Device for checking the alignment state of an image sensor and method for checking the alignment state of an image sensor

Abstract

Device (200) for checking the alignment state of an image sensor (120) of a camera module (115), wherein the device (200) has the following features: a first optical device (205) with a first optical element (220) that can be illuminated by a first light source (210) and moved along a first optical axis (215); a second optical device (235) with a second optical element (250) that can be illuminated by a second light source (240) and moved along a second optical axis (245), wherein the second optical device (235) is arranged at a distance from the first optical device (205) and the first optical axis (215) has an intersection (260) with the second optical axis (245), wherein the camera module (115) to be tested can be arranged in a region of the intersection (260); and an evaluation device (270) configured to read in position information (275) representing a position of the first and second optical elements (220, 250) detected at a specific time, and an image signal (285) representing image information detected by the image sensor (120) at the specific time, wherein the evaluation device (270) is configured to assign image information to each detected position using the image signal (285) and / or the position information (275) in order to determine the adjustment state of the camera module (115).

Description

[0001] The present approach relates to a device for checking the alignment state of an image sensor and a method for checking the alignment state of an image sensor.

[0002] Several approaches to the active alignment of camera modules are known from the state of the art. Active alignment is implemented within a production process. After completion of the manufacturing process, it is necessary to verify the quality of the camera system's alignment. The alignment can be negatively affected by manufacturing steps such as uneven curing of the adhesive used to fix the optics and sensor, as well as by mechanical stresses or temperature effects. In many cases, finished camera modules are tested with simple test image setups to determine whether they meet the specified focus criteria.

[0003] DE 10 2012 016 337 B4 discloses a method for determining the optical quality of a photomodule. Disclosure of the invention

[0004] Against this background, the present approach introduces a device for checking the alignment state of an image sensor and a method for checking the alignment state of an image sensor according to the main claims. Advantageous embodiments are described in the respective dependent claims and the following description.

[0005] The device and method presented here advantageously improve the verification of the alignment status of a camera's image sensor with respect to the associated optics. This allows for the quantitative determination of the degree of mechanical tilt or sensor misalignment that can lead to a loss of sharpness.

[0006] A device for checking the alignment status of an image sensor of a camera module is presented, wherein the device has the following features: a first optical device comprising a first optical element that can be illuminated by a first light source and moved along a first optical axis, a second optical device with a second optical element that can be illuminated by a second light source and moved along a second optical axis, wherein the second optical device is arranged (for example, radially) at a distance from the first optical device and the first optical axis has an intersection with the second optical axis, wherein the camera module to be tested can be arranged in a region of the intersection point, and an evaluation device configured to read position information representing a position of the first and second optical elements detected at a given time, and to read an image signal representing image information detected by the image sensor at that given time, wherein the evaluation device is configured to assign image information to each detected position using the image signal and additionally or alternatively the position information in order to determine the alignment state of the camera module.

[0007] For example, the device presented here can be used to check the image sensor of a camera in relation to its associated optics, for instance, at the end of the camera's manufacturing process. An important measurement parameter when checking the camera alignment after assembly can be the degree of tilt between an image plane of the optics and a sensor plane, which affects the sharpness and contrast distribution in the image field. The camera module under test, which may consist of optics and a sensor, can be illuminated using the optical devices, for example, with collimated light. The illumination can be performed at the axial position, parallel to the optical axis of the test piece, as well as at one or more off-axis positions.To advantageously obtain a quantitative assessment of the degree of mechanical sensor tilt or defocus in a fully assembled camera system, focusable optical devices, also known as collimators, can be used with the device presented here. For purely axial focusing, one optical device is sufficient. If the tilt of the image plane in one direction is to be determined, an additional off-axis optical device is required. At least one further off-axis optical device is necessary, which must not be arranged along the same line as the axial optical device and the first off-axis optical device, to determine the tilt of the image plane of the optical system under test in two directions. To increase the number of measurement positions and to obtain additional information about the curvature of the image plane, further off-axis optical devices can be added.Determining the spatial position of the image plane of the test object represents an advantageous application of the invention. For improved readability, a first and a second optical device will be referred to in the following description. By moving the optical elements within the optical devices, a test object can be imaged at different apparent object distances. For this purpose, the optical elements can, for example, be designed as reticles that can be moved along the optical axis of the respective optical device, thus making it possible to perform a focusing cycle.

[0008] The following approximate relationship can be established between the motion Δz. OE of the optical element within the optical device and the z-position of the measuring point in the image plane of the camera system under test Δ ZK The following should be taken into account: Δzk=fK2 / fOE2×ΔzOE where fk the focal length of the optics of the camera system to be tested and f OE the focal length of the optical element.

[0009] It is important to establish a clear relationship between the z-position, which can be determined by the position of the reticle in the optical device, and, for example, a specific image contrast value, such as the modulation transfer function (MTF) of the projected image. This relationship can advantageously be ensured quickly and with high accuracy using the device presented here. The device is designed to process the image information captured by the test specimen, i.e., for example, the comparison between the detail contrast at the edges of an object and the detail contrast of a pictorial representation of the same object, as described by the MTF value.For this purpose, the device includes the evaluation unit, which is designed to assign image information, for example an MTF value, to each acquired position information of the optical elements using the image signal and additionally or alternatively the position signal, in order to determine the alignment status of the camera module. This advantageously allows synchronization of the acquired image information with the position of the optical elements in the optical devices.

[0010] According to one embodiment, the device can include an image capture circuit, which may be configured to control or read the image sensor depending on the position of the optical elements, and which may be configured to provide the image signal. For example, the image capture circuit, which can also be called a frame grabber, may be an electronic circuit for digitizing analog image signals or for reading digital image data. The image capture circuit may also be configured, additionally or alternatively, to connect the camera module to a wide variety of systems. The device may therefore be designed, for example, to process the image information captured by the image sensor using the image capture circuit. The image capture circuit may, for example, be configured to provide the image signal to the evaluation unit via an interface.Additionally or alternatively, the frame grabber can, for example, be connected or connectable to a control unit for controlling the optical devices via signal transmission. In other words, the frame grabber serves for the electronic processing or transmission of the image information captured by the sensor.

[0011] According to a further embodiment, the device can include a control unit for controlling the first and second optical elements. The control unit can be configured to provide position information. For example, all optical elements, more precisely their motor controls or motion drives, can be electronically connected to the control unit in parallel. Each optical element can, in turn, have a position encoder, for example, by means of which the exact position of the respective optical element can be determined. Advantageously, the movement of the individual optical elements by the control unit can be optimally coordinated with the other optical elements. Additionally, the control unit can be configured to provide the respective positions using the position information. This advantageously optimizes the synchronization of position and image information.

[0012] According to a further embodiment, the device can be configured to position the first and second optical elements at a specific time such that the intermediate images of the optical elements lie in the same plane (intermediate image plane). These intermediate images are projected onto the image plane of the optical system under test. For example, the first optical element of the first optical device can be moved from a first starting position to a first end position. Similarly, the second optical element of the second optical device can be moved from a second starting position to a second end position. The intermediate images of the optical elements move from a first, common, apparent object plane to a second, common, apparent object plane. The first, apparent object plane correlates with the first and second starting positions, and the second, apparent object plane correlates with the first and second end positions.Between the first and second object planes, a variable number of predefined additional object planes can be traversed. This relationship naturally also applies to all conceivable planes along the trajectory of the optical elements. The velocity profiles of the first and second optical elements can be coordinated so that the intermediate images of all optical elements are always simultaneously positioned in the predefined object planes. This advantageously allows a trajectory to be defined along which the optical elements can be moved.

[0013] According to a further embodiment, the device can have a third optical unit with a third optical element that is illuminated by a third light source and movable along a third optical axis. The third optical unit can be arranged (for example, radially) at a distance from the first and second optical units, and the third optical axis can intersect the first and second optical axes, with the camera module to be tested being positioned in a region of this intersection. For example, the illumination of the optical elements can occur both at the axial position of the first optical unit, parallel to the optical axis of the test object, and at several off-axis positions. Ideally, the three optical elements are not arranged in a single plane, so that the image points projected in the camera module span an image plane whose angular position can be determined.At each z-position of the optical elements, a contrast (MTF) value for a fixed spatial frequency can be determined at each of the three field positions. The result of the measurement can be the focus curve, a representation of the image contrast as a function of the z-position. Advantageously, the degree of tilt of the image plane relative to the sensor plane can be deduced from the position of the maxima of the three curves along the z-direction, and defocus can also be optimally determined. For camera systems that are not yet permanently mounted together, a best-focus position can now be determined using active alignment between the optics and the sensor.

[0014] The use of three optical elements whose optical axes do not lie in a single plane is particularly advantageous for determining the tilt of the image plane of a camera module. Additional optical elements can be used to refine the determination and to obtain information about the field curvature of the test specimen.

[0015] Furthermore, a method for checking the alignment status of an image sensor of a camera module (for example, using a variant of a device presented here) is introduced, wherein the method comprises the following steps: Moving a first optical element, illuminated by a first light source, along a first optical axis of a first optical device, wherein the first optical axis essentially corresponds to an optical axis of the camera module under test, and moving a second optical element, illuminated by a second light source, along a second optical axis of a second optical device, wherein the second optical device is arranged (for example, radially) spaced apart from the first optical device and the first optical axis has an intersection with the second optical axis within an entrance pupil of the camera module.

[0016] Reading in position information, representing the position of the first, second, third, and / or each subsequent optical element as captured at a specific time, and reading in an image signal, representing image information captured by the image sensor at that specific time, and

[0017] Assigning the position to the image information using the image signal and additionally or alternatively the position information to determine the alignment status of the camera module.

[0018] For example, the method can be performed using a variant of the previously presented device to check the alignment of a camera's image sensor with respect to the associated optics. Such a check can be useful, for instance, at the end of the camera's manufacturing process. After completion of the manufacturing process, it is necessary to verify the quality of the camera system's alignment. The alignment can be negatively affected, for example, by manufacturing steps such as uneven curing of the adhesive used to fix the optics and sensor together, but also by mechanical influences or temperature effects. To obtain a quantitative assessment of the extent of sensor tilt or defocusing of the image sensor in a fully assembled camera system, the method presented here can advantageously be carried out.The general aim of the method described here is to directly assign the corresponding image signal to each position of the optical elements with high accuracy, meaning with the lowest possible time offset (latency) and temporal inaccuracy, or rather, to capture the image information and the corresponding position of the optical elements almost simultaneously. This is necessary to determine the position of highest image contrast with the greatest possible accuracy (in the micrometer range).

[0019] According to one embodiment, the method can include a step of outputting a position trigger signal to determine the time for acquiring the position of the first and, additionally or alternatively, a second optical element, whereby the position information can be provided in response to the position trigger signal. For example, the illuminated optical elements of the optical devices can be continuously moved from a starting position to an end position. Simultaneously, successive images of the optical elements can be captured by the test specimen using the image sensor. The individual image data, which can also be referred to as frames, can be processed, for example, by an image capture circuit or frame grabber. This image capture circuit can, for example, output the position trigger signal as soon as an image has been completely captured.Alternatively, the position trigger signal can be output at the beginning of image acquisition. Simultaneously with the position trigger signal, the image signal, which represents the image information, can be provided, for example, to an evaluation unit. The position trigger signal can, for instance, be output to a control unit for controlling the optical elements. In response to the position trigger signal, the current position of the optical elements can be provided to the evaluation unit using the position information. Thus, the image information can advantageously be evaluated as a function of the position of the optical elements.In other words, direct synchronization between the frame grabber and the control unit improves the measurement process by enabling continuous, high-speed focusing and eliminating the need for an indirect link between image position and encoder position via timestamps, which would necessarily require a linear, time-dependent movement process. Position-controlled triggering of the image acquisition also allows for non-linear (accelerated) motion profiles.

[0020] According to a further embodiment, the method can include a step of outputting an image trigger signal to determine the time for capturing the image information, whereby the image signal can be provided in response to the image trigger signal. For example, the optical elements can be moved continuously from a starting position to an end position. As soon as an optical element or an encoder of the corresponding optical device has reached a predefined position, the image trigger signal can be output. The image trigger signal can be output, for example, upon reaching non-equidistant position markers, such as at positions 0 mm, 0.1 mm, 0.2 mm, 0.5 mm, 1.0 mm, 2.0 mm, and 5.0 mm. At each of these or other predefined positions, the image trigger signal can, for example, be output to the image capture circuit.Simultaneously, the position signal can be provided to the evaluation unit. Responding to the image trigger signal, the image capture circuit can initiate an image acquisition process. Subsequently, the respective image information can be read out and provided to the evaluation unit using the image signal. The evaluation unit can then assign each piece of image information to the predefined position of the optical elements. Alternatively, the image information can be temporarily stored and transferred and assigned to the positions at the end of the focusing process. This step also advantageously allows for the evaluation of the image information as a function of the optical element encoder position.

[0021] According to a further embodiment, the method can include a step of storing the image information and, additionally or alternatively, the position of the first and second optical elements. In a first variant, the respective position of the first and second optical elements is stored after it has been acquired at a predefined time in response to a position trigger signal. Approximately simultaneously with the output of the position trigger signal, the image information is also stored in this variant. In a second variant, the image information is stored after it has been acquired at a defined time in response to an image trigger signal. Approximately simultaneously with the output of the image trigger signal, the respective position of the first and second optical elements is also stored in this variant.

[0022] According to a further embodiment, the first optical element can be moved at a first speed, and the second and / or each subsequent optical element at a second speed that differs from the first. For example, the control device for controlling the optical elements can be configured such that the intermediate images of the optical elements of all optical devices are advantageously located in the same object plane at the same time. The first optical axis of the first optical device essentially corresponds to an optical axis of the camera module under test, and the second and / or subsequent optical device(s) are arranged radially spaced from the first optical device. Consequently, this means that, for example, the second optical element of the second optical device should be moved at a different speed than the first optical element.For example, the traverse speed of a so-called master optical unit, such as the optical unit corresponding to the optical axis of the camera module, can be defined as a guideline value against which the speeds of the other optical units can be adjusted accordingly by the control system. Each individual optical unit can include its own position encoder, which can be used, for example, in a so-called closed-loop control system for position and speed control. The signals from the individual optical units can be transmitted electronically to the control unit in parallel. Since the relationship between the positions of the optical elements and apparent object planes (intermediate image planes) is non-linear, it is also advantageous to implement a corresponding speed profile to achieve a uniform distribution of measurement points in the image space.

[0023] According to a further embodiment, the first and second velocities can have a value greater than 0 m / s at any given time. Additionally or alternatively, the temporal profile of the first and second and / or subsequent velocities can be mathematically described by a nonlinear function. Advantageously, a continuous focusing run at high speed can be performed, thus eliminating the need for an indirect link between image information and the position of the optical elements via timestamps, which would necessarily require a temporally linear traversal process.

[0024] According to a further embodiment, the method can include a step of providing a motion signal, wherein the motion signal can represent a specification of the positions to be moved to by the optical elements, in particular wherein the specification can be stored as a position table. For example, one or more sets of optical element z-positions can be stored in the control unit. The individual z-positions can correspond to different object planes into which the images of the optical elements are seemingly projected for the camera module. These apparent object planes are also referred to as intermediate image planes. Advantageously, the velocity profiles of the first optical element and the second optical element can be coordinated such that all images of the optical elements are always simultaneously located in the predefined object planes.For example, the transfer of the set to positions can be done in the form of a position table, and the positions can be equidistant or non-equidistant. This advantageously allows a trajectory to be defined along which the optical elements of the optical devices are moved.

[0025] This process can be implemented, for example, in software or hardware, or in a hybrid form of software and hardware, for example in a control unit.

[0026] Also advantageous is a computer program product or computer program with program code that can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and is used to carry out, implement and / or control the steps of the method according to one of the embodiments described above, in particular if the program product or program is executed on a computer or device.

[0027] Examples of the approach presented here are shown in the drawings and explained in more detail in the following description. It shows: Fig. 1 a schematic representation of an embodiment of a measurement of a tilt between an image plane of an optical unit and a sensor plane; Fig. 2 a schematic representation of an exemplary embodiment of a device; Fig. 3A a schematic representation of an embodiment of a device in top view; Fig. 3B a schematic cross-sectional representation of an embodiment of a device in side view; Fig. 4 a schematic representation of an exemplary embodiment of a device; Fig. 5 a schematic representation of an exemplary embodiment of a device; Fig. 6 a flowchart of an embodiment of a method for checking the alignment status of an image sensor of a camera module; Fig. 8 a flowchart of an embodiment of a method for checking the alignment status of an image sensor of a camera module; and

[0028] In the following description of favorable embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, without repeating these elements.

[0029] Fig. Figure 1 shows a schematic representation of an embodiment of a measurement of the tilt between an image plane 100 of an optical unit 105 and a sensor plane 110. An important measurement parameter when checking camera alignment is the degree of tilt between the image plane 100 of the optics or optical unit 105 and the sensor plane 110. In the measurement shown here, the camera module 115 under test, consisting of optical unit 105 and image sensor 120, can be illuminated with collimated light. The sensor, or rather the optics of the test object, can be moved relative to each other, whereby an MTF value 130 for a fixed spatial frequency can be determined at each of the three field positions at each z-position 125. The result of the measurement, the focusing curve 135 with the contrast values ​​as a function of the z-position, is shown on the lower left side of the figure.The position of the maxima of the three curves along the z-direction allows conclusions to be drawn about the degree of tilt of the image plane 100 relative to the sensor plane 110, and also the determination of defocus. The illustration shows this in two dimensions; analogously, this evaluation can also be performed in three dimensions. For camera systems that are not yet permanently mounted, an optimal focus position can be determined by actively aligning the optics and sensor. After completion of the manufacturing process, it is necessary to check the quality of the camera system's alignment. The alignment can be negatively affected, for example, by manufacturing steps such as uneven curing of the adhesive used to fix the optics and sensor together, as well as by mechanical stresses or temperature effects.In many cases, finished camera modules are tested with simple test image setups to determine whether they meet the specified sharpness criteria. However, this method provides no quantitative indication of the degree of mechanical tilt or sensor misalignment that led to the observed drop in sharpness. This makes systematic optimization of the manufacturing process more difficult.

[0030] Fig. Figure 2 shows a schematic representation of an embodiment of a device 200. The device 200 is designed to check the alignment status of an image sensor 120 of a camera module 115. For this purpose, the device 200 comprises a first optical unit 205 with a first optical element 220, which can be illuminated by a first light source 210 and moved along a first optical axis 215. In the representation shown here, the first optical axis 215 corresponds to an optical axis 225 of the camera module 115, which is arranged below the first optical unit 205 in the figure. The device 200 further comprises a second optical unit 235 with a second optical element 250, which can be illuminated by a second light source 240 and moved along a second optical axis 245.The second optical device 235 is arranged radially (here specifically rotated by an angle relative to the first optical axis 225) from the first optical device 205, and the first optical axis 215 has an intersection point 260 with the second optical axis 245, with the camera module 115 to be tested being located in a region of the intersection point 260. In practical implementation, further optical devices can be added accordingly.

[0031] Furthermore, the device 200 includes an evaluation unit 270 configured to read a position signal 275. The position signal 275 represents the position of the first and second optical elements 220 and 250, as detected at a specific time, and in this embodiment, it can be provided to the evaluation unit 270 by a control unit 280 for controlling the optical elements 220 and 250. The evaluation unit 270 is also configured to read an image signal 285, which represents image information detected by the image sensor 120 at the specific time. In this embodiment, the evaluation unit 270 is configured to assign image information to each detected position using the image signal 285 and the position signal 275 in order to determine the alignment state of the camera module. In another embodiment, only the position signal or only the image signal can be used.

[0032] Fig. Figure 3A shows a schematic top view of an embodiment of a device 200. This device includes an axial optical unit 205 and several off-axis optical units 235, 300, which are spaced radially from the axial optical unit 205 at various angles. The device 200 shown here corresponds to or is similar to the one described in the preceding figure. Fig. The device described in Section 2 differs from the device shown here, with the difference that the device 200 comprises a third optical device 300 in addition to the first optical device 205 and the second optical device 235. Similar to the first optical device 205 and the second optical device 235, the third optical device 300 has a third optical element 315 that can be illuminated by a third light source 305 and is movable along a third optical axis 310. The third optical device 300 is arranged radially spaced from the first and second optical devices 205 and 235, and the third optical axis 310 has an intersection point 260 with the first and second optical axes 215 and 245, respectively. The camera module 115 to be tested can be arranged in a region of the intersection point 260. Similarly, further optical devices can also be arranged radially around the entrance aperture of the camera module to be tested. This fact is shown in the top view in . Fig. 3A illustrates this.

[0033] Fig. Figure 3B shows a schematic representation of an embodiment of a first optical device 205. The first optical device 205 shown here corresponds to or is similar to that described in the preceding figures. Fig. 2 and Fig. The first optical device described in Section 3A comprises a housing 330 in which the first light source 210 is arranged. The first light source 210 is configured to emit a light beam 335 that can be collimated by a projection lens 340. In this embodiment, the first optical element 220 is arranged between the first light source 210 and the projection lens 340. This optical element 220 is movable along the first optical axis 215, which corresponds to the optical axis 225 of the camera module 115 under test. The first optical element 220 is shown to be controllable by means of a motor drive and a position encoder 345, but only as an example.Depending on the position of the first optical element 220, the light beam 335 can be modified such that different apparent object distances can be set for the illuminated image sensor 120 of the camera module 115, and various contrast (MTF) values ​​can be evaluated for these object distances. In other words, the optics 340 generates a virtual intermediate image of the optical element 220, which in turn is projected as an object by the optics of the system 115 under test onto its sensor 120.

[0034] Fig. Figure 4 shows a schematic representation of an embodiment of a device 200. The device 200 shown here corresponds to or is similar to the one described in the preceding figures. Fig. 2 and Fig. The device described in Section 3 differs in that, in this embodiment, the device 200 comprises an image capture circuit 400. The image capture circuit 400, which can also be referred to as a frame grabber, is configured in this embodiment to read the image sensor 120 depending on the position of the optical elements 220, 250, 315 and to provide the image signal 285 to the evaluation unit 270. By way of example only, the image capture circuit 400 is additionally configured to output a position trigger signal 405 to the control unit 280. In this embodiment, the control unit 280 is configured to determine, in response to the position trigger signal 405, the time for detecting the position of the optical elements 220, 250, 315 and to store the respective position using a storage unit 407, which can also be referred to as an optical element position memory.The positions of the optical elements 220, 250, 315 can then be provided using the position signal 275.

[0035] In other words, in this embodiment, the device 200 is configured to process the image information captured by the test specimen using the image capture circuit 400, the image capture circuit 400 being connected to the control unit 280 for signal transmission purposes only by way of example. In this embodiment, all optical devices 205, 235, 300, more precisely their motor controls, are electronically connected in parallel to the control unit 280. The control unit 280 is configured in this embodiment to store the positions of the optical elements 220, 250, 315 at the time determined by the position trigger signal 405, which can be the beginning or the end of an image acquisition. The optical elements 220, 250, 315 are continuously moved from a starting position 410 to an end position 415.Each position of the optical elements correlates with a corresponding intermediate image position. The optical elements are arranged along their respective optical axes such that all intermediate images lie in a common, apparent object plane. Thus, the intermediate images also move from a starting position 410 to an end position 415. For clarity, the illustration shown here depicts only the first object plane 410, which corresponds to a starting position for the intermediate images of optical elements 220, 250, and 315, and the second object plane 415, which corresponds to an end position for the intermediate images of optical elements 220, 250, and 315. In other embodiments, the intermediate images of the optical elements can be moved along a variable number of object planes. For this purpose, several sets of positions of the optical elements are stored in the control unit in this embodiment.The individual positions correspond to different object planes 410, 415, in which the intermediate images of the optical elements 220, 250, 315, which can also be referred to as reticles, can be arranged. Due to the radial spacing of the optical devices 205, 235, 300 from each other, the distance I2 between the start position and the end position of the second optical element 250 is greater than the distance I1 between the start position and the end position of the first optical element 220. To compensate for this, the velocity profiles of the first optical device 205, the second optical device 235, and the third optical device 300, as well as those of other optical devices, can be coordinated so that all intermediate images of all optical elements 220, 250, 315 can always be arranged simultaneously in the predefined object planes 410, 415.The control system for the optical units 205, 235, 300 is designed such that the intermediate images of the optical elements of all optical units 205, 235, 300 are located in the same object plane 410, 415 at the same time. As a consequence, the optical elements of the off-axis optical units 235, 300 move at a different speed than the optical element of the axial optical unit 205. The travel speed of one of the first optical units 205 is specified here only as an example, serving as a guideline value to which the speeds of the other optical units 235, 300 are adjusted accordingly by the control system. Each of the optical units 205, 235, 300 includes, for example, its own position encoder, which can be used in a closed-loop control system for position and speed control.The signals from the individual optical devices 205, 235, 300—that is, the signal from the axial optical device 205 and the signals from the various off-axis optical devices 235, 300—can be electronically transmitted in parallel to the control device 280. Since the relationship between the position of the optical element and the apparent object plane is non-linear, a corresponding velocity profile can be implemented to achieve a uniform distribution of measurement points in the object space. The control device 280 is therefore configured, by way of example only, to provide a first movement signal 420, a second movement signal 422, and a third movement signal 425 to the optical devices 205, 235, 300, where the movement signals 420, 422, and 425 represent a specification for the positions that the optical elements 220, 250, and 315 can reach.For this purpose, only an example specification for the positions that can be approached by the optical elements 220, 250, 315 is stored as position table 430 in the control unit 280.

[0036] Fig. Figure 5 shows a schematic representation of an embodiment of a device 200. The device 200 shown here corresponds to or is similar to the one described in the preceding figures. Fig. 2, Fig. 3 and Fig. 4, Fig. The device described in Section 5 differs in that, in this embodiment, the control unit 280 is configured to output an image trigger signal 500. For illustrative purposes only, the image trigger signal 500 can be provided to the image capture circuit 400 to determine the time for acquiring the image information. Accordingly, in this embodiment, the image trigger signal 500 can be triggered as soon as the optical elements 220, 250, 315 have reached a predefined position. The predefined positions to be approached can be stored in a position table 430. In this embodiment, the image capture circuit 400 is configured to control the image sensor 120 in response to the image trigger signal 500 and to start an image acquisition process. After the image information has been acquired, the image signal 285 is available.In this embodiment, the image signal 285 can only be provided indirectly to the evaluation unit 270, since an image output unit 505 is only connected upstream of it as an example. Similarly, in this embodiment, the position signal 275 can only be provided indirectly from the control unit 280 to the evaluation unit 270 using a position output unit 510.

[0037] Fig. Figure 6 shows a flowchart of an embodiment of method 600 for checking the alignment status of an image sensor of a camera module. The method 600 presented here uses a device as described in the preceding Fig. 2, Fig. 3, Fig. 4 and Fig. 5, Fig. The method described in section 6 is feasible. Method 600 comprises step 605 of moving a first optical element, illuminated by a first light source, along a first optical axis of a first optical device. The first optical axis essentially corresponds to an optical axis of the camera module under test. In step 605, a second optical element, illuminated by a second light source, is also moved along a second optical axis of a second optical device. The second optical device is arranged radially spaced from the first optical device, and the first optical axis intersects the second optical axis within the camera module. For illustrative purposes only, the first optical element is moved at a first velocity, and the second optical element at a second velocity that differs from the first.In this embodiment, both the first and second velocities have a value greater than 0 m / s at any given time, and the time course of the first and second velocities can only be described mathematically by a nonlinear function as an example. Further optical devices can be added to this scheme.

[0038] Furthermore, the procedure 600 includes a reading step 610. In this step 610, position information is read in, representing the position of the first and second optical elements as captured at a specific time. Additionally, in step 610, an image signal is read in, representing image information captured by the image sensor at that specific time. Step 610 is followed by step 615, which assigns the positions to the image information using the image signal and the position information to determine the alignment state of the camera module.

[0039] The goal of the method described here, 600, is to directly assign the corresponding image signal to each position with high accuracy, meaning with the lowest possible time offset (latency) and temporal inaccuracy, or rather, to acquire the image information and the corresponding positions of the optical devices virtually simultaneously. This is necessary to determine the position of highest image contrast with the greatest possible accuracy (in the micrometer range). With method 600, the direct synchronization between the frame grabber and the optical device control enables continuous, high-speed focusing and avoids the indirect link between the image and encoder position via timestamps, which would necessarily require a linear temporal process.

[0040] Fig. Figure 7 shows a flowchart of an embodiment of method 600 for checking the alignment status of an image sensor of a camera module. The method 600 presented here corresponds to or is similar to the one described in the preceding Fig. The method described in section 7 differs from the method described in section 7, with the difference that it includes additional steps. In this embodiment, step 605, the movement step, is followed by step 700, the output of a position trigger signal. The position trigger signal is output only as an example to determine the time for acquiring the positions of the first and second optical elements (and, for example, other optical elements). Furthermore, in this embodiment, method 600 includes step 705, the storage of the image information and the positions of the first and second optical elements, as well as all other optical elements. Only then, in this embodiment, is the position information made available in response to the position trigger signal, read in together with the image signal, and each position is assigned to each piece of image information.In other words, in this embodiment of the method, 600 optical elements in focusable collimators are moved continuously, i.e., not stepwise, from a starting position to an end position. During this process, the test specimen acquires successive images of the reticle, and, by way of example, the individual image information (frames) is processed by a frame grabber. The frame grabber triggers a signal as soon as an image has been completely acquired. In another embodiment, the signal can also be output at the beginning of image acquisition. This is followed by the storage of the image information and the optical element encoder position information in response to the trigger signal. Subsequently, the image information, for example, the contrast values, is evaluated as a function of the optical element encoder position.

[0041] Fig. Figure 8 shows a flowchart of an embodiment of method 600 for checking the alignment status of an image sensor of a camera module. The method 600 presented here corresponds to or is similar to that described in the preceding Fig. 7 and Fig.Method 8 is described, with the difference that it includes alternative and additional steps. By way of example only, method 600 includes step 800 of providing a motion signal. This motion signal represents a specification for the positions to be reached by the optical elements in step 605 of the movement process. In this embodiment, this specification is stored as a position table with non-equidistant position markers. In step 805, by way of example only, an image trigger signal is then triggered upon reaching the positions 0 mm, 0.1 mm, 0.2 mm, 0.5 mm, 1.0 mm, 2.0 mm, and 5.0 mm, in order to determine the time for acquiring the image information, with the image signal being provided in response to the image trigger signal. In other words, in this embodiment, the optical elements in the focusable collimators move continuously from a starting position to an end position.A trigger signal is generated as soon as the encoder reaches a predefined position. These trigger signals are simply passed on to the frame grabber, which then starts the image acquisition process. This is followed by reading and storing the image information, assigned to the initially predefined position. In another embodiment, the image information can be temporarily stored and transferred and assigned to the positions at the end of the focusing process. In this embodiment, the image information, for example, the contrast values, is evaluated as a function of the optical element encoder position.

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