JP7443867B2 - Laser unit and laser marker device - Google Patents

Description

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

2. Description of the Related Art Laser marker devices are known that focus laser light onto a recording medium such as thermal paper and apply thermal energy to the object to cause it to color.
In a laser marker device, the beam diameter at the imaging position (focus point) of the laser beam corresponds to the dot diameter that can be printed, and there is a range in which sufficient thermal energy can be applied to the recording medium while maintaining the dot diameter. 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 fall within a certain range (within the printing depth) due to the printable depth. Therefore, there is a need for a laser marker that is robust to a certain extent with respect to the printing position so that printing can be performed even if the printing object fluctuates due to vibrations or there are variations in the thickness of the printing object.

Examples of such depth expansion techniques include lens diffusers, soft focus lenses, and the like. However, such depth expansion techniques generally assume a single beam.
In addition, as another depth enlarging technique, a technique using a phase type optical element is also known (for example, Patent Document 1), but when the optical element has a concentric shape and multiple beams with an image height are incident, There is a concern that different refraction will be given to each image height, causing aberrations.

In order to solve such problems, the laser unit according to the present invention includes a laser light source in which a plurality of light emitting parts that emit laser light are arranged, an imaging lens system that focuses the laser light, and a plurality of laser light sources. 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 ; It is a stepped prism in which the thickness in the axial direction changes stepwise, and is characterized in that the image forming position differs depending on the incident position in the direction perpendicular to the optical axis direction.

According to the present invention, in a multi-beam laser marker using a common optical system, each light beam can have a uniform depth-expanding effect.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the schematic structure of one form of the winding conveyance apparatus provided with the laser marker device based on this invention. 1 is a diagram showing the configuration of a winding and conveying device equipped with a laser marker device according to the present invention. 1 is a diagram showing the configuration of a laser marker device according to the present invention. FIG. 4 is a diagram showing an example of the configuration of the laser head shown in FIG. 3 when viewed from the Y direction. FIG. 4 is a diagram showing an example of the configuration of the laser head shown in FIG. 3 when viewed from the X direction. 1 is a diagram showing an example of the configuration of a stepped prism according to the present invention. It is a figure showing an example of the effect of the stepped prism concerning the present invention. FIG. 3 is a diagram showing the difference in output results between the laser marker device according to the present invention and a comparative example. It is a figure showing an example of control of the laser marker device concerning the present invention. It is a figure showing an example of the output at the time of printing of the laser marker device concerning the present invention. It is a figure which shows an example of the structure using a different refractive index plywood. 4 is a diagram showing an example of another configuration of the laser marker device shown in FIG. 3. FIG. 4 is a diagram showing an example of another configuration of the laser marker device shown in FIG. 3. FIG. It is a figure which shows another example of the structure of the stepped prism based on this invention.

Hereinafter, embodiments according to the present invention will be sequentially described using the drawings. In the embodiments, parts having the same functions and configurations are denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. Some drawings may be partially omitted or simplified to facilitate understanding of some configurations.

The printing device 100, which is a laser marker device according to the present invention, includes a device main body 30 constituting a laser unit, a laser head 20 for emitting laser light, a sheet S of thermal paper as a recording medium, and a sheet S. It has a transport section 10 for transporting.
Note that the printing device 100 in this embodiment functions as a laser marker device that prints using thermal energy by irradiating laser light onto the surface of the sheet S, but is not limited to printing characters, and can print characters, symbols, and lines. , a figure, a solid image, a combination thereof, a bar code, a two-dimensional code, and other images may be printed.

The sheet S is the object to be printed in this embodiment, and in addition to thermal paper, any material may be used as long as it absorbs light and converts it into heat, causing changes in hue, reflectance, etc., such as marking on metal. Also included. Further, the sheet S is not limited to a sheet shape, and may take various shapes.
Note that the "material that causes changes in hue, reflectance, etc. due to heat" constituting the sheet S includes, for example, a combination of an electron-donating dye precursor and an electron-accepting color developer used in conventional thermal paper. Can be used. In addition, materials that undergo changes in hue, reflectance, etc. due to heat include materials that undergo a complex reaction of heat and light, such as a color change reaction due to solid phase polymerization caused by heating a diacetylene compound and irradiating it with ultraviolet light. included.

In the present embodiment, as shown in FIG. 1, the conveying unit 10 includes a feeding roller 11 on which the sheet S is wound, and which feeds out the sheet S by rotating in a predetermined direction; This is a conveying means having a winding roller 12 for winding up.
Further, an encoder 49 serving as a detection means for detecting the speed of the sheet S is provided on the conveyance path of the sheet S of the conveyance unit 10, and detects the conveyance speed of the sheet S and the writing speed of the laser head 20. Control is performed to ensure that the

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 laser light.
Note that the length of the sheet S in the present embodiment in the width direction perpendicular to the feeding direction of the sheet S is wider than the width that can be irradiated by the laser head 20.
Therefore, the print width is secured by attaching a plurality of laser heads 20 at positions that do not overlap with each other, but the configuration is not limited to this, and a single laser head 20 may be used. In this way, even when the area to be printed is wider than the irradiation range of the laser head 20, a sufficient printing width can be ensured by providing a plurality of laser heads 20.

An image information output section 47 such as a personal computer that outputs image information, a cooling device 50, and an encoder 49 are connected to the apparatus main body section 30.
The device main body 30 and the laser head 20 are connected by a single or plural optical fibers 42, and as will be described later, the laser beam oscillated by the device main body 30 is transmitted via the optical fiber 42 and the laser head 20. and irradiates 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 light emitting element 41 via the optical fiber 42 and the laser head 20, and records an image (visible image) made up of drawing units. .

For example, as shown in FIG. 2, the device main body 30 includes a laser emitting element 41, a drive driver 45, a corresponding controller 46, and a power supply section 48 for supplying power to the laser emitting element 41. There is.
The device main body section 30 also includes a laser irradiation device 14 having a laser array section 14a and a fiber array section 14b. In the present embodiment, the laser irradiation device 14 includes fibers arranged in an array in the Z-axis direction, which is perpendicular to the X-axis direction, which is the moving direction of the sheet S, which is the recording target. It is an array.
In this embodiment, the device main body 30 that performs control to emit the laser beam and the laser head 20 that performs control to emit the laser beam toward the sheet S function as one "laser unit." do.

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

The laser emitting element 41 can be appropriately selected depending on the purpose, and for example, a semiconductor laser, a solid-state laser, a dye laser, etc. can be used. Among these, the laser emitting element 41 is preferably a semiconductor laser because it has wide wavelength selectivity, is small so that the device can be downsized, and can be made at low cost.

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

In the laser light emitting element 41, which is the emitting means, not all of the applied energy is converted into laser light. Normally, the laser light emitting element 41 generates heat by converting energy that is not converted into laser light into heat. Therefore, the laser light emitting element 41 is cooled by the cooling device 50 which is a cooling means.
Further, the laser irradiation device 14 of this embodiment uses the fiber array section 14b, so that the laser light emitting elements 41 can be arranged apart from each other. This makes it possible to reduce the influence of heat from the adjacent laser emitting elements 41 and efficiently cool the laser emitting elements 41, thereby avoiding temperature increases and variations in the laser emitting elements 41. It is possible to reduce variations in the output of laser light, and improve density unevenness and white spots.
Note that the output of the laser beam is the average output measured by a power meter. There are two types of laser light output control methods: a method of controlling the peak power, and a method of controlling the pulse emission ratio (duty: laser emission time/cycle time).

The cooling device 50 is of a liquid cooling type that cools the laser light emitting elements 41 by circulating a coolant, and includes a heat receiving part 51 where the coolant receives heat from each laser light emitting element 41, and a heat radiating part which radiates the heat of the coolant. 52. The heat receiving section 51 and the heat dissipating section 52 are connected by cooling pipes 53a and 53b. The heat receiving part 51 is provided with a cooling pipe made of a good heat conductive material through which a cooling liquid flows inside a case made of a good heat conductive material. The plurality of laser emitting elements 41 are arranged in an array in the heat receiving section 51.

The heat radiation section 52 includes a radiator and a pump for circulating coolant. The coolant sent out by the pump of the heat radiating section 52 flows into the heat receiving section 51 through the cooling pipe 53a. The cooling liquid cools the laser light emitting elements 41 by removing heat from the laser light emitting elements 41 arranged in the heat receiving part 51 while moving through the cooling pipe in the heat receiving part 51 . The coolant whose temperature has increased by absorbing the heat of the laser emitting element 41 flowing out from the heat receiving section 51 moves within the cooling pipe 53b, flows into the radiator of the heat dissipating section 52, and is cooled by the radiator. The coolant cooled by the radiator is again sent to the heat receiving section 51 by the pump.

The fiber array section 14b arranges a plurality of optical fibers 42 provided corresponding to the laser emitting elements 41 and the vicinity of the ends of these optical fibers 42, which serve as laser emitting sections, in an array in the vertical direction (Z-axis direction). and an array head 44 for holding the array head.
Further, each laser input portion of the optical fiber 42 is attached to the laser output surface of the corresponding laser light emitting element 41.

Note that if one array head 44 attempts to hold all the optical fibers 42, the array head 44 will become long and easily deform. As a result, with one array head 44, it is difficult to maintain the linearity of the beam array and the uniformity of the beam pitch. For this reason, it is desirable that the array head 44 hold 100 to 200 optical fibers 42. Further, the laser irradiation device 14 has a plurality of array heads 44 holding 100 to 200 optical fibers 42 arranged side by side in the Z-axis direction, which is perpendicular to the moving direction of the sheet S. preferable. In this embodiment, each array head 44 has 192 optical fibers 42 arranged side by side in the Y direction.
In this embodiment, the array head 44 is an optical fiber array arranged one-dimensionally in the Y direction, but the optical fibers 42 may be arranged, for example, in a zigzag pattern, in two rows, or two-dimensionally.

FIG. 3 is a diagram illustrating the 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 diameter R formed by irradiating laser light and developing color is continuous at the focal position where the light is focused on the sheet S. .

In this embodiment, the laser head 20 is fixed and is 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 The X direction in which the sheet S moves is defined as the "main scanning direction" and the "sub scanning direction". The main scanning direction and the sub-scanning direction are orthogonal to each other.

Note that since the array head 44 and the sheet S are moved relative to each other to record an image on the sheet S, the array head 44 may be moved relative to the sheet S, and the sheet S may be moved relative 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 imaging lens system 21 on the exit side, that is, on the Z direction side of the imaging lens system 21. It has a stepped prism 22, which is an imaging position changing element, and is arranged at a stepped prism 22, which is an imaging position changing element.
Note that FIG. 4 is a diagram of the laser head 20 viewed from the X direction side, which is the sub-scanning direction, and FIG. 5 is a diagram of the laser head 20, similarly viewed from the Y direction side, which is the main scanning direction.
In FIG. 5, a plurality of laser emitting portions 42a, which are light emitting points, are arranged side by side toward the front.

The imaging lens system 21 includes a front lens system 21a that converts a diverging laser beam emitted from each optical fiber 42 into a parallel beam, an optical aperture 21b, and a laser beam on the surface of the sheet S which is the irradiation surface of the laser beam. This optical system is made up of optical components such as a plurality of lenses, and a rear lens system 21c that collects light. 4 and 5 show main ray diagrams of the imaging lens system 21.
In this embodiment, the front lens system 21a and the rear lens system 21c are formed symmetrically with respect to the image-side focal plane of the front lens system 21a (the position of the optical aperture 21b in FIGS. 4 and 5).
Further, since the position of the array head 44 where each end face of the optical fiber 42 is arranged functions as a pseudo light emitting part that emits laser light as a multi-beam laser light source, the laser emitting part 42a, which is the end face of the optical fiber 42, It corresponds to "a laser light source in which a plurality of light emitting parts are arranged to emit laser light". In the present embodiment, the output waveform of the laser beam from the laser emitting section 42a is a top hat type laser beam, but the configuration is not limited to this, and the output waveform of the laser beam may have a Gaussian distribution.

Both the front lens system 21a and the rear lens system 21c are composed of three meniscus lenses. 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, the rear lens system 21c includes a first meniscus lens LN6, a second meniscus lens LN5 with a convex surface facing the image side, and a third meniscus lens LN4 with a concave surface facing the object side. To the side, they are arranged in the reverse order from the front lens system 21a.

In this 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 inorganic optical materials 23 made of BK7 and having different sizes are laminated.
Among the inorganic optical materials 23, a plate member 24 made of synthetic quartz, which is a dustproof window and functions as a dustproof part, is attached further to the image side than the one disposed closest to the +Z side.
As shown in FIG. 5, the stepped prism 22 has a different thickness distribution in a stepped manner in the X direction perpendicular to the Y direction, which is the direction in which the array heads 44 are arranged. The imaging position is changed to a different imaging position for each stage incident in the X direction. In other words, the laser beam is divided in the X direction, which is perpendicular to the optical axis direction of the laser beam, and a different imaging position is given to each divided laser beam. In other words, the light beam emitted from one laser emitting section 42a is emitted onto the sheet S with a plurality of image formation positions depending on the incident position in the X direction.
Specifically, as schematically shown in a ray diagram in FIG. When the thickness per sheet is l, the number of sheets of inorganic optical material 23 passing through changes depending on the incident position in the X direction, so the optical path length changes by xnl (x = 1, 2, 3..., 7). becomes.
Due to the difference in optical path length, the light beams passing through each inorganic optical material 23 in the X direction are multifocalized with the imaging position on the optical axis O, as illustrated in FIGS. 7(a) and 7(b). .
That is, the thermal energy given by irradiating the sheet S with the focused laser beam is distributed in the depth direction of the sheet S as shown in FIGS. 8(a) to 8(c), respectively.
In addition, in FIGS. 8(a) to (c), the solid line shows the light intensity of the laser beam when the stepped prism 22 is provided at the position shown in FIG. 7, and as a comparative example, the intensity of the laser beam when the stepped prism 22 is not provided The light intensity of the laser beam is shown by a broken line.
In addition, in FIGS. 8(a) to (c), the imaging position without the stepped prism 22 is defined as def=0, the position shifted toward the front is def-0.5 mm, and the position shifted toward the back is def +0.5mm. Further, the horizontal axis indicates the measurement coordinates when the center of the optical axis O of the laser beam is set to 0, and the vertical axis indicates the irradiance (W/mm ² ) of the laser beam. That is, in FIGS. 8(a) to 8(c), the area where the irradiance equal to or greater than a predetermined value is measured represents the beam diameter of the laser light.

As is clear from the graphs in FIGS. 8(a) to 8(c), by providing the stepped prism 22, it is possible to uniformly give each light beam a depth expanding effect in the depth direction of the sheet S. , the distribution of thermal energy is also made uniform in the depth direction, expanding the printable depth.

Now, the operation when printing on the sheet S using the printing apparatus 100 having such a configuration will be described.
First, an image information output unit 47 such as a personal computer inputs image information to the controller 46 . The controller 46 generates drive signals (control pulses) 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.
The controller 46 transmits a drive signal (control pulse) for driving each drive driver 45 to each drive driver 45 when the number of clocks oscillated by the clock generator reaches a specified number of clocks.

Upon receiving the drive signal (control pulse), each drive driver 45 transmits a current pulse to drive the corresponding laser light emitting element 41 . The laser light emitting element 41 outputs a light emission pulse and irradiates laser light according to the drive of the drive driver 45. The laser light emitted from the laser emitting element 41 enters the corresponding optical fiber 42 and is emitted from the laser emitting part 42a of the optical fiber 42. The laser light emitted from the laser emitting part 42a of the optical fiber 42 passes through the imaging lens system 21, and then passes through the stepped prism 22, which is an imaging position changing element, and is irradiated onto the surface of the sheet S, which is the recording target. Ru. By heating the surface of the sheet S with the laser beam irradiated, 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 control pulses and light emission pulses. FIG. 9(a) shows a timing chart of control pulses and light emission pulses, and FIG. 9(b) shows IL characteristics of the laser. As shown in Figure 9, the rise of the light emission pulse is slightly delayed compared to the current pulse because of the correlation between the IL characteristics of the laser output and the current value. This is because it does not emit light.

By the way, when a so-called scanning laser marker is used as a printing device, which records an image on the recording target by deflecting laser light using a galvano mirror, images such as characters are produced by the rotation of the galvano mirror and the drive driver. Recording is performed by irradiating laser light with pulse control.
Therefore, when recording a certain amount of information on a recording target, the rotational speed of the galvanometer mirror often becomes a limit to the writing speed, creating the problem that high-speed writing is difficult.

On the other hand, the laser head 20 in this embodiment is a multi-beam laser light source using a laser array in which a plurality of laser emitting sections 42a are arranged in an array.
Therefore, an image can be recorded on the sheet S by ON/OFF control of the laser light emitting element 41 corresponding to each pixel. Thereby, even if the amount of information is large, an image can be recorded on the sheet S without reducing the conveyance speed of the sheet S. Therefore, according to the printing apparatus 100 of this embodiment, even when recording a large amount of information on a recording target, images can be recorded without reducing productivity.
Note that the conveying speed of the sheet S in the conveying section 10 may be set as appropriate depending on the required speed, but writing is sufficiently possible at a conveying speed of about 10 m/s, for example.

Now, since the laser irradiation device 14 records an image by applying thermal energy to the sheet S at high speed based on the principle of heating the sheet S by irradiating laser light, when the conveyance speed of the conveyance section 10 increases, It is necessary to use a high-output laser emitting element 41. Specifically, the number of outputs per laser light emitting element 41 is about 10 W/piece, and the amount of heat generated by the laser light emitting element 41 is large.
Further, in this embodiment, in order to set the resolution to about 200 dpi, 192 laser emitting sections 42a are arranged in an array in the array head 44 at a pitch of 127 μm. With this configuration, high-power laser beams are concentrated, resulting in a large amount of heat generation.

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

Here, the manner in which printing is performed on the sheet S will be explained.

FIG. 10 is a diagram illustrating printing on the sheet S. To simplify the explanation, a case will be described in which the sheet S is stationary, but it may be assumed that a similar phenomenon occurs during conveyance of the sheet S before the sheet S passes through the irradiation range of the laser head 20.
The laser light emitted from the laser light emitting element 41 is transmitted as thermal energy to the laser spot position on the surface of the sheet S, in other words, to the image formation position by the imaging lens system 21.
As shown in FIG. 10, the thermal energy generally follows a Gaussian distribution with high energy at the center and low energy at the edges.

A coloring threshold value exists in the sheet S, and a portion exceeding the coloring threshold value is colored. The color density is proportional to the amount of thermal energy. Further, the coloring threshold value differs depending on the material of the sheet S.

When the imaging position of the laser beam by the imaging lens system 21 is set to def=0, the output of the laser beam is from the imaging position in the Z direction, that is, in the sheet The larger the shift in the thickness direction of S, the greater the change.
The larger the change in the output, the less the coloring threshold is satisfied, which may cause problems such as insufficient coloring at positions where coloring should occur.
Therefore, in this embodiment, by changing the imaging position on the same optical axis using the stepped prism 22, it is possible to uniformly give each light beam the effect of expanding the depth.

Now, optical members such as lenses used in an optical system are generally designed to have the same optical characteristics concentrically around the optical axis O.
Therefore, in order to simply achieve soft focus or multifocus, it is conceivable to insert a lens diffuser plate, a soft focus lens, or the like.
However, when an arrayed multi-beam laser light source is used as in this embodiment, the laser light from the laser emitting part 42a arranged at the end of the array head 44 enters the imaging lens system 21 obliquely. This may cause astigmatism due to lateral deviation of the light beam.
Therefore, in this embodiment, the stepped prism 22 is formed to extend in the Y direction, which is the array direction, and provides an optical path length divided into a plurality of sections in the X direction. With this configuration, even in the case of a multi-beam laser light source arranged in an array, it is possible to uniformly perform multifocalization on a plurality of light beams lined up in the array direction.
The stepped prism 22 divides the incident laser beam depending on the incident position of the laser beam in the X direction, and the image formation position in the Z direction is different for each divided laser beam.
Furthermore, by using the stepped prism 22, there is no loss or non-uniformity of laser light unlike with lens diffusers or soft focus lenses, and the imaging position of only a portion of the light beam is placed on the optical axis O. It can be changed with .

Further, in this embodiment, the stepped prism 22 is provided with a plurality of steps relative to the diameter of the laser beam so that the number of steps is maximum relative to the beam diameter of the laser beam.
With this configuration, it is possible to uniformly give each light beam the effect of expanding the depth.

Further, in this embodiment, the stepped prism 22 is formed by laminating a plurality of flat optical members of different sizes.
With this configuration, the stepped prism 22 can be manufactured at low cost.
Note that the stepped prism 22 can be manufactured as an integral optical member from a single optical material by cutting or the like, other than by laminating flat optical materials as described above.
If the step-like prism 22 is manufactured by cutting in this manner, there will be no interface between the flat plates, so that loss of light amount can be reduced.

Further, in this embodiment, the stepped prism 22 has an antireflection film on at least one surface of the laser light incident side and the laser light output side.
This configuration reduces the reflectance on the surface of the stepped prism 22, contributing to reducing stray light and light loss.

Further, in the present embodiment, the stepped prism 22 is arranged downstream of the imaging lens system 21 in the direction in which the laser light travels.
With this configuration, since the stepped prism 22 is arranged between the imaging position of the imaging lens system 21 and the imaging lens system 21, the laser emitting section 42a emits light at each position when viewed from the image side. Since the effect is similar to that obtained by disposing the light beams shifted in the axial direction, it is possible to uniformly increase the depth of each light beam without affecting the optical performance.

Further, in this embodiment, the stepped prism 22 includes a plate member 24 made of synthetic quartz, which serves as a hard dustproof part, on the surface on the side where the laser beam is most emitted. It is installed to cover the opening.
With this configuration, the laser head 20 can be easily downsized by suppressing an increase in the number of parts.

Now, as a second embodiment of the present invention, a different configuration example of the laser head 20 is shown in FIG.
Note that in FIG. 11, the same parts as those in the configuration already described in the first embodiment are given the same numbers, and the description thereof will be omitted as appropriate.

In this embodiment, the laser head 20 is disposed between the imaging lens system 21 and the imaging position, and includes a modified refractive index plywood 26 that includes cells 25 that are flat plates having a plurality of different refractive indexes in the X direction. are doing.
A plurality of cells 25 are provided in the X direction, which is perpendicular 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. ~nx.
Due to this configuration, the different refractive index plywood 26 makes the optical path of the laser beam incident on each cell 25 an optical distance of n1×z, n2×z, n3×z...nx×z, respectively. , it is possible to obtain multifocal laser light by giving an optical path difference.

In addition, in this configuration, n1 to nx change stepwise such that the refractive index is low on the +X direction side and high on the -X direction side, so n1<n2<n3...<nx It is.
The light rays incident on the cell 25 with a low refractive index form an image relatively to the front side, and the light rays incident on the cell 25 with a high refractive index form an image relatively on the back side.
In this way, the modified 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 modified refractive index plywood 26, the thickness, size, order of arrangement of glass materials, number, type, etc. of each cell 25 do not matter.
Further, in this embodiment, the shape of the different refractive index plywood 26 is a flat plate having a thickness of z, but the shape may be changed as appropriate depending on the design.

Furthermore, in the first and second embodiments described above, both the stepped prism 22 and the variable refractive index plywood 26 functioning as the imaging position changing element are connected to the imaging lens system 21 and the imaging lens system 21. Although it is arranged between the imaging position and the imaging position, it is not limited to this position.
Further, the shape of the stepped prism 22 may also be modified in various ways as described below.

For example, the stepped prism 22 may be placed closer to the −Z direction than the imaging lens system 21, as shown in FIG.
Alternatively, the stepped prism 22 may be placed near the optical aperture 21b of the imaging lens system 21, as shown in FIG. In addition, in FIG. 13, it is arranged downstream of the optical diaphragm 21b in the Z direction, but it may be arranged upstream.
Furthermore, "near the optical aperture 21b" includes those disposed between the front lens system 21a and the rear lens system 21c.

Furthermore, the stepped prism 22 may have stepped prisms on both sides, as shown in FIG. 14, or the corners of each inorganic optical material 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-mentioned embodiments as they are, and the present invention can be embodied by modifying the constituent elements within the scope of the gist at the implementation stage. . Moreover, various inventions can be formed by appropriately combining the plurality of components disclosed in the above-described embodiments. For example, some components may be deleted from all the components shown in the embodiments. Furthermore, different embodiments and modifications may be combined as appropriate.

10 Transport section 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 Cell (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 First meniscus lens LN2, LN5 Second meniscus lens LN3, LN4 Third meniscus lens S Recording medium (sheet)

Patent No. 5357790

Claims (10)

a laser light source in which a plurality of light emitting parts that emit laser light are arranged;
an imaging lens system that focuses the laser beam;
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;
has
The imaging position changing element is a stepped prism whose thickness in the optical axis direction changes stepwise, and the imaging position differs depending on the incident position in a direction perpendicular to the optical axis direction. laser unit. The laser unit according to claim 1,
The laser unit is characterized in that the stepped prism is constructed by overlapping a plurality of flat prisms of different sizes . The laser unit according to claim 1 ,
A laser unit characterized in that the stepped prism is integrally formed from a single material . The laser unit according to any one of claims 1 to 3 ,
The laser unit is characterized in that the image forming position changing element has an antireflection film on at least one surface of the incident side and the output side of the laser beam . The laser unit according to claim 1 ,
The laser unit is characterized in that the imaging position changing element has a plurality of regions having different refractive indexes in a direction perpendicular to the optical axis direction . The laser unit according to any one of claims 1 to 5 ,
The laser unit is characterized in that the imaging position changing element is disposed downstream of the imaging lens system in the traveling direction of the laser beam . The laser unit according to claim 6 ,
A laser unit characterized in that the imaging position changing element includes a dustproof section on the surface closest to the emission side of the laser beam, and the dustproof section is attached so as to cover an opening of a housing of the laser unit. . The laser unit according to any one of claims 1 to 5 ,
The laser unit is characterized in that the imaging position changing element is disposed upstream of the imaging lens system in the traveling direction of the laser beam . a laser light source in which a plurality of light emitting parts that emit laser light are arranged;
an imaging lens system that focuses the laser beam;
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;
has
The laser unit is characterized in that the imaging position changing element is disposed near an aperture of the imaging lens system, and the imaging position differs depending on an incident position in a direction perpendicular to the optical axis direction . The laser unit according to any one of claims 1 to 9,
a transport unit that transports the recording medium so as to pass through the imaging position of the laser light irradiated from the laser unit;
a light emission control unit that controls the light emission pattern of the laser light;
A laser marker device that prints on the recording medium.

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