Canon LV-7105 Service Manual - Page 26
Hybrid gamma correction, 4 Fan speed control, All lenses are made from lead-free glass - lcd
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Part 1: General Information q All lenses are made from lead-free glass All lenses are made from environmentally friendly lead-free glass. 4.3 Hybrid gamma correction Hybrid gamma correction is a new feature. It combines digital gamma correction and analog gamma correction, and takes advantage of the characteristics* of both. Using the on-screen menu, the user can take advantage of this new feature to control image gradation. * Analog gamma correction: analogue correction is applied to the non-linear analog circuit. In analog correction transitions between gradations are smooth. * Digital gamma correction: Correction is applied through digital processing of the X/Y gamma curve. Using a digital signal, varying the characteristics curve, for example, is simple. Because digital processing is involved, however, transitions between gradations can be abrupt. 4.4 Fan speed control A new feature of this projector is Real Time Fan Control. Temperature sensors control the fan to reduce the fan noise level to an unobtrusive level (39dB) during normal operation. There are two temperature sensors, sensor 1 measuring ambient room temperature and sensor 2 measuring the temperature in the area of the LCD panels. The outputs of the sensors are sent to the CPU, which then controls the voltage applied to the fan as outlined below. 1. If the internal temperature rises, the fan voltage is changed as shown in the figure below. But, if the internal temperature falls, the fan voltage remains unchanged for five minutes, then is changed The fan voltage is determined by the higher of the two sensor temperatures. 2. If the temperature sensed by sensor 1 exceeds 51˚C, or the temperature sensed by sensor 2 exceeds 57˚C, the lamp is extinguished. In this case, the main power switch must be turned off and then back on to resume operation. 3. The fan will continue to run for a maximum of 90 seconds after the power switch is turned off. 4. If the CPU receives no response from a sensor, it determines that the sensor is missing or broken and immediately shuts down the projector. 5. In Service Mode (when operating at high altitude) the fan operates at maximum voltage regardless of room temperature. 1-14