Illumination obscurement device

Details Illumination obscurement device Illumination obscurement device

1998-07-01

2001-04-24

Spyrou, Cassandra C. (Department: 2872)

Illumination

Light source and modifier

Including reflector

C362S257000, C362S276000, C362S277000, C362S282000, C362S303000, C345S031000, C348S098000, C348S743000, C352S040000, C352S041000, C352S089000, C352S208000, C352S212000, C353S088000, C353S097000

Reexamination Certificate

active

06220730

ABSTRACT:

TECHNICAL FIELD
The present disclosure describes a special image obscurement device for a light source.
BACKGROUND
In live dramatic performances controlled lighting is often used to illuminate a performer or other item of interest. The illuminated area for live dramatic performance is conventionally a circular beam of light called a “spot light.” This spot light has been formed from a bulb reflected by a spherical, parabolic, or ellipsoidal reflector. The combination forms a round beam due to the circular nature of reflectors and lenses.
The beam is often shaped by gobos.
FIG. 1
shows a light source
100
projecting light through a triangular gobo
108
to the target
105
. The metal gobo
108
as shown is a sheet of material with an aperture
110
in the shape of the desired illumination. Here, that aperture
110
is triangular, but more generally it could be any shape. The gobo
108
restricts the amount of light which passes from the light source
100
to the imaging lenses
103
. As a result, the pattern of light
106
imaged on the stage
105
conforms to the shape of the aperture
110
in the gobo
108
.
Light and Sound Design, the assignee of this application, have pioneered an alternate approach of forming the gobo from multiple selected reflective silicon micromirrors
200
. One such array is called a digital mirror device (“DMD”) where individual mirrors are controlled by digital signals. See U.S. Pat. No. 5,828,485 (application Ser. No. 08/598,077) and application Ser. No. 09/145,314, the disclosures of which are herein incorporated by reference. DMDs have typically been used for projecting images from video sources. Because video images are typically rectangular, the mirrors of DMDs are arranged in a rectangular array of rows and columns.
The individual mirrors
200
of a DMD are rotatable. Each mirror
200
is mounted on a bar
204
such that it can rotate in place around the axis formed by the bar
204
. Using this rotation, individual mirrors
200
can be turned “on” and “off” to restrict the available reflective surface.
FIG. 2
shows an example of using a DMD
400
to project a triangular illumination by turning “off” some of the mirrors in the DMD
400
. The surface of the DMD
400
exposed to a light source
402
comprises three portions. The individual mirrors which are turned “on” (toward the light source
402
) make up an active portion
404
. In
FIG. 4A
, the active portion
404
is triangular. The individual mirrors which are turned “off” (away from the light source
402
) make up an inactive portion
406
. These pixels are reflected. The third portion is a surrounding edge
408
of the DMD
400
. Each of these portions of the DMD
400
reflects light from the light source
402
to different degrees.
FIG. 3
shows a resulting illumination pattern
410
with the active area
404
inactive area
406
and cage
408
.
SUMMARY
The inventors recognize that light reflected from the inactive portion
406
of the DMD
400
generates a dim rectangular penumbra
418
area is surrounding the bright desired area
404
. Light reflected from the edge
408
of the DMD
400
generates a dim frame area. The inventors recognized that this rectangular penumbra
418
is not desirable.
The inventors also recognized that a circular penumbra is much less noticeable in the context of illumination used in dramatic lighting.
Accordingly the inventors have determined that it would be desirable to have a device which would provide a circular illumination without a rectangular penumbra while using a rectangular arrayed device as an imaging surface. The present disclosure provides such capabilities.
This disclosure describes controlling illumination from a light source. The disclosed system is optimized for use with a rectangular, arrayed, selective imaging device.
In a preferred embodiment, a rotatable shutter with three positions is placed between a DMD and the imaging optical system. The first position of the shutter is a mask, preferably a circle, placed at a point in the optical system to be slightly out of focus. This circle creates a circular mask and changes any unwanted dim reflection to a circular shape. The second position of the shutter is completely open, allowing substantially all the light to pass. The third position of the shutter is completely closed, blocking substantially all the light from passing.
An alternate embodiment for blocking the rectangular penumbra by changing any penumbra to round uses an iris shutter placed between a DMD and increases optics. The iris shutter creates a variable aperture which ranges from completely closed to completely open. Intermediate settings include circles of varying diameter, resulting in similar projections as with the first position of the shutter embodiment.
Another alternate embodiment for blocking the rectangular penumbra by changing any penumbra to round uses two reflective surfaces. The first reflective surface is a DMD. The second reflective surface is preferably a light-sensitive reflective surface such as a polymer. If the light striking a portion of the reflective surface is not sufficiently bright, that portion will not reflect the full amount of that light.
By controlling the penumbra illumination surrounding the desired illumination, DMDs and other pixel-based rectangular elements can be used in illumination devices without creating undesirable rectangular penumbras.


REFERENCES:
patent: 1865186 (1932-06-01), Harris, Jr.
patent: 5379083 (1995-01-01), Tomita
patent: 5541679 (1996-07-01), Yang
patent: 5668611 (1997-09-01), Ernstoff et al.

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