Method and apparatus for monitoring a spectral radiometer
The invention relates to a method for monitoring a spectroradiometer ( 4 ), in particular for measuring light-emitting test objects ( 1 ), in which the spectral data of the test objects ( 1 ) are captured by means of an optical system, wherein the radiometric, photometric and/or colorimetric quantities of the test objects ( 1 ) are ascertained from the spectral data. The problem addressed by the invention is that of specifying a method for monitoring a spectroradiometer ( 4 ), where it is not the continuous recalibration of the spectroradiometer ( 4 ) but the monitoring of when a calibration is necessary that is paramount. The invention solves this problem by virtue of changes in the wavelength scale, in the light throughput and/or in the spectral sensitivity of the spectroradiometer ( 4 ) being detected by way of a reference light source ( 5 ), integrated into the optical system, with a defined spectrum. Optionally, at least one detector integrated into the optical system can additionally monitor the stability of the reference light source ( 5 ). Moreover, the invention relates to a device for carrying out the method.
1. A method for monitoring a spectroradiometer ( 4 ) used to measure light-emitting test objects ( 1 ), in which the spectral data of the test objects ( 1 ) are acquired by means of an optical system, wherein radiometric, photometric and/or colorimetric variables of the test objects ( 1 ) are determined from the spectral data, wherein changes in the wavelength scale, in the light throughput and/or in the spectral sensitivity of the spectroradiometer ( 4 ) are detected by a reference light source ( 5 ) integrated in the optical system and wherein the light of the test object (I) is received by the optical system as the receiving optics, which comprises a measuring head ( 3 ) that is connected to the spectroradiometer ( 4 ) via an optical connection, as well as an objective ( 51 ) and an image sensor ( 52 ), wherein a portion of the light of the test object ( 1 ) is supplied to the spectroradiometer ( 4 ) by means of a beam splitter ( 53 ) via the optical connection and wherein the reference light source ( 5 ) is integrated in the measuring head ( 3 ) and has a known spectrum by means of which the calibration of the spectroradiometer is monitored, wherein the stability of the reference light source ( 5 ) is monitored by means of the image sensor ( 52 ).
2. The method according to claim 1 , wherein the reference light source ( 5 ) is an LED having a precision power source ( 6 ).
3. The method according to claim 1 , wherein the reference light source ( 5 ) is operated such that it stabilizes in a thermodynamic equilibrium.
4. The method according to claim 1 , wherein the reference light source ( 5 ) is operated in a pulsed manner.
5. The method according to claim 1 , wherein a white LED is used as the reference light source ( 5 ).
6. A device for monitoring a spectroradiometer ( 4 ) used to measure light-emitting test objects ( 1 ), comprising a spectroradiometer ( 4 ) and an optical system, coupled to said spectroradiometer ( 4 ), as receiving optics for light originating from a test object ( 1 ), wherein a reference light source ( 5 ) is integrated into the receiving optics, wherein the receiving optics further comprise a measuring head ( 3 ) that is connected to the spectroradiometer ( 4 ) via an optical connection, as well as an objective ( 51 ) and an image sensor ( 52 ), wherein a beam splitter ( 53 ) is configured to supply a portion of the light of the test object ( 1 ) to the spectroradiometer ( 4 ) via the optical connection, and wherein the reference light source ( 5 ) is integrated in the measuring head ( 3 ) and has a known spectrum by means of which the calibration of the spectroradiometer is monitored.
7. The device according to claim 6 , wherein the reference light source ( 5 ) is an LED.
8. The device according to claim 6 , wherein the optical connection is configured as an optical fiber.
9. The device according to claim 6 , wherein the image sensor ( 52 ) is a CCD image sensor ( 52 ).
10. The device according to claim 6 , wherein the reference light source ( 5 ) is temperature-stabilized and is operated by means of a precision power source ( 6 ).