it focuses on chart 200 at infinite position INF and obtaining the PDR by measuring blur at macro position MAC. However, the disclosed technology is not limited thereto. In another embodiment of the disclosed technology, the PDR of camera 100 can be evaluated by setting camera 100 so that it focuses on chart 20 at macro position MAC and obtaining the PDR by measuring blur at infinite position INF.

[0077] Although various embodiments have been described above, it should be understood that the disclosed embodiments are merely examples of certain implementations. Therefore, various modifications may be made to the camera test device and other embodiments described herein based on the content disclosed and / or shown in this patent document.

[0078] CROSS-REFERENCE TO RELATED APPLICATIONS

[0079] This patent document claims priority to and the benefit of Korean Application No. 10-2021-0133204, filed on October 7, 2021, which is hereby incorporated by reference as a part of the disclosure of this patent document.

Claims

1. A method for testing the focusing characteristics of a camera, the method comprising the following steps: positioning a camera to align the camera with a first chart providing a first scene for testing, such that the camera focuses on the first chart disposed at a first distance from the camera; measuring blur in an image of a second chart captured at a second distance from the camera, the second chart providing a second scene for testing; as well as The phase difference range PDR of the camera is evaluated based on the measured blur and the blur calculated by the circle of confusion CoC model.

2. The method according to claim 1, wherein The first distance is an infinite distance and the second distance is a micro distance, and wherein the first distance has a larger value than the second distance.

3. The method according to claim 1, wherein The camera is a fixed-focus module configured without a voice coil motor.

4. The method according to claim 1, wherein The camera includes: a lens module that collects light received from the first scene or the second scene; and A pixel array includes a plurality of pixels and an image plane, wherein each pixel detects light transmitted from the lens module, and wherein the light is incident on the image plane.

5. The method according to claim 4, wherein The steps of setting up the camera include the following steps: determining whether the camera is focused on the first chart by analyzing image data generated by the camera; and In the event that the camera is out of focus with the first chart, a distance between the lens module and the image plane is adjusted.

6. The method according to claim 5, wherein: The step of determining whether the camera is focused on the first chart includes determining whether the contrast of the image data is maximized.

7. The method according to claim 4, wherein: The blur calculated by the CoC model is a first diameter of a blur circle calculated by performing an operation on the first distance, the second distance, and a focal length of the lens module.

8. The method according to claim 7, wherein The step of measuring the blur comprises the following steps: extracting a circle of confusion from image data of the camera that has imaged the second chart; and A second diameter of the extracted blur circle is measured.

9. The method according to claim 8, wherein The step of evaluating the PDR of the camera includes calculating a second phase difference by dividing the second diameter corresponding to the measured blur by a width of each of the plurality of pixels.

10. The method according to claim 9, wherein: The step of evaluating the PDR of the camera further includes calculating a second PDR based on the second phase difference.

11. The method according to claim 10, wherein: The step of evaluating the PDR of the camera further includes evaluating the PDR of the camera based on a comparison result between a first PDR calculated from the first diameter and the second PDR.

12. The method according to claim 11, wherein The first PDR is calculated based on a first phase difference calculated by dividing the first diameter by the width of each of the plurality of pixels.

13. The method according to claim 1, wherein The first graph is any one of a spatial frequency response SFR graph and a line graph.

14. The method according to claim 1, wherein The second chart is any one of a diamond chart, a vine chart, a bar chart, and a checkerboard chart.

15. A camera testing device, comprising: a first chart providing a first scene for testing and arranged to have a first distance from the camera; a second chart providing a second scene for testing and arranged at a second distance from the camera; as well as a camera tester that: positions the camera to align the camera with the first chart so that the camera is focused on the first chart; measuring blur of the second chart; And evaluating the phase difference range (PDR) of the camera based on the measured blur and the blur calculated by the confusion circle (CoC) model.

16. The camera testing device according to claim 15, wherein: The first distance is an infinite distance, and the second distance is a micro distance, and wherein the first distance has a larger value than the second distance.

17. The camera testing device according to claim 15, wherein: The blur of the second chart is measured by: extracting a blur circle from image data of the camera that has imaged the second chart; and measuring a second diameter of the extracted blur circle.

18. The camera testing device according to claim 17, wherein: The PDR of the camera is evaluated by calculating a second phase difference by dividing the second diameter corresponding to the measured blur by the width of each image sensing pixel in the camera.

19. The camera testing device according to claim 18, wherein: The PDR of the camera is further evaluated by calculating a second PDR based on the second phase difference.

20. The camera testing device according to claim 15, wherein: The first graph is any one of a spatial frequency response (SFR) graph and a line graph, and the second graph is any one of a diamond graph, a vine graph, a bar graph, and a checkerboard graph.

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