Reflectometer employing an integrating sphere and lens-mirror concentrator

Claim 1

A reflectometer for measuring the reflectance of a sample comprising: a light source for generating a light beam having a plurality of wavelengths; means for selecting a predetermined wavelength to be projected onto the sample from the plurality of wavelengths generated by the light source; an integrating sphere; means for projecting the predetermined wavelength of light onto a sample located within the integrating sphere where it is reflected in a plurality of directions off the sample onto the wall of the integrating sphere where the reflected light is again reflected; the integrating sphere being further comprised of a detector for measuring the quantum of light reflected off the sample, a non-imaging concentrator having a hyperbolic mirror directing the reflected light from the sample onto the detector and one or more baffles to shield the concentrator from first reflections of the light off of the sample thereby forming a viewable field which is less than the maximum field-of-view of the concentrator; means for determining the reflectance of the sample based upon a quantum of light reflected off the sample; and means for displaying the reflectance of the sample.

Claim 19

A method for determining a total reflectance of a sample comprising the steps of: selecting a wavelength of a light beam to be projected onto a sample located within an integrating sphere whose reflectivity is to be determined; projecting the light into the integrating sphere through a spectrophotometer onto the sample; collecting a reflected light from the sample and the walls of the integrating sphere projected onto a cap radius, F, of the integrating sphere with a concentrator having a predetermined field-of-view; measuring the reflected light collected by the concentrator to ascertain a reflectance of the sample at the preselected wavelength; repeating the step of selecting the wavelength of the light to be projected into the integrating sphere by varying the preselected wavelength over a predetermined plurality of wavelengths; analyze the plurality of reflectivity measurements to obtain the total reflectance of the sample for the predetermined plurality of wavelengths; projecting a light beam through the spectrophotometer onto a standard reference material inside the integrating sphere and obtain a calibration factor for the integrating sphere by comparing the standard reflectance of the standard reference material to the reading of a calibration reflectance; correct the total reflectivity by applying the correction factor; and display the corrected total reflectance of the sample on a display.

Claim 20

A method for determining a total reflectance of a sample comprising the steps of: selecting a wavelength of a light beam to be projected onto a sample located within an integrating sphere whose reflectivity is to be determined; projecting the light into the integrating sphere through a spectrophotometer onto the sample; collecting a reflected light from the sample and the walls of the integrating sphere projected onto a cap radius, F, of the integrating sphere with a concentrator having a predetermined field-of-view; measuring the reflected light collected by the concentrator to ascertain a reflectance of the sample at the preselected wavelength; repeating the step of selecting the wavelength of the light to be projected into the integrating sphere by varying the preselected wavelength over a predetermined plurality of wavelengths; analyze the plurality of reflectivity measurements to obtain the total reflectance of the sample for the predetermined plurality of wavelengths; projecting a light beam through the spectrophotometer onto a standard reference material inside the integrating sphere and obtain a calibration factor for the integrating sphere by comparing the standard reflectance of the standard reference material to the reading of a calibration reflectance; correct the total reflectivity by applying the correction factor; and display the corrected total reflectance of the sample on a display.