JPH07182439A - Bessel beam scanning device - Google Patents

Abstract

PURPOSE:To miniaturize a Bessel beam scanning device by converting a light beam having a circular section into a Bessel beam to scan an object, separating the scanning light beam from its reflected light, and converting this reflected light into an electric signal. CONSTITUTION:An axicon lens 12 converts the laser beam L emitted from a beam emitting part 11 and having a circular section into a Bessel beam. A polygon mirror 14 momentarily changes the direction of the light sent from a flat and hollow mirror 13 which reflects the Bessel beam and then scans the surface of a scanning object 1 by the beam L. A hole 17 is formed at the center part of the mirrow 13 that serves as a separating means. Thus the light reflected from the object 1 is reflected again by the mirrow 14 and led to the back of the mirrow 13 through the hole 17. Then this reflected light is condensed on the surface of a photodetector 20 by a condenser lens 18. Therefore the separating means is just required to have such a size that can process the reflected light propagating through the hollow part of the circular light beam. Thus a beam scanning device can be miniaturized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Bessel beam scanning device used for scanning a scanning object on which a symbol such as a bar code is formed with a light beam.

[0002]

2. Description of the Related Art A scanning device is widely used which scans a scanning object on which a symbol such as a bar code or a character is formed with a laser beam and detects the reflected light from the scanning object to read the symbol. . In such a scanning device, a Gaussian beam whose intensity distribution in a plane intersecting the optical axis has a Gaussian distribution is generally used.

This type of apparatus comprises a beam emitting means for generating a Gaussian beam, a scanning means for scanning a scanning target by the Gaussian beam by swinging the Gaussian beam left and right, a reflected light from the scanning target and a beam emitting means. It includes a separating means for separating the Gaussian beam from the light source, a light collecting means for collecting the separated reflected light, and a light receiving means for receiving the collected reflected light and converting it into an electric signal. The beam emitting means includes a laser light source, a lens and a diaphragm. A semiconductor laser or a He-Ne laser is applied to the laser light source. As the scanning means, a polygon mirror or a single-sided mirror capable of rotating or reciprocating angular displacement is applied. A hollow mirror with a hole in the center is applied as the separating means. A photodiode or a photomultiplier tube is applied to the light receiving means.

A hollow mirror as a separating means is a large-area mirror with a small hole for passing a laser beam. Such a configuration is adopted because the laser beam has a small beam diameter, but the reflected light from the scan target is weak, and therefore it is necessary to receive the light in a wide area. However, since the Gaussian beam has a limited length (depth) that can be narrowed down, it is necessary to provide an autofocus mechanism or the like in order to provide a deep reading depth. Therefore, there is a problem that the configuration becomes complicated.

Therefore, a scanning device using a Bessel beam that does not cause such a problem is, for example, a "Light sect".
ioning with large depth and high resolution: Gerd
By Hausler and Werner Heckel (15 DECEMBER 1988 / V
ol.27, No. 24 / APPLIED OPTICS) ", JP-A-4-171415
JP-A-4-217079 and JP-A-5-359
It is proposed in No. 04 bulletin. In the Bessel beam, the intensity distribution in the cross section intersecting the optical axis follows the Bessel function. The Bessel beam is generated by utilizing the interference of laser light, and although the beam diameter itself is large, it has a thin interference peak at the center whose level greatly differs from the surroundings, so it is actually considered as a thin beam for use. It is possible. The length of the portion having the narrow interference peak is extremely long compared to the depth range of the Gaussian beam.

[0006]

In the Bessel beam,
It is possible to obtain a substantially narrow beam over a wide range,
In order to take advantage of these advantages, it is necessary to expand the range of interference as much as possible. Therefore, the beam diameter tends to be large, and in some cases, the diameter may exceed 30 mm. Therefore, in order to separate the emitted light and the reflected light by using the above-mentioned hollow mirror applied to the scanning device using the Gaussian beam, it is necessary to enlarge the hole through which the beam passes. This hollow mirror is outside the hole through which the beam passes,
Since it is necessary to have an area necessary to receive sufficient reflected light from the scanning target, the entire hollow mirror becomes extremely large. Therefore, it is necessary to enlarge not only the hollow mirror but also the scanning means, and there is a problem that the size of the entire apparatus is increased and the cost is increased.

Further, when the reflected light from the scanning object is collected and made incident on the light receiving means, if the optical system related to the light receiving means is configured by focusing on the reflected light from the distant scanning object, a near optical system With respect to the reflected light from the scanning target, the focus position on the side of the light receiving means becomes far, so there is a possibility that a sufficient amount of light cannot be incident on the light receiving means. Conversely, when focusing on the reflected light from a nearby scan target,
The reflected light from a distant scanning target cannot be made incident on the light receiving means.

In order to avoid such a problem, it is necessary to increase the light receiving area of the light receiving means. However, increasing the light receiving area causes problems such as an increase in cost and an increase in size of the device, and also causes a problem that noise is easily picked up. Further, when a photodiode is used, the frequency characteristic deteriorates due to the increase of the light receiving area.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above technical problems and to provide a Bessel beam scanning device which can be downsized.

[0010]

In order to achieve the above object, the invention according to claim 1 is directed to a beam emitting means for emitting a light beam having an annular cross section, and a light emitted from the beam emitting means. Beam converting means for converting a beam into a Bessel beam, and scanning means for guiding the light beam from the beam converting means to a scanning target and scanning the surface of the scanning target with the Bessel beam formed by the function of the beam converting means. And by separating the light beam having a circular cross-section emitted from the beam emitting means and the light passing through the path corresponding to the hollow portion of the light beam, the light is guided from the beam emitting means toward the scan target. Separating means for separating the light beam and the reflected light from the scanning target, and receiving the reflected light from the scanning target separated by the separating means. Is a Bessel beam scanning apparatus which comprises a light receiving means for converting into an electric signal.

According to the above arrangement, the beam emitting means emits the light beam having an annular cross section. And the separating means is
By separating the ring-shaped light beam and the light passing through the path corresponding to the hollow portion of the light beam, the light beam from the beam emitting means and the reflected light from the scanning target are separated.
Therefore, the separating means only needs to have a size capable of processing the annular light beam. On the contrary,
In the prior art, since a separating reflecting mirror having a configuration in which a light beam passes through the central portion was used, an area for processing the reflected light from the scan target is required around the portion through which the light beam passes. Was said. As described above, conventionally, the reflected light passing through the outside of the light beam was used, whereas in the present invention, the reflected light propagating through the hollow portion of the annular light beam is made incident on the light receiving means. As a result, the size of the separating means can be reduced.

According to a second aspect of the invention, the scanning means comprises:
A beam reflecting portion which is rotatably provided around a predetermined axis line and which reflects a light beam from the beam converting means is provided at a peripheral portion, and reflected light from the scanning target is provided in a central portion in a direction along the predetermined axis line. It is characterized in that it includes a reflecting mirror having a light guiding means for guiding to and the driving means for rotating the reflecting mirror around the predetermined axis, and also serves as the separating means.

In this structure, the reflecting mirror is commonly used for the separating means and the scanning means, so that the structure is further simplified. Further, a light guide means for guiding the reflected light from the scanning target in the direction along the rotation axis of the reflecting mirror is provided at the center of the reflecting mirror. Therefore, it is possible to always guide the reflected light from the scanning target in a fixed direction, regardless of the rotation of the reflecting mirror.
Therefore, by arranging the light receiving means at a fixed position where the light guided by the light guiding means can be received, the reflected light from the scan target can be guided to the light receiving means without rotating the reflecting mirror.

According to a third aspect of the present invention, the beam conversion means has a beam conversion function part having a beam conversion function at a portion where the annular light beam from the beam emission means is incident, and the annular light beam It is a conversion element having a non-functional portion having no beam conversion function in a portion corresponding to the central portion, and is also characterized in that it also functions as the separating means.

According to this structure, the beam converting means has the non-functional portion having no beam converting function in the portion corresponding to the central portion of the annular light beam. Reflected light from the scan target is incident on the non-functional portion. Therefore, the beam converting means can also have the function of separating means,
This can further simplify the configuration. The invention according to claim 4 is characterized in that the separation means is provided with a condensing means for condensing the reflected light from the scanning target and guiding it to the light receiving means.

According to this structure, since the condensing means is provided in the separating means, it is possible to increase the amount of light incident on the light receiving means without using a condensing lens or the like separately from the separating means. According to a fifth aspect of the present invention, the separating means separates the light beam and the reflected light so that the optical axis of the light beam from the beam emitting means is different from the optical axis of the reflected light from the scan target. An optical axis conversion means for converting at least one of the optical axes is included.

According to this structure, the optical axes of the light beam generated from the beam emitting means and the reflected light from the object to be scanned are different from each other, whereby the light separation is achieved.

[0018]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a conceptual diagram showing the configuration of a symbol reading device to which an embodiment of the present invention is applied. The symbol reading device is for optically reading a symbol such as a barcode formed on the surface of the scan target 1 by scanning with a laser beam. This symbol reading device includes a beam emitting unit 11 that emits a laser beam having an annular cross section,
An axicon lens 12 as a beam converting means for converting the annular laser beam L generated from the beam emitting part 11 into a Bessel beam, and a flat hollow mirror 13 for reflecting the laser light from the axicon lens 12. Hollow mirror 1
The polygon mirror 14 achieves the scanning of the surface of the scanning target 1 by the laser beam by changing the direction of the light from 3 every moment. Axicon lens 12
Is a conical lens (also called a prism).

The hollow mirror 13 corresponds to a separating means. A hole 17 is formed in the center of the hollow mirror 13, and the reflected light reflected by the scan target 1 is reflected by the polygon mirror 14 and then guided to the back of the hollow mirror 13 through the hole 17. Then, the light is condensed on the light receiving surface of the light receiving element 20 by the condenser lens 18. A photodiode or a phototransistor is used for the light receiving element 20. When the scan target 1 is scanned at high speed, an avalanche photodiode or a photomultiplier tube may be used as the light receiving element 20.

The polygon mirror 14 has an inverted polygonal frustum shape, and a plurality of side surfaces thereof are reflection surfaces for reflecting the laser beam L. The polygon mirror 14 is rotated by a motor 19 at a constant speed around its axis 14a. As a result, the laser beam L repeatedly scans the surface of the scan target 1 at a constant speed. FIG. 2 is a diagram for explaining the internal configuration of the beam emitting unit 11 and the optical arrangement of each unit of the symbol reading device. The beam emitting unit 11 includes a laser light source 21, a concave lens 22 for expanding the beam diameter of the light from the laser light source 21 to a required size, and an axicon lens for converting the light from the concave lens 22 into an annular laser beam. And 23.
The laser light source 21 is composed of a He-Ne laser or a semiconductor laser. If the beam diameter is sufficiently large, the concave lens 22 is unnecessary. In the case of a semiconductor laser, the beam cross-sectional shape is elliptical, but if this is a problem, the beam shape may be shaped using a lens or pinhole. Further, since the beam that has passed through the axicon lens 23 tends to spread, if this poses a problem, it suffices to use a lens so that the light beams become substantially parallel.

The annular laser beam L emitted from the axicon lens 23 enters the axicon lens 12 as the beam converting means. Axicon lens 12
Refracts the annular beam L toward the optical axis 25 and produces a Bessel beam in the region ΔR. That is, in the region ΔR, the lights that have passed through the peripheral portion of the axicon lens 12 gather and interfere with each other, and a Bessel beam is generated. Therefore, in the region ΔR, the scan target 1
It is possible to satisfactorily read a symbol such as a barcode formed on the surface of the.

The hollow mirror 13 and the polygon mirror 14 are
As shown by the two-dot chain line in FIG. 2, it is interposed between the region R and the axicon lens 12. Hollow mirror 1
The hole 17 formed in the central part of 3 is formed closer to the optical axis 25 of the axicon lens 12 than the position where the annular beam is incident. Therefore, the laser beam L from the axicon lens 12 does not enter the light receiving element 20 through the hole 17. The polygon mirror 14 is interposed between the region ΔR and the axicon lens 12 in order to effectively use the region ΔR for scanning the scan target 1.

FIG. 3 is a diagram showing a structure for separating the laser beam L and the reflected light from the object to be scanned in comparison with the prior art. FIG. 3 (a) shows the configuration of this embodiment.
(b) shows a conventional technique. It is assumed that the outer radius of the laser beam L at the position of the separating hollow mirror 13 and the radius of the hollow portion thereof are R and r, respectively. At this time, the hollow mirror 13
Is an outer radius R having a hole 17 of radius r at the center. However, the radius r is set to a value that can guide a sufficient amount of reflected light from the scan target 1 to the light receiving element 20.

In the prior art shown in FIG. 3B, the hole 17
Light is separated using a hollow mirror 13P having P in the center. In this case, the laser beam passes through the hole 17P, and the reflected light from the scan target is reflected at the peripheral edge. 12P is an axicon lens. Light receiving element 2 reflected from the scan target
In order to make the amount of light incident on 0 the same as in the case of FIG. 3 (a), a reflection area of πr ² must be secured outside the hole 17P. Therefore, for example, the hollow mirror 1
Assuming that the radius of the Bessel beam at the position of 3P is R as in the case of FIG. 3A and the outer radius of the hollow mirror 13P is R ', the following equation (1) is established.

ΠR ′ ² = πR ² + πr ² ∴R ′ = (R ² + r ² ) ^1/2 > R (1) That is, by adopting the configuration of this embodiment, the hollow mirror 13 It is understood that the size can be reduced. FIG. 4 is a diagram showing an optical arrangement of a portion that guides the reflected light from the scan target to the light receiving element 20. For example, condenser lens 1
It is assumed that the focal length of 8 is f and the radius of the light receiving surface of the light receiving element 20 is d. The light receiving element 20 is installed on the optical axis 18a which is separated from the condenser lens 18 by the focal length f. At this time, the light emitted from the focal position on the opposite side of the condenser lens 18 becomes parallel light and enters the light receiving element 20,
The following formula (2) is established for the light that is generated in the direction of the angle θ from the position and is incident on the edge of the light receiving element 20.

Tan θ = d / f (2) On the other hand, the reflected light from the scanning object 1 located at a distance L from the condenser lens 18 is condensed from the condenser lens 18 to a point a. Then, from the formula of thin lens, the following (3)
The formula holds.

[0027]

[Equation 1]

By using the expression (3), the following expression (4) is obtained for the light generated from the scan target 1 at the angle α and incident on the edge portion of the light receiving element 20. However, the following
In the equation (4), D is the distance between the position where the light generated from the scan target 1 at the angle α passes through the condenser lens 18 and the optical axis 18a.

[0029]

[Equation 2]

From this, it is understood that the light generated from the scan target 1 toward the constant angle range is incident on the light receiving surface of the light receiving element 20 regardless of the distance from the condenser lens 18 to the scan target. . That is, regardless of the distance L from the condenser lens 18 to the scan target 1, a fixed amount of reflected light can be incident on the light receiving element 20. Therefore,
The reflected light from the scan target 1 can be satisfactorily detected without using a large-area light receiving element.

In the prior art, the area ΔC near the optical axis 18a
Since the light passing through can not be incident on the light receiving element,
When the scanning target is near, the reflected light from the scanning target cannot enter the light receiving element. As described above, according to this embodiment, the hollow mirror 13 for separating light is used.
Has a reflecting portion for reflecting the annular laser beam L in the peripheral portion, and a hole 17 for guiding the reflected light from the scan target 1 to the light receiving element 20 is formed in the center. Therefore, it is sufficient for the hollow mirror 13 to have a size corresponding to the cross section of the annular laser beam L. Therefore, the hollow mirror 13 can be miniaturized. Further, since the polygon mirror 14 does not need to be able to reflect the light propagating outside the annular laser beam L, the polygon mirror 14 can also be downsized. In this way, miniaturization of the entire device is achieved.

FIG. 5 is a conceptual diagram showing the configuration of the second embodiment of the present invention. 5, parts corresponding to the respective parts shown in FIG. 1 described above are designated by the same reference numerals. In this embodiment, instead of the hollow mirror 13, the separating reflecting mirror 6 is used.
0 is used. The separating reflector has a reflector 61 at the center.
In addition, the transparent portion 62 that transmits the laser beam L from the beam emitting portion 11 is provided on the peripheral portion.
As a result, the reflected light from the scan target 1 is reflected by the central reflecting portion 61 and the optical axis is converted, and then the condenser lens 1
It is guided to the light receiving element 20 via 8.

The separating reflecting mirror 60 can be formed by selectively depositing metal on the surface of a transparent plate such as glass to form the reflecting portion 61. The transparent portion 62 is mainly provided to facilitate the holding of the separating reflecting mirror 60. With such a configuration as well, it is possible to separate the laser beam L and the reflected light from the scanning target by using the small-area separating reflection mirror 60, and the same operation and effect as those of the first embodiment. Is obtained.

FIG. 6 is a conceptual diagram showing the configuration of the third embodiment of the present invention. 6, parts corresponding to the respective parts shown in FIG. 1 described above are denoted by the same reference numerals. In the present embodiment, instead of the hollow mirror 13 described above, a separating reflecting mirror 30 having a concave mirror portion 31 in the central portion and a flat mirror portion 32 in the peripheral portion is used. The concave mirror section 31 is
It is formed so that the light coming from the front surface side of the separating reflecting mirror 30 can be guided to the back of the separating reflecting mirror 30.

The reflected light from the scanning object 1 is reflected by the polygon mirror 14, is reflected by the concave mirror portion 31 of the separating reflection mirror 30 to have its optical axis converted, and then is guided to the light receiving element 20 while being condensed. . Therefore, as compared with the configurations of the first and second embodiments described above, the condenser lens 18 for condensing the reflected light from the scan target 1 is not necessary.

The separating reflecting mirror 30 in which the flat mirror portion 32 and the concave mirror portion 31 are integrally formed can be produced by coating the surface of a plastic molded product with a metal. Further, the plane mirror portion 32 and the concave mirror portion 31 do not have to be integrally formed from the beginning, and after being formed as separate parts, the separating reflecting mirror 30 may be formed by appropriately joining the both. .

Further, in the separating reflecting mirror 30, the concave mirror 3
The portions other than 1 may be formed of a transparent member to allow the laser beam L to pass therethrough, and the beam emitting portion 11 and the axicon lens 12 may be arranged in the same manner as in the configuration of FIG. FIG. 7 is a conceptual diagram showing the configuration of the fourth embodiment of the present invention. In FIG. 7, parts having the same configurations as the parts shown in FIG. 1 are designated by the same reference numerals. In this embodiment, the separating reflecting mirror 3 used in the third embodiment is used.
The scanning target is scanned by the laser beam L using the scanning reflecting mirror 40 having a configuration similar to that of 0.

Specifically, the scanning reflecting mirror 40 will be described.
Has a concave mirror section 41 in the center and a flat mirror section 42 for reflecting the light from the axicon lens 12 in the peripheral section. On the back surface of the scanning reflecting mirror 40, there is a cylindrical body 45.
Bonded at an angle of 5 degrees. A pulley 46 is formed at the lower end of the tubular body 45. The rotational force of a motor 47 serving as a driving unit is transmitted to the pulley 46 via a belt 48.

The rotational force of the motor 47 is guided to the scanning reflecting mirror 40 via the belt 48, the pulley 46 and the tubular body 45. As a result, the scanning reflecting mirror 40 has the axis 45a.
Rotate around. As a result, the optical path of the laser beam L from the axicon lens 12 changes every moment, and the scanning of the scan target 1 by the laser beam is achieved. The rotation direction of the motor 47 may be reversed at regular time intervals, and the scanning reflecting mirror 40 may be reciprocally angularly displaced within a constant angular range.

The reflected light from the scanning object 1 is reflected by the concave mirror portion 41.
And is guided in the direction along the axis 45a. Then, the light reflected by the concave mirror portion 41 propagates in the internal space of the tubular body 45 while being condensed, and is guided to the light receiving surface of the light receiving element 20. In the present embodiment, the concave mirror 41 functions as an optical axis converting means, a light guiding means and a light collecting means.
Thus, according to this embodiment, both the scanning of the laser beam L and the separation of the light are achieved by the scanning reflecting mirror 40. Therefore, the structure is further simplified, and the entire apparatus can be further downsized.

FIG. 8 is a conceptual diagram showing the configuration of the fifth embodiment of the present invention. In FIG. 8, the same parts as those shown in FIG. 1 are designated by the same reference numerals. In this embodiment, a hollow axicon lens 50 having a hole 51 formed in the center is used. That is, the portion where the annular laser beam L is incident is a beam converting function portion having a beam converting function, and the portion corresponding to the central portion of the annular laser beam L is a non-functional portion having no beam converting function. Has become.

A condensing lens 53 for condensing the reflected light from the scan target 1 is fitted and held in the hole 51. The light receiving element 20 is arranged between the condenser lens 53 and the beam emitting section 11. In this configuration, the axicon lens 50 also serves as a separating means, and the hollow mirror 13 for separating the light or the reflecting mirrors 60, 30 for separating the light and the separating mirror for the light as in each of the above-described embodiments. It is not necessary to include the scanning reflecting mirror 40 having the configuration. Further, since the condenser lens 53 is fitted in the hole 51, it is not necessary to use a condenser lens as a separate component.

FIG. 9 is a conceptual diagram showing the configuration of the sixth embodiment of the present invention. 9, parts corresponding to the respective parts shown in FIG. 8 are designated by the same reference numerals. In this embodiment, the hole 5 formed in the center of the axicon lens 50.
A concave mirror 80 is fitted in the inside of the unit 1. As a result, the reflected light from the scan target 1 is reflected by the concave mirror 80 to change its optical axis, and is guided while being condensed on the light receiving element 20 arranged at a position facing the concave mirror 80. With this configuration, the same effect as that of the configuration shown in FIG. 8 can be obtained. A flat mirror is used instead of the concave mirror 80, and the light reflected by the flat mirror is condensed by a condenser lens to receive the light receiving element 2.
You may make it inject into 0.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the first embodiment described above, the polygon mirror is used for scanning the laser beam, but the configuration in which the single-sided mirror is reciprocally angularly displaced within a predetermined angular range about a predetermined axis also produces a laser beam. It is possible to scan an object to be scanned.

In the above embodiment, the Bessel beam is generated from the annular laser beam using the axicon lens, but a hologram element may be used instead of the axicon lens. Further, in the above example,
Hollow mirror 13, separating reflecting mirror 30 and scanning reflecting mirror 40
Although the portion on which the laser beam L is incident is a plane mirror, the laser beam may be expanded or contracted by using this portion as a reflecting surface having a constant curvature.

Although the separating reflecting mirror 30 and the scanning reflecting mirror 40 each have a concave mirror portion, the concave mirror portion is replaced with a plane mirror, and it is suitable between the plane mirror and the light receiving element. You may make it interpose a different condensing lens.
In addition, various design changes can be made within the scope of the matters described in the claims.

[0047]

According to the first aspect of the present invention, since the reflected light propagating through the hollow portion of the annular light beam is made incident on the light receiving means, the separating means can be downsized, and eventually the separating means can be downsized. The entire device can be downsized. According to the invention described in claim 2, since one reflecting mirror is commonly used for the separating means and the scanning means, the structure is further simplified.

According to the invention described in claim 3, the beam converting means can also have a function as a separating means,
This can further simplify the configuration. According to the invention described in claim 4, it is possible to increase the amount of light incident on the light receiving means with a simple configuration without using a condenser lens or the like separately from the separating means. According to the fifth aspect of the invention, the light separation is achieved by making the optical axes of the light beam generated from the beam emitting means and the reflected light from the scan target different from each other.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a simplified configuration of a symbol reading device to which a first embodiment of the present invention is applied.

FIG. 2 is a conceptual diagram showing an internal configuration of a beam emitting unit and an optical arrangement of each unit.

FIG. 3 is a diagram showing an optical configuration related to a hollow mirror in comparison with a conventional technique.

FIG. 4 is a diagram showing an optical configuration related to a light receiving element.

FIG. 5 is a conceptual diagram showing a simplified configuration of a symbol reading device to which a second embodiment of the present invention has been applied.

FIG. 6 is a conceptual diagram showing a simplified configuration of a symbol reading device to which a third embodiment of the present invention has been applied.

FIG. 7 is a conceptual diagram showing a simplified configuration of a symbol reading device to which a fourth embodiment of the present invention has been applied.

FIG. 8 is a conceptual diagram showing a simplified configuration of a symbol reading device to which a fifth embodiment of the present invention has been applied.

FIG. 9 is a conceptual diagram showing a simplified configuration of a symbol reading device to which a sixth embodiment of the present invention has been applied.

[Explanation of symbols]

 1 Scanning Target 11 Beam Emitting Part 12 Axicon Lens 13 Hollow Mirror 14 Polygon Mirror 17 Hole 18 Condensing Lens 20 Light-Receiving Element 60 Separating Reflecting Mirror 61 Reflecting Part 62 Transparent Part 30 Separing Reflecting Mirror 31 Concave Mirror Part 32 Plane Mirror Part 40 Scanning Reflector 41 Concave mirror 42 Plane mirror 50 Axicon lens 53 Condenser lens 80 Concave mirror

Claims (5)

[Claims] 1. A beam emitting means for emitting a light beam having an annular cross section, a beam converting means for converting the light beam emitted from the beam emitting means into a Bessel beam, and scanning with the light beam from the beam converting means. A scanning means for guiding the surface of the object to be scanned and scanning the surface of the scanning object with a Bessel beam formed by the function of the beam converting means, a light beam having a circular cross section emitted from the beam emitting means, and a light beam of the light beam. Separating means for separating the light beam guided from the beam emitting means toward the scan target and the reflected light from the scan target by separating the light passing through the path corresponding to the hollow portion, and the separating means. A Bessel beam scanning device including: a light receiving unit that receives the reflected light from the scanning target separated by Place 2. The scanning means is provided rotatably around a predetermined axis, and has a beam reflecting portion for reflecting a light beam from the beam converting means on a peripheral portion thereof, and a central portion for scanning from the scanning object. A reflecting mirror having a light guide means for guiding reflected light in a direction along the predetermined axis and a driving means for rotating the reflecting mirror around the predetermined axis, and also serving as the separating means. The Bessel beam scanning device according to claim 1, wherein 3. The beam converting means has a beam converting function part having a beam converting function at a part where the annular light beam from the beam emitting means is incident, and a part corresponding to a central part of the annular light beam. 2. The Bessel beam scanning apparatus according to claim 1, wherein is a conversion element having a non-functional portion having no beam conversion function, and also serves as the separating means. 4. The separating means is provided with a condensing means for condensing reflected light from a scanning object and guiding the reflected light to the light receiving means. Bessel beam scanning device. 5. The separating means includes at least one of the light beam and the reflected light such that an optical axis of the light beam from the beam emitting means and an optical axis of reflected light from the scanning target are different from each other. 5. The Bessel beam scanning device according to claim 1, further comprising an optical axis conversion means for converting one optical axis.