Rochester Imaging Technology Corporation

A Leading Provider of Components and Turnkey Solutions for the Industrial Imaging Market

 

 

TCUV SERIES: ULTRA-HIGH IMAGE RESOLUTION, ACCURACY AND FIELD DEPTH

Opto Engineering TC UV Series Telecentric Lenses are specifically designed to ensure the highest image resolution today available in the machine vision world.

 

No other lenses in the market can efficiently operate with pixels as small as 2 micron; for this reason TC UV Telecentric Lenses are a MUST for all those using high resolution cameras and seeking for the highest possible system accuracy.

 

Common lenses and traditional telecentric lenses operate in the visible light range. The limiting resolution of a lens is given by the cut-off frequency, the spatial frequency at which the lens is no longer able to yield sufficient image contrast information. As the cut-off frequency is inversely proportional to the light wavelength, common telecentric optics are useless with very small pixel sizes (such as 1.75 micron) which are becoming increasingly popular among industrial cameras. TC UV telecentric Lenses operate in the 365/425 nm range and deliver much higher image contrast at high spatial frequencies, being therefore compatible with the tiniest pixel sizes. On the other hand, when used in combination with normal cameras, the resolution of these lenses is so high that they can cope with much larger object displacements (higher field depths) than VIS lenses before any image defocusing becomes evident.

 

The graph above shows the limiting performances (diffraction limit) of two lenses operating at working F-number 8.

 

The VIS lens operates at 587 nm (green ligth) while the UV lens operates at 365 nm.

 

The MTF function, which expresses the contrast ratio, is much larger at high spatial frequencies in the UV than in the VIS range.

 

The vertical bars show the cut-off frequencies of both lenses: at 340 lp/mm, contrast yield by TCUV Lenses is still significant and pixels as small as 1.5 micron can bear useful image information.

The graph above shows the resolution specifications of TC UV lenses.

 

In addition to the MTF diffraction limit, both the MTF curve of TC UV lenses and the CTF (Contrast Transfer Function) curve are displayed.

 

MTF curve refers to the response of the lens to a sinusoidal pattern, while the CTF function expresses the contrast the lens is yielding when a "square wave" pattern made of black and white stripes is imaged.

 

 

If w is the spatial frequency and p is the pixel size, then a pixel whose size is p = 1/2w will yield a contrast given by the CTF at the spatial frequency w.

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