# US 2017/0285186 A1 · X-ray detector, imaging apparatus and calibration method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0285186 A1 - Document ID: US20170285186A1 - Status: Published application - Kind: A1 - Application number: 15/114,444 - Filed: 2015-12-09 - Published: 2017-10-05 - Earliest claimed: 2014-12-11 - Assignees: Koninklijke Philips N.V. - Applicants: Koninklijke Philips N.V. - Inventors: Ewald ROESSL; Heiner DAERR - Web page: https://patentgrep.com/patent/US20170285186A1 ## CPC - G01T 1/24: with semiconductor detectors - A61B 6/585: {Calibration of detector units} - G01T 7/005: {calibration techniques (stabilization of spectrometer G01T1/40)} - H05G 1/08: Electrical details - H01J 35/02: Details - G01T: MEASUREMENT OF NUCLEAR OR X-RADIATION (radiation analysis of materials, mass spectrometry G01N23/00; tubes for determining the presence, intensity, density or energy of radiation or particles H01J47/00) - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - H05G: X-RAY TECHNIQUE (investigating or analysing materials by the use of X-rays G01N23/00; apparatus for X-ray photography G03B42/02; X-ray tubes H01J35/00; TV systems having X-ray input H04N5/321) - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract The present invention relates to an X-ray detector comprising a directly converting semiconductor layer (60) having a plurality of pixels for converting incident radiation into electrical measurement signals with a band gap energy characteristic of the semiconductor layer, wherein said incident radiation is x-ray radiation emitted by an x-ray source (2) or light emitted by at least one light source (30, 33). Further, an evaluation unit (67) is provided for calculating evaluation signals per pixel or group of pixels from first electrical measurement signals generated per pixel or group of pixels when light from said at least one light source at a first intensity is coupled into the semiconductor layer and second electrical measurement signals generated per pixel or group of pixels when light from said at least one light source at a second intensity is coupled into the semiconductor layer, wherein said evaluation unit is configured to detect per pixel or group of pixels a noise peak in said first and second electrical measurement signals and to determine offset and gain per pixel or group of pixels from the detected noise peaks. A detection unit (69) is provided for determining detection signals from electrical measurement signals generated when x-ray radiation is incident onto the semiconductor layer, and a calibration unit (68) is provided for calibrating the detection unit on the basis of the evaluation signals. ## Claims ### Claim 1 X-ray detector comprising: a directly converting semiconductor layer having a plurality of pixels for converting incident radiation into electrical measurement signals with a band gap energy characteristic of the semiconductor layer, wherein said incident radiation is x-ray radiation emitted by an x-ray source or light emitted by at least one light source said light having an energy above the band gap energy of the semiconductor layer for the simulation of incident x-ray quanta, an evaluation unit for calculating evaluation signals per pixel or group of pixels from first electrical measurement signals generated per pixel or group of pixels when light from said at least one light source at a first intensity is coupled into the semiconductor layer and second electrical measurement signals generated per pixel or group of pixels when light from said at least one light source at a second intensity is coupled into the semiconductor layer, wherein said evaluation unit is configured to detect per pixel or group of pixels a noise peak in said first and second electrical measurement signals and to determine offset and gain per pixel or group of pixels from the detected noise peaks, a detection unit for determining detection signals from electrical measurement signals generated when x-ray radiation is incident onto the semiconductor layer, and a calibration unit for calibrating the detection unit on the basis of the evaluation signals. ### Claim 2 (depends on 1) X-ray detector as claimed in claim 1, wherein said evaluation unit is configured to perform a threshold scan to obtain said first and second electrical measurement signals. ### Claim 3 (depends on 2) X-ray detector as claimed in claim 2, wherein said evaluation unit is configured to determine the offset per pixel or group of pixels from the absolute threshold value of the noise peak in a threshold scan performed to obtain said first electrical measurement signals. ### Claim 4 (depends on 2) X-ray detector as claimed in claim 2, wherein said evaluation unit is configured to determine the gain per pixel or group of pixels from the absolute difference in the threshold values of the noise peak in a first threshold scan performed to obtain said first electrical measurement signals and a second threshold scan performed to obtain said second electrical measurement signals and from the intensity level of the light coupled into the semiconductor layer during the generation of the first and second electrical measurement signals. ### Claim 5 (depends on 1) X-ray detector as claimed in claim 1, wherein said evaluation unit is configured to calculate evaluation signals per pixel or group of pixels from at least three electrical measurement signals generated per pixel or group of pixels when light from said at least one light source at three different intensities is coupled into the semiconductor layer. ### Claim 6 (depends on 1) X-ray detection apparatus comprising: an x-ray detector as claimed in claim 1 and at least one light source for coupling light into the semiconductor layer, wherein the generated light, for the simulation of incident x-ray quanta, has an energy above the band gap energy of the semiconductor layer. ### Claim 7 (depends on 6) X-ray detection apparatus as claimed in claim 6, comprising a single light source for coupling light into the semiconductor layer. ### Claim 8 (depends on 6) X-ray detection apparatus as claimed in claim 6, comprising a plurality of light sources in particular a single light source per pixel or group of pixels, for coupling light into the semiconductor layer. ### Claim 9 (depends on 6) X-ray detection apparatus as claimed in claim 6, further comprising beam widening optics and/or beam guiding optics for beam widening and/or beam guiding of the light emitted from said at least one light source onto the semiconductor layer. ### Claim 10 (depends on 6) X-ray detection apparatus as claimed in claim 6, wherein said at least one light source is arranged outside of the path of the x-ray radiation beam. ### Claim 11 (depends on 9) X-ray detection apparatus as claimed in claim 9, comprising one or more removable or displaceable mirrors fiber optics, diffraction gratings for diffracting the light onto the pixels of the semiconductor layer and/or lenses. ### Claim 12 (depends on 6) X-ray detection apparatus as claimed in claim 6, wherein said at least one light source is configured for pulsed or continuous emission of light. ### Claim 13 (depends on 6) Imaging apparatus comprising: a radiation source for emitting radiation through an imaging area, an x-ray detection apparatus as claimed in claim 6 for detecting radiation from said imaging area, a gantry to which at least said x-ray detector is mounted and which allows rotation of said x-ray detector around said imaging area, and a controller for controlling said x-ray detection apparatus to detect radiation at a plurality of projection positions during rotation around said imaging area. ### Claim 14 Calibration method for calibrating an x-ray detector comprising a directly converting semiconductor layer having a plurality of pixels for converting incident radiation into electrical measurement signals with a band gap energy characteristic of the semiconductor layer and at least one light source for coupling light into the semiconductor layer, wherein the generated light, for the simulation of incident x-ray quanta, has an energy above the band gap energy of the semiconductor layer, said method comprising: acquiring first electrical measurement signals generated per pixel or group of pixels when light from said at least one light source at a first intensity is coupled into the semiconductor layer, acquiring second electrical measurement signals generated per pixel or group of pixels when light from said at least one light source at a second intensity is coupled into the semiconductor layer, calculating evaluation signals per pixel or group of pixels from the acquired first electrical measurement signals and the acquired second electrical measurement signals by detecting per pixel or group of pixels a noise peak in said first and second electrical measurement signals and determining offset and gain per pixel or group of pixels from the detected noise peaks, determining detection signals from electrical measurement signals generated when x-ray radiation is incident onto the semiconductor layer, and calibrating the x-ray detector on the basis of the evaluation signals. ### Claim 15 (depends on 14) Computer program comprising program code means for causing a computer to control an imaging apparatus to carry out the steps of the method as claimed in claim 14 when said computer program is carried out on the computer.