National Instruments NI 17xx

Chapter 4 Lighting

The smart camera automatically synchronizes the lighting strobe with the

image sensor exposure. The smart camera always turns the light on before

an exposure starts and turns the light off once the exposure completes.

The duration of the light strobe is dictated by the exposure time. Refer to

Chapter5, Ima ge Acquisition, for more information.

When operating in strobed mode, it is important that the strobe duty cycle

and strobe duration are within the specified limits of both the light and the

Direct Drive lighting controller. The strobe duration is the amount of time

that the light remains on. The strobe duration limit is the maximum amount

of time that the light can remain on when being driven at the maximum

current. The duty cycle is the ratio of the strobe duration to the frame

period, expressed as a percentage. Refer to the Maximum Frame Rate

section of Chapter5, Image Acquisition, for more informati on about the

frame period.

By default, you can set the exposure time to any setting within the range

supported by your smart camera. However, if the smart camera is

configured to use the Direct Drive lighting controller in strobed mode, care

must be taken to ensure that the resulting strobe duty cycle and strobe

duration do not violate the limits of the Direct Drive lighting controller or

the limits of the light. For your convenience, the software calculates the

resulting strobe duration and duty cycle for your configured frame rate and

exposure time. It then compares them to the limits of the Direct Drive

lighting controller and the limits specified in the associated lighting file.

Refer to the Lighting Files section of this chapter or the Maximum Frame

Rate section of Chapter5, Image Acquisition, for more informatio n.

If the requested exposure time violates the limits of the Direct Drive

lighting controller or the limits for your light as specified in the associated

lighting file, the smart camera can use the requested exposure time, but

requires the configured current to be at or below the maximum continuous

current.

Caution If you are using the 5 V strobe output or the 24 V strobe output, the software does

not impose any limits on the duration or the duty cycle of the strobe output. You must

ensure that your requested exposure time and the frame rate result in duration and duty

cycle that do not violate the limits of the external controller and/or light(s). Refer to the

Maximum Frame Rate section of Chapter 5, Image Acquisition, for more information.