DE102018133289A1 - Measuring device and method for determining the minimum resolvable contrast - Google Patents

Abstract

The invention relates to a measuring device (6) for determining the minimally resolvable contrast in a predetermined irradiance of an optical direct vision, image acquisition or camera system (3) to be tested, which can be arranged in the measuring device (6), with several measuring patterns with different adjustable contrasts with the optical direct vision, image acquisition or camera system (3) and the finest measurement patterns that can still be resolved by means of the optical direct vision, image acquisition or camera system (3) are determined, comprising at least: - a digital micromirror device (1) with a large number of micromirror actuators (1a) arranged in the form of a matrix, each of which can be switched to a first stable position (S1) and a second stable position (S2); - an illumination device (7) with at least one controllable light source (2.1, 2.2) and a first illumination path (7a), which is designed for the digital micromirror device device (1) to be illuminated with the light (L1) of the at least one light source (2.1) in such a way that the micromirror actuators (1a) in the first actuating position (S1) direct the light (L1) in the direction, in particular an input optic (3a) of the optical Steer direct vision, image acquisition or camera system (3) and steer into a beam trap (5) in the second position (S2); and - an electronic control device (8) which is set up to control the digital micromirror device (1) and the lighting device (7) in such a way that the measurement patterns can be generated by switching the micromirror actuators (1a) in conjunction with their lighting.

Description

The invention relates to a measuring device and a method for determining the minimally resolvable contrast, in particular MRC (Minimum Resolvable Contrast) or MCP (Minimum Contrast Perceived), in a predetermined irradiance of an optical direct vision, image acquisition or Camera system.

The determination of the minimally resolvable contrast is used in particular to use synthetic models to determine the detection ranges of different camera systems or direct vision devices in order to make them comparable.

In the known tests, the camera system to be tested is set up in or in front of a measuring apparatus. This consists of a lighting unit and corresponding targets, measurement samples or test pattern samples (e.g. USAF 1951 Resolving Power Test Target), which are applied to a substrate and have different resolutions. A test person then observes the targets captured by the camera system on an image display device and decides which target can still be resolved. The test patterns include bar graphs with variable contrast. The bar diagram is determined in which all bars can still be resolved by the person at a predetermined frequency. The next level of contrast is then selected and the procedure repeated. In most cases, measurements have to be carried out with different lighting settings (e.g. 10,000 lux for daylight or 100 lux for twilight) in order to obtain comparability with other devices with regard to non-linear behavior and / or to simulate specified or standardized operating conditions.

The type and number of test samples to be used is limited. These are usually on a dial or the like. There is then a restriction on the number of measuring points that can be used to determine the detection ranges. As a rule, there are only five or six different contrast levels, which means that the measurement result has to be heavily interpolated and thus the informative value drops.

In addition, the production of the measurement patterns or targets, in particular in the lower contrast range, for example with single-digit percentages of the contrast, is very complex. The required accuracies can often not be met, which further limits the number of measuring points.

1. 1. Durchlichttechnik:
   • Der Messmarkenträger wird von hinten beleuchtet. Der Kontrast wird durch die Transparenz der Messmarken bestimmt. Eine Beleuchtung ist über einen breitbandigen Wellenlängenbereich zwar möglich. Jedoch sind die Messmarkenkontraste und die -auflösung nur in diskreten Stufen einstellbar. Die Messmarken zeigen außerdem einen wellenlängenabhängigen Kontrast.
2. 2. Strahlkombination:
   • Mittels eines Strahlteilers bzw. Strahlkombinierers wird ein Hintergrundsignal mit einem Messmuster, das per Durchlicht beleuchtet wird, kombiniert. Mittels zweier Lichtquellen ist ein Kontrast stufenlos steuerbar. Die Beleuchtung ist ebenfalls in einem breitbandigen Wellenlängenbereich möglich. Die Messmarkenauflösung ist allerdings nur in diskreten Stufen einstellbar. Der Strahlteiler beeinflusst nachteilig die Polarisation des Lichts. Zur Kontrastbildung ist lediglich ein additives Verfahren möglich, d. h. bei einhundertprozentigem Kontrast leuchten die Messmarken und nicht der Hintergrund.
3. 3. Selbstleuchtendes Display:
   • Auf einem LCD/LED/OLED-Display werden die Messmarken generiert bzw. dargestellt. Über eine Pulsweitenmodulierung (PWM) bzw. eine Schaltfrequenz ist ein Kontrast fast stufenlos einstellbar. Die Messmarkenauflösung kann ebenfalls fast stufenlos eingestellt werden, d. h. die möglichen Stufen werden gröber, wenn man sich mit einem Pixelpitch (direkter Abstand der Pixel auf Bildschirmen) annähert. Eine Beleuchtung ist jedoch nicht in einem breitbandigen Spektralbereich möglich, insbesondere ist das Verfahren ungeeignet für Messungen im kurzwelligen Infrarotbereich. Diesbezüglich wird auf die CN 102279092 B verwiesen.

Known test setups with test patterns with bar graphs can be divided into three variants based on the way they work when generating the measurement patterns:

1. 1. Transmitted light technology:
   • The marker carrier is illuminated from behind. The contrast is determined by the transparency of the measuring marks. Illumination is possible over a broadband wavelength range. However, the measuring mark contrasts and the resolution can only be set in discrete steps. The measuring marks also show a wavelength-dependent contrast.
2. 2. Beam combination:
   • A background signal is combined with a measurement pattern, which is illuminated by transmitted light, by means of a beam splitter or beam combiner. A contrast can be steplessly controlled by means of two light sources. Illumination is also possible in a broadband wavelength range. However, the measurement mark resolution can only be set in discrete steps. The beam splitter adversely affects the polarization of the light. Only an additive method is possible to form contrast, ie the measuring marks shine and not the background at 100% contrast.
3. 3. Self-illuminating display:
   • The measurement marks are generated or displayed on an LCD / LED / OLED display. A contrast can be set almost infinitely via pulse width modulation (PWM) or a switching frequency. The measurement mark resolution can also be set almost continuously, ie the possible levels become coarser if one approaches with a pixel pitch (direct distance of the pixels on screens). However, illumination is not possible in a broadband spectral range, in particular the method is unsuitable for measurements in the short-wave infrared range. In this regard, the CN 102279092 B referred.

It is desirable to determine the minimally resolvable contrast even in the case of image acquisition or camera systems which operate in the infrared or UV range.

In the US 4,299,451 test image patterns are generated for video sensors to be tested in order to record their minimum contrast resolution, which can be recorded by a human observer.

The EP 0 864 231 B1 relates to the testing or checking of electronic image acquisition or camera systems and in particular a method and a device for automatically performing the minimum resolvable contrast (MRC) test. A contrast measurement by means of a bar pattern is avoided and replaced by an MTF (modulation transfer function) measurement, in particular on an edge. In addition, a large number of parameters (noise-related measurement limit, video bandwidth, noise filter function, system response to sine and rectangular functions, etc.) must be measured or already known. It is therefore a very indirect process in which many error influences and tolerances play a role. For example, an MTF measurement on an edge shows a very unfavorable error propagation because of the necessary derivation of the measurement curve with subsequent Fourier transformation.

The present invention is therefore based on the object of providing a measuring device and a method of the type mentioned at the outset which avoid the disadvantages of the prior art, in particular to enable variable setting of the measurement parameters and measurements in a broadband spectral range.

This object is achieved by the features mentioned in claim 1. With regard to the method, the object is achieved by claim 16.

• - eine digitale Mikrospiegeleinrichtung mit einer Vielzahl von matrixförmig angeordneten Mikrospiegelaktoren, welche jeweils in eine erste stabile Stellposition und in eine zweite stabile Stellposition schaltbar sind;
• - eine Beleuchtungseinrichtung mit wenigstens einer regelbaren Lichtquelle und einem ersten Beleuchtungspfad, welcher dazu ausgelegt ist, die digitale Mikrospiegeleinrichtung derart mit dem Licht der wenigstens einen Lichtquelle zu beleuchten, dass die Mikrospiegelaktoren das Licht in der ersten Stellposition in Richtung, insbesondere einer Eingangsoptik des optischen Direktsicht-, Bilderfassungs- oder Kamerasystems lenken und in der zweiten Stellposition in eine Strahlfalle lenken; und
• - eine elektronische Steuerungseinrichtung, welche dazu eingerichtet ist, die digitale Mikrospiegeleinrichtung und die Beleuchtungseinrichtung derart anzusteuern, dass durch die Schaltung der Mikrospiegelaktoren in Verbindung mit deren Beleuchtung die Messmuster erzeugbar sind.

According to the invention, a measuring device is proposed for determining the minimally resolvable contrast in a predetermined irradiance of an optical direct view, image acquisition or camera system to be tested, which can be arranged in the measurement device, several measurement patterns being recorded with different adjustable contrasts with the optical direct view, image acquisition or camera system and the finest measurement patterns which can still be resolved by means of the optical direct vision, image acquisition or camera system are determined, comprising at least:

• a digital micromirror device with a multiplicity of micromirror actuators arranged in a matrix, each of which can be switched into a first stable actuating position and into a second stable actuating position;
• an illuminating device with at least one controllable light source and a first illuminating path, which is designed to illuminate the digital micromirror device with the light of the at least one light source such that the micromirror actuators direct the light in the first position in the direction, in particular an input optic, of the direct optical view - Steer, image acquisition or camera system and steer into a beam trap in the second position; and
• an electronic control device, which is set up to control the digital micromirror device and the lighting device in such a way that the measurement patterns can be generated by switching the micromirror actuators in connection with their illumination.

By using the digital micromirror device or a DLP (Digital Light Processing) actuator in connection with the at least one controllable light source, the measurement mark contrast can be variably adjusted. If only one controllable light source is used, the contrast levels in the image can be generated by means of pulse width modulation (PWM) of the individual micromirror actuators or DLP elements. A DLP actuator or DLP actuator consists of many small, independently controllable mirrors. The DLP actuator displays freely selectable measurement patterns with freely selectable line resolutions. An almost infinitely variable setting of the measurement mark resolution is thus possible. Due to the mirror technology used, broadband lighting in a large spectral range is conceivable. The mirror optics used are largely independent of the selected color or the selected wavelength range, as a result of which the measuring device is highly flexible. The system is therefore basically suitable for measurements in the UV range, the visual range, the short-wave infrared range and the other infrared ranges, for example. In addition, a large-scale representation of the measuring marks or a representation of several identical measuring marks distributed in one field is made possible. Moving measuring marks can also be displayed. Due to the central electronic control device, in particular, which is set up to control the digital micromirror device and the lighting device, the measurement marks can be freely generated in form and contrast by software, so that the measurement setup can also be used for other measurement methods. Alternative test patterns such as Landolt rings, Snellen tables, sine patterns for machine evaluation or new test patterns such as triangles (e.g. for TOD / Triangle Orientation Discrimination) or measurement patterns for distortion measurement can also be displayed. The measuring system can automatically regulate the shutters or shutters of the light sources and generate patterns on the DLP actuator. Sizes derived from this, such as line pairs / line pairs per mm, are set directly. The user can continuously change the resolution, the contrast or the illuminance or irradiance, so to speak, with a simple push of a button, until the test pattern can no longer be resolved by the system to be tested. The results determined in this way can be stored directly in a table, from where they can be transferred to an atmosphere simulation program and evaluated in order to determine the detection ranges. By a Central operation and a digital input of measurement parameters can be measured faster and the results can be saved directly. The illuminance is automatically adjusted to the selected wavelength range. New test patterns can be generated quickly by software, which means that the measuring device can also be adapted to the needs of future measuring processes or alternative measurements can also be carried out. The measuring device according to the invention with the programmable micromirror targets and the corresponding lighting enables a very advantageous direct method for measuring the contrast. It is also conceivable that the measuring station independently different measuring marks, z. B. as a sine pattern, modulated and objectively evaluates the image or video of the system under test by means of image processing.

The spectral measuring range can be narrowed down and the lighting can be automatically adapted to measuring models using calibrated look-up tables. Appropriate control devices, for example exchangeable spectral filters or exchangeable light sources, can be provided for this purpose. There is also the possibility of simulating wavelength-dependent reflectivities of the target objects, e.g. B. with lighting at different times of the day. The user simply enters the desired contrast and wavelength and the software regulates everything accordingly.

The DLP actuator is also known as a DMD (Digital Micromirror Device) or digital micromirror device and consists of millions of small mirrors that can be switched bistably. Individual mirror elements of the DLP actuator have two stable positions, for example at + 12º "on" and at -12º "off". A light source can illuminate the DLP actuator at an angle of 24º. In the "on" state, the DLP mirrors reflect the light or radiation in the direction of the camera examinee. In the "off" state, the light is directed into a beam trap, which serves to almost completely absorb the radiation.

It is advantageous if the lighting device has a second lighting path, which is designed to illuminate the digital micromirror device with the light of the at least one controllable light source in such a way that the micromirror actuators direct the light in the second position in the direction, in particular an input optics, of the direct optical view - Steer, image acquisition or camera system and steer into the beam trap in the first position. This allows the lighting to be regulated better.

The at least one controllable light source can be provided with a controllable diaphragm, for example an iris diaphragm or the like, or a controllable closure, in particular for the precise setting of the irradiance or illuminance.

The at least one controllable light source can be provided with an integrating sphere. Alternatively, other regulated and homogeneous lighting methods can also be used.

It is advantageous if the at least one light source is provided with a measuring device for detecting the irradiance. The measuring device can e.g. B. as a lux meter or thermometer (z. B. in the infrared range).

This measure makes it possible to absolutely set or regulate the specified or required illuminance or irradiance.

The light from the at least one light source can be in a wavelength range from approximately 200 nm to approximately 12 μm or parts thereof. This advantageously enables optical systems whose useful wavelength range lies outside the visible wavelength range to be tested in the measuring device. It is also advantageous if there are several controllable light sources with different wavelength ranges. This means that different systems can be tested with just one measuring device.

The first lighting path and / or the second lighting path can have an additional controllable diaphragm.

The lighting device can have at least one first controllable light source and at least one second controllable light source.

It is very advantageous if the first controllable light source is arranged in the first illumination path and the second controllable light source is arranged in the second illumination path.

These measures make it possible to continuously adjust the object-background contrast ratio depending on the respective spectral measuring range. The DLP elements are illuminated from two sides with two adjustable light sources. The measuring mark contrast is thus infinitely adjustable via the two light sources. This makes the proposed measuring device even more flexible.

The adjustable contrast can be determined by a difference between the irradiance of the first controllable light source and the Irradiance of the second controllable light source are generated.

If only one controllable light source and only one illumination path are used, the adjustable contrast can alternatively be generated by modulation, preferably pulse width modulation, of certain micromirror actuators of the digital micromirror device.

In a constructive embodiment of the invention, a collimator or a device for collimating the light directed onto the optical direct vision, image acquisition or camera system can be present.

An absolute irradiance or illuminance or brightness, a wavelength range, a contrast and / or an appearance of the measurement pattern can be set as measurement parameters by means of the electronic control device. A digital input of measurement parameters enables measurements to be taken much faster. This can be done via a software interface, for example. The possibility of freely regulating the measurement pattern, resolution, contrast and irradiance means that higher accuracy and / or faster measurement is achieved. The measuring stand can be adapted to measuring methods with other measuring patterns by software without hardware changes. The adjustment of the spectral measuring range and an automatic lighting adjustment, for example to measurement models, can be done using calibrated look-up tables. Corresponding controllable actuating devices, for example exchangeable spectral filters or exchangeable light sources, can be provided for this purpose.

It is very advantageous if the control device is set up to control the digital micromirror device and the lighting device in such a way that by switching the micromirror actuators in conjunction with their lighting, a periodic or oscillating movement laterally or perpendicularly to an optical axis of the measuring device and / or the optical direct vision, image acquisition or camera system, in particular a shift of the measurement pattern can be carried out.

To avoid an aliasing effect, the captured image of the test pattern can be laterally shifted on the detector chip of the camera system to be tested. This can be achieved in that the generated measurement pattern is oscillated on the digital mirror device. This has the same effect. It is advantageous if the shift is a multiple of a pixel size, in particular a length or a width of a pixel or pixel, in particular an image sensor, of the optical direct vision, image acquisition or camera system. The generated pattern can be shifted in an oscillating manner on the micromirror device. For anti-aliasing, the shift can be several periods of the pixel size or a multiple of the pixel size of the detector chip. For example, if the pixel size of a camera to be tested is 3.5 µm in the visual spectrum, it could be shifted with an amplitude of 1 mm over a period of 5 seconds. This also ensures that the observer has sufficient image quietness. However, these parameters are variable and depend on the detector to be tested, the focal lengths of the detector optics and the measuring device. Requirements of the observer can also be taken into account.

Claim 16 specifies a method for determining the minimally resolvable contrast in a predetermined irradiance of an optical direct vision, image acquisition or camera system to be tested and which can be arranged in a measuring device.

Advantages for this result analogously and on the basis of the description.

It is very advantageous if the parameters or quantities of absolute brightness or irradiance and contrast can be set independently of one another in the measuring device. This enables very precise measurement results to be achieved. If only one controllable light source is available, the contrast can be achieved via the switching frequency of the DLP actuator. For example, one could set an absolute brightness with only one controllable light source (e.g. 10,000 lux), the difference, for example at 30% contrast, being achievable by switching the optics by only 70%. With two independent, controllable light sources, the two parameters absolute brightness and contrast could be set independently of one another.

Advantageous refinements and developments of the invention result from the subclaims.

Exemplary embodiments of the invention are described below with reference to the drawing.

• 1 Eine vereinfachte schematische Darstellung einer Bilderzeugung mittels DLP (Digital Light Processing);
• 2 eine schematische Darstellung der Messung eines minimal auflösbaren Kontrasts mittels DLP;
• 3 eine schematische Darstellung einer erfindungsgemäßen Messvorrichtung;
• 4 schematisch eine erste Ausführungsform einer Beleuchtungseinrichtung der erfindungsgemäßen Messvorrichtung;
• 5 schematisch eine zweite Ausführungsform einer Beleuchtungseinrichtung der erfindungsgemäßen Messvorrichtung;
• 6 schematisch eine dritte Ausführungsform einer Beleuchtungseinrichtung der erfindungsgemäßen Messvorrichtung; und
• 7 schematisch eine vierte Ausführungsform einer Beleuchtungseinrichtung der erfindungsgemäßen Messvorrichtung.

Show it:

• 1 A simplified schematic representation of an image generation using DLP (Digital Light Processing);
• 2nd a schematic representation of the measurement of a minimally resolvable contrast using DLP;
• 3rd a schematic representation of a measuring device according to the invention;
• 4th schematically a first embodiment of an illumination device of the measuring device according to the invention;
• 5 schematically a second embodiment of an illumination device of the measuring device according to the invention;
• 6 schematically a third embodiment of an illumination device of the measuring device according to the invention; and
• 7 schematically a fourth embodiment of an illumination device of the measuring device according to the invention.

In 1 an image generation using a digital light processing system (DLP) is shown in a highly simplified manner. The DLP system has a digital micromirror device 1 , also called Digital Micro Device (DMD), which consists of a large number (e.g. millions) of matrix-shaped micromirror actuators 1a exists, which are each switchable into a first stable position and a second stable position, ie bistable. How out 1 can be seen, have the micromirror actuators 1a two stable positions, namely S1 ("on"), e.g. B. at + 12º, and S2 ("Off"), e.g. B. at -12 °. There is also a zero position at 0º ("No power"). An adjustable light source 2nd shines on the micromirror actuator, for example, at an angle of 24 ° 1a . In the first position S1 reflect the micromirror actuators 1a a radiation or a light L1 the adjustable light source 2nd in the direction of a camera test or optical direct vision, image acquisition or camera system to be tested 3rd or on an entrance optics 3a of the optical direct vision, image acquisition or camera system to be tested 3rd . How out 1 can be seen further, a facility 4th for collimation of the optical direct vision, image acquisition or camera system 3a directed light L1 , for example a collimator or a collimator lens. That in the entrance optics 3a incoming reflected and collimated light from the controllable light source 2nd is with the reference symbol L1 ' Mistake. In the second stable position S2 becomes the light L1 into a beam trap 5 directed.

Functionally identical elements are provided with the same reference symbols in the figures.

The lighting of the digital micromirror device is generally sufficient 1 with only one controllable light source 2nd to achieve the effects of the invention. Contrast can be regulated by the switching times of the digital micromirror device 1 , in particular by modulation (pulse width modulation / PWM) of the micromirror actuators 1a can be achieved.

However, the inventor has found that for a continuous control of the contrast, it is very advantageous to use the micromirror actuators as in FIG 2nd shown from two sides with a first controllable light source 2.1 and a second controllable light source 2.2 with radiation or light L1 , L2 or. L1 ' , L2 ' to illuminate. By independently regulating the light sources 2.1 and 2.2 different object-background contrasts can be created.

• - die digitale Mikrospiegeleinrichtung 1 mit der Vielzahl von matrixförmig angeordneten Mikrospiegelaktoren 1a, welche jeweils in die erste stabile Stellposition S1 und in die zweite stabile Stellpositon S2 schaltbar sind;
• - eine Beleuchtungseinrichtung 7 mit wenigstens einer regelbaren Lichtquelle 2.1, 2.2 und einem ersten Beleuchtungspfad 7a, welcher dazu ausgelegt ist, die digitale Mikrospiegeleinrichtung 1 derart mit dem Licht L1 der wenigstens einen Lichtquelle 2.1 zu beleuchten, dass die Mikrospiegelaktoren 1a das Licht L1 in der ersten Stellposition S1 in Richtung, insbesondere der Eingangsoptik 3a des optischen Direktsicht-, Bilderfassungs- oder Kamerasystems 3 lenken und in der zweiten Stellposition S2 in die Strahlfalle 5 lenken; und
• - eine elektronische Steuereinrichtung 8, welche dazu eingerichtet ist, die digitale Mikrospiegeleinrichtung 1 und die Beleuchtungseinrichtung 7 derart anzusteuern, dass durch die Schaltung der Mikrospiegelaktoren 1a in Verbindung mit deren Beleuchtung die Messmuster erzeugbar sind.

3rd shows a measuring device according to the invention 6 for determining a minimally resolvable contrast in a predetermined irradiance of the device under test in the measuring device 6 optical direct vision, image acquisition or camera systems can be arranged 3rd , wherein several measurement patterns, not shown, with different adjustable contrasts with the optical direct vision, image acquisition or camera system 3rd captured and the finest measurement patterns, which still by means of the optical direct vision, image acquisition or camera system 3rd are resolvable, determined, comprising at least:

• - The digital micromirror device 1 with the large number of micromirror actuators arranged in a matrix 1a , each in the first stable position S1 and in the second stable position S2 are switchable;
• - a lighting device 7 with at least one controllable light source 2.1 , 2.2 and a first lighting path 7a , which is designed for the digital micromirror device 1 so with the light L1 the at least one light source 2.1 to illuminate the micromirror actuators 1a the light L1 in the first position S1 towards, especially the entrance optics 3a the optical direct vision, image acquisition or camera system 3rd steer and in the second position S2 into the beam trap 5 to steer; and
• - an electronic control device 8th , which is set up the digital micromirror device 1 and the lighting device 7 to be controlled such that by switching the micromirror actuators 1a the measurement patterns can be generated in connection with their illumination.

With the electronic control device 8th it can be a central electronic control device which permits central software control of all mechanical setting options of the system. Central operation and digital input of measurement parameters mean that measurements can be made faster and the results can be saved directly. In the electronic control device 8th Calibration data and / or control curves can be stored, in particular in look-up tables 9.

A sensor input 8a the electronic control device 8th can be a measured irradiance or illuminance and / or positioning positions of adjustable diaphragms 10 (please refer 4th - 7 ) received as input signals.

User input can also be used 8b the electronic control device can be provided, which can receive the wavelength range, the measurement method and / or the measurement pattern or target as input.

Furthermore, image reproduction 8c be provided which z. B. outputs the target frequency and other parameters.

How out 3rd further visible, the lighting device 7 a second lighting path 7b on which is designed the digital micromirror device 1 so with the light L1 , L2 the at least one light source 2.2 to illuminate the micromirror actuators 1a the light L2 in the second position S2 towards, especially the entrance optics 3a the optical direct vision, image acquisition or camera system 3rd steer and in the first position S1 into the beam trap 5 to steer.

The at least one light source 2.1 , 2.2 can be provided with at least one measuring device, not shown, for detecting the irradiance, which is connected to the sensor input 8a to control or regulate the at least one light source 2.1 , 2.2 through the electronic control device 8th connected is. The at least one measuring device can, for. B. in the area of the beam traps 5 be arranged.

In other alternative exemplary embodiments, however, the lighting device can also only have a single controllable light source 2.1 or a single lighting path 7a exhibit. Such embodiments are in the 4th to 6 shown.

4th shows a first embodiment of a lighting device 7.1 with an adjustable light source 2.1 . The light source 2.1 is with an adjustable aperture 10 and with an optional integrating sphere 11 Mistake. The adjustable aperture 10 can for example be designed as an iris diaphragm. The contrast between the light L1 ' and the light L2 ' can by modulating individual micromirror actuators 1a be generated. Only one lighting path is available 7a available. This represents the simplest lighting option. The controllability is due to the switching times of the DLP elements or micromirror actuators 1a limited.

In 5 is a second embodiment of a lighting device 7.2 shown. The lighting device 7.2 has a second lighting path 7b on which is designed the digital micromirror device 1 so with the light L2 the light source 2.1 to illuminate the micromirror actuators 1a the light in the second position S2 towards, especially the entrance optics 3a the optical direct vision, image acquisition or camera system 3rd steer and in the first position S1 into the beam trap 5 to steer. Because of the further adjustable aperture 10 in the first lighting path 7a is the irradiance of the light L1 always less than or equal to the irradiance of the radiation L2 . Through the further lighting path 7b better controllability can be achieved.

In 6 is a third embodiment of the lighting device 7.3 shown. Here too is a second lighting path 7b intended. Both lighting paths 7a , 7b are with an additional adjustable aperture 10 provided, causing the radiations L1 and L2 can be regulated separately. Through the same components in the lighting paths 7a , 7b the intensity can easily be regulated to the same values. The irradiance can be regulated indirectly via the control signals of the adjustable diaphragms.

7 shows a fourth embodiment of a lighting device 7 which is the first controllable light source 2.1 and the second controllable light source 2.2 having. The first adjustable light source 2.1 is in the first lighting path 7a and the second controllable light source 2.2 in the second lighting path 7b arranged. The adjustable contrast can be determined by a difference between the irradiance of the first controllable light source 2.1 and the irradiance of the second controllable light source 2.2 be generated.

An absolute irradiance or a brightness, a wavelength range, a contrast and / or an appearance of the measurement pattern by means of the electronic control device can be used as measurement parameters 8th be adjustable.

The light of the at least one light source 2.1 , 2.2 can be in a wavelength range from approximately 200 nm to approximately 12 μm or parts thereof. To the measuring device 6 Several controllable light sources can be made even more variable 2.1 , 2.2 be available with different wavelength ranges (not shown). Appropriate control devices, for example exchangeable spectral filters or exchangeable light sources, could be provided for this purpose. The exchangeable spectral filters could be analogous to the adjustable diaphragms 10 be arranged and over the look-up tables 9 to be selected.

The electronic control device 8th can be set up the digital micromirror device 1 and the lighting device 7 to be controlled such that by means of the switching of the micromirror actuators 1a in connection with their illumination, a periodic or oscillating movement laterally or perpendicular to an optical axis of the measuring device, not shown 6 and / or the optical direct vision, image acquisition or camera system 3rd , in particular a shift of the measurement pattern can be carried out.

The shift can be a multiple of a pixel size, in particular a length or a width of a pixel or pixel, in particular an image sensor (not shown) of the direct view optical, image acquisition or camera system 3rd be.

Reference list

1

Digital micromirror device

1a

Micromirror actuators

2, 2.1, 2.2

adjustable light source

3rd

optical direct vision, image acquisition or camera system

3a

Entrance optics

4th

Collimation facility

5

Beam trap

6

Measuring device

7, 7.1-7.3

Lighting device

7a

first lighting path

7b

second lighting path

8th

electronic control device

8a

Sensor input

8b

User input

8c

Image rendering

9

Look-up tables

10th

adjustable aperture

11

Ulbricht sphere

L1

Light from the first controllable light source

L1 '

reflected light from the first controllable light source

L2

Light from the second adjustable light source

L2 '

reflected light from the second controllable light source

S1

first position

S2

second position

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• CN 102279092 B [0006]
• US 4299451 [0008]
• EP 0864231 B1 [0009]

Claims (18)

Measuring device (6) for determining the minimum resolvable contrast in a predetermined irradiance of an optical direct vision, image acquisition or camera system (3) to be tested, which can be arranged in the measuring device (6), several measuring patterns with different adjustable contrasts with the optical direct vision, Image acquisition or camera system (3) is recorded and the finest measurement patterns that can still be resolved by means of the optical direct vision, image acquisition or camera system (3) are determined, comprising at least: - A digital micromirror device (1) with a plurality of micromirror actuators (1a) arranged in a matrix, which can each be switched into a first stable actuating position (S1) and a second stable actuating position (S2); - A lighting device (7, 7.1-7.3) with at least one controllable light source (2.1, 2.2) and a first lighting path (7a), which is designed to provide the digital micromirror device (1) with the light (L1) of the at least one controllable one To illuminate the light source (2.1) that the micromirror actuators (1a) direct the light (L1) in the first setting position (S1) in the direction, in particular an input optics (3a) of the optical direct vision, image acquisition or camera system (3) and in the direct the second position (S2) into a beam trap (5); and - An electronic control device (8) which is set up to control the digital micromirror device (1) and the lighting device (7, 7.1-7.3) in such a way that the measurement patterns can be generated by switching the micromirror actuators (1a) in connection with their illumination . Measuring device (6) after Claim 1 The lighting device (7, 7.2, 7.3) has a second lighting path (7b), which is designed to illuminate the digital micromirror device (1) with the light (L2) of the at least one controllable light source (2.2) such that the Micromirror actuators (1a) direct the light (L2) in the second setting position (S2) in the direction, especially an input optics (3a) of the optical direct vision, image acquisition or camera system (3) and in the first setting position (S1) into the beam trap ( 5) steer. Measuring device (6) after Claim 1 or 2nd The at least one controllable light source (2.1, 2.2) is provided with a controllable diaphragm (10). Measuring device (6) after Claim 1 , 2nd or 3rd The at least one light source (2.1, 2.2) is provided with an integrating sphere (11). Measuring device (6) according to one of the Claims 1 to 4th The at least one controllable light source (2.1, 2.2) is provided with a measuring device for detecting the irradiance. Measuring device (6) according to one of the Claims 1 to 5 The light of the at least one controllable light source (2.1, 2.2) lies in a wavelength range from approximately 200 nm to approximately 12 µm or parts thereof. Measuring device (6) according to one of the Claims 1 to 6 , with several controllable light sources (2.1, 2.2) with different wavelength ranges. Measuring device (6) according to one of the Claims 1 to 7 The first illumination path (7a) and / or the second illumination path (7b) have an additional controllable diaphragm (10). Measuring device (6) according to one of the Claims 1 to 8th The lighting device (7, 7.2, 7.3) has at least one first controllable light source (2.1) and at least one second controllable light source (2.2). Measuring device (6) after Claim 9 The first controllable light source (2.1) is arranged in the first illumination path (7a) and the second controllable light source (2.2) is arranged in the second illumination path (7b). Measuring device (6) after Claim 9 or 10 The adjustable contrast is generated by a difference between the irradiance of the first controllable light source (2.1) and the irradiance of the second controllable light source (2.2). Measuring device (6) according to one of the Claims 1 to 7 The adjustable contrast is generated by modulation, preferably pulse width modulation, of certain micromirror actuators (1a) of the micromirror device (1). Measuring device (6) according to one of the Claims 1 to 12th A device (4) for collimating the light directed onto the optical direct vision, image acquisition or camera system (3) is provided. Measuring device (6) according to one of the Claims 1 to 13 An absolute irradiance or brightness, a wavelength range, a contrast and / or an appearance of the measurement pattern can be set as the measurement parameter by means of the electronic control device (8). Measuring device (6) according to one of the Claims 1 to 14 , wherein the electronic control device (8) is set up to control the digital To control the micromirror device (1) and the lighting device (7) in such a way that by means of the switching of the micromirror actuators (1a) in connection with their lighting, a periodic or oscillating movement laterally or perpendicularly to an optical axis of the measuring device (6) and / or the direct optical view -, image acquisition or camera system (3), in particular a shift of the measurement pattern can be carried out. Method for determining the minimally resolvable contrast in a predetermined irradiance of an optical direct view, image acquisition or camera system (3) to be tested, which can be arranged in a measuring device (6), with measurement patterns for different adjustable contrasts with the optical direct view, image acquisition or camera system (3) recorded and the finest measurement patterns that can still be resolved by means of the optical direct vision, image acquisition or camera system (3) are determined, whereby: the measuring device (6) has a digital micromirror device (1) with a multiplicity of micromirror actuators (1a) arranged in a matrix, which are each switched into a first stable actuating position (S1) and into a second stable actuating position (S2), - The digital micromirror device (1) is illuminated in such a way that the micromirror actuators (1a) of the digital micromirror device (1) direct the light in the first position (S1) in the direction, in particular an input optics (3a) of the optical direct vision, image acquisition or camera system (3) steer and in the second position (S2) steer into a beam trap (5); and - The measurement patterns are generated by switching the micromirror actuators (1a) and their lighting. Procedure according to Claim 16 , The micromirror actuators (1a) being switched and illuminated in such a way that the measurement pattern, in particular laterally or perpendicularly to an optical axis of the measuring device (6) and / or the optical direct vision, image acquisition or camera system (3), moves periodically or oscillating , preferably be moved. Procedure according to Claim 17 , wherein the shift is a multiple of a pixel size, in particular a length or a width of a pixel or image point, in particular an image sensor, of the optical direct view, image acquisition or camera system (3).

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