Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
  • G01S17/88—Lidar systems specially adapted for specific applications
  • G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
  • G01S17/894—Three-dimensional [3D] imaging with simultaneous measurement of time-of-flight at a two-dimensional [2D] array of receiver pixels, e.g. time-of-flight cameras or flash lidar
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
  • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
  • G01S7/481—Constructional features, e.g. arrangements of optical elements
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B3/00—Simple or compound lenses
  • G02B3/02—Simple or compound lenses with non-spherical faces
  • G02B3/06—Simple or compound lenses with non-spherical faces with cylindrical or toric faces

Definitions

• the present invention relates to an optical system device and an optical element.
• Three-dimensional measurement sensors using the time-of-flight (TOF) method are being adopted for mobile devices, cars, robots, and more. This measures the distance to an object from the time it takes for light irradiated from a light source to be reflected and returned. If the light from the light source is irradiated evenly onto a specified area of the object, the distance at each irradiated point can be measured, and the three-dimensional structure of the object can be detected.
• TOF time-of-flight
• the above sensor system consists of a light irradiation unit that irradiates light onto the target object, a camera unit that detects the light reflected from each point on the target object, and a calculation unit that calculates the distance to the target object from the signal received by the camera.
• the camera section and calculation section can use existing CMOS imagers and CPUs, so the unique part of the above system is the light irradiation section, which consists of a laser and an optical filter.
• the diffusion filter which shapes the beam by passing the laser light through a microlens array and uniformly irradiates the target object over a controlled area, is a distinctive component of the above system.
• Non-Patent Document 1 optical devices utilizing the Lau effect have been known to convert incident light into a dot pattern.
• This is composed of a diffraction grating with a predetermined pitch P and a light source, and is arranged so that the distance L0 between the diffraction grating and the light source satisfies the following formula A, where ⁇ is the wavelength of the light from the light source and n is a natural number of 1 or more.
• a device in which the diffraction grating is replaced with a microlens is under consideration (for example, Patent Document 2).
• the aspheric lens 81 used was a square with a side length of 32 ⁇ m in the planar shape of the XY plane and a height of 21.2 ⁇ m.
• the focal length of the aspheric lens 81 was 50 ⁇ m, but the focal length f 1 of the cross-sectional shape of the aspheric lens 81 in the XZ plane was 10 ⁇ m, and the focal length f 2 of the cross-sectional shape in the YZ plane was 80 ⁇ m.
• Figure 3 shows the results of a simulation of the contrast ratio when the light from the light source is irradiated onto an optical element with ⁇ changed from 10 to 90 ⁇ m in 10 ⁇ m increments.
• the present invention aims to provide an optical system device and optical element that can emit high-contrast light even when emitting a non-circular dot pattern.
• an optical system device of the present invention includes an optical element having a first lens layer having linear first lenses that transmit light of wavelength ⁇ and are periodically arranged, and a second lens layer having linear second lenses that transmit light of wavelength ⁇ and are periodically arranged, arranged in a direction perpendicular to the first lenses, and an irradiation unit having a light source that irradiates a plurality of the first lenses and second lenses with light of wavelength ⁇ , wherein m and n are natural numbers of 1 or more, a focal length of the first lens is f 1 , a focal length of the second lens is f 2 , a magnitude of the pitch of the first lenses is P 1 , and a magnitude of the pitch of the second lenses is P 2 , and a distance L 1 between the irradiation unit and a first focal plane of the first lens and a distance L 2 between the irradiation unit and a second focal plane of the second lens are expressed by the following formulas 1 and 2:
• the present invention is
• the distance between the first focal plane and the second focal plane of the optical element is within 10 ⁇ m, and it is even more preferable that the first focal plane and the second focal plane are in the same position.
• the optical element may also include an intermediate layer between the first lens layer and the second lens layer, the intermediate layer having a lower refractive index than the materials of the first lens layer and the second lens layer.
• the optical element may also include a substrate on the side of the second resin layer opposite the first resin layer.
• the distances L 1 and L 2 are expressed by the following formulas 3 and 4. It is preferable to satisfy the following.
• the optical system device and optical element of the present invention can emit light with high contrast.
• FIG. 13 is a diagram showing the orientation distribution at the far end of the irradiation unit used in the simulation.
• FIG. 1A is a schematic cross-sectional view showing a conventional optical system device
• FIG. 1B is a perspective view showing an aspheric lens.
• 1 is a graph showing the contrast of a conventional optical system device.
• 1 is a projection diagram of a dot pattern of a conventional optical system device.
• 1 is a schematic cross-sectional view showing an optical system device of the present invention.
• FIG. 1 is a perspective view showing an optical element of the present invention.
• FIG. 2 is a perspective view showing another optical element of the present invention.
• 1A and 1B are schematic cross-sectional views showing an optical system device of the present invention, and FIG.
• FIG. 1C is a perspective view showing a first lens and FIG. 4 is a projection diagram of a dot pattern of the optical system device of the present invention.
• 3A to 3C are schematic cross-sectional views illustrating a method for producing an optical element of the present invention.
• 5A to 5C are schematic cross-sectional views illustrating a method for producing another optical element of the present invention.
• the optical system device of the present invention will be described below. As shown in FIG. 5, the optical system device of the present invention is mainly composed of an optical element 1 and an irradiation unit 2.
• the optical element 1 is mainly composed of a first lens layer 110 and a second lens layer 120.
• the first lens layer 110 transmits light of wavelength ⁇ and has periodically arranged linear first lenses 11. As shown in Fig. 5(a) , the first lenses 11 have a focal point that is spaced a focal length f1 ( f1 >0) from the side where the second lens layer 120 is not present.
• the second lens layer 120 has linear second lenses 12 that transmit light of wavelength ⁇ and are periodically arranged.
• the second lenses 12 are arranged so that the line direction is perpendicular to the line direction of the first lenses 11.
• the second lenses 12 have a focal point that is a focal length f2 ( f1 >0) away from the focal point on the first lens layer 110 side.
• the focal length means the distance between the lens surface closest to the focal point and the focal point, as shown in Fig. 5 .
• the first lens 11 and the second lens 12 may have any shape as long as they can focus light in a line shape, and for example, a lenticular lens may be used.
• the first lens 11 and the second lens 12 may be a Fresnel lens, a DOE lens, a metalens, or the like, as long as they can focus light in a line shape.
• the first lens 11 and the second lens 12 may be formed with an anti-reflection coating that prevents the light from the irradiation unit 2 from reflecting.
• the first lens layer 110 is made of a material having a higher refractive index than the material on the side where light enters the first lens 11.
• the second lens layer 120 is made of a material having a higher refractive index than the material on the side where light enters the first lens 11. Therefore, when the first lens layer 110 and the second lens layer 120 are formed adjacent to each other, the first lens layer 110 needs to have a lower refractive index than the second lens layer 120. However, if the difference in refractive index between the first lens layer 110 and the air is small, it may be difficult to expand the dot pattern to a wide angle. In such a case, as shown in FIG.
• an intermediate layer 130 having a lower refractive index than the materials of the first lens layer 110 and the second lens layer 120 may be provided between the first lens layer 110 and the second lens layer 120.
• the intermediate layer 130 may be made of a resin, but it is also possible to use a gas such as air or to create a vacuum.
• the optical element 1 may have a substrate or the like on the side of the second resin layer opposite the first resin layer for manufacturing reasons or the like.
• the substrate may be made of any material that transmits light of wavelength ⁇ , but it is preferable that the substrate be made of a material that has a lower refractive index than the first lens 11 and the second lens 12.
• the irradiation unit 2 has a light source 7 that irradiates the first lens 11 and the second lens 12 with light of wavelength ⁇ . Any light source 7 that irradiates the first lens 11 and the second lens 12 with light of wavelength ⁇ may be used.
• the irradiation unit 2 may be a single light source or multiple light sources.
• the irradiation unit 2 may be a multiple light source by passing the light of a single light source through an aperture having multiple pores. When the irradiation unit 2 is composed of multiple light sources, it is preferable that the light sources are formed on the same plane.
• a specific example of the irradiation unit 2 is a VCSEL (Vertical Cavity Surface Emitting LASER), which is expected to achieve high output with low power.
• the VCSEL has multiple light sources 7 that can irradiate light in a direction perpendicular to the light emitting surface. It is also preferable that a light absorbing film is formed on parts other than the light source 7, because noise due to reflected light is not introduced.
• the irradiation unit 2 When the irradiation unit 2 has a plurality of light sources 7, they need to be arranged so that the number of light sources 7 for each first lens 11 of the optical element 1 and the number of light sources 7 for each second lens 12 of the optical element 1 are the same in a planar view even when the irradiation unit 2 and the optical element 1 are moved in parallel relative to each other. Therefore, when j is a natural number of 1 or more, the irradiation unit 2 may arrange the light sources 7 regularly with a pitch of jP1 or P1 /j in the periodic direction of the first lenses 11 of the optical element 1. Similarly, when k is a natural number of 1 or more, the irradiation unit 2 may arrange the light sources 7 regularly with a pitch of kP2 or P2 /k in the periodic direction of the second lenses 12 of the optical element 1.
• the optical system device can convert the incident light into a dot pattern with high contrast when the distance L1 between the irradiation unit 2 and the first focal plane 111 of the lens 11 and the distance L2 between the irradiation unit 2 and the second focal plane 112 satisfy the following formulas ⁇ and ⁇ .
• m and n are natural numbers of 1 or more
• P1 is the pitch size of the first lens 11
• P2 is the pitch size of the second lens 12
• ⁇ is the wavelength of the light incident from the irradiation unit 2
• f1 is the focal length of the first lens 11
• f2 is the focal length of the second lens 12
• a, b, c, and d are coefficients indicating allowable errors.
• the first focal plane 111 means a plane perpendicular to the optical axis (z direction) of the first lens 11 and at the focal position of the first lens 11.
• the second focal plane 121 means a plane perpendicular to the optical axis (z direction) of the second lens 12 and at the focal position of the second lens 12.
• the first lens 11 and the second lens 12 are formed so that the first focal plane 111 and the second focal plane 121 are parallel to each other.
• the distances L1 and L2 refer to the distance (optical path length) that light travels in a vacuum in the same time that it travels in a medium, and are expressed as the product NL, where N is the refractive index of the medium and L is the actual distance.
• the distances L 1 and L 2 are expressed by the following formulas 3 and 4: It is better to satisfy.
• the distance between the first focal plane 111 and the second focal plane 121 of the optical element 1 is within 10 ⁇ m, since this makes it easier to simultaneously satisfy formulas 1 and 2 or formulas 3 and 4. It is also more preferable that the first focal plane 111 and the second focal plane 121 are in the same position.
• the optical element 1 transmits light with a wavelength ⁇ , and has a first lens layer 110 having a linear first lens 11 and a second lens layer 120 having linear second lenses 12 arranged in a direction (X direction) perpendicular to the line direction (Y direction) of the first lens 11, with an intermediate layer 130 sandwiched therebetween, as shown in FIG. 8(a) and (b).
• the intermediate layer 130 has a refractive index of 1.42.
• Figure 9 shows the projection diagram resulting from the simulation. As shown in Figure 8, the dots became very sharp and circular. In addition, the contrast was 123.2, which shows that the contrast can be improved significantly compared to conventional methods.
• optical element manufacturing method The following describes a method for manufacturing the optical element 1.
• the first lens 11 and the second lens 12 of the optical element 1 may be manufactured in any manner, but may be manufactured, for example, by using an imprint method.
• the second lens 12 is formed on the substrate 9 using a known technique such as an imprint method (second lens formation step).
• a known technique such as an imprint method
• the material 120a of the second lens 12 is applied to the substrate 9 with a predetermined thickness by a known method such as a spin coater (first application step).
• Any material 120a may be used as long as it can form the second lens 12 that transmits light of wavelength ⁇ , and for example, photocurable polydimethylsiloxane (PDMS) can be used.
• PDMS photocurable polydimethylsiloxane
• a second mold 52 having a second lens pattern that is an inverted shape of the second lens 12 is prepared, and the applied material of the second lens 12 is pressed to transfer the second lens pattern (first transfer step).
• the applied pattern is cured by irradiating UV light or the like (first curing step).
• the second mold 52 is released to form the second lens 12 on the substrate 9.
• the first lens 11 is formed on the second lens 12 using a known technique such as an imprint method (first lens formation process).
• a material 110a of the first lens 11 is applied to a predetermined thickness on the second lens 12 by a known method such as a spin coater (second application process). Any material 110a may be used as long as it can form the first lens 11 that transmits light of wavelength ⁇ , and photocurable polydimethylsiloxane (PDMS) can be used, for example.
• PDMS photocurable polydimethylsiloxane
• FIG. 10(f) a first mold 51 having a first lens pattern that is an inverted shape of the first lens 11 is prepared, and the applied material of the first lens 11 is pressed to transfer the first lens pattern (second transfer process). In addition, the applied pattern is cured by irradiating UV light or the like (second curing process).
• the first mold 51 is released, and the first lens 11 can be formed on the second lens 12.
• an intermediate layer 130 or the like is formed on the second lens 12, and then form the first lens 11 on top of that.
• a material 130a for the intermediate layer 130 is applied to a predetermined thickness on the second lens 12 by a well-known method such as a spin coater (intermediate layer application process).
• the material 130a is then hardened by irradiation with UV light or the like to form the intermediate layer 130 (intermediate layer hardening process).
• the first lens 11 is formed on the intermediate layer 130 using a known technique such as an imprinting method (first lens forming step).
• first lens forming step the material of the first lens 11 is applied to a predetermined thickness on the intermediate layer 130 by a known method such as a spin coater (second application step). Any material may be used as long as it can form the first lens 11 that transmits light of wavelength ⁇ , and photocurable polydimethylsiloxane (PDMS) can be used, for example.
• PDMS photocurable polydimethylsiloxane
• FIG. 11(f) a first mold 51 having a first lens pattern that is an inverted shape of the first lens 11 is prepared, and as shown in FIG.
• pressure is applied to the applied material of the first lens 11 to transfer the first lens pattern (second transfer step). Also, UV light or the like is irradiated to harden the applied pattern (second hardening step). Next, as shown in FIG. 11(h), the first mold 51 is released, and the first lens 11 can be formed on the second lens 12.
• first lens 11 and the second lens 12 are formed so that the distance between the focal plane 111 of the first lens 11 and the focal plane 121 of the second lens 12 is within 10 ⁇ m, and more preferably, they are in the same position.

Landscapes

• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Computer Networks & Wireless Communication (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Optics & Photonics (AREA)
• Electromagnetism (AREA)
• Diffracting Gratings Or Hologram Optical Elements (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=91084668

Family Applications (1)

Country Status (2)

Cited By (1)

Citations (5)

• 2023
  • 2023-11-13 JP JP2023580950A patent/JPWO2024106359A1/ja active Pending
  • 2023-11-13 WO PCT/JP2023/040683 patent/WO2024106359A1/ja not_active Ceased

Patent Citations (5)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events