Illumination – Light source and modifier – Adjustable or repositionable modifier
Reexamination Certificate
2000-09-22
2002-10-15
O'Shea, Sandra (Department: 2875)
Illumination
Light source and modifier
Adjustable or repositionable modifier
C362S324000, C362S346000
Reexamination Certificate
active
06464376
ABSTRACT:
This invention relates to beam steering apparatus, in particular to apparatus for steering a beam of visible light, infra red radiation, any other electromagnetic wave or ultrasonic sound in any direction.
Apparatus for directing a beam of light by rotatable mirrors is known from U.S. Pat. No. 4,663,698 and is illustrated schematically in FIG.
1
. The apparatus comprises a first mirror
10
on a rotating first support, or “pan”,
12
which is mounted to apparatus body
14
. The body
14
includes a light source, such as a lamp
16
, and focusing arrangement
18
. Using a belt drive, the pan
12
is rotatable about pan axis
20
by a motor
22
mounted on the body
14
.
A second mirror
24
on a rotating second support, or “tilt”,
26
is mounted on the pan
12
. Using another belt drive, the tilt
26
is rotatable about tilt axis
28
, orthogonal to the pan axis
20
, by a motor
30
mounted on the body
14
. This arrangement of rotatable mirrors can direct light in many directions.
As the pan
12
rotates, it carries the relatively large weight of the motor
30
for the tilt
26
, the motor
30
rotating eccentrically about the pan axis
20
. The weight of the motor
30
strains the pan mounting and adds to the required output level of the motor
22
for rotating the pan
12
. It is known to provide a counterbalance to compensate for the eccentric movement of the motor
30
in order to avoid straining of the mounting of the pan
12
. This latter arrangement, however, further adds to the load on the pan motor. Moreover, the pan
12
cannot be rotated continuously.
U.S. Pat. No. 4,827,387 and U.S. Pat. No. 4,945,459 describe similar lighting apparatus in which by use of belt drives both motors are mounted in a stationary position on the apparatus body. With reference to
FIG. 2
, motors
22
and
30
are rigidly mounted to a bottom plate
40
of the body of the apparatus.
A drive pulley
42
for the pan
12
is mounted to the pan
12
for rotation about the pan axis
20
. The drive pulley
42
is driven by a drive belt
44
which passes around a drive gear
46
mounted on the pan motor
22
.
A pair of coupled drive pulleys
48
for the tilt
26
also rotate about the pan axis
20
. Similar to the drive pulley
42
, one of the drive pulleys
48
is driven by a drive belt
50
which passes around a drive gear
52
mounted on the tilt motor
30
. Another drive belt
54
passes around the other one of the drive pulleys
48
, around a pair of idler gears
56
and then around a tilt-axis drive pulley
58
mounted to the tilt
26
. The gear ratio between the pan motor
22
and the pan
20
is the same as that between the tilt motor
30
and the tilt
26
.
As illustrated in
FIG. 2
, the drive belt
50
driven by the tilt motor
30
, which belt acts to rotate the tilt
26
, passes around the pan
12
. Therefore, if the tilt motor
30
is held stationary and the assembly is driven about the pan axis
20
, there is relative movement between the tilt axis
22
and the drive belt
54
as the tilt
26
is “panned” about the pan axis
20
. As a result, rotation of the pan
12
will induce rotation of the tilt
26
.
Whilst, in this arrangement, the pan is rotatable continuously, in order to achieve a desired movement of the tilt
26
a calculation must be made of the desired tilt movement plus (or minus) a compensation for any simultaneous movement that may occur of the pan
12
. For example, to maintain the tilt
26
at a constant tilt angle for a given angular velocity of the pan, the tilt
26
must be driven at the same angular velocity and in the same direction as the pan
12
. To rotate the tilt
26
at same angular velocity and in a same direction as the pan
12
, the tilt
26
must be driven at twice the angular velocity and in the same direction as the pan
12
.
The result is that to achieve certain combinations of pan speed and tilt speed, the output from the tilt motor
30
is required to be significantly higher when the pan
12
is being driven by the pan motor
22
than when the pan
12
is stationary.
In both of these arrangements, the optical length of the apparatus, that is the distance between the light source
16
and the aperture
60
of the tilt
26
tends to be long. For example, with an aperture size of 8 inches (20 cm), which is typical for apparatus for use in a theatre or discotheque, the optical length is approximately 4 feet (120 cm), with the result that only a beam of relatively narrow angle is output from the apparatus.
The present invention has the object of providing beam steering apparatus in which the problems and disadvantages identified in the prior art are overcome or at least ameliorated.
The present invention is applicable to a range of different types of radiation and energy, all of which have a common characteristic, namely that they are transmitted in a form that has the wave-like properties of reflection and diffraction and that has measurable frequency and wave length. Examples include, but are not limited to, ultra violet, infra red and visible light, ultrasound, audible sound, microwaves and mixtures of one or more of the aforementioned. References in the specification to “beam” are intended to refer to any such radiation or energy in wave-like form.
The present invention provides beam steering apparatus comprising:
first and second rotatable reflectors for deflecting a beam in different directions, the beam being deflectable by the first reflector onto the second reflector so as to deflect the beam substantially in any direction;
a first motor for rotating one of the reflectors and for driving a first input to a gearbox; and
a second motor for driving a second input to the gearbox, the gearbox having an output for rotating the other one of the reflectors.
The term “reflector” used herein includes both non-planar reflectors, having, for example, a concave surface (such as a spherical, parabolic or ellipsoidal surface), and planar reflectors, commonly referred to as “mirrors”. The term also includes non-planar reflectors in which the optical centre of the reflector is spaced from the geometric centre of the reflector.
The present invention also extends to a method of deflecting a beam by deflecting the beam off a first reflector on to a second reflector, and rotating both reflectors so as to deflect the beam substantially in any direction, the method comprising the steps of:
providing a first motor to rotate the one of the reflectors and to drive a first input to a gearbox;
providing a second motor to drive a second input to the gearbox; and
rotating the other one of the reflectors from the output of the gearbox.
The first motor may be arranged to rotate the first reflector and the output may be arranged to rotate the second reflector.
The use of a gearbox to drive one of the reflectors enables wide variations in the required output from, for example, the motor driving the tilt, to be avoided when a belt for driving the tilt passes around the pan.
Preferably, the gearbox is a summation gearbox.
In a preferred embodiment, the first reflector is arranged to rotate about a first axis and the second reflector is arranged to rotate about a second axis substantially orthogonal to the first axis.
The apparatus may include means for generating a beam. However, the apparatus may be provided as an accessory to be attached to a light source or other such beam generating means.
The present invention also provides beam steering apparatus, comprising:
means for generating a beam;
means for rotating the generating means so as to rotate the beam;
a rotatable reflector for deflecting the beam; and
means for rotating the reflector so as to deflect the beam substantially in any direction.
With the above arrangement, only one mirror is used to direct light in substantially any direction. This enables the optical length of the apparatus to be reduced, and a wide angle beam to be output from the apparatus.
The generating means may comprise a housing and a beam source may be disposed within the housing, the housing having an aperture for outputting a beam generated by t
Neils Peggy A.
Sterne Kessler Goldstein & Fox P.L.L.C.
Wynne Willson Gottelier Limited
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