CCD Shutter Open & Close Delay

Warning

This section describes a CCD feature that is considered legacy. The Shutter-related parameters are not available on modern sCMOS-based cameras.

In order to ensure that the entire sensor is exposed for the specified exposure_time, the mechanical limitations of the shutter must be considered. Open delay (PARAM_SHTR_OPEN_DELAY) and close delay (PARAM_SHTR_CLOSE_DELAY) account for the time necessary for the shutter to open and close. Remember that the camera is exposing while the shutter is opening and closing, so some pixels are exposed longer than others.

An "Iris" shutter opens in an expanding circular pattern.

A "Barn Door" shutter slides across the exposure area.

If the shutter is still closing when the image shifts for a frame transfer or readout, the image will smear. See the section CCD Image Smear for a more complete explanation on smearing. PARAM_SHTR_CLOSE_DELAY allows time for the shutter to close before the image shifts.

The default open and close delay values will vary depending on the brand of camera and the shutter used. Open delay may be up to 15 milliseconds with a close delay of up to 30 milliseconds. Change the default values only if using a shutter other than the shutter shipped with the camera. If a standard Teledyne Photometrics shutter is used, changing PARAM_SHTR_OPEN_DELAY and PARAM_SHTR_CLOSE_DELAY default values will not increase the frame transfer rate.

Please note that the shutter control parameters are available for cameras equipped with mechanical shutter only. Most modern cameras are not equipped with a shutter.