Patent ID: 7205154

Claim:
A method using a chemical array reader having: i) a holder to mount an array and hold the array at a reading position; ii) a light system to illuminate a mounted array when at a reading position; iii) a detection system having a focal plane, to detect light from different regions across the array emitted in response to the illumination, when at the reading position, and which generates a resulting signal for each of the regions across the array; and iv) an autofocus system which detects and reduces offset between the different regions of an array at the reading position and a determined position of the focal plane; the method comprising: a) positioning a calibration member having a uniform fluorescent layer at the reading position so as to receive illumination from the light system and emit light in response thereto, which emitted light is detected by the detection system to generate a resulting calibration signal; b) adjusting a position of the calibration member, when in the reading position, relative to the focal plane; c) determining the position of the focal plane from the light detected at various adjustments; and d) calibrating a sensitivity of the detection system from the detection system signals generated from the calibration member.