It is the IR-cut filter. I can give you the Raspberry Pi HQ camera’ IR filter spec.
The red filter used in the Raspberry Pi HQ camera has a circular shape with a diameter of 27.8mm and a thickness of 2.0mm. The filter blocks visible light and allows only infrared light to pass through, with a wavelength range of 700-1100nm and high transmittance within this range. Compared to the red filter used in the standard Raspberry Pi camera, the one used in the HQ camera has a slightly larger diameter but the same thickness, to accommodate the higher pixel count of the HQ camera's image sensor. It's important to note that the red filter used in the Raspberry Pi HQ camera has a different specification compared to the one used in the standard Raspberry Pi camera, so it's important to choose the correct filter based on the specific camera model and version being used. Could you please take a moment to review the highlighted lines? If you notice any errors, please let me know. Currently, we are using a customizable M12 Lens with an IR Cut filter in the Arducam IMX477 12MP High-Quality Camera. May I know what is the difference between an integral IR cut filter (Arducam module) and an IR cut-off filter in the lens? Regards Sakthinathan S