LBCAST

LBCAST (lateral buried charge accumulator and sensing transistor array) is a type of photo sensor which the manufacturer claims is simpler and thus smaller and faster than CMOS sensors. It was developed over ten years by Nikon, in parallel with other manufacturer's development of CMOS, and resulted in shipping product in 2003.

Both CMOS and LBCAST technologies branched from researchers discussions of "amplifying sensors" as a way to develop an imaging sensor with lower power requirements than the already-existing CCD sensor technology, for use in portable devices such as DSLR cameras.[1]

From the Nikon Website:

"In July 2003, Nikon introduced LBCAST- a completely new type of image sensor, different from CCD and CMOS, that is a high-speed, power-efficient, low-noise device to be installed in Nikon's flagship camera, the D2Hs."
"... Compared with conventional sensors, it saves more power and achieves less dark noise. (Dark noise is a phenomenon in which randomly spaced bright pixels appear in images due to the heat from the image device during shooting). Also, LBCAST increases image processing speed and improves sensitivity, contrast and color reproduction."[1]

Comparison between LBCAST and CMOS photo sensors

The main differences between LBCAST and CMOS-based sensors appear to be those given below:[1]

This division is to speed reading, and the separation of green pixels, to which the human eye is most sensitive, reduces noise artifacts which might otherwise be introduced by residual electrical charge in the accumulation circuitry, acquired previously from reading a pixel of a different colour.
Red and blue are significantly less important in human sight, and so presumably a decision was made not to keep separate read channels for the two colours, in order to simplify the circuit design for practical use -- at least in the described version of LBCAST technology.

Uses of LBCAST sensors

As at end 2006, the Nikon D2H and the D2Hs were the only publicly available cameras known to carry the sensor. Nikon has opted to use CCDs sourced from Sony in most of their low and mid range cameras and used a CMOS sensor in the flagship D2Xs/D2x. The LBCAST sensor in the D2Hs has remained at 4.1MP.

With the advent of the D3, D700 and D300 cameras in 2007 and 2008, all featuring CMOS sensor technology, it is unknown whether LBCAST plays a part in the design of the CMOS sensor of either, since Nikon's implementation of LBCAST is an adaptation of CMOS, and it is therefore technically correct to refer to the known instances of LBCAST as CMOS, Nikon has not been forthcoming to requests for specific information on the D3 sensor[2] and Nikon have claimed in the past that LBCAST would be further developed.[1]

Criticisms of LBCAST sensors

The following weaknesses have been cited as affecting the Nikon D2H, although whether these issues have origins specific to LBCAST, and whether LBCAST necessitates these problems, is not known.

References

  1. 1 2 3 4 "LBCAST". Nikon Corporation. Retrieved December 15, 2009.
  2. Hogan, Thom (April 9, 2007). "Answers to Nikon D3 Questions". Retrieved December 15, 2009.
  3. 1 2 Chambers, Lloyd (November 11, 2006). "Infrared Contamination: Good Color Gone Bad". Retrieved December 15, 2009.
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