ITT THIN FILM PHOTOCATHODE TECHNOLOGY

This most recent innovation from ITT Night Vision, provides generation 4 performance at a fraction of it's previous cost. This has allowed Collins Electro Optics to introduce a new level of performance to the I Cubed system.

Thin film technology delivers tremendous improvements in signal to noise ratio (SNR,expressed in decibels dB) where +3dB represents a signal to noise increase of 50%. Photo response (PR,measured in micro amps per lumen) represents the ability of the thin film galium arsenide photocathode to convert photons to electrons, has also improved dramatically. Halo diameter which determines the diameter of bright stars on the phosphor screen has decreased by 50%.

Each tube we receive is inspected and tested in an optical environment that simulates a faint magnitude 12 star field. Based on tube specifications and our in house testing, we classify tube performance. We have developed an algorithm based on tube dB rating, photo response, halo diameter, EBI (equivalent background illumination) which defines the black level with no input photons present at the photocathode and visual testing. Any tubes that do not meet specification are returned for replacement (this rarely happens).

We have previously catagorized tubes based on dB rating. This is how the United States government arrives at the "figure of merit" classification which is dB rating X tube resolution in line pairs per millimeter lp/mm. All tubes that go into the I Cubed are 64 lp/mm so this is not an issue for us. However simply multiplying dB X lp/mm is not adequate for predicting performance in telescope systems which place tremendous demands on tube performance due in large part to higher f numbers found in typical telescopes. In fact too high an f number (greater than ~f20 can photon starve the photo cathode, dramatically decreasing quantum efficiency and signal to noise ratio.

The bottom line for defining tube performance in telescope systems is that no single tube specification can adequitely predict real world visual performance. For example, a tube with a SNR of 29.5dB and PR of 1900 can produce a lower contrast less pleasing image than a tube with a SNR of 27.5dB and a PR of 2300. When you combine this with EBI and halo diameter it becomes obvious that quantifying performance with a single specification is not possible with image intensifier tubes.

We are confident that the new level of I Cubed performance, brought about by this dramatic improvement in intensifier tube technology will impress even the most vocal critics. Therefore we will continue to offer the same guarantee that if you are not satisfied with the I Cubed Eyepiece for any reason, just return it within 30 days for a full refund less shipping and credit card fees.

Over the coming months, we will be posting images of deep sky opjects captured using a digital camera with the new thin film Gen.4 tube.

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