Polaroid CCD Camera User Manual

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Section 2 - Introduction to CCD Cameras

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transports the charge packets in a serial manner to an on-chip amplifier. The

final operating step, charge detection, is when individual charge packets are

converted to an output voltage. The voltage for each pixel can be amplified off-

chip and digitally encoded and stored in a computer to be reconstructed and

displayed on a television monitor."

X=1

X=M

Y=1

Y=N

Output

Readout Register

Amplifier

Figure 2.1 - CCD Structure

2.2.1. Full Frame and Frame Transfer CCDs

In the ST-7E, ST-8E, ST-9E, ST-10E and ST-1001E, the CCD is read out electronically by shifting
each row of pixels into a readout register at the Y=0 position of the CCD (shown in Figure 2.1),
and then shifting the row out through an amplifier at the X=0 position. The entire array shifts
up one row when a row is shifted into the readout register, and a blank row is inserted at the
bottom. The electromechanical shutter built into the camera covers the CCD during the
readout to prevent streaking of the image. Without a shutter the image would be streaked due
to the fact that the pixels continue to collect light as they are being shifted out towards the
readout register. CCDs with a single active area are called Full Frame CCDs.

For reference, the ST-5C, ST-237, STV and ST-6 CCD cameras use a different type of

CCD which is known as a Frame Transfer CCD. In these devices all active pixels are shifted
very quickly into a pixel array screened from the light by a metal layer, and then read out. This
makes it possible to take virtually streak-free images without a shutter. This feature is typically

called an electronic shutter.

2.3.

Camera Hardware Architecture

This section describes the ST-7E, ST-8E, ST-9E, ST-10E and ST-1001E

CCD cameras from a

systems standpoint. It describes the elements that comprise a CCD camera and the functions
they provide. Please refer to Figure 2.2 below as you read through this section.

"History and Advancements of Large Area Array Scientific CCD Imagers", James Janesick, Tom

Elliott. Jet Propulsion Laboratory, California Institute of Technology, CCD Advanced Development

Group.

The ST-1001E does not have a second CCD for tracking.