Testing device for optical sample and method for testing optical sample

Abstract

To provide a testing device for testing an optical sample.SOLUTION: A testing device 100 includes a radiation source 145 for emitting a plurality of optical beams 115 along an optical axis 117. In addition, the testing device 100 includes an optical element formed as a filter element 125 for imprinting a specific polarization-direction onto the plurality of optical beams 115 or filtering light reflected or transmitted by the optical sample 105. The testing device 100 also includes a rotation unit 135 designed for rotating the optical sample 105 lying on the optical axis 117 by a rotation angle 140 relatively to the filter element 125. The testing device 100 also includes a detection unit 147 for determining a polarization axis of the optical sample 105 from the rotation angle 140 and a reflected light beam, from the plurality of optical beams 115, reflected by the optical sample 105 or transmitted through the optical sample 105, as well as a measure for the decentration value of the optical sample.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The approach presented herein provides an inspection device for an optical inspection object and an inspection device for an optical inspection object according to the main claims.

[0002] Many lenses either generate a refractive power (liquid crystal lenses) or are coated accordingly (polarizing layers, lambda / 4 layers, etc.) and therefore have properties that affect the polarization. When mounting such lenses, both the centering of the lenses and the alignment of the polarization axis are important. However, several work steps are often required to measure the centering on the one hand and the alignment of the polarization axis on the other hand. The implementation of several work steps, however, requires additional costs in terms of the design of the test device in order to measure the centering on the one hand and the alignment of the polarization axis on the other hand in the various work steps. At the same time, such a test device requires a large construction space. One consecutive measurement of the centering and the polarization is therefore performed with two different measuring heads. Correspondingly, the measurement technology requires a large construction space and the measurement time is long due to two separate individual measurements.

[0003] Against this background, it is an object of the present invention to provide an improved inspection device for optical inspection objects and an improved method for inspecting optical inspection objects.

[0004] The above problem is solved by the subject matter of the main claim.

[0005] The approach presented herein provides an inspection apparatus for an optical test object for determining decentering and polarization properties of the test object, the inspection apparatus having the following features: a light source for emitting a light beam along an optical axis; an optical element designed as a filter element in the optical axis for imparting a specific polarization direction to the light of the light beam or to the light reflected or transmitted by the object to be examined or for filtering the light, a rotation unit designed to rotate the test object, which is located at least close to the optical axis, by a rotation angle relative to the measuring system and / or the test unit; a detector unit designed to capture light reflected or transmitted by the object to be inspected and generate an at least approximately sharp image of the light source or reticle; an evaluation unit designed to determine a characteristic value for centering from the measured drawn circle and to determine the polarization axis of the test object from the rotation angle and the change in the brightness signal of the light beam of the light bundle reflected by the test object or transmitted by the test object, which change is related to the rotation angle.

[0006] Furthermore, the approach presented herein provides an inspection apparatus for optical inspection objects, the inspection apparatus having the following features: a light source for emitting a light beam along an optical axis; an optical element for collimating the emitted light bundle; an optical element designed as a polarization-influencing element for imparting a specific polarization direction to the light of a bundle of rays, an element for holding an optical inspection object; an optical element for recollimating the bundle of rays focused by the object to be examined; an optical element for filtering the light transmitted by the object to be examined, the optical element being designed as a polarizing filter; an optical element for refocusing the light transmitted by the test object onto the detection surface; a rotation unit designed to rotate the inspection object located in the optical axis relative to the inspection device and / or the individual components of the inspection device about the beam axis and / or the optical axis; a detector unit designed to simultaneously determine the polarization axis of the test object and the decentering of the test object from the rotation angle and from the rays of the light bundle transmitted by the test object; It is equipped with:

[0007] A light source can be understood, for example, as a light source or lamp which outputs corresponding light rays as a ray bundle along an optical axis. Alternatively, it can be an illuminated reticle. A filter element can be understood, for example, as an optical element which imparts a corresponding polarization direction to the incident light. A rotation unit can be understood, for example, as a mechanical unit which rotates the test object relative to the measuring device, such rotation can be performed by actively rotating the test object itself when the filter element is stationary, or by rotating the measuring device when the test object is stationary. For example, the rotation unit can be designed to rotate the measuring device or the test object by a certain rotation angle, for example around the optical axis or around the axis of the ray bundle, using an electric drive. A detector unit can be understood, for example, as a light sensor or projection surface, on which the light reflected by or transmitted through the test object is imaged and subsequently evaluated by a corresponding evaluation unit with respect to the position of the polarization axis of the test object.

[0008] The approach presented here is based on the knowledge that the position of the polarization axis can be evaluated very simply by rotating the test object relative to the filter element. This can be done, for example, by detecting and evaluating the change in brightness during the rotation, making use of the fact that, if the polarization axis of the test object or the surface of the test object is in the same position, the light intensity that can be received by the detector unit is maximized by setting the polarization direction imparted by the filter element to the light of the bundle of rays. In this way, it is possible to provide an inspection device for optical test objects using very simple means from a technical point of view, in which the polarization axis of the test object can be detected and at the same time a centering measurement, i.e. a measurement of the position of the optical center or the optical axis of the test object, can be performed using the same measurement structure. The approach proposed here therefore offers the advantage of simultaneously or simultaneously measuring several parameters of the test object by means of the proposed measurement structure, whereby further measurement structures can be omitted and thus structural space in the inspection device can be saved.

[0009] An embodiment of the approach proposed herein is advantageous, in which the detector unit is designed to determine the polarization axis of the test object using the brightness, brightness pattern and / or light intensity pattern of the light beams of the light beam bundle. Such an embodiment offers the advantage that the brightness and / or brightness or intensity pattern can be detected very simply from a technical point of view and thus the polarization axis of the test object can be accurately determined.

[0010] Furthermore, an embodiment of the approach proposed herein is advantageous, in which the rotation unit is designed to rotate the inspection object and / or the sensor unit around a beam axis and / or an optical axis. For example, such a beam axis can be the axis of a light ray in a light bundle. Such an embodiment offers the advantage of a compact construction of the inspection device.

[0011] According to another embodiment of the approach proposed herein, the filter element can be designed to impart a circular or linear polarization direction to the light and / or the detector unit has an analyzer designed to pass circular or linear polarization. Such an embodiment offers the advantage that the light of the light bundle is simply imparted or evaluated with a precise polarization direction by the filter element, so that recognition of the polarization direction of the examined object can be very easily implemented from a technical point of view.

[0012] Furthermore, an embodiment of the approach proposed herein is particularly advantageous, in which the polarizer and the analyzer are arranged relative to one another such that a predetermined azimuthal angle is set between the polarization direction defined by the polarizer and the polarization direction of the light passing through the analyzer defined by the analyzer. By setting a predetermined azimuthal angle, if this angle is known, the accuracy of the recognition of the polarization axis of the test object can be further improved, in addition to which the polarization axis of the birefringent optical element can also be determined.

[0013] Particularly advantageous are embodiments of the approach proposed herein, in which the detector unit is designed to perform a centering measurement of the test object. Such a centering measurement of the test object may comprise, for example, the measurement of the optical axis, the optical center, or another parameter of the test object. Such an embodiment of the approach proposed herein offers the advantage that several parameters, such as the polarization axis and the centering value of the test object, can be determined with one measurement structure, whereby the required construction space of the inspection device is very small, while the measurements can be performed without laboriously transferring the test object to different instruments or without different measurements on one instrument.

[0014] Furthermore, according to one embodiment of the approach presented herein, the detector unit can be designed to measure the diameter and / or radius of the detected drawn circle as a measure for the centration measurement. Such a diameter or radius detection makes the centration measurement very simple and fast to perform from a technical point of view.

[0015] Embodiments of the approach proposed herein, in which the detector unit is designed to perform the determination of the polarization axis and the centering measurement in parallel and / or simultaneously, and in which the brightness variation is detected in addition to the radius and / or diameter in the circular image, work particularly efficiently, making it possible to provide an inspection device that requires less construction space and is easy to handle during operation.

[0016] According to another embodiment of the approach proposed herein, the radiation source and detector unit can also be integrated into an autocollimator together with a polarizing filter element in the optical axis, a beam splitter being provided for extracting the light reflected by the inspection object from a light path parallel to the light emitted by the radiation source, such an embodiment offering the advantage of a very compact construction form of the inspection device.

[0017] According to another embodiment, an additional rotation of the polarizing element in the measurement system can be performed relative to the measurement system. This can be done mechanically or optically. The optical rotation of the polarizing element can be realized, for example, via a liquid crystal or LCD element. In that case, the polarization axis is rotated by applying a voltage.

[0018] This is particularly advantageous in the embodiment in which the rotation of the polarizing element is performed by a physical rotation of 1.25 times. Thus, in a physical rotation of 360 degrees, the polarizing element rotates by another 90°. In a subsequent second rotation, the additional rotation of the polarizing element increases to 180°, which optically corresponds to the initial configuration. Thus, for each point of the double drawn circle, two intensity values ​​are obtained, which are associated with mutually perpendicular polarization directions, resulting in a correspondingly different or inverted intensity profile. Thereby, additionally high signal intensities are obtained in areas of the drawn circle where only very low signal intensities are present in other embodiments. This complementary intensity profile allows the "complete" drawn circle to be used by adding the images to measure the eccentricity. Alternatively, this advantageous signal reception can also be achieved in that the measurement system and the polarizing element are mechanically movable relative to each other and rotate at different speeds.

[0019] According to another embodiment of the approach proposed herein, a collimator preceded by a polarizer can be used as a filter element, and a telescope with an analyzer can be provided in the optical path between the auxiliary optics and / or the decollimating lens.

[0020] An embodiment of the approach proposed herein is further advantageous as a method for inspecting an optical inspection object, which is carried out using a variant of the inspection device presented herein and comprises the following steps: - outputting a light beam from a radiation source through a filter element towards an object to be examined, and receiving in a detector unit the light beam reflected or transmitted by the object to be examined, - performing a relative rotational movement between the test object and the measuring device; - determining the polarization axis of the test object from the light reflected or transmitted by the test object; Includes.

[0021] The advantages discussed above can also be achieved quickly and efficiently with such an embodiment.

[0022] In another embodiment of the method, the rotational movement of the centration measurement unit is performed at a different rotational speed than the rotational movement of the polarizing element or deflection elements.

[0023] The approach presented herein further provides a control device designed to execute, control or implement the steps of the method variants presented herein in a corresponding device. This embodiment variant of the invention in the form of a control device also allows the problem on which the invention is based to be solved quickly and efficiently.

[0024] For this purpose, the evaluation device can have at least one calculation unit for processing signals or data, at least one storage unit for storing signals or data, at least one interface to sensors or actuators for reading sensor signals from sensors or for outputting control signals to actuators, and / or at least one communication interface for reading or outputting data embedded in a communication protocol. The calculation unit can be, for example, a signal processor, a microcontroller, etc., and the storage unit can be a flash memory or a magnetic storage unit. The communication interface can be configured for wireless and / or wired data reading or output, in which case a communication interface capable of wired data reading or output can read the data, for example electrically or optically, from a corresponding data transmission line or output the data to a corresponding data transmission line.

[0025] A control device unit here can be understood as an electrical device that processes sensor signals and outputs control and / or data signals accordingly. The control device can have an interface that can be formed by hardware and / or software. If formed by hardware, the interface can be, for example, part of a so-called system ASIC, which includes many functions of the control device. However, the interface can also be a dedicated integrated circuit or can at least partly consist of discrete components. If formed by software, the interface can be, for example, a software module present in a microcontroller together with other software modules.

[0026] Also advantageous is a computer program product or computer program which 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 which comprises a program code used to execute, perform and / or control the steps of the method according to one of the aforementioned embodiments, in particular when the program product or program is executed on a computer or device. [Brief description of the drawings]

[0027] In the following, advantageous exemplary embodiments of the approach presented herein are described in detail with reference to the accompanying figures.

[0028] [Figure 1] 1 shows a schematic diagram of an exemplary embodiment of an inspection apparatus for inspecting an optical inspection object; [Diagram 2] 2 shows a schematic diagram of an image of light reflected by a test object towards a sensor in a corresponding arrangement according to FIG. 1; [Diagram 3] 1 shows a schematic diagram of the signal profile of the detected light intensity without and with an additional rotation of the polarizing element. [Figure 4] 1 shows a schematic diagram of an exemplary embodiment of an inspection apparatus for inspecting an optical inspection object in transmission; [Diagram 5] 1 shows a flow chart of an exemplary embodiment of a method.

[0029] In the following figures, identical or similar elements are labeled with identical or similar reference numerals, and repeated description of these elements is omitted for clarity.

[0030] FIG. 1 shows a schematic diagram of an exemplary embodiment of an inspection device 100 for inspecting an optical inspection object 105. In this case, a light beam 115 is deflected in a beam splitter 120 along an optical axis 117 in the form of a bundle of rays from a light beam source 145, after which the light beam 115 is incident on a filter element 125. The light beam source can be advantageously combined with a crosshair (reticle). In this case, the filter element 125 can be designed as a polarizer or analyzer, which can impart a certain polarization direction to the light of the light beam 115 or pass light reflected by the inspection object 105 only with a certain polarization direction. Furthermore, a collimating and focusing unit 130 can be provided, which is arranged, for example, on the optical axis 117 and can focus the light 115 on the optical inspection object 105. The collimating and focusing unit 130 can then be arranged, for example, in two subunits 130a and 130b, which are respectively in front of or behind the filter element 125 in the light beam direction. In that case, the optical element 130a is called a collimating lens and the optical element 130b is called a focusing lens or a front lens. Furthermore, a rotation unit 135 is provided, which is designed, for example, as an electric drive for rotating the test object 105 through a rotation angle 140. In FIG. 1, this rotation is shown as the rotation unit 135 rotating the test object 105 or a holder of the test object 105, which is not shown in FIG. 1. Alternatively or additionally, the rotation unit 135 can also be designed to rotate the entire measurement system 100 through the rotation angle 140. The rotation unit is controlled via a control unit 165.

[0031] The light of the beam 115 is then reflected by the object under inspection 105, or more precisely by its surface, resulting in a polarization effect, in particular in that light of high intensity incident with the same polarization direction as is most strongly reflected by the surface of the object under inspection 105 is reflected. This reflected light then passes through the beam splitter 120 and is received by the sensor 110 of the detector unit 147. The detector unit 147 can be integrated in the sensor 110 or connected to the sensor via a suitable wired or wireless interface as part of the control device 150. To obtain an image of the center of curvature of the surface of the optical inspection object 105 from the reflected light, the sensor 110 can be designed, for example, as a CMOS or CCD camera or a projection screen towards which the camera is directed.

[0032] In that case, the control device 150 can be used to operate the device 100. In that case, the output of light by the light source 145 can be controlled by the output unit 155. With the controlled output of light, the reflected light or a corresponding signal obtained correspondingly at the sensor 110 can then be read by the reading interface 160. Then, for example, if the rotation of the test object 105 is controlled by a corresponding rotation angle 140, from here, the position of the polarization axis of the test object 105 can be determined by means of the determination unit 170 from the light reflected by the test object 105 together with the imaging obtained by the sensor 110.

[0033] At the same time, it is also possible to perform centering measurements using the structure shown in FIG. 1, which is possible simply by further evaluating the image of light reflected by the test object 105 detected by the sensor 110.

[0034] FIG. 2 shows a schematic diagram of an image 200 of light reflected by the test object 105 towards the sensor 110. The illustration in FIG. 2 then shows light reflected or incident towards the sensor 110, which forms a corresponding light pattern 210 or intensity pattern. It can be seen that the reflected light then produces an image of the test object or an object (in the example a cross) which forms a drawn circle 220 due to the rotation of the autocollimator. From the radius R of the drawn circle the eccentricity of the test object 105 can be deduced. Depending on the rotational position of the test object relative to the filter element 125 and the polarization influence properties of the test object, the (light) signal intensity changes within the rotational movement. If the filter element 125 or the test object 105 is rotated 360° and all camera images are integrated, instead of a circle with constant intensity, a sinusoidal intensity distribution which changes with the azimuth angle is obtained. In FIG. 2 this change is shown by the intensity profile. The rotation angle at which the intensity is maximum can be understood as the angle at which the polarization axis of the test object 105 is aligned. Thus, the brightness variation over the rotation angle contains information about the alignment of the polarization axis of the test object 105, whereas the diameter or radius R of the drawn circle 220 is a measure of the centration of the test object 105. The rotational movement of the test object 105 is therefore utilized to sense both measurands, which are advantageously measured in parallel.

[0035] Figure 3 shows a schematic diagram of the signal profile of the detected light intensity without and with an additional rotation of the polarizing element. In this case, the normalized intensity is plotted on the ordinate against the angle on the abscissa. The solid sinusoids show the detected signal profile when the test object is rotated at a constant rotation speed relative to the measurement system without additional rotation of the polarizer / analyzer. When measuring in reflection, this can be achieved by rotating the ACM or by rotating the test object. The dashed or dotted sinusoids are created when the polarizer / analyzer is rotated mechanically or optically at high speed relative to the measurement system. A first signal (dashed) and a second inverted signal (dotted) are thereby detected for each azimuthal position. The sum of the signal profiles results in a fully illuminated drawn circle.

[0036] Thus, if the dashed and dotted intensity profiles are added together, a "perfect" drawn circle can be obtained, as shown in the lower part of FIG.

[0037] Therefore, advantageously, the centering measurement and the polarization measurement can be associated in one measurement process, thereby keeping the construction space compact and also minimizing the measurement time. To achieve this, according to an exemplary embodiment, the centering measurement, in which a rotation of the test object is performed, is associated with the polarization light path. The approach presented herein therefore allows an advantageous association of the centering measurement and the polarization measurement, which allows for a compact measurement construction and short measurement times.

[0038] Depending on the characteristics of the object to be inspected, the filter element 125 or the polarizer and / or analyzer can be designed for circular polarization instead of linear polarization, or an azimuthal angle can be set between the polarizer and the (separate) analyzer.

[0039] Another technical embodiment of the variant of the inspection device presented in this specification is, for example: A telescope with a collimator and analyzer preceded by a polarizer in the optical path between the fore-optics and the "decollimating lens". The centration is measured in transmission.

[0040] FIG. 4 shows a schematic diagram of an exemplary embodiment of an inspection device 100 for inspecting an optical inspection object 105 in transmission, where a simultaneous measurement of the decentering and the polarization change characteristics of the optical element is measured in transmission. Again, the decentering is detected based on the radius or diameter of the drawn circle created by the rotation of the inspection object relative to the measurement system. To determine the polarization change characteristics of the inspection object 105, the collimator 400 is provided with a polarizing element, e.g., a polarizer 125, and the telescope 420 is provided with a polarizing filter element, e.g., an analyzer 410, which has a prelens 430 and a focusing lens or "decollimating lens" that is not explicitly shown in FIG. 4. The polarizer 125 in the collimator 400 is illuminated, e.g., through an illuminated focusing plate 435. As shown in FIG. 3 and described above, the polarizing element can itself be optically or mechanically rotated relative to the measurement system, e.g., to obtain a complementary signal profile. The polarizer 125 and the analyzer 410 can be rotated independently of each other or an additional quarter-wave plate can be rotated instead, which is advantageous, for example, when determining the Mueller matrix of the test object. Furthermore, the polarizer 125 and the analyzer 410 can have different optical properties. The polarizer 125 can be designed, for example, as a retardation plate or can be combined or connected with a retardation plate, so that the light beam after the collimator 400 has a circular polarization. The light beam is further focused in front of the prelens 430 or the analyzer 410 to the test object focal point 440. Such a variant is advantageous, for example, when the test object 105 changes the polarization of the light beam, for example from circular to linear, which is the case, for example, in pancake optics for AR / VR. For such test objects 105, it is therefore particularly advantageous to perform the measurement in transmission.

[0041] 5 shows a flow chart of an exemplary embodiment of a method 500 for inspecting an optical inspection object, which is performed using an inspection apparatus according to the variant introduced herein and includes outputting a light beam from a light source through a filter element to the inspection object and receiving the light beam reflected or transmitted by the inspection object at a detector unit 510. The method 500 further includes rotating the inspection object relative to the filter element 520 and determining a polarization axis of the inspection object from the light reflected or transmitted by the inspection object 530.

Claims

1. An inspection device (100) for an optical inspection object (105), said inspection device (100) having the following features: a light source (145) for emitting a light beam (115) along an optical axis (117); an optical element (125) designed as a polarization influencing or polarization filtering element in said optical axis (117) for imparting a specific polarization direction to the light of said bundle of rays (115) and for filtering the light reflected by said object to be examined (105); a rotation unit (135) designed to rotate the inspection object (105), which is located on the optical axis (117), relative to the inspection device and / or individual components of the inspection device about the beam axis and / or the optical axis (117); a detector unit (147) designed to simultaneously determine the polarization axis of the test object (105) and the decentering of the test object from the rotation angle (140) and from the rays of the bundle of rays (115) reflected by the test object (105), An inspection device comprising:

2. An inspection device (100) for an optical inspection object (105), said inspection device (100) having the following features: a light source (145) for emitting a light beam (115) along an optical axis (117); an optical element for collimating said emitted light bundle; an optical element designed as a polarization-influencing element for imparting a specific polarization direction to the light of said bundle of rays (115); an element for holding said optical inspection object, an optical element for recollimating the bundle of rays focused by the object under examination; an optical element for filtering the light transmitted by the object under examination (105), designed as a polarizing filtering element; - an optical element for refocusing the light transmitted by the test object onto a detection surface; a rotation unit (135) designed to rotate the inspection object (105), which is located on the optical axis (117), about the beam axis and / or the optical axis (117) relative to the inspection device and / or individual components of the inspection device; a detector unit (147) designed to simultaneously determine the polarization axis of the test object (105) and the decentering of the test object from the rotation angle (140) and from the rays of the bundle of rays (115) transmitted by the test object (105), An inspection device comprising:

3. 3. Inspection device (100) according to claim 1 or 2, characterized in that the polarization influencing element is mechanically and / or optically rotatable in the optical path.

4. 3. The inspection apparatus (100) of claim 1 or 2, wherein the detector unit (147) is designed to determine the polarization axis of the object to be inspected (105) using the brightness, brightness pattern and / or light intensity pattern (210) of the reflected or transmitted light rays of the light bundle (115).

5. The inspection device (100) according to any one of claims 1 to 4, characterized in that the polarizer (125) is designed to impart a circular or linear polarization direction to the light and the detector unit (147) has an analyzer designed to pass circularly or linearly polarized light.

6. The inspection device (100) of claim 5, characterized in that the polarizer (125) and the analyzer are arranged relative to each other such that a predetermined azimuth angle is set between the polarization direction defined by the polarizer (125) and the polarization direction of light passing through the analyzer defined by the analyzer.

7. Inspection device (100) according to any one of claims 1 to 6, characterized in that the detector unit (147) is designed to detect the degree of decentering from a contour (220) of the detected brightness variation.

8. The inspection device (100) according to any one of claims 1 to 7, characterized in that the light source (145) and the sensor (110) are integrated in an autocollimator together with the polarizer (125) and / or analyzer on the optical axis (117), and a beam splitter (120) is provided for extracting the light reflected by the object to be inspected (105) from an optical path parallel to the light irradiated by the light source (145).

9. A method (500) for inspecting an optical inspection object (105), said method (500) being carried out using an inspection device (100) according to any one of claims 1 to 8, comprising the following steps: - outputting (510) a bundle of light rays (115) from a light source (145) towards the test object (105), where the bundle of light rays is first polarized, and receiving in a detection unit (147) the light of the bundle of light rays (115) reflected by or transmitted through the test object (105); - rotating (520) said test object (105) relative to said test device (100) and / or individual components of said test device; - determining (530) simultaneously the polarization axis of the test object (105) and the decentering of the test object from the light reflected or transmitted by the test object (105); The method includes:

10. 10. The method (500) of claim 9, further comprising: rotating a polarization influencing element relative to the inspection device; and detecting, for each azimuthal position of the inspection object over the course of at least two rotations, a first intensity signal and a second intensity signal different from the first intensity signal.

11. 11. The method (500) of claim 10, wherein the first intensity signal and the second intensity signal are added to obtain a drawn circle having an intensity variation within a tolerance range to measure the eccentricity.

12. A control device (150), configured to execute and / or control the steps (510, 520, 530) of the method (500) of any one of claims 1 to 11 in corresponding units (155, 160, 170).

13. A computer program configured to perform and / or control the steps (510, 520, 530) of the method (500) of claim 11.

14. A machine-readable storage medium having stored thereon the computer program of claim 13.

Images