Method for inspecting projection device by means of inspection device and inspection device for inspecting projection device
By overlaying reference lines on a projection device and combining them with image analysis, the problem of low calibration and inspection efficiency of line lasers and cross-line lasers is solved, enabling fast and accurate calibration and inspection, suitable for devices such as smartphones, tablets, and AR glasses.
Patent Information
- Application Number
- CN202511173329.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-08-21
- Filing Date
- 2025-08-21
- Publication Date
- 2026-03-03
Smart Images
Figure CN121596576A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of projection equipment, such as line lasers and cross lasers, and to a method for inspecting projection equipment and a corresponding inspection device. Background Technology
[0002] Line lasers and cross-line lasers are widely used tools, for example, in architecture and interior design for precise measurements and alignment.
[0003] Line lasers that project an optical marker line are primarily used for leveling, aligning, and mounting components. Crosshair lasers are a special subclass of line lasers that simultaneously project a horizontal and a vertical optical marker line, forming a cross. These instruments are particularly advantageous for accurately representing and verifying right angles. Especially in the construction industry, line lasers and crosshair lasers facilitate precise leveling and alignment, and are important in areas such as interior finishing, dry construction, and ceiling structure installation. They improve efficiency and accuracy by replacing manual methods (such as using levels or string lines for alignment).
[0004] However, a known drawback of line lasers and crosshair lasers is that human users need to expend considerable effort to quickly and reliably verify the accuracy of the current calibration of these instruments. Especially during or between typical operating periods, sufficiently precise calibration checks are often not possible. Yet, properly functioning calibration is essential for the successful use of line lasers and crosshair lasers. Summary of the Invention
[0005] According to the present invention, a method for inspecting projection equipment and a corresponding inspection device are provided.
[0006] According to a first aspect of the invention, a method for inspecting a projection device using an inspection apparatus is provided. The projection device in the sense of the invention is a device that guides (projects) light from a light source onto an object (e.g., a planar surface such as a wall) through optical devices. Preferably, the projection device is a laser-based projection device, i.e., it includes one or more lasers (e.g., one or more laser diodes) as a light source. The projection device may in particular be a line laser or a crosshair laser, or include line lasers or crosshair lasers.
[0007] A line laser is a device that projects lines using laser light, which are typically oriented horizontally or vertically relative to the direction of gravity. Within the scope of this invention, such lines are referred to as optical marking lines or simply marking lines. A line laser comprises one or more lasers and a beam-forming optics configured to produce one or more marking lines on a surface. For this purpose, the optics typically have one or more cylindrical lenses and / or Powell lenses. The optics may also have diffractive optical elements for producing multiple lines. A crosshair laser is a type of line laser that projects two or more marking lines that intersect, for example, at a 90° angle, wherein typically one or more marking lines are oriented horizontally relative to the direction of gravity, and one or more other marking lines are oriented vertically relative to the direction of gravity. Furthermore, a crosshair laser can also be designed to project a vertical point. Line lasers and crosshair lasers can be designed as leveling instruments.
[0008] A method for inspecting a projection device includes the following steps: First, one or more optical marker lines are projected onto a substantially flat surface (e.g., a wall or floor surface) using the projection device. For this purpose, one or more light sources, typically part of the projection device, can be used. Such light sources can be, for example, laser sources. Then, an image of the surface is captured by a camera on the inspection device, for example as a single photograph, part of an image sequence, or video (e.g., in a live view), and preferably also of the projection device. Subsequently, the surface image is displayed on a screen of the inspection device, and one or more reference lines are displayed (i.e., overlaid) in the displayed image. These one or more reference lines correspond to the desired orientation of one of the one or more optical marker lines. Optionally, image processing can be performed on the image as part of or before this display step (i.e., during or after image capture). For example, image quality can be improved by denoising and / or removing image artifacts. Adjusting the viewing angle of the image is also considered; that is, the image can be transformed to appear as if it were taken from a different location.
[0009] The ideal orientation of optical marker lines can be visualized by inspecting the reference lines displayed on the device, and can be oriented, for example, based on internal sensors (e.g., parallel or perpendicular to the direction of gravity), thus facilitating the inspection of the projection device's calibration. In particular, deviations requiring recalibration of the projection device can be identified. The inspection device typically includes a computing unit for signal analysis processing, image processing, and / or image analysis processing, and may be, in particular, a smartphone, tablet, and / or AR glasses, or include such devices.
[0010] Preferably, the method further includes determining the orientation of the surface by inspection equipment (e.g., image analysis processing based on captured images and / or other images) and / or the orientation of inspection equipment (e.g., based on internal sensors of inspection equipment and / or image analysis processing based on captured images and / or other images), and calculating the desired orientation of the one or more optical marker lines by inspection equipment based on the determined surface orientation and / or the determined inspection equipment orientation. To identify any undesirable parallel offsets that may exist in the optical marker lines of the projection equipment, the position of the projection equipment and preferably its pose can also be detected by inspection equipment, for example, through user input of the projection equipment and / or by capturing images of the inspection equipment (e.g., as part of a single photograph, image sequence, or video) and subsequent image analysis processing. Thus, for example, knowing the location of the area (exit port) from which the light used for projection exits from the projection equipment, it can be determined at what ideal location (e.g., at what height) the optical marker lines of the projection equipment would be projected onto the surface. The area where the light used for projection exits the equipment is typically different from the location of the corresponding light source.
[0011] Advantageously, in another step of the method, one of the one or more optical marker lines is detected, and the deviation d between at least one of the one or more optical marker lines and the desired orientation of the corresponding optical marker line is determined. a Such deviations can be related to distance and / or angle. It is advisable to display the determined deviation d on the screen of the inspection equipment. a It is usually expressed as one or more numerical values. It displays one or more deviations d. a This can be done, for example, as angle or length information and / or by means of a traffic light icon (depicting a traffic light, for example, with red, yellow, and green signal colors), which indicates the deviation d. a Conduct a qualitative assessment. Optionally, the deviation d may also be considered. a When the value is particularly large (i.e., exceeding a predefined limit), the software of the inspection device prompts the user to calibrate the projection device, or the inspection device performs or initializes an automated or semi-automatic calibration of the projection device, for example, based on the calculated deviation d. a .
[0012] Preferably, the desired orientation of one (preferably each) of the one or more optical marking lines is parallel to at least one edge (e.g., a ridge) of the surface and / or parallel to or perpendicular to the direction of gravity.
[0013] In particular, the method may also include detecting the distance d between the surface and the projection device. wThe detection can be performed by the inspection device itself and / or by input from a human user of the inspection device (hereinafter referred to as the user). This distance always relates to a defined point (reference point) of the projection device, such as the center of the area where the light used for projection leaves the projection device or another significant point on the projection device's casing. Here, the distance from the reference point to the surface is given by the distance between the reference point and the base of the vertical line drawn from the reference point to the surface. Detection by the inspection device can be performed, for example, using a Lidar sensor (Light detection and ranging) and / or visual odometry and / or image analysis processing, combined with micro-motion analysis where necessary. Specifically, the distance d... w The detection may include detecting walls and / or floors and / or ceilings through image analysis processing of images taken by a camera of the inspection device, wherein the surface is the surface of the wall and / or floor and / or ceiling, and preferably the captured image of the wall and / or floor and / or ceiling is the same as the image of that surface. Particularly advantageous is a distance d w The detection includes probing the projection device through image analysis processing of an image captured by a camera on the inspection device, preferably an image of the projection device that is identical to the surface image. In the case of optical marker lines being detected, determining the deviation d may also be considered. a The distance d between the surface and the projection device is used. w Determine the deviation d a This usually requires other information, such as the height of the projection device (e.g., based on distance d). w (Similar points) and / or knowledge about the structure and construction of the projection equipment. Determine the deviation d. a This can be done, for example, through geometric considerations (e.g., using triangulation) and / or through image analysis processing. Especially in the case of deviation d... a In cases involving only angular deviation and / or intentionally ignoring displacement and considering only angle, distance d can also be avoided. w The deviation is determined solely based on image analysis and subsequent observation of the geometric orientation of the optical marker line relative to the desired orientation. This can be done, for example, when the camera is positioned at the height of the observed optical marker line and preferably at its optical center.
[0014] According to a second aspect of the invention, an inspection apparatus for inspecting a projection device is provided, preferably according to the method described above, wherein the inspection apparatus includes a camera and a screen. Preferably, the inspection apparatus further includes a computing unit for signal analysis processing, image processing, and / or image analysis processing. The inspection apparatus is preferably or includes a smartphone, tablet computer, and / or AR glasses. It is configured to capture an image of a substantially flat surface by means of a camera and display the image on the screen of the inspection apparatus, wherein the inspection apparatus is further configured to display one or more reference lines in the displayed image for one or more optical marking lines projected onto the surface by the projection device, wherein the one or more reference lines respectively correspond to the desired orientation of one of the one or more optical marking lines.
[0015] Particularly advantageously, the inspection device is also configured to detect the one or more optical marker lines in the image and compare their orientation with a corresponding desired orientation. It is conceivable that the inspection device is configured to display the desired orientation of the optical marker lines on the screen of the inspection device.
[0016] Preferably, the inspection device has one or more sensors for determining the orientation of the inspection device, such as one or more accelerometers and / or gyroscopes. In particular, the inspection device may also include a data transmission unit configured to communicate with the projection device wirelessly and / or via a wired connection. For example, this communication path can be used to calibrate the projection device and / or initialize the calibration of the projection device and / or transmit data required for calibration to the projection device.
[0017] Advantages of the present invention
[0018] This invention relates to checking the calibration of single-line lasers, cross-line lasers, and similar high-precision projection devices. The invention employs a method based on an external inspection device that provides the user with simple and rapid feedback on the calibration quality of the projection device by adding superimposed information to an image of the optical marker lines generated by the projection device.
[0019] Specifically, an image of a surface is captured by the inspection device according to the invention, including marker lines projected onto the surface (preferably as a live view), and displayed to the user. During this process, reference lines are superimposed onto the image, thereby providing the user with a simple explanation of the observed quality of the projection device's current calibration.
[0020] Optional embodiments of the present invention disclose supplements based on this basic idea, such as obtaining additional information about the deviation between the observed and desired directions of the optical marker lines. This additional information can be obtained using sensors of the inspection device and image analysis processing methods. Smartphones, tablets, and AR glasses are particularly suitable as the hardware foundation for the inspection device according to the present invention because they typically possess suitable sensors and powerful processors. In particular, the widespread availability of smartphones and tablets provides a low-cost possibility for implementing the present invention. Automated or semi-automated calibration of projection devices such as line lasers and crosshair lasers can also be considered, depending on the technical configuration of the respective device.
[0021] In summary, the present invention enables rapid, accurate, and cost-effective inspection of the calibration of projection devices, such as line lasers and cross lasers. Attached Figure Description
[0022] The embodiments of the present invention will be described in detail with reference to the accompanying drawings and the following description.
[0023] The attached diagram shows:
[0024] Figure 1A A schematic view showing the use of an exemplary inspection device according to the present invention to inspect a projection device;
[0025] Figure 1B A schematic view showing the use of an exemplary inspection device according to the invention to inspect other projection devices;
[0026] Figure 1C A schematic view of the screen of an exemplary inspection device according to the present invention is shown; and
[0027] Figure 2 A flowchart illustrating an exemplary method for inspecting a projection device according to the present invention is shown. Detailed Implementation
[0028] In the following description of embodiments of the present invention, the same or similar elements are denoted by the same reference numerals, and repeated descriptions of these elements are omitted in some cases. The accompanying drawings are only schematic representations of the subject matter of the invention.
[0029] Figure 1A The following is an illustrative illustration of the use of an exemplary inspection device 100 according to the invention to inspect a projection device 110 within the scope of the method according to the invention.
[0030] Here, the projection device 110 shown is a line laser, which projects an optical marking line 130a onto a substantially flat surface 150 of the wall using a laser source and suitable optics. The emitted light from the line laser illuminates the spatial region 120a and produces the optical marking line 130a on the surface 150.
[0031] Inspection device 100 (e.g., a smartphone or tablet) captures an image 150' of surface 150 using camera 101, for example, in the form of video or still image. Preferably, the projection device 110 is also captured by this or other images. Here, inspection device 100 can preferably detect the projection device 110 and / or surface 150 through image analysis processing. Figure 1A In the diagram, the pose 110' (i.e., its position and orientation) of the projection device 110 detected by the inspection equipment is symbolically represented by dashed lines. Thus, given the structure of the projection device 110, its orientation, especially the height at which the laser light exits the projection device 110, can be at least partially inferred. Furthermore, in Figure 1A In the image 150, the area of surface 150 detected by inspection device 100 is marked with a cross 152 defining the area. The captured image 150' of surface 150 is displayed on screen 102 of inspection device 100, wherein the optical marker line 130a projected onto the surface is visible in the image 150' of surface 150. Figure 1A (Line 130a' in the image). A corresponding reference line 160a' is superimposed on the image 150', which corresponds to the desired orientation 160a of the optical marker line 130a.
[0032] Therefore, the reference line 160a' displayed on the screen 102 of the inspection device 100 visualizes the ideal orientation of the optical marker line 130a. This orientation can be calculated based on the internal orientation sensor of the inspection device 100 and by determining the height of the laser from the projection device 110 (e.g., through image analysis processing). Figure 1A In the example shown, the desired orientation 160a is horizontal, i.e., it is perpendicular to the direction of gravity 142, and thus parallel to the corresponding coordinate system 140 (see [reference]). Figure 1C The x-axis 140a is defined by a coordinate system oriented based on the direction of gravity 142. The desired orientation 160a is typically calculated only for a finite length (e.g., corresponding to the extension of surface 150) and evaluated only within this finite length range compared to the actual orientation of the optical marking line 130a. This is in... Figure 1A The corresponding bracket-shaped boundary of line 160a is symbolically represented in the middle.
[0033] exist Figure 1AIn the example shown, the desired horizontal orientation 160a deviates from the optical marking line 130a, meaning it is offset parallel to the line rather than rotated. Therefore, the deviation d a This is equivalent to in Figure 1A The distance is indicated by line 190a. The distance d between surface 150 and projection device 110 is measured. w (exist Figure 1A The line is drawn as 180a), where the distance is d. w Given a defined point (reference point) of the projection device 110, and knowing the height of the projection device 110 (e.g., based on the same reference point) and the position of the laser beam emitted relative to the projection device 110, the deviation d can be calculated. a (That is, the distance between lines 130a and 160a), and is provided to the user in numerical form on the screen 102 of the inspection device 100 (in addition to graphically displaying the desired direction as reference line 160a'). Distance d w The detection can be performed, for example, through corresponding user input. However, it is preferably determined by means of a lidar sensor and / or visual odometry and / or image analysis processing.
[0034] Figure 1B A similar situation is illustrated. Again, schematically, an exemplary inspection device 100 according to the invention is used to inspect the projection device 110 within the scope of the method according to the invention. (And...) Figure 1A The difference lies in the fact that the desired orientation 160b of the optical marker line 130b is parallel to the direction of gravity 142, while... Figure 1B The example deviation d shown a The trajectory 160b is rotated relative to the desired orientation, but not offset. Correspondingly, the laser light emitted by the projection device 110 also illuminates another spatial region 120b. It should also be noted that... Figure 1A and Figure 1B The laser beam from the projection device 110 is emitted from different areas of the device. (The last sentence appears to be incomplete and possibly contains errors.) Figure 1A Equivalently, the corresponding reference line 160b' is displayed on the screen 102 of the inspection device 100, visualizing the expected direction of 160b.
[0035] exist Figure 1B In this case, the deviation d between the desired orientation 160b and the optical marking line 130b a It can be given by angle or distance, where the distance must be relative to a specific height. Figure 1B Mean deviation d a Displayed as line 190b, it represents the distance between the optically marked line 130b at a lower edge height of 150 on the surface and its desired orientation 160b. This deviation d aIt can be calculated and displayed to the user of the inspection device 100 in the form of one or more numerical values. In this example, it can also be as follows: Figure 1A The distance d between the projection device 110 and the surface 150 is determined. w (exist Figure 1B (This is illustrated by the corresponding line 180b). Note here that the distance d drawn here... w (Length of line 180b) and Figure 1A distance d w (The length of line 180a) is different. Figure 1A , 1B The lengths of the center lines 180a and 180b are merely exemplary choices. The different lengths of lines 180a and 180b indicate that even if the projection device 110 is positioned the same, when the distance d... w When each involves a different reference point of the projection device 110, the distance d w It may also be different, especially when Figure 1A and Figure 1B The projection device 110 may behave differently depending on its structural type. In summary, assuming the projection device 110 is positioned the same, the distance d shown will be... w The deviation can vary depending on the definition, and is particularly determined by the structural type of the projection device 110. Figure 1A and Figure 1B The different exit points of the laser light suggest the possibility of different structural types, where the distance d w For example, the center of the corresponding exit port can be used as a reference point.
[0036] Figure 1B The deviation d shown a The line 160b is not offset, only rotated, relative to the desired orientation. Therefore, it can be determined as an angle value through image analysis processing, and then converted into a distance value if necessary based on the length of line 190b. Such a conversion typically requires known comparison values, such as the length of optical marker line 130b or the height of surface 150. Alternatively, the angle and / or distance values can also be determined by other methods (e.g., performing triangulation), for which a known distance d can be used. w .
[0037] at last, Figure 1C The screen 102 of the inspection device 100 according to the invention is shown in schematic view form, and an exemplary possibility of capturing information within the scope of the inspection projection device 110 according to the method of the invention is illustrated. In this example, the foregoing is incorporated. Figure 1A and 1BTwo implementation methods are shown in the example. Therefore, the crosshair laser, acting as the projection device 110, projects two substantially perpendicular intersecting optical marker lines 130a and 130b onto a substantially flat surface 150. The screen 102 displays an image 150' (schematically represented by shaded lines) of the surface 150 taken by the inspection device 100, including images 130a' and 130b' of the optical marker lines 130a and 130b projected onto the surface 150, and a symbolic representation of the projection device 110 reflecting the detected pose 110' of the projection device 110. The desired orientations 160a and 160b of the optical marker lines 130a and 130b are... Figure 1A and 1B The same as in the example, and used as reference lines 160a' and 160b', are overlaid on the displayed image 150'.
[0038] exist Figure 1C In the example, the captured image 150' and the corresponding reference lines 160a', 160b' are displayed essentially from the perspective of the projection device 110, i.e., perpendicularly to surface 150 (front view). Therefore, Figure 1C The plane spanned by the coordinate system 140, plotted with x-axis 140a and y-axis 140b, is parallel to surface 150. Furthermore, the y-axis 140b is oriented opposite to the direction of gravity 142. If the inspection equipment... Figure 1A and 1B If image 150' is taken from a different perspective (e.g., a side view of the scene), then appropriate transformation of the captured image 150' can be considered during image processing to achieve the desired effect. Figure 1C The image shows a front view of surface 150. Furthermore, overlaid on image 150' is also a view based on... Figure 1A and 1B Explain the deviation d of the calculated distance values in the form of 192a and 192b. a And the detected distance d between the projection device 110 and the surface 150, which is another distance value 182. w ,in Figure 1C The values 182, 192a, and 192b shown should be understood as purely exemplary, as are their precise reproduction and positioning on screen 102. The distance value 182 may, for example, correspond to... Figure 1A and 1B The distance d detected in the implementation method w The average value. In this embodiment example, a traffic light icon 106 depicting a traffic light with three lights is used to allow the user to quickly detect the deviation d. a The size and calibration quality of the projection device 110. In the case shown, the calibration is evaluated as being in the medium quality range, and accordingly the traffic light icon 106 shows that the middle light 107 (yellow light) is activated.
[0039] Figure 2 An exemplary method 200 of the present invention is illustrated in flowchart form for inspecting a projection device 110 using an inspection device 100, such as a smartphone or tablet. Here, one or more optical marker lines 130a, 130b are first projected 210 onto a substantially flat surface 150 (such as a wall or floor) using the projection device 110. One or more laser sources of the projection device 110 are typically used for this projection 210. After an image 150' of the surface 150 is captured 220 by a camera 101 of the inspection device 100, the image 150' of the surface 150 is displayed 240 on a screen 102 of the inspection device 100.
[0040] Multiple additional steps 260 can be performed before, simultaneously with, or after the display 240. Figure 2 (marked with a dashed box in the image) to acquire more information based on image analysis and / or other data of the captured image 150'. Therefore, method 200 may, for example, include detecting the distance d between surface 150 and projection device 110 via inspection device 100 and / or via user input from inspection device 100. w This distance d is measured by inspection device 100. w The detection 230 may include detecting walls and / or floors and / or ceilings through image analysis processing, wherein surface 150 may be a surface of a wall and / or floor and / or ceiling. Furthermore, the inspection device 100 detects distance d at 230. w It may also include a projection device 110 that detects objects through image analysis and processing.
[0041] Furthermore, the orientation of surface 150 can be determined and / or the orientation of inspection device 100 can be determined by inspection device 100. Based on this, the desired orientation 160a, 160b of the one or more optical marking lines 130a, 130b can then be calculated by inspection device 100 based on the determined orientation of surface 150 and / or the determined orientation of inspection device 100.
[0042] For example, simultaneously, detection 236 can be performed on the one or more optical marker lines 130a, 130b, thereby determining, in step 238, at least one deviation d between the one or more optical marker lines 130a, 130b and the desired orientation 160a, 160b of the corresponding optical marker lines 130a, 130b, using the information obtained in steps 232, 234. a The determination 238 can be made using the distance d detected in step 230. w conduct.
[0043] During the process of displaying the image 150' of surface 150 on screen 102, the information obtained in step 260 can be displayed on screen 102 together with the image 150', i.e., superimposed on the image 150'. Therefore, after or simultaneously with step 240, it is possible to display 250 of this information and / or one or more reference lines 160a', 160b' in the displayed image 150', wherein the reference lines 160a', 160b' correspond to the desired orientation 160a, 160b of one or more optical marker lines 130a, 130b calculated, respectively.
[0044] This invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, various modifications are possible within the scope of the embodiments described, and these modifications are also within the understanding of those skilled in the art.
Claims
1. A method (200) for inspecting a projection device (110) using an inspection device (100), the projection device preferably comprising a line laser or a crosshair laser, the method comprising the following steps: a. Projecting (210) one or more optical marking lines (130a, 130b) onto a substantially flat surface (150) via the projection device (110); b. The camera (101) of the inspection device (100) captures (220) an image (150') of the surface (150); c. Display (240) the image (150') of the surface (150) on the screen (102) of the inspection device (100); as well as d. One or more reference lines (160a', 160b') are shown in the displayed image (150'), wherein the one or more reference lines (160a', 160b') correspond to the desired orientation (160a, 160b) of one of the one or more optical marker lines (130a, 130b).
2. The method (200) according to claim 1 further includes the following step: The orientation of the surface (150) and / or the orientation of the inspection device (100) are determined (232) by the inspection device (100); as well as The inspection device (100) calculates (234) the desired orientation (160a, 160b) of the one or more optical marker lines (130a, 130b) based on the orientation of the determined surface (150) and / or the orientation of the determined inspection device (100).
3. The method (200) according to claim 1 or 2, further comprising the following step: Detect (236) one or more optical marker lines (130a, 130b); as well as Determine the deviation d between at least one of the one or more optical marker lines (130a, 130b) and the desired orientation (160a, 160b) of the corresponding optical marker line (130a, 130b). a .
4. The method (200) according to any one of the preceding claims, wherein, One of the one or more optical marking lines (130a, 130b), preferably each optical marking line, has a desired orientation (160a, 160b) parallel to at least one edge of the surface (150) and / or oriented parallel to or perpendicular to the direction of gravity (142).
5. The method (200) according to any one of the preceding claims, wherein, The method (200) includes: detecting (230) the distance d between the surface (150) and the projection device (110) by means of input from the inspection device (100) and / or by means of input from the user of the inspection device (100). w .
6. The method (200) according to claim 5, wherein, The distance d w The detection (230) includes: detecting the wall and / or floor and / or ceiling by performing image analysis processing on images of the wall and / or floor and / or ceiling captured by a camera (101) of the inspection device (100), wherein the surface (150) is the surface of the wall and / or floor and / or ceiling, and preferably, the captured images of the wall and / or floor and / or ceiling are the same as the image (150') of the surface (150).
7. The method (200) according to claim 5 or 6, wherein the distance d w The detection (230) includes: The projection device (110) is detected by image analysis processing of an image of the projection device (110) captured by a camera (101) of the inspection device (100), wherein preferably, the image of the projection device (110) captured is the same as the image (150') of the surface (150).
8. The method (200) according to any one of claims 3 and 5 to 7, wherein, The distance d between the surface (150) and the projection device (110) w Used to determine the deviation d of (238) a .
9. An inspection device (100) for inspecting a projection device (110), preferably the inspection is performed using the method (200) according to any one of claims 1 to 8. in, The inspection device (100) includes a camera (101) and a screen (102), and the inspection device is configured for, The camera (101) captures an image (150') of a substantially flat surface (150) and displays the image (150') on the screen (102) of the inspection device (100). The inspection device (100) is further configured to display one or more reference lines (160a', 160b') in the displayed image (150') for one or more optical marking lines (130a, 130b) projected onto the surface (150) by the projection device (110), wherein the one or more reference lines (160a', 160b') correspond to the desired orientation (160a, 160b) of one of the one or more optical marking lines (130a, 130b).
10. The inspection device (100) according to claim 9, wherein, The inspection device (100) is further configured to detect the one or more optical marker lines (130a, 130b) in the image (150') and compare the orientation of the one or more optical marker lines with the corresponding desired orientation (160a, 160b).
11. The inspection device (100) according to claim 9 or 10, wherein, The inspection device (100) has one or more sensors for determining the orientation of the inspection device (100).
12. The inspection device (100) according to any one of claims 9 to 11, wherein, The inspection device (100) includes a data transmission unit configured to communicate with the projection device (110) wirelessly and / or via wired means.