U.S. patent application number 09/812064 was filed with the patent office on 2002-05-02 for wavlength specific coating for mirrored optics and method for reducing reflection of white light.
This patent application is currently assigned to HONEYWELL, INC.. Invention is credited to Blitstein, Jeffrey L..
Application Number | 20020051286 09/812064 |
Document ID | / |
Family ID | 26936285 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020051286 |
Kind Code |
A1 |
Blitstein, Jeffrey L. |
May 2, 2002 |
Wavlength specific coating for mirrored optics and method for
reducing reflection of white light
Abstract
An amorphous diamond coating applied onto mirrored optics in an
infrared motion sensor to block specific wavelengths of energy from
a "white light" source like a halogen lamp, without reducing the
reflectivity of the mirror surface in the Mid-Infrared wavelengths.
A specific thickness of diamond-like-coating is applied on top of
the reflective metal surface of a mirrored part, thereby reducing
the mirror's reflectivity at visible and near-Infrared wavelengths
known to be problematic for IR motion sensors, such as those
emitted from halogen lamps. The coating has no significant
detrimental effect on mid-infrared reflectivity, so the IR motion
sensor's performance is otherwise unaffected.
Inventors: |
Blitstein, Jeffrey L.;
(Folsom, CA) |
Correspondence
Address: |
John P. O'Banion
O'BANION & RITCHEY LLP
Suite 1550
400 Capitol Mall
Sacramento
CA
95814
US
|
Assignee: |
HONEYWELL, INC.
|
Family ID: |
26936285 |
Appl. No.: |
09/812064 |
Filed: |
March 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60244045 |
Oct 27, 2000 |
|
|
|
Current U.S.
Class: |
359/350 ;
252/587; 359/589; 359/885 |
Current CPC
Class: |
G02B 5/0808 20130101;
G02B 5/0866 20130101; G02B 5/208 20130101 |
Class at
Publication: |
359/350 ;
359/885; 252/587; 359/589 |
International
Class: |
G02B 001/00 |
Claims
What is claimed is:
1. A method of reducing the incidence of visible and near-infrared
light impinging on a reflective surface of an optical reflector,
comprising overlaying said reflective surface with a layer of
non-crystalline carbon material.
2. A method as recited in claim 1, wherein said non-crystalline
carbon material comprises amorphous diamond.
3. A method as recited in claim 1, wherein said non-crystalline
carbon material comprises a diamond-like coating.
4. A method of reducing the incidence of visible and near-infrared
light impinging on a reflective surface of an optical reflector,
comprising coating said reflective surface with a diamond-like
coating.
5. A method as recited in claim 4, wherein said diamond-like
coating comprises a non-crystalline carbon material.
6. A method as recited in claim 4, wherein said diamond-like
coating comprises an amorphous diamond material.
7. A mirror, comprising: (a) a substrate base; (b) a layer of
reflective material adjacent to said substrate base; and (c) a
light absorbing layer adjacent to said layer of reflective
material.
8. A mirror as recited in claim 7, wherein said light absorbing
layer comprises a non-crystalline carbon material.
9. A mirror as recited in claim 7, wherein said light absorbing
layer comprises an amorphous diamond material.
10. A mirror as recited in claim 7, wherein said light absorbing
layer comprises a diamond like coating.
11. A mirror as recited in claim 7, wherein said light absorbing
layer absorbs light in the visible and near-infrared regions.
12. A mirror, comprising: (a) a substrate base; (b) a layer of
reflective material adjacent to said substrate base; and (c) a
diamond-like coating over said layer of reflective material.
13. A mirror as recited in claim 12, wherein said diamond-like
coating absorbs light.
14. A mirror as recited in claim 12, wherein said diamond-like
coating absorbs light in the visible and near-infrared regions.
15. A mirror as recited in claim 12, wherein said diamond-like
coating comprises a non-crystalline carbon material.
16. A mirror as recited in claim 12, wherein said diamond-like
coating comprises an amorphous diamond material.
17. A mirror, comprising: (a) a substrate base; (b) a layer of
reflective material adjacent to said substrate base; and (c) a
layer of non-crystalline carbon material adjacent to said layer of
reflective material, wherein said layer of reflective material is
between said substrate base and said layer of non-crystalline
carbon material.
18. A mirror as recited in claim 17, wherein said non-crystalline
carbon material absorbs light.
19. A mirror as recited in claim 17, wherein said non-crystalline
carbon material absorbs light in the visible and near-infrared
regions.
20. A mirror as recited in claim 17, wherein said non-crystalline
carbon material comprises a diamond-like coating.
21. A mirror as recited in claim 20, wherein said non-crystalline
carbon material comprises an amorphous diamond material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from U.S. provisional
application Ser. No. 60/244,045 filed on Oct. 27, 2000.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
[0003] Not Applicable
BACKGROUND OF THE INVENTION
[0004] Infrared motion sensors such as those used for detecting
human targets are typically subjected to various sources of
radiation during their operation. Furthermore, motion sensors using
mirrored optics are generally unprotected from various undesired
wavelengths of incoming radiation. As a result, most of the energy
that reaches the mirror surface is reflected and focused onto the
infrared detector. This causes false alarms and/or other inaccurate
detection events.
[0005] Sunlight, as well as well as tungsten/halogen lamp sources
such as automobile headlamps, produce one type of electromagnetic
radiation that is known to promote false alarms in infrared motion
sensors. These radiation sources emit radiation in both the visible
(e.g., 360 nm to 760 nm) and the infrared (e.g., 760 nm to 50
.mu.m) spectrum. Accordingly, compliance testing of infrared motion
sensors in various countries often involves the use of a halogen
light source at fairly intense levels (e.g., 2000 to 6000 lux) to
determine the immunity of the motion sensor to this type of
radiation.
[0006] It has been the attempt of many manufacturers of motion
sensors to develop improved ways to make the infrared sensing
elements less susceptible to the effects of these types of light
sources. For example, some sensors use a protective absorbing layer
beneath the reflective layer of the mirror (see, for example, U.S.
Pat. No. 5,608,220 to Wieser et al., incorporated herein by
reference) to remove potentially harmful radiation from the
detector path. However, there is still a need for a more effective
manner in which to inhibit visible and near infrared light
(sometimes referred to as "white light" in the motion sensor
industry) to protect the sensing element(s).
BRIEF SUMMARY OF THE INVENTION
[0007] By way of example, and not of limitation the invention
comprises a method of reducing the incidence of visible and
near-infrared light impinging on a reflective surface of an optical
reflector by overlaying said reflective surface with a layer of
non-crystalline carbon material. The invention also comprises a
mirror having a substrate base, a layer of reflective material
adjacent to the substrate base, and a light absorbing layer
adjacent to the layer of reflective material. In the preferred
embodiment of the invention, a diamond-like-coating (DLC)
protective layer is placed on top of a reflective (e.g.,
metallized) mirror surface. This amorphous diamond coating has been
developed for this application by Diamonex Performance Products,
Allentown, Pa. and is referred to by Diamonex as "DLC-B".
[0008] An object of the invention is to coat the surface of a
mirror with a protective layer that absorbs broad-band visible and
near-infrared radiation so that said radiation is reduced before it
reaches the infrared (IR) sensor.
[0009] Another object of the invention is to coat the surface of a
mirror with a material that acts as a protective over-coating to
prevent damage to the mirror surface due to abrasions, oxidation,
corrosion, or atmospheric contamination.
[0010] Another object of the invention is to coat the surface of a
mirror with a material that can be "tuned" to selectively block a
specific wavelength of IR and/or visible energy (to below 10% of
incident radiation) which are determined to be most adverse to the
performance of the infrared sensor.
[0011] Another object of the invention is to coat the surface of a
mirror with a material that functions as an optical "notch" filter,
with excellent suppression of selectable wavelengths, while
otherwise being a reasonably good reducer of broad-band visible and
near-infrared (NIR) radiation.
[0012] In addition, the coating has been shown to have little
impact in the mid-infrared portion of the spectrum, where typical
infrared motion sensors operate. In contrast, other alternative
solutions, such as silicon-based windows or filters, will still
reduce the amount of available mid-infrared energy by more than
20%. The present invention, however, deters MIR radiation by 5% or
less.
[0013] Applications of this technology include, but are not limited
to, lighting controls, motion sensors for security and lighting and
other controls, temperature sensors and thermal controls, and
thermal imaging.
[0014] Further objects and advantages of the invention will be
brought out in the following portions of the specification, wherein
the detailed description is for the purpose of fully disclosing
preferred embodiments of the invention without placing limitations
thereon.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The invention will be more fully understood by reference to
the following drawings which are for illustrative purposes
only:
[0016] FIG. 1 is schematic view of an embodiment of a mirror
employing a diamond-like light absorbing coating according to the
invention.
[0017] FIG. 2 is a graph showing the near-infrared blocking
bandwidth of a DLC-chrome coating according to the present
invention.
[0018] FIG. 3 is a detailed view of a portion of the graph show in
FIG. 2.
[0019] FIG. 4 is a graph showing the mid-infrared reflectance of a
DLC-B coating over a chrome mirror in accordance with the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Referring to FIG. 1, an embodiment of mirror employing a
diamond-like-coating according to the present invention is shown.
As shown, the mirror 10 comprises a substrate base 12, a first
binding layer 14 overlaying the base 12, a metallized reflective
coating 16 overlaying the first binding layer 14, a second binding
layer 18 overlaying the reflective coating 16, and an absorbing
layer 20 overlaying the second binding layer 18.
[0021] Substrate base 12 is preferably a machined or molded
material which can be electro-plated or coated. The preferred
material is acrylonitrile-butadiene-styrene (ABS) plastic, but
other materials can be used as well. Examples of other suitable
materials for use as the substrate base include polyvinyl chloride,
acetal (Delrin.RTM.), nylon, polypropylene, polystyrene,
polymethyl-methacrylate (PMMA, or "acrylic" plastic), polycarbonate
plastic, glass, or aluminum. The thickness of substrate base 12 can
be any desired thickness.
[0022] With regard to binding layers 14, 18, silicon is preferred
for its adhesion characteristics. Binding layer 14 is preferably
approximately 25 angstroms thick, and binding layer 18 is
preferably approximately 175 angstroms thick.
[0023] Metallized layer 16 comprises the reflective mirror surface
for infrared (IR) radiation, and can be made of any metallic
substance which can be electroplated or vacuum deposited and which
has the desired reflective properties. Chrome, having a thickness
of approximately 1700 angstroms, is particularly well suited for
this application. However, other materials can be used, such as
aluminum, nickel or titanium. Alternatively, metallized layer 16
could be any IR reflecting substrate without a coating, such as Mo,
Cr, Al, Ag, or Ti.
[0024] Absorbing layer 20 is preferably a diamond-like-coating
(DLC) made of amorphous (non-crystalline) diamond (carbon) applied
by means of vacuum deposition. Examples of suitable methods for
producing diamond-like coatings are described in U.S. Pat. Ser.
Nos. 4,728,329 and 5,643,641, both of which are incorporated herein
by reference. This material is available from Diamonex Performance
Products, Allentown, Pa. under the designation "DLC-B". Preferably,
absorbing layer 20 has a thickness of approximately 1000 angstroms,
although experimental results indicate that thicknesses can range
from approximately 600 angstroms to approximately 1000 angstroms.
Other thicknesses may be suitable as well; however, increasing the
coating thickness changes the absorption spectra of the coating
towards shorter wavelengths. Further, while DLC-B is the preferred
coating material, other materials that can be used include Diamonex
NILAD (non-interlayer amorphous diamond), or Diamonex "DLC-A".
[0025] It will be appreciated that radiation 22 passing through the
widow of the motion sensor has a mid-infrared radiation component
24 and a visible and near-infrared radiation component 26.
Accordingly, the advantage of using absorbing layer 20 on a mirror
in a motion sensor is that the visible and near-infrared radiation
component 26 will be absorbed by absorbing layer 20. On the other
hand, the mid-infrared radiation component 24 will be reflected by
the metallized reflective coating 16 and directed as a beam 28 onto
the infrared detector 30.
[0026] FIG. 2 and FIG. 3 are graphs showing the near-infrared
blocking bandwidth of a DLC-chrome coating according to the present
invention, and FIG. 4 is a graph showing the mid-infrared
reflectance of a DLC-chrome coating according to the present
invention. In FIG. 2, the results of a visible-near infrared
reflectance scan for DLC over chrome on an ABS witness plate show
an average reflectance of 13.1% over the range of 360 nm to 1100
nm. In FIG. 3, which is a detailed view of a portion of the graph
in FIG. 2, the results show an average reflectance of 2.67% over
the range of 800 nm to 1000 nm and a minimum reflectance of 1.81%
at 900 nm. In FIG. 4, the results for a DLC-B sample over chrome on
an ABS witness plate show that mid-infrared radiation is not
absorbed.
[0027] As can be seen, these characteristics demonstrate that the
incidence of false alarms will be greatly reduced. Absorbing layer
20 absorbs broad-band visible and near-infrared radiation so that
said radiation is reduced before it reaches the infrared (IR)
sensor, acts as a protective over-coating to prevent damage to the
mirror surface due to abrasions, oxidation, corrosion, or
atmospheric contamination, and can be "tuned" by varying the
thickness to selectively block specific wavelengths of IR and/or
visible energy (to below 10% of incident radiation) which are
determined to be most adverse to the performance of the infrared
sensor. As indicated above, the coating thickness changes the
absorption spectra of the coating towards shorter wavelengths. In
essence, the coating is an optical "notch" filter, with excellent
suppression of selectable wavelengths, while otherwise being a
reasonably good reducer of broad-band visible and near-infrared
(NIR) radiation.
[0028] Although the description above contains many specificities,
these should not be construed as limiting the scope of the
invention but as merely providing illustrations of some of the
presently preferred embodiments of this invention. Thus the scope
of this invention should be determined by the appended claims and
their legal equivalents. Therefore, it will be appreciated that the
scope of the present invention fully encompasses other embodiments
which may become obvious to those skilled in the art, and that the
scope of the present invention is accordingly to be limited by
nothing other than the appended claims, in which reference to an
element in the singular is not intended to mean "one and only one"
unless explicitly so stated, but rather "one or more." All
structural, chemical, and functional equivalents to the elements of
the above-described preferred embodiment that are known to those of
ordinary skill in the art are expressly incorporated herein by
reference and are intended to be encompassed by the present claims.
Moreover, it is not necessary for a device or method to address
each and every problem sought to be solved by the present
invention, for it to be encompassed by the present claims.
Furthermore, no element, component, or method step in the present
disclosure is intended to be dedicated to the public regardless of
whether the element, component, or method step is explicitly
recited in the claims. No claim element herein is to be construed
under the provisions of 35 U.S.C. 112, sixth paragraph, unless the
element is expressly recited using the phrase "means for."
* * * * *