Patent ID: 6967644

Claim:
A coordinate input apparatus for inputting three-dimensional coordinates, comprising: designation means, having a light emission device, for designating a three-dimensional position, a plurality of line sensors for receiving light emitted by the light emission device and determining a three-dimensional position where the light emission device exists; a photoreception device for receiving light emitted by the light emission device; calculation means for calculating three-dimensional coordinates of a position where said designation means exists, based on a determined value obtained by said plurality of line sensors; and synchronization means for synchronizing a light emission cycle of the light emission device with a photoreception cycle of said line sensors based on a signal outputted by said photoreception device, wherein the light emission device emits light in a predetermined cycle, each of said plurality of line sensors comprises an electronic shutter function, and the electronic shutter function is turned on and off with a phase synchronous with the light emission cycle of the light emission device or a cycle which is an integral multiple of the light emission cycle, wherein said designation means includes a plurality of switches, the light emission device emits light based on one of a plurality of different modulation signals modulated by a carrier frequency higher than the predetermined cycle, and selection from the plurality of different modulation signals is made by the plurality of switches, wherein said synchronization means comprises generation means for generating a group of signals representing auxiliary data, indicative of time axis data of a signal from the light emission device and switch data for the plurality of switches of said designation means, based on a signal obtained by inputting a signal from the photoreception device to a band-pass filter having the same frequency characteristic as the carrier frequency, and based on the group of signals generated by the generation means, the light emission cycle of the light emission device and the photoreception cycle of said plurality of line sensors are synchronized, wherein said synchronization means executes a timing sequence, serving as a control signal of said plurality of line sensors, by referring to an arbitrary light-on timing of the light emission device obtained by the group of signals, and repeats the timing sequence each time coordinate data for a point is processed.