WO2019105433A1 - 影像畸变检测方法和系统 - Google Patents

影像畸变检测方法和系统 Download PDF

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Publication number
WO2019105433A1
WO2019105433A1 PCT/CN2018/118275 CN2018118275W WO2019105433A1 WO 2019105433 A1 WO2019105433 A1 WO 2019105433A1 CN 2018118275 W CN2018118275 W CN 2018118275W WO 2019105433 A1 WO2019105433 A1 WO 2019105433A1
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Prior art keywords
image
line
maximum width
width value
determining
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PCT/CN2018/118275
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English (en)
French (fr)
Inventor
魏伟
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京东方科技集团股份有限公司
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Priority to US16/767,147 priority Critical patent/US11360304B2/en
Publication of WO2019105433A1 publication Critical patent/WO2019105433A1/zh

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/01—Head-up displays
    • G02B27/0101—Head-up displays characterised by optical features
    • G02B27/0103—Head-up displays characterised by optical features comprising holographic elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/01—Head-up displays
    • G02B27/0101—Head-up displays characterised by optical features
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/60—Analysis of geometric attributes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N17/00—Diagnosis, testing or measuring for television systems or their details
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/01—Head-up displays
    • G02B27/0101—Head-up displays characterised by optical features
    • G02B2027/011—Head-up displays characterised by optical features comprising device for correcting geometrical aberrations, distortion
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/01—Head-up displays
    • G02B27/0101—Head-up displays characterised by optical features
    • G02B2027/0138—Head-up displays characterised by optical features comprising image capture systems, e.g. camera

Definitions

  • the present disclosure relates to the field of display system testing technologies, and in particular, to an image distortion detecting method and system.
  • Embodiments of the present disclosure provide an image distortion detecting method and system, which can be used to detect depth of field distortion of an image output by an image output device.
  • At least one embodiment of the present disclosure provides an image distortion detecting method, including: controlling a video output device to output a test image; and capturing an image of the test image by using an image acquiring device to obtain an image, the image being the image capturing
  • the device takes a picture taken when the imaging position of the image output device is focused, the image acquisition device is disposed at a set observation point of the image output device; and determines whether the image distortion satisfies the requirement based on the width of the line in the imaged image.
  • the test image is an image output by the image output device after inputting the test pattern
  • the test pattern is at least one of an equally spaced grid pattern and an equiangular grid pattern.
  • the image capturing device is configured to capture the test image to obtain an image, including: placing a reference object at an imaging position of the image output device, where the imaging position and the image are The spacing between the set observation points is equal to setting the imaging distance; the image acquisition device is focused on the reference object, and the test image is captured to obtain the imaged image.
  • the image capturing apparatus is configured to capture the test image to obtain an image, including: adjusting a focal length of the image acquiring device at a set interval, and each time After the adjustment, the test image is captured once to obtain a plurality of image images; and the clearest image image is selected from the plurality of image images as the imaged image.
  • the selecting the clearest image image from the plurality of image images as the imaged image comprises: determining a width of a set line in each of the image images; and setting a line with a minimum width Image of the image as the imaged image.
  • the determining the width of the set line in each image picture comprises: determining a width of the set line at a plurality of measurement points, the plurality of measurement points being spaced along an extending direction of the set line Arranging on the set line; determining a width of the set line according to a width at the plurality of measurement points.
  • determining whether the image distortion meets the requirement based on the width of the line in the imaged image comprises: determining a maximum width value of the line in the imaged image; and when the maximum width value is When the threshold is not greater than the set threshold, it is determined that the image distortion satisfies the requirement; or, when the ratio of the maximum width value to the specified line width is not greater than the set threshold, determining that the image distortion satisfies the requirement; or, when the maximum width value and the specified When the difference in line width is not greater than the set threshold, it is determined that the image distortion meets the requirements.
  • the determining a maximum width value of the line in the imaged image comprises: acquiring brightness data of the imaged image; determining two edges of each line in the imaged image according to the brightness data; Each line in the picture determines the spacing between the two edges in a direction perpendicular to the direction in which the lines extend; the maximum spacing of the spaces to be determined is taken as the maximum width value of the line.
  • the determining a maximum width value of the line in the imaged image includes: converting the imaged image into a grayscale image; performing binarization processing on the grayscale image to obtain a binarized image; determining In the binarized image, the number of pixels consecutively set to a value perpendicular to the extending direction of each line; the maximum number of the determined number of pixel points is taken as the maximum width of the line value.
  • determining whether the image distortion meets the requirement based on the width of the line in the imaged image comprises: determining a position corresponding to a maximum width value of the line in the imaged image; adjusting the a focal length of the image acquisition device, such that the image acquisition device focuses on a position corresponding to the maximum width value; determines a focal length when the image acquisition device focuses on a position corresponding to the maximum width value; and focuses on the image acquisition device The focal length at the position corresponding to the maximum width value determines whether the image distortion satisfies the requirement.
  • the determining a focal length when the image acquiring device focuses on a position corresponding to the maximum width value comprises: placing a reference object after the image acquiring device focuses on a position corresponding to the maximum width value a position capable of being clearly imaged in the image acquisition device; determining a distance between the reference object and the set observation point as a focal length when the image acquisition device focuses on a position corresponding to the maximum width value .
  • determining, according to a focal length when the image acquiring device focuses on a position corresponding to the maximum width value determining whether image distortion meets a requirement, comprising: when the image acquiring device is focused on the maximum width value When the focal length at the position is within the set range, it is determined that the image distortion satisfies the requirement; when the image capturing device focuses on the position corresponding to the maximum width value, the focal length is not within the set range, and it is determined that the image distortion does not satisfy the requirement.
  • the image acquisition device is an illuminometer or a charge coupled device camera.
  • the image output device comprises a head up display or a holographic image output device.
  • At least one embodiment of the present disclosure further provides an image distortion detecting system, comprising: an image acquiring device, configured to capture a test image output by the image output device, to obtain an image, the image is the image capturing device focusing a picture taken at an imaging position of the image output device, the image acquisition device being disposed at a set observation point of the image output device; and control means for determining whether image distortion is based on a width of a line in the imaged image fulfil requirements.
  • the test image distortion detecting system further includes a reference object for being placed at an imaging position of the image output device, the imaging position and the set observation point The distance between the two is equal to the set imaging distance; the image acquisition device is configured to focus on the reference object, and the test image is captured to obtain the imaged image.
  • the image acquiring device is configured to change a focal length at a set interval, and perform a shooting on the test image after each change of the focal length to obtain a plurality of image images;
  • the control device is configured to select the clearest image image from the plurality of image images as the imaged image.
  • control device is configured to determine a maximum width value of a line in the imaged image; when the maximum width value is not greater than a set threshold, determine that image distortion satisfies a requirement; or, when the maximum width value is When the ratio of the specified line width is not greater than the set threshold, it is determined that the image distortion satisfies the requirement; or, when the difference between the maximum width value and the specified line width is not greater than the set threshold, it is determined that the image distortion satisfies the requirement.
  • control device is configured to determine a position corresponding to a maximum width value of the line in the imaged image; adjust a focal length of the image acquiring device, so that the image acquiring device focuses on a position corresponding to the maximum width value; Describe a focal length when the image acquiring device focuses on a position corresponding to the maximum width value; and determine whether the image distortion satisfies a requirement according to a focal length when the image acquiring device focuses on a position corresponding to the maximum width value.
  • the image acquisition device is an illuminometer or a charge coupled device camera.
  • the image output device comprises a head up display or a holographic image output device.
  • FIG. 1 is a schematic flow chart of an image distortion detecting method according to an embodiment of the present disclosure
  • FIG. 2a is a schematic diagram of a grid pattern provided by an embodiment of the present disclosure
  • 2b is a schematic diagram of an equiangular grid pattern provided by an embodiment of the present disclosure
  • FIG. 3 is a schematic diagram of setting a set observation point according to an embodiment of the present disclosure.
  • FIG. 4 is a schematic flow chart of another image distortion detecting method according to an embodiment of the present disclosure.
  • FIG. 5 is a schematic flowchart of still another image distortion detecting method according to an embodiment of the present disclosure.
  • FIG. 6 is a schematic structural diagram of a focus position detecting manner according to an embodiment of the present disclosure.
  • FIG. 7 is a schematic diagram of an image distortion detecting system according to an embodiment of the present disclosure.
  • FIG. 1 is a schematic flowchart of the method for detecting image distortion. As shown in FIG. 1, the method includes the following steps.
  • step S101 the image output device is controlled to output a test image.
  • test image is an image that is output after the image output device inputs the test pattern.
  • the image output device refers to an image output device whose output image is not imaged on a physical imaging screen, such as a HUD, a holographic image output device, and the like.
  • the image output by the image output device can be either a virtual image (such as an output image of a HUD) or a real image (such as a holographic image output by a holographic image output device).
  • the step S101 may include: lighting a display source of the image output device and inputting image data of the test pattern into the display source, thereby causing the image output device to output the test image.
  • the projection HUD typically includes a display source, an optical system, and an imaging screen (typically a front windshield of the automobile), wherein the display source is used to output a graphic based on the input image data, the graphic being projected through the optical system To the imaging screen, imaging is performed on the side of the imaging screen opposite the side on which the display source is located.
  • the test pattern may be a grid pattern.
  • 2a is a schematic diagram of a grid pattern provided by an embodiment of the present disclosure.
  • the grid pattern 2 includes a plurality of first straight lines 21 arranged in parallel and a plurality of second straight lines 22 arranged in parallel.
  • the first straight line 21 is disposed to intersect the second straight line 22, for example, perpendicular to each other.
  • the first straight line 21 extends in the first direction
  • the second straight line 22 extends in the second direction
  • the first direction may be a horizontal direction
  • the second direction may be a vertical direction.
  • the grid image can be used to cover the entire imaging area of the image output device to better reflect the distortion of the output image of the image output device.
  • the extending direction of the first straight line and the second straight line may also be an oblique direction that is set at an angle to the horizontal direction.
  • the grid graphic may be an equally spaced grid graphic or an equiangular grid graphic.
  • the pitch between the straight lines 21, and Yn is the pitch between the nth first straight line 21 to the 0th first straight line 21 on the 0th first straight line 21 side.
  • the 0th first straight line is the horizontal center line of the grid pattern
  • the 0th second straight line is the vertical center line of the grid pattern.
  • the angle between the observation point O and the perpendicular lines of any two adjacent first straight lines 21 is set to a fixed angle A, and the observation point is set.
  • the angle between the perpendicular lines to any two adjacent second straight lines is also a fixed angle A.
  • A 1°.
  • it can also be set to other values according to actual conditions, such as 0.5°, 1.5°, 2°, and the like.
  • Yn represents the distance between the nth first straight line to the 0th first straight line on the 0th first straight line side
  • Xm represents the 0th second second side of the 0th second straight line side.
  • S is the set value.
  • S may be the distance between the set observation point to the imaging position of the image output device.
  • Equal-pitch mesh graphics are simpler to make, and the distribution of lines is more uniform, so it can better reflect the distortion of the image, so it is more convenient to use an equally spaced grid.
  • the test pattern may also include a plurality of parallel spaced lines, and the plurality of parallel spaced lines may extend in a horizontal direction, a vertical direction, or an oblique direction at a set angle with the horizontal direction.
  • the widths of the lines in the test pattern are equal.
  • the width of the line is a dimension in a direction perpendicular to the longitudinal direction of the line.
  • step S102 the test image is captured by the image acquisition device to obtain an image.
  • the imaged image is a picture taken when the image capturing device focuses on the imaging position of the image output device, and the image capturing device is set at a set observation point of the image output device.
  • an optimum viewing distance is usually set, and a rectangular area is provided as the optimal viewing area S0 (see FIG. 3) at the optimum viewing distance, which may be referred to as an eye box.
  • the set observation point may be the center point O of the rectangular area, that is, the intersection of the diagonal lines of the rectangle.
  • the most recent observation area S1 and the farthest observation area S2 are usually also provided, and the optimal observation area S0 is located between the most recent observation area S1 and the farthest observation area S2.
  • the rectangular region may have a length of 140 mm to 160 mm and a width of 40 mm to 60 mm. The horizontal height of the rectangular area can be set according to actual needs.
  • the center point O of the rectangular area can be set at the same level as the center point of the test image.
  • Setting the image acquisition device at the set observation point means that the center of the lens of the image acquisition device is located at the set observation point, and the center line of the lens is aligned with the center point of the test image.
  • the image acquisition device may be an illuminometer (for example, BM_7 (Chroma Brightness Tester manufactured by TOPCON Corporation of Japan)) or a Charge-coupled Device (CCD) camera or the like.
  • BM_7 Chroma Brightness Tester manufactured by TOPCON Corporation of Japan
  • CCD Charge-coupled Device
  • the step S102 may include: placing the reference object at an imaging position of the image output device, the distance between the imaging position and the set observation point is equal to setting the imaging distance;
  • the acquiring device focuses on the reference object, and takes a test image to obtain an image.
  • the method is suitable for the case where the imaging distance of the image output device is known.
  • the image acquisition device can be easily focused to the imaging position of the image output device and photographed, which is convenient and simple.
  • a reference figure is provided on the reference object, and the reference figure may be a m-shaped figure composed of four line segments intersecting at one point, the four line segments including the same line segment as the extending direction of the first straight line, And the angle between any two adjacent line segments is 45°.
  • the reference pattern is four diameters of a circle, and the angle between any two adjacent diameters of the four diameters is 45°.
  • the reference graphic may also be other graphics, such as any one of letters, numbers, words, or a combination of any two, or any combination of at least one of letters, numbers, and words and lines.
  • the reference object may include a bottom plate and a coating or sticker or the like disposed on one side of the bottom plate for displaying the reference graphic.
  • the reference may also be an electronic display for displaying a reference graphic.
  • the reference object may further be provided with a lifting mechanism and/or a translation mechanism for adjusting the height of the reference object in the Y direction (for example, the vertical direction), and the translation mechanism includes the X direction translation.
  • the mechanism and the Z-direction translation mechanism, the Z direction is the extension direction of the lens center line of the image acquisition device, and the X direction is perpendicular to the Y direction and the Z direction.
  • the lifting mechanism and the translation mechanism can adopt any existing mechanism, including but not limited to a rack and pinion moving mechanism, a screw moving mechanism, and the like.
  • the step S102 may include: adjusting a focal length of the image acquiring device at a set interval, and capturing a test image after each adjustment to obtain a plurality of image images; Among the image images, the clearest image is used as the image. Generally, when the image capturing device focuses on the imaging position of the image output device, the picture taken is the clearest, so the clearest image picture among the plurality of image pictures can be regarded as being taken when the image capturing device is focused on the imaging position of the image output device. image.
  • the set interval may be a scale on the lens of the image capture device, each time the lens is rotated by one scale.
  • the determining the clearest image image from the plurality of image images may include: determining a width of the set line in each image image; and using the image image to which the set line having the smallest width belongs as the imaged image.
  • determining a width of the set line in each image picture includes: determining a width of the set line at the plurality of measurement points, wherein the plurality of measurement points are arranged on the set line at intervals along an extending direction of the set line; The width of the set line is determined based on the width at a plurality of measurement points.
  • the set line refers to a line that sets a position in the image picture, and the set line may be at least one.
  • the setting lines in each image picture are the same.
  • the set line may be a line in the middle of the plurality of parallel lines.
  • the average value of the width values at the plurality of measurement points can be used as the width of the set line.
  • the set line may include a line in the grid pattern that is located in the middle in the first direction and a line that is in the middle in the second direction, ie, The cross centerline of the grid pattern (shown at 23 in Figure 2a).
  • the average value of the widths of the plurality of measurement points on each line can be separately calculated as the width of the corresponding line, and then the sum of the widths of the lines or the average of the widths of the lines can be used as the set line. The width.
  • setting the line also allows you to select multiple lines in the middle of the test pattern.
  • the image is accurately determined only by testing the width of the center line of the graphic, and the calculation process is simple, so the center line of the test pattern is often used as the setting line.
  • the number of measurement points on each line is at least 10 points.
  • the number of measurement points on the set line in the first direction is at least 10 points
  • the number of measurement points on the set line in the second direction is also For at least 10 points. It should be noted that the number of measurement points on the set line in the first direction may be the same as the number of measurement points on the set line in the second direction, or may be different, and may be set according to actual needs.
  • the setting of the measurement points on the set line of the grid pattern may be in the following manner: for the set line extending in the first direction, the setting between each adjacent two second lines may be A measuring point is set on the line; for the set line extending in the second direction, a measuring point can be set on the set line between each adjacent two first straight lines.
  • This method is also applicable to the case where the imaging distance of the image output device is known and unknown, and can be automatically determined by a smart device such as a computer, and the degree of automation is high.
  • the step S102 may include: manually adjusting a focal length of the image acquiring device and observing an imaging condition of the test image in the image acquiring device until the image capturing device focuses on the test image; Test the image for shooting to get an image.
  • step S103 it is determined whether the image distortion satisfies the requirement based on the width of the line in the imaged picture.
  • the line taken at the imaging position will become blurred and thicker, that is, the width of the line becomes larger, and the width of the line in the image is reflected by the degree of distortion of the image. Therefore, it can be based on the imaged image.
  • the width of the line determines if the image distortion meets the requirements. Whether or not the image distortion is satisfied based on the width of the line in the imaged image can be adopted in the manner shown in FIGS. 4 and 5, which will be described below in conjunction with FIGS. 4 and 5.
  • FIG. 4 is a flowchart of a method for detecting image distortion according to an embodiment of the present disclosure. As shown in FIG. 4, the method includes:
  • step S201 the image output device is controlled to output a test image.
  • step S202 the test image is captured by using an image acquisition device to obtain an image.
  • step S203 the maximum width value of the line in the imaged picture is determined.
  • the step S203 may include: converting the imaged image into a grayscale image; performing binarization processing on the grayscale image to obtain a binarized image; determining the binarized image, perpendicular to each
  • the number of pixels in the direction in which the line extends continuously is the set value; the maximum number is taken as the maximum width value of the line.
  • a CCD camera can be employed as the image acquisition device at a low cost.
  • the set value here means that the pixel is a line.
  • performing binarization processing on the grayscale image includes: comparing a grayscale value of each pixel point in the grayscale image with a set threshold, and marking a pixel point whose grayscale value is greater than a set threshold as the first value (For example, 1), indicating that the pixel belongs to a line, and marking a pixel whose gradation value is not greater than a set threshold as a second value (for example, 0), indicating that the pixel does not belong to a line.
  • the set threshold can be set according to the actual situation, as long as it can distinguish that the pixel points belong to a line or do not belong to a line.
  • the first value here is the set value in the first implementation.
  • the number of pixels of the set value may be determined by determining the number of pixels consecutively the first value row by row; determining the number of pixels consecutively the first value column by column, where the row direction is In the horizontal direction, the column direction is vertical. It can be seen that by using the grid pattern as the test pattern, the number of pixels consecutive to the first value can be determined by row-by-row column-by-column scanning, which is simple and convenient.
  • the step S203 may include: acquiring luminance data of each pixel in the imaged image; determining two edges of each line in the imaged image according to the brightness data; determining, for each line in the imaged image, vertical The spacing between the two edges in the direction of the direction in which the lines extend; the maximum spacing is taken as the maximum width of the line.
  • an illuminometer as the image acquisition means.
  • determining the two edges of each line in the imaged image according to the brightness data may be performed by determining a ratio of brightness of two pixel points adjacent in a direction perpendicular to an extending direction of the line; if the ratio is greater than or equal to The set value determines that the pixel with the higher brightness among the adjacent two pixels is the point on the edge of the line. If the ratio is less than the set value, it means that the two adjacent pixels are not points on the edge of the line.
  • the set value may be 10.
  • step S204 it is determined whether the depth of field distortion satisfies the requirement based on the maximum width value.
  • the step S204 can adopt any one of the following ways:
  • the depth of field distortion satisfies the requirement. If the ratio of the maximum width value to the specified line width is greater than the set value, the depth of field distortion does not satisfy the requirement; or,
  • the depth of field distortion satisfies the requirement. If the difference between the maximum width value and the specified line width is greater than the set value, the depth of field distortion does not satisfy the requirement; or
  • the depth of field distortion satisfies the requirement. If the maximum width value is greater than the set threshold, the depth of field distortion does not meet the requirements.
  • the line width is specified as the minimum width value or average width of the lines in the imaged picture or the width of the line (eg, the width of the aforementioned cross center line).
  • the minimum width value of the line can be referred to the manner of determining the aforementioned maximum width value, and a detailed description is omitted here.
  • the average width of the lines in the image is that all the lines in the image are processed according to the set line, the width of each line is obtained, and then the average of all the lines is taken to obtain the lines in the image. Average width.
  • FIG. 5 is a flowchart of another image distortion detecting method according to an embodiment of the present disclosure. As shown in Figure 5, the method includes:
  • step S301 the image output device is controlled to output a test image.
  • step S302 the test image is captured by the image acquisition device to obtain an image.
  • step S303 a position corresponding to the maximum width value of the line in the imaged picture is determined.
  • the line having the largest width value in the imaged image may be determined first, and the position of the line having the maximum width value is the position corresponding to the maximum width value of the line in the imaged image.
  • the manner of determining the line having the largest width value in the imaged picture can be referred to the aforementioned step S203, and a detailed description is omitted here.
  • the imaged image may also be visually observed to determine the position corresponding to the maximum width value of the line in the imaged image.
  • step S304 the focal length of the image acquisition device is adjusted such that the image acquisition device focuses on the position corresponding to the maximum width value.
  • step S304 causing the adjustment image acquisition means to focus on the position corresponding to the maximum width value means that the line corresponding to the position of the maximum width value can be clearly imaged in the image acquisition means.
  • the step S304 may include: adjusting a focal length of the image acquiring device at a set interval, and photographing the test image after each adjustment to obtain a plurality of image images; determining a line corresponding to the position of the maximum width value Width; when the difference between the width of the line corresponding to the position of the maximum width value and the width of the specified line does not exceed the set value, it is determined that the adjustment image acquisition means focuses on the position corresponding to the maximum width value.
  • the specified line width may be the minimum width value or the average width of the lines in the imaged picture or the width of the set line.
  • step S305 it is determined that the image acquisition device focuses on the focal length at the position corresponding to the maximum width value.
  • the step S305 can be implemented in the following manner: after the image acquiring device focuses on the position corresponding to the maximum width value, the reference object is placed in the focus position of the image acquiring device; the distance from the reference object to the image capturing device is determined as the image capturing device is focused. The focal length at the position corresponding to the maximum width value.
  • placing the reference object at the focus position of the image acquisition device includes: positioning the center of the reference object at a line connecting the center of the test image and the set observation point, and adjusting the distance of the reference object to the set observation point
  • the focal length when the image capturing device is focused on the position corresponding to the maximum width value can be determined according to the position of the reference object. It is simple and convenient to realize by artificially observing whether the reference object is located at the focus position of the image acquisition device.
  • placing the reference object in a focus position of the image acquisition device includes: positioning a center of the reference object on a line connecting the center of the test image and the set observation point, and focusing the image on the maximum width value After the corresponding position, the reference object is adjusted to the set observation point by the set distance interval, and after each adjustment of the reference object to the set observation point, the image acquisition device captures the reference object and the test image, and obtains First image
  • the reference object is circular, and if the reference object is tangent to the upper and lower third lines of the horizontal center line of the grid pattern and the left and right third lines of the vertical center line of the grid pattern in the second image, When the reference object is also tangent to the upper and lower third lines of the horizontal center line of the grid pattern and the left and right third lines of the vertical center line of the grid pattern in the first image, the reference object is located at the focus of the image acquisition device. position.
  • adjusting the distance of the reference object to the set observation point by the set distance interval may be adjusted within a certain range before and after the imaging distance of the image output device. Since the depth of field distortion of the image usually occurs at the front and rear positions of the imaging distance, adjustment within a certain range before and after the imaging distance of the image output device can reduce the number of adjustments in order to quickly determine the focus position of the image acquisition device.
  • a linear guide may be disposed in a linear direction of the center of the image acquisition device and the test image, and the reference object is disposed on the linear guide; the reference object is moved on the linear guide to facilitate control of the reference object relative to the image acquisition device s position.
  • the reference object 1 is disposed on the bracket 1a, and the bracket 1a is disposed on the linear guide 2, and the linear guide 2 is arranged along the line connecting the center of the lens of the image capturing device 3 and the center of the test image 4, as shown in the figure.
  • the bracket 1a can move along the linear guide 2, that is, in the Z direction.
  • the reference 1 is placed on the holder 1a, and the reference 1 can be moved in the X direction and the Y direction on the holder 1a.
  • the position of the reference object 1 can be moved in an automatic manner, for example, by using a motor or the like, or manually.
  • a scale 2a may be provided on or near the linear guide 2 to facilitate intuitive determination of the distance between the reference 1 and the image acquisition device 3.
  • a position sensor can be provided to detect the position of the reference object 1 on the linear guide 2 in real time and determine the distance between the reference object 1 and the image acquisition device 3 based on the detected position.
  • step S306 it is determined whether the depth of field distortion of the test image satisfies the requirement according to the focal length when the image acquisition device focuses on the widest line position.
  • the step S306 may include: determining that the image distortion satisfies the requirement when the image capturing device focuses on the position corresponding to the maximum width value is within the set range; and the focal length is not when the image acquiring device focuses on the position corresponding to the maximum width value When the setting range is within, it is determined that the image distortion does not meet the requirements.
  • the setting range is determined according to the focal length of the image capturing device when the imaged image is taken.
  • a ⁇ a, a is greater than 0
  • A is the focal length of the image acquisition device when shooting the image
  • a is determined according to the distortion requirements of the image output device, can be set according to actual requirements, the smaller the value of a, the requirement for image distortion The higher.
  • the focal length of the image acquiring device is adjusted based on the widest line in the imaged image, and whether the depth of field distortion of the image satisfies the requirement according to the focal length when the image acquiring device focuses on the widest line position, thereby realizing the image based on the image
  • the width of the line determines if the image distortion meets the requirements.
  • the actual physical position of the image acquisition device does not change, and the focus position of the image acquisition device is changed only by adjusting the focal length of the image acquisition device.
  • FIG. 7 is a schematic structural diagram of image distortion detecting according to an embodiment of the present disclosure.
  • the image distortion detecting system includes an image acquiring device 71 and a control device 72.
  • the image acquisition device 71 is configured to capture a test image output by the image output device to obtain an image, which is a picture taken when the image acquisition device focuses on an imaging position of the image output device, and the image acquisition device 71 is disposed in the image output device. Set the observation point.
  • Control device 72 is operative to determine if image distortion meets the requirements based on the width of the lines in the imaged image.
  • the image distortion detecting system may further include a reference object for being placed at an imaging position of the image output device, the distance between the imaging position and the set observation point being equal to the set imaging distance;
  • the image acquisition device 71 is configured to focus on the reference object and take a picture of the test image to obtain an image picture. This method is suitable for image output devices with a known imaging distance.
  • the image obtaining device 71 is configured to change the focal length at a set interval, and perform a shooting of the test image once after each change of the focal length to obtain a plurality of image images; and the control device 72 is configured to use the image image. Select the clearest image in the image as the image.
  • This method is also applicable to image output devices whose imaging distance is known or unknown. For the specific implementation process of the method, refer to the foregoing step S102, and details are not described herein.
  • the control device 72 determines whether the image distortion meets the requirements in one of two ways:
  • control device 62 is configured to determine a maximum width value of the line in the imaged image; when the maximum width value is not greater than the set threshold, determining that the image distortion satisfies the requirement; or, when the maximum width value is proportional to the specified line width
  • the threshold is not greater than the set threshold, it is determined that the image distortion satisfies the requirement; or, when the difference between the maximum width value and the specified line width is not greater than the set threshold, it is determined that the image distortion satisfies the requirement.
  • This implementation can use image processing technology to determine whether image distortion meets the requirements, high degree of automation, and simple system structure.
  • control device 72 is configured to determine a position corresponding to the maximum width value of the line in the image; adjust the focal length of the image acquisition device, so that the image acquisition device focuses on the position corresponding to the maximum width value; and determine that the image acquisition device is focused on The focal length at the position corresponding to the maximum width value; determining whether the image distortion satisfies the requirements according to the focal length when the image capturing device focuses on the position corresponding to the maximum width value.
  • a linear guide may be disposed in a linear direction of the image acquisition device (ie, the set observation point) and the center of the test image, and a reference object may be disposed on the linear guide; by moving the reference on the linear guide In order to control the position of the reference object relative to the image acquisition device.
  • a scale value on or near the linear guide may be provided to intuitively determine the distance between the reference object and the image acquisition device.
  • a position sensor may be provided to detect the position of the reference object on the linear guide in real time, and the control device may determine the distance between the reference object and the image acquisition device according to the detected position.
  • a focus adjustment device of the image acquisition device may be provided, which can rotate the lens of the image acquisition device under the control of the control device to adjust the focal length of the image acquisition device at set intervals.

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Abstract

公开了一种影像畸变检测方法和系统，属于显示系统测试技术领域。该方法包括：控制影像输出设备输出测试影像；采用图像获取装置对所述测试影像进行拍摄，得到成像图片，所述成像图片是所述图像获取装置聚焦在影像输出设备的成像位置时拍摄的图片，所述图像获取装置设置在影像输出设备的设定观察点；基于所述成像图片中线条的宽度确定影像畸变是否满足要求。本公开实施例可以用于检测影像输出设备输出的影像的景深畸变。

Description

影像畸变检测方法和系统
本申请要求于2017年11月30日提交、申请号为201711235491.8、发明名称为“影像畸变检测方法和系统”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本公开涉及显示系统测试技术领域，特别涉及一种影像畸变检测方法和系统。
背景技术
随着科技的进步，显示技术的应用越来越广泛。例如，虚拟影像显示技术和全息影像显示技术等逐步应用到人们的日常生活中。这类显示技术中，影像均不是在显示屏上成像，容易发生景深畸变。而在一些场景中，对于成像质量的要求较高，例如涉及到驾驶员人身安全的车载抬头显示器(Head-Up Display，HUD)，影像的景深畸变可能带来危险。因此，需要对输出影像的景深畸变进行检测。
发明内容
本公开实施例提供了一种影像畸变检测方法和系统，可以用于检测影像输出设备输出的影像的景深畸变。
本公开至少一实施例提供了一种影像畸变检测方法，包括：控制影像输出设备输出测试影像；采用图像获取装置对所述测试影像进行拍摄，得到成像图片，所述成像图片是所述图像获取装置聚焦在影像输出设备的成像位置时拍摄的图片，所述图像获取装置设置在影像输出设备的设定观察点；基于所述成像图片中线条的宽度确定影像畸变是否满足要求。
可选地，所述测试影像是影像输出设备输入测试图形后输出的影像，所述测试图形为等间距网格图形和等角度网格图形中的至少一种。
在本公开实施例的一种实施方式中，所述采用图像获取装置对所述测试影像进行拍摄，得到成像图片，包括：将参照物放置在影像输出设备的成像位置，所述成像位置与所述设定观察点之间的间距等于设定成像距离；使所述图像获 取装置聚焦在所述参照物上，对所述测试影像进行拍摄，得到所述成像图片。
在本公开实施例的另一种实施方式中，所述采用图像获取装置对所述测试影像进行拍摄，得到成像图片，包括：以设定间隔调节所述图像获取装置的焦距，并在每次调节后对所述测试影像进行一次拍摄，得到多个影像图片；从所述多个影像图片中选择最清晰的影像图片，作为所述成像图片。
可选地，所述从所述多个影像图片中选择最清晰的影像图片，作为所述成像图片，包括：确定各个所述影像图片中设定线条的宽度；将宽度最小的设定线条所属的影像图片作为所述成像图片。
可选地，所述确定各个影像图片中设定线条的宽度，包括：确定所述设定线条在多个测量点处的宽度，所述多个测量点沿所述设定线条的延伸方向间隔布置在所述设定线条上；根据所述多个测量点处的宽度确定所述设定线条的宽度。
在本公开实施例的一种实施方式中，所述基于所述成像图片中线条的宽度确定影像畸变是否满足要求，包括：确定所述成像图片中线条的最大宽度值；当所述最大宽度值不大于设定阈值时，确定影像畸变满足要求；或者，当所述最大宽度值与指定线条宽度的比值不大于设定阈值时，确定影像畸变满足要求；或者，当所述最大宽度值与指定线条宽度的差值不大于设定阈值时，确定影像畸变满足要求。
可选地，所述确定所述成像图片中线条的最大宽度值，包括：获取所述成像图片的亮度数据；根据所述亮度数据确定所述成像图片中各线条的两边缘；对于所述成像图片中的每根线条，确定在垂直于线条的延伸方向的方向上两边缘之间的间距；将确定出的所述间距中的最大间距作为所述线条的最大宽度值。
可选地，所述确定所述成像图片中线条的最大宽度值，包括：将所述成像图片转换为灰度图；对所述灰度图进行二值化处理，得到二值化图像；确定所述二值化图像中，在垂直于各线条的延伸方向上连续为设定值的像素点的个数；将确定出的像素点的个数中的最大个数作为所述线条的最大宽度值。
在本公开实施例的又一实施方式中，所述基于所述成像图片中线条的宽度确定影像畸变是否满足要求，包括：确定所述成像图片中线条的最大宽度值对应的位置；调整所述图像获取装置的焦距，使得所述图像获取装置聚焦在所述最大宽度值对应的位置；确定所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距；根据所述图像获取装置聚焦在所述最大宽度值对应的位置时的 焦距，确定影像畸变是否满足要求。
可选地，所述确定所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距，包括：在所述图像获取装置聚焦在所述最大宽度值对应的位置之后，将参照物置于能够在所述图像获取装置中清晰成像的位置；将所述参照物到所述设定观察点之间的距离，确定为所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距。
可选地，所述根据所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距，确定影像畸变是否满足要求，包括：当所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距在设定范围内时，确定影像畸变满足要求；当所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距不在设定范围内时，确定影像畸变不满足要求。
可选地，所述图像获取装置为照度计或者电荷耦合元件照相机。
可选地，所述影像输出设备包括抬头显示器或全息影像输出设备。
本公开至少一实施例还提供了一种影像畸变检测系统，包括：图像获取装置，用于对影像输出设备输出的测试影像进行拍摄，得到成像图片，所述成像图片是所述图像获取装置聚焦在所述影像输出设备的成像位置时拍摄的图片，所述图像获取装置设置在所述影像输出设备的设定观察点；控制装置，用于基于所述成像图片中线条的宽度确定影像畸变是否满足要求。
在本公开实施例的一种实施方式中，测试影像畸变检测系统还包括参照物，所述参照物用于放置在所述影像输出设备的成像位置，所述成像位置与所述设定观察点之间的间距等于设定成像距离；所述图像获取装置用于聚焦在所述参照物上，对所述测试影像进行拍摄，得到所述成像图片。
在本公开实施例的另一种实施方式中，所述图像获取装置用于以设定的间隔变化焦距，并在每次变化焦距后对所述测试影像进行一次拍摄，得到多个影像图片；所述控制装置用于从所述多个影像图片中选择最清晰的影像图片，作为所述成像图片。
可选地，所述控制装置，用于确定所述成像图片中线条的最大宽度值；当所述最大宽度值不大于设定阈值时，确定影像畸变满足要求；或者，当所述最大宽度值与指定线条宽度的比值不大于设定阈值时，确定影像畸变满足要求；或者，当所述最大宽度值与指定线条宽度的差值不大于设定阈值时，确定影像畸变满足要求。
可选地，所述控制装置，用于确定成像图片中线条的最大宽度值对应的位置；调整图像获取装置的焦距，使得所述图像获取装置聚焦在所述最大宽度值对应的位置；确定所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距；根据所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距，确定影像畸变是否满足要求。
可选地，所述图像获取装置为照度计或者电荷耦合元件照相机。
可选地，所述影像输出设备包括抬头显示器或全息影像输出设备。
附图说明
图1是本公开实施例提供的一种影像畸变检测方法的流程示意图；
图2a是本公开实施例提供的一种网格图形的示意图；
图2b是本公开实施例提供的等角度网格图形的示意图；
图3是本公开实施例提供的设定观察点的设置示意图；
图4是本公开实施例提供的另一种影像畸变检测方法的流程示意图；
图5是本公开实施例提供的又一种影像畸变检测方法的流程示意图；
图6是本公开实施例提供的聚焦位置检测方式的结构示意图；
图7是本公开实施例提供的一种影像畸变检测系统的示意图。
具体实施方式
为使本公开的原理和优点更加清楚，下面将结合附图对本公开实施方式作进一步地详细描述。
本公开实施例提供了一种影像畸变检测方法，图1为该影像畸变检测方法的流程示意图，如图1所示，该方法包括以下步骤。
在步骤S101中，控制影像输出设备输出测试影像。
这里，测试影像是影像输出设备输入测试图形后输出的影像。
在本实施例中，影像输出设备是指输出影像不在物理成像屏上成像的影像输出设备，例如HUD、全息影像输出设备等。影像输出设备输出的影像既可以是虚拟影像(例如HUD的输出影像)，也可以是真实影像(例如全息影像输出设备输出的全息影像)。
该步骤S101可以包括：点亮影像输出设备的显示源并将测试图形的图像数 据输入显示源，从而使得影像输出设备输出测试影像。以投射式HUD为例，投射式HUD通常包括显示源、光学系统和成像屏(通常为汽车前挡风玻璃)，其中，显示源用于根据输入的图像数据输出图形，该图形经过光学系统投射至成像屏，在成像屏的与显示源所在侧相反的一侧成像。
在本实施例中，测试图形可以为网格图形。图2a为本公开实施例提供的一种网格图形的示意图。如图2a所示，网格图形2包括多根平行间隔设置的第一直线21和多根平行间隔设置的第二直线22。第一直线21与第二直线22交叉设置，例如相互垂直。示例性地，第一直线21沿第一方向延伸，第二直线22沿第二方向延伸，第一方向可以为水平方向，第二方向可以为垂直方向。采用网格图形可以覆盖影像输出设备的整个成像区域，更好地反映影像输出设备输出影像的畸变。在其他实施例中，第一直线和第二直线的延伸方向也可以为与水平方向呈设定角度的倾斜方向。
可选地，该网格图形可以为等间距网格图形或者等角度网格图形。
在等间距网格图形中，任意相邻的两条第一直线21之间的间距相等，任意相邻的两条第二直线22之间的间距也相等，且任意相邻的两条第一直线21之间的间距等于任意相邻的两条第二直线22之间的间距。也就是说，图2a中的Xn＝nX1，这里，X1为多条第二直线22中最中间的一根第二直线22(记为第0根第二直线)和与之相邻的第二直线22之间的间距，而Xn为第0根第二直线一侧的第n根第二直线到第0根第二直线之间的间距。Y1＝X1，且Yn＝nY1，这里，Y1为多条第一直线21中最中间的一根第一直线21(记为第0根第一直线)和与之相邻的第一直线21之间的间距，而Yn为第0根第一直线21一侧的第n根第一直线21到第0根第一直线21之间的间距。当第一方向为水平方向且第二方向为垂直方向时，第0根第一直线即为网格图形的水平中心线，第0根第二直线即为网格图形的垂直中心线。
在等角度网格图形中，如图2b所示，设定观察点O到任意相邻的两条第一直线21的垂线之间的夹角均为固定角度A，并且设定观察点到任意相邻的两条第二直线的垂线之间的夹角也为固定角度A。图2b中仅以图2a中的第0根第二直线和第0根第二直线右侧的第1根第二直线之间的夹角以及第0根第二直线右侧的第1根第二直线和第2根第二直线之间的夹角为例进行说明。示例性地，A＝1°。当然，也可以根据实际情况设置为其他值，例如0.5°、1.5°、2°等。
当A＝1°时，可以按照以下公式确定各相邻的第一直线之间的距离和各相 邻的第二直线之间的距离：
Yn＝S*tan(n°)，
Xm＝S*tan(m°)，
这里，Yn表示第0根第一直线一侧的第n根第一直线到第0根第一直线之间的距离，Xm表示第0根第二直线一侧的第m根第二直线到第0根第二直线之间的距离，S为设定值。示例性地，S可以为设定观察点到影像输出设备的成像位置之间的距离。
等间距网格图形制作起来更简单，且线条的分布更均匀，因此能够更好地反应出影像的畸变，因此采用等间距网格更为方便。
在其他实施方式中，测试图形也可以包括多条平行间隔设置的线条，这多条平行间隔设置的线条的延伸方向可以为水平方向、竖直方向或者与水平方向呈设定角度的倾斜方向。
需要说明的是，测试图形中各条线条的宽度相等。其中，线条的宽度为与线条的长度方向垂直的方向上的尺寸。
在步骤S102中，采用图像获取装置对该测试影像进行拍摄，得到成像图片。
成像图片是图像获取装置聚焦在影像输出设备的成像位置时拍摄的图片，图像获取装置设置在影像输出设备的设定观察点。
对于影像输出设备而言，通常设置有最佳观看距离，并且在该最佳观看距离处设有一个矩形区域作为最佳观察区域S0(参见图3)，该矩形区域可以被称为眼盒。如图3所示，该设定观察点可以为矩形区域的中心点O，即矩形的对角线的交点。对于HUD而言，通常还设置有最近观察区域S1和最远观察区域S2，最佳观察区域S0位于最近观察区域S1和最远观察区域S2之间。示例性地，该矩形区域的长度可以为140mm～160mm，宽度可以为40mm～60mm。该矩形区域的水平高度可以根据实际需要设置，在测试过程中，可以将矩形区域的中心点O与测试影像的中心点设置在同一水平高度。将图像获取装置设置在设定观察点，是指图像获取装置的镜头的中心位于设定观察点处，且镜头的中心线对准测试影像的中心点。
示例性地，图像获取装置可以为照度计(例如BM_7(日本TOPCON公司生产的色度亮度测试仪))或电荷耦合元件(Charge-coupled Device，CCD)照相机等。采用照度计对影像进行拍摄，在获取成像图片的同时可以得到成像图片中每个像素点的亮度数据，例如像素点位置坐标和像素点位置坐标对应的亮 度数据。
在本公开实施例的一种实施方式中，该步骤S102可以包括：将参照物放置在影像输出设备的成像位置，该成像位置与设定观察点之间的间距等于设定成像距离；将图像获取装置聚焦在参照物上，对测试影像进行拍摄，得到成像图片。
该方式适用于影像输出设备的成像距离已知的情况，通过在成像位置处放置参照物，使得图像获取装置容易聚焦到影像输出设备的成像位置并进行拍摄，实现方便简单。
示例性地，参照物上设有参照图形，该参照图形可以为米字图形，该米字图形由相交于一点的四条线段组成，这四条线段包括与第一直线的延伸方向相同的线段，且任意相邻两条线段之间的夹角均为45°。例如，在本实施例中，参照图形为圆的四条直径，且四条直径中任意相邻的两条直径之间的夹角均为45°。当然，参照图形也可以为其他图形，例如包括字母、数字、文字的任意一种或者任意两种的组合，或者包括字母、数字和文字中的至少一种与线条的任意组合。
示例性地，参照物可以包括底板以及设置在底板的一侧面的涂层或贴画等，该涂层或贴画用于展示参照图形。在其他实施例中，该参照物还可以为电子显示屏，该电子显示屏用于展示参照图形。
为了便于调节参照物的位置，该参照物上还可以设置有升降机构和/或平移机构，升降机构用于调节参照物在Y方向(例如竖直方向)上的高度，平移机构包括X方向平移机构和Z方向平移机构，Z方向为图像获取装置的镜头中心线的延伸方向，X方向垂直于Y方向和Z方向。升降机构和平移机构可以采用现有任意的机构，包括但不限于齿轮齿条移动机构、丝杠移动机构等。
在本公开实施例的另一种实施方式中，该步骤S102可以包括：以设定间隔调节图像获取装置的焦距，并且在每次调节后对测试影像进行拍摄，得到多个影像图片；将多个影像图片中，最清晰的影像图片作为成像图片。通常，当图像获取装置聚焦在影像输出设备的成像位置时拍摄的图片最清晰，所以可以将多个影像图片中最清晰的影像图片认为是图像获取装置聚焦在影像输出设备的成像位置时拍摄的图片。
示例性地，设定间隔可以为图像获取装置镜头上的刻度，每次调节将镜头转动一个刻度。
可选地，从多个影像图片中，确定最清晰的影像图片的方式可以包括：确定各个影像图片中设定线条的宽度；将宽度最小的设定线条所属的影像图片作为成像图片。
可选地，确定各个影像图片中设定线条的宽度，包括：确定设定线条在多个测量点处的宽度，这多个测量点沿设定线条的延伸方向间隔布置在设定线条上；根据多个测量点处的宽度确定设定线条的宽度。
这里，设定线条是指影像图片中设定位置的线条，设定线条可以为至少一根。各个影像图片中的设定线条均相同。
例如，在测试图形为多条平行线的情况下，设定线条可以为多条平行线正中间的一根线条。在这种情况下，可以将多个测量点处的宽度值的平均值作为设定线条的宽度。
又例如，在测试图形为网格图形的情况下，设定线条可以包括网格图形中在第一方向上位于正中间的一根线条和在第二方向上位于正中间的一根线条，即网格图形的十字中心线(如图2a中的23所示)。在这种情况下，可以分别计算各条线条上的多个测量点的宽度的平均值，作为对应线条的宽度，然后将各线条的宽度之和或者各线条的宽度的平均值作为设定线条的宽度。
当然，设定线条还可以选择测试图形中位于中部的多根线条。但是通常情况下，仅通过测试图形的中心线的宽度就可以准确确定出成像图片，且计算过程简单，所以多选用测试图形的中心线作为设定线条。
为了保证确定出的线条的宽度的准确度，在每根线条上的测量点的数量均为至少10个点。例如，当设定线条为网格图形的十字中心线时，第一方向上的设定线条上测量点的数量为至少10个点，第二方向上的设定线条上的测量点的数量也为至少10个点。需要说明的是，第一方向上的设定线条上的测量点的数量与第二方向上的设定线条上的测量点的数量可以相同，也可以不同，可以根据实际需要设置。
示例性地，对于网格图形的设定线条上的测量点的设置可以采用以下方式：对于沿第一方向延伸的设定线条，可以在每相邻的两条第二直线之间的设定线条上设置一个测量点；对于沿第二方向延伸的设定线条，可以在每相邻的两条第一直线之间的设定线条上设置一个测量点。
该方式同时适用于影像输出设备的成像距离已知和未知的情况，并且可以通过计算机等智能设备自动确定，自动化程度高。
在本公开实施例的又一种实施方式中，该步骤S102可以包括：手动调节图像获取装置的焦距并观察测试影像在图像获取装置中的成像情况，直至图像获取装置聚焦在测试影像上；对测试影像进行拍摄，得到成像图片。
在步骤S103中，基于成像图片中线条的宽度确定影像畸变是否满足要求。
若影像产生了景深畸变，则在成像位置拍摄得到的线条将会变模糊变粗，即线条的宽度变大，成像图片中线条的宽度即反应了影像的畸变程度，因此，可以基于成像图片中线条的宽度来确定影像畸变是否满足要求。基于成像图片中线条的宽度确定影像畸变是否满足要求可以采用图4和图5所示的方式，下面将结合图4和图5分别进行说明。
图4为本公开实施例提供的一种影像畸变检测方法的流程图。如图4所示，该方法包括：
在步骤S201中，控制影像输出设备输出测试影像。
在步骤S202中，采用图像获取装置对该测试影像进行拍摄，得到成像图片。
该步骤S201和S202的实现方式可以参见前述步骤S101和S102，在此省略详细描述。
在步骤S203中，确定成像图片中线条的最大宽度值。
在第一种实现方式中，该步骤S203可以包括：将成像图片转换为灰度图；对灰度图进行二值化处理，得到二值化图像；确定二值化图像中，在垂直于各线条的延伸方向上连续为设定值的像素点的个数；将最大个数作为线条的最大宽度值。在这种实现方式中，可以采用CCD照相机作为图像获取装置，成本较低。这里的设定值表示该像素点为属于线条。
示例性地，对灰度图进行二值化处理，包括：将灰度图中各个像素点的灰度值与设定阈值比较，将灰度值大于设定阈值的像素点标记为第一值(例如1)，表示该像素点属于线条，将灰度值不大于设定阈值的像素点标记为第二值(例如0)，表示该像素点不属于线条。该设定阈值可以根据实际情况设定，只要能够区分出像素点属于线条或不属于线条即可。这里的第一值即为第一种实现方式中的设定值。
以前述第一直线和第二直线相互垂直且第一方向为水平方向、第二方向为垂直方向的网格图形为例，确定二值化图像中，在垂直于各线条的延伸方向上连续为设定值的像素点的个数可以采用以下方式：逐行确定连续为第一值的像 素点的个数；逐列确定连续为第一值的像素点的个数，这里，行方向为水平方向，列方向为垂直方向。可见，采用这种网格图形作为测试图形，可以采用逐行逐列扫描的方式确定连续为第一值的像素点的个数，实现简单方便。
在第二种实现方式中，该步骤S203可以包括：获取成像图片中各个像素点的亮度数据；根据亮度数据确定成像图片中各线条的两边缘；对于成像图片中的每根线条，确定在垂直于线条的延伸方向的方向上两边缘之间的间距；将最大间距作为线条的最大宽度值。在该实现方式中，由于需要利用成像图片的亮度数据，所以需要采用照度计作为图像获取装置。
示例性地，根据亮度数据确定成像图片中各线条的两边缘，可以采用以下方式：确定在垂直于线条的延伸方向的方向上相邻的两像素点的亮度的比值；若该比值大于或等于设定值，则确定相邻的两像素点中亮度较大的像素点为线条的边缘上的点。若该比值小于设定值，则表示相邻的两像素点均不是线条的边缘上的点。可选地，该设定值可以为10。
在步骤S204中，根据最大宽度值，判断景深畸变是否满足要求。
该步骤S204可以采用以下方式中的任意一种：
若最大宽度值和指定线条宽度的比值不大于设定值，则景深畸变满足要求，若最大宽度值和指定线条宽度的比值大于设定值，则景深畸变不满足要求；或者，
若最大宽度值和指定线条宽度的差值不大于设定值，则景深畸变满足要求，若最大宽度值和指定线条宽度的差值大于设定值，则景深畸变不满足要求；或者，
若最大宽度值不大于设定阈值时，则景深畸变满足要求，若最大宽度值大于设定阈值，则景深畸变不满足要求。
可选地，指定线条宽度为成像图片中的线条的最小宽度值或者平均宽度或者设定线条的宽度(例如前述十字中心线的宽度)。这里，线条的最小宽度值可以参见前述最大宽度值的确定方式，在此省略详细描述。设定线条的宽度的确定方式可以参见前述步骤S102的相关描述。而成像图片中的线条的平均宽度即将成像图片中的所有线条都按照设定线条的方式进行处理，得到每条线条的宽度，然后再取所有线条宽度的平均值，得到成像图片中的线条的平均宽度。
图5为本公开实施例提供的另一种影像畸变检测方法的流程图。如图5所 示，该方法包括：
在步骤S301中，控制影像输出设备输出测试影像。
在步骤S302中，采用图像获取装置对该测试影像进行拍摄，得到成像图片。
该步骤S301和S302的实现方式可以参见前述步骤S101和S102，在此省略详细描述。
在步骤S303中，确定成像图片中线条的最大宽度值对应的位置。
可选地，可以先确定出成像图片中具有最大宽度值的线条，该具有最大宽度值的线条所在的位置即为成像图片中线条的最大宽度值对应的位置。确定成像图片中具有最大宽度值的线条的方式可以参见前述步骤S203，在此省略详细描述。
可选地，也可以肉眼观察成像图片，确定出成像图片中线条的最大宽度值对应的位置。
在步骤S304中，调整图像获取装置的焦距，使得图像获取装置聚焦在最大宽度值对应的位置。
在该步骤S304中，使得调节图像获取装置聚焦在最大宽度值对应的位置是指最大宽度值对应位置的线条能够在图像获取装置中清晰成像。
在一种实现方式中，该步骤S304可以包括：以设定间隔调节图像获取装置的焦距，并在每次调节后对测试影像进行拍摄，得到多个影像图像；确定最大宽度值对应位置的线条的宽度；当最大宽度值对应位置的线条的宽度与前述指定线条宽度的差值不超过设定值时，确定调节图像获取装置聚焦在最大宽度值对应的位置。这里，指定线条宽度可以为成像图片中的线条的最小宽度值或者平均宽度或者设定线条的宽度。
在另一种实现方式中，可以人为判断图像获取装置是否聚焦在最大宽度值对应的位置。
在步骤S305中，确定图像获取装置聚焦在最大宽度值对应的位置时的焦距。
该步骤S305可以采用以下方式实现：在图像获取装置聚焦在最大宽度值对应的位置之后，将参照物置于图像获取装置的聚焦位置；将参照物到图像获取装置的距离，确定为图像获取装置聚焦在最大宽度值对应的位置时的焦距。
在一种实现方式中，将参照物置于图像获取装置的聚焦位置，包括：使参照物的中心位于测试影像的中心与设定观察点的连线上，调节参照物到设定观察点的距离，当观察到参照物清晰成像时，即可以根据参照物的位置确定图像 获取装置聚焦在最大宽度值对应的位置时的焦距。通过人为观察参照物是否位于图像获取装置的聚焦位置，实现起来简单方便。
在另一种实现方式中，将参照物置于图像获取装置的聚焦位置，包括：使参照物的中心位于测试影像的中心与设定观察点的连线上，在图像获取装置聚焦在最大宽度值对应的位置之后，以设定距离间隔调节参照物到设定观察点的距离，并在每次调节参照物到设定观察点的距离后，图像获取装置对参照物和测试影像进行拍摄，得到第一图像；
将第一图像中参照物相对于测试影像的位置与第二图像中参照物相对于测试影像的位置进行比较，若第一图像中参照物相对于测试影像的位置与第二图像中参照物相对于测试影像的位置相同，则表示参照物位于图像获取装置的聚焦位置，第二图像是参照物位于影像输出设备的成像位置时，采用图像获取装置聚焦在该成像位置对参照物和测试影像进行拍摄得到的图像。
例如，假设参照物为圆形，若第二图像中，参照物分别与网格图形的水平中心线的上下第三根线条以及网格图形的垂直中心线的左右第三根线条相切，则当第一图像中，参照物也与网格图形的水平中心线的上下第三根线条以及网格图形的垂直中心线的左右第三根线条相切时，表示参照物位于图像获取装置的聚焦位置。
示例性地，以设定距离间隔调节参照物到设定观察点的距离，可以在影像输出设备的成像距离前后一定范围内调节。由于影像的景深畸变通常发生在成像距离的前后位置，所以在影像输出设备的成像距离前后一定范围内调节可以减少调节次数，以便于快速确定图像获取装置的聚焦位置。
示例性地，可以在图像获取装置和测试影像的中心所在直线方向上设置直线导轨，并将参照物设置在直线导轨上；在直线导轨上移动参照物，以便于控制参照物相对于图像获取装置的位置。如图6所示，参照物1设置在支架1a上，支架1a设置在直线导轨2上，直线导轨2沿图像获取装置3的镜头的中心和测试影像4的中心的连线方向布置，如图中箭头a所示，支架1a可以沿直线导轨2移动，即沿Z方向移动。参照物1设置在支架1a上，参照物1可以在支架1a上沿X方向和Y方向移动。实现时，参照物1的位置移动可以采用自动方式，例如采用电机等驱动，也可以采用手动方式。
在一种实现方式中，如图6所示，可以在直线导轨2上或者附近设置刻度2a，以便于直观地确定参照物1与图像获取装置3之间的距离。在另一种实现 方式中，可以设置位置传感器，实时检测参照物1在直线导轨2上的位置，并根据检测到的位置确定参照物1与图像获取装置3之间的距离。
在步骤S306中，根据图像获取装置聚焦在最宽线条位置时的焦距，确定测试影像的景深畸变是否满足要求。
该步骤S306可以包括：当图像获取装置聚焦在最大宽度值对应的位置时的焦距在设定范围内时，确定影像畸变满足要求；当图像获取装置聚焦在最大宽度值对应的位置时的焦距不在设定范围内时，确定影像畸变不满足要求。
示例性地，设定范围根据拍摄成像图片时图像获取装置的焦距确定。通常为A±a，a大于0，A为拍摄成像图片时图像获取装置的焦距，a根据对影像输出设备的畸变要求确定，可以根据实际要求设置，a的值越小，对于影像畸变的要求越高。
在本实施例中，基于成像图片中最宽线条调节图像获取装置的焦距，并根据图像获取装置聚焦在最宽线条位置时的焦距确定影像的景深畸变是否满足要求，从而实现了基于成像图片中线条的宽度确定影像畸变是否满足要求。
需要说明的是，在本公开实施例提供的测试方法中，图像获取装置的实际物理位置不变，仅通过调节图像获取装置的焦距来改变图像获取装置的聚焦位置。
本公开实施例还提供了一种影像畸变检测系统，图7为本公开实施例提供的影像畸变检测的结构示意图。如图7所示，该影像畸变检测系统包括：图像获取装置71和控制装置72。图像获取装置71用于对影像输出设备输出的测试影像进行拍摄，得到成像图片，该成像图片是图像获取装置聚焦在影像输出设备的成像位置时拍摄的图片，图像获取装置71设置在影像输出设备的设定观察点。控制装置72用于基于成像图片中线条的宽度确定影像畸变是否满足要求。
在一种实现方式中，该影像畸变检测系统还可以包括参照物，该参照物用于放置在影像输出设备的成像位置，该成像位置与设定观察点之间的间距等于设定成像距离；图像获取装置71用于聚焦在参照物上，对测试影像进行拍摄，得到影像图片。该方式适用于成像距离已知的影像输出设备。
在另一种实现方式中，图像获取装置71用于以设定的间隔变化焦距，并在每次变化焦距后对测试影像进行一次拍摄，得到多个影像图片；控制装置72用于从影像图片中选择最清晰的影像图片，作为成像图片。该方式同时适用于成像距离已知或未知的影像输出设备。该方式的具体实现过程可以参见前述步骤 S102，在此不在赘述。
控制装置72确定影像畸变是否满足要求可以采用以下两种方式中的一种：
第一种实现方式、控制装置62用于确定成像图片中线条的最大宽度值；当最大宽度值不大于设定阈值时，确定影像畸变满足要求；或者，当最大宽度值与指定线条宽度的比值不大于设定阈值时，确定影像畸变满足要求；或者，当最大宽度值与指定线条宽度的差值不大于设定阈值时，确定影像畸变满足要求。第一种实现方式的具体实现过程可以参见图4所示实施例的相关描述，在此省略详细描述。这种实现方式可以利用图像处理技术确定影像畸变是否满足要求，自动化程度高，系统结构简单。
第二种实现方式、控制装置72用于确定成像图片中线条的最大宽度值对应的位置；调整图像获取装置的焦距，使得图像获取装置聚焦在最大宽度值对应的位置；确定图像获取装置聚焦在最大宽度值对应的位置时的焦距；根据图像获取装置聚焦在最大宽度值对应的位置时的焦距，确定影像畸变是否满足要求。
在第二种实现方式中，还可以在图像获取装置(即设定观察点)和测试影像的中心所在直线方向上设置直线导轨，并在直线导轨上设置参照物；通过在直线导轨上移动参照物，以便于控制参照物相对于图像获取装置的位置。
可选地，还可以在直线导轨上或者附近设置刻度值，以便于直观地确定参照物与图像获取装置之间的距离。在另一种实现方式中，可以设置位置传感器，实时检测参照物在直线导轨上的位置，控制装置可以根据检测到的位置确定参照物与图像获取装置之间的距离。
可选地，还可以设置图像获取装置的焦距调节装置，该焦距调节装置可以在控制装置的控制下转动图像获取装置的镜头，从而以设定间隔调节图像获取装置的焦距。
图像获取装置、参照物的布置方式可以参见图6及其相关描述，在此不再赘述。
以上所述仅为本公开的可选实施例，并不用以限制本申请的范围，凡在本公开的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请所附权利要求限定的保护范围之内。

Claims (20)

  1. 一种影像畸变检测方法，包括：
    控制影像输出设备输出测试影像；
    采用图像获取装置对所述测试影像进行拍摄，得到成像图片，所述成像图片是所述图像获取装置聚焦在所述影像输出设备的成像位置时拍摄的图片，所述图像获取装置设置在所述影像输出设备的设定观察点；
    基于所述成像图片中线条的宽度确定影像畸变是否满足要求。
  2. 根据权利要求1所述的影像畸变检测方法，其中，所述测试影像是所述影像输出设备输入测试图形后输出的影像，所述测试图形为等间距网格图形、等角度网格图形中的至少一种。
  3. 根据权利要求1所述的影像畸变检测方法，其中，所述采用图像获取装置对所述测试影像进行拍摄，得到成像图片，包括：
    将参照物放置在所述影像输出设备的成像位置，所述成像位置与所述设定观察点之间的间距等于设定成像距离；
    使所述图像获取装置聚焦在所述参照物上，对所述测试影像进行拍摄，得到所述成像图片。
  4. 根据权利要求1所述的影像畸变检测方法，其中，所述采用图像获取装置对所述测试影像进行拍摄，得到成像图片，包括：
    以设定间隔调节所述图像获取装置的焦距，并在每次调节后对所述测试影像进行一次拍摄，得到多个影像图片；
    从所述多个影像图片中选择最清晰的影像图片，作为所述成像图片。
  5. 根据权利要求4所述的影像畸变检测方法，其中，所述从所述多个影像图片中选择最清晰的影像图片，作为所述成像图片，包括：
    确定各个所述影像图片中设定线条的宽度；
    将宽度最小的设定线条所属的影像图片作为所述成像图片。
  6. 根据权利要求5所述的影像畸变检测方法，其中，所述确定各个所述影像图片中设定线条的宽度，包括：
    确定所述设定线条在多个测量点处的宽度，所述多个测量点沿所述设定线条的延伸方向间隔布置在所述设定线条上；
    根据所述多个测量点处的宽度确定所述设定线条的宽度。
  7. 根据权利要求1-6任一项所述的影像畸变检测方法，其中，所述基于所述成像图片中线条的宽度确定影像畸变是否满足要求，包括：
    确定所述成像图片中线条的最大宽度值；
    当所述最大宽度值不大于设定阈值时，确定影像畸变满足要求；或者，
    当所述最大宽度值与指定线条宽度的比值不大于设定阈值时，确定影像畸变满足要求；或者，
    当所述最大宽度值与指定线条宽度的差值不大于设定阈值时，确定影像畸变满足要求。
  8. 根据权利要求7所述的影像畸变检测方法，其中，所述确定所述成像图片中线条的最大宽度值，包括：
    获取所述成像图片的亮度数据；
    根据所述亮度数据确定所述成像图片中各线条的两边缘；
    对于所述成像图片中的每根线条，确定在垂直于线条的延伸方向的方向上两边缘之间的间距；
    将确定出的所述间距中的最大间距作为所述线条的最大宽度值。
  9. 根据权利要求7所述的影像畸变检测方法，其中，所述确定所述成像图片中线条的最大宽度值，包括：
    将所述成像图片转换为灰度图；
    对所述灰度图进行二值化处理，得到二值化图像；
    确定所述二值化图像中，在垂直于各线条的延伸方向上连续为设定值的像素点的个数；
    将确定出的像素点的个数中的最大个数作为所述线条的最大宽度值。
  10. 根据权利要求1-6任一项所述的影像畸变检测方法，其中，所述基于所述成像图片中线条的宽度确定影像畸变是否满足要求，包括：
    确定所述成像图片中线条的最大宽度值对应的位置；
    调整所述图像获取装置的焦距，使得所述图像获取装置聚焦在所述最大宽度值对应的位置；
    确定所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距；
    根据所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距，确定影像畸变是否满足要求。
  11. 根据权利要求10所述的影像畸变检测方法，其中，所述确定所述图像 获取装置聚焦在所述最大宽度值对应的位置时的焦距，包括：
    在所述图像获取装置聚焦在所述最大宽度值对应的位置之后，将参照物置于所述图像获取装置的聚焦位置；
    将所述参照物到所述设定观察点之间的距离，确定为所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距。
  12. 根据权利要求10所述的影像畸变检测方法，其中，所述根据所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距，确定影像畸变是否满足要求，包括：
    当所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距在设定范围内时，确定影像畸变满足要求；
    当所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距不在设定范围内时，确定影像畸变不满足要求。
  13. 一种影像畸变检测系统，包括：
    图像获取装置，用于对影像输出设备输出的测试影像进行拍摄，得到成像图片，所述成像图片是所述图像获取装置聚焦在所述影像输出设备的成像位置时拍摄的图片，所述图像获取装置设置在所述影像输出设备的设定观察点；
    控制装置，用于基于所述成像图片中线条的宽度确定影像畸变是否满足要求。
  14. 根据权利要求13所述的影像畸变检测系统，还包括参照物，
    所述参照物用于放置在所述影像输出设备的成像位置，所述成像位置与所述设定观察点之间的间距等于设定成像距离；
    所述图像获取装置用于聚焦在所述参照物上，对所述测试影像进行拍摄，得到影像图片。
  15. 根据权利要求14所述的影像畸变检测系统，还包括设置在所述设定观察点和所述测试影像的中心所在直线上的直线导轨，所述参照物设置在所述直线导轨上。
  16. 根据权利要求13所述的影像畸变检测系统，其中，所述图像获取装置用于以设定的间隔变化焦距，并在每次变化焦距后对所述测试影像进行一次拍摄，得到多个影像图片；所述控制装置用于从所述多个影像图片中选择最清晰的影像图片，作为所述成像图片。
  17. 根据权利要求13-16任一项所述的影像畸变检测系统，其中，所述控制 装置，用于确定所述成像图片中线条的最大宽度值；当所述最大宽度值不大于设定阈值时，确定影像畸变满足要求；或者，当所述最大宽度值与指定线条宽度的比值不大于设定阈值时，确定影像畸变满足要求；或者，当所述最大宽度值与指定线条宽度的差值不大于设定阈值时，确定影像畸变满足要求。
  18. 根据权利要求13-16任一项所述的影像畸变检测系统，其中，所述控制装置，用于确定成像图片中线条的最大宽度值对应的位置；调整图像获取装置的焦距，使得所述图像获取装置聚焦在所述最大宽度值对应的位置；确定所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距；根据所述图像获取装置聚焦在所述最大宽度值对应的位置时的焦距，确定影像畸变是否满足要求。
  19. 根据权利要求13-18任一项所述的影像畸变检测方法，其中，所述图像获取装置为照度计或者电荷耦合元件照相机。
  20. 根据权利要求13-18任一项所述的影像畸变检测方法，其中，所述影像输出设备包括抬头显示器或全息影像输出设备。
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