Method for grinding lens

A method for grinding lens is provided in the invention. First, a lens which has an optical surface and a surface-to-be-grinded is placed on a polishing pad. Next, cover up the lens with a fluid guiding tube wherein the fluid guiding tube has a fluid inlet and a fluid outlet with the fluid outlet being situated at the top of the polishing pad for accommodating the lens. After that, a fluid is introduced into the fluid guiding tube through the fluid inlet and is discharged from the fluid outlet, and the flow of the fluid follows the normal direction of the optical surface and applies force evenly thereon. Last, the polishing pad is moved along with the tangent line of its surface for the surface-to-be-grinded to be grinded.

This application claims the benefit of Taiwan application Serial No. 092127520, filed Oct. 3, 2003, the subject matter of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to a method for grinding lens, and more particularly to a method for grinding lens without mechanic contact.

2. Description of the Related Art

Of today's laser processing technology, gas laser has been widely used in drilling, cutting, engraving, welding, material heat treatment, and so on. In the technology of gas laser, gas is used as an active medium and is sealed inside a resonant cavity. The resonant cavity consists of two pieces of lens: the front one is a semi-reflecting lens while the rear one is a total-reflecting lens. Each of the two lenses has an optical surface and a gas contact surface, wherein the gas contact surface contacts with the gas which is sealed inside the resonant cavity. The operation of gas laser is that when a voltage or a current passes through an optical resonant cavity, the gas will be excited to create a monochromatic narrow light-beam of high homology which can be focused on a tiny spot with great precision for laser processing. The oscillation frequency of the laser light has much to do with the penetration rate of the lens used in the resonant cavity, i.e., the lower the penetration rate, the higher the oscillation frequency.

It is noteworthy that after a period of gas laser operation some blemishes or spots which severely affect lens quality will be formed on the gas contact surface of the lens, so the lens needs to be replaced after a certain period of operation. Since the lens used in gas laser is very expensive, lens replacement is a big expenditure for gas laser operation. As shown inFIG. 1, since optical surface13of lens12is so sensitive that an operator cannot use any mechanic tool for polishing pad15to grind surface-to-be-grinded14, the other side of lens corresponding to optical surface13. Even if force is applied from the lateral side of the lens, the conventional grinding method with mechanic contact still cannot apply the force evenly to achieve an even grinding. That is to say, when polishing pad15moves along with the direction of arrow50inFIG. 1, surface-to-be-grinded14will not be able to move in parallel to polishing pad15due to the force coming from the lateral side of lens12. Particularly, the higher the level of evenness required is, the poorer the result of the above method will be.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a lens grinding method, whose non-mechanic contact design of using fluid to apply force onto optical surface not only prevents the optical surface from being blemished when grinding the surface-to-be grinded but also improves lens utilization and hence reduces lens replacement expenditure.

It is therefore an object of the invention to provide a lens grinding method. First, a lens is placed on the surface of a polishing pad, wherein the lens has an optical surface and a surface-to-be-grinded corresponding to each other, and the surface-to-be-grinded contacts with the surface of the polishing pad. Next, cover up the lens with a fluid guiding tube wherein the fluid guiding tube has a fluid inlet and a fluid outlet corresponding to each other. The fluid outlet situated at the top of the polishing pad for accommodating the lens has a plurality of baffles for contacting with the lateral side of the lens and for holding the lens accordingly. After that, a fluid is introduced into the fluid guiding tube through the fluid inlet and is discharged from the fluid outlet. The flow of the fluid follows the normal direction of the optical surface and applies force evenly thereon, so that a tight contact between the surface-to-be-grinded and the polishing pad can be created. Last, the polishing pad is moved along with the tangent line of its surface for the surface-to-be-grinded to be grinded.

It is therefore an object of the invention to provide a lens grinding method. First, a lens is placed on the surface of a polishing pad, wherein the lens has an optical surface and a surface-to-be-grinded corresponding to each other, and the surface-to-be-grinded contacts with the surface of the polishing pad. Next, cover the lens with a fluid guiding tube wherein the fluid guiding tube has a fluid inlet and a fluid outlet corresponding to each other. The fluid outlet situated at the top of the polishing pad for accommodating the lens has a plurality of baffles for contacting with the lateral side of the lens and for holding the lens accordingly. After that, a liquid is introduced into the fluid guiding tube through the fluid inlet and is discharged from the fluid outlet. The flow of the liquid follows the normal direction of the optical surface and applies force evenly thereon so that a tight contact between the surface-to-be-grinded and the polishing pad can be created. Following that, the polishing pad is moved along with the tangent line of its surface for the surface-to-be-grinded to be grinded. After that, halt the movement of the polishing pad when the grinding of the surface-to-be-grinded is finished. Last, halt the supply of the liquid then introduce a gas into the fluid guiding tube from the fluid inlet to dry the optical surface.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a lens grinding method for grinding the lens having an optical coat and a surface-to-be-grinded which correspond to each other. This method prevents the optical surface of the lens from being blemished when grinding the surface-to-be-grinded hence improves lens utilization and reduces lens replacement expenditure.

Referring toFIG. 2, a flowchart showing the lens grinding method according to the preferred embodiment of the invention. First, start with step202: a lens312is placed on the surface of a polishing pad315, wherein lens312has an optical surface313and a surface-to-be-grinded314corresponding to each other, and the surface-to-be-grinded contacts with the surface of the polishing pad as shown inFIG. 3andFIG. 4. The optical surface313includes at least one optical thin film formed on the lens. Next, proceed to step204: cover up lens312with a fluid guiding tube320wherein fluid guiding tube320has a fluid inlet322and a fluid outlet324corresponding to each other with fluid outlet324being situated at top of polishing pad315for accommodating lens312as shown inFIG. 5. The opening of fluid inlet322is smaller than that of fluid outlet324which has a plurality of baffles, three baffles326for instance, for contacting with the lateral side of lens312and for holding lens312accordingly.

After that, proceed to step206: a fluid328is introduced into fluid guiding tube320through fluid inlet322and is discharged from fluid guiding tube320via the gap between fluid guiding tube320and the lateral side of lens312as well as via fluid outlet324as shown inFIG. 6. InFIG. 6, when flowing through fluid guiding tube320, fluid328will lash against the surface of optical surface313and evenly apply force on the surface of optical surface313along with the normal direction thereof, so that a tight contact between surface-to-be-grinded314and polishing pad315can be created. The fluid328must not have any reaction with optical surface313. Following that, polishing pad315is moved along with the tangent line of its surface for grinding surface-to-be-grinded314.

Furthermore, lens312can be a lens used in gas laser or a lens supposed to be disposed. According to the invention, a lens supposed to be disposed in gas laser can be recycled to be further utilized after having been grinded again. Consequently, the lens replacement expenditure is reduced.

If fluid328is de-ionized water or other liquids, after surface-to-be-grinded314has been grinded, the invention can further comprise the following steps. First, halt the movement of polishing pad315. Next, halt the supply of de-ionized water or other liquids then introduce a gas into fluid guiding tube320through fluid inlet322to dry optical surface313, lest traces of water or other liquids might be left thereon. The gas used to dry optical surface313is a hot nitrogen gas.

The lens grinding method disclosed in the above preferred embodiment adopts a non-mechanic contact design, which uses fluid to apply force onto an optical surface, not only prevents the optical surface of the lens from being blemished when grinding the surface-to-be-grinded, but also improves lens utilization and hence reduces lens replacement expenditure.