Process and apparatus for laser drilling

Claim 2

A process for laser drilling a plurality of holes completely through a work piece comprising the steps of: (a) directing a pulsed laser beam onto the work piece so as to form a hole extending completely through the work piece; (b) placing an acoustic sensing means in proximity to, but not in contact with the work piece; (c) acoustically sensing the audible sound generated by the melting of the work piece caused by the laser beam pulse and converting the acoustic signal into a first electrical signal proportional to the audible sound; (d) passing the first electrical signal through a frequency filter to filter out those frequencies below a predetermined value; (e) passing the first electrical signal through an amplitude filter; (f) adjusting a threshold value of the amplitude filter such that, when the hole extends completely through the work piece and is properly sized, the amplitude of the first electrical signal is below the threshold value; (g) converting the first electrical signal into digital form by assigning a value of 1 to each laser pulse electrical signal above the threshold amplitude and a value of 0 to those below the threshold amplitude; (h) generating a second electrical signal for each pulse of the laser beam; (i) converting the second electrical signal into digital form; (j) placing the first and second electrical signals in phase with each other and generating a first input signal; (k) generating a second input signal corresponding to the number of digital pulses above the threshold amplitude necessary to properly form the hole completely through the work piece; (l) comparing the first input signal to the second input signal; (m) generating an output signal based upon the comparison of the first and second input signals; (n) displaying the output signal so as to indicate the quality of the hole being formed; and, (o) controlling one of the operating parameters of the laser with the output signal.

Claim 3

The process according to claim 1 wherein the output signal controls the energy level of the laser beam.

Claim 4

The process according to claim 1 wherein the output signal controls the duration of the laser beam pulse.

Claim 5

The process according to claim 1 wherein the output signal controls the focal point of the laser beam.

Claim 6

The process according to claim 1 wherein the output signal controls the number of pulses of the laser beam.

Claim 7

The process according to claim 1 wherein the output signal controls the rate of laser beam pulses.

Claim 8

The process according to claim 1 wherein a plurality of holes are formed in the work piece and wherein the output signal controls the operating parameters of the laser beam to correct any deficiencies in the hole being formed before the next hole is formed.

Claim 9

The process according to claim 5 comprising the additional step of generating at least one supplemental pulse of the laser beam to correct any deficiencies in the hole being formed.

Claim 10

The process according to claim 1 further comprising temporarily storing the output signal in a storage memory.

Claim 11

Apparatus for drilling a plurality of holes completely through a work piece comprising: (a) means directing a pulsed laser beam onto the work piece so as to form a hole extending completely through the work piece; (b) acoustic sensing means located in proximity to, but not in physical contact with, the work piece to sense the audible sound generated by the melting of the work piece caused by the laser beam pulses and to generate a first electrical signal proportional to the audible sound; (c) amplitude filter means connected with the acoustic sensing means to filter out a portion of the first electrical signal below a predetermined threshold amplitude; (d) means to adjust the threshold amplitude of the amplitude filter means such that, when the hole extends completely through the work piece and is properly sized, the amplitude of the first electrical signal is below the threshold amplitude; (e) first analog-digital conversion means connected to the amplitude filter means to convert the first electrical signal into digital form assigning a value of 1 to each laser pulse electrical signal above the threshold amplitude and a value of 0 to those below the threshold amplitude; (f) frequency filter means connected between the acoustic sensing means and the amplitude filter means to filter out those frequencies below a predetermined value; (g) a laser pulse detector to generate a second electrical signal in response to each pulse of the laser beam; (h) second analog-digital conversion means connected to the laser pulse detector to convert the second electrical signal into digital form; (i) recorder means connected to the first and second analog-digital conversion means to place the first and second electrical signals in phase with each other and to generate a first input signal; (j) reference value generating means to generate a second input signal corresponding to the number of digital pulses above the threshold amplitude necessary to properly form the hole completely through the work piece; (k) comparison means connected so as to receive the first and second input signals and to generate an output signal based on the comparison; (l) display means connected to the comparison means to display the output signal so as to indicate the quality of the hole being formed; and, (m) control means connected so as to receive the output signal and to control at least one of the operating parameters of the laser.

Claim 12

Apparatus for drilling a plurality of holes completely through a work piece comprising: (a) means directing a pulsed laser beam onto the work piece so as to form a hole extending completely through the work piece; (b) acoustic sensing means located in proximity to, but not in physical contact with, the work piece to sense the audible sound generated by the melting of the work piece caused by the laser beam pulses and to generate a first electrical signal proportional to the audible sound; (c) amplitude filter means connected with the acoustic sensing means to filter out a portion of the first electrical signal below a predetermined threshold amplitude; (d) means to adjust the threshold amplitude of the amplitude filter means such that, when the hole extends completely through the work piece and is properly sized, the amplitude of the first electrical signal is below the threshold amplitude; (e) first analog-digital conversion means connected to the amplitude filter means to convert the first electrical signal into digital form assigning a value of 1 to each laser pulse electrical signal above the threshold amplitude and a value of 0 to those below the threshold amplitude; (f) frequency filter means connected between the acoustic sensing means and the amplitude filter means to filter out those frequencies below a predetermined value; (g) a laser pulse detector to generate a second electrical signal in response to each pulse of the laser beam; (h) second analog-digital conversion means connected to the laser pulse detector to convert the second electrical signal into digital form; (i) recorder means connected to the first and second analog-digital conversion means to place the first and second electrical signals in phase with each other and to generate a first input signal; (j) reference value generating means to generate a second input signal corresponding to the number of digital pulses above the threshold amplitude necessary to properly form the hole completely through the work piece; (k) comparison means connected so as to receive the first and second input signals and to generate an output signal based on the comparison; (l) display means connected to the comparison means to display the output signal so as to indicate the quality of the hole being formed; and, (m) control means connected so as to receive the output signal and to control at least one of the operating parameters of the laser.

Claim 13

The apparatus of claim 10 wherein the control means is connected to the laser so as to control the energy level of the laser beam.

Claim 14

The apparatus of claim 10 wherein the control means is connected to the laser so as to control the duration of the laser beam pulse.

Claim 15

The apparatus of claim 10 wherein the control means is connected to the laser so as to control the focal point of the laser beam.

Claim 16

The apparatus of claim 10 wherein the control means is connected to the laser so as to control the number of pulses of the laser beam.

Claim 17

The apparatus of claim 10 wherein the control means is connected to the laser so as to control the pulse rate of the laser beam.