Office table board flatness defect measuring method capable of projecting defect area pattern

Abstract

The invention provides an office table board flatness defect measurement method capable of projecting defect area patterns, a medium and equipment, and relates to the technical field of flatness measurement. Comprising the following steps: projecting light beams on an office table board from at least three light source positions at a fixed height around the office table board, and collecting a projection image of the surface of the office table board; segmenting the projection image into a plurality of first areas; measuring the relative brightness of each first area of the projection image, and dividing the first area into a backlight area, a surface light area and a plane area; combining the adjacent backlight area and surface light area into a suspected defect area; and calculating the sum of the absolute values of the areas or the relative brightness of the suspected defect region corresponding to all the light source positions as a defect value, and if the maximum defect value is greater than a preset corresponding threshold value, judging that the suspected defect region is a confirmed defect region. According to the invention, the influence of original patterns or figures on the office table board can be avoided, so that the accuracy of flatness measurement is improved.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application is a divisional application based on the Chinese patent application with application number 202411141590X, application date: August 20, 2024, and invention name: "A method, medium and equipment for measuring the flatness defects of office desk panels". Technical Field

[0002] The invention relates to the technical field of flatness measurement, and in particular to a method, medium and equipment for measuring flatness defects of an office desk panel. Background Art

[0003] In the production and manufacturing process of office desks, with the development of technology, the requirements for quality control are getting higher and higher. Among them, the office desk board is one of the most important parts for users, and its flatness has the greatest impact on the user experience.

[0004] In traditional technology, mechanical devices are mostly used to measure the flatness of desktops, such as the Chinese patent applications with publication numbers CN207976105U and CN214010202U. However, during use, technicians found that the matching accuracy of the sliding parts in these mechanical devices directly affects the accuracy of flatness measurement, and there is also a large error in reading the scale by naked eyes.

[0005] Therefore, on this basis, technicians have developed a flatness measurement method based on image processing, such as the Chinese patent application with publication number CN113310438A. This application obtains an initial fringe image including a number of equally spaced linear stripes; and projects the initial fringe image onto the surface to be measured, so that the wall to be measured, which originally lacks texture information and geometric structure, will have distorted stripes in the fringe projection image projected on the wall due to the protrusions or depressions in the wall to be measured, thereby forming a fringe projection image carrying depth information on the wall to be measured, and by collecting the fringe projection image; and according to the fringe bending characteristics and fringe sparse characteristics in the fringe projection image, the flatness information of the surface to be measured is determined.

[0006] However, it was found during use that if the surface to be measured has a pattern, the original pattern will interfere with the projected fringe image, causing interference in the extraction of fringe bending features and fringe sparse features. Therefore, the above solution is more suitable for pure color surfaces without patterns or surfaces with simple patterns, but it is not accurate for measuring desktops with complex patterns (such as wooden tabletops).

[0007] Therefore, how to develop a flatness measurement solution that can be applicable to office desk panels that originally have patterns / patterns is one of the problems that need to be solved urgently. Summary of the invention

[0008] The purpose of the present invention is to provide a method, medium and equipment for measuring the flatness defects of an office desk panel, which can avoid the influence of the original pattern or pattern of the office desk panel, thereby improving the accuracy of flatness measurement.

[0009] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a method for measuring flatness defects of an office desk panel, comprising the following steps: S1, sequentially projecting light beams onto the desk board from at least three light source positions at fixed heights around the desk board, and collecting projection images of the surface of the desk board respectively; S2, dividing the projection image into a plurality of first regions; S3, measuring the relative brightness of each first area of ​​the projection image at each light source position, and dividing the first area into a backlight area, a surface light area and a plane area according to the relative brightness; S4, merging the adjacent backlight area and surface light area into a suspected defect area; S5, for each suspected defect area, calculate the sum of the absolute values ​​of the area or relative brightness of the suspected defect area corresponding to all light source positions as its defect value. If the maximum defect value is greater than the preset corresponding threshold, the suspected defect area is determined to be a confirmed defect area.

[0010] In some embodiments of the first aspect of the present invention, in S3, the relative brightness is measured as follows: S301, converting the image of the projection image in each first region into a grayscale image, traversing all pixels of the grayscale image, and calculating an average value of the grayscale values ​​as the brightness of each first region of the projection image; S302, obtaining a standard image corresponding to the same light source position, and calculating the brightness of each first area of ​​the standard image according to the step of S301; S303: Subtract the brightness of the first area corresponding to the projection image from the brightness of the first area corresponding to the standard image to obtain the relative brightness of the first area.

[0011] In certain embodiments of the first aspect of the present invention, the at least three light sources are located at the same height and are distributed in a circular array, and the center of the circular array is located directly above the center of the desk panel.

[0012] In some embodiments of the first aspect of the present invention, in S3, the method of dividing the first area into a backlight area, a surface light area and a plane area according to the relative brightness is as follows: Setting a first threshold value less than zero and a second threshold value greater than zero; If the relative brightness is less than a first threshold, the corresponding first area is a surface light area; If the relative brightness is greater than a second threshold, the corresponding first area is a backlight area; If the relative brightness is between the first threshold and the second threshold, the corresponding first area is a plane area.

[0013] In certain embodiments of the first aspect of the present invention, in said S4, the following steps are further included: S411, further dividing the first area where the backlight area / front light area located at the edge of the suspected defect area is located into second areas; S412, dividing the second area into a backlight area, a surface light area and a plane area according to the relative brightness; S413, removing the second area divided into the plane area from the original suspected defect area.

[0014] In certain embodiments of the first aspect of the present invention, said S3 further comprises the following steps: S421, further dividing the first region where the plane region located at the edge of the suspected defect region is located into a third region; S422, dividing the third area into a backlight area, a surface light area and a plane area according to the relative brightness; S423, adding the second area divided into the backlight area and the surface light area to the original suspected defect area.

[0015] In certain embodiments of the first aspect of the present invention, when adjacent backlight areas and surface light areas are merged into a suspected defect area, if there is a plane area between the adjacent backlight areas and surface light areas, the plane area between the adjacent backlight areas and surface light areas is merged into the suspected defect area.

[0016] In certain embodiments of the first aspect of the present invention, in S5, the confirmed defect area is further divided into a concave portion and a convex portion, and the distinguishing method is as follows: Determine the arrangement order of adjacent backlight areas and surface light areas along the projection light beam direction corresponding to the confirmed defect area. If the surface light area is located in front of the backlight area, the confirmed defect area is divided into a recessed portion; if the backlight area is located in front of the surface light area, the confirmed defect area is divided into a raised portion.

[0017] In a second aspect, the present invention provides a non-transitory storage medium, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the steps of a method for measuring flatness defects of an office desk panel as described in the first aspect.

[0018] In a third aspect, the present invention provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of a method for measuring flatness defects of an office desk panel as described in the first aspect are implemented.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention analyzes the relative brightness of multiple first areas of the surface image of the office desk board, thereby distinguishing the fleshy backlight area and the surface light area. Combining the different effects of uneven positions on light reflection, it can be seen that whether it is a concave part or a convex part, there will be adjacent backlight areas and surface light areas. Therefore, the distinguished adjacent backlight areas and surface light areas are merged to obtain the suspected defect area; and combined with the requirements for flatness, the area or relative brightness of the suspected defect area is further judged as a confirmed defect area. This method is judged by relative brightness, so it will not be affected by the original pattern / pattern on the surface of the office desk board.

[0020] 2. Since the defective parts of the office desks have different shapes, they may be circular, elliptical, or other irregular shapes. Under the projection of light beams at different angles, the defect values ​​(i.e., the sum of the absolute values ​​of the area or relative brightness) of the suspected defective areas of these irregular shapes are also different. If a fixed light source is used for detection, missed detection may occur. Therefore, the present invention uses at least three light source positions to transmit light beams, and in the final judgment, for the same suspected defective area, the maximum defect value is taken for judgment, thereby avoiding missed detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall process of the present invention.

[0022] Figure 2 Schematic diagram of light source position distribution of the present invention.

[0023] Figure 3 It is a schematic diagram of dividing a projection image into a first area according to the present invention.

[0024] Figure 4 Schematic diagram of light refraction in the concave part.

[0025] Figure 5 Schematic diagram of light refraction on a raised part.

[0026] Figure 6 It is a partial schematic diagram of the backlight area, the surface light area and the plane area of ​​the present invention.

[0027] Figure 7 It is a schematic diagram of merging adjacent backlight areas and surface light areas into a suspected defect area according to the present invention.

[0028] Figure 8 It is a schematic diagram of further dividing the backlight area into second areas according to the present invention.

[0029] Fig. 9This is a schematic diagram of further dividing the plane area into second areas according to the present invention.

[0030] Fig.10 This is a schematic diagram of the suspected defect area after refinement of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Embodiment 1: Please refer to Figure 1 This embodiment provides a method for measuring the flatness defects of an office desk panel, comprising the following steps: S1, projecting light beams onto the desk board from at least three light source positions at fixed heights around the desk board in sequence, and collecting projection images on the surface of the desk board respectively.

[0033] like Figure 2 As shown, in order to facilitate the installation of the office desk and the light source, this embodiment is provided with a mounting groove 2 for fixing the office desk 1. An annular track 3 is provided on the periphery of the mounting groove 2, a slider 4 is slidably fitted on the annular track 3, a light source 5 is fixedly installed on the top of the slider 4, and when the light source 5 is turned on, a light beam is projected toward the center of the office desk 1.

[0034] It is worth mentioning that although this embodiment requires at least three light source positions, at any time, only one of the light sources 5 needs to be lit. Therefore, in order to save the production cost of the device, this embodiment adopts the sliding cooperation of the above-mentioned annular track 3 and slider 4 to realize the switching of the position of the light source 5.

[0035] like Figure 2 In the figure, the light source 5 is initially located at the light source position a1 where the solid line is located, and the light beam is projected onto the upper surface of the desk board 1 as shown by the dashed line. It should be noted that the shape of the light beam is not limited, and it only needs to cover the upper surface of the desk board 1. Whether it is projected onto a position outside the desk board 1 is not limited.

[0036] At other times, the slider 4 moves along the circular track 3, and the light source 5 can be located at the light source position a2 or the light source position a3 where the dotted line is located, and also project a light beam onto the upper surface of the desk board 1. Preferably, the slider 4 of this embodiment is driven to move by a built-in motor, and the motor is connected to the controller via wired / wireless means.

[0037] The light source positions a1 , a2 , a3 and other light source positions are preferably at the same height and distributed in a circular array, with the center of the circular array being located directly above the center of the desk panel 1 .

[0038] At each light source position, a camera 6 is set just above the desk board 1 to collect projection images on the desk board surface and number them. For example, the projection image collected from the light beam at the light source position a1 is , correspondingly, the projection images collected from the light beams at the light source positions a2 and a3 are , .

[0039] S2, dividing the projection image into a plurality of first regions; like Figure 3 As shown, any projected image (including , , ) is divided into 8×16=128 first regions, and all the first regions are numbered respectively to obtain the first regions To the first area .

[0040] S3, measuring the relative brightness of each first area of ​​the projection image at each light source position, and dividing the first area into a backlight area, a surface light area and a plane area according to the relative brightness.

[0041] like Figure 4 As shown, for the concave portion on the surface of the desk board 1, the area between the dotted line o1 and the dotted line o2 is backlight, and the reflected light in this range is sparser than the plane after refraction, and the area shows lower brightness in the projection image obtained from above. On the contrary, the area between the dotted line o2 and the dotted line o3 is surface light, and the reflected light in this range is denser than the plane after refraction, and the area shows higher brightness in the projection image obtained from above.

[0042] Similarly, if Figure 5 As shown, for the raised part of the surface of the desk board 1, its performance is opposite to that of the recessed part. Between the dotted line o1 and the dotted line o2 is the surface light, and the reflected light in this range is denser than the plane after refraction. In the projected image obtained from above, this area shows higher brightness. Conversely, between the dotted line o2 and the dotted line o3 is the backlight, and the reflected light in this range is sparser than the plane after refraction. In the projected image obtained from above, this area shows lower brightness.

[0043] Therefore, by comparing the relative brightness of the first area in the projection image of the office desk to be measured with that of the corresponding first area in the standard image of a standard office desk (i.e., no depressions or projections on the surface), it can be determined whether the first area of ​​the office desk to be measured is a backlight area or a surface light area, thereby determining whether it has a depression or a projection.

[0044] It should be noted that the standard image and the projection image of the office desk to be measured are collected by transmitting light beams from the same light source position.

[0045] That is to say, before the actual measurement, the standard office desk board is collected according to the method of step S1 to obtain multiple standard images of the surface of the standard office desk board. For example, a light beam is projected from the light source position a1 to collect the standard images. , accordingly, the standard image is collected from the light source positions a2 and a3. , standard image .

[0046] The relative brightness is measured as follows: S301, converting the image of the projection image in each first area into a grayscale image, traversing all pixels of the grayscale image, and calculating an average value of the grayscale values ​​as the brightness of each first area of ​​the projection image.

[0047] The projection image is divided into 128 first regions. For example, through the above calculation, the brightness values ​​of the 128 first regions are obtained, which are respectively recorded as to ; The superscript represents the number of the projection image / standard image, and the subscript represents the number of the first area. Similarly, the projection image , projected image The corresponding brightness values ​​of the 128 first regions can also be obtained.

[0048] S302, obtaining a standard image corresponding to the same light source position, and calculating the brightness of each first area of ​​the standard image according to the step of S301.

[0049] That is, we get the standard image mentioned above. , standard image , standard image Among them, the standard image With projected image Corresponding, standard image With projected image Corresponding, standard image With projected image correspond.

[0050] For each standard image, the corresponding 128 brightness values ​​of the first area can also be obtained. For example, the brightness values ​​of the first area are recorded as to .

[0051] S303: Subtract the brightness of the first area corresponding to the projection image from the brightness of the first area corresponding to the standard image to obtain the relative brightness of the first area.

[0052]

[0053] In the formula, Represents the light source position The projected image collected at The first area The relative brightness of Represents the light source position The projected image collected at The first area Brightness; Represents the light source position Standard image collected at The first area brightness.

[0054] It is worth mentioning that since the brightness uses the average grayscale of the image, when the above relative brightness is positive, it means that the average grayscale of the projected image is greater than the average grayscale of the standard image, that is, the projected image is brighter than the standard image, which means that the corresponding area is backlit, otherwise it is surface lit.

[0055] With standard image The first area For example, its relative brightness for:

[0056] Through this step, corresponding to the standard image at each light source position, the relative brightness of 128 first areas can be obtained.

[0057] As we know from the above, the backlight has lower brightness and a larger average grayscale value relative to the plane, while the surface light has higher brightness and a smaller average grayscale value relative to the plane.

[0058] Therefore, the method of dividing the first area into a backlight area, a surface light area and a plane area according to the relative brightness in this embodiment is as follows: A first threshold Th1 less than zero and a second threshold Th2 greater than zero are set. Preferably, the first threshold Th1 is -10, and the second threshold Th2 is 10.

[0059] If the relative brightness is less than the first threshold Th1, the corresponding first area is the surface light area; If the relative brightness is greater than a second threshold value Th2, the corresponding first area is a backlight area; If the relative brightness is between the first threshold and the second threshold, the corresponding first area is a plane area.

[0060] It is worth noting that in the calculation process of the above relative brightness, the average value of the grayscale value of the first area is used. If there is only a small part of backlight or surface light in the first area, it is easy to be judged as a plane area in the classification process. The larger the absolute value of the first threshold Th1 and the second threshold Th2, the easier it is to distinguish the first area with only a small part of backlight or surface light as a plane area; conversely, it is easy to distinguish the first area with only a small part of backlight or surface light as a backlight area or a surface light area as a whole.

[0061] like Figure 6 As shown, assuming that the light beam is projected from the left, the dotted box represents the actual concave part, the shaded area within the dotted line represents the backlight, and the blank area within the dotted line represents the surface light. On the contrary, if the dotted box represents the actual convex part, the shaded area within the dotted line represents the surface light, and the blank area within the dotted line represents the backlight.

[0062] Through the above calculation, the first area where the red box is located , , , It is judged as the backlight area, and the first area of ​​the blue frame , , It is judged as the surface light area, and the first area is the plane area.

[0063] S4, merging the adjacent backlight area and surface light area into a suspected defect area.

[0064] Regardless of whether it is a recessed portion or a raised portion, there will be adjacent backlight areas and surface light areas at the same time, so a suspected defect area (recessed portion or raised portion) can be obtained by merging the adjacent backlight areas and surface light areas.

[0065] Generally speaking, the backlight area and the front light area are adjacent to each other, but if Figure 6 As shown, located in the first area , The first area between , and in the first area , The first area between It is obviously also part of the concave portion or the convex portion, but because it is located at the intersection of the backlight and the surface light, and the areas of the backlight and the surface light are roughly equal, it is mistakenly judged as a plane area in step S3.

[0066] Therefore, when the adjacent backlight areas and surface light areas are merged into a suspected defect area, if there is a plane area between the adjacent backlight areas (red frame) and surface light areas (blue frame), the plane area between the adjacent backlight areas and surface light areas is merged into the suspected defect area.

[0067] Specifically, the plane area between the closest backlight area and the front light area is merged into the suspected defect area, and the following is obtained: Figure 7 As shown, the suspected defect area is indicated by the green box.

[0068] However, the shape of the suspected defect area in the green box is quite different from the actual recessed / raised portion shown in the dotted box. The reason is that the small part of the first area where the edge of the suspected defect area (green box) is located, which should belong to the backlight area or the surface light area, is mistakenly judged as the plane area, or the small part that should belong to the plane area is mistakenly judged as the backlight area or the surface light area.

[0069] Therefore, at this point, the first area located at the edge of the suspected defect area is further refined, specifically including at least one of the following two methods.

[0070] Method 1: S411, further dividing the first area where the backlight area / front light area located at the edge of the suspected defect area is located into second areas; The first area determined to be the backlight area For example, Figure 8 As shown, it is divided into 3×3=9 second areas, which are respectively to .

[0071] S412, and divide the second area into a backlight area, a surface light area and a plane area according to the relative brightness; please refer to the same distinction method in step S3 for details.

[0072] Through this step, the second area , , , , The second area is divided into a backlight area, and the remaining second area is a plane area.

[0073] S413, removing the second area divided into the plane area in step S412 from the original suspected defect area.

[0074] Method 2: S421, further dividing the first region where the plane region located at the edge of the suspected defect region is located into a third region; The first area is determined to be a plane area. For example, Fig. 9As shown, it is divided into 3×3=9 second areas, which are respectively to .

[0075] S422, and dividing the third area into a backlight area, a surface light area and a plane area according to the relative brightness.

[0076] Through this step, the second area , , The first area is divided into a backlight area, and the remaining second areas are plane areas. After further segmentation of other first areas, new surface light areas will also be generated.

[0077] S423, adding the second area divided into the backlight area and the surface light area in step S422 to the original suspected defect area.

[0078] After the above methods 1 and 2 are processed together, we get Fig.10 The further refined suspected defect area shown in the green box is obviously closer to the actual elliptical defect area.

[0079] S5: For each suspected defect area, calculate the corresponding positions of all light sources The overall area or relative brightness of the suspected defect area The sum of the absolute values ​​of ; That is, according to the position of the light source For each suspected defect area, a corresponding number of defect values ​​will be obtained .

[0080] Take the defect value of these quantities The maximum value of If the maximum defect value is greater than the preset corresponding threshold, the suspected defect area is determined to be a confirmed defect area.

[0081] It is worth noting that the overall area is used as the defect value When , the corresponding threshold is ; in relative brightness The sum of the absolute values ​​of When , the corresponding threshold is .

[0082] In other embodiments, in order to better reflect the defect state, another algorithm is used to calculate the defect value, that is, the sum of the products of the area of ​​each first region / second region of the suspected defect area and the absolute value of the relative brightness corresponding to all light source positions is calculated as the defect value. ,Right now:

[0083] In the formula, Represents the light source position The projected image collected at The area of ​​the first region or the second region; Represents the light source position The projected image collected at The relative brightness of the first area or the second area, the subscript pm refers to the number of the first area or the second area; Represents suspected defect areas.

[0084] The relative brightness of the suspected defect area can be regarded as the depth of the concave part or the height of the convex part.

[0085] When the area is used as the defect value, large-area depressions / protrusions can be screened out, but their depth / height information cannot be obtained; similarly, when the sum of the absolute values ​​of relative brightness is used as the defect value, the area information is ignored.

[0086] In actual measurement, it is often necessary to pay attention to both area and depth / height information. Therefore, the sum of the products of the area of ​​each first region / second region of the suspected defect area and the absolute value of the relative brightness is used as the defect value, which can better represent the characteristics of the suspected defect area. At the same time, the corresponding threshold is also different from the values ​​of the other two cases.

[0087] The reason why this method makes the final judgment on the maximum defect value at all light source positions for the same suspected defect area is that for the same recessed portion or raised portion, the brightness changes produced locally in each first area or second area are different when illuminated by light beams in different directions.

[0088] To put it more intuitively, taking a narrow and long concave portion as an example, when the light beam is irradiated along its length direction, the depth changes more gently due to the direction in which the light beam extends; while when the light beam is irradiated along a direction perpendicular to its length, the depth changes more sharply. Therefore, when calculating the relative brightness of the first area or the second area in step S3, it is obvious that it is easier to detect the suspected defect area when the light beam is irradiated along a direction perpendicular to its length.

[0089] For the office desk 1, the shape of the suspected defect area is unknown before detection, so this method sets at least three different light source positions, which can basically cover the appropriate angles. Of course, in order to further improve the detection accuracy, the number of light source positions can be further increased, but the amount of calculation will also increase accordingly.

[0090] It is worth mentioning that in S5, the confirmed defect area is further divided into a concave portion and a convex portion, and the distinction method is as follows: Determine the arrangement order of adjacent backlight areas and surface light areas along the projection light beam direction corresponding to the confirmed defect area. If the surface light area is located in front of the backlight area, the confirmed defect area is divided into a recessed portion; if the backlight area is located in front of the surface light area, the confirmed defect area is divided into a raised portion.

[0091] Furthermore, after step S5, step S6 is also included, in which the pattern of the confirmed defective area is projected onto the corresponding position of the office desk board 1 to be inspected. For details, please refer to Figure 2 A projector 7 may be provided above the desk panel 1 to project the pattern for confirming the defective area.

[0092] Embodiment 2: In a second aspect, the present invention provides a non-transitory storage medium, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the steps of a method for measuring flatness defects of an office desk panel as described in Example 1.

[0093] Embodiment three: In a third aspect, the present invention provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of a method for measuring flatness defects of an office desk panel as described in Example 1 are implemented.

[0094] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other. The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for measuring flatness defects of office desk panels capable of projecting defect area patterns, characterized in that: The steps include: S1, sequentially projecting light beams onto the desk board from at least three light source positions at fixed heights around the desk board, and collecting projection images of the surface of the desk board respectively; S2, dividing the projection image into a plurality of first regions; S3, measuring the relative brightness of each first area of ​​the projection image at each light source position, and dividing the first area into a backlight area, a surface light area and a plane area according to the relative brightness; S4, merging the adjacent backlight area and surface light area into a suspected defect area; S5, for each suspected defect area, calculating the sum of the absolute values ​​of the area or relative brightness of the suspected defect area at all light source positions as its defect value, and if the maximum defect value is greater than the preset corresponding threshold, determining the suspected defect area as a confirmed defect area; S6, projecting the determined pattern of the confirmed defective area onto the corresponding position of the office desk to be inspected.

2. A method for measuring flatness defects of an office desk panel capable of projecting defect area patterns according to claim 1, characterized in that: In S3, the relative brightness is measured as follows: S301, converting the image of the projection image in each first region into a grayscale image, traversing all pixels of the grayscale image, and calculating an average value of the grayscale values ​​as the brightness of each first region of the projection image; S302, obtaining a standard image corresponding to the same light source position, and calculating the brightness of each first area of ​​the standard image according to the step of S301; S303: Subtract the brightness of the first area corresponding to the projection image from the brightness of the first area corresponding to the standard image to obtain the relative brightness of the first area.

3. A method for measuring flatness defects of an office desk panel capable of projecting defect area patterns according to claim 2, characterized in that: The at least three light sources are located at the same height and are distributed in a circular array, with the center of the circular array located directly above the center of the desk panel.

4. The method for measuring flatness defects of a desk panel capable of projecting defect area patterns according to claim 2, characterized in that: In S3, the method of dividing the first area into a backlight area, a surface light area and a plane area according to the relative brightness is as follows: Setting a first threshold value less than zero and a second threshold value greater than zero; If the relative brightness is less than a first threshold, the corresponding first area is a surface light area; If the relative brightness is greater than a second threshold, the corresponding first area is a backlight area; If the relative brightness is between the first threshold and the second threshold, the corresponding first area is a plane area.

5. The method for measuring flatness defects of a desk panel capable of projecting defect area patterns according to claim 1, characterized in that: In said S3, the following steps are also included: S411, further dividing the first area where the backlight area / front light area located at the edge of the suspected defect area is located into second areas; S412, dividing the second area into a backlight area, a surface light area and a plane area according to the relative brightness; S413, removing the second area divided into the plane area from the original suspected defect area.

6. A method for measuring flatness defects of an office desk panel capable of projecting defect area patterns according to claim 1 or 5, characterized in that: The S3 further includes the following steps: S421, further dividing the first region where the plane region located at the edge of the suspected defect region is located into a third region; S422, dividing the third area into a backlight area, a surface light area and a plane area according to the relative brightness; S423, adding the second area divided into the backlight area and the surface light area to the original suspected defect area.

7. The method for measuring flatness defects of a desk board capable of projecting defect area patterns according to claim 1, characterized in that: When the adjacent backlight areas and surface light areas are merged into the suspected defect area, if there is a plane area between the adjacent backlight areas and surface light areas, the plane area between the adjacent backlight areas and surface light areas is merged into the suspected defect area.

8. The method for measuring flatness defects of a desk panel capable of projecting defect area patterns according to claim 1, characterized in that: In S5, the confirmed defect area is further divided into a concave portion and a convex portion, and the distinguishing method is as follows: Determine the arrangement order of adjacent backlight areas and surface light areas along the projection light beam direction corresponding to the confirmed defect area. If the surface light area is located in front of the backlight area, the confirmed defect area is divided into a recessed portion; if the backlight area is located in front of the surface light area, the confirmed defect area is divided into a raised portion.

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