Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2001-10-10
2004-01-20
Lester, Evelyn (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S224200, C359S290000, C359S298000, C359S578000, C345S085000, C345S108000
Reexamination Certificate
active
06680792
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to visible spectrum (which we define to include portions of the ultra-violet and infrared spectra) modulator arrays and interferometric modulation.
The first patent application cited above describes two kinds of structures whose impedance, the reciprocal of admittance, can be actively modified so that they can modulate light. One scheme is a deformable cavity whose optical properties can be altered by deformation, electrostatically or otherwise, of one or both of the cavity walls. The composition and thickness of these walls, which comprise layers of dielectric, semiconductor, or metallic films, allows for a variety of modulator designs exhibiting different optical responses to applied voltages.
One such design includes a filter described as a hybrid filter which has a narrow bandpass filter and an induced absorber. When the wall associated with the hybrid filter is brought into contact with a reflector, incident light of a certain range is absorbed. This occurs because the induced absorber matches the impedance of the reflector to that of the incident medium for the range of frequencies passed by the narrow-band filter.
The second patent application cited above describes designs which rely on an induced absorber. These designs operate in reflective mode and can be fabricated simply and on a variety of substrates.
The devices disclosed in both of these patent applications are part of a broad class of devices which we will refer to as IMods (short for “interferometric modulators”). An IMod is a microfabricated device that modulates incident light by the manipulation of admittance via the modification of its interferometric characteristics.
Any object or image supporter which uses modulated light to convey information through vision is a form of visual media. The information being conveyed lies on a continuum. At one end of the continuum, the information is codified as in text or drawings, and at the other end of the continuum, it is abstract and in the form of symbolic patterns as in art or representations of reality (a picture).
Information conveyed by visual media may encompass knowledge, stimulate thought, or inspire feelings. But regardless of its function, it has historically been portrayed in a static form. That is, the information content represented is unchanging over time. Static techniques encompass an extremely wide range, but in general include some kind of mechanism for producing variations in color and/or brightness comprising the image, and a way to physically support the mechanism. Examples of the former include dyes, inks, paints, pigments, chalk, and photographic emulsion, while examples of the latter include paper, canvas, plastic, wood, and metal.
In recent history, static display techniques are being displaced by active schemes. A prime example is the cathode ray tube (CRT), but flat panel displays (FPD) offer promise of becoming dominant because of the need to display information in ever smaller and more portable formats.
An advanced form of the FPD is the active matrix liquid crystal display (AMLCD). AMLCDs tend to be expensive and large, and are heavy users of power. They also have a limited ability to convey visual information with the range of color, brightness, and contrast that the human eye is capable of perceiving, using reflected light, which is how real objects usually present themselves to a viewer. (Few naturally occurring things emit their own light.)
Butterflies, on the other hand, achieve a broad range of color, brightness, and contrast, using incident light, processed interferometrically, before delivery to the viewer.
SUMMARY
In general, in one aspect, the invention features a modulator of light having an interference cavity for causing interference modulation of the light, the cavity having a mirror, the mirror having a corrugated surface.
In general, in another aspect of the invention, the interference modulation of the light produces a quiescent color visible to an observer, the quiescent color being determined by the spatial configuration of the modulator.
In implementations of the invention, the interference cavity may include a mirror and a supporting structure holding the mirror, and the spatial configuration may include a configuration of the supporting structure, or patterning of the mirror. The supporting structure may be coupled to a rear surface of the mirror. The invention eliminates the need for separately defined spacers and improves the fill-factor.
In general, in another aspect of the invention, the structure for modulating light includes modulators of light each including an interference cavity for causing interference modulation of the light, each of the modulators having a viewing cone. The viewing cones of the modulators are aligned in different directions.
In implementations of the invention, the viewing cones of the different modulators may be aligned in random directions and may be narrower than the viewing cone of the overall structure. Viewing a randomly oriented array of interference modulators effectively reduces the color shift.
In general, in another aspect of the invention, the modulators may be suspended in a solid or liquid medium.
In general, in another aspect of the invention, an optical compensation mechanism is coupled to the modulators to enhance the optical performance of the structure. In implementations of the invention, the mechanism may be a combination of one or more of a holographically patterned material, a photonic crystal array, a multilayer array of dielectric mirrors, or an array of microlenses. The brightness and/or color may be controlled by error diffusion. An array of modulators may be viewed through a film of material which, because of its tailored optical properties, enhances the view from a limited range of angles, or takes incident light of random orientation and orders it. The film may also enhance the fill factor of the pixel. The film may also comprise a patterned light emitting material to provide supplemental lighting.
In general, in another aspect of the invention, an optical fiber is coupled to the interference cavity. The invention may be used in the analysis of chemical, organic, or biological components.
In general, in another aspect of the invention, there is an array of interference modulators of light, a lens system, a media transport mechanism and control electronics.
In general, in another aspect, the invention features an information projection system having an array of interference modulators of light, a lens system, mechanical scanners, and control electronics. In implementations of the invention, the control electronics may be configured to generate projected images for virtual environments; and the array may include liquid crystals or micromechanical modulators.
In general, in another aspect, the invention features an electronics product having an operational element, a housing enclosing the operational element and including a display having a surface viewed by a user, and an array of interference modulators of light on the surface.
Implementations of the invention may include one or more of the following features. The operational element may include a personal communications device, or a personal information tool, or a vehicular control panel, or an instrument control panel, or a time keeping device. The array may substantially alter the aesthetic or decorative features of the surface. The aesthetic component may respond to a state of use of the consumer product. The array may also provide information. The modulation array of the housing may comprise liquid crystals, field emission, plasma, or organic emitter based technologies and associated electronics.
In general, in another aspect, the invention features devices in which aggregate arrays of interference modulators are assembled as a display, e.g., as a sign or a billboard.
In general, in another aspect, the invention features a vehicle having a body panel, an array of interference modulators of light on a surface of the body panel, and electronic circuitry
Blakely , Sokoloff, Taylor & Zafman LLP
Iridigm Display Corporation
Lester Evelyn
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