clear_until_trig( );
This function causes the CCD to enter clearing mode and continues clearing indefinitely until a trigger arrives. Both the parallel and serial registers are continuously clearing (moving charge toward and into the serial register then out). When the trigger signal arrives, the CCD finishes the current parallel shift (the maximum delay is the time to shift 1 parallel row) and then stops clearing. Execution immediately continues with the next script instruction. For more information concerning the pinouts and electrical specifications of the trigger port, refer to your camera’s User Manual. (Please note that the current parallel shift is completed before the camera begins integrating.)
expose(exp_time);
The CCD exposes for exp_time milliseconds. This command usually appears immediately after
shutter_open, clear_parallel, or clear_until_trig. Note that exposing is not equivalent to merely waiting for the duration of the exposure time. During an exposure, voltage is applied to the CCD in a gridlike pattern, to produce potential wells (pixels) and to keep the charge from drifting into adjacent cells. On some CCDs, this voltage may be applied in either normal or MPP mode. The mode actually used for the exposure reflects the most recently set parallel shifting mode (whether that mode was set to normal or MPP). exp_time may be set to zero, although this instruction becomes a “no operation” under those conditions. The exp_time variable maintains full precision up to a value of 65,535 milliseconds. After that point, the program creates longer times through an internal loop counter that provides more precise timing than the scripting loop_begin command. Due to this mechanism, some values may be rounded off to a nearby value (for example, prime numbers greater than 65,535 won’t be exactly represented). The maximum exposure length is 2^32 milliseconds (about 49 days). For more information on using exposure in conjunction with frame transfer, consult your camera’s User Manual.
expose_until_trig( );
This function begins exposing immediately and continues exposing until a trigger signal arrives. The script then continues with the next instruction. During the exposure, this applies voltage patterns to the CCD in either normal or MPP modes (see expose). As with the regular expose function, this neither opens or closes the shutter. For more information concerning the pinouts and electrical specifications of the trigger port, refer to your camera’s User Manual.
expose_while_trig(clear_first);
This function initiates a scripted version of the
flash(flash_time);
This function activates the flash circuit (a set of pins on the trigger port of many PVCAM cameras) and continues applying power for flash_time milliseconds. In some cases, this may be used to activate devices connected to the camera, such as an illuminator or filter wheel (although the flash signal differs from camera to camera and is often not a
8Advanced Camera Operation Manual