GB2295739A - Infrared ray wireless microphone - Google Patents

Abstract

A microphone housing 10 has a generally cylindrical shape and a number of wide-angle infrared LEDs, 12, 12 ..., facing obliquely downwards, around the axis the lower end portion of the housing 10. The light radiation angles are generally mutually adjacent or partially overlap. The LEDs 12, 112 ... are mounted on surfaces of a prismoidal or pyramidal pedestal 24 having through holes for LED terminals. A carrier wave, modulated by the microphone output, drives the LEDs. <IMAGE>

Description

TITLE Infrared ray wireless microphones DESCRIPTION technical Field The invention relates to infrared ray wireless microphones which are omnidirectional like radio wave wireless microphones.

Background Art With a radio wave wireless microphone, as radio waves radiate in all directions, reception at a receiver without fading or noise is possible even if the attitude of the wireless microphones or the direction in which it is pointed changes according to the movement of a singer.

However, in a karaoke booth, a large number of wireless microphones are used near to one another. As the number of channels is restricted by the Wireless Telegraphy Act, a number of wireless microphones may be used close together on the same channel. Radio waves pass through the walls which partition the various compartments, so there is interference between the karaoke systems in the different compartments.

For resolving this problem, there are infrared ray wireless microphones. In a conventional infrared ray wireless microphone, one or two infrared LEDs face one direciton at the bottom of the microphone housing, and one to three infrared LEDs are driven by carrier waves modulated by electrical signals to which sound input into the microphone has been converted. The light radiated by the infrared LEDs is picked up by light pickups on the walls of the respective compartments, and converted to electrical signals again. These signals are input into an acoustic device.

Such infrared ray wireless microphones cause no interference in the karaoke systems in the different compartments as the light emitted by the infrared LEDs is completely cut off by the compartment walls. No restrictions are imposed by the Wireless Telegraphy Act.

However, if the movement of the singer changes the direction or attitude of the microphone and the light pickup no longer lies within the directivity range, fading occurs or noise is produced.

The Invention The invention provides an infrared ray wireless microphone of generally cylindrical shape having a number of wide-angle infrared LEDs arranged around the axis of the microphone, a carrier wave generator for driving the LEDs, and means for modulating the carrier wave with electrical signals to which sound input to the microphone has been converted. Preferably, the LEDs face obliquely downwards; they may be mounted on surfaces of a prismoidal or pyramidal pedestal having through holes for LED terminals.

The microphone may be covered by a windscreen at the top end of a housing. The LEDs may be located at one end of the housing, on the surface of the windscreen, or at the top of the windscreen. Their light radiation angles of the LEDs may be mutually adjacent or partially overlap so that together they radiate in all directions.

Drawings Fig. l(a) is a side view, partially cut-away of an outer case of an infrared ray wireless microphone according to the invention; Fig. 1(b) is a view along the arrow A in Fig. l(a) with the outer case removed; Fig. 2(a) is a side view of a pedestal in Fig. 1 on which wide-angle infrared LEDs are mounted; Fig. 2(b) is a view along the arrow A in Fig. 2(a); Fig. 3 is a cross-section showing the wide-angle infrared LEDs assembled with the pedestal; Fig. 4 shows the range over which signals from the infrared ray wireless microphone of Figs. 1 to 3 are radiated; and Fig. 5 is a block diagram of the electrical circuit incorporated in the infrared ray wireless microphone of Figs. 1 to 3.

With particular reference to Fig. 1, six wide-angle infrared LEDs 12, 12 ... are installed at the bottom of an infrared ray wireless microphone housing 10. The housing 10 is generally of a circular cylinder with a diameter suitable to make it easy to grip. The top is covered with a windscreen 14 (Fig. 4). The housing 10 accomomdates a nickel-cadmium battery 18 as a power supply, a frame 20 for supporting and fixing the wideangle infrared LEDs 12, 12 ..., the microphone itself and an electrical circuit for the functioning of the microphone. All of these elements are covered by a case 22 of plastics material, the portion of which faces the wide-angle infrared LEDs 12, 12 ... being of a smoked semi-transparent material, through which infrared rays pass without attenuation, but which attenuates visible light.

At the lower end of the housing 20, a pedestal 24 for determining the mounting attitudes of the wide-angle infrared LEDs 12, 12 ... is fixed by means of screws, and a small space 26 (Fig. 3) is defined between the pedestal 24 and the lower-end of the frame 20. The pedestal 24 has one end surface fitting against the frame 20, and an approximately hexagonal prismoid 24a on the other end surface. An electrode hole 24b (Fig. 2(b)) is formed through the centre of the hexagonal prismoid 24a, on the axis of the housing 10. Pairs of terminal holes 24d, 24d ,,, into which the terminals 12a, 12a ... (Fig. 3) of the wide-angle infrared LEDs 12, 12 ... can be inserted, pass through in the axial direction, in respective sloping surfaces 24c, 24c ... of the hexatgonal prismoid 24.

Positioning projections 24e, 24e ..., which have recess portions for receiving and positioning the sidewall portions of the wide-angle infrared LEDs 12, 12 ..., are provided at the bottom of respective sloping surfaces 24c, 24e ....

One end of a flexible circuit board 34 is fixed to the surface of the pedestal 24 on the side that fits together with the frame 20. This end has holes facing the electrode hole and the terminal holes 24d, 24d ... in the pedestal 24, and it has a wiring pattern formed on it.

The terminals 12a, 12a ... of the wide-angle infrared LEDs 12, 12 ... pass through the terminal holes 24d, 24d ... and then bend. The bottom surfaces of the wide-angle infrared LEDs 12, 12 ... like on the sloping surfaces 24c, 24c ... of the prismoid 24a, and their sidewalls contact the recesses in the positioning projections 24e, 24e ... (Fig. 2(a)).

An insulating element 28 (Fig. 3) is provided at the vertex of the prismoid 24a. An annular electrode 30 is fixed on this insulating element 28. Free ends of strip conductors 30a, 30a project from the annular electrode 30 and pass through the pedestal 24 and the circuit board 34. An electrode 32 engages in the hole 24b, and is electrically isolated from the annular electrode 30 by a cylindrical portion of the insulating element 28. The element 28 has an expanded portion at an outer end, and at its upper end a thread which passes through the circuit board 34, has a washer and nut screwed on it, and fixes one end of the circuit board 34 to the pedestal 24.

It also serves to fix the electrode element 32 itself.

The terminals 12a, 12a ... of the wide-angle infrared LEDs 12, 12 ... and the strip conductors 30a, 30a ... of the annular electrode element 30 are fixed to the wiring pattern of the circuit board 34 by soldering.

The circuit board 34 has one end fixed to the pedestal 24, and is accommodated in the space 26 by being bent into an approximate U shape. An LED driver 36 is formed as a circuit by the provision of circuit elements on opposite sides of the U shape. The wiring pattern to which the electrode element 32 and the strip conductors 30a, 30a of the annular electrode element 30 are electrically connected forms a charging circuit to the terminals of the nickel-cadmium battery 18.

By way of example of the light radiation angle of a wideangle infrared LED 12, the half power angle is 45 degrees on the positive side and on the negative side with respect to the axis which the LED faces, and the angle for the maximum value is about 70 degrees. Six wideangle infrared LEDS 12, 12 ... are equally spaced at 60 degree intervals around the axis of the housing 10. They are set facing obliquely downwards at an angle of about 20 degrees relative to the plane normal to the axis. With this arrangement, the wide-angle infrared LEDs 12, 12 are so disposed around the axis that, in terms of the half power angles, the radiation angles are more or less adjacent to one another, and their maximum-value radiation angles partially overlap one another.

Underneath in the axial direction, the maximum-value radiation angles are mutually adjacent. Therefore infrared signals from the wide-angle infrared LEDs 12, 12 are art radiated over the whole range other than a circular cone with a downwardly directed vertex. If, as shown in Fig. 4, one or two light pickups 40 are installed on wall surfaces 38, irradiated by the infrared signals, signals can always be picked up, even if the direction or the attitude of the infrared ray wireless microphone changes in the course of use. If several light pickups 40 are installed, the sum of their signals is supplied to an acoustic device on the reception side.

Alternatively, the arrangement may be such that the signals from that one of the light pickups in which the received light intensity is the stronger or strongest are selected.

The six wide-angle infrared LEDs 12, 12 ... are driven simultaneously by the LED driver 36, whose drive control is conventional. Sound signals that have been input into the microphone (Fig. 5) are output as electrical signals.

These are amplified by a low-frequency amplifier 42 and then are adjusted, by a modulation degree adjuster 44, to a range in which over-modulation does not occur. A modulator 48 uses the resulting signals for frequency modulation of a carrier wave signal that is produced by a carrier wave generator 46. The carrier wave signal is so set that two waves, e.g. of 2060 kHz and 2560 kHz, can be selected. The modulated carrier wave signal is amplified by a high-frequency amplifier 50, and supplied to the LED driver 36. The LED driver 36 controls the emitted light intensity of the wide-angle infrared LEDs 12, 12 ... in accordance with the modulated carrier wave signal.

Although six wide-angle infrared LEDs 12, 12 ... are used, all that is needed is a number of infrared LEDs suitable in view of their radiation angle. Although the wide-angle infrared LEDs 12, 12 ... are located at the bottom of the housing 10, where there is little likelihood of their being covered as the result of the microphone being held, they may be anywhere as long as they are not liable to be covered when the wireless microphone is held. They may be at the upper end of the housing 10, near the junction with the windscreen 14. The wide-angle infrared LEDs 12, 12 ... may also be disposed in equal-spread locations around the axis or at the upper end of the windscreen 14. There may be a hexagonal pyramid instead of the approximately hexagonal prismoid 24a on the pedestal 24.

Claims (4)

1. An infrared ray wireless microphone of generally cylindrical shape having a number of wide-angle infrared LEDs arranged around the axis of the microphone, a carrier wave generator for driving the LEDs, and means for modulating the carrier wave with electrical signals to which sound input to the microphone has been converted.

2. A microphone according to claim 1 in which the LEDs face obliquely downwards.

3. A microphone according to claim 2 in which the LEDs are mounted on surfaces of a prismoidal or pyramidal pedestal having through holes for LED terminals.

4. An infrared ray wirless microphone as herein described with reference to the drawings.