Roper Photometric

8Advanced Camera Operation Manual

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

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 a nd 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 t iming 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 si gnal 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 high-level bulb-mode exposure. If

clear_first

is 1, this

initially enters a continuous clearing mode, exactly like clear_until_trig. If

clear_first

is 0, the CCD

exposes while it waits for the trigger. In either case, once the trigger arrives, the CCD switches into an

exposing mode (either normal or MPP, see expose for more information), and continues exposing while the

trigger signal is present. As soon as the trigger ends, the exposure stops, and the script proceeds with the next

instruction. Note that this instruction is not redundant. You can’t use expose_until_trig in conjunction

with other instructions (such as clear_until_trig) to duplicate the function of this trigger, because a

trigger signal stops the exposure with expose_until_trig, while that same trigger signal starts (and

maintains) expose_while_trig. For more information concerning the pinouts and electrical specifications of

the trigger port, refer to your camera’s User Manual. clear_first must be either 0 or 1.

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 TTL-compatible signal). For more information concerning the pino uts and

electrical specifications of the trigger port, refer to your camera’s User Manual.

flash_time

must be between 1

and 65,535, inclusive.