Optical axis calibration method, system, ghost image measurement method and computer device

Abstract

The application relates to an optical axis calibration method, an optical axis calibration system, a ghost image measurement method and a computer device. The method is applied to an optical axis calibration system comprising an image acquisition device adjusted in position by a first adjusting mechanism and an adjusting jig provided with a display module to be measured and adjusted in position by a second adjusting mechanism, and comprises the following steps: controlling the first adjusting mechanism and / or the second adjusting mechanism to perform rotation adjustment, so that a cross calibration image displayed by the display module to be measured is aligned with a picture reference cross of the image acquisition device; controlling the second adjusting mechanism to perform translation adjustment, so that multi-order ghost images formed by a ghost image calibration image displayed by the display module to be measured in a picture of the image acquisition device are regularly distributed; and controlling the first adjusting mechanism to perform rotation adjustment again, so that the cross calibration image displayed by the display module to be measured is aligned with the picture reference cross of the image acquisition device. The method can reduce ghost image interference, optimize optical calibration accuracy and improve ghost image measurement accuracy.

Description

Technical Field

[0001] This application relates to the field of measurement technology, and in particular to an optical axis calibration method, system, ghost image measurement method, and computer equipment. Background Technology

[0002] In the field of near-eye display technology, ghost image measurement is a crucial step in evaluating the imaging quality of display modules. In traditional techniques, to ensure measurement accuracy, the optical axis of the near-eye display module and the image acquisition device is typically calibrated before ghost image measurement. This is done by adjusting the pose of the display module to align the crosshair pattern displayed by the module with the center of the camera image.

[0003] However, due to the complexity of the optical system of the near-eye display module, even after the cross pattern is aligned, the complex distribution characteristics caused by reflection result in disordered ghost images or even overlapping with the main image in subsequent ghost image test patterns, which seriously affects the recognition and intensity analysis of the ghost image area.

[0004] It is evident that existing technologies still suffer from low accuracy and high susceptibility to interference in optical calibration. Summary of the Invention

[0005] Therefore, it is necessary to provide an optical axis calibration method, system, ghost measurement method, and computer equipment that can reduce ghost image interference, optimize optical calibration accuracy, and improve ghost image measurement accuracy in response to the above-mentioned technical problems.

[0006] In a first aspect, this application provides an optical axis calibration method applied to an optical axis calibration system. The optical axis calibration system includes an image acquisition device whose pose is adjusted by a first adjustment mechanism and an adjustment fixture on which a display module under test is mounted, whose pose is adjusted by a second adjustment mechanism. The optical axis calibration method includes:

[0007] Control the first adjustment mechanism and / or the second adjustment mechanism to rotate and adjust so that the crosshair calibration image displayed by the display module under test is aligned with the screen reference crosshair of the image acquisition device;

[0008] The second adjustment mechanism is controlled to perform translation adjustment so that the multi-level ghost images formed by the ghost image calibration image displayed by the display module under test in the screen of the image acquisition device are distributed in a regular manner;

[0009] The first adjustment mechanism is rotated again to align the crosshair calibration image displayed by the display module under test with the screen reference crosshair of the image acquisition device.

[0010] In one embodiment, prior to controlling the first adjustment mechanism and / or the second adjustment mechanism to perform rotational adjustment, the method further includes:

[0011] Based on the standard gauge block, control the first adjustment mechanism and / or the second adjustment mechanism to perform translation adjustment, so as to adjust the distance between the image acquisition device and the display module under test to a preset spacing.

[0012] In one embodiment, controlling the first adjusting mechanism and / or the second adjusting mechanism to perform rotational adjustment includes:

[0013] Control the second adjustment mechanism to rotate and adjust so that the orientation of the cross arm in the displayed cross calibration image coincides with the orientation of the arm of the reference cross in the image;

[0014] The first adjustment mechanism is controlled to rotate and adjust so that the center of the cross intersection in the displayed cross calibration image coincides with the center of the reference cross on the screen.

[0015] In one embodiment, controlling the second adjusting mechanism to perform rotational adjustment includes:

[0016] Acquire the first image to be aligned, captured by the image acquisition device;

[0017] The third-party rotation amount is determined based on the orientation of the cross arms of the cross calibration image in the first image to be aligned.

[0018] The second adjustment mechanism is controlled to perform rotation adjustment based on the third-party rotation amount.

[0019] In one embodiment, controlling the first adjusting mechanism to perform rotational adjustment includes:

[0020] Acquire the second image to be aligned, captured by the image acquisition device;

[0021] Based on the offset of the center of the cross intersection of the cross calibration image in the second image to be aligned, a first direction rotation amount and a second direction rotation amount are determined; the rotation axes of the first direction rotation amount and the second direction rotation amount are perpendicular to each other;

[0022] The first adjustment mechanism is controlled to perform rotational adjustment based on the rotation amount in the first direction and the rotation amount in the second direction.

[0023] In one embodiment, controlling the second adjustment mechanism to perform translation adjustment includes:

[0024] The initial exposure parameters of the image acquisition device are updated according to preset exposure parameters; the preset exposure parameters include preset exposure time and / or preset camera gain.

[0025] Acquire the ghost image obtained by the image acquisition device after the exposure parameters are updated;

[0026] Based on the captured image of the ghost image, a first directional translation amount and a second directional translation amount are determined; the directions of the first directional translation amount and the second directional translation amount are perpendicular to each other;

[0027] Based on the translation amount in the first direction and the translation amount in the second direction, the second adjustment mechanism is controlled to perform translation adjustment.

[0028] In one embodiment, the first adjustment mechanism provides rotational degrees of freedom about a first direction and a second direction, and translational degrees of freedom about a third direction; the second adjustment mechanism provides translational degrees of freedom about the first direction and the second direction, and rotational degrees of freedom about a third direction.

[0029] Wherein, the first direction, the second direction, and the third direction are perpendicular to each other, and the first direction and the second direction are both parallel to the mounting plane of the display module under test.

[0030] Secondly, this application provides an optical axis calibration system, which includes an image acquisition device, an adjustment fixture, a first adjustment mechanism, a second adjustment mechanism, and a control module. The image acquisition device is position-adjusted by the first adjustment mechanism, the adjustment fixture is position-adjusted by the second adjustment mechanism, and the adjustment fixture is used to mount the display module under test.

[0031] The control module is connected to the image acquisition device, the first adjustment mechanism, and the second adjustment mechanism respectively, and is used to perform the optical axis calibration method described above according to the image image of the image acquisition device.

[0032] Thirdly, this application provides a ghost image measurement method applied to an optical axis calibration system. The optical axis calibration system includes an image acquisition device whose pose is adjusted by a first adjustment mechanism and an adjustment fixture on which a display module to be tested is mounted, whose pose is adjusted by a second adjustment mechanism. The ghost image measurement method includes:

[0033] Perform the optical axis calibration method as described above;

[0034] Acquire the calibration image obtained by the image acquisition device after optical axis calibration;

[0035] Based on the calibration acquisition image, ghost image measurement is performed on the display module under test to obtain the ghost image measurement result.

[0036] Fourthly, this application provides a computer device including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the method described above.

[0037] Fifthly, this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described above.

[0038] The aforementioned optical axis calibration method, system, ghost image measurement method, and computer equipment, by controlling the first adjustment mechanism and / or the second adjustment mechanism to perform rotational adjustment, align the crosshair calibration image displayed by the display module under test with the reference crosshair of the image acquisition device, thus achieving initial spatial alignment of the main image with the optical axis of the acquisition system; controlling the second adjustment mechanism to perform translational adjustment, so that the multi-level ghost images formed by the ghost image calibration image displayed by the display module under test in the image acquisition device's screen are regularly distributed, thereby transforming the originally chaotic ghost image distribution into a spatially regular array structure; and again controlling the first adjustment mechanism to perform translational adjustment, so that the multi-level ghost images formed by the ghost image calibration image displayed by the display module under test in the image acquisition device's screen are regularly distributed, thus ... are regularly distributed, thus transforming the originally chaotic ghost image distribution into a spatially regular array structure. The joint mechanism is rotated and adjusted so that the crosshair calibration image displayed by the display module under test is aligned with the crosshair reference of the image acquisition device, thus eliminating the slight tilt error introduced by translation adjustment. The closed-loop process of establishing the main image alignment reference, controlling the ghost image distribution, and recalibrating the main image, through the process of crosshair coarse calibration, ghost image alignment, and crosshair recalibration, transforms the ghost image from uncontrollable interference noise into an engineering-controllable calibration feature, realizing the physical separation of the ghost image from the main image. This can improve the resolvability and measurement consistency of the ghost image area in the image, achieving the technical effects of reducing ghost image interference, optimizing optical calibration accuracy, and improving ghost image measurement accuracy. Attached Figure Description

[0039] Figure 1 This is a diagram illustrating the application environment of the optical axis calibration method in one embodiment;

[0040] Figure 2 This is a flowchart illustrating an optical axis calibration method in one embodiment;

[0041] Figure 3 This is a schematic diagram of the optical axis calibration system in one embodiment;

[0042] Figure 4 This is a flowchart illustrating the optical axis calibration method in another embodiment;

[0043] Figure 5 This is a schematic diagram of a crosshair calibration image in another embodiment;

[0044] Figure 6 This is a schematic diagram of a ghost image calibration image in another embodiment;

[0045] Figure 7 This is a schematic diagram of a multi-level ghost image in one embodiment where the optical axis is not properly aligned.

[0046] Figure 8 This is a schematic diagram of a multi-order ghost image under the condition of good optical axis calibration in one embodiment;

[0047] Figure 9 This is a structural block diagram of an optical axis calibration system in one embodiment;

[0048] Figure 10 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0050] The optical axis calibration method provided in this application embodiment can be applied to, for example... Figure 1 In the application environment shown, the optical axis calibration system includes an image acquisition device 102 whose pose is adjusted by a first adjustment mechanism 101, an adjustment fixture 104 on which a display module 105 under test is mounted and whose pose is adjusted by a second adjustment mechanism 103, and a terminal 106. The terminal 106 is connected to the first adjustment mechanism 101, the image acquisition device 102, and the second adjustment mechanism 103, respectively, and is used to control the first adjustment mechanism and / or the second adjustment mechanism to perform rotational adjustment so that the crosshair calibration image displayed by the display module under test is aligned with the screen reference crosshair of the image acquisition device; to control the second adjustment mechanism to perform translational adjustment so that the multi-level ghost images formed by the ghost image calibration image displayed by the display module under test in the screen of the image acquisition device are regularly distributed; and to control the first adjustment mechanism to perform rotational adjustment again so that the crosshair calibration image displayed by the display module under test is aligned with the screen reference crosshair of the image acquisition device. The terminal 106 can be, but is not limited to, various personal computers, laptops, smartphones, and tablets.

[0051] In one embodiment, such as Figure 2 As shown, an optical axis calibration method is provided, which can be applied to, for example... Figure 1 Taking the optical axis calibration system shown as an example, the optical axis calibration system includes an image acquisition device whose pose is adjusted by a first adjustment mechanism and an adjustment fixture on which the display module under test is mounted, whose pose is adjusted by a second adjustment mechanism. The optical axis calibration method includes:

[0052] Step S110: Control the first adjustment mechanism and / or the second adjustment mechanism to rotate and adjust so that the crosshair calibration image displayed by the display module under test is aligned with the screen reference crosshair of the image acquisition device.

[0053] The image acquisition device can be an optoelectronic imaging device used to capture the imaging results of the display module under test, providing visual feedback to support optical axis alignment and ghost image distribution observation. In this embodiment, the image acquisition device can receive the emitted light from the display module under test through a lens system, and convert it into a digital image signal output via a photoelectric sensor. Exemplarily, the image acquisition device can be one or more of, including but not limited to, CMOS cameras, CCD cameras, and industrial cameras.

[0054] The display module under test can be a near-eye display unit with integrated optical elements. In this embodiment, the display module under test can serve as an imaging source, achieving optical calibration by displaying a crosshair calibration image and a ghost image calibration image. For example, it can include a light source and a multi-layer optical structure, the optical structure of which determines the generation characteristics and distribution pattern of the ghost image. In this embodiment, an image signal of the crosshair calibration image or the ghost image calibration image can be input to the display module under test via a driving circuit to generate a composite image containing the main image and multiple ghost images. For example, the display module under test can employ one or more display methods such as diffractive waveguides, reflective displays, and refractive displays; this embodiment does not limit this.

[0055] The adjustment fixture can be a mechanical platform used to fix the display module under test and, in conjunction with a second adjustment mechanism, to support spatial pose adjustment, thereby achieving fixation of the display module under test and controllable pose adjustment in translational and rotational dimensions. For example, the adjustment fixture can support the display module under test through a rigid connection structure and achieve displacement and attitude changes with the aid of the second adjustment mechanism.

[0056] The first adjustment mechanism can be an execution unit that drives the image acquisition device to adjust its pose, and can be used to achieve fine adjustment of the image acquisition device. In this embodiment, the first adjustment mechanism can be used to adjust the rotation of the optical axis of the image acquisition device. For example, after receiving a control signal, the first adjustment mechanism can drive the gimbal structure to rotate through an electric device such as a stepper motor or a voice coil motor.

[0057] The second adjustment mechanism can be a drive adjustment fixture, that is, an execution unit that drives the display module under test to adjust its position and posture, and can support translation and rotation adjustment of the display module under test in space. For example, after receiving control commands, the second adjustment mechanism can realize translation or rotation in space through electric devices such as stepper motors and voice coil motors.

[0058] The crosshair calibration image can be a reference visual pattern displayed and output by the display module under test for optical axis alignment. It can be used as a primary image reference to determine whether the optical axis coincides with the screen reference crosshair of the image acquisition device.

[0059] The image reference crosshair can be a preset visual coordinate reference in the image frame of the image acquisition device, used to determine whether the crosshair calibration image is centered in the image acquisition device's screen.

[0060] Controlling the rotation of the first and / or second adjustment mechanisms can be achieved through a closed-loop feedback mechanism. This involves comparing the position of the crosshair calibration image in the acquired frame with the deviation of the reference crosshair, driving the adjustment mechanisms to rotate until their centers coincide. Furthermore, based on image edge detection and template matching algorithms, the center coordinates of the crosshair image can be automatically calculated and the gimbal angle adjusted. Visual alignment can then be achieved by fine-tuning the first and / or second adjustment mechanisms, thereby achieving coarse alignment between the main image and the optical axis of the acquisition system, and establishing a calibration benchmark.

[0061] Step S120: Control the second adjustment mechanism to perform translation adjustment so that the multi-level ghost images formed by the ghost image calibration image displayed by the display module under test in the image acquisition device are regularly distributed.

[0062] The ghost image calibration image can be a pattern output by the display module under test to highlight the distribution of ghost images. For example, the ghost image calibration image can be generated by the display driving circuit, using one or more structures such as symmetrical, asymmetrical, dot matrix, and circular rings, producing multi-level ghost images through reflection and diffraction within the module. For example, the ghost image calibration image can employ single-point patterns, multi-point patterns, single-line patterns, multi-line patterns, grid patterns, asymmetrical patterns, etc. Furthermore, iterative alignment can be performed using ghost image calibration images with different patterns.

[0063] Multi-level ghost images can be multiple secondary images that coexist with the main image, generated by reflection or diffraction from the internal optical interfaces of the display module under test, and are different from the main image of the ghost image calibration image. They reflect the optical system under non-ideal conditions and can be used to assess the degree of ghost image interference. For example, multi-level ghost images may originate from multiple reflections or scatterings of incident light by multiple layers, interfaces, diffraction structures, etc. in the module, thereby forming a discrete image array separated along the optical axis.

[0064] Correspondingly, controlling the second adjustment mechanism to perform translational adjustment can be done by translating the adjustment fixture along a direction perpendicular to the optical axis while maintaining rotational stability, observing the displacement response of the ghost images in the image plane until they form a predictable spatial array. In one exemplary embodiment, the ghost image position can be determined by translating in segments along the X-axis and / or Y-axis with fixed step sizes, recording the change in ghost image position at each step, and fitting a linear relationship between displacement and translation amount. In another exemplary embodiment, a preset ghost image distribution model can be used to calculate the required translation amount in reverse, driving the second adjustment mechanism to move to the target position. This can transform the originally chaotic ghost image distribution into a spatially regular array structure, achieving physical separation of the main image and ghost images in the image plane.

[0065] In step S130, the first adjustment mechanism is rotated again to align the crosshair calibration image displayed by the display module under test with the reference crosshair of the image acquisition device.

[0066] It is understandable that, since step S120 drives the second adjustment mechanism to adjust, the originally aligned optical axes become misaligned after adjustment. By re-aligning the crosshairs, a dual match of relative position and axial direction can be achieved.

[0067] Correspondingly, controlling the first adjustment mechanism to perform rotation adjustment again can be done after completing the translation adjustment, by using the same adjustment method as controlling the first adjustment mechanism in step S110, to re-detect the positional offset of the crosshair calibration image relative to the screen reference crosshair, and only by rotating the first adjustment mechanism for fine adjustment to restore alignment.

[0068] Taking the mass production testing of AR glasses modules as an example, the optical axis calibration method in this embodiment can be implemented on the optical performance testing production line of AR glasses modules. The module under test is fixed on an adjustment fixture, and the image acquisition device is located directly in front of it. First, the gimbal is rotated by the first adjustment mechanism to align the crosshair calibration image output by the module with the center of the camera image. Then, the display pattern is switched to a dot matrix ghost image calibration image, and the second adjustment mechanism is controlled to move the adjustment fixture horizontally so that the ghost images form a linear arrangement with equal spacing and decreasing brightness on the image sensor. Finally, the first adjustment mechanism is finely adjusted again to ensure that the crosshair image is still accurately centered, so that the ghost images present a clearly separated array in the image, which is convenient for subsequent software to automatically identify the intensity and position of each level of ghost images and avoid misjudgment caused by ghost image overlap.

[0069] This embodiment provides an optical axis calibration method. By controlling the first adjustment mechanism and / or the second adjustment mechanism to perform rotational adjustment, the crosshair calibration image displayed by the display module under test is aligned with the reference crosshair of the image acquisition device, thus achieving initial spatial alignment of the main image and the optical axis of the acquisition system. The second adjustment mechanism is then controlled to perform translational adjustment, so that the multi-level ghost images formed by the ghost image calibration image displayed by the display module under test in the image acquisition device's screen are distributed in a regular manner, thereby transforming the originally chaotic ghost image distribution into a spatially regular array structure. The first adjustment mechanism is then controlled again to... By rotating the image to align the crosshair calibration image displayed by the display module under test with the crosshair reference image of the image acquisition device, the slight tilt error introduced by translation adjustment can be eliminated. The closed-loop process of establishing the main image alignment reference, controlling the ghost image distribution, and recalibrating the main image, through the process of crosshair coarse calibration, ghost image alignment, and crosshair recalibration, transforms the ghost image from uncontrollable interference noise into an engineering-controllable calibration feature, realizing the physical separation of the ghost image from the main image. This can improve the resolvability and measurement consistency of the ghost image area in the image, achieving the technical effects of reducing ghost image interference, optimizing optical calibration accuracy, and improving ghost image measurement accuracy.

[0070] In one embodiment, prior to controlling the first adjustment mechanism and / or the second adjustment mechanism to perform rotational adjustment, the method further includes:

[0071] Based on the standard gauge block, control the first adjustment mechanism and / or the second adjustment mechanism to perform translation adjustment so as to adjust the distance between the image acquisition device and the display module under test to a preset spacing.

[0072] The standard gauge block can be a reference body such as metal or ceramic with a known precise geometric length, used to set the system working distance between the image acquisition device and the display module under test, or it can be a high-precision distance measuring device used to achieve distance measurement.

[0073] The preset spacing can be a fixed working distance determined through optical simulation or experimental calibration to achieve optimal spatial separation between the main image and the first-order ghost image in the image plane. Alternatively, it can be a usage distance determined based on the application of the display module under test and the actual usage scenario. In an exemplary embodiment, taking a near-eye display module as an example, the preset spacing can be a set distance between the human eye and the near-eye display module. During optical calibration, the preset spacing can be precisely limited using standard gauge blocks.

[0074] Based on the standard gauge block, the first adjustment mechanism and / or the second adjustment mechanism are controlled to perform translational adjustment. This can be achieved by placing the standard gauge block between the front end of the image acquisition device and the rear end of the adjustment fixture, and controlling the first or second adjustment mechanism to perform translational movement until the gauge block is clamped tightly without gaps, thereby locking the system spacing to the nominal length of the gauge block, i.e., the preset spacing.

[0075] Furthermore, a contact displacement sensor can be used to monitor the compression of the gauge block in real time. When the sensor reading stabilizes within the gauge block's tolerance range, the position of the adjustment mechanism is locked. Additionally, optical mirrors can be installed on both sides of the gauge block, and the distance between the two mirrors can be measured using a laser interferometer to dynamically adjust the adjustment mechanism until the measured value equals the preset distance, thereby establishing a precise and reproducible system working distance.

[0076] This embodiment provides an optical axis calibration method that uses a standard gauge block to control the first adjustment mechanism and / or the second adjustment mechanism to perform translational adjustment, thereby adjusting the distance between the image acquisition device and the display module under test to a preset spacing. By locking the system working distance through a physical reference, the spatial separation characteristics generated by Fresnel reflection can be stably excited, avoiding ghost image position drift and overlap with the main image caused by random distance, thus achieving the technical effect of improving the predictability of ghost image spatial distribution and measurement consistency.

[0077] In one embodiment, controlling the first adjusting mechanism and / or the second adjusting mechanism to perform rotational adjustment includes:

[0078] Control the second adjustment mechanism to rotate and adjust so that the orientation of the cross arms in the displayed cross calibration image coincides with the orientation of the arms of the reference cross on the screen;

[0079] The first adjustment mechanism is rotated to make the center of the cross intersection in the displayed cross calibration image coincide with the center of the reference cross on the screen.

[0080] In this context, the orientation of the cross arms in the cross calibration image can be the absolute orientation angle of the two cross arms relative to the image coordinate system. It is understood that the orientation of the cross arms in the cross calibration image is affected by the module's mounting tilt angle and rotation error after the cross pattern output by the display module under test is imaged by the optical system, causing the extension direction of the arms to shift. Therefore, the orientation of the cross arms can be used as an orientation reference for rotation calibration to eliminate relative rotational distortion between the module and the acquisition system. The orientation of the cross arms in the cross calibration image can include one or more of the following: horizontal arm orientation, vertical arm orientation, diagonal arm orientation, etc.

[0081] The orientation of the arms of the image reference crosshair can be the fixed orientation angle of the two arms of the preset reference crosshair in the image coordinate system of the image acquisition device. It can be used to provide an absolute orientation reference, thereby comparing and correcting the rotation deviation of the crosshair calibration image. For example, the orientation of the arms of the image reference crosshair can include, but is not limited to, horizontal reference arms, vertical reference arms, diagonal reference arms, etc.

[0082] Controlling the second adjustment mechanism to perform rotational adjustment can keep the image acquisition device fixed, and drive the adjustment fixture to rotate around the optical axis only through the second adjustment mechanism to adjust the azimuth angle of the display module under test until the cross arm is aligned with the arm direction of the reference cross, thereby eliminating rotational distortion and eliminating the azimuth rotation error caused by module installation or clamping, realizing the azimuth alignment between the main image and the reference system, and providing a stable premise for subsequent center alignment.

[0083] The center of the crosshair intersection in the crosshair calibration image can be the pixel coordinate position of the geometric center point where the two arms of the crosshair intersect in the crosshair calibration image in the image plane. In an exemplary embodiment, the center of the crosshair intersection in the crosshair calibration image can be obtained by identifying the intersection point of the crosshair arms using an image processing algorithm. The center of the image reference crosshair can be the pixel coordinate position of the geometric center of a preset reference crosshair in the image acquisition device's image in the image plane.

[0084] Controlling the first adjustment mechanism to perform rotational adjustment can be achieved by fixing the adjustment fixture after the orientation alignment is completed, and only rotating the image acquisition device through the first adjustment mechanism to fine-tune its optical axis direction, so that the cross intersection is precisely aligned with the center of the image, realizing optical axis coaxiality. Thus, after eliminating orientation error, the precise alignment of the optical axis center can be achieved independently, avoiding the coupling interference between orientation and center errors.

[0085] This embodiment provides an optical axis calibration method that controls a second adjustment mechanism to rotate and adjust so that the orientation of the cross arm coincides with the orientation of the arm of the image reference cross, and controls a first adjustment mechanism to rotate and adjust so that the center of the cross intersection coincides with the center of the image reference cross. By first eliminating the orientation distortion caused by the module installation tilt angle or fixture eccentricity through the second adjustment mechanism, and then independently achieving precise alignment of the optical axis center based on orientation alignment, the coupling interference between rotation and center error is avoided. This decouples the traditional single overall alignment operation. By using two independent operations, orientation alignment and center alignment, the coupling interference between rotational degrees of freedom can be effectively cut off, thereby improving the accuracy of cross calibration.

[0086] In one embodiment, controlling the second adjusting mechanism to perform rotational adjustment includes:

[0087] Acquire the first image to be aligned, captured by the image acquisition device;

[0088] The third-party rotation amount is determined based on the orientation of the cross arms in the first image to be aligned, according to the orientation of the cross arms in the cross calibration image.

[0089] The second adjustment mechanism is controlled to perform rotation adjustment based on the third-party rotation amount.

[0090] The first image to be aligned may be an original digital image frame captured by the image acquisition device before rotation adjustment, containing the crosshair calibration image output by the display module under test, used for alignment with the central crosshair of the camera.

[0091] The third-party rotation amount is determined based on the orientation of the crossarms in the calibration image within the first image to be aligned. This can be achieved by image processing of the first image to be aligned, extracting the geometric orientation of the crossarms, and calculating the angle difference between the crossarms and the image reference coordinate system. This difference is the required rotation compensation angle around the optical axis. Furthermore, determining the third-party rotation amount based on the orientation of the crossarms in the calibration image within the first image to be aligned can be achieved by determining the driving amount for the rotation of the second adjustment mechanism based on the angle difference, causing the adjustment fixture to rotate around the optical axis by that angle to eliminate crossarm orientation deviation.

[0092] In one specific embodiment, the second adjustment mechanism is controlled to perform rotation adjustment based on the third-party rotation amount. This can be achieved by using a closed-loop servo system to convert the rotation amount into motor pulses, driving the stepper motor to rotate precisely at the corresponding angle. Alternatively, a pre-calibrated rotation-displacement mapping table can be used to directly map the angle value into a fixture rotation execution command. This enables closed-loop rotation calibration based on image geometric features, eliminating manual alignment errors and optical nonlinear interference.

[0093] This embodiment provides an optical axis calibration method. By acquiring a first image to be aligned using an image acquisition device, determining a third-direction rotation amount based on the orientation of the cross arms of the cross calibration image within the first image to be aligned, and controlling a second adjustment mechanism to perform rotation adjustment based on the third-direction rotation amount, the method converts subjective visual alignment into objective numerical output based on the first image to be aligned, achieving precise quantification of rotation error. Closed-loop rotation calibration based on image geometric features effectively eliminates errors from manual alignment and optical nonlinear interference, making rotation calibration quantifiable, reproducible, and traceable. This achieves the technical effects of reducing ghost image interference, optimizing optical calibration accuracy, and improving ghost image measurement accuracy.

[0094] In one embodiment, controlling the first adjusting mechanism to perform rotational adjustment includes:

[0095] Acquire the second image to be aligned, captured by the image acquisition device;

[0096] The first direction rotation amount and the second direction rotation amount are determined based on the offset of the center of the cross intersection of the cross calibration image in the second image to be aligned.

[0097] The first adjustment mechanism is controlled to perform rotational adjustment based on the rotation amount in the first direction and the rotation amount in the second direction.

[0098] The second image to be aligned can be an image frame acquired by the image acquisition device after azimuth alignment is completed during the optical axis calibration process, used to accurately calculate the offset of the center of the cross intersection.

[0099] The first direction rotation amount can be the angular error component about the horizontal axis of the image acquisition device, calculated from the offset of the crosshair center in the image plane. It can be used to compensate for the tilt of the image acquisition device in the vertical plane and eliminate asymmetric ghost image diffusion in the vertical direction. The second direction rotation amount can also be the angular error component about the vertical axis of the image acquisition device, calculated from the offset of the crosshair center in the image plane. It can be used to compensate for the tilt of the image acquisition device in the horizontal plane and eliminate asymmetric ghost image diffusion in the horizontal direction. The rotation axes of the first and second direction rotation amounts are perpendicular to each other.

[0100] The first and second rotation amounts are determined by the offset of the center of the crosshair intersection of the crosshair calibration image in the second image to be aligned. This can be achieved by inputting the two-dimensional pixel offset of the center of the crosshair intersection into the camera intrinsic parameter matrix and using inverse perspective projection transformation to calculate the angular error components around the two orthogonal axes. In an exemplary embodiment, the pixel offset can be mapped to the parallax angle of the image plane using calibrated camera intrinsic parameters and distortion coefficients, and then decomposed into pitch and yaw components to obtain the first and second rotation amounts. Alternatively, based on a preset offset rotation lookup table method, the corresponding rotation amounts can be directly output through interpolation. This transforms the visual alignment error into executable three-dimensional spatial rotation parameters and achieves accurate modeling from two-dimensional image offset to three-dimensional optical axis tilt.

[0101] Accordingly, controlling the first adjustment mechanism to perform rotational adjustment based on the first and second direction rotation amounts can be achieved by inputting the calculated two rotational components as control commands into the first adjustment mechanism to drive it to perform rotational adjustment and realize angle compensation.

[0102] This embodiment provides an optical axis calibration method. By acquiring a second image to be aligned from an image acquisition device, and determining a first rotation amount and a second rotation amount based on the offset of the center of the cross intersection of the crosshair calibration image in the second image to be aligned, the first adjustment mechanism is then controlled to perform rotation adjustment based on the first and second rotation amounts. By converting visual alignment errors into executable three-dimensional spatial rotation parameters, closed-loop compensation for the optical axis spatial tilt angle is achieved. This can eliminate the combined tilt of pitch and yaw caused by fixture installation errors or mechanical deformation, enabling the module optical axis and the acquisition device optical axis to achieve true coaxiality in three-dimensional space. This achieves the technical effects of reducing ghost image interference, optimizing optical calibration accuracy, and improving ghost image measurement accuracy.

[0103] In one embodiment, controlling the second adjustment mechanism to perform translation adjustment includes:

[0104] The initial exposure parameters of the image acquisition device are updated according to the preset exposure parameters;

[0105] Acquire ghost images obtained by the image acquisition device after the exposure parameters are updated;

[0106] Based on the image captured from the ghost image, determine the translation amount in the first direction and the translation amount in the second direction; the directions of the translation amount in the first direction and the translation amount in the second direction are perpendicular to each other;

[0107] Based on the translation amount in the first direction and the translation amount in the second direction, the second adjustment mechanism is controlled to perform translation adjustment.

[0108] The preset exposure parameters can be a set of exposure control parameters for the image acquisition device, pre-set to optimize ghost image quality. These parameters guide the image acquisition device to dynamically adjust the exposure during the ghost image calibration phase, ensuring the ghost image signal clock is within a resolvable grayscale range. For example, the preset exposure parameters can be calibrated by the system based on the typical ghost image brightness range and dynamic characteristics of the display module under test, or they can be set and stored in a configuration file based on prior knowledge.

[0109] Preset exposure parameters include preset exposure time and / or preset camera gain.

[0110] The preset exposure time can be a specific value in the preset exposure parameters used to control the light-sensing time of the image sensor. It can be used to control the cumulative brightness of the ghost image, avoiding the invisibility of weak ghosts due to underexposure or the loss of ghost image details due to overexposure. Furthermore, the preset exposure time can be experimentally tested to determine the optimal exposure time value that results in a clear yet unsaturated ghost image by measuring the signal-to-noise ratio and saturation of the ghost image.

[0111] Preset camera gain can be a specific value in the preset exposure parameters used to control the amplification factor of the analog signal from the image sensor. It can be used to enhance the signal strength of low-brightness ghost images, improve their detectability in complex backgrounds, and suppress noise pollution introduced by excessive gain. Furthermore, preset camera gain can be used to adjust the gain at a fixed exposure time so that the grayscale distribution of the ghost image covers the middle range of the sensor's dynamic range, avoiding noise dominance or saturation distortion.

[0112] The initial exposure parameters of the image acquisition device are updated according to the preset exposure parameters. This can be done by reading the exposure time and / or gain value from the preset exposure parameters and overwriting the current default or automatic exposure settings of the image acquisition device.

[0113] Ghost image capture can be a digital image containing clear, multi-level ghost images captured by an image capture device after the exposure parameters have been updated.

[0114] The first directional translation can be a quantitative displacement value obtained from the analysis of the ghost image acquisition image, representing the displacement that the display module under test needs to move along the first orthogonal direction of the image plane. For example, the first directional translation can be obtained by using an image processing algorithm to identify the center offset of the ghost image array in the horizontal or vertical direction and calculate the difference between it and the ideal distribution position.

[0115] Similarly, the second directional translation can be a quantitative displacement value obtained from the analysis of the ghost image acquisition, representing the required movement of the display module under test along the second orthogonal direction of the image plane. For example, the second directional translation is calculated synchronously with the first directional translation, determined based on the distribution offset of the ghost image array in another dimension perpendicular to the first direction.

[0116] Determining the first and second directional translation amounts based on the captured images of the ghost images can be achieved by image processing of the captured images, identifying the distribution characteristics of the ghost image array, and calculating its offset relative to the ideal distribution position in two orthogonal directions. Furthermore, determining the first and second directional translation amounts based on the captured images can employ edge detection and centroid localization algorithms to extract the center coordinates of the ghost images step by step, fit their linear distribution trend, and calculate the displacement from the ideal spacing. Alternatively, a deep learning model can be used to learn the ghost image features and inversely calculate the module's translation error. This allows the visual characteristics of the ghost image distribution to be transformed into quantifiable two-dimensional translation commands, achieving a precise mapping from image observation to physical adjustment.

[0117] The translation adjustment of the second adjustment mechanism is controlled by the translation amount in the first and second directions. The calculated translation amounts in the two orthogonal directions can be used as inputs to drive the second adjustment mechanism to perform displacement compensation along the corresponding spatial axis, thereby realizing the active control of the spatial distribution of ghost images and enabling multi-order ghost images to form a regular and separable array structure on the image sensor plane.

[0118] This embodiment provides an optical axis calibration method that updates the initial exposure parameters of an image acquisition device according to preset exposure parameters to obtain a ghost image acquired by the image acquisition device after the exposure parameters are updated. A first-direction translation and a second-direction translation are determined based on the ghost image. A second adjustment mechanism is controlled to perform translation adjustment based on the first-direction and second-direction translations. By actively adapting to the brightness characteristics of the ghost image, the ghost image acquisition is ensured to have a high signal-to-noise ratio and complete structural information. An image analysis algorithm automatically extracts the offset of the ghost image in two orthogonal directions to achieve data-driven precise displacement compensation. The second adjustment mechanism is controlled to perform two-dimensional translation so that the ghost image forms a regular and predictable array distribution on the image plane. This transforms the ghost image from uncontrollable imaging noise into a measurable and controllable calibration feature, eliminating calibration errors caused by unstable exposure or subjective judgment, significantly improving the accuracy and repeatability of ghost image recognition, and achieving the technical effects of reducing ghost image interference, optimizing optical calibration accuracy, and improving ghost image measurement accuracy.

[0119] In one embodiment, the first adjustment mechanism provides rotational degrees of freedom about a first direction and a second direction, and translational degrees of freedom about a third direction; the second adjustment mechanism provides translational degrees of freedom about the first direction and the second direction, and rotational degrees of freedom about a third direction.

[0120] Among them, the first direction, the second direction and the third direction are perpendicular to each other, and the first direction and the second direction are both parallel to the mounting plane of the display module under test.

[0121] The first direction can be one of the reference coordinate axes parallel to the mounting plane of the display module under test, used to define the reference direction for translation and rotation. The second direction can be a reference coordinate axis orthogonal to the first direction and parallel to the mounting plane of the display module under test, forming a two-dimensional coordinate system for the module mounting plane. The first and second directions together constitute the two-dimensional working plane of the module.

[0122] The third direction can be a reference coordinate axis perpendicular to the mounting plane of the display module under test, which is the main propagation direction of the optical axis. As the core reference axis for optical axis alignment, the third direction can be used to achieve system spacing control and module yaw rotation compensation.

[0123] The mounting plane of the display module under test can be the geometric plane on which the display module is fixed on the adjustment fixture, and its normal direction is consistent with the optical axis of the module. The mounting plane of the display module under test serves as a physical reference system for the first and second directions, ensuring that all adjustment movements are performed within the module coordinate system and avoiding coordinate system confusion.

[0124] This embodiment provides an optical axis calibration method. A first adjustment mechanism provides rotational degrees of freedom around a first and second direction, and translational degrees of freedom along a third direction. A second adjustment mechanism provides translational degrees of freedom along the first and second directions, and rotational degrees of freedom around a third direction. These three directions are mutually perpendicular and unified on the module mounting plane. Thus, the first adjustment mechanism enables rotational alignment of the image acquisition device and control of the optical axis spacing, while the second adjustment mechanism enables translational adjustment and yaw compensation of the module within the mounting plane. This allows the three key steps—primary image alignment, ghost image distribution optimization, and yaw compensation—to be executed independently without coupling interference. This fundamentally eliminates adjustment interference, error accumulation, and convergence instability caused by multi-degree-of-freedom coupling in a single mechanism, achieving the technical effects of reducing ghost image interference, optimizing optical calibration accuracy, and improving ghost image measurement accuracy.

[0125] To more clearly illustrate the technical solution of this application, a detailed embodiment is also provided.

[0126] In the field of near-eye display technology, near-eye display modules are key components, and their optical performance directly affects the user experience. Ghosting, as one of the key indicators of the imaging quality of near-eye display modules, refers to the virtual image that is similar in shape and size to the real image but darker in brightness, produced by the incident light beam of the optical display system being reflected multiple times at the reflective surface of the element. Its intensity directly affects the user's visual experience, and staring at ghosting for a long time can cause visual fatigue and dizziness.

[0127] Before measuring ghost images in near-eye display modules, the optical axis of the measuring device needs to be calibrated to ensure that the module's optical axis is coaxial with that of the measuring system. Currently, most measuring devices use a crosshair pattern displayed on the optical module for optical axis calibration. By adjusting the module's pose, the displayed crosshair pattern is imaged at the center of the ghost image measurement system's image, coinciding with the image center of the measuring system. While this method is widely used in optical axis calibration for measuring systems, it has significant limitations and shortcomings in the optical axis calibration for near-eye display module ghost image measurement. This method does not fully consider the issue of multi-level ghost images in near-eye display modules. Using only the crosshair center for optical axis calibration results in a scattered distribution of multi-level ghost images that may overlap with the true image, severely affecting the accuracy of subsequent extraction of ghost image location regions and measurement of ghost image intensity. In other words, the existing optical axis calibration method for near-eye display module ghost image measurement suffers from the problem of a scattered distribution of multi-level ghost images, leading to complex ghost image extraction in the later stages.

[0128] This embodiment takes a near-eye display module as an example and provides a method for optical axis calibration in ghost image measurement. By using a ghost image measurement device and a multi-order ghost image position calibration method, combined with an industrial camera and a wide field of view lens, the optical axis is calibrated during ghost image measurement of the near-eye display module to ensure the accuracy of the ghost image measurement results.

[0129] This method is applied to, for example Figure 3 The optical calibration measurement system shown is a fixed and adjustable measurement system and related testing equipment testing platform, including: camera 1, lens 2, near-eye display module, fixture, module adjustment mechanism, camera adjustment mechanism, structural components, reference plane, darkroom environment, etc.

[0130] Camera 1 can be an industrial camera used to capture ghost images of the module under test. When paired with a wide field-of-view lens, it forms a ghost image testing system that can acquire images with a bit depth of ≥12 bits and has a high dynamic range.

[0131] Lens 2 can be an industrial lens, used in conjunction with an industrial camera. Its entrance pupil diameter and position match the exit pupil of the module under test, and the entrance pupil distance is ≤15mm. The vertical and horizontal field of view of the lens are larger than the field of view of the module under test, ensuring that the entire field of view of the module can be measured.

[0132] Module 3 can be the display module under test. The ghost image position and intensity of the module need to be determined. The module itself has the function of lighting up the image, and is responsible for lighting up and switching the ghost image test pattern during measurement. In this embodiment, module 3 is the near-eye display module under test. The module is divided into a left-eye module and a right-eye module. This embodiment takes the left-eye module as an example.

[0133] Fixture 4 is used to fix the module position, and the precision of fixture 4 itself ensures that the module under test is placed in the predetermined test position. Fixture 4 is installed on the module adjustment mechanism to fix and ensure the accurate placement of the product under test. At the same time, fixture 4 is responsible for illuminating the module and controlling the switching of different test patterns.

[0134] The camera adjustment mechanism 6, also known as the first adjustment mechanism, includes adjustments in the Rx / Ry / Z directions. The Rx & Ry axis adjustment mechanism 61 adjusts the camera's rotation angle around the X and Y axes to make the camera's optical axis perpendicular to the surface of the module under test. The Z-axis adjustment mechanism 62 adjusts the distance h from the surface of the first lens of the measurement system lens to the surface of the module under test, placing it in a predetermined position.

[0135] The module adjustment mechanism 5, also known as the second adjustment mechanism, includes adjustments in the X / Y / Rz directions. The X-axis adjustment mechanism 52 and the Y-axis adjustment mechanism 53 are responsible for adjusting the position of the module in the X and Y directions. The Y-axis adjustment distance is relatively large, and it is responsible for transporting the module under test back and forth between the test position and the upper and lower modules. The Rz rotation angle 51 adjusts the rotation angle of the module around the optical axis to keep its direction aligned with the camera.

[0136] Structural component 7 is a fixing structure for the camera and lens of the ghost image measurement system. It can be a gantry structure used to fix the camera, lens, Z-axis adjustment and Rx & Ry axis adjustment mechanism 61, and fix the camera and camera adjustment mechanism of the measurement system on the reference plane.

[0137] The distance h between the lens surface and the surface of the module under test is 8. The distance h requires that the entrance pupil position of the lens matches the exit pupil position of the module under test.

[0138] Reference plane 9 is used to fix the module adjustment mechanism and gantry structure, and is the reference plane of the entire measuring device.

[0139] When measuring ghost images, a darkroom environment of 10°C is required, and the brightness of the darkroom must be less than 0.1 lux.

[0140] In one embodiment, such as Figure 4 As shown, an optical axis calibration method is provided, which includes the following steps:

[0141] Install the module 3 to be tested onto the fixture 4, move it below the lens 2 of the measuring system, and the module will illuminate a cross pattern (e.g., Figure 5 The image shown is a crosshair pattern used for coarse positioning calibration. (Align the optical axis of the measurement system camera with the optical axis of the module under test, and turn on camera 1.) The crosshair pattern can be roughly seen in the camera image.

[0142] Adjust the camera's Z-axis adjustment mechanism 62, and use standard gauge blocks to adjust the module 3 and the lens 2 surface to a preset distance h.

[0143] Adjust the module's Rz rotation angle by 51 so that the module's crosshair pattern in the camera image coincides with the camera's central crosshair Rz direction.

[0144] Adjust the camera's Rx & Ry axis adjustment mechanism 61 so that the crosshair pattern of the imaging module in the camera image coincides with the Rx & Ry direction of the camera's central crosshair.

[0145] Module 3 switches patterns, lighting up the ghost test pattern (e.g.) Figure 6 The image shown is a ghost image test pattern used in ghost image measurement. It can also be used for multi-level ghost image position calibration. When the camera is under high exposure or the gain is increased, this pattern will show the multi-level ghost image position of the module. Adjust the camera exposure time or camera gain until the ghost image is displayed in the picture. Adjust the X-axis adjustment mechanism 52 and Y-axis adjustment mechanism 53 of module 3 to adjust the randomly distributed multi-level ghost images along the X and Y directions to a regular distribution, that is, adjust the randomly distributed multi-level ghost images along the X and Y directions to a regular distribution along the X and Y directions.

[0146] Module 3 switches patterns, illuminating the crosshair calibration pattern (e.g.) Figure 5 As shown), adjust the camera exposure time to normal display, and adjust the camera's Rx & Ry axis adjustment mechanism 61 so that the cross pattern of the imaging module in the camera image coincides with the Rx & Ry direction of the camera's central cross.

[0147] At this point, the optical axis of the ghost image measuring device has been calibrated. The optical axis of the module coincides with the optical axis of the camera, and the center of the module image is consistent with the center of the measurement system image. The multi-level ghost images are arranged in a regular pattern, no longer the scattered arrangement before calibration.

[0148] like Figure 7 As shown, when the optical axis of the measuring device is not properly calibrated and the module illuminates the ghost image calibration image, the multi-level ghost image positions displayed by the measuring system are as follows: Figure 7 As can be seen in the left image, multi-level ghost images appear near the four real images in the top, bottom, left, and right. The distribution of the multi-level ghost images is relatively scattered and not arranged in order, which is not conducive to ghost detection and localization. Figure 7 The right image is a circular test image, which shows that the position of the multi-order ghost rings within the brightest true image is offset and overlaps with the true image ring.

[0149] like Figure 8 As shown, this is a distribution diagram of the multi-order ghost image positions of the measurement system when the optical axis of the measuring device is well calibrated. Figure 8 As can be seen in the left figure, near the four real images (top, bottom, left, and right), the multi-level ghost images are arranged sequentially along the X and Y axes. The ghost image positions are relatively regular, which facilitates the extraction of ghost image positions and intensities. Figure 8 In the right image, the centers of the multi-level ghost images in the ring detection image coincide, and the multi-level ghost rings and the true image rings do not interfere with each other and have no overlapping areas, making them easy to detect and extract.

[0150] This embodiment provides an optical axis calibration method that, compared to conventional optical axis calibration methods for near-eye display measurement devices that only use cross center coincidence calibration and ignore the multi-level ghosting phenomenon present in near-eye display modules, results in the multi-level ghosting of the module being scattered and possibly overlapping with the real image, causing serious interference to the subsequent extraction of ghosting regions and detection of ghosting intensity. This method can not only calibrate the optical axis position of the near-eye display module measurement device, but also calibrate the arrangement of the multi-level ghosting of the module, making them arranged regularly along the horizontal or vertical direction, greatly reducing the algorithmic difficulty of subsequent extraction of ghosting regions and detection of ghosting intensity.

[0151] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0152] In one embodiment, such as Figure 9 As shown, an optical axis calibration system is provided. The optical axis calibration system includes an image acquisition device 102, an adjustment fixture 104, a first adjustment mechanism 101, a second adjustment mechanism 103, and a control module 107. The image acquisition device 102 is position-adjusted by the first adjustment mechanism 101, and the adjustment fixture 104 is position-adjusted by the second adjustment mechanism 103. The adjustment fixture 104 is used to install the display module 105 under test.

[0153] The control module 107 is connected to the image acquisition device 102, the first adjustment mechanism 101, and the second adjustment mechanism 103 respectively, and is used to execute the optical axis calibration method as described in any of the above embodiments according to the image image of the image acquisition device 102.

[0154] The optical axis calibration system may include an image acquisition device 102, a first adjustment mechanism 101, a second adjustment mechanism 103, and a control module 107. It is understood that traditional calibration relies on independent manual adjustment devices, lacks system-level linkage capabilities, and is difficult to achieve step-by-step collaborative optimization of the main image and the ghost image. The optical axis calibration system of this embodiment is a complete calibration platform that integrates image acquisition, pose adjustment, and control logic, thereby supporting a multi-step collaborative optical axis calibration process.

[0155] The image acquisition device 102 is connected to the control module 107 and the first adjustment mechanism 101. It can capture the optical image output by the display module under test 105, providing visual feedback for calibration and for identifying the main image and ghost images. For example, the image acquisition device 102 can receive the emitted light from the display module under test 105 through a lens system, convert it into a digital image signal output via a photoelectric sensor. The image acquisition device 102 can receive the optical imaging signal from the display module under test 105 and output data including a crosshair calibration image, a ghost image calibration image, and digital images of multi-level ghost images.

[0156] The first adjustment mechanism 101 is connected to the image acquisition device 102 and the control module 107, and can drive the image acquisition device 102 to perform rotational pose adjustment to align the main image with the reference crosshair and compensate for the offset caused by translation adjustment. For example, the first adjustment mechanism 101 can receive the rotation angle control signal output by the control module 107 and output the pitch and yaw angle changes of the image acquisition device 102.

[0157] The second adjustment mechanism 103 is connected to the adjustment fixture 104 and the control module 107. It can drive the adjustment fixture 104 to perform translational adjustment, actively controlling the spatial distribution of the ghost image in the image plane, and achieving separation by utilizing the geometric offset relationship between the ghost image and the main image. For example, the second adjustment mechanism 103 can receive the translational distance control signal output by the control module 107 and output the linear displacement of the adjustment fixture 104 along the direction perpendicular to the optical axis. Compared with the traditional calibration process, this embodiment introduces a translational adjustment mechanism, thereby effectively utilizing the geometric offset relationship between the ghost image and the main image to achieve spatial separation.

[0158] The control module 107 is connected to the image acquisition device 102, the first adjustment mechanism 101, and the second adjustment mechanism 103. It can receive the image from the image acquisition device 102, analyze image features, and output control commands to the adjustment mechanisms to achieve a closed-loop calibration process, including but not limited to main image alignment and ghost image distribution optimization. For example, the control module 107 interacts with each component via electrical connections. The control module 107 can receive digital image data output by the image acquisition device 102 and output rotation and translation control signals to the first adjustment mechanism 101 and the second adjustment mechanism 103, respectively. The control module 107 identifies the center of the crosshair image and the ghost image distribution pattern based on image processing algorithms, calculates the deviation, and generates adjustment commands. In a specific embodiment, the control module 107 can use an embedded image processing unit, FPGA, etc., for real-time image analysis.

[0159] This embodiment provides an optical axis calibration system. An image acquisition device 102 captures the image of the display module 105 under test. A control module 107 analyzes image features based on the image and outputs control commands. A first adjustment mechanism 101 drives the image acquisition device 102 to perform rotational pose adjustment to align the main image. A second adjustment mechanism 103 drives an adjustment fixture 104 to perform translational adjustment to regulate the spatial distribution of ghost images. The adjustment fixture 104 fixes the display module 105 under test and supports its pose adjustment. This system integrates image acquisition, pose adjustment, and control logic into a complete calibration platform, supporting multi-step collaborative optical axis calibration. The process involves systematically changing the projection position of the ghost image on the image sensor by translating the module under test. By utilizing the fixed geometric offset relationship between the ghost image and the main image, multi-level ghost images are separated in a regular manner and form a predictable spatial array. The control module 107 automatically identifies the distribution pattern of the ghost image based on the imaging image and performs closed-loop adjustment, transforming the ghost image from an uncontrollable source of interference into an adjustable calibration feature. This achieves high-precision optical axis alignment of the main image and active optimization of the spatial distribution pattern of the ghost image, fundamentally solving the problem of the ghost image overlapping and being difficult to separate from the main image. As a result, the technical effects of reducing ghost image interference, optimizing optical calibration accuracy, and improving the accuracy of ghost image measurement are achieved.

[0160] Each module in the aforementioned optical axis calibration system can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of the computer device in software form, so that the processor can call and execute the corresponding operations of each module.

[0161] In one embodiment, a ghost image measurement method is provided. Taking the application of this method to an optical axis calibration system as an example, the optical axis calibration system includes an image acquisition device whose pose is adjusted by a first adjustment mechanism and an adjustment fixture on which a display module to be tested is mounted, whose pose is adjusted by a second adjustment mechanism. The ghost image measurement method includes:

[0162] Step S210: Perform the optical axis calibration method as described in any of the above embodiments.

[0163] Step S220: Obtain the calibration acquisition image obtained by the image acquisition device after optical axis calibration.

[0164] Step S230: Based on the calibration acquisition image, perform ghost image measurement on the display module under test to obtain the ghost image measurement result.

[0165] The calibration acquisition image can be image data containing structured ghost image distribution captured by the image acquisition device after the optical axis calibration process is completed. At this time, the module's optical axis coincides with the camera's optical axis, and the ghost images are already separable and quantifiable. Obtaining the calibration acquisition image obtained by the image acquisition device after optical axis calibration can be achieved by triggering the image acquisition device to save the current frame image after the optical axis calibration process is completed.

[0166] The ghost image measurement results can be a set of ghost image spatial and intensity parameters extracted from calibrated and acquired images using image processing algorithms. This serves as quantitative ghost image evaluation data and can be used to determine the module's optical performance. For example, the ghost image measurement results include, but are not limited to, ghost image intensity distribution curves, ghost image spatial location matrices, and ghost image contrast gradient maps.

[0167] Based on the calibrated images, ghost image measurements are performed on the display module under test to obtain the ghost image measurement results. This can be achieved by performing image processing algorithms on the calibrated images to extract one or more parameters such as the spatial position, relative brightness, contrast, and spacing of ghost images of each order, forming a quantitative evaluation result. Furthermore, template matching algorithms can be used to match a preset ghost image morphology library, and the intensity and offset of ghost images of each order can be determined by sorting them by correlation coefficient. This achieves automated, repeatable, and high-precision quantitative output of ghost image parameters, avoiding recognition errors caused by ghost image overlap.

[0168] This embodiment provides a ghost image measurement method that obtains ghost image measurement results by performing an optical axis calibration method, acquiring calibration acquisition images, and performing ghost image measurement based on the calibration acquisition images. The optical axis calibration achieves precise alignment of the main image and structured control of the spatial distribution of ghost images. The ghost image measurement achieves automated, repeatable, and high-precision quantitative output of ghost image parameters. It can accurately extract quantitative parameters of ghost images of various orders based on high-quality images, avoid recognition confusion and intensity misjudgment caused by ghost image overlap, and achieve the technical effect of improving the accuracy of ghost image measurement.

[0169] In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 10 As shown. The computer device includes a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When executed by the processor, the computer program implements an optical axis calibration method. The display screen can be an LCD screen or an e-ink display screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad mounted on the computer device casing, or an external keyboard, touchpad, or mouse.

[0170] Those skilled in the art will understand that Figure 10 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0171] In one embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the optical axis calibration method of any of the above embodiments:

[0172] Control the first adjustment mechanism and / or the second adjustment mechanism to rotate and adjust so that the crosshair calibration image displayed by the display module under test is aligned with the screen reference crosshair of the image acquisition device;

[0173] The second adjustment mechanism is controlled to perform translation adjustment so that the multi-level ghost images formed by the ghost image calibration image displayed by the display module under test in the screen of the image acquisition device are distributed in a regular manner;

[0174] The first adjustment mechanism is rotated again to align the crosshair calibration image displayed by the display module under test with the screen reference crosshair of the image acquisition device.

[0175] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the optical axis calibration method of any of the above embodiments:

[0176] Control the first adjustment mechanism and / or the second adjustment mechanism to rotate and adjust so that the crosshair calibration image displayed by the display module under test is aligned with the screen reference crosshair of the image acquisition device;

[0177] The second adjustment mechanism is controlled to perform translation adjustment so that the multi-level ghost images formed by the ghost image calibration image displayed by the display module under test in the screen of the image acquisition device are distributed in a regular manner;

[0178] The first adjustment mechanism is rotated again to align the crosshair calibration image displayed by the display module under test with the screen reference crosshair of the image acquisition device.

[0179] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0180] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0181] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0182] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for calibrating an optical axis, characterized in that, An optical axis calibration system is applied, the optical axis calibration system comprising an image acquisition device whose pose is adjusted by a first adjustment mechanism and an adjustment fixture on which a display module under test is mounted, whose pose is adjusted by a second adjustment mechanism; the optical axis calibration method comprises: Control the first adjustment mechanism and / or the second adjustment mechanism to rotate and adjust so that the crosshair calibration image displayed by the display module under test is aligned with the screen reference crosshair of the image acquisition device; The second adjustment mechanism is controlled to translate along a direction perpendicular to the optical axis so that the multi-level ghost images formed by the ghost image calibration image displayed by the display module under test in the image acquisition device are regularly distributed. The first adjustment mechanism is rotated again to align the crosshair calibration image displayed by the display module under test with the screen reference crosshair of the image acquisition device.

2. The optical axis calibration method according to claim 1, characterized in that, Before controlling the first adjusting mechanism and / or the second adjusting mechanism to perform rotational adjustment, the following is also included: Based on the standard gauge block, control the first adjustment mechanism and / or the second adjustment mechanism to perform translation adjustment, so as to adjust the distance between the image acquisition device and the display module under test to a preset spacing.

3. The optical axis calibration method according to claim 1, characterized in that, The control of the first adjusting mechanism and / or the second adjusting mechanism to perform rotational adjustment includes: Control the second adjustment mechanism to rotate and adjust so that the orientation of the cross arm in the displayed cross calibration image coincides with the orientation of the arm of the reference cross in the image; The first adjustment mechanism is controlled to rotate and adjust so that the center of the cross intersection in the displayed cross calibration image coincides with the center of the reference cross on the screen.

4. The optical axis calibration method according to claim 3, characterized in that, The control of the second adjustment mechanism to perform rotational adjustment includes: Acquire the first image to be aligned, captured by the image acquisition device; The third-party rotation amount is determined based on the orientation of the cross arms of the cross calibration image in the first image to be aligned. The second adjustment mechanism is controlled to perform rotation adjustment based on the third-party rotation amount.

5. The optical axis calibration method according to claim 3, characterized in that, The control of the first adjusting mechanism to perform rotational adjustment includes: Acquire the second image to be aligned, captured by the image acquisition device; Based on the offset of the center of the cross intersection of the cross calibration image in the second image to be aligned, a first direction rotation amount and a second direction rotation amount are determined; the rotation axes of the first direction rotation amount and the second direction rotation amount are perpendicular to each other; The first adjustment mechanism is controlled to perform rotational adjustment based on the rotation amount in the first direction and the rotation amount in the second direction.

6. The optical axis calibration method according to claim 1, characterized in that, The control of the second adjustment mechanism to perform translation adjustment includes: The initial exposure parameters of the image acquisition device are updated according to preset exposure parameters; the preset exposure parameters include preset exposure time and / or preset camera gain. Acquire the ghost image obtained by the image acquisition device after the exposure parameters are updated; Based on the captured image of the ghost image, a first directional translation amount and a second directional translation amount are determined; the directions of the first directional translation amount and the second directional translation amount are perpendicular to each other; Based on the translation amount in the first direction and the translation amount in the second direction, the second adjustment mechanism is controlled to perform translation adjustment.

7. The optical axis calibration method according to any one of claims 1 to 6, characterized in that, The first adjustment mechanism provides rotational degrees of freedom about a first direction and a second direction, and translational degrees of freedom about a third direction; the second adjustment mechanism provides translational degrees of freedom about the first direction and the second direction, and rotational degrees of freedom about a third direction. Wherein, the first direction, the second direction, and the third direction are perpendicular to each other, and the first direction and the second direction are both parallel to the mounting plane of the display module under test.

8. An optical axis calibration system, characterized in that, The optical axis calibration system includes an image acquisition device, an adjustment fixture, a first adjustment mechanism, a second adjustment mechanism, and a control module. The image acquisition device is position-adjusted by the first adjustment mechanism, the adjustment fixture is position-adjusted by the second adjustment mechanism, and the adjustment fixture is used to mount the display module under test. The control module is connected to the image acquisition device, the first adjustment mechanism, and the second adjustment mechanism respectively, and is used to execute the optical axis calibration method as described in any one of claims 1 to 7 according to the image image of the image acquisition device.

9. A method for measuring ghost images, characterized in that, The method is applied to an optical axis calibration system, which includes an image acquisition device whose pose is adjusted by a first adjustment mechanism and an adjustment fixture on which a display module to be tested is mounted, whose pose is adjusted by a second adjustment mechanism. The ghost image measurement method includes: Perform the optical axis calibration method as described in any one of claims 1 to 7; Acquire the calibration image obtained by the image acquisition device after optical axis calibration; Based on the calibration acquisition image, ghost image measurement is performed on the display module under test to obtain the ghost image measurement result.

10. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the method of any one of claims 1 to 7.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method of any one of claims 1 to 7.

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