US-20260126666-A1 - BESSEL BEAM GENERATION DEVICE AND OPTICAL SCANNING DEVICE USING SAME

Abstract

The modified Bessel beam generating device that achieves design flexibility is provided. The present invention provides a Bessel beam generating device that splits a laser beam emitted from a single light source and causes diverging light in a donut shape from optical fibers arranged on the same circle to be emitted toward the inside, thereby emitting a disk illumination beam that is focused in the vicinity of the center. This makes it possible to generate a disk illumination beam without blocking the high-intensity central portion and without reducing the light intensity.

Inventors

• Hiroshi Ogawa

Assignees

• Hiroshi Ogawa

Dates

Publication Date

20260507

Application Date

20230427

Priority Date

20220427

Claims (5)

1. 1 - 8 . (canceled)
2. 9 : A modified Bessel beam generating device, comprising: a light source that emits a laser beam; an optical fiber into which the laser beam emitted from the light source is introduced; and a lens that, by adjusting the light flux of an irradiation beam emitted from the optical fiber, produces diverging light having a ring-shaped cross-section with a hollow center that travels toward the inside of the ring and emits it from the optical fiber as a disk illumination beam; wherein the lens includes a reflective lens that reflects the incident laser light outward from the optical axis, and a reflective cover portion arranged to cover the reflective lens and that reflects the laser light traveling outward toward the inside; and wherein the reflective cover portion inverts the laser light traveling outward such that light located on the inner side becomes outer and light located on the outer side becomes inner; whereby a Bessel beam generating device is provided.
3. 10 : The modified Bessel beam generating device according to claim 9 , wherein the reflective lens is a rotationally symmetric conical reflector whose generatrix is linear or curved and that reflects the incident laser light outward from the optical axis, and the reflective cover portion is arranged to cover the conical reflector and re-reflects the reflected wave from the conical reflector with a surface that is a portion cut out from a spherical surface, an ellipsoidal surface, or a higher-order parabolic surface, or a free-form surface, such that light of higher intensity overlaps at a farther position to form a focus.
4. 11 : The modified Bessel beam generating device according to claim 10 , wherein the reflective cover portion has a surface formed by rotating an ellipse or a parabola about the optical axis, which re-reflects the reflected wave.
5. 12 : An optical scanning device, comprising: a light source that emits a laser beam; an optical fiber into which the laser beam emitted from the light source is introduced; a lens (including a reflective lens and a reflective cover portion) that, by adjusting the light flux of the irradiation beam emitted from the optical fiber, produces diverging light having a ring-shaped cross-section with a hollow center that travels toward the inside of the ring and emits it as a disk illumination beam, the lens including a reflective lens that reflects the incident laser light outward from the optical axis and a reflective cover portion that is arranged to cover the reflective lens and reflects the laser light traveling outward toward the inside; a light receiving unit that receives return light when the disk illumination beam is irradiated onto a measurement target and converts it into an electrical signal; and an analysis unit that calculates the position of a reflection point of the measurement target by analyzing the electrical signal; wherein the reflective cover portion inverts the laser light traveling outward such that light located on the inner side goes outward and light located on the outer side goes inward.

Description

TECHNICAL FIELD The present invention relates to, for example, a Bessel beam generating device having a large depth of focus, and an optical scanning device using the same. BACKGROUND ART Conventionally, an OCT (Optical Coherence Tomography) apparatus that generates a Bessel beam using an axicon lens is known (see, for example, Patent Document 1). CITATION LIST Patent Literature PTL1: Japanese Patent No. 5680776 SUMMARY OF INVENTION Technical Problem However, in an OCT apparatus of such a configuration, because an axicon lens is used, the focal length from the axicon lens to the focus is restrictively short, requiring the distance to the object being irradiated to be set short. This imposes limitations on the design. The present invention has been made to solve the above problem, and an object of the invention is to provide a Bessel beam generating device and an optical scanning device using the same that can improve design freedom (design flexibility). Solution to the Problem To achieve the above object, a Bessel beam generating device according to the present invention is characterized by comprising: a group of at least four light emitters arranged at equal intervals on the same circle such that light is emitted from the tip of an optical waveguide portion, with the optical axis of the light emitted from each said light emitter maintained at the same angle with respect to the diameter direction of the circle; an entrance portion that splits a laser beam emitted from a single light source and causes the split beams to enter each of the optical waveguide portions; and an optical waveguide portion having a function to make the phase and amplitude of the emitted light from each said light emitter identical. Further, an optical scanning device according to the present invention is characterized by comprising: a group of at least four light emitters arranged at equal intervals on the same circle such that light is emitted from the tip of an optical waveguide portion, with the optical axis of the light emitted from each said light emitter maintained at the same angle with respect to the diameter direction of the circle; an entrance portion that splits a laser beam emitted from a single light source and causes the split beams to enter each of the optical waveguide portions; an optical waveguide portion having a function to make the phase and amplitude of the emitted light from each said light emitter identical; a light receiving unit that receives return light of the emitted light (reflected from the measurement object) and converts it into an electrical signal; and an analysis unit that calculates the position of a reflection point of the measurement object by analyzing the electrical signal. Furthermore, a Bessel beam generating device according to the present invention is characterized by comprising: a rotationally symmetric conical reflector whose generatrix is linear or curved with respect to the optical axis such that an incident laser beam is reflected outward relative to the optical axis; and a reflective cover portion arranged to cover the conical reflector, which re-reflects the wave reflected by the conical reflector using an elliptical surface main mirror having the optical axis as its axis of rotational symmetry. An optical scanning device according to the present invention is characterized by comprising: a light source that emits a laser beam; a reflective lens on which the laser beam from the light source is incident and which reflects the laser beam outward from the optical axis; a reflective cover portion arranged to cover the reflective lens and that reflects the laser beam traveling outward toward the inside, thereby projecting a disk-shaped illumination beam; a light receiving unit that receives return light from the disk illumination beam and converts it into an electrical signal; and an analysis unit that calculates the position of a reflection point of the measurement object by analyzing the electrical signal. Advantageous Effects According to the present invention, it is possible to realize a Bessel beam generating device and an optical scanning device using the same that can improve design flexibility. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic diagram illustrating the configuration (1) of a Bessel beam generating device in the first embodiment. FIG. 2 is a schematic diagram illustrating the configuration (2) of the Bessel beam generating device in the first embodiment. FIG. 3 is a schematic diagram for explaining the laser light emitted from an optical fiber. FIG. 4 is a schematic diagram illustrating the configuration (3) of the Bessel beam generating device in the first embodiment. FIG. 5 is a schematic diagram for explaining (1) the focusing of the Bessel beam generating device in the first embodiment. FIG. 6 is a schematic diagram for explaining movement of the focus of the Bessel beam generating device in the first embodiment in a plane direction. FIG. 7 is a schematic diag