U.S. patent number 3,782,823 [Application Number 05/237,421] was granted by the patent office on 1974-01-01 for laser microprobe.
This patent grant is currently assigned to American Optical Corporation. Invention is credited to Donald H. Hansen, Joseph W. Kantorski, David A. La Marre, Donald A. Smith, Milton R. Thorburn.
United States Patent |
3,782,823 |
Kantorski , et al. |
January 1, 1974 |
LASER MICROPROBE
Abstract
A laser microprobe including a laser and microscope in
combination with variable attenuators and pinholes to direct
radiation at a microscope object and to spectroscopically analyze
the effects thereof. A combined shutter and occluder permit
observation through the eyepiece for alignment and subsequent
discharge of the laser without danger to the operator.
Inventors: |
Kantorski; Joseph W.
(Southbridge, MA), Smith; Donald A. (Woodstock, CT), La
Marre; David A. (Woodstock, CT), Hansen; Donald H.
(Williamsville, NY), Thorburn; Milton R. (Southbridge,
MA) |
Assignee: |
American Optical Corporation
(Southbridge, MA)
|
Family
ID: |
22893639 |
Appl.
No.: |
05/237,421 |
Filed: |
March 23, 1972 |
Current U.S.
Class: |
356/318; D16/131;
219/121.62; 219/121.73; 359/389; 600/473; 219/121.6; 219/121.83;
606/4 |
Current CPC
Class: |
G01J
3/0213 (20130101); G01J 3/02 (20130101) |
Current International
Class: |
G01J
3/02 (20060101); G01J 3/00 (20060101); G01j
003/02 () |
Field of
Search: |
;331/94.5A ;356/85,86
;350/81 ;219/121L |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Peppers et al.: Analytical Chemistry, Vol. 40, No. 8, July 1968,
pages 1178-1182. .
Peppers: Applied Optics, Vol. 4, No. 5, May 1965, pages 555-558.
.
Rasberry et al.: Applied Optics, Vol. 6, No. 1, January 1967, pages
81-86. .
Rasberry et al.: Applied Optics, Vol. 6, No. 1, January 1967, pages
87-93..
|
Primary Examiner: Wibert; Ronald L.
Assistant Examiner: Evans; F. L.
Attorney, Agent or Firm: William C. Nealon et al.
Claims
What is claimed is:
1. A microprobe apparatus including:
a frame,
a laser connected to said frame and disposed along a horizontal
first optical axis,
a microscope connected to said frame and including a body with an
eyepiece and an objective thereon along a microscope optical path
and in operative relationship to an object holder,
a dichroic mirror connected to said body, between said eyepiece and
said objective, in both said optical path and said first horizontal
optical axis and at about 45.degree. relative to said horizontal
first optical axis such that said horizontal first optical axis is
deflected to a second optical axis by said mirror to coincide with
said optical path,
a reticle projection unit connected to said body of said microscope
and effective to project, along a first projection axis, an image
of a reticle and reflect the same along a second projection axis
from the side of said dichroic mirror opposite that upon which
radiation from said laser is incident, said reticle image being
visible through said eyepiece in superimposed relationship to the
object image field, attitude adjustment means to align said second
projection axis coincident with said optical path,
means to transmit radiation from said laser to said mirror so as to
direct the same through said objective at a desired target on said
object holder, and
a pinhole carrier including a plurality of radial web projections
and mounted for rotation in the plane parallel to said first
optical axis, each of said web projections having means for
mounting a pinhole of a different size for selective placement of
the same on said first optical axis, thus to control the spot size
of the laser radiant energy incident upon said target.
2. A microprobe apparatus as defined in claim 1, further
including:
an illuminator mounted on the body of said microscope and effective
to direct light thereinto along an illumination axis,
a beam splitter mounted within said body and positionable on said
illumination axis and at an angle relative thereto such that said
illumination axis is deflected by said beam splitter to coincide
with said optical path,
said beam splitter being movably mounted relative to said optical
path and interconnected with said laser so that when said laser is
operating, said beam splitter is out of said optical path.
3. A microprobe apparatus as defined in claim 1, and further
including:
a battery of attenuators of different densities mounted for
selective placement, one at a time, within said first optical axis
to control the transmission of laser energy therefrom along said
optical axis.
4. A microprobe apparatus as defined in claim 1, and further
including:
a partial reflector disposed in said first optical axis and
effective to reflect a known portion of the laser radiant energy
incident thereupon, and
an energy monitor including a photo diode disposed in the path of
radiant energy reflected from said partial reflector and means to
correlate said reflected radiant energy to the total energy output
from said laser.
5. A microprobe apparatus as defined in claim 2 in which said beam
splitter is mounted relative to said body on an electrical solenoid
device and movable therewith into and out of said optical path,
and further including an occluder mounted to said solenoid device
for movement therewith into and out of said optical path, said
occluder traversing said optical path between said dichroic mirror
and said eyepiece,
said occluder being in a position out of said optical path when
said beam splitter is in a position in said optical path, and visa
versa.
Description
BACKGROUND OF THE INVENTION
The present invention relates to spectroscopy, particularly
spectroscopy in which a laser is used to supply energy to a
specimen under examination. More particularly, this invention
relates to a combined laser, microscope and optical system by which
radiant energy from the laser is directed to a specimen and its
effects analyzed.
Laser spectroscopy, by itself, is known to the prior art, and is
disclosed, for example, in U.S. Pat. No. 3,463,591, issued to
Franken, Cross, and Cross. The Franken et al patent discloses the
concept of a laser apparatus to direct radiant energy onto a small
area of specimen in order to vaporize the same almost
instantaneously. The vapor is then analyzed in a spectroscope to
determine its constituent elements. The means by which the
foregoing functions are accomplished are only schematically
represented.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a laser
microprobe for use in spectroscopy.
Another object is to provide a laser microprobe with means to
insure that destructive radiation from the laser is not incident
upon the observer's eye.
Another object is to provide such an apparatus with improved
accuracy of alignment between laser, microscope, and specimen.
Another object is to provide such an apparatus having a range of
adjustability of radiation level and target sizes.
Further objects, advantages, and features of this invention will
become apparent from the following description of one embodiment
thereof, given in connection with the accompanying drawing.
Briefly, the present invention is practiced in one form by a laser
aligned with a variable attenuator, variable pinhole and optics for
transmission of radiation from the laser into a microscope and onto
an object mounted relative to the microscope. A combination shutter
and occluder permit eyepiece observation with visible light and
laser discharge onto the object with the light path between object
and eyepiece occluded to prevent damage to the observer's eyes.
DRAWING
FIG. 1 is a top plan view of a combined laser, filter wheel,
pinhole assembly, and prism mount for use in association with a
microscope.
FIG. 2 is a front elevation view of the apparatus shown in FIG. 1,
additionally showing an associated microscope.
FIG. 3 is a side elevation view showing part of the microscope of
FIG. 2 from the right end thereof.
DESCRIPTION
Referring now to FIG. 1, a laser is shown at 2. Laser 2 is
preferably a neodymium glass laser emitting at 1.06 micron
wavelength in the near infrared. Laser 2 is mounted on a base plate
or frame 4 by means of a pair of clamps 6, each of these clamps
having vertical and horizontal adjustment screws 8 and 10
respectively for the alignment of the laser 2. Clamps 6 are mounted
to the frame 4 by suitable fasteners shown for example at 12.
An attenuator disk 14 defines a plurality of apertures spaced
circumferentially with respect thereto and is mounted on a filter
wheel assembly 16 which is in turn mounted by suitable fasteners 12
to the frame 4. Filter wheel assembly 16 also mounts a disk drive
motor 18 for rotation in a vertical plane of the attenuator disk 14
which is connected to the motor 18. The apertures, one of which is
represented at 20, in disk 14, are arranged so that their centers
are positionable, one at a time, at the optical axis 22 of the
laser 2 and associated system. In other words, by the rotatability
of disk 14, each of its apertures 20 can be placed in the optical
axis 22 of the system. Motor 18 is suitably controlled so as to
rotate disk 14 and stop it at desired positions. Filters or
attenuators of differing densities are mounted in several of the
apertures 20, one of which is left clear. In one specific
embodiment, the filter wheel or attenuator disk 14 carries four
calibrated attenuators in addition to one open aperture, by which
10 percent, 25 percent, 50 percent, 75 percent and 100 percent of
the energy from the laser 2 is transmitted.
A lens 24 is disposed along the optical axis 22 and is mounted to
the frame 4 by suitable fasteners 12.
A pinhole assembly, generally indicated at 26 is mounted to the
frame 4 by fasteners 12, and includes a pair of horizontal frame
plates 28 and 30, one mounted on the other and spaced therefrom by
a plurality of vertical struts 32. A pinhole drive motor 34 is in
turn mounted atop frame plate 30 by means of vertical struts 36.
Drive motor 34 is a low torque motor and is operatively connected
by its drive shaft to a pinhole carrier 38 which is mounted for
rotation in a horizontal plane on a suitable bearing 40 relative to
the frame plates 28 and 30. Pinhole carrier 38 is shown having a
central core portion 42 and a plurality of webs 44 disposed in
vertical planes and extending radially from the core 42. Five such
webs 44 are shown in the example being described. Each of these
webs 44 carries a pinhole 46 for selective positioning in the
optical axis 22. Pinholes 46 differ in size depending on the
desired function. In this specific embodiment, the pinholes are
0.0032, 0.0064, 0.0096, 0.0120, and 0.0160 inches in diameter to
produce target spot sizes of 5, 10, 15, 20, and 25 micrometer
diameters respectively when used in conjunction with a 10X
objective lens. Motor 34 is operatively connected to a suitable
control circuit including microswitches which abut the pinhole
carrier to shut off the motor and stop its movement at the
positioning of a desired one of the pinholes in the optical axis
22. By rotating the carrier 38 in a plane parallel to rather than
perpendicular to optical axis 22, any inaccuracy in the stoppage of
motor 34 and carrier 38 is of much less consequence.
A partial reflector 48 is mounted to the frame 4 in the optical
axis 22 at a suitable angle relative thereto in order to reflect a
part of the energy incident thereon to an energy monitor. A right
angle prism 50 is mounted relative to the frame 4 in the optical
axis 22 so as to deflect the optical axis 22 by 90.degree.. Prism
50 is mounted for linear adjustability along the optical axis 22 in
both its directions, and also for limited rotational adjustability
about an axis parallel to that of the laser. By such plural modes
of adjustability, the optical axis 22 after deviation by the prism
50 can be placed as desired relative to the associated microscope
and optical system.
A relay tube 52 is mounted adjacent the prism 50 to define a path
along which the deflected optical axis 22 is directed. Relay tube
52 is mounted relative to a frame 54 which in turn is mounted by
suitable fasteners to frame 4. Relay tube 52 has mounted therein a
lens 56 which, with lens 24 forms a 2-power telescope. That is to
say, lenses 24 and 56 are the eyepiece and objective lenses
respectively of a 2-power telescope.
Referring now especially to FIG. 2, the same apparatus described in
FIG. 1 is shown in front elevation view. In addition to the above
described elements, FIG. 2 shows a binocular microscope, generally
indicated at 58 associated with the laser optical system. Eyepieces
60 are mounted on the microscope body 62 from which an objective 64
is depended. A microscope stage 66 is disposed beneath the
objective 64 and includes suitable controls 68, 70, and 72 for X,
Y, and Z adjustability of the stage relative to the microscope
body.
Between the eyepieces 60 and the objective 64 of this microscope,
and within the body 62, a beam splitter 74 is mounted and located
in the optical path 76 of the microscope. An illuminator 78 is
mounted on the body 62, communicates with the interior of the
microscope, and directs light onto the beam splitter 74 along an
illumination axis 80. Light from the illuminator 78 is refelcted
from the beam splitter 74 along the optical path 76 to illuminate
the object or specimen under observation in the incident-light mode
of operation of this instrument. Beam splitter 74, being partially
transmissive also permits the observer to view the specimen in the
eyepieces. Beam splitter 74 is mounted on a rotatable shaft 82
which is operatively connected to a rotary solenoid 84 which is in
turn operatively connected to the electrical control system of this
apparatus. An occluder 83 is also connected to shaft 82 of solenoid
84 for rotation therewith into and out of the optical path 76 of
the microscope. When positioned in the optical path, the occluder
is between the eyepiece and a mirror 88 where optical axis 22 joins
optical path 26. In the position shown, light from illuminator 78
is reflected onto the specimen for the purpose of alignment and
observation through the beam splitter 74 and the occluder is out of
the optical path 76. When the rotary solenoid is energized in
association with laser system, the beam splitter 74 is moved out
of, and the occluder 83 moved into, the optical path 76 of the
microscope.
Referring now to FIG. 3, the microscope of FIG. 2 is shown in side
elevation view. In this view, the body 62 of the microscope is
shown to include a reticle projection unit, generally indicated at
86, and the optical axis 22 of the laser system extending into the
microscope body 62. A dichroic mirror 88 is disposed above the beam
splitter 74 in the optical path 76 of the microscope. The axis 22
of the laser system and the projection axis 90 of the reticle
projection unit 86 are directed at opposite sides of the dichroic
mirror 88. By means of dichroic mirror 88, optical axis 22 is
deflected along the microscope optical path 76. By its dichroic
character, the mirror 88 reflects the 1.06 micron laser radiation
while transmitting in the visible range to the eyepieces for the
observer.
Reticle projection unit 86 includes a light source 92, a condenser
94, a suitable reticle plate 96, and a projection lens 98, for the
projection of the image of reticle 96 into the optical path 76 of
the microscope and, by means of dichroic mirror 88, to the
eyepieces 60. The reticle projection unit 86 is mounted to the body
of the microscope by means of a rocker plate 100 which is mounted
by a fastener 102 to permit limited rocking or wobbling motion
relative to the microscope body. Plate 100 and the associated
reticle projection unit 86 are swingably adjusted relative to
fastener 102 by means of a pair of adjusting screws 104, against
which plate 100 is spring-biased by springs 106. Fastener 102 is
located directly above the reticle projection unit 86 and axis 90;
adjusting screws 104 are located below and off-set from the
projection axis 90. Thus, only one of the screws 104 appears in
this figure. An energy monitor is represented at 108 and is
disposed in position relative to beam splitter 48 to receive and
detect reflected radiation therefrom. As presently preferred, the
beam splitter 48 is calibrated to reflect 8 percent of the radiant
energy incident thereon to the monitor 108. Monitor 108 consists of
a standard photo-diode with suitable electronics which are known
per se and need not be described further herein. This monitor 108
is for the purpose of determining the power level of the laser 2.
Energy monitor 108 is more fully disclosed in application Ser. No.
108,367, filed Jan. 21, 1971 by Albert D. Battista.
In operation, the microscope user first views through the eyepieces
60 to see a projected reticle pattern from the reticle projection
unit 86 superimposed on the image of the object or specimen. Having
been pre-adjusted by a test firing and subsequent adjustment of the
reticle, the observed reticle image now indicates the target
location on the object whereon the laser energy will be focused.
This adjustment is made with the specimen illuminated, either by
substage illumination transmitted through the object or by incident
illumination from illuminator 78 and beam splitter 74. When aligned
as desired, laser operation is commanded by electrical signal which
first actuates the solenoid 84 to swing the beam splitter 74 out of
the path of the laser and concurrently swings the occluder 83 into
the microscope optical path 76 above the dichroic mirror 88. The
happening of these two events then permits a trigger signal to
operate the laser, discharging its radiation along the optical axis
22 and from the dichroic mirror 88 onto the specimen or target. The
presence of occluder 83 above the mirror 88 is a second or backup
safety feature preventing any laser energy from getting to the
eyepiece.
The microscope described herein is capable of a substantial range
of adjustability for various operations. For example, the
attenuator disk 14 renders the density of the laser beam adjustable
in steps from 10 percent to 100 percent. The several pinholes on
carrier 38 make the target spot sizes adjustable in steps with the
largest being 5 times the diameter of the smallest. The instrument
furthermore has provision for transmitted or incident illumination,
and an interlocked shutter-occluder for operator safety.
The foregoing description of an embodiment of this invention is
given by way of illustration and not of limitation. The concept and
scope of the invention are limited only by the following claims and
equivalents thereof which may occur to others skilled in the
art.
* * * * *