Intensified Camera Systems

Pattern Recognition Group, Faculty of Applied Physics Delft University of Technology, Lorentzweg 1, NL-2628 CJ Delft, The Netherlands

A wide range of cameras is currently available, e.g.: video-rate CCD-cameras, slow-scan cooled CCD-cameras and CID-cameras. For an enhanced gain, these camera systems can also include an image intensifier. The performance of a certain camera system together with its price tag, defines it field of application. We are interested in two aspects - what is the performance of a given image intensifier and what is the underlying model that explains this performance. The intensifier under study is a 2nd generation multichannel plate (MCP) image intensifier. In the past we have reported on methods to characterize CCD-cameras [1,2]. An extension of these methods will be used to measure the performance, that is charcteristics, of intensified cameras. Further, we wiill consider how the measured results are explained by the fundamental principles of the intensifier.

The properties of interest are:

• Photon-to-photon gain;
• Noise effects;
• Spatial frequency response.

These properties can be retrieved by the CCD characterization methods [1], applied to systems with and without intensifier. The difference in performance of those two systems must be due to the intensifier. These results, together with manufacturers specifications, can be tested with the underlying Poisson model for photon/electron statistics [3].

Another method is based on measuring single photon responses, instead of the statistical methods described above. By looking at the response of a single detected photon (at the photocathode) or thermally induced electron, similar properties can be determined:

• The total response is a measure for the gain. Given the gain of the camera, the photon-to-photon gain can be calculated;
• The difference in gain from one event to another represents the noise;
• The spatial spread in the single photon response is the point spread function (PSF), which is the spatial domain representation of the spatial frequency response.

The image intensifier under study is a Delft Electronic Products xx1450 2nd generation multichannel plate (MCP) intensifier (S25 photocathode, P43 phosphor screen). The intensifier is optically coupled to the camera using two camera lenses (50mm, f/=1.4). All measurements are made with a Photometrics KAF1400 camera.

This work is supported by Lambert Instruments B.V. and STW, The Netherlands' Organization for Scientific Research.

Bibliography

1. Mullikin JC, Van Vliet LJ, Netten H, Boddeke FR, Van der Feltz G, Young IT: Methods for CCD Camera Characterization. In: Proceedings of the SPIE Conference on Image Acquisition and Scientific Imaging Systems, San Jose, California, SPIE TC-2173, pp. 73-84, 1994.

2. Young IT, Rutten A, Netten H, Van Vliet LJ: Characterization of a color CCD camera. In: Proceedings of the European Workshop on Microscope Instrumentation, San Miniato, Italy, pp. 97-92, 1994.

3. Snyder DL and Miller ML: Random Point Processes in Time and Space, Springer-Verlag, 1993

e-mail: young@ph.tn.tudelft.nl