Patent ID: 7365329

Claim:
A method for determining location of an infrared-cut (IR-cut) filter film on a substrate, the filter film and the substrate cooperatively functioning as an IR-cut filter, the method comprising the steps of: providing an infrared laser device, the filter and an infrared laser sensor, the IR-cut filter being arranged between the IR laser device and the IR laser sensor, the IR laser device and the IR laser sensor being aligned with each other; emitting an infrared laser beam from the IR laser device to a surface of the IR-cut filter in a manner such that the infrared laser beam is obliquely incident on an edge portion of the IR-cut filter at an incident angle θ, and a width L of the infrared laser beam satisfies the following equation: L=D× sin θ, wherein, D represents a thickness of the substrate; and determining the location of the filter film on the substrate in such a way that, if a light intensity of the infrared laser beam received by the infrared sensor is equal to or close to zero, the IR-cut filter film is on a surface of the substrate facing the infrared laser device, if the light intensity of the infrared laser beam received by the infrared sensor is equal to or close to a light intensity of the infrared laser beam emitted from the infrared laser device, the filter film is located on a surface of the substrate facing towards the infrared laser sensor.