Specifications

Appendix G

Interline CCD Cameras

Introduction

This appendix discusses the operation and theory of a Princeton Instruments camera with

an interline CCD. Operationally, a camera with a conventional CCD and one having an

interline CCD are quite similar, the principal difference being that a shutter would

ordinarily not be required if the camera has an interline chip.

It is important to note that an interline chip can operate in either of two timing modes,

overlapped or non-overlapped. The operating mode is always overlapped unless the

exposure time is shorter than the readout time, in which case non-overlapped operation is

automatically selected by the controlling software. Because overlapped operation is

faster, to achieve the fastest possible operation, it is generally preferable to operate

overlapped if possible. Thus there may be situations where increasing the exposure time

slightly will cause the camera to switch from non-overlapped to overlapped operation.

When this happens, the video may blank for a moment as the unit is reprogrammed, and

then reappear with approximately double the frame rate that was available when it was

operating non-overlapped. Detailed discussions of how the interline camera works and

the implications for operation follow.

Camera

Introduction: The function of the camera is to collect very low intensity light and

convert the energy into a quantitative, electronic signal (photo-electrons) over a

two-dimensional space. To do this, light from the subject is focused onto an interline

CCD array, in which imaging and light-insensitive readout registers alternate and where

the specified number of columns of pixels for the chip is, in fact, the number of register

pairs. Because the charge on each image pixel never has to transfer more than one row,

the transfer can be made very quickly without smearing.

Formats: Available formats include the RTE/CCD-1300-Y/HS and RTE/CCD-782-

Y/HS. These are interline CCD devices. A special clocking mode to minimize

background signal is supported. See Roper Scientific brochures for detailed

specifications.