1. Technical Field
The present invention relates to lens modules, and more particularly to a lens module that is capable of performing infrared and visible-spectrum photography.
2. Description of Related Art
Nowadays, camera modules are now in widespread use. Camera modules are being combined with various portable electronic devices such as mobile phones, PDAs (personal digital assistants) and computers to be increasingly multi-functional.
A typical camera module generally includes a lens module. The lens module is a very important component of the camera module. The lens module is coupled with an image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) so as to capture images. Generally speaking, the image sensor reacts to light both in the visible spectrum and in the infrared spectrum. Light in the infrared spectrum can cause interference that causes the image sensor signal-to-noise ratio to be reduced, when the lens module is used in natural light conditions for visible-spectrum photography. Therefore, an infrared-cut filter that blocks light in the infrared spectrum is fitted in the lens module to prevent such interference.
However, such lens module having an infrared-cut filter fitted therein is only capable of performing visible-spectrum photography. Thus use of the lens module is restricted to some extent. For example, such a lens module cannot ideally be used in dark environments for photography because of the lack of visible-spectrum. Although infrared is emitted by all objects all the time, even in dark environments, the lens module cannot be used for infrared photography due to infrared light being blocked by the infrared-cut filter.
What is needed, therefore, is a lens module that is capable of performing both infrared and visible-spectrum photography.