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Digital Exposure System, Research Lamp Sources


Correct for Lamp Output Variations with Age

Our lamp power supplies are highly regulated and operate lamps at constant current or power, even if the line voltage changes over a wide range. Even with lamp current constant, the light output of many lamps varies with age, filament or electrode erosion, gas adsorption or desorption, and, particularly for mercury lamps, ambient temperature. Both the total output and the distribution of power between the spectral lines from a mercury lamp change with temperature. These effects cause output variations with time, with different and sometimes pronounced frequency dependence. Even the relatively simple quartz tungsten halogen lamps exhibit output variations: evaporation and halogen cycle redeposition of tungsten constantly change the microstructure of the filament. The 68950 corrects for these lamp output changes, maintaining a constant, long term output, from the lamp.

Intensity of arc lamp under with and without 68950 control.

Ideal Optical Set-up

We recommend that you rod mount the light sensor as shown in Fig. 3, using a 5° Wedge to split off part of the beam. The normal surface reflection off the substrate is enough to "pick-off" a portion of the beam for monitoring by the 68950 sensor. You can also use a beamsplitter at 45°, but you may need to attenuate the light hitting the sensor with an aperture, diffuser or filter, depending upon the reflectance of the beamsplitter. The 7123 Mount holds a 1 inch (25.4 mm) diameter optic at the input of the light sensor. Another method of monitoring the light output, if you have plenty of light to spare, is to use an integrating sphere at the output of the source, and mount the light sensor on one of the sphere’s ports.

Monitors and Adjust Light Output

The 68950 is made up of a light sensing head and a controller. The silicon based light sensor is temperature stabilized to maintain complete independence from temperature variations and monitors part of the light source's output. The controller constantly compares the recorded signal to the set level and changes the power supply output as the lamp ages or as other conditions cause a change.

Built-in Digital Timer

The built-in digital timer controls any of our electronic shutters for timed exposure applications. Accurate, repeatable timed exposures down to 2 ms are possible. The Digital Exposure System for Research Sources, model 68950, doesn't directly drive the shutter, but rather provides a TTL output signal for the shutter controller, which is a part of the shutter system. We also offer Electronic Safety Shutters.

Adapter Kits for Oriel® Lamp Housings

For convenience, you can mount the sensor directly to the lamp housing. The 68952 Adapter Kit mounts the sensor off our Research Housings, looking transversely at the lamp. The 68952 includes a filter holder with a beam attenuator. The 68954 Adapter Kit mounts the sensor on an unused port of the Series Q Housing. It also includes a filter holder and beam attenuator.

The 68952 Adapter Kit shown connecting a 71582 Silicon detector to a research lamp housing