Optical confocal device having a common light directing means

Details Optical confocal device having a common light directing means Optical confocal device having a common light directing means

1999-09-28

2002-06-04

Le, Que T. (Department: 2878)

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

C250S208100, C257S082000

Reexamination Certificate

active

06399936

ABSTRACT:

FIELD OF THE INVENTION
The invention disclosed herein relates generally to optical instruments and methods. Stated more particularly, disclosed and protected by the present patent is a scanning confocal device for scanning an object with an optical beam, detecting the light remitted from or reflected by the object, and generating an image of the object.
BACKGROUND OF THE INVENTION
Confocal imaging techniques include the illumination of objects with a “flying spot” and the detection of light that is reflected from or otherwise remitted by the currently illuminated point on the object located only in the image plane. This provides better spatial resolution, better contrast to the image, and less depth of field than conventional optical devices. The small depth of field allows for the creation of 3-D images of semi-transparent objects. Scanning imaging techniques are employed in confocal laser scanning microscopes (CLSM), tandem scanning microscopes (TSM), scanning laser ophthalmoscopes (SLO), and other applications.
A TSM is discussed in Petran et al., “Tandem-Scanning Reflected-Light Microscope,”
Journal of the Optical Society of America
1968 Vol. 58, No. 5, pp 661-664. Petran et al. acknowledged that reflected-light microscopy of semi-transparent material is usually unsatisfactory because of low contrast and light scattering. They describe the TSM, in which both the object plane and the image plane are scanned in tandem. In the Petran et al. system, the object is illuminated with light passing through holes in one sector or side of a rotating scanning disk, known as a Nipkow disk. The scanning disk is imaged by the objective at the object plane. Reflected-light images of these spots thereby produced are directed to the diametrically opposite side of the same disk. With this, light can pass from the source to the object plane, and, from the object plane to the image plane, only through optically congruent holes on diametrically opposite sides of the rotating disk.
Tandem scanning confocal arrangements, however, are “light-starved” by the limited brightness of the illumination spot. TSM systems, in addition, are hampered by stray light scattered from the moving pinhole array.
Current flying spot systems benefit from the advent of the laser. They use moving optical elements for deflecting a laser beam, so that an illumination spot is swept across the object to be scanned.
A recent version of a CLSM is described in U.S. Pat. No. 5,532,873 of Dixon. The scanning of the laser beam is provided by two mirrors, rotationally oscillating around axes that are perpendicular to each other.
A confocal scanning laser ophthalmoscope (CSLO) is disclosed in Webb et al, “Confocal Scanning Laser Ophthalmoscope,”
Applied Optics,
Vol. 26, No. 8, Apr. 15, 1987, pp 1492-1499. The apparatus uses multiple scanning elements, including a multifaceted rotating polygonal reflector scanner, to provide scanning of both incident and reflected light at television-rate frequencies. The CSLO scans an illumination spot over the fundus of an eye, and synchronously scans a detector over the image.
Other confocal devices, are discussed
in The Handbook of Biological Confocal Microscopy,
2nd edition. Pawley, ed., Plenum Press, 1995.
Conventional scanning devices of the type discussed require a multiplicity of mechanical components moving at high speed. They are typically bulky and require significant power to drive the scanning mechanism.
A confocal scanning device without moving parts is described in U.S. Pat. No. 5,028,802 of Webb et al,.
FIG. 1A
of the present application (which is
FIG. 1C
of the '802 patent) provides a summary of the Webb et al. invention and is prior art.
FIG. 1B
of the present application (
FIG. 3
of the '802 patent) shows the preferred embodiment of the '802 patent.
Referring to
FIG. 1C
of the '802 patent (
FIG. 1A
of the present application), the scanning arrangement employs N×M array
10
of microlasers in a scanning mode as the illumination source. As shown in
FIG. 1A
of the present application (
FIG. 1C
of Webb), the device includes a laser scan drive
16
for energizing the lasers of array
10
. The microlasers are energized sequentially, so that the array
10
is scanned in a conventional TV raster fashion. The array
10
is imaged on the object
18
to be illuminated thereby providing raster illumination of the object
18
. Light
19
emitted from the object, by reflection, scatter or transmission, is then detected by detector
20
and the detection signal, carried on line
21
, is displayed synchronously with the array scan, to provide a video image on a monitor or other image output device
22
driven by SYNCH signals provided by drive
16
on line
24
.
Referring to
FIG. 1B
of the present application (
FIG. 3
of Webb), a confocal scanning configuration uses a detector array having independently addressable photodiodes, that are optically congruent to microlasers. Lens L directs light from scanned source array
10
onto the object plane OB, and light reflected from the object is directed to detector
20
by beam splitter S. A lens L′ is used to direct light reflected from the object onto discrete photodiodes of a detector array
20
′. These photodiodes are read individually, in a pattern that is, and are synchronized with the scanning-illumination of the object. Thus, light scattered from non-illuminated portions of the object does not contribute to the output of the detection device, unless it impinges upon the selected portion of the detector. As a result, noise due to unwanted scattered light is significantly reduced.
U.S. Pat. No. 5,034,613 to Denk et al., which issued Jul. 23, 1991 for Two-Photon Laser Microscopy, discloses a laser scanning microscope in which fluorescent light is detected in a manner intended to avoid photo-bleaching.
U.S. Pat. No. 5,071,246 to Blaha et al., which issued Dec. 10, 1991 for Confocal Scanning Ophthalmoscope, discloses the use of light wave conductors.
U.S. Pat. No. 5,120,953 to Harris, which issued Jun. 9, 1992 for Scanning Confocal Microscope Including A Single Fiber For Transmitting Light To and Receiving Light From An Object, discloses the use of optical fibers for transmitting light and a light separator to divert the return light to a detector.
U.S. Pat. No. 5,296,703 to Tsien, which issued Mar. 22, 1994 for Scanning Confocal Microscope Using Fluorescence Detection, discloses the use of a beam of radiation and detection of the resulting fluorescence using beam splitters and rotatable scanning mirrors and a raster scan display.
U.S. Pat. No. 5,325,386 to Jewell et al., which issued Jun. 28, 1994 for Vertical-Cavity Surface Emitting Laser Array Display System, discloses the use of vertical cavity surface emitting lasers in an array to enhance a display.
U.S. Pat. No. 5,386,112 to Dixon, which issued Jan. 31, 1995 for Apparatus and Method for Transmitted-Light and Reflected-Light Imaging, discloses a microscope using a series of beam splitters and mirrors and light that is reflected is separated from light that is transmitted.
U.S. Pat. No. 5,430,509 to Kobayashi, which issued Jul. 4, 1995 for Scanning Laser Ophthalmoscope, discloses the use of beam splitters and mirrors and uses at least three scanning systems.
U.S. Pat. No. 5,450,501 to Smid issued Sep. 12, 1995 and is directed to an Apparatus for the Point-by-Point Scanning of an Object using frequency selective filtration to operate a system having transmission of light through the object being viewed.
U.S. Pat. No. 5,512,749 to Iddan et al., which issued Apr. 30, 1996 for Infrared Microscope, discloses the use of a cryogenic detection device and an IR array of detectors including a scanning mirror for scanning the object.
U.S. Pat. No. 5,524,479 to Harp et al. issued Jun. 11, 1996 and is directed to a Detecting System for Scanning Microscopes. The patent discloses the use of a cantilevered arm as a probe to examine the object to be viewed.
U.S. Pat. No. 5,563,710 to Webb, which issued Oct. 8, 1996 for Imaging System With Confocally S

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