Surgery – Instruments – Light application
Reexamination Certificate
2002-07-31
2004-08-03
Gibson, Roy D. (Department: 3739)
Surgery
Instruments
Light application
C606S004000, C349S086000
Reexamination Certificate
active
06770068
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a controllable electro-optical patternable mask for controlling electromagnetic energy, particularly an electro-optical mask which utilizes electrochromic or substrate-dispersed liquid crystal cells for transmission control, and a system which involves the use of the controllable mask for use in, for example, an ophthalmic surgical system such as an excimer laser system using ultraviolet electromagnetic energy for contouring the cornea through controlled ablation of the cornea, a photoresist system, a microelectronics system, or a photolithography system, as well as other types of ablation systems.
BACKGROUND OF THE INVENTION
Prior art electrochromic devices are known that include a layer of an electrochromic material, such as MoO
3
, sandwiched between two transparent electroconductive electrode layers, for example, of indium-tin oxide(ITO). A layer of an H± or Li± ion-conducting material is present between an electrode and the electrochromic material. Electrochromic devices also include devices having an ion-storage layer for storing ions. The application of an electric potential of a few volts across the electrodes causes the color of the layer stack to change. The color change is reversible.
Electro-optical devices containing an electrochromic material layer have been used in conjunction with an anti-dazzling mirror, a light control window and various kinds of display devices as described in U.S. Pat. No. 4,617,619 to Kamimari et al. Electro-optic devices utilizing the electrochromic action (i.e., induced color changes in material such as, e.g., WO
3
, MoO
3
and V
2
O
5
) have also been studied with regard to communication systems using visible or near visible electromagnetic radiation as a message carrier. An example can be seen in U.S. Pat. No. 4,245,883. Reference is also made to U.S. Pat. No. 5,970,187 describing an electrochromic optical switching device and referring to use of the switching devices in rear view mirrors, sun roofs, architectural glass, vision control glass, displays and display screen with variable transmission. These patents are incorporated herein by reference.
U.S. Pat. No. 5,742,362 discloses a process for forming photosensitive material for the manufacture of wiring board which features an exposure apparatus comprising a liquid crystal display for displaying a mask pattern and memory means storing a transmissivity pattern with the transmissivity of each cell of the liquid crystal display element being adjusted in accordance with the transmissivily pattern. Reference is also made to U.S. Pat. No. 5,105,215 entitled “Liquid Crystal Programmable Photoresist Exposure System.” These two patents are incorporated by reference.
Electrochromic displays are also known and feature devices that employ a reversible electrochemical reaction to cause a change in color of segments patterned to form alphanumeric characters. Electrochromic displays are passive devices that only modulate ambient light, in contrast to an active liquid crystals that twist ambient polarized light or active light-emitting diode displays that do not modulate light but instead produce light. Hence, the electrochromic displays operate at low voltages, and have a low enough energy requirement that a watch-size display can be operated for about 1 year from a small commercial battery. In the off state, the segments are typically colorless; in the on state, they are brightly colored, for example, blue or purple.
The structure of an electrochromic display package typically consists of two substrate glass pieces, two transparent voltage electrodes, two electrochromic electrodes and one hydrophobic Li electrolyte. All pieces are held together with a solder-glass, or epoxy, seal. To operate the device, a dc potential of 1-1.5 V is applied to the voltage electrodes to activate, the electrochemical electrodes for the electrochromic oxidation and reduction process (redox reaction).
Electrochromic displays can be categorized in two types, bistable, which means that once the color has been switched, the state of the device remains, even in the absence of applied voltage. Limitations of these types of systems includes the slowness of the color change, due to the low migration ratio and the difficulties to obtain strong color changes. In the second type, two complementary electrochromic molecules are dissolved in a solvent. One becomes colored by oxidation and the other by reduction. Thus, this type of system is relatively simple to build, reacts very fast and produces dark colors.
Single layer electro-optical polymer dispersed cells have recently gained attention in the display field and work on the principle of very fine microbubbles trapped into a substrate. When no voltage is applied, the bubbles will take on a random polar orientation. Thus, if a voltage is applied to the cell the bubbles will orientate and align with the electric field, if the substrate carefully matches the index and the director for polarized light of the bubbles, the light will propagate all the way through the material without being reflected at the bubbles and without the need for polarizers.
In the field of laser surgery efforts have been made to ablate an exposed cornea in an effort to achieve a pre-determined volumetric ablation pattern to the exposed cornea. In this regard, various surgical techniques for reprofiling of the corneal surface have been proposed as described in, for example, L'Esperance, U.S. Pat. No. 4,732,14; J. T. Lin, U.S. Pat. No. 5,520,679; David F Muller, U.S. Pat. No. 4,856,513; Kristian Hohla, U.S. Pat. No. 5,520,679, these patents are also incorporated by reference herein.
In practice there are two basic techniques to ablate and remove a set volume of tissue in the cornea and they are:
1) a scanning technique that uses a small flying laser spot between 1-2 mm in diameter and requires thousands of pulses to do the surgery; and
2) a large spot beam technique wherein a laser beam of around 8 mm in cross-section is used in conjunction with an erodible mask or a moving, blocking mask to ablate and which generally requires, on average, a few hundred pulses to achieve the desired ablation.
The main advantage of a flying laser spot technique is the ability to readily execute irregular patterns. However, the flying laser spot technique suffers from the drawback of generally requiring longer surgical times to execute the desired ablation pattern both from the standpoint of the number of pulses required and the overlapping requirement to ensure coverage of the ablated area. Any increase in the length of time required to carry out the laser ablation process can lead to longer corneal exposure time and corresponding medical concerns such as cornea dehydration which can lead to poorer healing, poorer visual acuity and, in general, longer post operative recovery times. A longer time period in which a laser is operated per patient also leads to a decrease in the useful life of the laser and an increase in service requirements. Flying laser spot techniques place greater stress on the laser cavity and the optical train components due to high repetition and rate requirements.
A flying laser spot technique also leaves ridges and valleys as a result from overlapping and the resultant ablated surface will not be a highly smooth and polished ablation.
A large beam spot system does allow for more rapid application of the desired energy (including the avoidance of the degree of overlapping involved in a randomly or non-randomly applied, partially overlapping flying spot system) and typically places less strain on the laser equipment, but does not have the irregular pattern versatility provided with a flying spot system. Also, if mechanically moving components are relied upon as the means for blocking or allowing through the laser beam (e.g., an iris or rotating or sliding aperture plate, then the problems of mechanical wear, potential jamming or breakdown arise).
Attempts have been made to provide masks that operate with a large beam application in
Matallana Eduardo
Ruiz Antonio
Gibson Roy D.
Johnson Henry M.
Smith , Gambrell & Russell, LLP
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