Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – With antiglare or shading
Reexamination Certificate
2001-10-06
2003-11-04
Mai, Huy (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
With antiglare or shading
C351S163000
Reexamination Certificate
active
06641261
ABSTRACT:
BACKGROUND
1. Field of Invention
Embodiments relate to lenses blocking selected wavelength ranges of light, in particular to protective eyewear using such lenses, and more particularly to such protective eyewear worn by medical personnel.
2. Related Art
Medical personnel are subject to eyestrain when working under bright medical lighting. In many instances, for example, very bright, white lighting is used in surgical and examination rooms. In other instances, such as during endoscopic or arthroscopic surgery, background lighting is dimmed and medical personnel view bright video monitors. Such bright lighting typically contains ultraviolet (UV) and far violet (short violet wavelength) light that may cause both eyestrain and eye damage. Optical filters (e.g., conventional sunglasses) exist that block portions of the UV spectrum. But medical personnel must clearly see in order to carry out medical procedures, and such UV-blocking filters unacceptably darken the viewed scene. Medical personnel also identify different objects such as different tissues by color, but such darkening filters change the perceived colors of viewed objects. Thus certain qualities of light reaching the eye should be preserved to assist medical personnel.
Light is characterized by wavelength, often measured in nanometers (nm). Light radiated by most light sources contains a multiplicity of wavelengths. The spectral radiance of a specific light source is the intensity at each wavelength of light radiated by the source. Spectral radiance is typically plotted with intensity (often normalized) in the ordinate and wavelength in the abscissa.
Color may be a physical description of light, serving as a proxy for wavelength. Color may also refer to human perception of light incident on the retina. Various theories of human color perception exist. Humans can generally perceive light in a range of wavelengths from around 400 nm to around 750 nm. However, the human eye is not equally responsive to all visible wavelengths. Instead, the eye is responsive to light in three overlapping bands: a blue band centered on about 450 nm, a green band centered on about 540 nm, and a red band centered on about 600 nm. When light having a mixture of wavelengths strikes the retina, the brain perceives the mixture color as an average of the light energy received from the component wavelengths that fall within each responsive band. For example, if a mixture of blue light and yellow light is incident on the retina, the mind perceives the color of the light mixture as green, and does not distinguish the individual blue and yellow colors. Color is therefore what the human mind perceives when one or more wavelengths of light is incident on the retina.
Human eye response to light intensity in the visible spectrum varies by wavelength.
FIG. 1
shows a representation of photopic (bright light) visual response of a typical human eye. Curve
102
is the strength of typical photopic visual response as a function of wavelength (&lgr;) and is asymmetric. Range
104
from 700-400 nm is a typical photopic visual range. Ultraviolet light is light having wavelength shorter than approximately 400 nm. As set forth in ISO 8980-3:1999(E) “Ophthalmic optics—Uncut finished spectacle lenses—Part 3: Transmittance specifications and test methods”, incorporated by reference, UV-A is defined from 380 to over 315 nm and UV-B is defined from 315 to over 280 nm. Therefore, one range of UV light is approximately 400-280 nm, and is shown as UV range
106
. Range
108
from 425-400 nm is a range of short violet light wavelengths (far violet) that humans can perceive, but for which the eye response is small. The intensity of light incident on the retina is perceived as brightness.
A hue is the color perceived when a single wavelength of light strikes the retina. A typical person perceives hues in groups of reds (longer than about 610 nm), oranges (about 610-590 nm), yellows (about 590-570 nm), greens (about 570-500 nm), blues (about 500-440 nm), and violets (less than about 440 nm). A single wavelength of light is perceived as having a dominant hue.
A tint identifies a particular mixture of light wavelengths and intensities (i.e., the spectral radiance distribution of a particular light). A particular tint is perceived as a corresponding color. The tint of an object is defined by how that object radiates light, or by how that object selectively reflects or absorbs wavelengths of light that strike the object. The perceived tint of an illuminated object is also determined by the intensity of light at various wavelengths coming from the object. When an object is illuminated by light of a particular tint, the illuminated object is perceived as having a color corresponding to a tint which is a combination of the tint of the light mixed with the tint of the object.
Tints are expressed in various ways. Tints may be expressed as mixtures of three primary colors (e.g., red, green, and blue). Tints may also be expressed as chroma (hue) and saturation. Saturation indicates how much or little white light is mixed with a (pure) chroma to make the tint. In the CIELAB system, tints are described by coordinates (L*, a*, b*). L* is luminosity (light or dark), a* is green-red balance, and b* is blue-yellow balance. A known spectral distribution of light can be mathematically transformed into CIELAB (L*, a*, b*) coordinates using methods known by skilled artisans.
In the CIELAB system, &Dgr;E is a measure of the variation between two tints, defined at coordinates (L*1, a*1, b*1) and (L*2, a*2, b*2), respectively. &Dgr;E is calculated by using Equation 1:
&Dgr;E={square root over ((&Dgr;
L
*)
2
+(&Dgr;
a
*)
2
+(&Dgr;
b
*)
2
)} [1]
where &Dgr;L*=L*1−L*2, &Dgr;a*=a*1−a*2, and &Dgr;b*=b*1−b*2. During manufacturing, for example, Equation 1 is used to compare a specified tint to a tint produced by the manufactured product (e.g., a filter). A value of 3 for such a &Dgr;E comparison is typically considered to be an acceptable manufacturing tolerance. For two identical tints, &Dgr;E is zero.
FIG. 2
is the 1931 Commission Internationale de l'Eclairage (C.I.E.) Chromaticity Diagram with typical color perceptions shown. The C.I.E. Chromaticity Diagram provides a graphical representation of tints. Since three primary colors may define a tint, if the amount of one primary color is fixed, a particular tint is defined by specifying the amounts of the other two. Consequently, two numbers are sufficient to define a mixture of three primary colors, thereby defining a tint. The defined tint is graphically shown by plotting the defining numbers (x,y) on the horizontal (x) and vertical (y) axes of the Chromaticity Diagram. For example, tint
202
is a red tint at (0.6,0.3), tint
204
is a white tint at (0.3,0.3), and tint
206
is a yellowish-green tint at (0.3,0.6). Hues (identified by wavelength in
FIG. 2
) are shown around the outside border of the Diagram.
A MacAdams ellipse is an area of the C.I.E. Diagram defining a boundary around a tint such that a person typically does not distinguish differences among tints inside the particular MacAdams ellipse. As shown in
FIG. 2
, MacAdams ellipse
208
(shown exaggerated in size) is defined around tint
204
. A typical person does not distinguish tints falling within ellipse
208
from tint
204
.
The color white describes light having equal intensity at all wavelengths in the visible spectrum. The color white also describes a human perception. Various color description systems define the perceived color white in various ways. For example, the Chromaticity Diagram depicts white as being in a center portion of the Diagram, as shown in FIG.
2
. People identify various tints as being white, although they distinguish among various “whites”. For example, some “whites” may appear bluish; others reddish.
Objects heated to a sufficiently high temperature radiate light. A heated blackbody produces a continuous spectral radiance distribution with a single peak. As a blackbody is made h
Gunday Erhan H.
Jurgens Albert M.
Miller Eric C.
Wang Charles N.
Stryker Corporation
Winston & Strawn LLP
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