i) Field of the Invention
The present invention relates to an automatic control system for lighting projectors which serve to light up a theater, studio, hall or the like for purposes of stage effects.
ii) Description of the Background Art
In stage lighting for a theater, it is generally necessary to topically light up a specific place on a stage by a lighting projector, for example, a spotlight or the like for the purpose of realizing desired stage effects. If an object to be lit up on the stage is a moving one such as a person or the like, or a specific place is lit up on the basis of such a moving object, it is necessary to control the lighting projector according to the movement of the object so as to shift its lighting direction.
Usually, the lighting direction of such a lighting projector has heretofore been controlled by an operator of the lighting projector while visually observing the movement of the object.
In the control of the lighting direction of the lighting projector by the operator, however, the operator is required to be skilled in operating technique, and it is very difficult to reliably conduct the intended control of the lighting direction for a long period of time because of difference between individual operators in technical skill, operator's fatigue and the like. In addition, a plurality of lighting projectors are often used in lighting of this sort, and if so, the same number of operators as the lighting projectors are required.
In Japanese Patent Application Laid-Open No. 33802/1989, there has hitherto been proposed an automatic tracking apparatus for a spotlight, which serves to track an moving object for lighting.
This apparatus includes a supersonic wave transmitter held by a moving object to be lit up and adapted to reliably generate a supersonic wave at regular intervals by a clock oscillator, a plurality of supersonic wave sensors for detecting this supersonic wave, another clock oscillator in a control unit, which transmits a wave having a frequency closely similar to that of the clock oscillator held by the object, a time difference detector for detecting a time difference between the clock signal from the clock oscillator in the control unit and the clock signal from the supersonic wave sensor, a computing element for operating a distance between the supersonic wave sensor and the object on the basis of the time difference signal to locate the position of the object, and a control unit for controlling the lighting direction of the spotlight according to an output of the computing element.
According to this apparatus, positional data of the moving object can be obtained theoretically. Therefore, the lighting projector can be controlled to automatically shift the lighting direction thereof, thereby tracking the moving object to light up it.
In practice, this apparatus however involves the following problems:
(1) The frequencies in the supersonic wave transmitter held by the moving object and the clock oscillator in the control unit must be caused to approximate to each other with high precision. In practice, however, it is considerably difficult to achieve this approximation. This difficulty becomes greater as the number of moving objects increases. The solution of this problem requires additional signal processing means such as synchronization of a plurality of clock oscillators by radio wave signals. PA1 (2) When the apparatus is applied to a plurality of moving objects, it is necessary to use supersonic waves having frequencies separately preset on the moving objects and correspondingly, employ supersonic wave sensors corresponding to the preset frequencies. In this case, additional signal processing means are required for the individual frequencies. Therefore, the above-described difficulty becomes more and more marked. PA1 (3) The necessity of the above-described additional signal processing requires complicated signal processing for obtaining a positional data for each moving object and hence prolongs the time required for the control. As a result, the time density of the resulting positional data inevitably becomes low, leading to loose control of the lighting projector in the end. PA1 a central control unit; PA1 a radio wave transmitter for transmitting a radio wave signal according to a transmission command signal from the central control unit; PA1 a supersonic wave transmitter held by a moving object and adapted to transmit a supersonic wave by detecting the radio wave signal; PA1 a plurality of supersonic wave detecting devices each having a time counter which is initialized by a start command signal from the central control unit to start instrumentation, adapted to stop the instrumentation of the time counter by detecting the supersonic wave transmitted from the supersonic wave transmitter, and disposed in different stationary positions; and PA1 a lighting projector provided in a stationary position and having a drive mechanism for shifting its lighting direction, PA1 said central control unit including: PA1 a central control unit; PA1 a radio wave transmitter for transmitting radio wave signals according to transmission command signals from the central control unit; PA1 supersonic wave transmitters separately held by two or more moving objects and adapted to transmit respective supersonic waves by detecting the radio wave signals identified correspondingly to the supersonic wave transmitters; PA1 a plurality of supersonic wave detecting devices each having a time counter which is initialized by a start command signal from the central control unit to start instrumentation, adapted to stop the instrumentation of their corresponding time counters by detecting the supersonic wave transmitted from the supersonic wave transmitter, and disposed in different stationary positions; and PA1 at least one lighting projector provided at stationary position and having a drive mechanism for shifting its lighting direction, PA1 said central control unit including:
As described above, the conventional control systems for lighting projectors require complicated constitution and signal processing and consequently involve a problem that control of the lighting projectors according to the movement of moving objects cannot be achieved with high precision.