US 4,467,246 A · Light quantity controller and input device

Abstract

A light quantity controller and an input device are disclosed. The light quantity controller comprises a light source, a photo-sensor to detect a light quantity of the light source, a signal source for generating a reference signal, a comparator for comparing the detected light amount with the reference signal, and control circuit to control a duty ratio of the energization to the light source in accordance with the compare result to maintain the light quantity of the light source at a constant level. The light quantity controller further comprises a comparator to compare the energization signal to the light source with a reference signal to detect the degradation of the light source. The input device has a key matrix including a plurality of input ports and a plurality of output ports of a control unit interconnected through switches. A signal source independent from the output ports of the key matrix is connected to at least one of the input ports through switches.

Claims18

Dependent claims

A light quantity controller comprising:

a light source adapted to emit light upon energization;
means for detecting the light quantity of said light source, and for producing a detection signal;
setting means for manually setting a desired light quantity of said light source, and for generating a reference signal in accordance with the light quantity set;
means for comparing the detection signal and the reference signal from said setting means, and for producing a comparison result as an output;
means for controlling an amount of an energization signal applied to said light source in accordance with the reference signal from said setting means;
and
means for adding the output signal from said comparing means to the reference signal to be applied to said control means so that the light quantity detected by said detecting means becomes equal to the desired light quantity set by said setting means.

4 more elements

Dependencies are inferred from the claim text.

Light quantity controller and input device

Life of this patent

Light quantity controller and input device

Life of this patent

Abstract

Claims18