NEW PRODUCTS – NEW POSSIBILITIES
Telecentric lenses with
tunable working distance
focusing without moving elements
Figure 2: Measured temporal noise in the compressed signal
parts of the image, and more than 8 bits just carries the photon noise of the data. Te questions arise whether it is possible to
apply a nonlinear transformation in such a way that the temporal noise is independent of the grey value, and what is the minimum number of bits with which a signal can be presented without any significant loss of information? It would be especially useful if an 8-bit quantisation could be achieved for up to 16-bit image data. To find a solution for these
questions, firstly the nature of the photon noise and the theoretical linear camera model (see EMVA 1288 Working Group) has to be considered, and secondly the influence of additional noise caused by quantisation has to be taken into account. A detailed derivation of the solution is too long for this article, but it can be found in the paper referenced at the end of the page. In one example the nonlinear
Any
equidistant quantisation is a clear mismatch
required instead of 16-bit, resulting in a compression ratio of two. Aſter measuring the parameters according to EMVA 1288 with the decompressed data (middle row in Table 1), there is additional noise that results in higher system gain. Aſter correction of the system gain (lower row in Table 1) the measurement results fit very well with the original measurement without compression. Te interest in compression
was because the Camera Link interface found on the PCO Edge camera had limited bandwidth – this was the fastest interface at that time – and the requirement to stream the data at a higher rate. An approach of a simple nonlinear transformation was used
transformation scheme was applied to the PCO Edge 5.5 operated in fast-scan mode, and an almost constant, signal-independent noise is achieved (Figure 2) as predicted by the theoretical considerations. Te original image is quantised with 16-bit. Using procedures detailed in the EMVA 1288 standard, the standard deviation of the dark noise and the system gain were measured (upper row in Table 1). Te compression parameters are set in a way that only 8-bit per pixel is
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by PCO, but a convincing solution was only found through the cooperation between the Heidelberg Collaboratory for Image Processing (HCI) and PCO. Both parties benefit from each other; PCO gets access to wide-ranging interdisciplinary knowledge of HCI, and HCI gets access to high-end camera equipment for applied research. O
Reference
B. Jähne and M. Schwarzbauer: Noise equalisation and quasi lossless image data compression – or how many bits needs an image sensor? Technisches Messen, 83, 16-24, 2016.
http://dx.doi.org/10.1515/teme-2015-0093.
0.13x - 0.66x for sensor up to 16 mm
1x - 3x for sensors up to 35 mm
Telecentric lenses with
integrated coaxial illumination
improved image homo- geneity and intensity
exchangable beamsplitter (unpolarized, polarized)
possibility to integrate a retardation plate
Visit us at South hall, booth 1146
SILL OPTICS GmbH & Co. KG Johann-Hoellfritsch-Str. 13 DE-90530 Wendelstein Phone: +49 (0)9129 - 90 23-0
info@silloptics.de •
silloptics.de
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