Method and device for optically measuring an optically active surface of an at least partially transparent sample body

Abstract

The invention relates to a method and a device (8) for optically measuring an at least partially transparent sample body (10) with an optically active first surface and a second surface lying opposite thereto. The method is carried out using reflection geometry and has the following steps: i) applying a highly viscous reflection-reducing fluid (1) onto the second surface of the sample body (10); ii) carrying out the optical measurement process; and iii) removing the highly viscous reflection-reducing fluid (1).

Description

[0001] Method and device for optically measuring an optically effective surface of an at least partially transparent test specimen

[0002] The present invention relates to a method and a device for optically measuring an at least partially transparent test specimen having an optically effective first surface and an opposite second surface in reflection geometry, as well as the use of a reflection-reducing, highly viscous fluid in such a method.

[0003] Methods for measuring at least partially transparent specimens are known in the literature. For example, a specimen's surface can be scanned using an altimeter to create a profile of the surface. However, a disadvantage of this tactile measurement is the risk of scratching the surface.

[0004] As an alternative to these contact-based measurement methods, contactless optical methods are known. These methods involve shining light onto the sample and detecting the light, which is altered by an optically active surface of the sample, in reflection and / or transmission geometry.

[0005] Particularly in the case of measurements in reflection geometry, the measurement result can be distorted or impaired by backside reflections, i.e. reflections on a surface of the test specimen that is opposite the surface irradiated with light.

[0006] In practice, various methods have been established to reduce such backside reflection. For example, mechanically or chemically roughening or matting the backside is known to prevent a directed reflection caused by scattering. If necessary, the matted surface can be coated with a dye to further attenuate the scattered light. The matting and, if applicable, the coloring are removed from the backside in a subsequent grinding and polishing process. Therefore, this method is only suitable for the optical measurement of precursors, where at least the backside of the sample specimen undergoes further treatment.

[0007] Another option for reducing backside reflection is to coat the back of the sample with a sealing wax. However, removing the wax after measurement is time-consuming and requires the use of solvents, which can be harmful to health and / or the environment.

[0008] Finally, it is possible to cover the back of the test specimen with adhesive tape. However, specific properties of the adhesive tape, such as its adhesive strength, must be taken into account. It is also important that the adhesive tape adheres evenly to the back, as the formation of air bubbles can cause reflections on the uncoated areas. This method therefore requires some practice and is not always reliable.

[0009] In summary, the methods currently used to reduce back reflection in the optical measurement of transparent specimens have the following disadvantages:

[0010] Suitable only for pre-products, as the back is irreversibly damaged, complex to apply and unreliable, and / or complex to remove.

[0011] Against this background, the object of the present invention is to provide an alternative method and a corresponding device for reducing a backside reflection during the optical measurement of an at least partially transparent specimen with an optically effective first surface and an opposite second surface in reflection geometry, which does not have the disadvantages of the known methods. In particular, the method should be simple to apply and non-destructive.

[0012] This object is achieved by the embodiments characterized in the claims.

[0013] According to one aspect, a method is provided for the optical measurement of an at least partially transparent test body having an optically effective first surface and an opposite second surface, wherein the method is carried out in reflection geometry and comprises the following steps: i) applying a reflection-reducing, highly viscous fluid to the second surface of the test body; ii) performing the optical measurement; and iii) detaching the reflection-reducing, highly viscous fluid.

[0014] The method according to the invention is used for the optical measurement of an at least partially transparent specimen with an optically effective first surface. This means that the specimen to be measured does not have to be transparent over the entire extent of the first surface, but can, for example, have a non-transparent edge region. To be suitable for the method according to the invention, the specimen must therefore only be transparent in the area relevant for the measurement.

[0015] The first surface of the test specimen is optically effective. This means that incident light rays are refracted at the first surface. Examples of test specimens for which the method according to the invention is suitable include semi-finished and finished products of optical lenses, as well as casting molds made of (mineral) glass, in particular for optical lenses or their (semi-)finished products.

[0016] In semi-finished lenses, only the first surface has received the desired optical polish, while the second surface has not yet been significantly processed. By measuring semi-finished products, quality control can be performed during production, and the polish of the first surface can be corrected if necessary.

[0017] Finished lenses differ from semi-finished lenses in that a second surface, opposite the first surface, has also been ground and is therefore also optically effective. For this type of sample, the method according to the invention serves as a final inspection for the quality of the lens. Since, as explained in detail below, the method according to the invention can be carried out without damage and the highly viscous fluid can be removed from the sample using simple means, the method according to the invention is particularly suitable for measuring finished optical lens products.

[0018] The material of the specimen is not particularly limited, as long as it is at least partially transparent and at least one surface of the specimen can be brought into an optically effective state. In particular, the specimen can be made of plastic or mineral glass. In the case of specimens made of mineral glass, for example, silicate glass, a backside reflection occurs more frequently during optical measurements in reflection geometry, making it impossible to measure a specimen without prior treatment of the backside. Thus, the method according to the invention is particularly suitable for specimens made of mineral glass.

[0019] For the optical measurement of the specimen in reflection geometry, light is shone onto the first, optically effective, surface. The shone light is reflected by the first surface, and the optical effectiveness of the first surface is determined based on the deviation of the reflected light from the incident light. However, a portion of the shone light is not reflected by the first surface, but passes through it and strikes the second surface of the specimen, where it can be reflected.

[0020] The light used for the measurement can be white or visible light, for example, or it can have a specific wavelength or wavelength range. For example, the light can be in a wavelength range from 380 nm to 800 nm or from 400 nm to 780 nm. However, only wavelength ranges can be used, for example ultraviolet light (UV-C: 100 to 280 nm, UV-B: 280 to 315 nm and / or UV-A: 315 to 380 nm), violet light with 380-450 nm, blue light with 450-495 nm, green light with 495-570 nm, yellow light with 570-590 nm, orange light with 590-620 nm, red light 620-750 nm, infrared light (IR-A: 780 to 1400 nm and / or IR-B: 1400 to 3000 nm) or mixtures thereof.

[0021] The reflection-reducing, high-viscosity fluid of the present invention serves to suppress this secondary reflection. For the purposes of the present invention, a fluid is considered reflection-reducing if it suppresses secondary reflection, particularly in the wavelength range used for measurement, by at least 50%, preferably 75%, more preferably 90%, and most preferably 99%.

[0022] The fluid used in the method of the present invention is highly viscous. This means that the fluid is adjusted to be fluid enough to be applied to the second surface of the specimen without bubbles and without damage, while being viscous enough not to drip off the specimen.

[0023] In a preferred embodiment of the present invention, the anti-reflective fluid has a viscosity in the range of approximately 10,000 mPas to approximately 100,000 mPas, preferably approximately 20,000 mPas to approximately 50,000 mPas. The viscosity can be determined using a rotational viscometer (e.g., Ametek DV2T viscometer with spindle RV-5) at a temperature of 23°C and a rotation frequency of 20 rpm. The aforementioned viscosity values ​​marked with "approximately" may deviate by up to 10%, preferably up to 5%, upwards or downwards, but in particular represent the exact value.

[0024] The occurrence of secondary reflections at the second surface of the sample can be suppressed, for example, by matching the refractive index of the high-viscosity fluid to the refractive index of the sample. Reflections generally occur at interfaces where the refractive index of the propagation medium changes. For this reason, the refractive index of the high-viscosity fluid preferably deviates from the refractive index of the sample by 10% or less. In a preferred embodiment, the refractive index of the high-viscosity fluid deviates from the refractive index of the sample by 5% or less, more preferably 1% or less.

[0025] Alternatively or additionally, the highly viscous fluid can be adjusted to absorb the incident light passing through the transparent specimen. For this purpose, pigments that absorb in the wavelength range of the incident light can be added to the highly viscous fluid. For example, black pigments such as metal oxides, especially iron oxide, (wood) charcoal, graphite, or carbon black can be added.

[0026] In a preferred embodiment, the highly viscous fluid absorbs the light passing through the test specimen by at least 75%, more preferably at least 90% and most preferably at least 99%.

[0027] In the first step of the method according to the invention, the reflection-reducing, highly viscous fluid is applied to the second surface of the test specimen. The application method is not further limited and includes, among others, a dip coating method, a spin coating method, a transfer coating method, and a doctor blade coating method.

[0028] The viscosity and wetting properties of the anti-reflective fluid can be adjusted to achieve good adhesion to the specimen. For example, the surface tension of the fluid can be reduced using surface-active substances, such as surfactants, to achieve improved wetting properties.

[0029] In a preferred embodiment, the highly viscous, anti-reflective fluid has a surface tension of less than 62.5 mN / m. The surface tension is particularly preferably between approximately 29 mN / m and approximately 60 mN / m, in particular between approximately 45 mN / m and approximately 60 mN / m. The aforementioned surface tension values ​​marked with "approximately" may deviate by up to 5%, preferably up to 1%, upwards or downwards, but in particular represent the exact value. The surface tension can be determined using the conventional ironing or tear-off method.

[0030] After applying the reflection-reducing, highly viscous fluid to the second surface of the specimen, the first, optically active surface of the specimen is optically measured in reflection geometry. As explained above, corresponding methods are known to those skilled in the art.

[0031] After the optical measurement, the reflection-reducing, highly viscous fluid is removed from the sample. In the simplest case, the fluid can be removed completely without leaving any residue. In this case, the fluid can be reused for further measurements. Alternatively, the fluid can be removed with a suitable solvent.

[0032] In a preferred embodiment, the solvent is water and the fluid is water-soluble. For the purposes of the present application, water-soluble means that at a temperature of 20°C, at least 50 g, preferably 100 g, of the fluid completely dissolves in one liter of water.

[0033] Preferably, the method can be carried out automatically. The test specimen can be moved to a dispenser by means of a manipulator or a transport device, for example, a roller conveyor, which applies or dispenses a predetermined amount of the highly viscous, reflection-reducing fluid onto the second surface of the test specimen. Optionally, the fluid can be distributed by rotating the test specimen or by spreading it with a tool, so that the fluid covers substantially the entire second surface of the test specimen.

[0034] The optical measurement can also be performed automatically, especially after the specimen has been moved to a measuring device using a manipulator or transport device. The measurement results can be transferred from the measuring device to a memory or an external computer via a data line.

[0035] The removal of the reflection-reducing, highly viscous fluid from the specimen can also be automated, particularly after the specimen has been moved to a cleaning device by means of the manipulator or transport device. In the case of a water-soluble, reflection-reducing, highly viscous fluid, removal can advantageously be achieved by rinsing with a jet of a cleaning fluid or by immersion in a cleaning fluid, wherein the cleaning fluid can, in particular, be water.

[0036] One aspect of the present invention relates to a reflection-reducing high-viscosity fluid comprising:

[0037] - a mass fraction of 49% to 61% of a polymer dispersion,

[0038] - a mass fraction of 23% to 30% of a foam,

[0039] - a mass fraction of 9% to 11% of a diluent, and

[0040] - a mass fraction of 8% to 10% of a colour, where the sum of all mass fractions is 100%.

[0041] A further aspect of the present invention relates to the use of the reflection-reducing high-viscosity fluid in a method according to the invention.

[0042] The reflection-reducing, highly viscous fluid, in particular the foam, preferably contains saccharides, in particular mucopolysaccharide and / or glycosaminoglycans such as aloverose or acemannan and / or D-glucose or D-mannose, which are contained in aloe vera juice. For this purpose, the foam or fluid can contain or comprise aloe vera juice, with the foam preferably containing a mass fraction of about 0.5% to about 40%, preferably about 1% to about 30%, in particular about 1% to about 5% aloe vera juice, preferably from the leaves of Aloe barbadensis. The addition of aloe vera juice advantageously enables the production of a particularly smooth and viscosity-stable fluid.According to a further aspect, a device for carrying out a method for optically measuring an at least partially transparent test body with an optically effective first surface and an opposite second surface in reflection geometry is proposed, wherein the method is defined by the features described above.

[0043] The device comprises: a holder for the specimen to be measured; a manipulator; a pretreatment unit for applying a highly viscous, reflection-reducing fluid to a second surface opposite the first surface of the specimen to be measured; a measuring unit for recording a reflection measurement by irradiating a measuring position on the surface of the specimen to be measured with light and detecting at least a portion of the light reflected by the specimen during the irradiation; a post-treatment unit for removing the highly viscous, reflection-reducing fluid located on the second surface of the specimen to be measured.

[0044] Furthermore, the aforementioned preferred embodiments and / or the aforementioned advantages also apply to this device in a corresponding manner.

[0045] The holder for the specimen to be measured can be any holder designed to accommodate the specimen to be measured. The holder can, for example, consist of a base or support plate or comprise a base or support plate. Alternatively and / or additionally, the holder can contain a holder for the specimen to be measured.

[0046] The manipulator, also referred to as a transport device, is not further restricted as long as it is designed to move the holder with the test specimen to be measured relative to the pre-treatment unit, relative to the measuring unit and relative to the post-treatment unit. This can be understood as both a movement of the holder to the immobile units and a movement of the respective units to a immobile holder for the test specimen to be measured, as well as combinations thereof. In the case of immobile units, at least one actuator can be used as the preferred manipulator, which converts control commands received from a control device into a movement and thus moves the holder for the test specimen to be measured to the individual units. This can be implemented cost-effectively, for example, by mounting the holder on a roller conveyor.The roller conveyor can perform a movement, particularly a linear one, with the units arranged along the direction of movement of the roller conveyor. In the case of a stationary mount for the specimen to be measured, one or more actuators can be used as the preferred manipulator(s), which move the respective units for the mount. Advantageously (for example, for cost reasons), only one actuator can be used, which causes a displacement of a mount, with the pretreatment unit, measuring unit, and post-treatment unit being arranged on this mount.For example, the pre-treatment unit, measuring unit and post-treatment unit can be arranged on a rotatable holder like a carousel, whereby by performing a rotating movement of the holder, one of the units is moved into the direct vicinity of the holder for the test specimen to be measured in order to carry out the steps intended for the respective unit there.

[0047] The pretreatment unit, also referred to as a pretreatment station, is designed to apply a highly viscous, anti-reflective fluid according to one aspect of the present application to a second surface of the sample to be measured, opposite the first surface to be measured. The pretreatment unit can be implemented, for example, as a dispenser which, connected to a reservoir containing the highly viscous, anti-reflective fluid, applies or dispenses the fluid onto the second surface of the sample to be measured. Alternatively or additionally, the fluid can be distributed by rotating the sample or by spreading it using a tool, so that, for example, the fluid essentially covers the entire second surface of the sample. Furthermore, dip or transfer coating of the second surface of the sample to be measured with the fluid is possible.In addition, the pretreatment unit can also be designed to clean the sample to be measured before applying the fluid.

[0048] The measuring unit, also referred to as a measuring device or reflection detection unit, can comprise at least one light source for irradiating the sample body with light (measuring light) and at least one detector for detecting at least a portion of the light reflected by the sample body during irradiation. The light source can be a suitable light source and can comprise one or more LEDs, lamps (e.g., white light lamps), lasers (such as tunable lasers or frequency-doubling lasers), etc. Such a measuring unit can be a spectrometer familiar to those skilled in the art, comprising a suitable light source and a detector.

[0049] The post-treatment unit, also referred to as a post-treatment station or cleaning device, is designed to detach or remove the highly viscous, anti-reflection fluid from the second surface of the test specimen. The post-treatment unit is not further restricted and can be implemented in various ways, as long as it is designed to remove the fluid from the test specimen, in particular without leaving any residue.

[0050] In the case of a water-soluble, reflection-reducing, highly viscous fluid, the removal can advantageously be carried out by rinsing with a jet of a cleaning fluid or by immersion in a cleaning fluid, wherein the cleaning fluid can in particular be water. Alternatively, particularly if a reusable fluid is present or used, the fluid can also be withdrawn or removed from the surface using a tool. Advantageously, the pre-treatment unit can also form a common unit with the post-treatment unit. In an exemplary combined pre- and post-treatment unit, the fluid removed after the measurement has been completed can remain within the common pre- and post-treatment unit and, without transport, can be reused and reapplied from there in a subsequent, further measurement.In addition, the post-treatment unit can also be designed to clean the sample to be measured after the fluid has been removed.

[0051] The device may further comprise a control device. The control device may be designed to control and / or regulate the manipulator and / or the pretreatment and / or post-treatment unit and / or the measuring unit. The control device may further comprise further units, such as a memory unit (for example, for at least temporarily storing the recorded data from the optical measurement), an input unit for inputting data, an output unit for outputting data (such as information and / or commands), a communication unit for communicating data both from and to the control unit and / or to the individual units of the control device, and / or to other units. Communication between the individual units of the control unit and / or external units can take place via suitable interfaces, both wirelessly and wired.

[0052] The input unit may, for example, comprise a computer mouse and / or a computer keyboard and / or a touch-sensitive screen and / or another suitable input unit. The input unit may be part of the control device or connected to the control device via a suitable data connection.

[0053] The output unit can, for example, comprise at least one computer screen for outputting or displaying text and / or images and / or graphics, and / or at least one loudspeaker for outputting audio data. The output unit can be part of the control device or connected to the control device via a suitable data connection.

[0054] The device is particularly suitable for integration into a production line.

[0055] Furthermore, the device can be at least partially automated. The sequence of individual or all steps of the method performed by the device for optically measuring the at least partially transparent test specimen can be controlled and / or regulated, for example, by means of the control device.

[0056] In particular, the device can be automatically loaded with a test specimen to be measured. This can be done using a suitable manipulator. Likewise, the optical measurement(s) can be carried out automatically, and / or after the measurement has been completed, the test specimen to be measured can be automatically unloaded from the device. Accordingly, the device can have a loading unit designed to position the test specimen to be measured in the holder and / or an unloading unit designed to remove the test specimen to be measured from the holder. The loading unit and / or the unloading unit can also be implemented as separate units (for example, in a production line).The loading unit and / or unloading unit can be connected to the control device by means of a suitable data connection and can be controlled and / or regulated accordingly by the control device.

[0057] Furthermore, the device can be designed such that both surfaces of a test specimen can be measured within the device. In particular, the device can be configured to displace the test specimen such that both its first and second surfaces can be measured within the device. The displacement of the test specimen can be achieved, for example, by means of a suitable displacement device, which can be a component of the manipulator. Advantageously, the test specimen to be measured is firmly held in the holder, wherein, after the first surface of the test specimen has been measured, the holder can be tilted, rotated, or otherwise moved with the test specimen within the device.The movement (e.g., tilting or rotating) of the holder can be performed in such a way that the second surface of the specimen subsequently assumes the orientation of the first surface, allowing pretreatment of the previously first surface with a highly viscous, anti-reflective fluid. In summary, the present invention provides an improved method for optically measuring an at least partially transparent specimen and a device for carrying out such a method, in which the occurrence of disruptive secondary reflections can be reduced.

[0058] Embodiments of the method and device for optical reflection measurement are described below by way of example with reference to the accompanying figures. Individual elements of the described embodiments are not limited to the respective embodiment. Rather, elements of the embodiments can be combined with one another as desired, thereby creating new embodiments. The figures show:

[0059] Figure 1: Schematic drawing of an arrangement for carrying out the method according to the invention using a highly viscous fluid as a reflection-reducing agent in a reflection measurement,

[0060] Figure 2: Schematic drawing of a device for carrying out an optical measurement of an at least partially transparent test specimen.

[0061] Fig. 1 illustrates an embodiment for the use of the reflection-reducing, highly viscous fluid according to the invention. The arrangement shown in Figure 1 can be used to characterize a transparent test specimen 10 by means of a reflection measurement. This arrangement comprises a light source 30 which irradiates the test specimen 10 to be examined with light 40. Furthermore, the arrangement comprises a detection unit 20 (in particular as a component of a measuring unit) which is suitable for detecting light 41 reflected from the test specimen 10. In particular, the detection unit 20 can comprise means for reducing stray light, for example a stray light diaphragm or a tube. The test specimen 10 to be measured is positioned in the arrangement such that a first surface can be measured by means of the reflection measurement. For this purpose, the first surface faces the light source 30 or the detection unit 20 during the measurement.According to the method according to the invention, the test specimen 10 was provided with a reflection-reducing, highly viscous fluid 1 according to the invention on its second surface facing away from the light source before the measurement or characterization of its first surface. The fluid 1 absorbs light 42 emitted by the light source 30 and transmitted at the first surface. This advantageously enables a measurement or characterization of the first surface without disruptive reflections from the second surface impairing the result of the measurement or characterization. Without limiting the generality, the second surface can of course also be measured or characterized. For this purpose, the test specimen 10 is positioned upside down and positioned with its second surface facing the light source 30, wherein the first surface has then been provided beforehand with the reflection-reducing, highly viscous fluid 1 according to the invention.

[0062] Fig. 2 shows a schematic drawing of a device 8 for carrying out an optical measurement of an at least partially transparent test specimen 10. The optical measurement is carried out according to the method for optical measurement described above according to one aspect of the present application.

[0063] Within the device, a roller conveyor is arranged as a preferred manipulator 82, on which a holder 81 for the test specimen 10 to be measured, shown here as a spectacle lens, is arranged. The device further comprises a pretreatment unit 83. The pretreatment unit 83 is preferably implemented as a dispenser that applies a highly viscous, anti-reflection fluid to a surface of the test specimen. In addition, the device comprises a measuring unit 84. The measuring unit can be a spectrometer familiar to those skilled in the art that is designed to record a reflection measurement of the surface of the test specimen to be measured. The device further comprises a post-treatment unit 85, which is designed to remove the fluid applied by the pretreatment unit 83 from the test specimen after it has been measured.

[0064] The device further comprises a control device 80, which comprises a processor as the preferred computing unit, a hard disk as the preferred storage unit, a monitor as the preferred output unit, and a keyboard as the preferred input unit. The control device also comprises a communications unit. The control device 80 is designed to control and / or regulate the manipulator 82 and / or the pretreatment unit 83 and / or the post-treatment unit 85 and / or the measuring unit 84.

[0065] The present invention is further described by the following non-limiting examples, particularly with regard to the preparation of the anti-reflective high-viscosity fluid.

[0066] The following components are used to produce the reflection-reducing, high-viscosity fluid:

[0067] 1. A mass fraction of approximately 55% of a polymer dispersion, preferably an aqueous or solvent-based dispersion adhesive, for example, an ethyl acetate dispersion or a polyvinyl acetate dispersion. The dispersion can be carried out in water, ethanol, acetone, or a mixture thereof. However, water is preferably used exclusively, since ethanol and acetone are flammable and hazardous substances that evaporate rapidly, thereby changing the properties of the anti-reflective, highly viscous fluid and also polluting the environment.

[0068] The polymer dispersion may contain or be mixed with a benzisothiazolinone from the class of isothiazolinones, for example 1,2-benzisothiazol-3(2H)-one (CAS No. 2634-33-5), which acts as a biocide and therefore has preservative properties, in a mass fraction of less than one percent.

[0069] The polymer dispersion may also contain or be mixed with 2-(2-butoxyethoxy)ethyl acetate (CAS No. 124-17-4) in a mass fraction of less than one percent to adjust the spreadability of anti-reflective, highly viscous fluids, since it has a viscosity of 1.79 mPas and a surface tension of 28.5 mN / m at 20°C. The polymer dispersion may have a viscosity of about 4000 mPas to about 20,000 mPas, preferably about 8000 mPas to about 15,000 mPas. The above-mentioned viscosity is determined by means of the Brookfield method, preferably with a rotational viscometer (e.g., Ametek DV2T viscometer with spindle RV-5) at a temperature of 23°C and a rotation frequency of 20 rpm.

[0070] The polymer dispersion can have a density of about 0.95 g / m 3 up to about 1.1 g / m 3A mass fraction of about 26% of a foam comprising water, at least one emulsifier, at least one surfactant and at least one saccharide, in particular a monosaccharide and / or a polysaccharide.

[0071] The emulsifier can preferably contain stearic acid, a polyethylene glycol derivative (PEG derivative) or a polypropylene glycol derivative (PPG derivative) such as ceteareth-50, methyl gluceth-20 and / or laureth-23.

[0072] Preferably, the surfactant may contain sodium dodecylpolyoxyethylene sulfate (sodium laureth sulfate), sodium polynaphthalenesulfonate and / or potassium stearate.

[0073] The saccharide can preferably comprise a monosaccharide, for example galactose, glucose, xylose, mannose, mucopolysaccharide, and / or glycosaminoglycans such as aloverose or acemannan, which are contained in aloe vera juice. The saccharide can preferably comprise a polysaccharide, for example D-glucose and / or D-mannose, which are also contained in aloe vera juice. It is understood that the saccharide can also comprise a mixture of the above-mentioned monosaccharides and / or polysaccharides. The foam can preferably further comprise at least one of the following ingredients: a moisturizer, a pH adjuster, a buffering agent, a thickener, and a preservative.

[0074] Preferably, the moisturizer may contain glycerin, palmitic acid and / or coco-caprate or a mixture thereof.

[0075] Preferably, triethanolamine can be contained in the foam as a pH regulator. More preferably, potassium hydroxide can be contained in the foam as a buffer substance. More preferably, xanthan gum and / or water-soluble cellulose or hydroxypropyl methylcellulose can be contained in the foam as a thickener. A mass fraction of about 10% of a diluent, in particular an aqueous solution or water. Preferably, the aqueous solution can be a solution of sodium chloride, in particular with a mass fraction of about 9 g per liter of water, or a Ringer's solution (Solutio Ringeri). The diluent can contain at least one preservative. For example, the aqueous solution can contain sodium edetate (EDTA) and / or polyhexanide or polyamethylene biguanide or polyamethylene biguanide (PHMB), in particular with a concentration of about 0.0001% to 0.001%.The diluent may contain at least one gelling agent, such as hyaluronic acid, preferably in a concentration of about 0.2% to about 2%. A mass fraction of about 9% of a paint, in particular an acrylic paint, which contains at least one pigment in addition to at least one copolymer and water as a carrier substance. The paint may have a density of about 1.05 to about 1.35 g / cm³. 3The at least one pigment or pigment mixture is designed to absorb light at a specific wavelength, preferably to a proportion of more than 50%, particularly preferably to a proportion of more than 75%, and in particular to a proportion of more than 90% or more than 95%. The specific wavelength can, for example, be visible light in a wavelength range from 380 nm to 800 nm or from 400 nm to 780 nm. However, only the wavelength ranges used for measuring a transparent body can be absorbed, for example ultraviolet light (UV-C: 100 to 280 nm, UV-B: 280 to 315 nm and / or UV-A: 315 to 380 nm), violet light with 380-450 nm, blue light with 450-495 nm, green light with 495-570 nm, yellow light with 570-590 nm, orange light with 590-620 nm, red light 620-750 nm, infrared light (IR-A: 780 to 1400 nm and / or IR-B: 1400 to 3000 nm) or mixtures thereof.Preferably, the at least one pigment can be iron oxide black or carbon black or the pigment mixture can comprise at least one or both of the aforementioned pigments.

[0076] The aforementioned mass fractions are subject to slight variation, for example, to adjust the viscosity of the anti-reflective, highly viscous fluid without impairing its anti-reflective effect. Thus, the specified mass fractions can vary by approximately 5 to 10% of the stated mass fraction, so that the sum of all mass fractions again equals 100%.

[0077] A preferred composition of the reflection-reducing, highly viscous fluid can be made from easily obtainable and ecologically and health-safe ingredients. The polymer dispersion used can be (1) a white glue, which is available as a commercially available craft glue or wood glue, for example, under the brand name "PONAL" from Henkel; (2) a shaving foam, which is available, for example, under the brand name "Isana" as "Shaving Foam Sensitive with Aloe Vera" from dm; (3) a contact lens combination solution, which is available, for example, under the brand name "visiomax" Contact Lens Care Combination Solution for Soft Contact Lenses from dm; and (4) a black acrylic paint, which is available, for example, under the brand name "AKADEMIE" as "Acryl color - 23000 - Fine Artist Acrylic Paint" from Schmincke.To prepare the anti-reflective, highly viscous fluid, mix 17 g of shaving foam with 37 g of craft glue in a glass bowl until a viscous mass forms. A teaspoon (equivalent to approximately 6 g) of paint is added to this mixture and spread evenly. Finally, 7 g of the combined solution is slowly added and mixed until the mixture easily separates from the bowl while stirring.

[0078] The mass thus obtained is left to stand in the air for one day with occasional stirring in order to dry or thicken, in particular to achieve a desired viscosity of approximately 10,000 mPas to 100,000 mPas, and is then stored in an airtight container.

[0079] Preferred embodiments of the invention have been described above using examples. Individual elements of the described embodiments are not limited to the respective embodiment. Rather, elements of the embodiments can be combined with one another in any desired way, thereby creating new embodiments. Furthermore, individual features can be modified.

[0080] List of reference symbols

[0081] 1 highly viscous fluid

[0082] 8 Device for carrying out an optical measurement

[0083] 10 test specimens

[0084] 20 detection units

[0085] 30 light source

[0086] 40 light

[0087] 41 reflected light

[0088] 42 transmitted light

[0089] 80 Control device

[0090] 82 Manipulator

[0091] 83 Pretreatment unit

[0092] 84 measuring unit

[0093] 85 Aftertreatment unit

Claims

Claims: A method for the optical measurement of an at least partially transparent test specimen (10) with an optically effective first surface and an opposing second surface, wherein the method is carried out in reflection geometry, in particular automatically, and comprises the following steps: i) applying a highly viscous, reflection-reducing fluid to the second surface of the test specimen (10); ii) performing the optical measurement; and iii) removing the reflection-reducing, highly viscous fluid. The method according to claim 1, wherein the highly viscous fluid has a viscosity in the range of 10,000 mPas to 100,000 mPas. The method according to claim 1 or 2, wherein the highly viscous fluid has a refractive index that differs by less than 10% from the refractive index of the test specimen (10).A method according to any one of claims 1 to 3, wherein, for optical measurement of the test specimen (10) in reflection geometry, light is shone onto the first surface side of the test specimen (10) and the highly viscous fluid absorbs at least 75% of the light passing through the test specimen (10). A method according to any one of claims 1 to 4, wherein the highly viscous fluid has a surface tension of less than 62.5 mN / m. A method according to any one of claims 1 to 5, wherein the highly viscous fluid is water-soluble. A method according to any one of claims 1 to 6, wherein the test specimen (10) consists of mineral glass. A method according to any one of claims 1 to 7, wherein the test specimen (10) is a semi-finished or finished product of an optical lens, in particular a spectacle lens. A method according to any one of claims 1 to 8, wherein the second surface of the test specimen (10) is also optically active. Use of a reflection-reducing highly viscous fluid comprising: a mass fraction of 49% to 61% of a polymer dispersion, a mass fraction of 23% to 30% of a foam, a mass fraction of 9% to 11% of a diluent, and a mass fraction of 8% to 10% of a colorant, wherein the sum of all mass fractions equals 100%, in a method according to any one of claims 1 to 9.Device (8) for carrying out a method for the optical measurement of an at least partially transparent test body (10) with an optically effective first surface and an opposing second surface in reflection geometry according to one of claims 1 to 9, wherein the device comprises: a receptacle for the test body (10) to be measured; a manipulator (82); a pretreatment unit (83) which is configured to apply the highly viscous, reflection-reducing fluid to a second surface opposite the first surface of the test body (10); a measuring unit (20, 84) which is configured to Reflectance measurement by irradiating a measurement position on the surface The device (8) is configured to capture the sample body (10) to be measured with light (40) and to detect at least a portion of the light (41) reflected by the sample body (10) during irradiation; a post-treatment unit (85) configured to detach the highly viscous, reflection-reducing fluid located on the second surface of the sample body to be measured. The device (8) according to claim 11, wherein the device further comprises a control device (80) configured to control and / or regulate the manipulator (82) and / or the pre-treatment unit (83) and / or the post-treatment unit (85) and / or the measuring unit (84). The device (8) according to claim 11 or 12, wherein the device further comprises a loading unit configured to position the sample body (10) to be measured in the receptacle.Device (8) according to any one of claims 11 to 13, wherein the device further comprises a discharge unit configured to remove the test specimen (10) to be measured from the receptacle. Device (8) according to any one of claims 11 to 14, wherein the device is configured to reposition the test specimen (10) such that both its first and second surfaces can be measured within the device (8).

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