Controlling temperature and humidity

The longevity and brightness of your projector’s lasers require optimal temperatures and humidity. If it gets too hot, the laser diode will at first drop in power, then it may fail completely. If it gets too cold—below the dew point in humid environments—condensation can form, decreasing life. Hence temperature control in the ‘sweet spot’ is important. In this article, we discuss the importance of keeping your projector environment at the right temperature and humidity levels to ensure a long cinema life.

Liquid cooling for a completely sealed LOS design (Left) Cinema projector chassis with mounted cooling fans (Right)

Temperature

One of the biggest factors affecting laser life and output brightness is temperature. Lasers work more efficiently at lower temperatures. This means lasers can achieve higher brightness (lumens per watt) when they are adequately cooled. Maintaining a low ambient temperature in the projection booth is important for a long laser life. For the best results, Christie^® recommends a maximum temperature of 25°C (77°F).

The Christie LOS employs advanced cooling plates and heat exchangers to efficiently remove the heat from the laser diode. Diode arrays arranged in tiles make it easier for the heat to dissipate quickly. Although the temperature of the tri-color lasers can be controlled, the red lasers are the most sensitive to temperature fluctuations. Christie uses specific thermal management techniques to keep the red laser diode at optimal operational temperature.

Using a cooling plate to help dissipate the heat, the laser diodes are liquid cooled. The radiator helps to bring the liquid temps back down as it cycles through. Because it’s a completely sealed system, there are no fans in the LOS to intake or extract air, which means there’s no chance of dust ingress. The overall circulation design is simple, efficient, and conducive to the modular design of the cooling system, making the projector small and compact.

Humidity

Laser elements generate heat that must be dissipated for efficient lifetime operation. Overly aggressive cooling can result in condensation on the optical elements in the LOS that can cause a loss in brightness. Christie solves this with a control circuit that detects moisture levels using a humidity sensor, automatically adjusting system settings to prevent condensation and potential damage. For example, when the projector detects the ambient temperature is too low or the humidity is too high, the control circuit will automatically adjust or raise the temperature to avoid condensation.

Of course, temperature adjustments beyond a reasonable range may change the projector’s output brightness. It is vital to account for temperature and humidity conditions when building your theatre and setting up the projection booth. Your cinema sales representative can guide you on ideal conditions, and our tech support team can answer further questions on the topic.