Laser energy measuring unit and laser machining apparatus

1. A laser energy measuring unit comprising:

a mask having a plurality of mask holes with different diameters, said mask being configured so that one of said mask holes is selectively positioned within an optical path of a laser beam;

an attenuating member within the optical path of the laser beam downstream of said mask so as to attenuate energy of the laser beam having passed through said mask, said attenuating member having:

a circular shading portion located so as to block a center part of the laser beam having passed through said mask from passing through said attenuating member at a position coincident with a center of the laser beam having passed through said mask; and

a plurality of through holes arranged around said circular shading portion for attenuating the laser beam having passed through said mask, said through holes being formed in a formation area of said attenuating member wider than a spread area of said attenuating member through which energy of the laser beam having passed through said mask is distributed;

a measuring device for measuring the energy of the laser beam having passed through said attenuating member such that a center part of an energy of the laser beam has been blocked by said circular shading portion of said attenuating member to thereby minimize the energy of the laser beam; and

a condenser lens located at one side of said attenuating member, said condenser lens being configured to condense the laser beam having passed through said mask to said measuring device.

2. The laser energy measuring unit of claim 1 , wherein said measuring device includes:

a sensor for sensing an energy level of the laser beam having passed through said attenuating member; and

a calculation section for comparing an energy level sensed by said sensor to a pre-set energy value.

3. The laser energy measuring unit of claim 1 , wherein said shading portion is located so as to block a center-most part of the laser beam having passed through said mask from passing through said attenuating member at a position coincident with a center-most axis of the laser beam having passed through said mask.

4. A laser machining apparatus, comprising:

a branching member for splitting a laser beam oscillated from a laser oscillator into a machining laser beam for machining workpieces and a measuring laser beam to be measured to determine an energy level of the laser beam; and

a laser energy measuring unit for measuring the energy level of the measuring laser beam, and for detecting an abnormal condition when the measured value of the measuring laser beam deviates from a predetermined range, said laser energy measuring unit comprising:

a mask having a plurality of mask holes with different diameters, said mask being configured so that one of said mask holes is selectively positioned within an optical path of the laser beam;

an attenuating member within the optical path of the measuring laser beam downstream of said mask so as to attenuate energy of the measuring laser beam, said attenuating member having:

a circular shading portion located so as to block a center part of the measuring laser beam from passing through said attenuating member at a position coincident with a center of the measuring laser beam; and

a plurality of through holes arranged around said circular shading portion for attenuating the measuring laser beam, said through holes being formed in a formation area of said attenuating member wider than a spread area of said attenuating member through which energy of the measuring laser beam is distributed;

a measuring device for measuring the energy of the measuring laser beam having passed through said attenuating member such that a center part of an energy of the laser beam has been blocked by said circular shading portion of said attenuating member to thereby minimize the energy of the laser beam; and

a condenser lens located at one side of said attenuating member, said condenser lens being configured to condense the measuring laser beam having passed through said mask to said measuring device;

wherein said branching member is located downstream of said mask so as to split the laser beam having passed through said mask.

5. The laser machining apparatus of claim 4 , wherein said measuring device includes:

a sensor for sensing an energy level of the measuring laser beam having passed through said attenuating member; and

a calculation section for comparing an energy level sensed by said sensor to a pre-set energy value.

6. The laser machining apparatus of claim 5 , further comprising a control section for receiving a signal from said measuring device, and for stopping a machining operation when the energy level sensed by said sensor deviates from the pre-set energy value.

7. The laser machining apparatus of claim 4 , wherein said shading portion is located so as to block a center-most part of the laser beam having passed through said mask from passing through said attenuating member at a position coincident with a center-most axis of the laser beam having passed through said mask.

8. The laser energy measuring unit of claim 1 , wherein said through holes of said attenuating member are arranged so as to entirely surround said circular shading portion.

9. The laser machining apparatus of claim 4 , wherein said through holes of said attenuating member are arranged so as to entirely surround said circular shading portion.