Testing device for an optical test object and method for testing an optical test object
Patent Information
- Authority / Receiving Office
- FI · FI
- Patent Type
- Patents
- Current Assignee / Owner
- TRIOPTICS GMBH
- Filing Date
- 2024-08-20
- Publication Date
- 2026-07-09
Abstract
Description
[0001] The approach presented here provides a testing device for an optical test specimen and a method for testing an optical test specimen according to the main claims.
[0002] Some lenses have polarization-influencing properties, either because they generate their refractive power (liquid crystal lenses) or because they are coated accordingly (polarizing layers, lambda / 4 layers, etc.). When installing such lenses, both their centering and the alignment of the polarization axis are important. However, this often requires multiple work steps to measure both the centering and the alignment of the polarization axis. Carrying out this multiple work steps requires additional effort in terms of the design of the test fixture in order to measure both the centering and the alignment of the polarization axis in different work steps. At the same time, such a test fixture requires more space. This would require a sequential measurement of centering and polarization using two different measuring heads.Accordingly, the measurement technology requires a lot of space and the two separate individual measurements lead to long measurement times.
[0003] Against this background, the object of the present invention is to provide an improved testing device for an optical test specimen and an improved method for testing an optical test specimen.
[0004] This problem is solved by the subject matter of the main claims.
[0005] The approach presented here creates a test fixture for an optical test piece for determining decentration and polarization properties of the test piece, wherein the test fixture has the following features: a beam source for emitting a beam of rays along an optical axis; an optical element configured as a filter element in the optical axis for impressing or filtering a specific polarization direction of the light of the beam of rays or of light reflected or transmitted by the test object; a rotation unit configured to rotate the test object, which is located at least near the optical axis, by a rotation angle relative to a measuring system and / or the test unit; a detector unit configured to capture the light reflected or transmitted by the test object and to generate an at least approximately sharp image of the light source or the reticle;and an evaluation unit designed to determine a characteristic value for the centering from the measured impact circle, as well as to determine a polarization axis of the test object from the angle of rotation and the associated variation in the signal brightness of the light beam of the beam reflected by the test object or transmitted through the test object. ;
[0006] Furthermore, the approach presented here creates a test device for an optical test object, wherein the test device comprises the following features: a beam source for emitting a beam of rays along an optical axis; an optical element for collimating the emitted beam of rays; a polarization-influencing optical element for imprinting a specific polarization direction of the light of the beam of rays; an element for holding the optical test object; an optical element for recollimating the beam of rays focused by the test object; a polarization-filtering optical element for filtering light transmitted by the test object; an optical element for refocusing the light transmitted by the test object onto a detection plane; a rotation unit designed to rotate the test object lying in the optical axis relative to the test device and / or individual assemblies thereof about a beam axis and / or the optical axis;and a detector unit configured to simultaneously determine a polarization axis of the test object and its decentration from the rotation angle and a light beam of the beam transmitted by the test object.
[0007] A beam source can be understood, for example, as a light source or lamp that emits corresponding light rays as a bundle of rays along the optical axis. Alternatively, this can also be an illuminated reticle. A filter element can be understood, for example, as an optical element that imparts a corresponding polarization direction to an incident light. A rotation unit can be understood, for example, as a mechanical unit that rotates the test object relative to the measuring device. This can be achieved either by actively rotating the test object itself with the filter element at rest or by rotating the measuring device with the test object at rest.For example, the rotation unit can be configured to rotate the measuring device or the test object by a specific rotation angle, for example, about the optical axis or about an axis of the beam, using an electric drive. A detection unit can be understood, for example, as an optical sensor or a projection surface onto which light reflected from the test object or light transmitted through the test object is projected and subsequently evaluated by a corresponding evaluation unit with regard to the position of the test object's polarization axis.
[0008] The approach presented here is based on the realization that the position of the polarization axis can be very easily evaluated by rotating the test object in relation to the filter element. This can be achieved, for example, by recording and evaluating a brightness variation during the rotation. This takes advantage of the fact that when the position of the polarization axis of the test object or of a surface of the test object is the same, with the set polarization direction that is impressed on the light of the beam by the filter element, the light intensity that can be received by the detector unit is the greatest. In this way, using very simple technical means, a test device for the optical test object can be created which has the option of recording the polarization axis of the test object and, at the same time, with the same measuring setup, also has the option of carrying out a centering measurement, i.e. a measurement of the optical center orthe position of the optical axis of the test object. The approach proposed here thus offers the advantage of measuring several parameters of the test object simultaneously using the proposed measurement setup, eliminating the need for an additional measurement setup and thus saving space in the test fixture.
[0009] A favorable embodiment of the approach proposed here is one in which the detector unit is designed to determine the polarization axis of the test object using a brightness, a brightness pattern, and / or light intensity pattern of the light beam of the beam. Such an embodiment offers the advantage of being able to very easily detect the brightness and / or brightness pattern reference or the intensity pattern, thus enabling the polarization axis of the test object to be determined precisely.
[0010] Another advantageous embodiment of the approach proposed here is one in which the rotation unit is designed to rotate the test object and / or the sensor unit about a beam axis and / or the optical axis. For example, such a beam axis can be an axis of a light beam in the beam bundle. Such an embodiment offers the advantage of a compact design of the test device.
[0011] According to another embodiment of the approach proposed here, a filter element can be configured to impart a circular or linear polarization direction to the light, and / or the detector unit can have an analyzer configured to allow circularly or linearly polarized light to pass through. Such an embodiment offers the advantage of easily imparting or evaluating a very precise polarization direction to the light of the beam using the filter element, so that the detection of the polarization direction of the test object can be implemented in a technically simple manner.
[0012] A particularly advantageous embodiment of the approach proposed here is one in which the polarization element and the analyzer are arranged relative to one another in such a way that a predefined azimuthal angle is set between the polarization direction defined by the shaping element and a polarization direction of the light passing through the analyzer, defined by the analyzer. By setting the predefined azimuthal angle, with knowledge of this angle, a further improvement in the precision of detecting the polarization axis of the test object can be achieved, and the polarization axis of a birefringent optical element can also be determined.
[0013] A particularly advantageous embodiment of the approach proposed here is one in which the detection unit is designed to perform a centering measurement of the test object. Such a centering measurement of the test object can, for example, comprise a measurement of the optical axis, the optical center, or another parameter of the test object. Such an embodiment of the approach proposed here offers the advantage of being able to determine several parameters, such as the polarization axis of the test object and a centering value, with one measurement setup. This means that only a very small installation space is required for the test device. Furthermore, a measurement can be performed without the laborious switching of the test object to different devices or different measurements on one device.
[0014] Furthermore, according to one embodiment of the approach presented here, the detection unit can be configured to use a diameter and / or a radius of a detected impact circle as a measure for the centering measurement. By detecting such a diameter or radius, the centering measurement can be implemented or executed very easily and quickly.
[0015] A particularly efficient embodiment of the approach proposed here is one in which the detection unit is designed to determine the polarization axis and the centering measurement in parallel and / or simultaneously, with a brightness variation being recorded in the impact circle image in addition to the radius and / or diameter. Such an embodiment makes it possible to create testing devices that require only a small amount of installation space and are easy to handle during operation.
[0016] According to a further embodiment of the approach proposed here, the radiation source and the detector unit can be installed in an autocollimator together with the polarizing filter element in the optical axis, with a beam splitter provided to decouple light reflected by the test object from a beam path parallel to the light radiated by the radiation source. Such an embodiment offers the advantage of a very compact design of the test device.
[0017] According to a further embodiment, an additional rotation of the polarization element in the measuring system relative to the measuring system can be performed. This can be done either mechanically or optically. Optical rotation of the polarization element can be realized, for example, via a liquid crystal or LCD element. The polarization axis is rotated by applying a voltage.
[0018] A particularly advantageous embodiment results in an embodiment in which the rotation of the polarization element occurs with 1.25 times the physical rotation. With a physical rotation of 360 degrees, an additional rotation of the polarization element of 90° is obtained. In a subsequent second rotation, the additional rotation of the polarizing element increases to 180°, which optically corresponds to the starting configuration. Therefore, for each point of the double beating circle, two intensity values are obtained. These values are linked to mutually perpendicular polarization directions and result in correspondingly different or inverted intensity curves. This also results in an additional high signal intensity in areas of the beating circle where, in other embodiments, only a very low signal intensity is present.This complementary intensity profile allows a "complete" beat circle to be used for measuring decentration by adding the images. Alternatively, this advantageous signal reception can also be achieved by mechanically moving the measuring system and the polarization element relative to each other and rotating at different speeds.
[0019] According to a further embodiment of the approach proposed here, a collimator with a polarizer attached in front can be used as a filter element and a telescope with an analyzer can be provided in the beam path between an auxiliary optics and / or a decollimation lens.
[0020] Furthermore, an embodiment of the approach proposed here is advantageous as a method for testing an optical test object, wherein the method is carried out using a variant of a test device presented here and comprises the following steps: Emitting light of a beam from the radiation source through the filter element onto the test object and receiving light of the beam reflected or transmitted by the test object in the detector unit; performing a relative rotational movement between the test object and the measuring device; and determining the polarization axis of the test object from the light reflected or transmitted by the test object.
[0021] Such an embodiment also allows the above-mentioned advantages to be realized quickly and efficiently.
[0022] In a further embodiment of the method, the rotational movement of the centering measuring unit is carried out at a different rotational speed than the rotational movement of the polarizing element(s).
[0023] The approach presented here further provides a control unit configured to perform, control, or implement the steps of a variant of a method presented here in corresponding devices. This embodiment of the invention in the form of a control unit also allows the problem underlying the invention to be solved quickly and efficiently.
[0024] For this purpose, the control unit can have at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, at least one interface to a sensor or an actuator for reading sensor signals from the sensor or for outputting control signals to the actuator, and / or at least one communication interface for reading or outputting data embedded in a communication protocol. The computing unit can be, for example, a signal processor, a microcontroller, or the like, wherein the memory unit can be a flash memory or a magnetic storage unit.The communication interface can be designed to read in or output data wirelessly and / or wired, wherein a communication interface that can read in or output wired data can read this data, for example, electrically or optically from a corresponding data transmission line or output it to a corresponding data transmission line.
[0025] In this context, a control unit can be understood as an electrical device that processes sensor signals and outputs control and / or data signals depending on them. The control unit can have an interface that can be implemented in hardware and / or software. In a hardware implementation, the interfaces can, for example, be part of a so-called system ASIC, which contains a wide variety of functions of the control unit. However, it is also possible for the interfaces to be separate integrated circuits or to consist at least partially of discrete components. In a software implementation, the interfaces can be software modules that are present, for example, on a microcontroller alongside other software modules.
[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 when the program product or program is executed on a computer or a device.
[0027] Favorable implementation examples of the approach presented here are explained in more detail below with reference to the attached figures. They show: Fig. 1 a schematic representation of an embodiment of a testing device for testing an optical test object; Fig. 2 a schematic representation of the image of the arrangement corresponding to the test specimen Figure 1 reflected light onto the sensor; Fig. 3 a schematic representation of signal curves of a detected light intensity without and with additional rotation of a polarization element; Fig. 4 a schematic representation of an embodiment of a test device for testing an optical test object in transmission; and Fig. 5 a flowchart of an embodiment of a method
[0028] Identical or similar elements are provided with identical or similar reference symbols in the following figures, whereby a repeated description of these elements is omitted for reasons of clarity.
[0029] Figure 1shows a schematic representation of an embodiment of a testing device 100 for testing an optical test object 105. A light beam 115 is deflected from a beam source 145 along an optical axis 117 in the form of a beam bundle at a beam splitter 120, after which the light beam 115 is incident on a filter element 125. The beam source can advantageously be combined with a reticle. The filter element 125 can be designed as a polarizer or analyzer and can impart a specific polarization direction to the light of the light beam 115 or allow light reflected from the test object 105 to pass only with a specific polarization direction. Furthermore, a collimation and focusing unit 130 can be provided, for example, which is arranged along the optical axis 117 and can focus the light 115 onto the optical test object 105.The collimation and focusing unit 130 can, for example, be arranged in two subunits 130a and 130b, each arranged in the beam direction before or after the filter element 125. The optical element 130a is referred to as the collimation lens, and the optical element 130b as the focusing lens or auxiliary 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 the . Fig. 1 This rotation is shown in such a way that the rotation unit 135 rotates the test object 105 or a Fig. 1 not shown, rotates the holder of the test specimen 105. Alternatively or additionally, the rotation unit 135 can also be designed to rotate the entire measuring system 100 by the rotation angle 140. The rotation unit is controlled via a control unit 165.
[0030] The light of light beam 115 is now reflected from the test object 105, or more precisely from its surface, resulting in a polarizing effect in which the light incident in the same polarization direction as that most strongly reflected by the surface of the test object 105 is reflected with high intensity. This reflected light then passes through the beam splitter uo and is received by a sensor 110 of a detector unit 147. The detector unit 147 can be integrated together with the sensor 110 or connected to a control unit 150 via a suitable wired or wireless interface as part of the control unit 150. The sensor 110 can be designed, for example, as a CMOS or CCD camera or a projection screen with a camera directed thereto in order to obtain an image of the center of curvature of a surface of the optical test object 105 from the reflected light.
[0031] The device 100 can now be operated using a control unit 150. The output of light by the beam source 145 can be controlled by means of an output unit 155. The reflected light or a corresponding signal obtained by the controlled output of the light at the sensor 110 can then be read in via a read-in interface 160. If, for example, a rotation of the test object 105 by a corresponding rotation angle 140 is controlled, the position of the polarization axis of the test object 105 can be determined from the light reflected by the test object 105 using a determination unit 170, together with the image obtained from the sensor 110.
[0032] At the same time, it is also possible to use the Figure 1to carry out a centering measurement using the setup shown, which can only be made possible by further evaluation of the image of the light reflected from the test object 105 captured by the sensor 110.
[0033] Fig. 2 shows a schematic representation of the image 200 of the light reflected from the test object 105 onto the sensor 110. The representation from the Figure 2shows a light reflected or incident on the sensor 110, which forms a corresponding light pattern 210 or intensity pattern. Here, it can be seen that the reflected light creates an image of an object (in the specific example, a cross), which forms a beating circle 220 due to the rotation of the test object or the autocollimator. From the radius R of the beating circle, a decentration of the test object 105 can be inferred. Depending on the rotational position of the test object and its polarization-influencing properties in relation to the filter element 125, the (light) signal intensity varies within the rotational movement. If all camera images are integrated over a 360° rotation of the filter element 125 or the test object 105, one obtains a sinusoidal intensity distribution that varies with the azimuth angle instead of a circle with constant brightness. In the Figure 2This variation is indicated by the intensity curve. The rotation angle for which the brightness is maximum can be understood as the angle at which the polarization axis of the test object 105 is aligned. The brightness variation over the rotation angle thus contains information about the alignment of the polarization axis of the test object 105, while the diameter or radius R of the striking circle 220 represents a measure of the centering of the test object 105. The rotational movement of the test object 105 is therefore used to determine both measured variables, which are advantageously measured in parallel.
[0034] Fig. 3shows a schematic representation of signal curves of a detected light intensity with and without additional rotation of a polarization element. Here, a normalized intensity is plotted on the ordinate versus an angle on the abscissa. The solid sine curve describes the detected signal curve when the test object is rotated at a constant rotational speed relative to the measuring system, without any additional rotation of the polarizer / analyzer. For a reflection measurement, this can be achieved by rotating the ACM or rotating the test object. The dashed or dotted sine curve is created by mechanical or optical rotation of the polarizer / analyzer relative to the measuring system at increased speed. This means that for each azimuthal angular position, a first signal (dashed line) and a second, inverted signal (dotted line) are recorded.By adding the signal curves, you get a completely illuminated impact circle.
[0035] Thus, a "complete" beat circle can be obtained by adding the dashed and dotted intensity curves, as shown in the lower part of the Fig. 3 is shown.
[0036] This advantageously allows the centering measurement to be combined with a polarization measurement in a single measurement process. This keeps the installation space compact and minimizes the measurement time. To achieve this, according to one exemplary embodiment, the centering measurement, which involves rotating the test specimen, is combined with a polarizing beam path. The approach presented here thus enables an advantageous combination of centering measurement and polarization measurement, enabling a compact measurement setup and short measurement times.
[0037] Depending on the properties of the test object, the filter element 125 or the polarizer and / or the analyzer can be designed for circularly polarized light instead of linearly polarized light, or an azimuthal angle can be set between the polarizer and (a separate) analyzer.
[0038] Other technical versions of the test device presented here would include, for example, a collimator with a polarizer attached to it and a telescope with an analyzer in the beam path between the lens attachment and the "decollimation lens." Centration is measured in transmission.
[0039] Fig. 4shows a schematic representation of an embodiment of a testing device 100 for testing an optical test piece 105 in transmission, in which the simultaneous measurement of a decentration and a polarization-changing property of an optical element is measured in transmission. The decentration is also determined here based on the radius or diameter of a beating circle, which is created by rotating the test piece relative to the measuring system. To determine the polarization-changing properties of the test piece 105, a polarizing element, e.g. a polarizer 125, is provided in the collimator 400, as well as a polarization-filtering element, e.g. an analyzer 410, in the telescope 420, which has an auxiliary lens 430 and a Fig. 4not explicitly shown focusing lens or a "decollimation lens". The polarizer 125 in the collimator 400 is illuminated, for example, by an illuminated reticle 435. The polarizing elements can in turn be rotated, optically or mechanically, relative to the measuring system in order to achieve a complementary signal curve, such as in the Fig. 3shown and described above. The polarizer 125 and analyzer 410 can be rotated independently of one another, or an additional quarter-wave plate can be rotated instead, which is advantageous, for example, in determining the Müller matrix of the test object. Furthermore, the polarizer 125 and the analyzer 410 can have different optical properties. For example, the polarizer 125 can be designed as a retardation plate or combined or connected with one, so that the light rays behind the collimator 400 have circular polarization. The light rays are further focused in front of the auxiliary lens 430 or the analyzer 410 at a test object focal point 440. Such a variant is advantageous, for example, when the test object 105 changes the polarization of the light rays, for example from circular to linear, which is the case, for example, with pancake optics for AR / VR applications.For such test specimens 105, carrying out the measurement in transmission is therefore particularly advantageous.
[0040] Fig. 5 shows a flowchart of an embodiment of a method 500 for testing an optical test object, wherein the method 500 is carried out using a testing device according to a variant presented here and includes a step 510 of emitting light of a beam from the beam source through the filter element onto the test object and receiving light of the beam reflected or transmitted by the test object in the detector unit. Furthermore, the method 500 includes a step 520 of rotating the test object relative to the filter element and a step 530 of determining the polarization axis of the test object from the light reflected or transmitted by the test object.
Claims
1. Test device (100) for an optical test object (105), the test device (100) having the following features: - a beam source (145) for emitting a beam of rays (115) along an optical axis (117); - a polarization-influencing or polarization-influencing element arranged in the optical axis (117).polarization-filtering optical element (125) for imprinting a specific polarization direction of the light of the beam (115) and for filtering light reflected by the test object (105); - a rotation unit (135) which is designed to rotate the test object (105) lying in the optical axis (117) relative to the test device and / or individual assemblies thereof about a beam axis and / or the optical axis (117); and - a detector unit (147) which is designed to simultaneously determine a polarization axis of the test object (105) and its decentration from a rotation angle (140) and a light beam of the beam (115) reflected by the test object (105).
2. Test device (100) for an optical test object (105), the test device (100) comprising the following features: - a beam source (145) for emitting a beam (115) along an optical axis (117); - an optical element for collimating the emitted beam; - a polarization-influencing optical element for imprinting a specific polarization direction of the light of the beam (115); - an element for holding the optical test object; - an optical element for recollimating the beam focused by the test object; - a polarization-filtering optical element for filtering light transmitted by the test object (105); - an optical element for refocusing the light transmitted by the test object onto a detection plane;- a rotation unit (135) designed to rotate the test object (105) lying in the optical axis (117) relative to the test device and / or individual assemblies thereof about a beam axis and / or the optical axis (117); and - a detector unit (147) designed to simultaneously determine a polarization axis of the test object (105) and its decentration from the rotation angle (140) and a light beam of the beam bundle (115) transmitted by the test object (105); 3. Test device (100) according to claim 1 or 2, characterized in that the polarization-influencing elements in the beam path are mechanically and / or optically rotatable.
4. Test device (100) according to claim 1 or 2, characterized in thatthe detector unit (147) is designed to determine the polarization axis of the test object (105) using a brightness, a brightness pattern and / or light intensity pattern (210) of the reflected or transmitted light beam of the beam bundle (115).
5. Test device (100) according to one of the preceding claims, characterized in that the polarizer (125) is designed to impart a circular or linear polarization direction to the light, and wherein the detector unit (147) has an analyzer designed to allow circularly or linearly polarized light to pass through.
6. Test device (100) according to claim 5, characterized in thatthe polarizer (125) and the analyzer are arranged relative to one another such that a predefined azimuthal angle is set between the polarization direction defined by the polarizer (125) and a polarization direction of the light passing through the analyzer, defined by the analyzer.
7. Test device (100) according to one of the preceding claims, characterized in that the detector unit (147) is designed to determine a measure of decentration from a detected beat circle (220) of a brightness variation.
8. Test device (100) according to one of the preceding claims, characterized in thatthe beam source (145) and a sensor (110) are installed in an autocollimator together with the polarizer (125) and / or an analyzer in the optical axis (117), and wherein a beam splitter (120) is provided to decouple a light reflected by the test object (105) from a beam path parallel to the light radiated by the beam source (145).
9. A method (500) for testing an optical test object (105), wherein the method (500) is carried out using a test device (100) according to one of the preceding claims 1 to 8 and comprises the following steps: - emitting (510) light of a beam (115) from the beam source (145) onto the test object (105), wherein a polarization is first impressed on the beam, and receiving in the detector unit (147) a light of the beam (115) reflected by the test object (105) or transmitted through the test object, - rotating (520) the test object (105) relative to the test device (100) and / or individual components of the test device; and - simultaneously determining (530) the polarization axis of the test object (105) and its decentering from the light reflected or transmitted by the test object (105).
10. Method (500) according to claim 9 characterized in thatthe polarization-influencing elements are rotated relative to the test device and that for each azimuthal angular position of the test object in the course of at least two revolutions, a first intensity signal and a second intensity signal deviating therefrom are recorded.
11. Method (500) according to claim 10, characterized in that the first intensity signal and the second intensity signal are added to obtain a striking circle with an intensity variation within a tolerance range for measuring decentration.
12. Control device (150) which is configured to execute and / or control the steps (510, 520, 530) of the method (500) according to one of the preceding claims in corresponding units (155, 160, 170).
13. Computer program configured to execute and / or control the (510, 520, 530) of the method (500) according to claim 11.
14. Machine-readable storage medium on which the computer program according to claim 13 is stored