National Instruments ISC-1762, Руководство пользователя

Страница: 30 / 80

4-2
|
ni.com
Chapter 4 Lighting
Direct Drive Lighting Controller
This section applies only to the following NI Smart Cameras:
• NI 1742
• NI 1744
• NI 1762
• NI 1764
The NI Smart Camera offers an innovative lighting controller that directly powers third-party
current controlled lights. With other smart cameras, a lighting controller that drives a light must
be purchased separately. The Direct Drive lighting controller is capable of powering a variety of
third-party lights.
For a current controlled light, higher current produces more light, up to the maximum current
rating of the light. The maximum current rating of the light is specified by the manufacturer and
based on the average amount of power that can be safely dissipated by the light.
The Direct Drive controller can operate in continuous or strobed mode. When operating in
strobed mode, the controller can provide more current to the light than in continuous mode. The
average power dissipated while strobing the light for a short period of time at a higher current
can be comparable to the average power dissipated while running the light continuously at a
lower current. Table 4-1 shows the maximum allowed current for continuous mode and strobed
mode.
For applications with a pause between exposures while new parts move into position, you can
strobe the light, which allows the use of higher current and produces more light; thus you can
reduce the exposure time. A shorter exposure time decreases the time it takes to acquire an image
and potentially increases the total throughput of the system. Refer to the
Exposure
section of
Chapter 5,
Image Acquisition
, for more information about exposure control.
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 Chapter 5,
Image 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
Table 4-1. Maximum Allowed Current for Direct Drive Lighting Controller
Maximum Strobed Current Maximum Continuous Current
1 A 500 mA