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Pixel shift technology

In cameras with pixel shift technology the sensor is mounted on a precise piezoelectric crystal stage which allows the CCD to be nano-shifted by 1/3 or 1/2 of a pixel. This enables the standard resolution to be extended by 4 times or even by 9 times. In this way applications that demand ultra high resolution can be realised.

The pixel shifting process is shown in Figure 1. In this example, the sensor is shifted precisely by ½ pixel in the X and Y directions as shown, with the resulting image being a combination of the 4 individual images giving improved resolution (4 shot result image) in comparison with the standard output image (1 shot result image). Image combination is carried out in software on the processing PC. A similar procedure can be carried out by shifting the sensor by 1/3 pixel to produce 9 resultant images.

Figure 1: Pixel shift technology

Cameras that feature pixel shift technology are available in both monochrome and colour versions and the pixel shifting process has additional benefits for colour imaging. Colour cameras use Bayer interpolation to produce colour images and unwanted artifacts can occur such as colour moiré or false color pixels. Using pixel shifting, however, no colour artifacts or aliasing will occur and the colour resolution is optimized, as shown in Figure 2.

Figure 2: Colour optimisation with pixel shift

The improvement in resolution is illustrated on the section of a banknote in Figures 3(a) and 3(b). Figure 3(a) is recorded at the standard resolution settings, but the pattern is pixelated and unclear. Figure 3(b) shows the same region using pixel shift technology and the pattern is clearly resolved. In addition to the benefits of improved resolution the pixel shift gives a larger field of view if fitted with the appropriate lens, which means it could avoid the need to stitch multiple images together or remove the need for multiple cameras, saving both time and money.

Figure 3 (a): Banknote without pixel shift

Figure 3 (b): Banknote with pixel shift