Auto ICR with built in IR pass filter
About the camera lenses for security or intelligent traffic system, there is a problem of focus shift in visible light and near infrared light. This focus shift occurs due to longitudinal chromatic aberration, specifically it occurs because the focal length of visible light and near-infrared light are different.
IR-corrected lenses are one of the solution to this problem, but the optical design of IR correction is difficult on the high magnification zoom lenses. Therefore, in order to achieve IR correction on the high zoom ratio, some additional optical and mechanical support structures are required in addition to the optical design. Furthermore IR corrected lenses need expensive low dispersion glass (LD glass), these factors affect the cost of the final product.
Another solution is auto ICR (IR cut filter removable) with built-in IR pass filter. For regular auto ICR, IR cut filter is used in the daytime and dummy glass for the nighttime. We replace dummy glass with IR pass filter to obtain sharp black and white images during evening (mixed light situation) and nighttime surveillance. The IR pass filter allows IR light to pass through, but blocks visible light. When IR illuminator is used for nighttime surveillance, this solution works effectively. Specifications of built-in filter (wavelength, transmittance range) can be met according to each customer’s request.
Auto ICR by combination of IR cut filter and IR pass filter
850nm IR pass filter transmittance graph
