6 Conclusion

We have proposed a new design for a photon counting device, which can be built from commercially available components. Recent improvements in CCD technology enable the use linear arrays with very fast readout, potentially giving the DELTA camera performance comparable with the best existing photon counting cameras. Moreover, since the DELTA camera provides series of very short frames, it should correctly process quasi-simultaneous photons, which may not be detected with asynchronous cameras. Although our DELTA camera is synchronous, it has the advantages of asynchronous cameras: time resolution and high-flux coordinate determination. On-line data processing from the high-rate signals considered here can be done at present by computers, usually tending to be cheaper and faster than custom electronics. This opens a way to "smart detectors'', like the DELTA camera, based not only on an electro-optical system, but also on a significant software implementation (as back-projection and cross-cleaning). The DELTA camera prototype under development in our laboratory will, we hope, provide valuable improvements to dark speckle and long baseline interferometry observations in the near future.

Acknowledgements

The authors thank A. Blazit, A. Labeyrie,

and F. Vakili, who participated many years ago to the brainstorming which contributed to the birth of the DELTA concept. We are grateful to Dr. J.W. Beletic, and to Dr. O. Jagutzki for their comments and suggestions. S. Morel is supported in this work by a joint fellowship from Matra Marconi Space and CNRS.