Processes and devices for the photothermal inspection of a test body
First Claim
1. Process for photothermally inspecting a test specimen in which the test specimen (58) is acted on by luminous radiation (65) in an illumination region (66) during an illumination time and thermal radiation (70) emitted by the test specimen (58) from a detection region (69) is detected, wherein properties of the test specimen (58) are determined from the chronological course of the thermal radiation (70), which can be represented by means of an emissions curve that has a heating part with an increasing amplitude and a cooling part with a decreasing amplitude, characterized in that at least two illumination times (tp) are adjusted, which are less than the quotient of the square of an estimated value of a layer thickness constituted by the distance between boundary surfaces and an estimated value for the diffusivity between the boundary surfaces, in that the illumination region (66) and the detection region (69) are spaced apart from each other with a diffusion spacing, in that the maximal amplitudes are determined for each emissions curve, which maximal amplitudes occur for each illumination time in the detection region, with associated adjustment times, and in that the diffusivity is determined from the ratio between at least two maximal amplitudes, the diffusion spacing, and the associated adjustment times.
1 Assignment
0 Petitions
Accused Products
Abstract
Processes and devices for the photothermal inspection of a test body. Lighting radiation with short lighting times is applied to a test body and at least one measurement value of the emission curve during or after a short lighting time is sensed. The diffusion and/or effusion capacity of a test body coating layer, for example, can be determined by computer units on the basis of the measurement value(s), even when the thickness of the coating layer is unknown, because the measurement values are detected during or shortly after irradiation and the coating layer thickness plays only an insignificant role in the course of the emission curve in this range.
61 Citations
12 Claims
- 1. Process for photothermally inspecting a test specimen in which the test specimen (58) is acted on by luminous radiation (65) in an illumination region (66) during an illumination time and thermal radiation (70) emitted by the test specimen (58) from a detection region (69) is detected, wherein properties of the test specimen (58) are determined from the chronological course of the thermal radiation (70), which can be represented by means of an emissions curve that has a heating part with an increasing amplitude and a cooling part with a decreasing amplitude, characterized in that at least two illumination times (tp) are adjusted, which are less than the quotient of the square of an estimated value of a layer thickness constituted by the distance between boundary surfaces and an estimated value for the diffusivity between the boundary surfaces, in that the illumination region (66) and the detection region (69) are spaced apart from each other with a diffusion spacing, in that the maximal amplitudes are determined for each emissions curve, which maximal amplitudes occur for each illumination time in the detection region, with associated adjustment times, and in that the diffusivity is determined from the ratio between at least two maximal amplitudes, the diffusion spacing, and the associated adjustment times.
-
11. Device for photothermally inspecting a test specimen, in particular by carrying out a process for photothermally inspecting a test specimen in which the test specimen is acted on by luminous radiation in an illumination region during an illumination time and thermal radiation emitted by the test specimen from a detection region is detected in a time-resolved manner, wherein properties of the test specimen are determined from the chronological course of the thermal radiation, which can be represented by means of an emissions curve, which has a heating part with an increasing amplitude and a cooling part with a decreasing amplitude, characterized in that an illumination time is adjusted, which is less than the quotient of the square of an estimated value of a layer thickness constituted by the distance between boundary surfaces and an estimated value for the diffusivity between the boundary surfaces, and that the effusivity of the test specimen is determined from at least one measurement value disposed in the heating part or in a section of the cooling part immediately following the heating part, which has a high cooling rate that corresponds to a heating rate of the heating part,
the device having an illumination device which can act on the test specimen with luminous radiation in an illumination region during an illumination time, having a detection device which can carry out a time-resolved detection of thermal radiation emitted by the test specimen from a detection region, and having a control and evaluation device which can determine properties of the test specimen from the chronological course of the thermal radiation, which can be represented by means of an emissions curve, which has a heating part with an increasing amplitude and a cooling part with a decreasing amplitude, characterized in that the illumination device can be used to adjust at least one illumination time, which is less than the quotient of the square of an estimated value of a layer thickness constituted by the distance between boundary surfaces and an estimated value for the diffusivity between the boundary surfaces, and that a calculation unit is provided, which can be used to determine the effusivity of the test specimen from at least one measurement value disposed in the heating part or in a section of the cooling part immediately following the heating part, which has a high cooling rate that corresponds to a heating rate of the heating part, characterized in that the detection unit can be used to detect a number of measurement values disposed in the heating part and/or in the section of the cooling part of the emissions curve immediately following the heating part, further characterized in that a model parameter memory is provided, which can store as parameters predetermined values for a thermal conductivity and the product of density and specific heat capacity of a substrate, as well as an estimated value for an effusivity and an estimated value for a layer thickness of a coating of the test specimen, in that a heat energy measuring unit is provided, which can establish a heat energy measuring parameter value associated with the energy of the luminous radiation acting on the test specimen, in that a short-term emissions model curve calculation unit is provided with which initial emissions model curves— - which contain measurement values that are established for determining the effusivity—
can be calculated by means of the heat energy measurement parameter value and the other predetermined parameters, with variation of the effusivity in the vicinity of the associated estimated value in at least one of the sections of the emissions curves, and that a short-term emissions curve comparison unit can determine the initial emissions model curve, which can be determined with the corresponding effusivity and has the least deviations from the measurement values.
- which contain measurement values that are established for determining the effusivity—
-
12. Device for photothermally inspecting a test specimen, in particular by carrying out a process for photothermally inspecting a test specimen in which the test specimen is acted on by luminous radiation in an illumination region during an illumination time and thermal radiation emitted by the test specimen from a detection region is detected in a time-resolved manner, wherein properties of the test specimen are determined from the chronological course of the thermal radiation, which can be represented by means of an emissions curve, which has a heating part with an increasing amplitude and a cooling part with a decreasing amplitude, characterized in that an illumination time is adjusted, which is less than the quotient of the square of an estimated value of a layer thickness constituted by the distance between boundary surfaces and an estimated value for the diffusivity between the boundary surfaces, and that the effusivity of the test specimen is determined from at least one measurement value disposed in the heating part or in a section of the cooling part immediately following the heating part, which has a high cooling rate that corresponds to a heating rate of the heating part,
the device having an illumination device which can act on the test specimen with luminous radiation in an illumination region during an illumination time, having a detection device which can carry out a time-resolved detection of thermal radiation emitted by the test specimen from a detection region, and having a control and evaluation device which can determine properties of the test specimen from the chronological course of the thermal radiation, which can be represented by means of an emissions curve, which has a heating part with an increasing amplitude and a cooling part with a decreasing amplitude, characterized in that the illumination device can be used to adjust at least one illumination time, which is less than the quotient of the square of an estimated value of a layer thickness constituted by the distance between boundary surfaces and an estimated value for the diffusivity between the boundary surfaces, and that a calculation unit is provided, which can be used to determine the effusivity of the test specimen from at least one measurement value disposed in the heating part or in a section of the cooling part immediately following the heating part, which has a high cooling rate that corresponds to a heating rate of the heating part, characterized in that the detection unit can be used to detect a number of measurement values disposed in the in the section of the cooling part immediately following the heating part, up to a multiple of the duration of the heating part, further characterized in that a long-term emissions model curve calculation unit is provided, which can use the predetermined parameters to calculate the sections of the cooling parts of a number of cooling model curves in which the measurement values lie, and that a long-term emissions curve comparison unit can determine the cooling model curve with the least deviations from the measurement values.
Specification