JPS6135867B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser processing device that can be applied to processing such as a laser scalpel that cauterizes human tissue with a laser beam and cuts it, and melt cutting of various materials.

In recent years, various types of lasers have been developed, and their application fields have expanded significantly. Particularly in the field of laser processing, which uses lasers as a source of optical energy, many so-called laser scalpels for the human body and cutting machines for various materials have come into existence.

By the way, in this type of laser processing, especially in laser scalpels, controlling the depth of cut is even more important than safety, and various methods have been proposed to date to control this depth.
There is no method that can accurately measure and control the depth of a laser-processed part. This is due to the difficulty in measuring the depth of minutely processed parts because laser processing uses extremely focused laser light. Conventionally, the depth near the laser beam irradiation area has been measured by optical means, which has caused safety problems.

The object of the present invention is to provide a laser processing device that solves these problems.The purpose of the present invention is to provide a laser processing device that uses pulsed sound from the workpiece (laser light irradiation part) and uses the received measurement value of this pulsed sound to generate laser light. The machining depth is controlled by adjusting the oscillation.

A specific method for generating pulsed sound from the laser irradiation unit, that is, the workpiece during processing, modulates the output of the irradiated laser light into a pulsed form, and for this purpose, a pulse oscillation unit is provided in the laser oscillator. Pulse sound from the object to be processed, particularly from the point where the laser beam is irradiated, is received by, for example, a microphone with good directivity installed near the laser oscillator. The machining depth can be determined by measuring the time delay of this received signal from the time of pulsed laser light oscillation, that is, the time from the time of pulsed laser light oscillation to the time of pulsed sound reception. The device is configured to stop (interrupt) the oscillation of the laser beam when it becomes impossible to receive the pulsed sound.

This will be explained below with reference to the drawings.

1 is a laser oscillator, and a continuous wave (CW) laser oscillation section 1' and a pulsed laser oscillation section 1'' are installed in the resonator. Therefore, the laser light output 3 from this laser oscillator 1 is As shown in FIG. 2, it has a form in which a continuous wave (CW) component, which is advantageous for processing, and pulse components P ₁ and P ₂ for generating sound from the irradiation point are added.

Pulsed sound 3' generated from the laser irradiation point on the workpiece 2 is received by a highly directional microphone 4 installed near the laser oscillator 1.
The output signal of the microphone 4 is input to a time delay measuring circuit 5.

Reference numeral 6 denotes a pulse laser power supply section that excites the pulsed laser oscillation section 1'', and this power supply section 6 transmits a reference signal to the time delay measuring circuit 5 when the pulsed laser beam is oscillated.When this reference signal is generated, In FIG. 2, they are indicated by t ₀ , t ₀ ′, . . . .

FIG. 2 shows the output signal from the microphone 4, that is, the pulse acoustic output P, and the pulse acoustic output corresponding to the pulse component P ₁ in FIG.
PO ₁ , and similarly the acoustic output corresponding to pulse component P ₂ is PO ₂ . The time delay Δt between the signals P ₁ and PO ₁ is measured by the time delay measuring circuit 5. The machining depth is determined by this measured value △t as described later, and when △t is outside the set delay time, a control signal is output and the signal is sent to the continuous wave laser oscillation unit via the laser power control circuit 7. 1′
A laser power source 8 that excites is controlled. That is, when the measured value Δt deviates from the set delay time, the oscillation of the laser beam from the laser oscillator 1 is stopped, and as a result, the machining depth is controlled.

The delay time set above is △ in Figure 2 3.
Although indicated by T, the control of the machining depth will be explained in more detail. In other words, during pulsed laser oscillation
The laser beam _{3 is emitted only when the pulse sound PO 1 is} received within the gate width (set time) △T delayed by △T 1 from t ₀ , and when it deviates from the gate width △T, the laser power control circuit 7 CW oscillator 1'
The excitation of the laser beam 3 is interrupted and the irradiation of the laser beam 3 is stopped.

In FIG. 1, L ₁ indicates the distance from the laser oscillator 1 to the workpiece 2, and L ₂ indicates the distance from the laser beam irradiation point to the microphone 4. Now, if the machining depth is L, and the speed of light and the speed of sound are C and Va, respectively, the following relational expression holds true.

△t=(L ₁ +L)/C+(L ₂ +L)/Va...(
(Equation 1) Considering that the speed of light C in (Equation 1) is very high, the machining depth L is determined by the following relational expression.

L≒△tVa−L ₂ (Equation 2) That is, as described above, the machining depth can be determined by knowing the delay time △t. For example, L ₁ =
Assuming L ₂ = 10 cm and L = 1 mm, △t = △t ₁ + △t ₂ (shown in Figure 2 2) ≒0.3×10 ^-9 _sec +3.4×10 ^-4 cec ≒3.4×10 ^-4 sec This shows that when the machining depth L changes by 1 mm, Δt changes by 3×10 ⁻⁶ sec.

Note that, as is clear from the above equation (2), the machining depth ΔL is controlled to be ΔL=Va×Δt. Naturally, △ of the gate output G shown in Fig. 2
By making T ₁ and ΔT variable and adjusting them, the machining depth can be controlled.

The present invention can be modified in various ways other than the embodiments described above. For example, when oscillating a laser beam, the pulsed laser beam is divided into two parts, and one side is irradiated onto the non-processed area (flat area) and the other side is irradiated onto the processing point, so that the sound from the flat area and the sound from the processed area are separated. A method using time differences is also possible.

Furthermore, even in the method of oscillating pulsed laser light, when outputting laser light as shown in Fig. 2 1, the configuration shown in Fig. 1 is CW within one oscillator.
Although the oscillation section is provided with a pulse oscillation section, for example, two laser light sources may be used and the beams (light rays) may be mixed. Alternatively, it is also possible to use only the CW oscillation section without using the pulsed laser oscillation section, and to transform the CW oscillation section into a pulsed form using a cutter or the like and irradiate the workpiece with the CW oscillation section.

A carbon laser or the like is used as the CW oscillation section, and an argon laser or the like is used as the pulsed oscillation section, but there are no restrictions on the type of these laser oscillation sections. The method of installing the microphone as a means for receiving acoustic signals from the workpiece is also not limited to the illustrated example. In reality, the laser oscillator is installed inside or attached to a processing machine frame (not shown), and an acoustic receiving means such as a microphone is also attached to the processing machine frame.

As described in detail above, the laser processing device of the present invention can determine the processing depth with extremely high accuracy, and at the same time, it is possible to control the processing depth, and therefore, especially in the case of a laser knife, excessive A highly safe laser scalpel that can prevent cuts (processing) can be obtained. In other words, since the acoustic signal is received from the processing point of the workpiece, there is no error caused by measuring the depth of nearby parts, which is likely to occur when measuring the depth of a minute part optically, and it is accurate. Highly reliable machining can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing the basic configuration of the present invention, and FIG. 2 is a diagram showing the operation principle. 1... Laser oscillator, 1'... Continuous wave (CW) laser oscillation section, 1''... Pulse laser oscillation section, 2... Workpiece, 3... Laser light, 3'... Pulse sound , 4...Microphone, 5...Time delay measurement circuit, 6...Pulsed laser power supply, 7...Laser power supply control circuit, 8...
...Continuous wave laser power supply, R...Laser output, P
...Pulse sound output, G...Gate output, △t...
...delay time.

Claims (1)

[Claims] 1. A processing device that performs processing by irradiating a workpiece with a laser beam, which includes a laser oscillation means that oscillates a processing laser beam containing a continuous wave component and a pulsed component, and a processing device that processes a workpiece by irradiating the workpiece with a continuous wave component and a pulsed component. acoustic receiving means for receiving pulsed sound generated from the irradiation point; means for measuring elapsed time from the time of oscillation of the pulse component to the time of reception of the pulsed sound; and based on the time value measured by the measuring means. and excitation control means for controlling excitation of the laser oscillation means.