Narrow beam generating device

Abstract

Provided is a narrow beam generation device capable of generating a linear narrow beam having a diameter equal to or less than a predetermined size from light emitted from an arbitrary light source without depending on a distance from an emission position. The narrow beam generation device includes: a light source; a condensing unit that collimates or condenses the divergent light from the light source within a predetermined solid angle range; a first light focusing unit that focuses at least a portion of the light emitted from the light focusing unit in a region narrower than the incident beam; and a second light ray gathering unit that gathers the light rays emitted from the first light ray gathering unit into a linear narrow beam, the first light ray gathering unit and the second light ray gathering unit are both odd-order aspheric optical elements or optical systems, and the second light ray gathering unit is disposed at a light ray gathering position by the first light ray gathering unit. The first light gathering unit and the second light gathering unit have different shapes.

Description

Technical Field

[0001] The present invention relates to a narrow beam generating device. Background Art

[0002] In the past, there are known projector devices and display devices that use light sources such as laser light emitting elements. For example, an integrated photon module is disclosed, which includes: one or more light sources such as lasers; beam shaping optical elements; coupling optical elements; MEMS scanners; and one or more mechanical structural elements such as optical frames that facilitate installation and are used to maintain optical configurations (for example, refer to Patent Document 1).

[0003] However, in recent years, glasses-type display devices that can bring virtual reality images such as AR, MR, VR, etc. into the field of vision are emerging. In particular, the laser scanning type display method called LBS (Laser Beam Steering) can also be applied to retinal scanning displays, allowing even people with poor eyesight to see clear images (for example, refer to Patent Document 2).

[0004] In addition, as a means of adjusting the beam diameter and light intensity distribution of laser light emitted from a semiconductor laser, a technology has been disclosed in which a pair of axicons with equal apex angles are arranged so that their bottom surfaces face each other and the spacing can be adjusted along the optical axis (for example, see Patent Document 3).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application No. 2009-533715

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 11-064782

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 10-239632 Summary of the invention

[0010] Problems to be solved by the invention

[0011] In the prior art, since only a narrow beam of light can be obtained at the focal position or before and after the short focal position, it is necessary to accurately place the object at the focal position when using it in laser drawing or cutting processing, and its conveying mechanism or focusing mechanism for aligning the focus must be complex and precise, and the overall structure of the device becomes larger. In addition, in the fiber coupling of lasers, a coupling lens is used to focus the light beam and input the light to the end face of the optical fiber, but there is a divergence angle from the coupling point, so there is a loss in coupling. Therefore, as an example, when the light of the laser diode is injected into a single-mode optical fiber (core diameter 3μm), there is a problem that only about 30% of the coupling efficiency is obtained.

[0012] In addition, in order to properly implement devices such as retinal scanning displays disclosed in Reference 2, it is necessary to project a high-definition image onto a very small area such as the retina. Therefore, the light beam that scans the retina is preferably of a very small diameter (for example, about 20 μm). However, in previous technologies, for example, the diameter of a Gaussian beam cannot be set to a parallel beam of less than about 300 μm, so a point beam that focuses at a specific distance is used as an alternative. The point beam becomes a very small beam diameter at a specific distance, but the beam diameter at the position before and after the focal length becomes larger, so in a glasses-type display device, due to individual differences in the wearers of the glasses, the distance at which the image reaches the retina is different, so there is a problem of requiring a detailed adjustment mechanism for adjusting the distance.

[0013] The present invention has been made in view of the above circumstances, and an object thereof is to provide a narrow beam generating device capable of generating a linear narrow beam having a diameter equal to or smaller than a predetermined size based on light emitted from an arbitrary light source, regardless of the distance from an emission position.

[0014] Means for solving problems

[0015] (1) The present invention relates to a narrow beam generating device, comprising: a light source; a focusing unit, which collimates or focuses divergent light from the light source within a predetermined solid angle range; a first light gathering unit, which gathers at least a portion of light emitted from the focusing unit into an area narrower than an incident light beam; and a second light gathering unit, which gathers light emitted from the first light gathering unit into a linear narrow beam, wherein the first light gathering unit and the second light gathering unit are both optical elements or optical systems that are odd-order aspherical surfaces, and the second light gathering unit is arranged at a gathering position of light based on the first light gathering unit, and the first light gathering unit and the second light gathering unit have different shapes.

[0016] (2) The narrow beam generating device according to (1), wherein the first light focusing unit and the second light focusing unit are both composed of optical elements having an axicon effect.

[0017] (3) A narrow beam generating device according to (1) or (2), wherein, when the first light gathering unit and the second light gathering unit are both composed of one refractive surface, the first light gathering unit and the second light gathering unit are constituted as an integrated element, and when the first light gathering unit and the second light gathering unit both have one reflecting surface, a hole portion is formed on the reflecting surface of the first light gathering unit, through which the linear narrow beam focused by the second light gathering unit can pass.

[0018] Effects of the Invention

[0019] According to the present invention, it is possible to provide a narrow beam generating device capable of generating a linear narrow beam having a diameter equal to or smaller than a predetermined size based on light emitted from an arbitrary light source, regardless of the distance from the emission position. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram showing the structure of a narrow beam generating device according to the first embodiment of the present invention.

[0021] Figure 2 It is a schematic diagram showing the structure of a narrow beam generating device according to a second embodiment of the present invention.

[0022] Figure 3 yes Figure 2 AA line cross-section diagram.

[0023] Figure 4A It is a perspective view showing a first light focusing unit and a second light source focusing unit according to a second embodiment of the present invention.

[0024] Figure 4B It is a perspective view showing a first light focusing unit and a second light source focusing unit according to a second embodiment of the present invention.

[0025] Figure 5 It is a schematic diagram showing the structure of a narrow beam generating device according to a third embodiment of the present invention.

[0026] Figure 6 It is a schematic diagram showing the structure of a narrow beam generating device according to a fourth embodiment of the present invention.

[0027] Figure 7 This is a schematic diagram comparing the effects of eccentricity on the incident light of odd-order aspheric surfaces and even-order aspheric surfaces.

[0028] Figure 8 It is a diagram showing the results of optical simulation of the narrow beam generating device according to the first embodiment.

[0029] Fig. 9It is a diagram showing the results of optical simulation of the narrow beam generating device according to the second embodiment.

[0030] Fig.10 It is a diagram showing the results of optical simulation of the narrow beam generating device according to the third embodiment.

[0031] Fig.11 It is a diagram showing the results of optical simulation of the narrow beam generating device according to the fourth embodiment. DETAILED DESCRIPTION

[0032] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. The content of the present invention is not limited to the description of the following embodiment.

[0033] <<First Implementation Method>>

[0034] <Structure of Narrow Beam Generating Device>

[0035] like Figure 1 As shown, the narrow beam generating device 1 of this embodiment has a light source 2, a collimating optical element 3 as a focusing unit, and an optical element 4. The optical element 4 is an optical element that integrates a convex axis cone surface 41 as a first light focusing unit and a concave axis cone surface 42 as a second light source focusing unit.

[0036] In the present embodiment, the collimating optical element 3 and the optical element 4 are configured so that the optical axes are substantially the same as the optical axis X. In addition, the optical axes of the collimating optical element 3 and the optical element 4 do not necessarily need to be located at the axis center of the optical axis X, and there may be some axis offset. In the narrow beam generating device 1, the narrow beam L1 is generated starting from the position just after the emission from the concave axis cone surface 42 of the optical element 4. In principle, the diameter of the narrow beam L1 is constant regardless of the distance from the emission position, and the length of the narrow beam L1 is infinite in principle.

[0037] The use of the narrow beam generating device 1 capable of generating the above-mentioned narrow beam L1 is not particularly limited, and the narrow beam generating device 1 can be applied to various projector devices, display devices, laser processing devices, lighting devices, optical communication devices, optical storage devices, optical information processing devices, etc. In particular, the size of the beam diameter of the narrow beam L1 can be set to be less than a predetermined size, and it hardly diverges within a predetermined length (in principle to infinity) in the direction of the optical axis X. The beam diameter of the narrow beam L1 is substantially constant regardless of the distance from the emission position, so there is no need to adjust the focus position. Therefore, the narrow beam generating device 1 can be preferably applied to a retinal scanning display. The beam diameter of the narrow beam L1 can be, for example, set to be less than 50 μm, can be set to be less than 20 μm, and can also be set to be less than 10 μm.

[0038] In addition to the above, when the narrow beam generating device 1 is used for photolithography, it is possible to directly draw a high-precision photomask without a precise focusing mechanism. In addition, when the narrow beam generating device 1 is used for a laser processing device, a processing hole with a uniform depth can be formed, compared to the previous laser processing hole that had to be conical. In addition, compared with the previous laser, the energy per unit end face area is very high, so when applied to a shearing device, even a laser oscillator with a smaller output than before can perform sufficient processing. In addition, when the narrow beam generating device 1 is used for sensing technology, high-resolution sensing can be performed without relying on the sensing distance. In addition, when the narrow beam generating device 1 is coupled to an optical fiber, the light input to a single-mode optical fiber, which previously had a coupling efficiency of only about 30%, can be improved to a coupling efficiency of more than 90%.

[0039] The light source 2 is, for example, any light source such as a semiconductor laser (LD), an LED, or a surface light source. There is no particular limitation on the light source 2, and spatial coherence and temporal coherence are not required, so any light source can be used. The light source 2 can also adjust and modulate the light intensity by a light source driver that serves as a power source. As the light source 2, a plurality of light sources emitting light of the same or different wavelengths can also be provided. For example, a plurality of light sources can also be used as a light source after combining RGB light.

[0040] The collimating optical element 3 as a focusing unit is an optical element for the light emitted from the light source 2 to be incident. The collimating optical element 3 converts the incident light into parallel light roughly parallel to the optical axis X and emits it. As the collimating optical element 3 of the focusing unit, collimating lenses, reflectors, diffractive optical elements (DOE), etc. can be cited. The diffractive optical element is an element that has a fine concave-convex structure on the surface, utilizes the diffraction phenomenon of light to branch the light in space, and can output light of a desired pattern and shape. In the case where a plurality of light sources 2 are provided, a plurality of collimating optical elements 3 are provided corresponding to the number of light sources 2. In addition, a collimating optical system is used for a light source with a divergent characteristic, but in a light source without a divergent characteristic, a collimating optical system may not be used, and the light may be incident directly or using a beam expander to match the optical system of the subsequent stage. In addition, as a focusing unit, it is not limited to a unit that generates completely collimated light, as long as it is a focusing unit that focuses the divergent light from the light source to a predetermined solid angle range.

[0041] The optical element 4 is an optical element for incident parallel light generated by the collimating optical element 3. The optical element 4 has a convex axis cone surface 41 as a first light source focusing unit and a concave axis cone surface 42 as a second light source focusing unit having a shape different from that of the convex axis cone surface 41. Both the convex axis cone surface 41 and the concave axis cone surface 42 are refractive surfaces of odd-order aspheric surfaces. The parallel light is incident on the convex axis cone surface 41, and a narrow beam L1 is emitted from the vertex of the concave axis cone surface 42. Figure 1 As shown, the apex of each of the convex axis cone surface 41 and the concave axis cone surface 42 is arranged on the optical axis X. The convex axis cone surface 41 is arranged toward the incident side of the above-mentioned parallel light, and the concave axis cone surface 42 is arranged toward the exit side of the above-mentioned parallel light. The convex axis cone surface 41 and the concave axis cone surface 42 are right circular cone surfaces and right circular cone inner surfaces having the same vertex angle. By setting the first light collecting unit and the second light source collecting unit to the above-mentioned different shapes, it is possible to compactly configure the narrow beam generating device 1 compared to, for example, the case where both the first light collecting unit and the second light source collecting unit are set to convex axis cone surfaces.

[0042] The convex axis cone surface 41 has the function of focusing the parallel light generated by the collimating optical element 3 to an area narrower than the incident light beam. The concave axis cone surface 42 is arranged at the light focusing position of the convex axis cone surface 41. In detail, the vertex of the conical inner surface of the concave axis cone surface 42 is arranged near the farthest position relative to the convex axis cone surface 41 at the focusing position of the parallel light of the convex axis cone surface 41 (Bessel beam generation position). As a result, the outermost light rays of the light beam incident on the convex axis cone surface 41 with a certain degree of expansion are focused by the convex axis cone surface 41, and are focused from the vertex of the concave axis cone surface 42 into a narrow beam L1 parallel to the optical axis X and emitted. In addition, the above-mentioned outermost light rays are concentrated near the optical axis X, so a narrow beam L1 with strong light intensity is emitted.

[0043] In the present embodiment, the optical element 4 is made of a light-transmitting material such as glass, and is an optical element in which a convex cone surface 41 as a first light gathering unit and a concave cone surface 42 as a second light source gathering unit are integrated. In addition to the above, the optical element having the convex cone surface 41 and the optical element having the concave cone surface 42 may be respectively provided as different optical elements, but it is preferred that they are integrated as an optical element like the optical element 4. Thus, compared with the case of providing different optical elements, there is no need to adjust the positions of the convex cone surface 41 and the concave cone surface 42, so that a narrow beam L1 having a desired beam diameter can be generated with high precision. In addition, the structure of the narrow beam generating device 1 can be simplified.

[0044] <Optical simulation results>

[0045] Figure 8 This is a diagram showing the results of optical simulation performed using the narrow beam generating device 1 according to the first embodiment and using optical design software ZEMAX (registered trademark) (manufactured by ZEMAX Development Corporation). Figure 8 The results of the irradiance distribution output by the above optical simulation are shown when detectors are set on a plane perpendicular to the optical axis X at positions where the distance D from the concave axis tapered surface 42 is 100 mm, 500 mm, and 1000 mm, respectively. Figure 8The vertical and horizontal axes of the output result correspond to the detector size (20 μm on one side) (unit: mm), and the center (vertical axis = 0, horizontal axis = 0) corresponds to the position of the optical axis X. Table 1 below shows the details of each structure of the narrow beam generating device 1 of the first embodiment.

[0046] [Table 1]

[0047]

[0048] The aspheric coefficient values ​​in Table 1 are aspheric coefficient values ​​in an aspheric surface shape defined by the following equation (1) (aspheric equation based on a quadratic surface).

[0049] Z={H 2 / R} / [1+{1-(1+k)(H / R) 2} 1 / 2 ]+Σα n H n (1)

[0050] In formula (1), Z represents the displacement (droop) of the surface parallel to the optical axis, H represents the height of the incident light, R represents the radius of curvature of the base surface, K represents the cone constant, and α n It represents the aspheric coefficient of H raised to the nth power. The surface interval (mm) in Table 1 represents the interval to the next surface on the optical axis X in the incident direction. The refractive index in Table 1 refers to the refractive index of the medium on the exit side relative to the refractive index of the medium on the incident side (relative refractive index).

[0051] like Figure 8 As shown, it is clear that the narrow beam generated by the narrow beam generating device 1 maintains a diameter equal to or smaller than a predetermined diameter of about several μm regardless of the distance from the emission position.

[0052] Hereinafter, other embodiments of the present invention will be described. The description of the same configuration as that of the first embodiment may be omitted.

[0053] Second Implementation Method

[0054] <Structure of Narrow Beam Generating Device>

[0055] like Figure 2 As shown, the narrow beam generating device 1a of the second embodiment includes a light source 2, a collimating optical element 3 as a focusing unit, and an optical element 4a. The optical element 4a is composed of an axicon mirror 41a and an axicon mirror 42a. The structure of the narrow beam generating device 1a other than the optical element 4a is the same as that of the narrow beam generating device 1 of the first embodiment.

[0056] The first and second light condensing units of the narrow beam generating device 1a of this embodiment are composed of odd-order aspherical reflective surfaces, thereby generating a narrow beam L2 having stable characteristics that are independent of the wavelength of incident light.

[0057] The axis prism 41a has a concave axis cone surface 41a1 as a first light gathering unit, and the axis prism 42a has a convex axis cone surface 42a1 as a second light gathering unit. The concave axis cone surface 41a1 and the convex axis cone surface 42a1 are both odd-order aspheric reflection surfaces. The parallel light generated by the collimating optical element 3 is incident on the concave axis cone surface 41a1, and the reflected light gathered and reflected by the concave axis cone surface 41a1 is incident on the convex axis cone surface 42a1. In addition, the reflected light gathered and reflected by the convex axis cone surface 42a is gathered and emitted from the hole portion h formed in the axis prism 41a as a narrow beam L2 parallel to the optical axis X.

[0058] like Figure 2 As shown, the apex of each of the concave axis cone surface 41a1 and the convex axis cone surface 42a1 is arranged on the optical axis X. The concave axis cone surface 41a1 is arranged toward the incident side of the parallel light generated by the collimating optical element 3, and the convex axis cone surface 42a1 is arranged between the collimating optical element 3 and the concave axis cone surface 41a1 in a manner opposite to the concave axis cone surface 41a1. The concave axis cone surface 41a1 and the convex axis cone surface 42a1 are right circular cone surfaces or right circular cone inner surfaces having the same vertex angle, and the bottom area of ​​the convex axis cone surface 42a1 is smaller than the bottom area of ​​the concave axis cone surface 41a1.

[0059] The concave cone surface 41a1 has the function of reflecting the parallel light generated by the collimating optical element 3 and focusing it in an area narrower than the incident light beam. The vertex of the convex cone surface 42a1 is arranged at the focusing position of the parallel light of the concave cone surface 41a1. Thus, the outermost light beams incident on the concave cone surface 41a1 with a certain degree of expansion are focused by the concave cone surface 41a1 and are incident on the convex cone surface 42a1. And, from the vertex of the convex cone surface 42a1, as a narrow beam L2 parallel to the optical axis X, they are focused and emitted by reflection. In addition, the above-mentioned outermost light beams are concentrated near the optical axis X, so that a narrow beam L2 with a strong light intensity is emitted.

[0060] like Figure 4A and Figure 4BAs shown, a hole h is formed at a position of the axis prism 41a corresponding to the vertex of the conical inner surface of the concave axis cone surface 41a1. The hole h is a hole through which the narrow beam L2 emitted from the vertex of the convex axis cone surface 42a1 can pass, and the diameter of the hole h has a diameter sufficiently larger than the diameter of the narrow beam L2. The diameter of the hole h is not particularly limited, and for example, it can be a diameter less than the projection shape of the optical axis X direction of the axis prism 42a. According to the above structure, the parallel light generated by the collimating optical element 3 is blocked by the axis prism 42a, so it does not directly reach the hole h, and only the narrow beam L2 gathered by the convex axis cone surface 42a1 reaches the hole h. As a result, the diameter of the narrow beam L2 can be set to a diameter less than a predetermined size. In addition, the hole h is provided in the axis prism 41a, and the narrow beam generating device 1a is configured in such a way that the narrow beam L2 emitted from the axis prism 42a is emitted from the hole h, thereby enabling the narrow beam generating device 1a to be compactly configured.

[0061] <Optical simulation results>

[0062] Fig. 9 This is a diagram showing the results of optical simulation performed using the narrow beam generating device 1 a according to the second embodiment using optical design software ZEMAX (registered trademark) (manufactured by ZEMAX Development Corporation). Fig. 9 The results of the irradiance distribution output by the above optical simulation are shown when detectors are set on a plane perpendicular to the optical axis X at positions where the distance D from the hole h is 100 mm, 500 mm, and 1000 mm, respectively. Fig. 9 The vertical and horizontal axes in the output result correspond to the detector size (20 μm on one side) (unit: mm), and the center (vertical axis = 0, horizontal axis = 0) corresponds to the position of the optical axis X. The vertex angle of the conical inner surface of the concave cone surface 41a1 and the vertex angle of the conical surface of the convex cone surface 42a1 are both 20 degrees, the distance between the vertex angles is 3 mm, the diameter of the bottom surface of the conical inner surface of the concave cone surface 41a1 is 6 mm, and the diameter of the bottom surface of the conical surface of the convex cone surface 42a1 is 1 mm. The following Table 2 shows the details of each structure of the narrow beam generating device 1a of the second embodiment.

[0063] [Table 2]

[0064]

[0065] like Fig. 9 As shown, it is clear that the narrow beam generated by the narrow beam generating device 1 a maintains a diameter equal to or smaller than a predetermined diameter of about several μm regardless of the distance from the emission position.

[0066] 《Third Implementation Mode》

[0067] <Structure of Narrow Beam Generating Device>

[0068] like Figure 5 As shown, the narrow beam generating device 1b of the third embodiment includes a light source 2, a collimating optical element 3 as a focusing unit, a critical angle axicon element 5, and an optical element 4. The structure of the narrow beam generating device 1b other than the critical angle axicon element 5 is the same as that of the narrow beam generating device 1 of the first embodiment.

[0069] The narrow beam generating device 1b involved in the present embodiment is configured by disposing a critical angle axicon element 5 as an annular light focusing unit (annular light focusing element) between the collimating optical element 3 and the optical element 4. In the case where the narrow beam generating device 1b is configured without providing the critical angle axicon element 5 (i.e., in the case of the narrow beam generating device 1 of the first embodiment), the light that contributes to the generation of the narrow beam is only the light near the periphery when viewed from the optical axis X direction of the optical element 4. Therefore, although a narrow beam can be generated, it cannot be said that the utilization efficiency of the incident light is high. The critical angle axicon element 5 of the present embodiment has the following function: to focus the parallel light emitted from the collimating optical element 3 into annular light near the periphery when viewed from the optical axis X direction of the optical element 4 and emit it. Therefore, compared with the narrow beam generating device 1 without the critical angle axicon element 5, the narrow beam generating device 1b can improve the utilization efficiency of the incident light.

[0070] The critical angle axis cone element 5 is composed of an optical element 51 as a first optical element and an optical element 52 as a second optical element, which are arranged in sequence from the incident side. The optical element 51 has a plane 51a on the incident side arranged in such a manner that the parallel light emitted from the collimating optical element 3 is incident vertically, and has a concave axis cone surface 51b as the inner surface of a right circular cone on the exit side. The optical element 52 has a convex axis cone surface 52a on the incident side and a convex axis cone surface 52b on the exit side, and the convex axis cone surface 52a is a right circular cone surface having the same apex angle as the concave axis cone surface 51b. The concave axis cone surface 51b is arranged in contact with the convex axis cone surface 52a. The concave axis cone surface 51b and the convex axis cone surface 52a can also be bonded in a light-transmitting manner, for example, by an adhesive having appropriate optical properties.

[0071] The optical element 51 and the optical element 52 are both composed of a light-transmitting member, but the refractive index of the material constituting the optical element 51 is different from the refractive index of the material constituting the optical element 52. Specifically, as described below, the refractive index of the material constituting the optical element 51 and the optical element 52, and the vertex angles of the concave axis conical surface 51b and the convex axis conical surface 52a are set in such a manner that the light emitted from the optical element 51 propagates along the convex axis conical surface 52a.

[0072] Since the refractive indexes of the materials constituting the optical element 51 and the optical element 52 are different, the light incident from the optical element 51 to the optical element 52 is refracted according to Snell's law at the concave axis cone surface 51b (convex axis cone surface 52a) as the boundary surface. When the refractive index of the material constituting the optical element 51 is set to N, and the refractive index of the material constituting the optical element 52 is set to N', the light incident on the concave axis cone surface 51b at an incident angle θ is refracted at an angle θ' that satisfies the following formula (2). Here, the incident angle θ is approximately equal to 1 / 2 of the vertex angles of the concave axis cone surface 51b and the convex axis cone surface 52a.

[0073] N·sinθ=N'·sinθ' (2)

[0074] Here, when the incident angle θ exceeds the so-called critical angle θc, the light incident from the optical element 51 to the optical element 52 is totally reflected at the concave cone surface 51b (convex cone surface 52a) serving as the boundary surface. However, when the incident angle θ = critical angle θc, the light incident from the optical element 51 to the optical element 52 propagates along the convex cone surface 52a. At this time, the relationship between the refractive index N and the refractive index N' satisfies the following formula (3). In addition, even when the incident angle θ is not strictly consistent with the critical angle θc, as long as the incident angle θ does not exceed the critical angle θc but is an angle very close to the critical angle θc, the light emitted from the optical element 51 can be concentrated in a very narrow area along the convex cone surface 52a.

[0075] N·sin(θc)=N' (3)

[0076] That is, the optical element 51 and the optical element 52 are constructed in such a way that the critical angle θc calculated based on the refractive index of each material constituting the optical element 51 and the optical element 52 is approximately equal to 1 / 2 of the apex angle of the concave axis cone surface 51b and the convex axis cone surface 52a, so that the light emitted from the optical element 51 can propagate along the convex axis cone surface 52a.

[0077] The light propagating along the convex axis conical surface 52a in the optical element 52 is collected by the convex axis conical surface 52b as annular parallel light and emitted. When viewed from the optical axis X direction of the optical element 4, the annular parallel light emitted from the convex axis conical surface 52b is incident near the periphery. As described in the first embodiment, the light incident on the optical element 4 is collected by the convex axis conical surface 41, and is collected from the vertex of the concave axis conical surface 42 as a narrow beam L3 parallel to the optical axis X and emitted.

[0078] <Optical simulation results>

[0079] Fig.10This is a diagram showing the results of optical simulation performed using the narrow beam generating device 1 b according to the third embodiment using optical design software ZEMAX (registered trademark) (manufactured by ZEMAX Development Corporation). Fig.10 The results of the irradiance distribution output by the above optical simulation are shown when detectors are set on a plane perpendicular to the optical axis X at positions where the distance D from the concave axis tapered surface 42 is 100 mm, 500 mm, and 1000 mm, respectively. Fig.10 The vertical and horizontal axes of the output result correspond to the detector size (20 μm on one side) (unit: mm), and the center (vertical axis = 0, horizontal axis = 0) corresponds to the position of the optical axis X. Table 3 below shows the details of each structure of the narrow beam generating device 1b of the third embodiment.

[0080] [Table 3]

[0081]

[0082] like Fig.10 As shown, the beam diameter of the narrow beam generated by the narrow beam generating device 1b is 7.0 μm when the distance D from the emission position is 100 mm, 9.2 μm when the distance D from the emission position is 500 mm, and 12.0 μm when the distance D from the emission position is 1000 mm. Based on this result, it was confirmed that a narrow beam with a diameter of 12 μm or less can be obtained when the distance D from the emission position is at least 1000 mm or less. In addition, it was confirmed that the amount of light forming the above-mentioned narrow beam is 87% of the amount of incident light, and the utilization efficiency of the incident light is improved by about 100 times compared with the narrow beam generating device 1 of the first embodiment.

[0083] 《Fourth Implementation Mode》

[0084] <Structure of Narrow Beam Generating Device>

[0085] like Figure 6 As shown, the narrow beam generating device 1 c of the fourth embodiment includes a light source 2 , a collimating optical element 3 as a light focusing unit, and an optical element 4 b .

[0086] The optical element 4b is composed of an optical element 41b and an optical element 42b. The optical element 41b has a plane 41b1 on the incident side configured so that the parallel light emitted from the collimating optical element 3 is incident vertically, and has a convex axis cone surface 41b2 on the exit side as a right circular cone surface. The optical element 42b has a concave axis cone surface 42b1 on the incident side as the inner surface of a right circular cone having the same apex angle as the convex axis cone surface 41b2, and has an aspherical surface 42b2 on the exit side. The convex axis cone surface 41b2 is configured to abut against the concave axis cone surface 42b1. The convex axis cone surface 41b2 and the concave axis cone surface 42b1 can also be bonded in a light-transmitting manner, for example, by an adhesive having appropriate optical properties.

[0087] The convex axis cone surface 41b2 and the concave axis cone surface 42b1 function as a first light gathering unit. The optical element 4b has a structure similar to the above-mentioned critical angle axis cone element 5. Specifically, the optical element 41b and the optical element 42b are composed of translucent components with different refractive indices, and the optical element 41b and the optical element 42b are constructed so that the critical angle θc calculated based on the refractive index of each material constituting the optical element 41b and the optical element 42b is approximately equal to 1 / 2 of the vertex angle of the convex axis cone surface 41b2 and the concave axis cone surface 42b1. Therefore, the parallel light incident on the optical element 41b from the plane 41b1 propagates along the concave axis cone surface 42b1 in the optical element 42b and is gathered.

[0088] The narrow beam generating device 1c of this embodiment has an aspherical surface 42b2 as a second light collecting unit. The aspherical surface 42b2 is arranged at a position where the light beam is collected by the convex axis conical surface 41b2 and the concave axis conical surface 42b1 as the first light collecting unit. The light collected by the convex axis conical surface 41b2 and the concave axis conical surface 42b1 is collected and emitted from the vertex of the aspherical surface 42b2 as a narrow beam L4 parallel to the optical axis X.

[0089] The aspheric surface 42b2 has an axicon effect and is a refractive surface of an odd-order aspheric surface that introduces a cubic term. By using an odd-order aspheric surface as the second light focusing unit, as described below, it has the advantages of being less susceptible to eccentricity, having a high degree of freedom in design, and being easy to manufacture.

[0090] Figure 7 This is a schematic diagram comparing the effects of eccentricity of incident light when the light is incident on an odd-order aspheric surface and an even-order aspheric surface. The odd-order aspheric surface Zodd and the even-order aspheric surface Zeven are defined by the following equations (4) and (5), respectively. In the following equations (4) and (5), H refers to the incident height.

[0091] Zodd=H+H 3 +H 5 (4)

[0092] Zeven=H 2 +H 4 +H 6 (5)

[0093] like Figure 7 As shown in the figure, when the incident light is decentered by ΔZ along the optical axis X, if the change amount of the incident light on the even-order aspheric surface is expressed as ΔHeven, and the change amount on the odd-order aspheric surface is expressed as ΔHodd, then ΔHeven>ΔHodd is certain, and the change amount on the odd-order aspheric surface is smaller than that on the even-order aspheric surface. Therefore, the odd-order aspheric surface has a smaller sensitivity to decentering than the even-order aspheric surface, and has the advantage of being less susceptible to the influence of decentering.

[0094] The second light gathering unit such as the aspheric surface 42b2 needs to make the light gathered in the narrow area emit in parallel in the same direction. Therefore, the aspheric surface serving as the second light gathering unit needs to be designed so that the amount of shape change remains in a somewhat narrow range. As a shape for realizing the above, an axicon surface can be cited. For example, the shape of the axicon surface is represented by the following formula (6). In the following formula (6), α represents the vertex inclination angle, and H represents the incident height.

[0095] Zaxicon=tan(α)·H (6)

[0096] Since the shape change variance value based on the incident height H is 0, the smaller the shape change variance value is, the closer the shape distribution of the axicon surface is to the characteristics of the axicon surface. Therefore, in order to increase the design freedom and maintain the axicon effect, an odd-order aspheric surface with a smaller shape change variance value is more advantageous than an even-order aspheric surface. In addition, the first differential value of the aspheric shape distribution determines the emission direction of the light, so by reducing the variation of the first differential value, the deviation of the propagation direction of the emitted light can be reduced. Moreover, the odd-order aspheric surface has a shape whose top end is blunter than the axicon surface, so it has the advantage of being easy to manufacture. In particular, the above-mentioned advantage of easy manufacturing of the odd-order aspheric surface that has introduced high-order terms is greater.

[0097] <Optical simulation results>

[0098] Fig.11 This is a diagram showing the results of optical simulation performed using the narrow beam generating device 1 c according to the fourth embodiment using optical design software ZEMAX (registered trademark) (manufactured by ZEMAX Development Corporation). Fig.11 The results of the irradiance distribution are shown when detectors are set on a plane perpendicular to the optical axis X at positions where the distance D from the aspherical surface 42b2 is 100 mm, 500 mm, and 1000 mm, respectively, and the above-mentioned optical simulation outputs the irradiance distribution. Fig.11The vertical and horizontal axes of the output result correspond to the detector size (20 μm on one side) (unit: mm), and the center (vertical axis = 0, horizontal axis = 0) corresponds to the position of the optical axis X. Table 4 below shows the details of each structure of the narrow beam generating device 1c according to the fourth embodiment.

[0099] [Table 4]

[0100]

[0101] like Fig.11 As shown, the beam diameter of the narrow beam generated by the narrow beam generating device 1c has a very small diameter of about 2 μm on any detector. Based on this result, it is confirmed that even when a high-order odd-order aspheric surface is used as the second light focusing unit, a narrow beam having a diameter less than a predetermined size can be generated.

[0102] As mentioned above, although the preferred embodiment of the present invention was described, the content of the present invention is not limited to the above-mentioned embodiment, and can be modified appropriately.

[0103] In the third embodiment, the narrow beam generating device 1b is described as being configured by arranging the critical angle axicon element 5 between the collimating optical element 3 and the optical element 4. This is not limiting. The same effect can be obtained by arranging the critical angle axicon element 5 between the collimating optical element 3 and the optical element 4a of the second embodiment.

[0104] Explanation of symbols

[0105] 1. 1a, 1b, 1c narrow beam generating device;

[0106] 2. Light source;

[0107] 3. Collimating lens (collimating optical system);

[0108] 41, 41a1, 41b2, 42b1 a first light gathering unit;

[0109] 42, 42a1, 42b2 second light gathering unit;

[0110] L1, L2, L3, L4 narrow beam;

[0111] X-ray axis.

Claims

1. A narrow beam generating device, characterized in that: have: light source; a focusing unit for collimating or focusing the divergent light from the light source within a predetermined solid angle range; a first light collecting unit which collects at least a portion of the light emitted from the light collecting unit into a region narrower than the incident light beam; a second light collecting unit, which collects the light emitted from the first light collecting unit into a linear narrow beam; as well as an annular light focusing unit, which is arranged between the light focusing unit and the first light gathering unit, The first light gathering unit and the second light gathering unit are both optical elements or optical systems that are odd-order aspherical surfaces. The second light gathering unit is arranged at a gathering position of the light based on the light of the first light gathering unit, The first light gathering unit and the second light gathering unit have different shapes, The annular light focusing unit is composed of a first optical element and a second optical element arranged in sequence from the incident side. The first optical element has a plane on which light from the light focusing unit is vertically incident and a concave axis cone surface arranged on the exit side. The second optical element has a convex axial cone surface on the incident side.

2. The narrow beam generating device according to claim 1, characterized in that: The first light gathering unit and the second light gathering unit are both composed of optical elements with an axicon effect.

3. The narrow beam generating device according to claim 1 or 2, characterized in that: In the case where the first light gathering unit and the second light gathering unit are both composed of one refractive surface, the first light gathering unit and the second light gathering unit are formed as an integrated element. When both the first light focusing unit and the second light focusing unit have one reflecting surface, a hole is formed on the reflecting surface of the first light focusing unit through which the linear narrow beam focused by the second light focusing unit can pass.

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