Model 68950 Digital Light Intensity Control Box (right) with Arc Lamp Power Supply.
The 68950 is a light intensity controller and digital timer in one. The light intensity controller maintains a constant light output from your arc, deuterium and quartz tungsten halogen lamps, and the digital timer allows timed exposures and dose control. RS-232 communications allow computer controlled operation.The control box of the 68950 houses the light intensity controller and the digital timer. The large LED readout displays timer and light intensity controller (LIC) information.
Our power supplies are highly regulated; they 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. Fig. 1 shows the marked improvement in output stability when a 68950 is used.
The 68950 is made up of a light sensing head and a controller. The silicon based light sensor monitors part of the light source output; the controller constantly compares the recorded signal to the set level and changes the power supply output to keep the measured signal at the set level. Automatic detector gain setting allows the unit to work with the large variety of Oriel Light Sources offered by Newport.
The sensor is temperature stabilized to maintain complete independence from temperature variations; this means you don't have to worry about variations in the ambient temperature affecting the reading.
As the lamp ages or as other conditions cause a change in the light output, the controller signals the lamp power supply to increase or decrease power to the lamp, in order to maintain the light output constant. (Not all Oriel® Power Supplies work with the 68950 ).
The Digital Timer controls any of our electronic shutters for timed exposure applications. Accurate, repeatable timed exposures down to 2 ms are possible. We also offer a stand alone Digital Timer, for those not requiring a light intensity controller or dose control. Neither the Stand Alone Digital Timer, model 68945 , nor the Light Intensity and Digital Timer System, model 68950 , drive the shutter. They provide TTL output for the driver, which is a part of the shutter system. We also offer Electronic Safety Shutters.
We recommend that you rod mount the light sensor as shown in Fig. 3, using a 5° Wedge, (such as our 44645 BK7 Glass or 44899 Fused Silica 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 spheres ports.Both of the methods described above maximize the performance from the 68950 , as you are monitoring the output of the source rather than just the lamp. Therefore, arc wander and lamp differences are taken into account. However, if these optical set-ups are not practical, you can monitor the lamps output by mounting the sensor directly to an Oriel Lamp Housing, using the kits listed in the Ordering Information Table.
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.
You can remotely control the 68950 or 68945 via a push button switch, model 68955 .