Surgery – Instruments – Light application
Reexamination Certificate
1998-10-23
2001-06-12
Leubecker, John P. (Department: 3739)
Surgery
Instruments
Light application
C606S004000, C606S010000, C606S012000, C219S121620, C356S128000
Reexamination Certificate
active
06245058
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for measuring optical characteristic of an ablation standard object ablated with laser beam, an apparatus for measuring an ablation rate comprising the same, and an apparatus comprising either the former or the latter.
2. Description of Related Art
A well known processing apparatus ablates an object with laser beam. The processing apparatus ablates a corneal surface with excimer laser beam, thereby causing its curvature to change in order to correct ametropia of an eyeball.
When an excimer laser works successively under the condition that the fixed processing condition is given, an ablation depth per one shot, at the time of irradiating the same object to be processed, is considered approximately constant. (Where the ablation depth is referred to as “ablation rate”, in the description, and one shot is referred to as “one scan” in the preferred embodiment.) However, the ablation rate often changes due to a kind of object to be processed, timing when the laser works, some factors such as output energy of the laser and the processing condition, and the like. The change of the ablation rate exerts a bad influence upon an apparatus such as to need accurate depth control, particularly upon an apparatus such as to ablate a cornea to form it into the desired and fixed shape. However, it is difficult to obtain an actual ablation rate of the cornea.
Therefore, the present applicant has been proposed an apparatus in U.S. Pat. No. 5,624,436 corresponding to Japanese Patent application laid-open No. HEI6(1994)-226471, by which the operator can easily obtain an ablation rate, the apparatus correcting based on the ablation rate. The apparatus disclosed in the publication ablates an ablation standard object having a known ablation rate (a transparent plate made from PMMA (polymethyl methacrylate)), where an ablation rate of an object (a cornea) is unknown, in order to form the ablation standard object into such a curved surface as to have the desired optical characteristic. Next, the operator measures the optical characteristic of the curved surface actually formed on the standard object with a measuring means (a lens_meter). The operator then inputs the measured data into the apparatus, then causing the apparatus to calculate the ablation rate of the object to be processed in a manner of comparing the desired optical characteristic with the actual optical characteristic, thereby correcting a driving information of the apparatus.
However, referring to above mentioned method, the operator causes the apparatus to ablate the standard object and then has to move the standard object from the ablation apparatus to a lens_meter commonly on sale in order to measure the object. It is troublesome for the operator and takes a lot of time. Accuracy of the measured results tend to be easily and subtly influenced by alignment of the standard object relative to a measuring optical system of the lens_meter and an operator's skill and knowledge for operating the same.
Further, in the case that the operator reads and inputs the results measured by the lens_meter into the ablation apparatus by using input means such as a keyboard and the like, there are possibility of artificial mistakes in reading and inputting the measured results. Input operation is also troublesome for the operator and takes a lot of time.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide an apparatus by which an operator can measure accurately and easily optical characteristic after ablating without moving an ablation standard object. Another object of the present invention is to provide an apparatus which does not make the operator feel troublesome in operation and to provide an apparatus by which the artificial mistakes can be reduced.
To achieve the objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, an apparatus for measuring an optical characteristic of an ablation standard object having a known ablation rate, as compared with an object to be processed having a unknown ablation rate which is ablated with laser beam, the apparatus comprises retaining means for retaining the ablation standard object so that a surface thereof may be at a predetermined height, refractive power measuring means for measuring a refractive power of the ablation standard object, which includes a projecting optical system for projecting target luminous flux for use in refractive power measurement onto the ablation standard object retained by the retaining means and a detecting optical system for detecting the target luminous flux projected by the projecting optical system, moving means for moving the refractive power measuring means to the predetermined measuring position in order to measure the refractive power of the ablation standard object, and output means for outputting results measured by the refractive power measuring means.
Another aspect of the present invention, the apparatus for measuring an ablation rate of an ablation apparatus which ablates an object to be processed with laser beam, the apparatus comprises retaining means for retaining an ablation standard object having a known ablation rate, as compared with said object to be processed having a unknown ablation rate, so that a surface of the ablation standard object may be at the predetermined height, refractive power measuring means for measuring a refractive power of the ablation standard object, which includes a projecting optical system for projecting target luminous flux for use in refractive power measurement onto the ablation standard object retained by the retaining means and a detecting optical system for detecting the target luminous flux projected by the projecting optical system, moving means for moving the refractive power measuring means to the predetermined measuring position in order to measure the refractive power of the ablation standard object, calculating means for calculating an ablation rate and/or its changing ratio based on results measured by the refractive power measuring means, and output means for outputting results obtained by the calculating means.
Further another aspect of the present invention, an ablation apparatus comprising laser irradiating means for irradiating with laser beam by which an object to be processed is ablated, the apparatus comprises retaining means for retaining an ablation standard object having a known ablation rate, as compared with said object to be processed having a unknown ablation rate, so that a surface of the ablation standard object may be at the predetermined height, refractive power measuring means for measuring a refractive power of the ablation standard object, which includes a projecting optical system for projecting target luminous flux for use in refractive power measurement onto the ablation standard object retained by the retaining means and a detecting optical system for detecting the target luminous flux projected by the projecting optical system, moving means for moving the refractive power measuring means to the predetermined measuring position in order to measure the refractive power of the ablation standard object, and correcting means for correcting a driving information of the laser irradiating means at the time of irradiating the object to be processed with laser beam based on results measured by the refractive power measuring means.
According to the present invention, an operator can measure accurately and easily optical characteristic after ablating without moving an ablation standard object for use in calibration. The measured results can be inputted automatically into the ablation apparatus. Accordingly, the operator does not feel troublesome in operation and the artificial mistakes can be reduced.
REFERENCES:
patent: 5261822 (1993-11-01), Hall et al.
patent: 5309214 (1994-05-01), Hashimoto
patent: 5460627 (1995-10-01), O'Donnell, Jr.
p
Farah Ahmed
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Leubecker John P.
Nidek Co. Ltd.
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