IR Cut-Off Filters

IR-Cut in our System

I was first noticed of the IR Cut-Off Filter by the sensor board connector schematic diagram:

IMX178 Sensor Board Pinout Diagram

Pin 35 and Pin 36 illustrate IRCUT_CONTROL, which do NOT have any connections with the IMX chip. Reminded by the sensor board retailer, I went on search engine, and realised that IR_CUT filters mechanism is widespread in network / security camera.

In short, the two IRCUT pins are to be connected to a dedicate IRCUT filter mechanism to switch between IR-Cut filter and all-pass (not sure about the name) filter.

What is IR-Cut?

There is a nice article about IR-Cut:

What’s IR-Cut infrared security camera ?

IR-Cut security camera is the security camera has a IR-CUT filter built-in to make camera provide true color reproduction high quality image at day and night. The function of IR-cut in security camera is fixing the color distortion, meanwhile maintaining good light sensitivity at night.

When a security camera works at day, people want to get the accurate color images, the equipped IR-cut filter will block the infrared light (from outside), so infrared light will not enter into the image sensor (CMOS/CCD). If the infrared light enters to the image sensor at day, it will interfere the color reproduction.

Here is a Chinese version.

Effect of IR-Cut

Source for IR-Cut

For easy integration, there are lots of existing IRCUT solution on taobao: Search IRCUT on taobao, at very affordable price.

Also, alternatively, there are also IR-Cut Filters available for us, such as:

Taobao:可见光滤光片高 可见光高透红外截止通光片 400-700nm通过滤波片

or

Edmund

IR Cut-Off Filters

Sunex Inc.

Connection Details

imx178_lv_refb_vera_Page_5

It appears that the control is simply GPIO, which then go through power amplifier for mechanical controls.

Bottom Line

As we are not shooting at night, we do not need a switchable IR-Cut mechanism. But purchasing an IR-Cut filter itself for our system seems necessary. As it improves image quality by a lot.

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