Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND SYSTEM FOR MICROSCOPE ILLUMINATION
FIELD OF THE INVENTION
The Present invention relates to improvements to illuminator means for field,
internal computer and bench microscopes.
DEFINITIONS
For the purpose of this patent application the following definitions apply
throughout:
LED: LED is used to mean light emitting diode which may be either single
colour such
as red, green, blue, yellow, infrared or ultraviolet LEDS in any case type.
Laser diode: Any of the wide variety of semiconductor laser light emitting
diodes
including infrared, visible and ultraviolet laser diodes.
Diffuser: Any light diffusing material such as opal glass, sandblasted optical
material,
etched optical material, milky plastic or holographic diffuser material, but
most particularly the
family of white TeflonTM materials and a proprietary material called
SpectralonTM made by
LABSPHERE.
BACKGROUND OF THE INVENTION
Past patents proposed many ways of constructing microscopes and designing
illumination
systems for microscopes. One series of embodiments of the illumination system
described in this
patent is particularly suitable for field microscope use since in it employs a
white LED as the
light source. This offers a very high efficiency daylight like light source
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which is ideal for field use in that it is small, light, low power and can be
easily supplied by
battery or solar cell energy sources. It is different from other LED
microscope light sources
such as the one described in US patent 5,489,771 in that it uses a different
and far more
efficient approach to achieve flat field illumination and high efficiency in a
daylight like
source along with wavelength shaping, dimming control and battery power.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a novel method and system
for
producing LED based illuminators for compound microscopes which feature
modular
I O interchangeability, small size, low weight, high efficiency, low cost and
ease of construction.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the present invention will now be described, by way
of
example only, with respect to the attached Figures, wherein:
Figure 1 shows a first embodiment of an illuminator in accordance with the
present
invention,
Figure 2 shows similar type of illuminator to Fig. 1 except an optical
component is
used to isolate the external environment from the diffuser surface, and to
further shape the
illuminating cone leaving the illuminator;
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Figure 3 shows a similar type of illuminator to Fig. 1 except a plurality of
LEDs is
used to increase the light output level from the illuminator and a solid optic
is used to isolate
the external environment from the diffuser surface,
Figure 4 shows an illuminator where six LEDs are arranged in such a way as to
provide selectable colour content in the output from the illuminator,
Figure 5 shows a darkfield illuminator employing reflective optics and LEDs,
Figure 6 shows a simpler version of the darkfield illuminator,
Figure 7 shows a fibre optic or light guide version of the illuminator,
Figure 8 shows a novel field microscope employing one embodiment of the
illuminator.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is concerned with the design of high efficiency
illuminators
which employ LEDS, laser diodes and specifically white light LEDs with
internal phosphor
conversion methods. Several versions of such illuminators are described which
cover the
application areas of field microscopy and condenser replacement illuminators
for new or
retrofit use on conventional style upright and inverted microscopes.
PREFERRED EMBODIMENTS
In Figure 1 is shown a simple single LED microscope illuminator for a field
microscope in which the LED 200 supplies light to a diffuser 205 through a
limiting filter
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204. In this case the filter 204 limits the UV light component from the LED
200 from
leaving the illuminator so there is no UV content from the illuminator. The
filter in this case
is a Lee theatrical filter, part number 226, UV blocking filter and the LED is
a white light
LED which uses a 470nm blue LED with a phosphor coating to convert a
substantial part of
the emitted light from the UV and blue portion of the spectrum to a daylight
like broad
spectrum light. In other cases the filter can be, for instance, a UV
transmitting and visible
light absorbing filter used with a 470nm blue LED to act as a UV illuminator
for
fluorescence microscopy with transmitted light. The T-1 3/4 style LED shown is
chosen
since it produces a well defined 15 degree beam of light.
The light from the LED 200 strikes the diffuser 205 with a diameter to fill
the clear
aperture of the rear side ofthe diffuser. A portion of the light passes
through the diffuser and
a portion s reflected from the back surface. The portion reflected from the
back surface of
the diffuser strikes the rear reflective optic surface 201 and is reflected
back at the diffuser
to increase the efficiency of the illuminator due to back side losses from the
diffuser. The
light passing through the diffuser either directly exits the outlet of the
illuminator via port
203 which in this case is an open port with no window, or strikes the front
reflective optic
surface 202 and is reflected back to the diffuser front surface. The size of
the opening of the
illuminator port, the angle of the front reflective optic and the diameter of
the clear aperture
of the front surface of the diffuser all act to set the numerical aperture of
the illuminator. The
numerical aperture can be set to match the highest expected aperture of the
objectives used
with this illuminator. The illuminated field diameter is set by the diameter
of the port
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opening in the front surface of the illuminator. This port size may be
adjusted by means of an iris
diaphragm or by a series of sliding or rotating fixed apertures. The rear
reflective optic 202 is
machined into the surface of the LED mounting component 210 and may be as
machined
aluminium or may incorporate broadband or narrow band reflective coatings on
its surface. The
front reflective optic is machined into the internal surface of illuminator
body 512 and may be as
machined or may incorporate broadband or narrow band reflective coatings on
its surface.
Where it is desired to protect the diffuser from dirt or fluids a window can
be incorporated to seal
the port opening 203 from the external environment. Such a window limits the
effective
numerical aperture due to total internal reflection. Illuminators of this type
without windows
have been tested and have achieved numerical apertures greater than 0.80 NA.
The LED is powered by external power via connector 508 or internal battery
power (not shown) which is controlled by intensity adjustment control 507
which sets the current
and voltage supplied to the LED by control circuit located on printed circuit
board 509.
The LED 200 can be any type of LED or laser diode. The diffuser can be
TeflonTM, spectralonTM or any similar diffusing material which diffuses
substantially all of the
angles and wavelength of light impinging on it, including glass, ground glass,
opal glass or
etched glass. The diffuser can be incorporated internally or externally
wavelength converting
materials which can shift the wavelength of the I,ED or laser diode wither to
shorter or longer
wavelengths as desired. The wavelength converting materials include phosphors,
frequency
conversion crystals and other similar materials.
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In other patents such as US Patent 5,489,771 another type of LED illuminator
is
described except it uses chip type LEDS which are direct coupled to a diffuser
block. The
designs described herein use discrete LEDS and reflective optics with a
diffuser to
accomplish a higher efficiency and a controlled numerical aperture of
illumination. They
also employ white light LEDs and utilize electronic control of the LED
intensity and low
power regulation circuits.
In Figure 2 a piano convex Tense 260 is used to form an isolation between the
external
environment and the diffuser surface. The Tense 260 is cemented into the
outlet opening of
the illuminator to form a fluid and gas tight seal. The optical
characteristics of the Tense limit
the angles of light which can leave the diffuser/reflector area since many
trajectories of light
experience total internal reflection at the air glass interface of the Tense.
This limits the
maximum NA from the illuminator and produces a more defined beam with less
stray light
than the version shown in Fig. 1.
In Figure 3 two LEDs 270 and 280 are shown with their beams directed to
diffuser
203. If two identical LEDs are employed then the brightness of the illuminator
can be
increased while if two different wavelength LEDs are employed then the
illuminator can
supply tailored spectral output to match a particular application need.
A different type of outlet window design is also shown in this figure. The
output port
is occupied by an optical component 281 which incorporates the front
reflective optical
components into its outer surface 288 as a reflective mirrored surface with
either broadband
or narrow spectral reflectance characteristics. This optical component 281 has
a plane front
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surface which forms the coupling surface of the illuminator so that the
illuminator can be oil
coupled to a slide to allow high numerical apertures to be achieved. The rear
side of the
optical component 281 also has a plane surface to that it can be cemented, oil
or fluid
coupled or otherwise optical coupled or contacted to the diffuser 203 front
surface. In this
type of illuminator there may be more than one control means 283 to
individually control the
separate LEDs. Alternatively the LEDs can be controlled via signals from the
connector 282
in order to coordinate the illuminating system with the observing system of
the microscope.
Figure 4 shows a similar type of illuminator in which six LEDs 401 through 406
(402
through 405 not shown but arranged in a circular array about the vertical
centre axis of the
illuminator) are used to illuminate the diffuser 203. Here the rear reflective
optic has its
primary mirror surface at 408 and secondary surfaces at 410 and 411. In such
an illuminator
the control the individual LEDs would typically by external control signals
via connector 409
but it could also be by six internal controls 412 arranged around the base of
the illuminator.
In Figure 5 is shown a darkfield condenser replacement using an LED
illumination
system. The particular type of darkfield condenser shown here is a cardioid
design but this
type of illuminator can be used with virtually any type of darkfield condenser
design
including those with patch stops where the cone internal reflector can form
the patch stop.
The LED 500 send a beam of light upwards toward the primary mirror 501, which
is a
mirrored hollow in the circular glass part 502, which then directs the light
towards the
secondary mirror 503. The secondary mirror 503 is a mirrored outside surface
of circular
glass part 504. The top surface of glass part 504 forms the outlet window for
the light from
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the condenser and can be flat or a truncated inverted cone. This surface is
flat on the top
surface to allow oil coupling to the slide carrying the object to be viewed.
The two glass
parts 502 and 504 are cemented or bonded together so that light can pass the
boundary
between the two components at low angles of incidence without total internal
reflection.
Since a portion of the light from the LED normally strikes the middle of the
primary mirror
where it would reflect back to the LED instead of carrying on to the secondary
mirror, a set
of reflective optics 505 and 513 are used to configure the light path so that
the light is
preferentially sent to the portions of the primary mirror where it then passes
to the secondary
mirror. Since the light strikes the conical reflector surfaces at grazing
angles it is important
to note that the light is still substantially parallel, or within a small
angular spread when it
strikes the primary mirror. The conical reflector 511 can be mounted on a
spider at the top
of reflector 505 or alternately it can be adhered to the underside of glass
part 502. The
reflector 513 sets the outside diameter of the beam of light from the LED and
is formed on
the internal surface of part 505 so it also serves as the mounting means for
the LED 500
which is adhered in the bore of the reflector 505. The reflector 511 sets the
diameter of the
hollow central region of the beam of light from the LED. In some cases the
reflectors 513
and 511 may be used alone with suitable angles to form a dry type darkfield
illuminator (not
shown) with numerical apertures to suit the application and objectives chosen.
The reflectors
513 and 511 increase the efficiency with which light from the LED is conveyed
to the outlet
window of glass part 504. In the version of such an illuminator as shown the
LED 500 is
supplied with controlled power from the electronic dimmer circuit which is
contained on
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printed circuit board 509. Power to this printed circuit board is supplied
through power
connector 508. The intensity of the light from the illuminator is controlled
by potentiometer
507. The overall illuminator is contained in housing 512 which is
approximately the same
size as a traditional darkfield condenser. The housing 513 has a mounting
flange or dovetail
510 made to mate with the microscope type it is intended for. Inside the
housing 512 is a
means for supporting the reflector 505 which is here shown as part 506.
Such darkfield condensers can be configured with single LEDs as shown or with
multiple LEDs of same colour inside the reflector optics 513 and 511 to
increase the
brightness, or with multiple colour LEDs either in the form of discrete LEDs,
LEDs
containing multiple die or discrete LED chips, to control the wavelength
content of the
emerging light from the condenser.
The general idea of using an LED in a darkfield condenser has been previously
proposed and successfully carried out by J. Dutton as described in Quekett
Bulletin No. 33
December 1998 page 29. It is the intent of this patent to show improvements to
the scheme
he proposed to increase the efficiency, intensity, and control of intensity
and wavelength of
such an LED powered darkfield condenser.
Figure 6 shows a simplified version of Figure 5 with only the external rear
reflective
optic 513 on the internal surface of 505. This application can be particularly
suited to laser
diode applications where power levels are not difficult to achieve and
efficiency is not such
a consideration. It is also suitable for applications such as darkfield auto-
fluorescence where
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a powerful beam of blue or UV light is desired to initiate spontaneous
fluorescence of a
sample object.
Figure 7 shows a typical LED based illuminator where the diffuser is moved to
the
outer surface of the illuminator at 701. The diffuser may also be omitted and
a plane
polished first surface may be employed. The optical component 703 consists of
a light guide
formed by a suitable optical material which can be glass, plastic, GRIN
material or fibre
optic bundles. The material is contoured to be cemented to the LED at
interface 705. The
numerical aperture of the illuminator is set by the angles of the internal
reflective surfaces
704 which may be omitted in applications where numerical aperture is not
important. The
LED is held in place by mounting block 702 which keeps the LED in contact
optical part 703
if they are not cemented together.
Figure 8 shows a typical application of one style of these illuminators as a
modular
microscope stage, illuminator, and control system all in one integrated
package.
The module includes a stage module 100 which includes an LED 101 which may be
a coloured LED or which may be a white light emitting LED which employs a
system of
several LED chips to achieve white light either internally to the LED
encapsulation or as a
set of discrete chips or die, or which may be a white light emitting LED where
the white light
is achieved by a phosphor coating on the LED die or on or in the LED plastic
encapsulation
so that the original substantial monochromatic light from the LED die is
converted to broad
spectral content white light. The LED emits light which strikes the diffuser
106 so that part
of the light is transmitted by the diffuser 106 in the forward direction to
the outlet of the
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illuminator 127 and part of the light is reflected by the diffuser and strikes
the reflector optic
surface of part 102 which serves a dual function to hold the LED in place and
to reflect light
back to the diffuser surface. Of the light transmitted by the diffuser a
portion directly leaves
the outlet of the illuminator 127 while light which is not within the
acceptance angle of the
output reflector 126 is reflected back to the front diffuser surface 106. This
pair of mirrors
acting on the front and back sides of the diffuser greatly increases the
efficiency of the
illuminator.
The cone of light from the diffuser can be tailored to any desired numerical
aperture
to match the maximum numerical aperture of the objective lenses used with the
field
microscope by the selection of the angles of the reflector surfaces of
reflector 126 and by the
diameter of the diffuser 106 and the illuminator outlet opening 127. The
surface of the front
reflector 126 may be a plane surface or a curved surface. The distance from
the diffuser 106
to the LED 101 is determined by the cone angle of the light emitted by the LED
and the
diameter of the diffuser. The edge of illuminated circle of the cone angle of
the LED should
match the clear aperture of the diameter of the diffuser. The angle of the
rear reflector optic
102 should be chosen to maximize the return of reflected light to the diffuser
and may be a
plane surface or a curved surface.
A filter material 128 which may be an interference filter or a film or gel
type filter
may be used to remove unwanted light from the illuminator output. This is
particularly true
where the LED is a phosphor based white light emitting LED which uses a blue
LED as the
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exciting source for the phosphor and where the blue LED emits UV light as part
of its overall
spectral output. In this case a material such as LEE Filter number 226 UV
blocking gel is
selected to remove the UV light from the LED output. The LED is powered from a
printed
circuit board 103 which contains the regulating and dimming electronics to
control the LED
brightness 105 and a control potentiometer 104 which is used to manually
adjust the
brightness of the LED.
The light from the illuminator passes through the glass slide 107 to
illuminate the
object 108 with a cone of flat light of spectral content determined by the
choice of LED 101.
TYPICAL ILLUSTRATIVE APPLICATIONS AREAS
The illuminators described herein are particularly useful in field and remote
laboratory
applications. Third world laboratories carrying out pathological bacterial or
scientific
research will benefit from the availability of such condensers which can be
used with existing
microscopes as a retrofit item.
Current scientific researchers in traditional major research labs can also
benefit from
the extremely uniform field of illumination made available by these
condensers. Another
area of application is in microscopy where wavelengths outside the visible
spectral range can
be detrimental to the sample object. The white LEDs employed herein do not
emit light
outside the normal spectral range and any minimal UV or IR content ifpresent
can be readily
filtered with commercially available filtering components. The low photon
levels and
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virtually zero UV and IR content suggests these types of condensers for long
term studies of
cells especially in fertilization work for in vitro fertilization.
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