Patent Description:
In the above technical field, patent literature <NUM> discloses a technique of detecting the tilt of a process surface by using a measurement device provided outside an optical processing head.

Patent literature <NUM>: Canadian Patent Application Publication No. <CIT>
Prior art which is related to this field of technology can be found e.g. in <CIT> disclosing a processing head for a laser processing apparatus, in <CIT> disclosing a laser machining head with focus control, in <CIT> disclosing a laser minute processing device, in <CIT> disclosing a laser beam irradiation device, in <CIT> disclosing a control system for depositing powder to a molten puddle, and in <CIT> disclosing a method for processing the surface of a workpiece using heat. Further cited prior art documents are <CIT> showing a method of verifying seam quality during a laser welding process and <CIT> showing a laser cladding apparatus and method.

In the technique described in this literature, however, the measurement device includes an inspection optical system completely independent of an optical system that guides a ray for processing to a process surface. Thus, independent adjustment needs to be performed for the measurement device.

The present invention enables to provide a technique of solving the above-described problem.

Aspects of the present invention provide an optical processing head, an optical processing apparatus, a control method of an optical processing apparatus, and a control program of an optical processing apparatus according to the respective claims.

According to the present invention, the state of a process surface can be easily inspected in optical processing.

A preferred embodiment(s) of the present invention will now be described in detail with reference to the drawings. It should be noted that the relative arrangement of the components, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise. In the following embodiments, "light" includes various electromagnetic waves ranging from ultraviolet light to a microwave, and can be properly selected in accordance with a processing target or the like.

An optical processing head <NUM> according to the first embodiment of the present invention will be described with reference to <FIG>. The optical processing head <NUM> includes a light guide portion <NUM> and an inspection portion <NUM>.

The light guide portion <NUM> guides a ray <NUM> for processing and a ray <NUM> for inspection to a process surface <NUM>. The ray <NUM> for inspection and the ray <NUM> for processing are rays having different wavelengths.

The inspection portion <NUM> inspects the state of the process surface <NUM> from reflected light <NUM> of the ray <NUM> for inspection reflected by the process surface <NUM>.

With the above-described arrangement, the state of a process surface such as the tilt of the process surface or the concentration of a processing material on the process surface can be easily inspected in optical processing. Since the ray <NUM> for processing and the ray <NUM> for inspection have different wavelengths, these rays do not interfere with each other in the light guide portion <NUM>. This arrangement also has an advantage in which these rays can be superimposed on each other and the light guide portion <NUM> can be downsized. Further, the reflected light <NUM> of the ray <NUM> for inspection can be separated from reflected light of the ray <NUM> for processing. That is, the inspection portion <NUM> can separate and receive only the reflected light <NUM>, and noise generated by the ray <NUM> for processing can be reduced.

An optical processing head <NUM> according to the second embodiment of the present invention will be described with reference to <FIG> is a view showing the internal arrangement of the optical processing head <NUM> to which a laser beam is applied. As shown in <FIG>, the optical processing head <NUM> includes a condensing optical system device <NUM> functioning as a light guide portion, an inspection unit <NUM> functioning as an inspection portion, and a nozzle <NUM>.

The condensing optical system device <NUM> includes a collimator lens <NUM>, a condenser lens <NUM>, a cover glass <NUM> that covers the condenser lens <NUM>, and a housing <NUM> that holds these lenses. The collimator lens <NUM> converts, into parallel light, a ray <NUM> for processing that travels from an incident end <NUM>. The condenser lens <NUM> condenses the parallel light toward a process surface <NUM> on the downstream side.

With these optical systems, the condensing optical system device <NUM> can guide, to the process surface <NUM>, the ray <NUM> for processing that has been emitted by a light source (not shown), has passed through a light transmitting portion <NUM>, and has been guided from the incident end <NUM>. The light transmitting portion <NUM> is, for example, an optical fiber having a core diameter of φ0. <NUM> to <NUM>, and guides light (for example, a laser beam) generated by the light source to the optical processing head <NUM>.

The optical processing head <NUM> condenses, on the process surface <NUM>, the ray <NUM> for processing that has entered the optical processing head <NUM> from the incident end <NUM>, heats the process surface <NUM>, and forms a molten pool <NUM> on the process surface <NUM>.

The nozzle <NUM> has a ray path that does not cut off the ray <NUM> for processing. The nozzle <NUM> receives supply of a powder material and gas from a material supply device (not shown) through a material supply portion, and ejects a processing material <NUM> mixed in the gas to the molten pool <NUM> of the process surface <NUM>. After that, the molten pool <NUM> is cooled to deposit the material on the process surface <NUM>. The molten pool <NUM> is moved on the process surface <NUM>, and melting, material supply, and cooling are repeated, implementing three-dimensional shaping.

The inspection unit <NUM> is a unit for observing the status of the process surface <NUM> and its vicinity from a viewpoint along the optical axis of the ray <NUM> for processing. The inspection unit <NUM> is arranged upstream of the condenser lens <NUM> and downstream of the collimator lens <NUM>.

The inspection unit <NUM> includes an image capturing device <NUM> that captures a spot image of reflected light <NUM> of a ray <NUM> for inspection. Further, the inspection unit <NUM> includes a comparator <NUM> that compares the spot image of the ray <NUM> for inspection with a reference spot image. The inspection unit <NUM> further includes one-way mirrors <NUM> and <NUM> provided inside the housing <NUM>, and a ray emitter <NUM> for inspection.

The image capturing device <NUM> is arranged off the ray <NUM> for processing. The inspection unit <NUM> includes the one-way mirror <NUM> that transmits the ray <NUM> for processing and guides, to the image capturing device <NUM>, the reflected light <NUM> of the ray <NUM> for inspection reflected by the process surface <NUM>.

The ray emitter <NUM> for inspection is arranged off the ray <NUM> for processing. The ray emitter <NUM> for inspection may be a light source for inspection, but is not limited to this and may be the exit port of a light transmitting portion such as an optical fiber.

The one-way mirror <NUM> is coated to transmit the ray <NUM> for processing (wavelength of <NUM>,<NUM> or more) and reflect part of the ray <NUM> for inspection (wavelength of <NUM> to <NUM>) by the downstream surface of the one-way mirror <NUM>. The reflected light <NUM> reflected by the process surface <NUM> is reflected by the one-way mirror <NUM>, and guided to the image capturing device <NUM>. Feedback control of processing parameters is performed in accordance with the observed processing status, and the processing accuracy can be improved. The one-way mirror <NUM> transmits the ray <NUM> for processing and guides, to the process surface <NUM>, the ray <NUM> for inspection emitted by the ray emitter <NUM> for inspection.

The ray emitter <NUM> for inspection and the image capturing device <NUM> are arranged off the ray <NUM> for processing. The ray emitter <NUM> for inspection is, for example, an LED, and the wavelength of the ray <NUM> for inspection is <NUM> to <NUM>. However, the ray emitter <NUM> for inspection is not limited to this, and may be a halogen lamp, an incandescent lamp, a krypton lamp, or the like as long as it can emit the ray <NUM> for inspection having a wavelength (for example, a wavelength of <NUM> to <NUM>) different from the wavelength (for example, a wavelength of <NUM>,<NUM>) of the ray <NUM> for processing. The image capturing device <NUM> includes a lens 221a, and an image sensor 221b such as a CCD or CMOS sensor. A ray that has reached the lens 221a is condensed to each pixel of the image sensor 221b.

The temperature of the process surface <NUM> is raised to be high during processing. At this time, thermal radiation is generated from the process surface <NUM>. The wavelength spectrum of this thermal radiation complies with a Planck distribution shown in <FIG>. For example, <FIG> shows spectra <NUM> and <NUM> each indicating the relationship between the wavelength and the intensity when the temperature at the process point is <NUM>,<NUM> or <NUM>,<NUM>.

The thermal radiation from the process surface <NUM> and the ray <NUM> for inspection simultaneously enter the image sensor. If the wavelength of the thermal radiation is equal or close to that of the ray <NUM> for inspection, the thermal radiation becomes noise in the image sensor. To prevent this, the wavelength of the ray <NUM> for inspection is preferably set to be different from that of the thermal radiation. This has an effect capable of reducing noise.

Letting c be the light velocity, h be the Planck constant, and κ be the Boltzmann constant with respect to a maximum temperature T assumed on the process surface <NUM>, the relation between a wavelength λ and luminance I of the ray <NUM> for inspection is given by: <MAT> More specifically, the ray <NUM> for inspection has a wavelength of <NUM> or less, and is preferably ultraviolet light or blue light having a wavelength of <NUM> or less.

Typical examples of a metal powder are iron and SUS (Steel Use Stainless), and their melting point is about <NUM>,<NUM>. In <FIG>, the peak wavelength of the thermal radiation spectrum when the process point is at <NUM>,<NUM> is about <NUM>. If the wavelength is set to be equal to or smaller than <NUM> which is smaller than this peak wavelength, the radiation intensity abruptly decreases. In contrast, the radiation intensity gradually decreases at a wavelength larger than the peak wavelength. For this reason, noise generated by the thermal radiation can be efficiently reduced by setting the wavelength of the ray <NUM> for inspection to be equal to or smaller than <NUM>.

When the ray <NUM> for inspection having a wavelength of <NUM> or more is employed, Rayleigh scattering becomes main scattering in a processing material as small as about several µm. Since the scattering becomes weak in reverse proportion to the fourth power of the wavelength, the concentration of the processing material may not be inspected at high accuracy. Therefore, this embodiment implements high-accuracy inspection of the concentration of a processing material by setting the wavelength of the ray <NUM> for inspection to be equal to or smaller than <NUM> so that the processing material is scattered strongly by Mie scattering even when the processing material is a powder as small as about several µm.

The comparator <NUM> compares a reference spot image with the spot image of the ray <NUM> for inspection. When a process surface perpendicular to the optical axis of the ray <NUM> for processing is set as a reference process surface and the processing material <NUM> is not ejected, the spot image of the reflected light <NUM> of the ray <NUM> for inspection reflected by this reference process surface is set as a reference spot image.

Based on the distance between a spot center included in the spot image of the ray <NUM> for inspection and a reference spot center included in the reference spot image, the comparator <NUM> calculates the tilt angle of the process surface <NUM> with respect to the reference process surface. Also, the comparator <NUM> calculates the concentration of the processing material <NUM> on the process surface <NUM> from the difference in size between the spot image of the ray for inspection and the reference spot image. The optical processing head <NUM> further includes an adjuster <NUM> that adjusts the ejection amount of the processing material <NUM> based on the concentration of the processing material <NUM> on the process surface <NUM>.

<FIG> is a view showing the result of calculating an image captured by the image capturing device <NUM> by a ray tracing simulation.

An image as the result of capturing an image of the reflected light <NUM> by the image capturing device <NUM> will be called a ray spot image for inspection. The spot diameter of the ray spot image for inspection is set to be, for example, a full width at half maximum with reference to the peak position of the spot.

When no powder material is ejected to the process surface <NUM> and the process surface is perpendicular to the optical axis of the ray for processing, a reference spot image <NUM> is output. To the contrary, when a powder material is ejected to the process surface <NUM> and the powder exists densely near the process surface <NUM>, the ray spot for inspection becomes larger than the reference spot, as in a ray spot image <NUM> for inspection.

If the powder convergence is high, the concentration of the powder present in the powder convergent region becomes high, and the reflected light <NUM> of the ray <NUM> for inspection is scattered by the powder. That is, as the powder convergence is higher, the count at which the ray for inspection is scattered by the powder becomes higher. As the scattering count is higher, the ray spot for inspection received by the image sensor becomes wider. It can be said that the powder convergence is higher as the difference of the ray spot diameter for inspection from the reference spot diameter is larger. From this, the diameter of the ray spot for inspection is measured and compared with the diameter of the reference spot, thereby calculating the powder convergence. The powder convergence is quantified by the powder concentration on the process surface <NUM>.

When no powder material is ejected to the process surface <NUM> and the process surface <NUM> tilts, the position of the ray spot for inspection shifts from the reference spot, as in a ray spot image <NUM> for inspection. Letting d be the distance of this shift on the screen, a tilt θ of the process surface <NUM> can be given using a distance f between the lens 221a and the image sensor 221b: <MAT>.

When the powder material is ejected and the process surface <NUM> tilts, the position of the ray spot for inspection shifts from the reference spot, and the ray spot for inspection becomes larger than the reference spot, as in a ray spot image <NUM> for inspection.

A plane perpendicular to the optical axis is defined as the reference of the tilt of the process surface <NUM>. As the tilt of the process surface <NUM> is larger, the distance d between the peak position of the ray spot for inspection and the peak position of the reference spot becomes larger. From this, the powder convergence and the tilt angle θ of the process surface can be calculated.

Whether the powder concentration on the process surface is proper can be determined from information of the powder convergence. When the powder concentration does not have a desired value, it can be adjusted by increasing/decreasing the powder supply amount.

In general, the tilt angle θ is desirably <NUM>°. At this time, the optical axis of the ray <NUM> for processing and the process surface <NUM> are perpendicular to each other. When the optical axis of the ray <NUM> for processing and the process surface <NUM> are perpendicular to each other, the Fresnel reflection of the ray <NUM> for processing by the process surface <NUM> is minimized, and the light use efficiency is maximized. Hence, when the optical axis of the ray <NUM> for processing or the process surface <NUM> is adjusted to always keep the tilt angle to be <NUM>, the light use efficiency can always be maximized. The tilt angle θ can be maintained at <NUM>° regardless of the processing status by, for example, controlling a stage supporting the process surface <NUM> or controlling the tilt of the optical processing head <NUM>.

When the reflectance of the ray for processing on the process surface <NUM> is high (for example, a copper plate), reflected light of the ray for processing returns to the light source for processing and may damage the light source for processing. In this case, it is also important to set the tilt angle θ to be a value other than <NUM>° so that the ray for processing does not directly return to the light source for processing. That is, the damage to the light source for processing can be suppressed by setting the tilt angle θ to be a value other than <NUM>.

<FIG> is a view for explaining the optical axis shift of the ray <NUM> for processing by the one-way mirrors <NUM> and <NUM>. As shown in <FIG>, the reflecting surface of the one-way mirror <NUM> and that of the one-way mirror <NUM> are symmetrical about a plane <NUM> perpendicular to an optical axis <NUM> of the ray <NUM> for processing. That is, tilt angles α of the reflecting surfaces of the one-way mirrors <NUM> and <NUM> with respect to the axis of the ray <NUM> for processing are equal to each other. Shifts of the ray <NUM> for processing from the optical axis by the one-way mirrors <NUM> and <NUM> cancel each other. This has an effect in which shift correction of the optical axis <NUM> of the ray <NUM> for processing becomes unnecessary.

<FIG> is a flowchart showing the sequence of processing to be performed by the inspection unit <NUM>. First, in step S601, the image capturing device <NUM> captures an image of a ray spot for inspection. Then, in step S602, a reference spot image is read out from a database (not shown). Here, a reference minimum spot image and a reference maximum spot image are read out as the reference spot image. The reference minimum spot image is a reference spot image having a minimum spot diameter. The reference maximum spot image is a reference spot image having a maximum spot diameter. For example, the reference minimum spot image is a reference spot image reflected by the reference process surface perpendicular to the optical axis of the ray <NUM> for processing when the processing material <NUM> is not ejected. In contrast, the reference maximum spot image is a reference spot image reflected by the reference process surface when the processing material <NUM> is ejected in a maximum amount.

In step S603, the comparator <NUM> compares the ray spot diameter for inspection with the reference minimum spot diameter. If the ray spot diameter for inspection is smaller, the process advances to step S604, and the adjuster <NUM> increases the supply amount of the material by the nozzle <NUM>.

In step S605, the comparator <NUM> compares the ray spot diameter for inspection with the reference maximum spot diameter. If the ray spot diameter for inspection is larger, the process advances to step S606, and the adjuster <NUM> decreases the supply amount of the material by the nozzle <NUM>.

Further, the process advances to step S607, and the comparator <NUM> determines whether the shift d between the center of the ray spot for inspection and the center of the reference spot is equal to or smaller than a reference value D. If the shift d exceeds the reference value D, the process advances to step S608 to adjust the tilt of the stage (not shown) (or the optical processing head).

As described above, according to the second embodiment, the state of a process surface such as the tilt of the process surface or the concentration of a processing material in gas on the process surface can be easily inspected by a simple arrangement. The optical processing head can be controlled in accordance with the state of the process surface.

An optical processing head according to the third embodiment of the present invention will be described with reference to <FIG> is a view for explaining the arrangement of an optical processing head <NUM> according to this embodiment. In the optical processing head <NUM> according to the third embodiment, unlike the second embodiment, an inspection unit <NUM> includes a one-way mirror <NUM> and a ray emitter <NUM> for inspection. Unlike the one-way mirror <NUM>, the one-way mirror <NUM> is attached with the same tilt as that of a one-way mirror <NUM>. In accordance with this, the ray emitter <NUM> for inspection is provided on the side of an image capturing device <NUM>. The remaining arrangement and operation are the same as those in the second embodiment, so the same reference numerals denote the same arrangement and operation and a detailed description thereof will not be repeated.

According to the third embodiment, since the ray emitter <NUM> for inspection and the image capturing device <NUM> can be provided on the same side of the optical processing head <NUM>, the same effect as that of the second embodiment can be obtained by a more compact arrangement. However, a contrivance to cope with the shift of the optical axis as described with reference to <FIG> (for example, a condenser lens <NUM> is arranged with a shift) is necessary.

An optical processing head according to the fourth embodiment of the present invention will be described with reference to <FIG> is a view for explaining the arrangement of an optical processing head <NUM> according to this embodiment. In the optical processing head <NUM> according to the fourth embodiment, unlike the second embodiment, an inspection unit <NUM> includes a flat transmission plate <NUM> instead of the one-way mirror <NUM>, and a ray emitter <NUM> for inspection is arranged near an image capturing device <NUM>. The remaining arrangement and operation are the same as those in the second embodiment, so the same reference numerals denote the same arrangement and operation and a detailed description thereof will not be repeated.

A one-way mirror <NUM> and the transmission plate <NUM> are symmetrical about a plane perpendicular to the optical axis of a ray <NUM> for processing. That is, the tilt angles of the one-way mirror <NUM> and transmission plate <NUM> with respect to the axis of a ray <NUM> for processing are equal to each other. The shift of the optical axis of the ray <NUM> for processing by the one-way mirror <NUM> can be canceled by refraction by the transmission plate <NUM>.

According to the fourth embodiment, the same effect as that of the second embodiment can be obtained by a more compact arrangement. Further, there is an effect in which shift correction of the optical axis of the ray <NUM> for processing becomes unnecessary.

An optical processing apparatus <NUM> according to the fifth embodiment of the present invention will be described with reference to <FIG>. The optical processing apparatus <NUM> is an apparatus that includes one of the optical processing heads <NUM>, <NUM>, <NUM>, and <NUM> explained in the above-described embodiments, and generates a three-dimensional shaped object (or overlay welding) by melting a material by heat generated by condensed light. Here, the optical processing apparatus <NUM> including an optical processing head <NUM> will be explained as an example.

In addition to the optical processing head <NUM>, the optical processing apparatus <NUM> includes a light source <NUM>, a light transmitting portion <NUM>, a coolant supply device <NUM>, a coolant supply portion <NUM>, a stage <NUM>, a gas supply device <NUM>, a gas supply portion <NUM>, a material supply device <NUM>, a material supply portion <NUM>, and a controller <NUM>.

The light source <NUM> can be a laser, an LED, a halogen lamp, a xenon lamp, an incandescent lamp, or the like. The wavelength of a ray is, for example, <NUM>,<NUM>, but is not limited to this.

The coolant supply device <NUM> stores, for example, water as a coolant, and supplies the coolant by a pump to the optical processing head <NUM> via the coolant supply portion <NUM>. The coolant supply portion <NUM> is a resin or metal hose having an inner diameter of φ2 to <NUM>. The coolant is supplied into the optical processing head <NUM>, circulated inside it, and returned to the coolant supply device <NUM>, thereby suppressing the temperature rise of the optical processing head <NUM>. The coolant supply amount is, for example, <NUM> to <NUM>/min.

The stage <NUM> is, for example, an X stage, an X-Y stage, or an X-Y-Z stage, and can operate the respective axes (X, Y, and Z).

The gas supply device <NUM> supplies a purge gas to the optical processing head <NUM> through the gas supply portion <NUM>. The purge gas is, for example, nitrogen, argon, or helium. However, the purge gas is not limited to this and may also be another gas as long as the purge gas is an inert gas. The purge gas supplied to the optical processing head <NUM> is ejected from a nozzle <NUM> along the above-described ray.

The material supply device <NUM> supplies a material to the nozzle <NUM> via the material supply portion <NUM>. Examples of the material are a metal particle, a resin particle, a metal wire, and a resin wire. The material supply device <NUM> can simultaneously supply even a carrier gas. The material supply portion <NUM> is, for example, a resin or metal hose, and guides, to the nozzle <NUM>, a powder flow prepared by mixing a material in a carrier gas. However, when the material is a wire, no carrier gas is necessary.

Although not shown, the optical processing apparatus <NUM> includes an orientation control mechanism and position control mechanism that control the orientation and position of the optical processing head <NUM>.

Next, the operation of the optical processing apparatus <NUM> will be explained. A shaped object <NUM> is created on the stage <NUM>. The purge gas is ejected from the nozzle <NUM> to a process surface <NUM>. Thus, the peripheral environment of the molten pool is purged by the purge gas. By selecting an oxygen-free inert gas as the purge gas, oxidization of the process surface <NUM> can be prevented.

The optical processing head <NUM> is cooled by the coolant supplied from the coolant supply device <NUM> through the coolant supply portion <NUM>, suppressing the temperature rise during processing.

By scanning the optical processing head <NUM> along the process surface <NUM> at the same time as the above-described series of operations, desired shaping can be performed while depositing the material. That is, this apparatus can implement overlay welding or three-dimensional shaping.

The controller <NUM> acquires the status of the process surface <NUM> from an inspection unit <NUM>, controls the material supply device <NUM> in accordance with this status, and changes the amount of a processing material to be ejected to the process surface <NUM>. Also, the controller <NUM> acquires the status of the process surface <NUM> from the inspection unit <NUM>, controls the stage <NUM> in accordance with this status, and changes the tilt of the process surface <NUM> so that the process surface <NUM> and the optical processing head <NUM> are located at predetermined relative positions.

As described above, according to the fifth embodiment, higher-accuracy optical processing can be implemented by easily inspecting the status of a process surface and setting processing conditions suited to the status.

Claim 1:
An optical processing head comprising:
a light guide portion (<NUM>, <NUM>) that guides, to a process surface, a ray for processing (<NUM>, <NUM>) and a ray for inspection (<NUM>, <NUM>) different in wavelength from the ray for processing; and
an inspection portion (<NUM>, <NUM>) that inspects a state of the process surface from reflected light of the ray for inspection reflected by the process surface;
a nozzle (<NUM>) that ejects a processing material toward a molten pool formed on the process surface by the ray for processing,
characterized in that
said inspection portion (<NUM>) includes an image capturing unit (<NUM>) that captures a spot image of the ray for inspection and a comparator (<NUM>) that compares the spot image of the ray for inspection with a reference spot image,
the comparator calculates a tilt angle of the process surface (<NUM>) with respect to the reference process surface, based on a distance between a spot center included in the spot image of the ray for inspection and a reference spot center included in the reference spot image,
the reference spot image is an image obtained by capturing an image of the ray for inspection reflected by a reference process surface perpendicular to an optical axis of the ray for processing, and
the state of the process surface comprises a tilt of the process surface.