SITe SIA003A TEC Module used in AP8 Cameras	SITe non-TEC SI-003A CCD used in AP8B and AP8P Cameras

When the AP7 camera was introduced in 1996, the imaging sensor used was the SITe 512 x 512 SI-502 TEC (thermoelectric cooler) module. The CCD and TEC came in a vacuum-sealed chamber from Scientific Imaging Technologies, Inc. (see illustration at left above). The ready-to-use chamber made for quick and easy integration onto the Apogee printed-circuit board inside the camera head, and the built-in TEC provided 50 - 55 degrees C cooling below ambient temperature. And, because the SIA502A and SIA003A TEC modules have the same lead footprints, one circuit board could be used for either AP7 or AP8 cameras. All early AP7 and AP8 model cameras used these prechambered CCDs (see the illustration below, left).

In 1999, Apogee designed a chamber for the non-TEC 512 x 512 SI-502A CCDs (as in the illustration above, right), and this became the AP7"B" camera. The primary difference between the AP7 and AP7B was the type of CCD package, but the revision to the camera head's circuit board in order to accommodate the new Apogee chamber resulted in the added benefit of lower system noise. Also, being able to accommodate the non-TEC CCDs gave us more flexibility and lowered the price of AP7 cameras.

Toward the end of 1999, Apogee began work on the parallel-port version of the AP7B camera. This camera was called the AP7"P" and its price was dramatically lowered from the 1996 introductory price. Back-illuminated cameras priced below US$7000 were realized for the first time. Although the earlier AP7 cameras could be modified to "B" or "P" cameras, the changes require both a new CCD and a new pc-board in the camera head, which is essentially a whole new camera. Modifying an existing AP7 or AP8 to a "B" or "P" camera is thus not practical, and Apogee does not offer an upgrade path for this.

In the spring of 2000, Apogee started on the redesign of the AP8 so that it could use the non-TEC SITe 1024 x 1024 SI-003A CCDs. This was more difficult than converting the AP7 because of the large size of the SI-003A CCD. The first units began shipping in fall of 2000. Along with the parallel-port cost reduction by eliminating the ISA-bus card, the change from TEC modules to non-TEC CCDs cut the price of Grade 2 AP8P cameras to nearly half that of the older model AP8.

Due to the tremendous success of the "B" and "P" camera models, Apogee has discontinued the building of cameras using the SITe TEC module CCDs. All AP7 and AP8 cameras are now either "B" or "P" models, depending on the PC interface ("B"= ISA bus, "P"= parallel port) requested at time of purchase. There are no significant performance differences between the ISA-bus and parallel-port versions of the cameras, in terms of system noise and image throughput. The 30kHz processor speed in the camera head is not affected by ISA-bus or parallel-port speeds. The "P" cameras are, however, significantly less expensive.

AP8 Camera Head Electronics with SITe SIA003A TEC Module	AP8P Camera Head Electronics with non-TEC SI-003A CCD