Coherent light generators – Particular resonant cavity – Specified cavity component
Reexamination Certificate
1999-02-01
2001-05-15
Font, Frank G. (Department: 2877)
Coherent light generators
Particular resonant cavity
Specified cavity component
C372S099000, C372S020000, C372S108000, C372S107000
Reexamination Certificate
active
06233268
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser apparatus which is used to treat a diseased part of a patient by irradiating a treatment laser beam emitted from a laser source to the part to be treated.
2. Description of Related Art
Conventionally, there have been known laser apparatus which emit a treatment laser beam to the fundus of a patient's eye, thereby photocoagulating a part to be treated. A laser source used for such the laser apparatus excites and produces a laser beam in a laser tube. The light beam is reflected by a pair of mirrors (a reflection mirror and an output mirror) disposed in parallel and opposite to each other on both sides of the laser tube to resonate between the mirrors. Thus, a laser beam oscillation is ensured. In this case, if the setting angle of the reflection mirror deviates even a little from the proper angle, the mirror could not oscillate and emit laser beams or would reduce laser oscillating efficiency. This may cause inconveniences such as a lowering in output power of laser beams as compared with a setting power level. For solving the above problem, conventionally, the laser apparatus, upon turning the power thereof on, starts laser oscillation for an initial setting and drives the reflection mirror to rotate at the same time, thereby to measure the output power of laser beams during the rotation of the mirror. Based on the measurement results, the reflection mirror are adjusted to the angle where the highest laser oscillating efficiency can be obtained. An optimum laser oscillation can be ensured accordingly.
However, the above measurement of laser output power for an optimum laser oscillation is made by rotating the reflection mirror by every predetermined pulse, thereby taking a very long time and keeping an operator waiting for completion of the measurement.
In addition, the measurement, needing a long time, causes an increase of the consumption of electricity in the laser apparatus. As a result, the amount of heat generated is increased, resulting in a rise in temperature in the laser apparatus. This causes a problem that the temperature in the laser apparatus tends to come faster to the previously set upper limit of temperature where the laser apparatus can be operated. Especially, a laser treatment apparatus used for surgical operations would stop operating when the upper limit temperature is reached during the surgical operation. To prevent the stop of the apparatus, there is desired the laser apparatus capable of reducing the amount of heat generated therein to a minimum.
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 a laser apparatus capable of detecting fast an optimum angle of reflection mirror(s) where excellent laser oscillating efficiency can be obtained, and of reducing the consumption of electricity.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the purpose of the invention, there is provided a laser apparatus for generating laser light beams including a laser oscillation device for oscillating laser beams, a resonation device with a plurality of reflection mirrors for reflecting the laser beams oscillated by the laser oscillation device, a rotation device for rotating at least one of the reflection mirrors about a first axis and a second axis respectively, the second axis intersecting the first axis at a predetermined angle, a light quantity measurement device for measuring a light quantity of the laser beams emitted from the resonation device, a rotation angle determination device for determining a first rotation angle at which the light quantity measurement device detects an output of the laser beam from the resonation device while the reflection mirror is rotated about the first axis and the second axis respectively, and a second and a third rotation angles which are on both sides of the first rotation angle, a rotating range determination device for determining a rotating range of the reflection mirror, the range being supposed to include a rotation angle at which a maximum quantity of laser beam is obtained, based on measurement values measured by the light quantity measurement device when the reflection mirror(s) is positioned at the first, second, and third rotation angles determined by the rotation angle determination device, and an angle determination device for determining an optimum rotation angle of the reflection mirror(s) with respect to the first axis and the second axis respectively, at which the maximum quantity of laser beam is obtained, based on the measurement values measured by the light quantity measurement device when the reflection mirror is rotated successively within the rotating range determined by the rotating range determination device.
Furthermore, it is preferable that the rotation device rotates the reflection mirror sequentially at first predetermined intervals in order to search the first rotation angle.
In the laser apparatus, preferably, an interval defined by the second rotation angle and the first rotation angle and an interval defined by the third rotation angle and the first rotation angle are both the same first predetermined interval, wherein the reflection mirror is rotated within the rotating range determined by the rotating range determination device at second predetermined intervals which are smaller than the first predetermined intervals.
With the above structure, the laser apparatus of the present invention operates as follows;
If a pulse motor is used for the rotation device, for instance, assuming the first predetermined interval to be 500 pulses, the second predetermined interval to be 10 pulses, the rotation of the reflection mirror at 500 pulse intervals makes it possible to rapidly detect the first rotation angle of the reflection mirror at which the laser quantity of a predetermined level or more is obtained.
After detection of the first rotation angle, the second rotation angle and the third rotation angle are determined to be positioned on both sides of the first rotation angle and separately therefrom by the intervals corresponding to 500 pulses each. The quantity (power) of output laser beams corresponding to the three angles is compared to select one from among the three rotation angles to determine the rotating range. While the reflection mirror is rotated within the rotating range by 10 pulses each, the laser quantity at each point is measured. Thus, the optimum rotation angle of the reflection mirror, at which the maximum laser quantity is obtained, is finally determined.
According to the present invention, the optimum angle of the reflection mirror can rapidly be found. For example, although it would generally take 12 seconds to determine the optimum angle in the conventional laser apparatus, the present invention can reduce the time needed to determine the angle to less than half.
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U.S. application No. 09/012,214, Shinji et al., filed Jan. 23, 1998.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Floris Ruiz Delma R.
Font Frank G.
Nidek Co. Ltd.
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