 |
Description  |
|
|
FIELD OF THE INVENTION
This invention relates generally to a light projection apparatus and, in
particular, but not exclusively, to an apparatus for use in the projection
of television or video pictures and similarly derived images of computer
generated or other visual information onto viewing surfaces. More
particularly, this invention relates to an optical system attached to the
final output of a projector for projecting images of varying size, contour
and orientation relative to the projector on either single or multiple
viewing surfaces.
BACKGROUND OF THE INVENTION
In conventional laser video projectors all of the red, green and blue light
beam components are transmitted to a horizontal scanner or rotating
polygon mirror having a predetermined number of facets and then onto three
lenses, preferably 454-640 nm AR coated high power achromats to a frame
scanner or scanning mirror. The three lenses positioned between the
rotating polygon mirror and the scanning mirror are 55 mm, 25 mm
cylindrical and 55 mm to 160 mm, respectively. Such a projector is
disclosed in U.S. Pat. No. 5,136,426, which is assigned to the same
assignee as the present invention and is incorporated by reference herein
for all purposes. The image on the scanning mirror is then directed to a
fixed steering mirror to a viewing surface. This viewing surface can be a
solid surface, such as a conventional projector screen or wall. Other
conventional scanning means could be used with the present invention, such
as the scanning means disclosed in U.S. Pat. Nos. 4,613,201; 4,611,245;
4,979,030; or 4,978,202, that are incorporated by reference herein for all
purposes.
It is known by those skilled in the art that when an image is moved
horizontally by a rotating steering mirror, the image needs to be rotated
responsive to this horizontal movement to maintain the image right side
up. Conventional rotator means or assemblies to rotate the image
responsive to the horizontal movement include a dove prism, K-mirror or
pechan prism. However, because of the expanding nature of the image, or,
in other words, the diverging image transmitted from the scanning mirror
of the projector, a properly sized rotator assembly and the steering
mirror are larger than desired and, in turn, require large motors for
moving the steering mirror and rotator assembly.
Dove prisms have been used in the past for rotating the image responsive to
the horizontal movement. U.S. Pat. Nos. 2,966,096; 3,894,798; 4,235,535;
and 4,645,318 are examples of conventional dove prisms that are
incorporated by reference herein for all purposes. Another example of a
conventional dove prism used to rotate a laser image responsive to
horizontal movement is a 2".times.2".times.6.5" dove prism having a prism
corner cut of 55.degree. with the index of refraction of the glass stock
being n=1.51. This dove prism requires a 5".times.5" steering mirror,
weighs approximately 1150 grams (2.5 lbs.) and requires a rotation stage
with a central aperture of at least 3".
U.S. Pat. No. 4,235,535 discloses a projector for projecting images onto a
cylindrical screen for purposes of simulating the view of a ship in a ship
simulator. The image is projected onto the dove prism 13 for rotation
responsive to the horizontal movement of the image. The horizontal and
vertical movement of the image are controlled by stepping motors. These
stepping motors can be operated manually or by computer independently of
each other. The speed of rotation of the dove prism 13 is one-half the
horizontal movement.
Mirrors have also been used in the past for rotating an image. As best
shown in FIG. 1 of U.S. Pat. No. 3,326,077, a lamp 52 is located below a
photocell 54 directly behind a condensing lens system 56 which is designed
to collimate the light emitted by the lamp onto a slightly inwardly
tapered beam which illuminates the bottom slit pattern 50a. (col. 3, lns.
15-20) Also disclosed are mirrors 32, 36 and 60. (col. 4, lns. 7-11) U.S.
Pat. No. 3,326,077 is incorporated by reference herein for all purposes.
FIG. 1 of the present invention illustrates a conventional K-mirror
assembly. In this K-mirror the scanning mirror M.sub.1 projects a
diverging image onto a 1".times.1" mirror M.sub.2 which in turn reflects
onto a 2".times.2" mirror M.sub.3 which in turn reflects onto a
4".times.5" mirror M.sub.4 to rotate the image. This K-mirror assembly
then transmits the image to the steering mirror M.sub.5 which is sized at
7".times.6" to properly steer the complete image.
A conventional pechan prism to rotate an image is disclosed in U.S. Pat.
No. 4,645,318. Conventional prisms, such as the dove and pechan prisms,
are generally custom manufactured to specification by optic fabrication
shops such as CVI of Albuquerque, N. Mex.; Rocky Mountain Instrument Co.
of Longmont, Colo. and Kollmorgen Corporation of Northampton, Mass.
It has also been known in the past to use optics to collimate an image, as
disclosed in U.S. Pat. Nos. 4,294,506 and 4,906,061. However, the
collimated image has not then been projected through a rotator assembly,
such as a K-mirror, pechan prism or dove prism, to rotate the image
responsive to the horizontal movement of the steering mirror. Moreover,
the angular information of the collimated image has not subsequently been
restored after being transmitted through the rotator assembly so that the
image continues to diverge.
U.S. Pat. No. 4,294,506 discloses an argon laser 36 where the image is
passed through an expander lens 39, comprising a convex lens 39a and a
concave lens 39b, to convert the image into a collimated image, as best
shown in FIG. 4. After the light impinges on the facets 32a of a rotating
polygon mirror 32, the collimated beam is reflected towards a scanning
surface 34. An anamorphic optical system comprising a first convex
cylindrical lens 37 and a condensor lens 33 is disposed intermediate the
rotating polygon mirror 32 and scanning surface 34 to convert the
collimated image to a converging image. (col. 3, lns. 22-40)
U.S. Pat. No. 4,906,061 discloses scanning a surface with a laser light
beam. The light beam is projected through a collimator lens 2 to a
rotating mirror 3, the light beam is deflected by the mirror 3 and applied
through a f.THETA. lens 4 to converge on the surface to be scanned. The
rotating mirror 3, as shown in FIG. 1, may comprise a rotating polygon
mirror or a pyramidal mirror. The collimator lens 2, as best shown in
FIGS. 2A and 2B, is movable along the optical axis to correct the
curvature of the field.
An image mover for a light projector has been desired where the size of the
steering mirror, rotator assembly and their associated parts and motors
are reduced. This size reduction of the steering mirror and rotator
assembly allows higher acceleration and velocity movement of the image
with smaller motors.
SUMMARY OF THE INVENTION
According to the invention, an image mover adapted for use with a laser
light image having angular information is provided. The image mover
comprises a relay or first lens to collimate and relay angular information
of the image from a projector scanning mirror. A rotator assembly such as
a K-mirror, pechan prism or dove prism are used for rotating the
collimated image responsive to the horizontal movement of the steering
mirror. A restoring or second lens, which can either be a fixed focal
length lens or a zoom lens, restores the collimated light image of a size
proportional to the image angular information from the projector scanning
mirror. The restored image is then projected to a steering mirror and
steered onto a viewing surface in real time.
Additionally, the rotator assembly and the steering mirror may move
independently or proportional to each other and are computer assisted for
projection onto single or multiple viewing surfaces. Advantageously, a
series of these relay lenses, restoring lenses and rotator assemblies can
be used alone or with a fiber optic bundle for positioning the image on a
viewing surface remote from the projector.
BRIEF DESCRIPTION OF THE DRAWINGS
The objects, advantages and features of the invention will become more
apparent by reference to the drawings which are appended hereto wherein
like numerals indicate like parts and wherein an illustrated embodiment of
the invention is shown, of which:
FIG. 1 is a conventional K-mirror assembly and steering mirror with a
diverging image;
FIG. 2 is a schematic of the rotator assembly disposed between the relay
lens and the restoring lens which are, in turn, disposed between the
scanning mirror and the steering mirror, respectively;
FIG. 3 is a sectional elevation view of the preferred embodiment of the
present invention;
FIG. 4 is a perspective view of a scanning mirror, relay lens and
intermediate image plane of the present invention;
FIG. 5 is an elevational view of conventional imaging having an infinite
conjugate; and
FIG. 6 is an elevational view of the angular information being transmitted
from the scanning mirror to the relay lens of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
The image mover, generally indicated at 10, can be used with any light
projector but is particularly adapted for use with a laser light
projector, such as disclosed in U.S. Pat. No. 5,136,426. The image mover
10 of the present invention is preferably positioned above the projector
so that the central axis 12 of the image mover 10 is aligned with optical
axis 14 of the vertical scanning mirror 16. A laser light projector is
particularly desirable for use with the present invention since the image
will maintain focus at any desired distance from the projector, i.e. from
the scanning mirror 16 to infinity.
The scanning mirror 16 is similar to the frame scanner S.sub.2 as shown in
FIGS. 1, 3 and 7 or reference number 104 in FIG. 4 of U.S. Pat. No.
5,136,426. As explained in col. 5, lns. 29-48 of U.S. Pat. No. 5,136,426
and as shown in FIGS. 2 and 3 of the invention, the projector P includes a
55 mm lens L.sub.5, a 25 mm cylindrical lens L.sub.6 whose power is in the
vertical direction, but for use with the present invention the lens
L.sub.7 is preferably a 120-125 mm lens to provide the desired throw
distance for the image mover, as will be discussed below in detail.
In general, an image is first projected off the vertical scanning mirror
16. The image is then passed through a first or relay lens 18. Preferably,
the relay lens 18 is an achromat lens for collimating the angular
information provided from the scanning mirror 16. By positioning the relay
lens 18 of the present invention close to the scanning mirror 16,
preferably one focal length of lens 18, the relay lens 18 intercepts the
scanned images before they diverge into a large area requiring the large
rotator assemblies and mirrors along with the motors to operate them. The
collimated image is then passed through the rotator assembly, generally
indicated at 20, such as a K-mirror assembly, as shown in FIGS. 2 and 3 or
a dove prism or pechan prism, as discussed previously. The collimated
image is then transmitted to the second or restoring lens, generally
indicated at 22, to restore the diverging angular information of the
image. This restored image is then transmitted to a steering mirror 24 for
projection onto a viewing surface 26. The viewing surface 26 is defined as
any solid surface 26A, such as a projector screen or wall, or could be a
fluid surface 26B, such as smoke or any other gas or liquid.
As is known to those skilled in the art, laser projection differs from
conventional projection in that all of the angular information of the
projected image is present from the time the laser reflects off the
scanning mirror 16. However, in conventional projection, be it film,
slides, cathode ray tube, liquid crystal, liquid crystal light valve or
oil film light valve projectors, the desired image is created on one plane
and a set of optics, such as an objective lens, is used to relay this
image to the viewing surface. In laser video projection, image planes are
not used. Instead, the combined laser beams, which contain color and
intensity information, are scanned horizontally by the horizontal scanner
to produce a TV line and each line is positioned vertically by the
vertical scanning mirror 16, such as disclosed in U.S. Pat. No. 5,136,426.
Thus, a laser video picture is comprised of video information and angular
information in two orthogonal directions. Only when this diverging set of
laser beams intercepts a viewing surface is an image produced. Therefore,
an image in the laser video projection industry is not an image in the
conventional optical sense but image is defined herein as the information
transmitted by the scanning mirror 16.
Turning to FIG. 6, at one focal length f away from the relay lens 18, an
intermediate image plane 28 is formed. A beam waist is formed at a point
displaced from the optical axis 14 by the product of the focal length
f.sub.18 of the relay lens 18 and the vector sum of the horizontal and
vertical scan angles of the laser video image, as best shown in FIG. 6.
Therefore, at plane 28, one focal length f down the optical axis 14, from
relay lens 18 the scanned laser images are focused to the gaussian beam
waist.
A matrix of the horizontally and vertically scanned image from the scanning
mirror 16 will form a representation of the video image on plane 28. This
representation will not show the detail of the image in all instances
because the beam waist diameter may be greater than the width of one video
line on plane 28. The restoring lens 22 is positioned so that its infinite
conjugate focal point coincides with the plane 28. Then each point, for
example point 30B in FIG. 4, in the plane 28 will correspond with one
unique horizontal and vertical angle originally relayed from relay lens
18, such as pixel 30A of the laser video image. Therefore, each angle of
the restoring lens 22 is proportional to the displacement of the point on
plane 28 from the optical axis 14 and the focal length f.sub.22 of the
restoring lens 22. In this manner, the angular information that constructs
the laser video image is captured by the relay lens 18, collimated and
relayed to | | |
