U.S. patent application number 13/972489 was filed with the patent office on 2014-11-13 for medical headlamp optics.
This patent application is currently assigned to River Point, LLC. The applicant listed for this patent is River Point, LLC. Invention is credited to John Thomas Ferguson.
Application Number | 20140334132 13/972489 |
Document ID | / |
Family ID | 51864634 |
Filed Date | 2014-11-13 |
United States Patent
Application |
20140334132 |
Kind Code |
A1 |
Ferguson; John Thomas |
November 13, 2014 |
Medical Headlamp Optics
Abstract
A lamp having a front surface from which a beam of light is
emitted and that includes a housing. An optical assembly is
supported and partially enclosed by the housing, and includes an
LED assembly, a prime lens and an exit lens, with light emitted
from the LED assembly passing through the aspheric prime lens and
exiting through the exit lens. Also, the exit lens defines a front
surface and a rear surface and the rear surface has a convex shape
different from the shape of the front surface.
Inventors: |
Ferguson; John Thomas;
(Portland, OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
River Point, LLC |
Portland |
OR |
US |
|
|
Assignee: |
River Point, LLC
Portland
OR
|
Family ID: |
51864634 |
Appl. No.: |
13/972489 |
Filed: |
August 21, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61822493 |
May 13, 2013 |
|
|
|
Current U.S.
Class: |
362/105 ;
362/311.02 |
Current CPC
Class: |
F21V 21/084 20130101;
B29C 70/72 20130101; A61B 1/0692 20130101; A61B 90/35 20160201;
A61B 2090/502 20160201; A61B 2090/309 20160201; F21V 5/04 20130101;
F21W 2131/20 20130101; A61B 90/30 20160201 |
Class at
Publication: |
362/105 ;
362/311.02 |
International
Class: |
A61B 19/00 20060101
A61B019/00; F21V 21/084 20060101 F21V021/084 |
Claims
1. A lamp having a front surface from which a beam of light is
emitted, comprising: (a) a housing (b) an optical assembly
supported and partially enclosed by said housing, including an LED
assembly, a prime lens and an exit lens, with light emitted from
the LED assembly passing through the aspheric prime lens and
exiting through the exit lens; and (c) wherein said exit lens
defines a front surface and a rear surface and said rear surface
has a convex shape different from the shape of said front
surface.
2. The lamp of claim 1 wherein said rear surface defines a curve
across its diameter having the characteristic that for every 0.5 mm
chord connecting two points along the curve the perpendicular
distance ("sagitta" or "sag") from the chord to the curve, at the
chord midpoint, is at least 0.025 mm.
3. The lamp of claim 1 wherein the rear surface defines a curve,
across its diameter, fitting the equation:
Z=(CR.sup.2)/(1+SQRT(1-(1+K)C.sup.2R.sup.2)), where Z is forward
displacement from the peak of the rear surface in mm, R is distance
from the center in mm, C is a constant of between 0.05 and 0.06
mm.sup.-1 and K is a unitless constant of between 14 and 16.
4. A medical headlamp assembly, comprising: (a) a headstrap
assembly; (b) batteries mounted on said headstrap assembly; (c) a
lamp, operatively mounted on said headstrap assembly and powered by
said batteries and having: (i) a high-efficiency light source that
emits light; and (ii) an optical assembly structured and positioned
so as to accept and emit most of said light from said
high-efficiency light source; and (d) wherein said lamp produces a
beam of light from said optical assembly that at a distance of 46
cm, on a white surface perpendicular to said beam, creates a spot
of light that is greater than 40 mm in diameter and that is all
illuminated to an intensity of greater than 50,000 lux.
5. The medical headlamp assembly of claim 4, wherein said spot of
light has a color rendering index of greater than 60.
6. The medical headlamp assembly of claim 4, wherein said spot of
light is all illuminated to an intensity of greater than 58,000
lux.
7. The medical headlamp assembly of claim 4, wherein said spot of
light has a maximum intensity of greater than 70,000 lux.
8. The medical headlamp assembly of claim 4, having a mass of less
than 300 grams.
9. The medical headlamp assembly of claim 4, wherein said optical
assembly includes a prime lens adjacent to said light source and an
exit lens.
10. The medical headlamp assembly of claim 9, wherein said prim
lens defines a concavity in its rear surface and said light source
protrudes into said concavity, thereby permitting said optical
assembly to capture more light from said light source.
11. A medical headlamp assembly, comprising: (a) a headstrap
assembly; (b) a source of electric power; (c) a lamp, operatively
mounted on said headstrap assembly and powered by said source of
electric power and having: (i) a high-efficiency light source that
emits light; and (ii) an optical assembly structured and positioned
so as to accept and emit most of said light from said
high-efficiency light source; and (d) wherein at an ambient
temperature of 30 degrees Celsius, said lamp can operate at maximum
power without forced fluid cooling and without causing damage to
itself, and produces a beam of light that at a distance of 46 cm,
on a white surface perpendicular to said beam, creates a spot of
light that is greater than 40 mm in diameter and that is all
illuminated to a brightness of greater than 50,000 lux.
12. The medical headlamp assembly of claim 11, wherein said beam
has a light intensity of more than 90 lumens per watt of power
delivered to said lamp.
13. The medical headlamp assembly of claim 11, wherein said beam
has a light intensity of more than 100 lumens per watt of power
delivered to said lamp.
14. The medical headlamp assembly of claim 11, wherein said beam
has a light intensity of more than 110 lumens per watt of power
delivered to said lamp.
15. The medical headlamp assembly of claim 11, wherein said source
of electric power is a battery assembly supported by said headstrap
assembly.
16. The medical headlamp assembly of claim 11, having a mass of
less than 300 grams.
17. The medical headlamp assembly of claim 11, wherein said light
assembly is an LED assembly.
18. The medical headlamp assembly of claim 17, wherein said LED
assembly includes an LED supported by a substrate and covered by a
silicone dome lens.
19. The medical headlamp assembly of claim 18, wherein an annular
light block is seated on said silicone dome lens.
20. The medical headlamp assembly of claim 11, wherein said spot of
light has a color rendering index of greater than 60.
21. The medical headlamp assembly of claim 11, wherein said spot of
light has a color rendering index of about 65.
Description
RELATED APPLICATIONS
[0001] This application claims priority from provisional
application Ser. No. 61/822,493, filed May 13, 2013, which is
incorporated by reference as if fully set forth herein.
BACKGROUND
[0002] A medical headlamp assembly is a critical part of the
surgeon's suite of tools, as it is of great importance that a
surgeon can clearly see in the operating theater. The ideal
headlamp would be easily portable, light and comfortable to wear
for at least four hours. Further, it would have battery power,
mounted on the headstrap, sufficient to last four hours off one
charge, thereby eliminating the necessity of waist mounted battery
pack and cables connecting this pack to the lamp, which are
uncomfortable and complicate antiseptic protocol. Further the ideal
headlamp assembly would create a bright beam of light that was
homogenous and uniform in brightness and color, from edge-to-edge,
directly along the surgeon's line of sight, without obscuring his
or her line of sight. Also, it would be entirely silent, easily
adjustable in position and would not be susceptible to infection by
mold or any other sort of organism.
[0003] Unfortunately, these criteria are not only difficult to
meet, but are also frequently at odds with each other. For example,
although it is better to have a bright light, this creates more
heat, which must be safely expressed from the lamp. It is helpful
in the elimination of heat to make the lamp bigger, but doing so is
likely to cause it to obscure the surgeon's line of sight and add
unbearable weight. Another option for expressing heat would be to
provide a fan, but this creates a sound which may be difficult for
the surgeon to tolerate. To permit longer battery life it would be
helpful to have higher capacity batteries, but doing so makes the
assembly heavier and more difficult for the surgeon to tolerate for
a long period of time. The batteries could be placed in a waist
pack, but doing so requires an electrical line extending from an
aseptic area, about the waist underneath the scrubs (anything under
the neck is a "sterile" area), to a nonsterile area, on the
surgeon's head. This arrangement complicates aseptic protocol.
[0004] There is a currently available headlamp assembly that mounts
batteries on the headband and that has batteries that can be
swapped out, one at a time, for extended surgical periods. The
light produced by this headlamp is on the order of 166 lumens in
intensity. For many types of surgery, for example where a deep
cavity that has been opened up inside a patient requires
illumination, a higher intensity lamp is desirable.
SUMMARY
[0005] The following embodiments and aspects thereof are described
and illustrated in conjunction with systems, tools and methods
which are meant to be exemplary and illustrative, not limiting in
scope. In various embodiments, one or more of the above-described
problems have been reduced or eliminated, while other embodiments
are directed to other improvements.
[0006] In a first separate aspect, the present invention takes the
form of a lamp having a front surface from which a beam of light is
emitted and that includes a housing. An optical assembly is
supported and partially enclosed by the housing, and includes an
LED assembly, a prime lens and an exit lens, with light emitted
from the LED assembly passing through the aspheric prime lens and
exiting through the exit lens. Also, the exit lens defines a front
surface and a rear surface and the rear surface has a convex shape
different from the shape of the front surface.
[0007] In a second separate aspect, the present invention takes the
form of a medical headlamp assembly that includes a headstrap
assembly and batteries mounted on the headstrap assembly. Further,
a lamp is operatively mounted on the headstrap assembly and powered
by the batteries and has a high-efficiency light source that emits
light and an optical assembly structured and positioned so as to
accept and emit most of the light from the high-efficiency light
source. Finally, the lamp produces a beam of light from the optical
assembly that at a distance of 46 cm, on a white surface
perpendicular to the beam, creates a spot of light that is greater
than 40 mm in diameter and that is all illuminated to an intensity
of greater than 50,000 lux.
[0008] In a third separate aspect, the present invention takes the
form of a medical headlamp assembly, comprising a headstrap
assembly, a source of electric power and a lamp, operatively
mounted on the headstrap assembly and powered by the source of
electric power. The lamp has a high-efficiency light source that
emits light and an optical assembly structured and positioned so as
to accept and emit most of the light from the high-efficiency light
source; and wherein at an ambient temperature of 30 degrees
Celsius, the lamp can operate at maximum power without forced fluid
cooling it and without causing damage to itself, and produces a
beam of light that at a distance of 46 cm, on a white surface
perpendicular to the beam, creates a spot of light that is greater
than 40 mm in diameter and that is all illuminated to a brightness
of greater than 50,000 lux.
[0009] In addition to the exemplary aspects and embodiments
described above, further aspects and embodiments will become
apparent by reference to the drawings and by study of the following
detailed descriptions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Exemplary embodiments are illustrated in referenced
drawings. It is intended that the embodiments and figures disclosed
herein are to be considered illustrative rather than
restrictive.
[0011] FIG. 1 shows a side view of a medical headlamp assembly,
according to the present invention.
[0012] FIG. 2 shows an isometric view of the medical headlamp
assembly of FIG. 1.
[0013] FIG. 3 is a cross-sectional view of a lamp for use in a
medical headlamp assembly such as that of FIG. 1.
[0014] FIG. 4 is an exploded view of the lamp of FIG. 3.
[0015] FIG. 5 is a diagram of the lens system of a prior art
headlamp, showing the outer light rays when the system is in
operation.
[0016] FIG. 6 is a diagram of the lamp of FIG. 3, showing the outer
light rays when the system is in operation.
[0017] FIG. 7 is a graph of light intensity values from a spot
formed on a white background formed 45.7 cm (18 inches) in front of
the front surface of the headlamp, according to a preferred
embodiment, using 1 Amp of current and a 3.4 Volt, from battery,
voltage drop. The intensity values are taken along a diameter of
the light spot.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Definitions
[0018] For the purposes of this application, a "high efficiency
light source" is an electrically powered light source having a
light emitting surface area of less than 50 mm.sup.2 that produces
light at a rate of greater than 50 lumens per watt of input power
and at a rate greater than 30 lumens per square millimeter of light
emitting area. This term does not include packaging or a lens. If
these items are included the phrase used is "high efficiency light
source assembly".
[0019] A light emitting diode (LED), as used in the application,
refers to a solid state electrical device and does not include any
lens or packaging. This element is sometimes referred to as a
"die," by others. A light emitting diode assembly, includes
packaging and a lens.
[0020] The term "most" as used in this application, means more than
50%.
[0021] The term "light" as used in this application refers to
visible light.
[0022] The "front" of the medical lamp is the side from which light
is emitted. The "longitudinal dimension" extends from front to
back.
[0023] Referring to FIGS. 1 and 2, in a preferred embodiment of the
present invention is a medical headlamp assembly 10, having a
headlamp optical assembly (bezel) 12, an adjustable headlamp bezel
support assembly 14, a headstrap assembly 16, supporting a pair of
batteries 18, each in contact to a circuit board (not shown) in a
circuit board repository 20. A head-top strap 22 and brightness
control knob 24 also are supported by headstrap assembly 16.
Assembly 10 includes a headlamp bezel 12 that has a slightly larger
diameter than generally found in the prior art. This permits a
brighter light beam since it can support more power intake (drive
current), as the greater surface area permits more heat to be
radiated away. But it also necessitates a better degree of
positioning control and ease of positioning control.
[0024] It is highly desirable, but very difficult, to produce a
large, clear, sharp round light spot for a surgeon, using LED
technology that is powered by head-mounted batteries. To do this it
would be beneficial to use an LED assembly that produces a cone of
light having a 3 dB beam width of greater than 90.degree., but
there is no such LED assembly available that produces a beam that
has a sharp edge while still being efficient enough to provide the
brightness necessary to do a deep cavity surgery. The Oslon
Square.TM. LED assembly provides a beam width of 120.degree., and
although bright enough was considered unusable in this application
due to the slow tapering off of the beam edges, which if not
corrected would create a spot of light having a fuzzy boundary,
when an aspheric lens system is used, as is typical. This detracts
from the tight focus on a specific area that the medical light is
intended to provide and can cause distracting reflections of the
metal instruments used in surgery.
[0025] Referring to FIGS. 3, 4 and 6, in a preferred embodiment, of
an optical assembly 12, an LED assembly 212, including a domed
silicone lens 214, and producing a light beam having a 3 dB
beamwidth of 120.degree., has a 25.mu. (1 mil) thick annular light
block 220 fitted around LED assembly 212, with the domed silicone
lens 214 extending through the annulus of the light block 220. The
beam exiting light block 220 has a beamwidth of 120.degree. but
with a much sharper edge then the beam from LED assembly 212. This
contrasts with prior art systems in which an adjustable iris light
block is placed entirely in front of the light source, resulting in
a greater portion of the light being blocked and lost to beneficial
use. Because this permits the use of the otherwise unusable
120.degree. beam width assembly, this assembly permits a larger
spot of light for the surgeon using the optical assembly 12. The
placement of the light block 220 together with its 25.mu.
thickness, creates a sharp boundary about the light, and ultimately
creating a sharp spot of light, at the typical 80-100 mm (16-18 in)
working distance. Lens 214 is fit into a concavity 216 formed in
the back of an aspheric prime optic lens 218. Table 1 shows the LED
assembly 212 characteristics for four differing embodiments. In an
alternative preferred embodiment an LED assembly is used that is
similar to the Oslon Square LED assembly, but includes more than
one LED die, and in another preferred embodiment more than one LED
assembly is used.
[0026] In front of prime optic lens 218, an exit lens 222 has a
convex rear surface 224, thereby better directing the captured
light back to create a beam of constant illumination over area. The
equation for the surface is:
Z=(CR.sup.2)/(1+SQRT(1-(1+K)C.sup.2R.sup.2)); [0027] Where Z is the
distance of the surface away from the apex of the rear surface 224
of the exit lens 222, in the longitudinal dimension, toward plane
226 (see FIG. 6), where: [0028] R=radial distance from center in
mm; and where C=0.05479 mm.sup.-1, and K=-14.954 (unitless).
[0029] More generally, the curve described by the above equation
has the characteristic that for every 0.5 mm chord connecting two
points along the curve the perpendicular distance ("sagitta" or
"sag") from the chord to the curve, at the chord midpoint, is at
least 0.025 mm.
[0030] As noted in the background, prior art systems included an
adjustable iris aperture in front of the light source to permit
adjustment of light spot size and create a sharply defined edge and
homogeneous brightness and color from edge to edge. Although this
permitted flexibility with respect to spot size, the movable
elements of the iris required the iris aperture to be positioned
further in front, the light source resulting in more light being
blocked. Also, the need to have moveable leaf elements that fit
together could impart a noncircular shape to the beam and the spot
of light produced by the beam. Even when an iris was not used, as
illustrated by FIG. 5, prior art systems, such as optical
arrangement 300, would lose light by placement of the prime lens
310 far ahead of the light source 312. By contrast, a preferred
embodiment has a set aperture size created by the 25 micron--100
micron (1 to 4 mils) thick annular light block 220. This novel
arrangement creates a far sharper light-spot boundary, due to the
extremely thin circular aperture wall, resulting in virtually no
light reflecting from the inner surface of annulus. This light
block 220 is positioned around dome 214 of LED assembly 212,
thereby blocking a smaller portion of the light produced by
assembly 212.
[0031] The LED assembly 212 is driven by a 750 milliamp or greater
current. A one (1) amp current at a typical battery voltage of 3.45
Volts results in a voltage drop through the LED assembly of about
3.15 Volts, due to some voltage drop through a rheostat, which is
used to adjust light intensity, in the headstrap 16. This creates
about 3.15 Watts of power that must be dissipated as heat from the
LED assembly 212. The LED assembly 212 is driven by traces 242 that
extend through a sheet of flex circuit 240 that is mounted behind
prime lens holder 250 (FIGS. 3 and 4). Annular light block 220 fits
into a round recess 260 in the center of holder 250. A layer of the
flex circuit 240 is made of copper (except for channels where the
copper has been removed to separate the traces 242 from the rest of
the copper covering), which efficiently conducts heat away from
assembly 212. Light is reflected from this conductive layer, which
is close to the front, and at most covered with a transparent
coating. This light is re-reflected back by the annular light
block, preventing this yellowish light from entering the beam of
light produced by assembly 10.
[0032] As illustrated in FIGS. 3 and 4, the exit lens 222 is held
in a lens holder 270 that has a slot-follower 272 which is fitted
into a curved slot 282 in an aft barrel 280. An outer ring 290
includes a straight internal longitudinal slot 292, and is mounted
about aft barrel 280, so that when outer ring 290 is rotated, lens
holder 270 is also rotated as slot-follower 272 is forced to stay
in straight slot 292. This rotation forces slot-follower 272 to
rotate within curved slot 282, which in turn causes slot-follower
272 and lens holder 270 to be moved either forward or backward in
aft barrel 280. This either focuses or defocuses the light beam,
creating a larger or smaller spot of light. The aft barrel 280 is
made of aluminum and has a high thermal conductivity, whereas lens
holder 270 and outer tube 290 are made of hard, black acrylonitrile
butadiene styrene (ABS) polymer. Aft barrel 280 has a length 300 of
49.36 mm, and a height 320 of 38.61 mm. The front of aft barrel 280
has an outer diameter 330 of 27.26 mm. The other parts shown in
FIGS. 3 and 4 are shown at the same scale as the aft barrel. The
optical assembly 12 has a mass of 43 grams. The entire assembly 10,
including batteries 18, has a mass of 340 grams.
TABLE-US-00001 TABLE 1 LED Assemblies Used in Various Embodiments
Further Manufacturer Designation LED Beam Designation Class (Color)
Angle LED Assembly of Emb. 1 Oslon Square PC 120 LED Assembly of
Emb. 2 Oslon Square EC 120 LED Assembly of Emb. 3 Oslon Square CC
120 LED Assembly of Emb. 4 Oslon Square EQW 120 Current Applied 750
mA 1 A 1.2 A 1.5 A Lumen Output LED Assembly of Emb. 1 252-346
312-429 372-511 408-561 LED Assembly of Emb. 2 220-294 273-364
325-434 357-476 LED Assembly of Emb. 3 189-271 234-336 279-401
306-440 LED Assembly of Emb. 4 294-409 364-507 434-604 476-663
Voltage LED Assembly of Emb. 1 3.08 3.15 3.2 3.28 LED Assembly of
Emb. 2 3.08 3.15 3.2 3.28 LED Assembly of Emb. 3 3.08 3.15 3.2 3.28
LED Assembly of Emb. 4 3.08 3.15 3.2 3.28 Wattage LED Assembly of
Emb. 1 2.31 3.15 3.84 4.92 LED Assembly of Emb. 2 2.31 3.15 3.84
4.92 LED Assembly of Emb. 3 2.31 3.15 3.84 4.92 LED Assembly of
Emb. 4 2.31 3.15 3.84 4.92 Lm/Watt @ max lm LED Assembly of Emb. 1
150 136 133 114 LED Assembly of Emb. 2 127 116 113 97 LED Assembly
of Emb. 3 117 107 104 89 LED Assembly of Emb. 4 177 161 157 135
[0033] The effect of the above detailed design is a medical
headlamp assembly 10 with batteries 18 mounted on the headstrap
assembly 16, and without a fan to provide forced air cooling, but
which produces a brighter beam than previously available headlamp
assemblies of this sort. The beam produced, in one preferred
embodiment, has a light volume of 413 lumens with a color rendering
index of at least 65. The beam is emitted relatively evenly from
the 23 mm diameter front surfaces of the exit lens 222, and spreads
out by 4.19 degrees in all directions as the beam advances.
Referring to FIG. 7, a one (1) Amp lamp, as described above, where
the voltage drop from the batteries is 3.4 Volts, produces a spot
of light at 45.7 cm (18 inches) as shown. With a bright central
area, about 52 mm wide at all above 50,000 lux at a color rendering
index (CRI) of greater than 65. This is surrounded by a ring of
about 10 mm width, where the light intensity declines from 50,000
lux to 25,000 lux. At the edges of the light beam, the brightness
drops off by 20 dB in 0.5.degree.. The lamp is operable in an
ambient temperature of up to 30.degree. Celsius, with no fan to
cool the lamp.
[0034] This brightness is achieved by two improvements, with
respect to prior art assemblies. First, the electric power applied
to the LED assembly 212 is greater than in the prior art.
[0035] Second, the proportion of light produced by the LED that is
emitted in the beam is greater. The greater electric power of
2.5875 Watts creates a problem of successfully expressing the heat
produced. It is highly advantageous to do this without the use of a
fan, which would drive up electric power usage and create an
unwanted noise. Accordingly, no fan is used in the preferred
embodiment. The need to express the heat produced, is addressed by
a longer aft barrel 280 which is made of aluminum and acts as a
heat radiator, without blocking the surgeon's view. Also, the
copper surface of flex circuit 240 conducts heat away from the LED
assembly 212 and toward the bezel housing. A greater proportion of
light produced by the LED is emitted in the light beam because: 1)
the distance between the LED assembly 212 and the prime lens is
shortened to virtually nothing, as the LED assembly 212 protrudes
into a concavity 216 in the prime lens 218; 2) the adjustable iris,
present in many prior art systems has been eliminated; 3) the
annular light block 220 sits on the lens of the LED assembly 212,
so that it is so far back that it blocks only a small proportion of
the light. In one preferred embodiment 70% of the light produced by
LED assembly 212 is emitted from the exit lens 222 as a light beam.
Alternative preferred embodiments emit anywhere from 50% to 70% of
the light produced by the led assembly 212 out of exit lens 222.
This compares favorably with prior art systems where less than 45%
of the light produced by the light source is emitted in the beam.
In a preferred embodiment the light beam produced from exit lens
222 has a volume of 114 to 161 lumens for every watt of power
applied to LED assembly 212. In one alternative preferred
embodiment this figure ranges from 90 lumens of output light per
watt to 161 lumens of output light per watt.
[0036] This device greatly eases the task of the surgeon, who may
now have an adequately bright and wide spot for deep cavity
surgery, without the need for the distracting noise and cumbersome
extra weight of a fan and without the need of any power cable
traversing from a sterile to a nonsterile zone.
[0037] While a number of exemplary aspects and embodiments have
been discussed above, those possessed of skill in the art will
recognize certain modifications, permutations, additions and
sub-combinations thereof. It is therefore intended that the
following appended claims and claims hereafter introduced are
interpreted to include all such modifications, permutations,
additions and sub-combinations as are within their true spirit and
scope.
* * * * *