Patent ID: 8301399

Claim:
A method for predicting, based on the degradation tendency of a photo-semiconductor device, the lifetime of the photo-semiconductor device that outputs light at light output values including a maximum light output value that is restricted by thermal saturation, the method comprising using one or more processors to perform the steps of: extracting the maximum light output value of the photo-semiconductor device by measuring the characteristic of light output from the photo-semiconductor device with respect to drive current; repeating the step of extracting the maximum light output value of the photo-semiconductor device at least once, thereby extracting a plurality of maximum light output values of the photo-semiconductor device at a plurality of extraction points in total; calculating a degradation curve that approximates the characteristic of the maximum light output values with respect to drive time periods that have passed after initially driving the photo-semiconductor device; calculating, based on the degradation curve, a drive time period at which the maximum light output value on the degradation curve and a drive light output value that is set in a drive apparatus of the photo-semiconductor device become the same; and predicting that the calculated drive time period is the lifetime of the photo-semiconductor device.