Optisk sensoranordning och förfarande för att reglera dess exponeringstid

摘要

An optical sensor device (10) has an illuminating light source (13) and an image sensor (14). The image sensor (14) captures a sequence of images under exposure of light from the light source (13). A controller (30) in the optical sensor device (10) has a control output and generates an exposure time control signal on the control output. The controller (30) includes an exposure time control loop. Each iteration of the loop includes the steps: calculating an error between a set value and an actual luminance condition value determined in a current image in the sequence of images; calculating a current exposure time as a function of the error and an exposure time calculated during the preceding iteration of the control loop; and generating the exposure time control signal on the control output based on the current exposure time. The exposure time may thereby be determined so as to yield optimum contrast in an image which is to be captured by the image sensor (14).