JP2021146395A - Laser unit and laser marker device - Google Patents

Abstract

To provide a multi-beam laser marker which imparts a uniform field depth expanding effect to each ray of light.SOLUTION: A laser unit has a laser light source in which a plurality of light-emitting parts for emitting a laser beam are arranged, an imaging lens system for condensing of the laser beam, and an imaging position change element for changing imaging positions of the plurality of laser beams in the optical axis direction so that the imaging positions are different on the optical axis of the imaging lens system. In the imaging position change element, the imaging positions are different depending on an incident position in a vertical position to the optical axis direction.SELECTED DRAWING: Figure 2

Description

The present invention relates to a laser unit and a laser marker device.

There is known a laser marker device that collects laser light on a recording medium such as thermal paper and develops color by applying thermal energy to an object.
In the laser marker device, the beam diameter at the imaging position (condensing point) of the laser light corresponds to the printable dot diameter, and the range in which sufficient thermal energy can be applied to the recording medium while maintaining the dot diameter is It is defined as a predetermined printable depth. That is, in the laser marker device, the height of the object to be printed needs to be within a certain range (within the print depth) due to the influence of the printable depth. Therefore, there is a demand for a laser marker that is robust to the printing position to some extent so that printing can be performed even if the printing target flutters due to vibration or the thickness of the printing target varies.

Examples of such a depth enlargement technique include a lens diffuser and a soft focus lens. However, such depth expansion technology is generally assumed to be a single beam.
Further, as another depth enlargement technique, a technique using a phase type optical element is also known (for example, Patent Document 1), but when a multi-beam having a concentric shape of the optical element and a high image height is incident, There is a concern that different refractions will be given to each image height, causing aberrations.

In order to solve such a problem, in the laser unit according to the present invention, a laser light source in which a plurality of light emitting units for emitting laser light are arranged, an imaging lens system for condensing the laser light, and a plurality of imaging lens systems are used. It has an imaging position changing element that changes the imaging position of the laser beam in the optical axis direction so as to be different on the optical axis of the imaging lens system, and the imaging position changing element is the light. The imaging position is different depending on the incident position in the vertical direction with respect to the axial direction.

According to the present invention, in a multi-beam laser marker using a common optical system, it is possible to uniformly give the effect of depth expansion to each light beam.

It is a figure which shows the schematic structure of one form of the take-up transfer apparatus provided with the laser marker apparatus which concerns on this invention. It is a figure which shows the structure of the take-up transfer apparatus provided with the laser marker apparatus which concerns on this invention. It is a figure which shows the structure of the laser marker apparatus which concerns on this invention. It is a figure which shows an example of the structure of the laser head shown in FIG. 3 seen from the Y direction. It is a figure which shows an example of the structure of the laser head shown in FIG. 3 seen from the X direction. It is a figure which shows an example of the structure of the stepped prism which concerns on this invention. It is a figure which shows an example of the effect of the stepped prism which concerns on this invention. It is a figure which shows the difference of the output result between the laser marker apparatus which concerns on this invention, and a comparative example. It is a figure which shows an example of the control of the laser marker apparatus which concerns on this invention. It is a figure which shows an example of the output at the time of printing of the laser marker apparatus which concerns on this invention. It is a figure which shows an example of the structure using the different refractive index plywood. It is a figure which shows an example of another configuration of the laser marker apparatus shown in FIG. It is a figure which shows an example of another configuration of the laser marker apparatus shown in FIG. It is a figure which shows another example of the structure of the stepped prism which concerns on this invention.

Hereinafter, embodiments according to the present invention will be sequentially described with reference to the drawings. In the embodiment, the same functions and the same configurations are designated by the same reference numerals, and duplicate description will be omitted as appropriate. Drawings may be partially omitted or simplified to aid understanding of some configurations.

The printing device 100, which is a laser marker device according to the present invention, comprises a device main body 30 constituting a laser unit, a laser head 20 for emitting laser light, a sheet S, which is a thermal paper as a recording medium, and a sheet S. It has a transport unit 10 for transporting.
The printing device 100 in the present embodiment functions as a laser marker device that prints by heat energy by irradiating the surface of the sheet S with a laser beam, but the printing device 100 is not limited to letters, and is not limited to letters, symbols, and lines. , A graphic, a solid image, or a combination thereof, a bar code, a two-dimensional code, or the like may be printed.

The sheet S is an object to be printed in the present embodiment, and may be any material other than thermal paper, which absorbs light and converts it into heat to cause changes in hue, reflectance, etc., for example, engraving on metal. Etc. are also included. Further, the sheet S is not limited to the sheet shape, and may take various shapes.
As the "material that causes changes in hue, reflectance, etc. due to heat" constituting the sheet S, for example, a combination of an electron-donating dye precursor and an electron-accepting color developer used in conventional thermal paper is used. Can be used. In addition, as a material that causes a change in hue, reflectance, etc. due to heat, a material that causes a change such as a combined reaction of heat and light, for example, a discoloration reaction due to solid phase polymerization due to heating of a diacetylene compound and irradiation with ultraviolet light is also available. included.

In the present embodiment, as shown in FIG. 1, the transport unit 10 is wound with a sheet S, and is rotated in a predetermined direction to send out the sheet S, and a feeding roller 11 and a sheet S. It is a transport means including a take-up roller 12 for taking up a wind-up roller 12.
Further, an encoder 49, which is a detection means for detecting the speed of the sheet S, is provided on the transport path of the sheet S of the transport unit 10, and the transport speed of the sheet S and the writing speed of the laser head 20 are provided. Controls to match with.

A laser head 20 is attached on the moving path of the sheet S in the printing device 100, and irradiates the sheet S with a laser beam.
The length of the sheet S in the present embodiment in the width direction orthogonal to the feeding direction of the sheet S is wider than the irradiable width of the laser head 20.
Therefore, the printing width is secured by mounting a plurality of laser heads 20 at positions that do not overlap each other, but the present invention is not limited to this, and a single laser head 20 may be used. As described above, even when the printing range is wider than the irradiation range of the laser head 20, a sufficient printing width can be secured by providing the plurality of laser heads 20.

An image information output unit 47 such as a personal computer that outputs image information, a cooling device 50, and an encoder 49 are connected to the device main unit 30.
The device main body 30 and the laser head 20 are connected by a single or a plurality of optical fibers 42, and the laser light oscillated by the device main body 30 passes through the optical fiber 42 and the laser head 20 as described later. Is irradiated to the sheet S.
In this way, the printing device 100 irradiates the sheet S, which is a recording medium, with the laser light emitted from the laser emitting element 41 via the optical fiber 42 and the laser head 20, and records an image (visible image) composed of drawing units. ..

As shown in FIG. 2, for example, the apparatus main body 30 includes a laser emitting element 41, a drive driver 45, a controller 46, and a power supply unit 48 for supplying electric power to the laser emitting element 41. There is.
The apparatus main body portion 30 also has a laser irradiation apparatus 14 having a laser array portion 14a and a fiber array portion 14b. In the present embodiment, the laser irradiation device 14 is a fiber in which the end faces of the plurality of optical fibers 42 on the exit side are arranged in an array in the Z-axis direction orthogonal to the X-axis direction, which is the movement direction of the sheet S as the recording object. It is an array.
In the present embodiment, the apparatus main body 30 that controls to emit such laser light and the laser head 20 that controls to emit the laser light toward the sheet S function as one "laser unit". do.

A power supply unit 48 and an image information output unit 47 are connected to the controller 46.
The controller 46 is a light emission control unit that generates a pattern for emitting light from the laser light emitting element 41 based on the image information output from the image information output unit 47 and outputs it as a signal.

The laser emitting element 41 can be appropriately selected depending on the intended purpose, and for example, a semiconductor laser, a solid-state laser, a dye laser, or the like can be used. Among these, the laser light emitting element 41 is preferably a semiconductor laser from the viewpoints of wide wavelength selectivity, small size, so that the device can be miniaturized, and low price.

The wavelength of the laser light emitted by the laser light emitting element 41 is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 700 nm to 2000 nm, more preferably 780 nm to 1600 nm.

In the laser emitting element 41 which is an emitting means, not all of the applied energy is converted into laser light. Normally, in the laser light emitting element 41, energy that is not converted into laser light is converted into heat to generate heat. Therefore, the laser emitting element 41 is cooled by the cooling device 50 which is a cooling means.
Further, in the laser irradiation device 14 of the present embodiment, by using the fiber array unit 14b, it is possible to arrange the laser emitting elements 41 apart from each other. As a result, the influence of heat from the adjacent laser emitting element 41 can be reduced, and the laser emitting element 41 can be cooled efficiently, so that the temperature rise and variation of the laser emitting element 41 can be avoided. It is possible to reduce the output variation of the laser beam, and to improve density unevenness and whiteout.
The output of the laser beam is the average output measured by the power meter. There are two types of laser light output control methods, one is to control the peak power and the other is to control the pulse emission ratio (duty: laser emission time / period time).

The cooling device 50 is a liquid cooling system that circulates a cooling liquid to cool the laser emitting element 41, and has a heat receiving unit 51 in which the cooling liquid receives heat from each laser emitting element 41 and a heat radiating unit that dissipates heat from the cooling liquid. It is equipped with 52. The heat receiving unit 51 and the heat radiating unit 52 are connected by cooling pipes 53a and 53b. The heat receiving portion 51 is provided with a cooling tube for flowing the cooling liquid formed of the good thermal conductive member inside the case formed of the good thermal conductive member. The plurality of laser light emitting elements 41 are arranged in an array on the heat receiving unit 51.

The heat radiating unit 52 includes a radiator and a pump for circulating the coolant. The coolant sent out by the pump of the heat radiating unit 52 flows into the heat receiving unit 51 through the cooling pipe 53a. Then, the coolant takes the heat of the laser emitting elements 41 arranged in the heat receiving unit 51 while moving the cooling tube in the heat receiving unit 51, and cools the laser emitting element 41. The cooling liquid that has taken the heat of the laser light emitting element 41 flowing out from the heat receiving unit 51 and whose temperature has risen moves in the cooling pipe 53b, flows into the radiator of the heat radiating unit 52, and is cooled by the radiator. The coolant cooled by the radiator is pumped again to the heat receiving unit 51.

The fiber array portion 14b forms an array in the vertical direction (Z-axis direction) of a plurality of optical fibers 42 provided corresponding to the laser light emitting element 41 and the vicinity of the end portion of the optical fiber 42 serving as the laser emitting portion. It includes an array head 44 for holding.
Further, each laser incident portion of the optical fiber 42 is attached to the laser emitting surface of the corresponding laser emitting element 41.

If one array head 44 tries to hold all the optical fibers 42, the array head 44 becomes long and easily deformed. As a result, it is difficult for one array head 44 to maintain the linearity of the beam arrangement and the uniformity of the beam pitch. Therefore, it is desirable that the array head 44 holds 100 to 200 optical fibers 42. Further, in the laser irradiation device 14, a plurality of array heads 44 holding 100 to 200 optical fibers 42 are arranged side by side in the Z-axis direction, which is a direction orthogonal to the moving direction of the sheet S. preferable. In the present embodiment, 192 optical fibers 42 are arranged side by side in the Y direction on the array head 44.
In the present embodiment, the array heads 44 are optical fiber arrays arranged one-dimensionally in the Y direction, but the arrangement of the optical fibers 42 may be, for example, zigzag, two rows, or two-dimensionally arranged.

FIG. 3 is a diagram illustrating an arrangement state of the laser array. As shown in FIG. 3, the optical fibers 42 in the array head 44 are arranged so that the dot diameters R formed by irradiating the laser beam to develop colors at the focal position focused on the sheet S are continuous. ..

In the present embodiment, the laser head 20 is fixed and used as a non-scanning laser head that does not perform so-called "scanning". However, for convenience, the Y direction, which is the array direction in which the optical fibers 42 are arranged, is set to "Y direction". The "main scanning direction" is defined, and the X direction in which the sheet S moves is defined as the "secondary scanning direction". The main scanning direction and the sub scanning direction are orthogonal to each other.

Since the array head 44 and the sheet S are relatively moved to record an image on the sheet S, the array head 44 may move with respect to the sheet S, and the sheet S may move with respect to the array head 44. You may.

As shown in FIGS. 4 and 5, the laser head 20 includes an imaging lens system 21 for condensing the laser light emitted from the array head 44, and an emitting side, that is, a Z direction side with respect to the imaging lens system 21. It has a stepped prism 22 which is an imaging position changing element arranged in.
Note that FIG. 4 is a view of the laser head 20 viewed from the X direction side, which is the sub-scanning direction, and FIG. 5 is a view of the laser head 20 viewed from the Y direction side, which is also the main scanning direction.
In FIG. 5, laser emitting portions 42a, which are a plurality of light emitting points, are arranged side by side toward the front.

The imaging lens system 21 has a front lens system 21a that converts the laser light of the divergent light emitted from each optical fiber 42 into a parallel light beam, an optical aperture 21b, and a laser beam on the surface of the sheet S that is the irradiation surface of the laser light. It is an optical system composed of an optical component such as a plurality of lenses having a rear lens system 21c for condensing light. 4 and 5 are attached with a main ray diagram of the imaging lens system 21.
In the present embodiment, the front lens system 21a and the rear lens system 21c are formed symmetrically about the image side focal plane (position of the optical diaphragm 21b in FIGS. 4 and 5) of the front lens system 21a.
Further, since the position of the array head 44 on which each end face of the optical fiber 42 is arranged functions as a pseudo light emitting portion that emits laser light as a multi-beam laser light source, the laser emitting portion 42a that is the end face of the optical fiber 42 functions. It corresponds to "a laser light source in which a plurality of light emitting units for emitting laser light are arranged". In the present embodiment, the output waveform of the laser beam in the laser emitting unit 42a is a top hat type laser beam, but the present invention is not limited to this configuration, and light having a Gaussian distribution output waveform may be used.

Both the front lens system 21a and the rear lens system 21c are composed of three meniscus lenses, and the front lens system 21a is a positive th lens with a concave surface facing the object side in order from the object side to the image side. It has a 1 meniscus lens LN1, a positive second meniscus lens LN2 with a convex surface facing the object side, and a negative third meniscus lens LN3 with a concave surface facing the image side.

Similarly, in the rear lens system 21c, the first meniscus lens LN6, the second meniscus lens LN5 with the convex surface facing the image side, and the third meniscus lens LN4 with the concave surface facing the object side are images from the object side. It is arranged on the side in the reverse order of the front lens system 21a.

In the present embodiment, the stepped prism 22 has a function as an imaging position changing element that changes the imaging position of a plurality of laser beams in the Z direction so as to be different on the optical axis O of the imaging lens system 21. It is an optical member.

As shown in FIG. 6, the stepped prism 22 has a structure in which seven flat plate-shaped inorganic optical materials 23 made of BK7 having different sizes are laminated.
Among the inorganic optical materials 23, a plate-shaped member 24 made of synthetic quartz, which is a dust-proof window and functions as a dust-proof portion, is attached to the image side of the inorganic optical material 23, which is arranged on the most + Z side.
As shown in FIG. 5, the stepped prism 22 has different stepped thickness distributions in the X direction, which is vertical to the Y direction, which is the arrangement direction of the array heads 44. The imaging position is changed to a different imaging position for each step incident in the X direction. In other words, the laser beam is divided in the X direction, which is the vertical direction with respect to the optical axis direction of the laser beam, and different imaging positions are given to each of the divided laser beams. That is, the luminous flux emitted from one laser emitting unit 42a is given a plurality of imaging positions depending on the incident position in the X direction and is emitted to the sheet S.
Specifically, as shown schematically in the ray diagram in FIG. 7A, the optical distance of the light transmitted through the inorganic optical material 23 is the refractive index of the inorganic optical material 23: n, 1 of the inorganic optical material 23. When the thickness per sheet is l, the number of the inorganic optical materials 23 passing through changes depending on the incident position in the X direction, so that the optical path length changes by xnl (x = 1,2,3 ..., 7). It becomes.
Due to such a difference in optical path length, as illustrated in FIGS. 7A and 7B, the luminous flux passing through each of the inorganic optical materials 23 in the X direction has an image formation position multifocal on the optical axis O. ..
That is, the heat energy given by irradiating the sheet S with the focused laser light is distributed as shown in FIGS. 8 (a) to 8 (c) in the depth direction of the sheet S, respectively.
In FIGS. 8A to 8C, the light intensity of the laser beam when the stepped prism 22 is provided at the position shown in FIG. 7 is shown by a solid line, and the stepped prism 22 is not provided as a comparative example. The light intensity of the laser beam is shown by a broken line.
Further, in FIGS. 8A to 8C, the imaging position without the stepped prism 22 is def = 0, the position shifted toward the front is def-0.5 mm, and the position shifted toward the back is def. It was set to +0.5 mm. The horizontal axis shows the measurement coordinates when the center of the optical axis O of the laser light is 0, and the vertical axis shows the irradiance of the laser light (W / mm ² ). That is, in FIGS. 8A to 8C, the region where the irradiance above a predetermined value is measured represents the beam diameter of the laser beam.

As is clear from the graphs of FIGS. 8A to 8C, by providing the stepped prism 22, the depth expansion effect can be uniformly given to each light ray in the depth direction of the sheet S. , The distribution of thermal energy is made uniform in the depth direction, and the printable depth is expanded.

Now, the operation when printing is performed on the sheet S by using the printing device 100 having such a configuration will be described.
First, the image information output unit 47 of a personal computer or the like inputs image information to the controller 46. The controller 46 generates a drive signal (control pulse) for driving each drive driver 45 based on the input image information. The controller 46 transmits the generated drive signal (control pulse) to each drive driver 45. Specifically, the controller 46 includes a clock generator.
When the number of clocks oscillated by the clock generator reaches the specified number of clocks, the controller 46 transmits a drive signal (control pulse) for driving each drive driver 45 to each drive driver 45.

When each drive driver 45 receives a drive signal (control pulse), it transmits a current pulse to drive the corresponding laser light emitting element 41. The laser light emitting element 41 outputs a light emitting pulse and irradiates the laser light according to the drive of the drive driver 45. The laser light emitted from the laser light emitting element 41 enters the corresponding optical fiber 42 and is emitted from the laser emitting portion 42a of the optical fiber 42. The laser light emitted from the laser emitting portion 42a of the optical fiber 42 passes through the imaging lens system 21 and then irradiates the surface of the sheet S, which is the recording object, through the stepped prism 22 which is the imaging position changing element. NS. By being heated by the laser beam applied to the surface of the sheet S, an image is recorded on the surface of the sheet S with the spot diameter of the laser beam as the resolution.

FIG. 9 is a diagram illustrating the relationship between the control pulse and the light emission pulse. FIG. 9A shows a timing chart of the control pulse and the emission pulse, and FIG. 9B shows the IL characteristics of the laser. As shown in FIG. 9, the rise of the emission pulse is slightly delayed from that of the current pulse because the laser is not applied with a certain current value in the correlation between the laser output and the IL characteristic of the current value. Is not emitted.

By the way, when a so-called scanning laser marker, which deflects a laser beam by using a galvano mirror and records an image on a recording object, is used as a printing device, an image such as characters is produced by rotating the galvano mirror and driving a driver. With the pulse control of, laser light is irradiated and recorded.
Therefore, when recording a certain amount of information on a recording object, the rotation speed of the galvanometer mirror often limits the writing speed, which causes a problem that high-speed writing is difficult.

On the other hand, the laser head 20 in the present embodiment is a multi-beam laser light source using a laser array in which a plurality of laser emitting portions 42a are arranged in an array.
Therefore, an image can be recorded on the sheet S by ON / OFF control of the laser emitting element 41 corresponding to each pixel. As a result, even if the amount of information is large, the image can be recorded on the sheet S without reducing the transport speed of the sheet S. Therefore, according to the printing apparatus 100 of the present embodiment, even when a large amount of information is recorded on the recording object, the image can be recorded without reducing the productivity.
The transport speed of the sheet S of the transport unit 10 may be appropriately set according to the required speed, but for example, a transport speed of about 10 m / s is sufficient for writing.

By the way, since the laser irradiation device 14 records an image by applying thermal energy to the sheet S at high speed in principle of irradiating the sheet S with laser light to heat the sheet S, when the transfer speed of the transfer unit 10 is increased. Needs to use a high-power laser emitting element 41. Specifically, the number of outputs per laser emitting element 41 is about 10 W / piece, and the amount of heat generated by the laser emitting element 41 is large.
Further, in the present embodiment, 192 laser emitting portions 42a are arranged in an array on the array head 44 at a pitch of 127 μm in order to set the resolution to about 200 dpi. Due to this configuration, high-power laser light is densely packed, so that a large amount of heat is generated.

Therefore, in the laser irradiation device 14, the temperature rise of the laser light emitting element 41 can be further suppressed by providing the cooling device 50 and liquid-cooling the laser light emitting element 41. As a result, according to the laser irradiation device 14, the light emission interval of the laser light emitting element 41 can be further shortened, the transport speed of the sheet S can be increased, and the productivity can be increased. In the cooling device 50 of the present embodiment, the laser emitting element 41 is liquid-cooled, but the laser emitting element 41 may be air-cooled by using a cooling fan or the like. Liquid cooling has a higher cooling efficiency than air cooling, and has the advantage that the laser emitting element 41 can be cooled satisfactorily. On the other hand, air cooling has the advantage that the laser emitting element 41 can be cooled at low cost, although the cooling efficiency is lower than that of liquid cooling.

Here, the state of being printed on the sheet S will be described.

FIG. 10 is a diagram illustrating printing on the sheet S. The case where the sheet S is stationary will be described for the sake of simplification of the description, but the same phenomenon may occur before the sheet S passes through the irradiation range of the laser head 20 in the transportation of the sheet S.
The laser light emitted from the laser emitting element 41 is transmitted as thermal energy to the laser spot position on the surface of the sheet S, in other words, the imaging position by the imaging lens system 21.
As shown in FIG. 10, the thermal energy generally has a Gaussian distribution in which the central portion is high and the edge portion is low.

The sheet S has a color development threshold value, and a portion exceeding the color development threshold value develops color. The color development density is proportional to the magnitude of thermal energy. Further, the color development threshold differs depending on the material of the sheet S.

When the imaging position of the laser beam imaging lens system 21 is set to def = 0, the output of the laser beam is in the Z direction from the imaging position, that is, the sheet, as already described in FIGS. 8A to 8C. The greater the deviation in the thickness direction of S, the greater the change.
As the change in the output becomes larger, there may be a problem that the color development threshold value is not satisfied and the position where the color should be developed is not sufficiently developed.
Therefore, in the present embodiment, by changing the imaging position on the same optical axis by the stepped prism 22, it is possible to uniformly give the effect of depth expansion to each light ray.

An optical member such as a lens used in an optical system is generally designed to have the same optical characteristics concentrically around the optical axis O.
Therefore, in order to simply make the soft focus or multi-focus, it is conceivable to insert a lens diffuser, a soft focus lens, or the like.
However, when an array-shaped multi-beam laser light source is used as in the present embodiment, the laser light from the laser emitting portion 42a arranged at the end of the array head 44 is obliquely incident on the imaging lens system 21. As a result, there is a risk of astigmatism due to lateral displacement of the light beam.
Therefore, in the present embodiment, the stepped prism 22 is formed so as to extend in the Y direction, which is the array direction, and gives an optical path length divided into a plurality of X directions. With such a configuration, even a multi-beam laser light source arranged in an array can uniformly multifocalize a plurality of light rays arranged in the array direction.
The stepped prism 22 divides the incident laser light according to the incident position of the laser light in the X direction, and the imaging position in the Z direction is different for each of the divided laser lights.
Further, by using the stepped prism 22, unlike the lens diffuser and the soft focus lens, the loss and non-uniformity of the laser light are not caused, and only the imaging position of a part of the luminous flux is on the optical axis O. Can be changed with.

Further, in the present embodiment, the stepped prism 22 is provided with a plurality of steps with respect to the diameter of the laser beam so that the number of steps is maximized with respect to the beam diameter of the laser beam.
With such a configuration, it is possible to uniformly give the effect of depth expansion to each light ray.

Further, in the present embodiment, the stepped prism 22 is formed by laminating a plurality of flat plate-shaped optical members having different sizes.
With such a configuration, the stepped prism 22 can be manufactured at low cost.
The stepped prism 22 can be manufactured as an integral optical member from a single optical material by cutting or the like, in addition to the one obtained by laminating flat plate-shaped optical materials in this way.
If the stepped prism 22 is manufactured by cutting in this way, the light amount loss can be reduced because the interface between the flat plates does not exist.

Further, in the present embodiment, the stepped prism 22 has an antireflection film on at least one surface of the incident side and the emitted side of the laser beam.
With such a configuration, the reflectance on the surface of the stepped prism 22 is reduced, which contributes to the reduction of stray light and the reduction of light amount loss.

Further, in the present embodiment, the stepped prism 22 is arranged downstream of the imaging lens system 21 in the traveling direction of the laser beam.
With this configuration, the stepped prism 22 is arranged between the imaging position of the imaging lens system 21 and the imaging lens system 21, so that the laser emitting portion 42a emits light at each position when viewed from the image side. Since the effect is the same as when the lenses are arranged so as to be offset in the axial direction, it is possible to give each ray a uniform depth-enhancing lens without affecting the optical performance.

Further, in the present embodiment, the stepped prism 22 is provided with a plate-shaped member 24 made of synthetic quartz, which is a dust-proof portion having high hardness, on the surface on the most emitting side of the laser beam, and the plate-shaped member 24 is a housing of the laser head 20. It is installed so as to cover the opening.
With such a configuration, the laser head 20 can be easily miniaturized by suppressing an increase in the number of parts.

As a second embodiment of the present invention, FIG. 11 shows a different configuration example of the laser head 20.
In FIG. 11, the same parts as those already described as the first embodiment are numbered in the same manner, and the description thereof will be omitted as appropriate.

In the present embodiment, the laser head 20 has a different refractive index plywood 26 which is arranged between the imaging lens system 21 and the imaging position and includes cells 25 which are flat plates having a plurality of different refractive indexes in the X direction. doing.
A plurality of cells 25 are provided in the X direction, which is a vertical direction with respect to the Y direction, which is the array direction, and the Z direction, which is the direction of the optical axis O, and each cell 25 has the same thickness z and a different refractive index n1. It has ~ nx.
With this configuration, the different refractive index plywood 26 sets the optical path of the laser light incident on each cell 25 to the optical distances of n1 × z, n2 × z, n3 × z ... nxxz, respectively. , It is possible to obtain a multifocal laser beam given an optical path difference.

Further, in such a configuration, n1 to nx are gradually changed so as to have a low refractive index on the + X direction side and a high refractive index on the −X direction side, so that n1 <n2 <n3 ... <nx Is.
The light rays incident on the cell 25 having a low refractive index are imaged relatively on the front side, and the light rays incident on the cell 25 having a high refractive index are imaged relatively on the back side.
In this way, the different refractive index plywood 26 functions as an imaging position changing element that changes the imaging position of the laser beam of the imaging lens system 21.

Regarding the different refractive index plywood 26, the thickness, size, arrangement order, number, type, etc. of each cell 25 are not limited.
Further, as the shape of the different refractive index plywood 26, a flat plate shape having a thickness z is selected in this embodiment, but the shape may be changed as appropriate according to the design.

Further, in the first and second embodiments described above, both the stepped prism 22 and the different refractive index plywood 26 that function as the imaging position changing element are the imaging lens system 21 and the imaging lens system 21. Although it is placed between the image formation position and the image formation position, it is not limited to such a position.
Further, with respect to the shape of the stepped prism 22, various modified examples may be taken as described below.

For example, the stepped prism 22 may be arranged on the −Z direction side of the imaging lens system 21 as shown in FIG.
Alternatively, the stepped prism 22 may be arranged in the vicinity of the optical diaphragm 21b of the imaging lens system 21 as shown in FIG. In FIG. 13, the optical diaphragm 21b is arranged on the downstream side in the Z direction, but it may be on the upstream side.
Further, "near the optical diaphragm 21b" includes those arranged between the front lens system 21a and the rear lens system 21c.

Further, as shown in FIG. 14, the stepped prism 22 may have a stepped shape on both sides, or the corners of the respective inorganic optical materials 23 may be chamfered.

Although the embodiments according to the present invention have been described above, the present invention is not limited to the above-described embodiments as they are, and at the implementation stage, the components can be modified and embodied within a range that does not deviate from the gist thereof. .. In addition, various inventions can be formed by an appropriate combination of the plurality of components disclosed in the above-described embodiment. For example, some components may be removed from all the components shown in the embodiments. Further, different embodiments and modifications may be combined as appropriate.

10 Transport unit 14 Laser irradiation device 20 Laser unit (laser head)
21 Imaging lens system 22 Imaging position changing element (stepped prism)
23 Inorganic optical material 24 Dustproof part (plate-shaped member)
25 cells (imaging position changing element)
26 Different refractive index plywood (imaging position changing element)
41 Laser light emitting element 42 Optical fiber 100 Laser marker device (printing device)
LN1, LN6 1st meniscus lens LN2, LN5 2nd meniscus lens LN3, LN4 3rd meniscus lens S Recording medium (sheet)

Japanese Patent No. 5357790

Claims (11)

A laser light source in which multiple light emitting parts that emit laser light are arranged, and
An imaging lens system that collects laser light and
An imaging position changing element that changes the imaging position of the plurality of laser beams in the optical axis direction so as to be different on the optical axis of the imaging lens system.
Have,
The imaging position changing element is a laser unit characterized in that the imaging position differs depending on the incident position in the vertical direction with respect to the optical axis direction. The laser unit according to claim 1.
The imaging position changing element is a laser unit characterized by being a stepped prism whose thickness in the optical axis direction changes stepwise. The laser unit according to claim 2.
The stepped prism is a laser unit characterized in that it is formed by superimposing a plurality of flat plate-shaped prisms having different sizes. The laser unit according to claim 2.
The stepped prism is a laser unit characterized in that it is integrally formed of a single material. The laser unit according to any one of claims 2 to 4.
The imaging position changing element is a laser unit having an antireflection film on at least one surface of an incident side and an emitted side of the laser light. The laser unit according to claim 1.
The imaging position changing element is a laser unit characterized by having a plurality of regions having different refractive indexes in the vertical direction with respect to the optical axis direction. The laser unit according to any one of claims 1 to 6.
The laser unit is characterized in that the imaging position changing element is arranged on the downstream side in the traveling direction of the laser beam with respect to the imaging lens system. The laser unit according to claim 7.
The imaging position changing element is characterized in that the surface on the most emitting side of the laser beam is provided with a dustproof portion having high hardness, and the dustproof portion is attached so as to cover an opening of a housing of the laser unit. Laser unit to do. The laser unit according to any one of claims 1 to 6.
The laser unit is characterized in that the imaging position changing element is arranged on the upstream side in the traveling direction of the laser beam with respect to the imaging lens system. The laser unit according to any one of claims 1 to 6.
The imaging position changing element is a laser unit characterized in that it is arranged in the vicinity of the diaphragm of the imaging lens system. The laser unit according to any one of claims 1 to 10.
A transport unit that transports the recording medium so as to pass through the imaging position of the laser beam emitted from the laser unit, and a transport unit.
It has a control unit that controls the irradiation position of the laser beam.
A laser marker device that prints on the recording medium.

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