Back exposure

Backside illuminated (English: backside illumination , BSI ) is a structural variant in the construction of solid state image sensors .

CCD for UV, viewing window on the underside of the chip

technology

After passing through the camera optics, the light hits the light-sensitive silicon crystal directly and from behind, while with the front side illumination variant, the light first passes the area of ​​the metallization layers before it generates electrical charges in the silicon.

CCD in front side illumination

As a result, part of the active surface is “in the shadow” and the sensor is less sensitive. With the first CMOS sensors, more area was covered by the wiring than with a CCD ; changing the exposure direction is more effective than with the more sensitive CCD.

Areas of application

BSI technology is used for both CMOS and CCD sensors. While front side illumination was previously dominant in commercially available digital cameras, back side illumination (BSI) was reserved for special applications such as astronomy, especially in the area of ultraviolet light (compare front and back-side illuminated ). There was a BSI-CCD for UV recordings on the Hubble Space Telescope .

BSI sensors have been mass-produced since 2009. With CMOS sensors, the advantages of this arrangement are the improved image quality and higher light sensitivity. Since the beginning of the 2010s, BSI sensors have also been installed in conventional mobile devices and digital cameras.

Individual evidence

1. ↑ NASA Tech Brief on UV-CCD
2. ↑ Press news Omnivision: OmniVision Turns Digital Imaging World Upside Down  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.  
3. ↑ golem.de: OmniVision turns camera sensor technology upside down