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Claims  |
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What is claimed is:
1. A beam steering optical system having a system pupil, said system
comprising:
an irradiating optical system producing at least one irradiating light beam
for irradiating an object;
a two-sided rotatable mirror positioned to cover only a first portion of
the system pupil and to reflect with a first surface the at least one
irradiating light beam received from said irradiating optical system;
an objective lens positioned to receive the at least one irradiating light
beam reflected from said two-sided rotatable mirror and to focus the at
least one irradiating light beam on the object,
wherein said irradiating optical system, said two-sided rotatable mirror,
and said objective lens together define an irradiation path for the at
least one irradiating light beam;
a photodetector receiving at least one detecting light beam comprising the
at least one irradiating light beam reflected by the object and then by a
second surface of said two-sided rotatable mirror; and
beam redirecting means for redirecting one of the at least one irradiating
light beam and the at least one detecting light beam,
wherein said irradiating optical system and said photodetector are
positioned so that one of the following occurs:
the at least one irradiating light beam is reflected by the first surface
of said two-sided rotatable mirror to said beam redirecting means which
redirects the at least one irradiating light beam through a second portion
of the system pupil not covered by said two-sided rotatable mirror and
then through said objective lens to the object; and
the at least one detecting light beam reflected by the object passes
through the second portion of the system pupil not covered by said
two-sided rotatable mirror to said beam redirecting means, and is
redirected by said beam redirecting means to the second surface of said
two-sided rotatable mirror which reflects the at least one detecting light
beam to said photodetector;
wherein said two-sided rotatable mirror steers both the at least one
irradiating light beam and the at least one detecting light beam through
the same angle when said two-sided rotatable mirror rotates,
wherein said objective lens, said two-sided rotatable mirror, and said
photodetector together define an observation path for the at least one
detecting light beam, and
wherein the irradiation path and the observation path are spaced from each
other at least at the system pupil.
2. The system defined by claim 1,
wherein said objective lens receives the at least one detecting light beam
reflected by the object and directs the at least one detecting light beam
to the second portion of the system pupil not covered by said two-sided
rotatable mirror, and
wherein said beam redirecting means is positioned to receive the at least
one detecting light beam after passing through the second portion of the
system pupil, and redirects the at least one detecting light beam to the
second surface of said two-sided rotatable mirror, said second surface of
said two-sided rotatable mirror reflecting the at least one detecting
light beam to said photodetector,
wherein said objective lens, said two-sided rotatable mirror, said beam
redirecting element, and said photodetector together define the
observation path for the at least one detecting light beam.
3. The system defined by claim 1,
wherein said beam redirecting means is positioned to receive the at least
one irradiating light beam after being reflected by said first surface of
said two-sided rotatable mirror and redirects the at least one irradiating
light beam through the second portion of the system pupil to said
objective lens, and
wherein said irradiating optical system, said objective lens, said
two-sided rotatable mirror, and said beam redirecting element together
define the irradiation path for the at least one irradiating light beam.
4. The system defined by claim 1, wherein said beam redirecting means
comprises two mirrors extending to form a ninety degree angle therebetween
and having surfaces facing each other, wherein the two mirrors intersect
along an axis parallel to the rotation axis of said two-sided rotatable
mirror.
5. The system defined by claim 1, wherein said beam redirecting means
comprises at least a curved or flat mirror coaxial with the optical axis
of said objective lens, making the system pupil conjugate with the second
surface of said two-sided rotatable mirror at a magnification of
substantially -1.
6. The system defined by claim 1, wherein said two-sided rotatable mirror
is rotatable around two perpendicular axes for steering the at least one
irradiating light beam and the at least one detecting light beam
two-dimensionally, wherein said beam redirecting means is constructed to
redirect the at least one detecting light beam in two perpendicular planes
corresponding to the rotating direction of said two-sided rotatable
mirror.
7. The system defined by claim 1, further comprising a second rotatable
mirror for steering the at least one irradiating light beam and the at
least one detecting light beam, the rotation axis of said second rotatable
mirror being perpendicular to the rotation axis of said two-sided
rotatable mirror.
8. The system defined by claim 1, further comprising:
a second rotatable mirror, for steering the at least one irradiating light
beam, located between said irradiating optical system and said two-sided
rotatable mirror, wherein the rotation axis of said second rotatable
mirror is perpendicular to the rotation axis of said two-sided rotatable
mirror;
a third rotatable mirror, for steering the at least one detecting light
beam, located between said photodetector and said two-sided rotatable
mirror, wherein the rotation axis of said third rotatable mirror is
perpendicular to the rotation axis of said two-sided rotatable mirror,
wherein said third rotatable mirror rotates simultaneously through the
same angle as said second rotatable mirror;
a first relay optical system for making the system pupil conjugate with
said second rotatable mirror; and
a second relay optical system for making the system pupil conjugate with
said third rotatable mirror.
9. An ophthalmic apparatus comprising:
an irradiating optical system comprising at least one light source
producing at least one irradiating light beam for irradiating an eye;
an objective lens positioned to receive the at least one irradiating light
beam to focus the at least one irradiating light beam on the eye;
a detecting optical system, comprising at least one photodetector, for
receiving at least one detecting light beam comprising the at least one
irradiating light beam reflected by the eye; and
a beam steering optical system, having a system pupil, comprising:
a two-sided rotatable mirror positioned to cover only a first portion of
the system pupil and to reflect with a first surface thereof the at least
one irradiating light beam received from said irradiating optical system
and to reflect to said at least one photodetector with a second surface
thereof the at least one detecting light beam reflected by the eye; and
beam redirecting means for redirecting one of the at least one irradiating
light beam and the at least one detecting light beam;
wherein said irradiating optical system and said at least one photodetector
are positioned so that one of the following occurs:
the at least one irradiating light beam is reflected by the first surface
of said two-sided rotatable mirror to said beam redirecting means which
redirects the at least one irradiating light beam through a second portion
of the system pupil not covered by said two-sided rotatable mirror and
then through said objective lens to the eye; and
the at least one detecting light beam reflected by the eye passes through
the second portion of the system pupil not covered by said two-sided
rotatable mirror to said beam redirecting means, and is redirected by said
beam redirecting means to the second surface of said two-sided rotatable
mirror which reflects the at least one detecting light beam to said at
least one photodetector,
wherein said objective lens makes the pupil of the eye conjugate with the
system pupil,
wherein said irradiating optical system, said two-sided rotatable mirror,
and said objective lens together define an irradiation path for the at
least one irradiating light beam;
wherein said objective lens, said two-sided rotatable mirror, and said
detecting optical system together define an observation path for the at
least one detecting light beam,
wherein said two-sided rotatable mirror steers both the at least one
irradiating light beam and the at least one detecting light beam through
the same angle when said two-sided rotatable mirror rotates, and
wherein the irradiation path and the observation path are spaced from each
other at least at the system pupil.
10. The apparatus defined by claim 9,
wherein said objective lens receives the at least one detecting light beam
reflected by the eye and directs the at least one detecting light beam to
the second portion of the system pupil not covered by said two-sided
rotatable mirror, and
wherein said beam redirecting means is positioned to receive the at least
one detecting light beam after passing through the second portion of the
system pupil, and redirects the at least one detecting light beam to the
second surface of said two-sided rotatable mirror, said second surface of
said two-sided rotatable mirror reflecting the at least one detecting
light beam to said at least one photodetector,
wherein said objective lens, said two-sided rotatable mirror, said beam
redirecting element, and said at least one photodetector together define
the observation path for the at least one detecting light beam.
11. The apparatus defined by claim 9,
wherein said beam redirecting means is positioned to receive the at least
one irradiating light beam after being reflected by said first surface of
said two-sided rotatable mirror and redirects the at least one irradiating
light beam through the second portion of the system pupil to said
objective lens, and
wherein said irradiating optical system, said objective lens, said
two-sided rotatable mirror, and said beam redirecting element together
define the irradiation path for the at least one irradiating light beam.
12. The apparatus defined by claim 9, further comprising control means for
controlling the rotation angle of said two-sided rotatable mirror in
accordance with an output signal from said at least one photodetector to
stabilize the position of the at least one irradiating light beam on the
eye at least in one dimension when the eye moves.
13. The apparatus defined by claim 9, wherein said at least one light
source comprises a first laser emitting a first laser light beam, wherein
said irradiating optical system further comprises a second laser emitting
a second laser light beam, wherein said irradiating optical system further
comprises means for combining the first and second laser light beams into
a single combined laser beam and for directing the single combined laser
beam to said two-sided rotatable mirror.
14. A beam steering method for steering a beam in a beam steering system
having a system pupil, comprising:
a first step of producing at least one irradiating light beam with an
irradiating optical system for irradiating an object and projecting the at
least one irradiating light beam to a first portion of the system pupil;
a second step of reflecting the at least one irradiating light beam at the
first portion of the system pupil with a first surface of a two-sided
rotatable mirror to the object;
wherein said first and second steps together define an irradiation path for
the at least one irradiating light beam;
a third step of reflecting the at least one irradiating light beam from the
object as at least one detecting light beam to a second surface of the
two-sided rotatable mirror, and reflecting the at least one detecting
light beam from the second surface of the two-sided rotatable mirror to a
photodetector;
a fourth step of redirecting one of the at least one irradiating light beam
and the at least one detecting light beam;
a fifth step of positioning the irradiating optical system and the
photodetector so that one of the following sequences of steps occurs:
reflecting the at least one irradiating light beam with the first surface
of the two-sided rotatable mirror, and redirecting the reflected at least
one irradiating light beam, reflected by the first surface of the
two-sided rotatable mirror, through a second portion of the system pupil
not covered by the two-sided rotatable mirror to the object; and
projecting the at least one detecting light beam reflected by the object
through the second portion of the system pupil not covered by the
two-sided rotatable mirror, redirecting the at least one detecting light
beam having passed through the second portion of the system pupil to the
second surface of the two-sided rotatable mirror, and reflecting the at
least one detecting light beam from the second surface of the two-sided
rotatable mirror to the photodetector; and
a sixth step of steering both the at least one irradiating light beam and
the at least one detecting light beam through the same angle when the at
least one irradiating light beam is reflected by the first surface of the
two-sided rotatable mirror and when the at least one detecting light beam
is reflected by the second surface of the two-sided rotatable mirror;
wherein said third step defines an observation path for the at least one
detecting light beam,
wherein all of the steps of said method are performed so that the
irradiation path and the observation path are spaced from each other at
least at the system pupil. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a beam steering optical system. More
particularly, the present invention relates to an optical system for
steering or redirecting light beams in forward and reverse directions
through an objective lens and a steering optical system. The present
invention is also directed to an ophthalmic apparatus using such a beam
steering optical system.
2. Description of the Related Art
In optical devices, such as scanning laser microscopes, an irradiating beam
for irradiating the eye is directed along an irradiating path to x and y
axis steering mirrors before being focused at a target within the eye. A
detecting beam reflected from the target is imaged back along
substantially the same irradiating path to the x and y axis steering
mirrors before it is split off from the irradiating path and directed to a
photodetector or an imaging device. More generally, an optical system used
in a clinical setting may require one or more irradiating beams and one or
more detecting beams to be all steered together using one or more mirrors.
In such a system, the irradiating beam may be a diagnostic probing beam
such as the red beam of a laser Doppler instrument, or a treatment beam,
such as a point-focused surgical laser beam. Direct illumination of the
eye may also be provided independently of the steering mirror or mirrors,
for example, by flooding the eye with sufficient light to view the field
of clinical interest in the eye. The detecting beam or beams reflected by
the eye may be focused to produce a visual image, converted by a
photodetector to a localized tracking image signal, converted to a tissue
reflectance value used for laser intensity control, or processed in some
other way. In such instruments, it is desirable for the treatment light
beam and the detecting light beam to pass through steering mirrors to vary
the field of treatment or observation, respectively.
One instrument of this type is described in U.S. Pat. No. 4,856,891. This
patent discloses an eye fundus tracker/stabilizer using a common steering
system to steer a narrow diagnostic or treatment light beam toward the eye
and to receive light returning from the eye as a return image. The
advantage of such a beam steering system is that by moving a steering
mirror or mirrors to stabilize the position of the return image, the
diagnostic or treatment light beam incident on the eye is automatically
maintained at a stable location on the eye fundus bearing a fixed spatial
relationship to the imaged area. However, when such a system is used to
observe or treat a target on the fundus of an eye, the relatively intense
diagnostic or treatment light input into the instrument to irradiate the
eye scatters in the steering assembly, adding substantial noise to the
extremely weak light returning from the eye. In addition, when it is
desired to position a steering mirror and one or more stops confocal with
the observed field or with the pupil of the eye, precision is required in
locating or aligning the beam with respect to these elements. This
structure complicates the problem of maintaining sufficiently distinct
paths for the input light and the return light, and further compounds the
noise and cross-talk problems.
U.S. Pat. Nos. 5,094,523 and 5,106,184 propose solutions to these problems.
These patents disclose a two dimensional light steering apparatus
comprising a pair of pivotable beam-directing elements, each having first
and second faces. A beam traveling in a first direction is redirected by
the first face of both elements, and a beam traveling in the second
direction is redirected by the second face of both elements. The elements
are preferably relatively thin planar mirrors (so called two-sided
mirrors) which each steer the light about one of two axes. The first and
second faces each perform a virtually identical purely pivotal steering
motion to provide a wide field scan which is not occluded by system
pupils. Steering in two dimensions may be employed for irradiating an eye
and detecting light reflected therefrom through a common objective lens
assembly. This structure allows highly efficient and jitter-free imaging,
while providing effective input/output beam separation for such difficult
applications as simultaneously treating and imaging the fundus of the eye.
However, the apparatus disclosed in U.S. Pat. Nos. 5,094,523 and 5,106,184
is complicated because they are designed for two-dimensional beam steering
and two-dimensional imaging. For example, the irradiating beam path and
the detecting beam path cross each other in the beam steering optical
system. This limits one's flexibility in aligning the optical elements
comprising the steering optical system itself and other systems such as
the irradiating optical system (which produces a suitable shape for the
irradiating beam) and the light detecting optical system which contains
stops and detectors. Such a complicated structure is not needed for
one-dimensional beam steering, used, for example, in a laser Doppler
instrument for measuring retinal vessel blood flow.
Thus, there is a need for a beam steering optical system and an ophthalmic
instrument using beam steering that is simple in structure which generates
little noise and cross-talk between an irradiating beam irradiating the
eye and a detection beam reflected by the eye. There is also a need for a
beam steering optical system and an ophthalmic instrument using beam
steering that maintains distinct paths for the irradiating light and the
detecting light. In addition, there is a need for a one-dimensional beam
steering apparatus which generates low amounts of noise and little
cross-talk between an irradiating beam irradiating the eye and a detection
beam reflected by the eye.
SUMMARY OF THE INVENTION
It is an object of the present invention to overcome the problems noted
above.
It is another object of the present invention to provide a beam steering
optical system and an ophthalmic instrument using beam steering that is
simple in structure which generates little noise and cross-talk between an
irradiating beam irradiating the eye and a detection beam reflected by the
eye.
It is still another object of the present invention to provide a beam
steering optical system and an ophthalmic instrument using beam steering
that maintains distinct paths for the irradiating light and the detecting
light.
It is a further object of the present invention to provide a
one-dimensional beam steering apparatus which generates low amounts of
noise and little cross-talk between an irradiating beam irradiating the
eye and a detecting beam reflected by the eye.
According to one aspect, the present invention which achieves one or more
of these objectives relates to a beam steering optical system having a
system pupil. The system comprises an irradiating optical system, a
two-sided rotatable mirror, an objective lens, beam redirecting means, and
a position-sensing photodetector. The irradiating optical system produces
at least one irradiating light beam for irradiating an object. The
two-sided rotatable mirror is positioned to cover only a first portion of
the system pupil and to reflect with a first surface the at least one
irradiating light beam received from the irradiating optical system. The
objective lens is positioned to receive the at least one irradiating light
beam reflected from the two-sided rotatable mirror and to focus the at
least one irradiating light beam on the object.
The irradiating optical system, the two-sided rotatable mirror, and the
objective lens together define an irradiation path for the at least one
irradiating light beam. In addition, the objective lens, the two-sided
rotatable mirror, and the photodetector together define an observation
path for the at least one detecting light beam.
The photodetector is positioned to receive at least one detecting light
beam comprising the at least one irradiating light beam reflected by the
object and then by a second surface of the two-sided rotatable mirror. The
beam redirecting means redirects one of the at least one irradiating light
beam and the at least one detecting light beam.
The irradiating optical system and the photodetector are positioned so that
one of the following two arrangements occurs. In a first arrangement the
at least one detecting light beam reflected by the object passes through
the second portion of the system pupil not covered by the two-sided
rotatable mirror to the beam redirecting means. The beam redirecting means
redirects the at least one detecting light beam to the second surface
(nearer to the photodetector) of the two-sided rotatable mirror. The
second surface of the two-sided rotatable mirror then reflects the at
least one detecting light beam to the photodetector. In a second
arrangement the at least one irradiating light beam is reflected by the
first surface (nearer to the light source) of the two-sided rotatable
mirror to the beam redirecting means. The beam redirecting means redirects
the at least one irradiating light beam through a second portion of the
system pupil not covered by the two-sided rotatable mirror and then
through the objective lens to the object.
By interchanging the light source of the irradiating optical system and the
photodetector, the observation path and the irradiation path can be
reversed, and the first arrangement can be changed to the second
arrangement and vice versa.
The two-sided rotatable mirror steers both the at least one irradiating
light beam and the at least one detecting light beam through the same
angle when the two-sided rotatable mirror rotates. In order to prevent
cross-talk between the at least one irradiating light beam and the at
least one detecting light beam, the irradiation path and the observation
path are spaced from each other at least at the system pupil.
According to another aspect, the present invention which achieves one or
more of these objectives relates to an ophthalmic apparatus comprising an
irradiating optical system, a beam steering optical system, an objective
lens, and a detecting optical system.
The irradiating optical system comprises at least one light source
producing at least one irradiating light beam for irradiating an eye. The
objective lens is positioned to receive the at least one irradiating light
beam to focus the at least one irradiating light beam on the eye. The
detecting optical system comprises at least one photodetector, and
receives at least one detecting light beam comprising the at least one
irradiating light beam reflected by the eye. The beam steering optical
system has a system pupil and comprises a two-sided rotatable mirror and
beam redirecting means.
The two-sided rotatable mirror is positioned to cover only a first portion
of the system pupil and to reflect with a first surface thereof the at
least one irradiating light beam received from the irradiating optical
system. In addition, the two-sided rotatable mirror reflects to the at
least one photodetector with a second surface thereof the at least one
detecting light beam reflected by the eye.
The beam redirecting means redirects one of the at least one irradiating
light beam and the at least one detecting light beam. The irradiating
optical system and the at least one photodetector are positioned so that
one of the following two arrangements occurs. In the first arrangement the
at least one irradiating light beam is reflected by the first surface of
the two-sided rotatable mirror to the beam redirecting means. The beam
redirecting means redirects the at least one irradiating light beam
through a second portion of the system pupil not covered by the two-sided
rotatable mirror and then through the objective lens to the eye. In the
second arrangement the at least one detecting light beam reflected by the
eye passes through the second portion of the system pupil not covered by
the two-sided rotatable mirror to the beam redirecting means. The beam
redirecting means redirects the at least one detecting light beam to the
second surface of the two-sided rotatable mirror. The second surface of
the two-sided rotatable mirror reflects the at least one detecting light
beam to the at least one photodetector.
In this embodiment the objective lens makes the pupil of the eye conjugate
with the system pupil. In addition, the irradiating optical system, the
two-sided rotatable mirror, and the objective lens together define an
irradiation path for the at least one irradiating light beam. Also, the
objective lens, the two-sided rotatable mirror, and the detecting optical
system together define an observation path for the at least one detecting
light beam.
By interchanging the light source of the irradiating optical system and the
photodetector, the observation path and the irradiation path can be
reversed, and the first arrangement can be changed to the second
arrangement, and vice versa.
The two-sided rotatable mirror steers both the at least one irradiating
light beam and the at least one detecting light beam through the same
angle when the two-sided rotatable mirror rotates. In order to prevent
cross-talk between the at least one irradiating light beam and the at
least one detecting light beam, the irradiation path and the observation
path are spaced from each other at least at the system pupil.
According to another aspect, the present invention which achieves one or
more of these objectives relates to a beam steering method for steering a
beam in a beam steering system having a system pupil. The method comprises
a first step of producing at least one irradiating light beam with an
irradiating optical system for irradiating an object and projecting the at
least one irradiating light beam to a first portion of the system pupil.
The method also comprises a second step of reflecting the at least one
irradiating light beam at the first portion of the system pupil with a
first surface of a two-sided rotatable mirror to the object. The first and
second steps together define an irradiation path for the at least one
irradiating light beam.
The method further comprises a third step of reflecting the at least one
irradiating light beam from the object as at least one detecting light
beam to a second surface of the two-sided rotatable mirror, and reflecting
the at least one detecting light beam from the second surface of the
two-sided rotatable mirror to a photodetector. In addition, the method
comprises a fourth step of redirecting one of the at least one irradiating
light beam and the at least one detecting light beam.
The method also comprises a fifth step of positioning the irradiating
optical system and the photodetector so that one of the following two
sequences of steps occurs. The first sequence of steps comprises
reflecting the at least one irradiating light beam with the first surface
of the two-sided rotatable mirror, and redirecting the reflected at least
one irradiating light beam, reflected by the first surface of the
two-sided rotatable mirror, through a second portion of the system pupil
not covered by the two-sided rotatable mirror to the object. The second
sequence comprises projecting the at least one detecting light beam
reflected by the object through the second portion of the system pupil not
covered by the two-sided rotatable mirror, redirecting the at least one
detecting light beam having passed through the second portion of the
system pupil to the second surface of the two-sided rotatable mirror, and
reflecting the at least one detecting light beam from the second surface
of the two-sided rotatable mirror to the photodetector.
The method also comprises a sixth step of steering both the at least one
irradiating light beam and the at least one detecting light beam through
the same angle when the at least one irradiating light beam is reflected
by the first surface of the two-sided rotatable mirror and when the at
least one detecting light beam is reflected by the second surface of the
two-sided rotatable mirror.
The third step defines an observation path for the at least one detecting
light beam. In addition, in order to prevent cross-talk between the at
least one irradiating light beam and the at least one detecting light
beam, all of the steps of the method are performed so that the irradiation
path and the observation path are spaced from each other at least at the
system pupil.
According to another aspect, the present invention which achieves one or
more of these objectives relates to a beam steering optical system having
a system pupil. The system comprises an irradiating optical system, a
two-sided mirror, an objective lens, and a photodetector. The irradiating
optical system produces at least one irradiating light beam for
irradiating an object. The two-sided mirror is positioned to cover only a
first portion of the system pupil. The two-sided mirror is also positioned
to reflect with a first surface the at least one irradiating light beam
received from the irradiating optical system and to reflect with a second
surface at least one detecting light beam comprising the at least one
irradiating light beam reflected from the object. The objective lens is
positioned to receive the at least one irradiating light beam reflected
from the first surface of the two-sided mirror and to focus the at least
one irradiating light beam on the object.
The irradiating optical system, the two-sided mirror, and the objective
lens together define an irradiation path for the at least one irradiating
light beam. In addition, the photodetector is positioned to receive at the
least one detecting light beam reflected by the second surface of the
two-sided mirror. Also, the objective lens, the two-sided mirror, and the
photodetector together define an observation path for the at least one
detecting light beam. Moreover, one of the irradiation path and the
observation path intersects the first portion of the system pupil and the
other one of the irradiation path and the observation passes through a
second portion of the system pupil not covered by the two-sided mirror. In
addition, to prevent cross-talk between the at least one irradiating light
beam and the at least one detecting beam the irradiation path and the
observation path are spaced from each other at least at the system pupil.
These and other features and advantages of the present invention will be
more readily understood upon reviewing the following detailed description
of preferred embodiments taken in conjunction with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a schematic view of a first embodiment of the present invention.
FIG. 1B is a schematic view of an alternative embodiment of the first
embodiment of the present invention.
FIG. 2 is a schematic view of the system pupil of the embodiment shown in
FIG. 1A when viewed from the objective lens 5.
FIG. 3 is a schematic view of a second embodiment of the present invention.
FIG. 4 is schematic view of a third embodiment of the present invention.
FIG. 5 is a schematic view of a fourth embodiment of the present invention.
FIG. 6 is a schematic view of a fifth embodiment of the present invention.
FIG. 7A is a schematic side view of a sixth embodiment of the present
invention.
FIG. 7B is a schematic bottom view of the apparatus shown in FIG. 7A in the
direction A.
FIG. 8 is a schematic view of images 56', 59', 101a', 101b', 123', 127',
135a', 135b', and 137' on the eye pupil Ep.
FIG. 9 is a schematic view of a fundus image displayed on a TV monitor 65.
FIG. 10 is a graph of the result of a frequency analysis of a signal
detected by one of the photomultiplier tubes 135a, 135b.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
A first embodiment of the present invention is the one-dimensional steering
optical system shown in FIG. 1A. The system includes an irradiating
optical system comprising a laser source 1, which emits an irradiating
beam 2 irradiating an object such as the fundus Ef of an eye E of an
examinee. This is accomplished by first passing the irradiating beam 2
through a lens 3a of the irradiating optical system 3 positioned in front
of the laser source 1. The irradiating beam 2 is incident on the lens 3a
at a position spaced from the optical axis 3b thereof. The lens 3a directs
the irradiating beam 2 to cross the optical axis 3b along an irradiating
path to a lens 3c of the irradiating optical system. The irradiating beam
2 is incident on the lens 3c at a position spaced from the optical axis
thereof, which is also the axis 3b. As a result, the optical axis 3b is
the optical axis of the irradiating optical system. The irradiating
optical system 3 directs the irradiating beam 2 onto a first (front)
surface 4a of a two-sided rotatable mirror 4. The first surface 4a of the
two-sided rotatable mirror 4 reflects the irradiating beam 2 to an
objective lens 5 facing the examinee's eye E at a point spaced from and
above the optical axis 5a thereof. The objective lens 5 directs the
irradiating beam 2 onto the fundus Ef of the eye E.
The two-sided rotatable mirror 4 is located at and covers only a portion of
the system pupil. The system pupil is located on a plane perpendicular to
the optical axis 5a of the objective lens 5 around the point at which this
plane crosses the optical axis 3b of the irradiation optical system. The
two-sided rotatable mirror 4 pivots and steers the irradiating beam 2
about an axis 4o, which is perpendicular to the optical axis 3b of the
irradiating optical system on this plane. The axis 4o also extends along
the edge of the mirror 4 closest to the lens 3c of the irradiating optical
system. This edge is positioned at the intersection of the optical axis 5a
of the objective lens 5 and the optical axis 3b of the irradiating optical
system. Alternatively, the axis 4o can extend along other lines
perpendicular to the optical axis 3b of the irradiating optical system and
the edge can be spaced from the intersection of the axes 5a and 3b. By
such an arrangement, the two-sided rotatable mirror 4 covers only half of
the system pupil. As a result, the irradiating beam 2 is incident on this
half of the system pupil and is reflected by the first surface 4a, while a
beam reflected from the eye E, passes through the other half of the system
pupil and does not strike the first surface of the two-sided rotatable
mirror 4, as will be discussed below.
The objective lens 5 is so positioned as to make the system pupil conjugate
with the pupil Ep of the examinee's eye E. Consequently, the irradiating
beam 2 travels through only one half of the pupil Ep of the examinee's eye
E. As the two-sided rotatable mirror 4 rotates, the irradiating beam 2 is
steered to irradiate, through the pupil Ep, one point on a particular line
on the eye fundus Ef.
The light source 1, the lens 2, the lenses 3b and 3c of the irradiating
optical system, the two-sided rotatable mirror 4, and the objective lens 5
together define an irradiation path for the irradiating beam 2 from the
light source 1 to the eye E.
The light reflected by the point on the fundus Ef is called a detecting
beam 6. The detecting beam 6 is directed close to but separated from the
irradiating path followed by the irradiating beam 2 and in the reverse
direction. Thus, the detecting beam 6 passes through the other half of the
pupil Ep, travels below the optical axis 5a to the objective lens 5, and
passes through the other half of the system pupil not covered by the
two-sided rotatable mirror 4. This latter feature is accomplished by the
eccentric location of the two-sided rotatable mirror 4 or its asymmetrical
shape.
FIG. 2 shows the system pupil of FIG. 1A when viewed from the objective
lens 5. The system pupil appears as a square, the lower half of which is
covered by the first surface 4a of the two-sided rotatable mirror 4. This
is illustrated by the solid rectangle labelled 4a. The circle labelled 2'
denotes the cross-section of the irradiating beam 2 which is reflected by
the first surface 4a. The upper half of the system pupil is shown as a
rectangle in dashed lines and is denoted by 4a'. The detecting beam 6
passes through the upper half 4a' of he system pupil. This is shown by the
circle labelled 6', which denotes the cross-section of the detecting beam
6.
The detecting beam 6, after passing through the upper half 4a' of the
system pupil, strikes a beam redirecting system for redirecting the
detecting beam 6. In this embodiment the beam redirecting system comprises
a curved relay mirror 7, which flips the detecting beam 6 and redirects it
to the second surface 4b of the two-sided rotatable mirror 4. As the
two-sided rotatable mirror 4 rotates, the second surface 4b performs a
steering correction on the detecting beam 6, which is in the opposite
direction to the steering operation performed by the first surface 4a on
the irradiating beam 2, but of the same magnitude. This is accomplished
because, as the two-sided rotatable mirror 4 rotates, it rotates the
irradiating beam 2 and the detecting beam 6 through the same angle
simultaneously.
The center of curvature of the curved relay mirror 7 is located at the
center of the system pupil. Therefore, the second surface 4b of the
two-sided rotatable mirror 4 is conjugate with the upper half 4a' of the
system pupil at a magnification of -1. Moreover, as a result, the position
of the detecting beam 6 on the second surface 4b and the position of the
detecting beam 6 on the system pupil as indicated by 6' in FIG. 2 are
symmetrically located with respect to the x axis shown in FIG. 2. In
addition, the position of the detecting beam 6 on the second surface 4b is
almost the same as the position of the irradiating beam 2 on the first
surface 4a, which is indicated by 2' in FIG. 2, except that these two
beams are reflected by different surfaces of the two-sided rotatable
mirror 4.
The second surface 4b reflects the detecting beam 6 to a position-sensing
photodetector 8 through a detecting optical system 9. The detecting
optical system 9 comprises a lens 9a having an optical axis 9b, and an
eccentric aperture 10. The eccentric aperture 10 is located between the
two-sided rotatable mirror 4 and the lens 9a and is spaced from the
optical axis 9b of the detecting optical system 9. From the second surface
4b, the detecting beam 6 passes through the eccentric aperture 10 and
travels to the lens 9a off axis from axis 9b, which focuses the detecting
beam 6 on the position-sensing photodetector 8.
Thus, the objective lens 5, the curved relay mirror 7, the two-sided
rotatable mirror 4, the eccentric aperture 10, the lens 9a, and the
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