Continuous evolution and enhancements are natural results of the effort of individual companies to utilize all gained experience and new ideas and also to stay in the forefront and offer better, more reliable and powerful products to their customers. Also cooled CCD cameras of the G2 series already underwent several revisions:

• The first revision used USB 1.1 interface working at 12 Mbps transfer speed. Only G2-0400 model with KAF0402ME CCD was available in this revision. Peltier hot side was cooled by two fans. This particular revision driver was called “g2ccd”.

• The second revision of the G2 camera has only a small changes in the air intake vents shaping to make the camera somewhat quieter. But digital electronics was completely overhauled and upgraded to USB 2.0 interface with 480 Mbps transfer speed. New models G2-1600 and G2-3200 were added and the original model changed name to G2-0402. Camera driver was named “g2ccd2”, the digit “2” in the suffix signalized USB interface version.

• Yet another version of the digital electronics was developed for the new G3 series of CCD cameras with detectors up to 36 × 24 mm (digital electronics board is the same for various models of the same series, individual models differ in analog electronics, designed for every particular type of CCD). Camera driver was “g3ccd”. More exactly two drivers for two versions of these cameras were introduced, one for Full-Frame KAF CCD based cameras (g3ccdF) and the second for Interline-Transfer detectors KAI CCD based cameras (g3ccdI). Differentiation is necessary because of fundamental differences in driving of CCD chips of the above mentioned architectures.

  The same electronic module was later reused also in G2 cameras and even later in the even bigger G4 series. The third revision of G2 cameras was introduced. The best visible visual difference is the usage of a single and slightly larger (and again slightly more quiet) cooling fan instead of two smaller fans employed by previous revisions. Revision three also used enlarged desiccant barrel and allowed much easier desiccant exchange. Number of models of G2 cameras were offered, KAF detector variants (G2-0402, G2-1600, G2-3200), KAI detector variants (G2-2000, G2-4000) and also “astrophotographic” model with ABG KAF detector (G2-8300).

  This revision also introduced slightly confusing naming of G2 and G4 camera drivers—all three series (including the G3 one) used the same driver named “g3ccd”.

Number of internal updates were performed on G2 cameras revision 3 and G3 and G4 cameras revision 1, for instance variants for external filter wheel were developed, additional heating of the cold CCD chamber front optical window was added, near-IR preflash capability was introduced for KAF based models etc. But cameras were the same from the outside and they were software compatible and used the same driver. Development of another version of digital electronics, using modern electronics circuits, and mainly significant redesign of the internal cold CCD chamber required introduction of new revisions of G2, G3 and G4 cameras. G2 series advanced from revision 3 to 4 and G3 and G4 series are now in revision 2.

Similarly also new drivers were unified and named “gXccdF” and “gXccdI” (for FF and IT detectors). G2 and G4 cameras employing Back-Illuminated E2V detectors use new driver “gXccdB”.

Main updates are:

• The G2 revision 4 shell underwent a slight facelift. Camera is less “boxy” and more similar to bigger G3 and G4 models. Air intake vents are better protected against unwanted interference of rotating fans with either fingers of various wires (hitting a rotating fan with finger is not dangerous, only somewhat unpleasant). Changes of the air intake vents is the only distinguishing feature of G3 and G4 cameras revision 2, otherwise the look is identical.

  Basic mechanical dimensions (width, height, depth) of the camera heads did not change. Only the distance of the optical axis relative to camera body center axis is slightly shifted (1 to 2 mm).

• Desiccant container of the G2 cameras was enlarged, it is now identical to the container used on G3 and G4 models.

• CCD cold chambers of all models were significantly redesigned. New chambers bring better insulation from the environment and thus require less frequent desiccant exchanges. They also allow usage of CCDs without cover glass, which are much more demanding to insulation, absence of moisture etc.

• New digital electronics uses 480 Mbps USB 2.0 interface (Gx cameras use only a small fraction the transfer capacity of this interface, so moving to 4.8 Gbps USB 3.0 brings no advantages, only problems with bigger connector, shorter and less flexible cables etc.), still it brings numerous important improvements:

  • Images are downloaded faster, especially in the Preview mode. Low-noise mode is not significantly faster, digitization speed is limited by the necessity to achieve lowest possible read noise.

  • Internal memory buffers are much bigger, despite the buffer size was not limiting even in the case of previous revision, if the cameras are used with at last moderate PC.

  • Temperature regulation is more precise, especially when the camera main controller is busy (e.g. during image digitization).

Numerous changes, affecting almost all camera components including the camera shell, printed circuit boards wit electronics up to new firmware and drivers, is always demanding to management and Gx camera shipment terms were prolonged. But manufacturing of new revisions is ramping fast and availability significantly improves now.