Optical devices and optical systems

Abstract

To provide a new optical device and optical system.SOLUTION: An optical device includes a light emitting portion, a first magnetic element, and a circuit, the first magnetic element includes a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, the first magnetic element is irradiated with reflected light emitted by the light emitting portion and reflected by an object to be irradiated, a first signal corresponding to the light emission from the light emitting portion is input to the circuit, and a second signal corresponding to the irradiation of the first magnetic element with the reflected light is input from the first magnetic element to the circuit.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to optical devices and optical systems. [Background technology]

[0002] Photoelectric conversion elements are used for a variety of purposes.

[0003] For example, Patent Document 1 describes a distance measuring device that receives reflected light from a reflector with a photodiode and measures the distance to the target object, which is the reflector. This distance measuring device uses LiDAR (Light Detection and Ranging) technology. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-128084 Summary of the Invention [Problem to be solved by the invention]

[0005] Optical sensors using semiconductor pn junctions are widely used, but new breakthroughs are needed for further development.

[0006] The present invention has been made in view of the above problems, and has an object to provide a novel optical device and optical system. [Means for solving the problem]

[0007] In order to solve the above problems, the following means are provided.

[0008] (1) An optical device according to a first aspect includes a light emitting unit, a first magnetic element, and a circuit, wherein the first magnetic element includes a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, wherein the first magnetic element is irradiated with light emitted by the light emitting unit and reflected by an irradiated object, a first signal corresponding to the light emitted by the light emitting unit is input to the circuit, and a second signal corresponding to the irradiation of the reflected light onto the first magnetic element is input from the first magnetic element to the circuit.

[0009] (2) In the optical device according to the above aspect, the first signal may be input from the light emitting unit to the circuit.

[0010] (3) The optical device according to the above aspect may further include a second magnetic element, the second magnetic element including a third ferromagnetic layer, a fourth ferromagnetic layer, and a second spacer layer sandwiched between the third ferromagnetic layer and the fourth ferromagnetic layer, the second magnetic element being irradiated with a portion of the light emitted by the light-emitting portion, and the first signal being input to the circuit from the second magnetic element.

[0011] (4) In the optical device according to the above aspect, the first magnetic element may also be irradiated with a portion of the light emitted by the light emitting portion, and the first signal may be input to the circuit from the first magnetic element.

[0012] (5) The optical device according to the above aspect may further include an optical scanning mirror, wherein at least a portion of the light emitted by the light emitting unit is reflected by the optical scanning mirror and irradiated onto the irradiated body, and the reflected light from the irradiated body is reflected by the optical scanning mirror and irradiated onto the first magnetic element.

[0013] (6) An optical system according to a second aspect has an optical device according to the above aspect, and calculates the time difference between the light emission of the light-emitting unit and the irradiation of the reflected light onto the first magnetic element based on the first signal and the second signal input to the circuit.

[0014] (7) The optical system according to the above aspect may determine the distance between the object to be illuminated and the optical device based on the time difference.

[0015] (8) An optical system according to a third aspect includes the optical device according to the above aspect, and obtains a three-dimensional image of the object to be illuminated from the reflected light. [Effects of the Invention]

[0016] The optical device and optical system according to the above aspects operate on a novel principle. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of an optical system according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the first magnetic element according to the first embodiment. [Figure 3] 5A and 5B are diagrams for explaining a first mechanism of operation of the first magnetic element according to the first embodiment. [Figure 4] 6A and 6B are diagrams for explaining a second mechanism of operation of the first magnetic element according to the first embodiment. [Figure 5] 3A and 3B are diagrams illustrating examples of a first signal and a second signal in the optical system according to the first embodiment. [Figure 6] FIG. 4 is a diagram showing a change over time in an output voltage from a first magnetic element in the optical system according to the first embodiment. [Figure 7] FIG. 4 is a diagram showing a change over time in an output voltage from a first magnetic element in the optical system according to the first embodiment. [Figure 8] FIG. 10 is a schematic diagram of an optical system according to a second embodiment. [Figure 9] FIG. 10 is a cross-sectional view of a second magnetic element according to a second embodiment. [Figure 10] 10A and 10B are diagrams illustrating examples of a first signal and a second signal in an optical system according to a second embodiment. [Figure 11] FIG. 10 is a schematic diagram of an optical system according to a third embodiment. [Figure 12]10A and 10B are diagrams illustrating examples of a first signal and a second signal in an optical system according to a third embodiment. [Figure 13] FIG. 10 is a schematic diagram of an optical system according to a fourth embodiment. [Figure 14] FIG. 10 is a schematic diagram of an optical system according to a fifth embodiment. [Figure 15] FIG. 10 is a schematic diagram of an optical system according to a sixth embodiment. [Figure 16] FIG. 1 is a schematic diagram of an application example of an optical system. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, the embodiments will be described in detail with reference to the drawings as appropriate. The drawings used in the following description may show characteristic portions enlarged for convenience in order to make the features easier to understand, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate changes can be made within the scope of the effects of the present invention.

[0019] The directions are defined as follows. The stacking direction of the first magnetic element 2 is the z direction, one direction in a plane perpendicular to the z direction is the x direction, and the direction perpendicular to the x and z directions is the y direction. Hereinafter, the +z direction may be expressed as "up" and the -z direction as "down". The +z direction is the direction from the second electrode E2 to the first electrode E1. Up and down do not necessarily coincide with the direction in which gravity is applied.

[0020] "First embodiment" FIG. 1 is a schematic diagram of an optical system 100 according to a first embodiment. The optical system 100 includes, for example, an optical device 10 and an external device 90. The optical system 100 obtains the distance to the irradiated object Ob, a three-dimensional image of the irradiated object Ob, and the like, using light emitted from a light-emitting unit 1 of the optical device 10 (hereinafter referred to as light L1) and light reflected from the irradiated object Ob (hereinafter referred to as reflected light L2). The light L1 is emitted light from the light-emitting unit 1.

[0021] In this specification, light is not limited to visible light, but also includes infrared light, which has a longer wavelength than visible light, and ultraviolet light, which has a shorter wavelength than visible light. The wavelength of visible light is, for example, 380 nm or more and less than 800 nm. The wavelength of infrared light is, for example, 800 nm or more and 1 mm or less. The wavelength of ultraviolet light is, for example, 200 nm or more and less than 380 nm.

[0022] The optical device 10 includes, for example, a light emitting unit 1, a first magnetic element 2, a circuit 3, an external interface 4, and lenses R1 and R2.

[0023] The light-emitting unit 1 has a laser light source. The light-emitting unit 1 is connected to a power source during use. The power source may be inside the light-emitting unit 1. The laser light source emits pulsed laser light of a predetermined duration at a predetermined cycle. The light L1 emitted by the light-emitting unit 1 is collimated by a lens R1. The light L1 is irradiated onto the object to be irradiated Ob. The lens R1 is, for example, a collimator lens.

[0024] The first magnetic element 2 is irradiated with reflected light L2 emitted by the light-emitting unit 1 and reflected by the irradiated object Ob. The first magnetic element 2 may be one or more. For example, a plurality of first magnetic elements 2 may be arranged one-dimensionally or two-dimensionally along a plane intersecting the irradiation direction of the reflected light L2, and the reflected light L2 may be irradiated onto the arranged plurality of first magnetic elements 2. The reflected light L2 is collected by a lens R2 and irradiated onto the first magnetic element 2. The lens R2 is, for example, a focus lens. To prevent ambient light from entering through the lens R2 and irradiating the first magnetic element 2, a wavelength filter that cuts ambient light may be provided on the optical path of the reflected light L2 immediately before the lens R2 or between the lens R2 and the first magnetic element 2.

[0025] Fig. 2 is a cross-sectional view of the first magnetic element 2 according to the first embodiment. In Fig. 2, the direction of magnetization of the ferromagnetic material in the initial state is indicated by an arrow.

[0026] The first magnetic element 2 includes at least a first ferromagnetic layer 21, a second ferromagnetic layer 22, and a spacer layer 23. The spacer layer 23 is located between the first ferromagnetic layer 21 and the second ferromagnetic layer 22. The first magnetic element 2 may also include a buffer layer 24, a seed layer 25, a ferromagnetic layer 26, a magnetic coupling layer 27, a perpendicular magnetization induction layer 28, a cap layer 29, and an insulating layer 30. The buffer layer 24, the seed layer 25, the ferromagnetic layer 26, and the magnetic coupling layer 27 are located between the second ferromagnetic layer 22 and the second electrode E2, and the perpendicular magnetization induction layer 28 and the cap layer 29 are located between the first ferromagnetic layer 21 and the first electrode E1. The insulating layer 30 is located between the first electrode E1 and the second electrode E2 and covers the periphery of the stack 20.

[0027] The first magnetic element 2 is, for example, an MTJ (Magnetic Tunnel Junction) element in which the spacer layer 23 is made of an insulating material. The resistance value of the first magnetic element 2 changes when irradiated with external light. The resistance value of the first magnetic element 2 in the z direction (the resistance value when a current flows in the z direction) changes according to the relative change between the state of magnetization M21 of the first ferromagnetic layer 21 and the state of magnetization M22 of the second ferromagnetic layer 22. Such an element is also called a magnetoresistance effect element.

[0028] The first ferromagnetic layer 21 is a light detection layer whose magnetization state changes when irradiated with external light. The first ferromagnetic layer 21 is also called a magnetization free layer. The magnetization free layer is a layer containing a magnetic material whose magnetization state changes when predetermined external energy is applied. The predetermined external energy is, for example, light irradiated from the outside, a current flowing in the stacking direction of the first magnetic element 2, or an external magnetic field. The state of the magnetization M21 of the first ferromagnetic layer 21 changes depending on the intensity of the irradiated light.

[0029] The first ferromagnetic layer 21 includes a ferromagnetic material. The first ferromagnetic layer 21 includes at least one of magnetic elements such as Co, Fe, or Ni. The first ferromagnetic layer 21 may include elements such as B, Mg, Hf, or Gd in addition to the magnetic elements described above. The first ferromagnetic layer 21 may be, for example, an alloy including a magnetic element and a non-magnetic element. The first ferromagnetic layer 21 may be composed of multiple layers. The first ferromagnetic layer 21 may be, for example, a CoFeB alloy, a stacked body in which a CoFeB alloy layer is sandwiched between Fe layers, or a stacked body in which a CoFeB alloy layer is sandwiched between CoFe layers. Generally, the term "ferromagnetic" includes "ferrimagnetic." The first ferromagnetic layer 21 may exhibit ferrimagnetic properties. On the other hand, the first ferromagnetic layer 21 may exhibit ferromagnetic properties that are not ferrimagnetic. For example, a CoFeB alloy exhibits ferromagnetic properties that are not ferrimagnetic.

[0030] The first ferromagnetic layer 21 may be an in-plane magnetization film having an axis of easy magnetization in the in-plane direction (any direction in the xy plane) or a perpendicular magnetization film having an axis of easy magnetization in the direction perpendicular to the film plane (z direction).

[0031] The thickness of the first ferromagnetic layer 21 is, for example, 1 nm or more and 5 nm or less. The thickness of the first ferromagnetic layer 21 is preferably, for example, 1 nm or more and 2 nm or less. When the first ferromagnetic layer 21 is a perpendicular magnetization film, if the thickness of the first ferromagnetic layer 21 is small, the effect of perpendicular magnetic anisotropy applied from the layers above and below the first ferromagnetic layer 21 is strengthened, and the perpendicular magnetic anisotropy of the first ferromagnetic layer 21 is increased. In other words, if the perpendicular magnetic anisotropy of the first ferromagnetic layer 21 is high, the force that returns the magnetization M21 to the z-direction is strengthened. On the other hand, if the thickness of the first ferromagnetic layer 21 is large, the effect of perpendicular magnetic anisotropy applied from the layers above and below the first ferromagnetic layer 21 is relatively weaker, and the perpendicular magnetic anisotropy of the first ferromagnetic layer 21 is weakened.

[0032] As the thickness of the first ferromagnetic layer 21 decreases, its volume as a ferromagnetic body decreases, and as it increases, its volume as a ferromagnetic body increases. The responsiveness of the magnetization of the first ferromagnetic layer 21 when external energy is applied is inversely proportional to the product (KuV) of the magnetic anisotropy (Ku) and the volume (V) of the first ferromagnetic layer 21. In other words, as the product of the magnetic anisotropy and the volume of the first ferromagnetic layer 21 decreases, the responsiveness to light increases. From this perspective, in order to improve the responsiveness to light, it is preferable to reduce the volume of the first ferromagnetic layer 21 after appropriately designing the magnetic anisotropy of the first ferromagnetic layer 21.

[0033] If the thickness of the first ferromagnetic layer 21 is greater than 2 nm, an insertion layer made of, for example, Mo or W may be provided within the first ferromagnetic layer 21. That is, the first ferromagnetic layer 21 may be a stack in which a ferromagnetic layer, an insertion layer, and a ferromagnetic layer are stacked in this order in the z direction. The interfacial magnetic anisotropy at the interface between the insertion layer and the ferromagnetic layer enhances the perpendicular magnetic anisotropy of the entire first ferromagnetic layer 21. The thickness of the insertion layer is, for example, 0.1 nm to 1.0 nm.

[0034] The second ferromagnetic layer 22 is a magnetization fixed layer. The magnetization fixed layer is a layer made of a magnetic material whose magnetization state is less likely to change when a predetermined external energy is applied than the magnetization free layer. For example, the magnetization direction of the magnetization fixed layer is less likely to change when a predetermined external energy is applied than the magnetization free layer. Also, for example, the magnitude of the magnetization of the magnetization fixed layer is less likely to change when a predetermined external energy is applied than the magnetization free layer. The coercive force of the second ferromagnetic layer 22 is, for example, greater than the coercive force of the first ferromagnetic layer 21. The second ferromagnetic layer 22 has an easy axis of magnetization in the same direction as the first ferromagnetic layer 21, for example. The second ferromagnetic layer 22 may be an in-plane magnetization film or a perpendicular magnetization film.

[0035] The material constituting the second ferromagnetic layer 22 is, for example, the same as that of the first ferromagnetic layer 21. The second ferromagnetic layer 22 may be, for example, a multilayer film in which Co layers having a thickness of 0.4 nm to 1.0 nm and Pt layers having a thickness of 0.4 nm to 1.0 nm are alternately stacked several times. The second ferromagnetic layer 22 may be, for example, a laminate in which Co layers having a thickness of 0.4 nm to 1.0 nm, Mo layers having a thickness of 0.1 nm to 0.5 nm, a CoFeB alloy layers having a thickness of 0.3 nm to 1.0 nm, and Fe layers having a thickness of 0.3 nm to 1.0 nm are stacked in this order.

[0036] The magnetization of the second ferromagnetic layer 22 may be fixed by, for example, magnetic coupling with the ferromagnetic layer 26, which sandwiches the magnetic coupling layer 27. In this case, the combination of the second ferromagnetic layer 22, the magnetic coupling layer 27, and the ferromagnetic layer 26 may be referred to as a magnetization fixed layer. Details of the magnetic coupling layer 27 and the ferromagnetic layer 26 will be described later.

[0037] The spacer layer 23 is a layer disposed between the first ferromagnetic layer 21 and the second ferromagnetic layer 22. The spacer layer 23 is a layer made of a conductor, an insulator, or a semiconductor, or a layer containing current-carrying points made of a conductor in an insulator. The spacer layer 23 is, for example, a non-magnetic layer. The film thickness of the spacer layer 23 can be adjusted depending on the orientation directions of the magnetizations of the first ferromagnetic layer 21 and the second ferromagnetic layer 22 in the initial state, which will be described later.

[0038] When the spacer layer 23 is made of an insulating material, a material containing aluminum oxide, magnesium oxide, titanium oxide, silicon oxide, or the like can be used as the material of the spacer layer 23. These insulating materials may also contain elements such as Al, B, Si, and Mg, or magnetic elements such as Co, Fe, and Ni. A high magnetoresistance ratio can be obtained by adjusting the thickness of the spacer layer 23 so that a high TMR effect is exhibited between the first ferromagnetic layer 21 and the second ferromagnetic layer 22. To efficiently utilize the TMR effect, the thickness of the spacer layer 23 may be approximately 0.5 to 5.0 nm, or approximately 1.0 to 2.5 nm.

[0039] When the spacer layer 23 is made of a nonmagnetic conductive material, conductive materials such as Cu, Ag, Au, or Ru can be used. To efficiently utilize the GMR effect, the thickness of the spacer layer 23 may be about 0.5 to 5.0 nm, or about 2.0 to 3.0 nm.

[0040] When the spacer layer 23 is made of a non-magnetic semiconductor material, it can be made of zinc oxide, indium oxide, tin oxide, germanium oxide, gallium oxide, ITO, etc. In this case, the thickness of the spacer layer 23 may be about 1.0 to 4.0 nm.

[0041] When a layer including current-carrying points formed by a conductor in a nonmagnetic insulator is used as the spacer layer 23, the current-carrying points may be formed by a nonmagnetic conductor such as Cu, Au, or Al in a nonmagnetic insulator made of aluminum oxide or magnesium oxide. The conductor may also be formed of a magnetic element such as Co, Fe, or Ni. In this case, the thickness of the spacer layer 23 may be approximately 1.0 to 2.5 nm. The current-carrying points are, for example, columnar bodies with a diameter of 1 nm to 5 nm when viewed perpendicularly to the film surface.

[0042] The ferromagnetic layer 26 is magnetically coupled to, for example, the second ferromagnetic layer 22. The magnetic coupling is, for example, antiferromagnetic coupling, and occurs due to RKKY interaction. The direction of the magnetization M22 of the second ferromagnetic layer 22 and the direction of the magnetization M26 of the ferromagnetic layer 26 are antiparallel to each other. The material constituting the ferromagnetic layer 26 is, for example, the same as that of the first ferromagnetic layer 21.

[0043] The magnetic coupling layer 27 is located between the second ferromagnetic layer 22 and the ferromagnetic layer 26. The magnetic coupling layer 27 is made of, for example, Ru, Ir, or the like.

[0044] The buffer layer 24 is a layer that reduces lattice mismatch between different crystals. The buffer layer 24 is, for example, a metal containing at least one element selected from the group consisting of Ta, Ti, Zr, and Cr, or a nitride containing at least one element selected from the group consisting of Ta, Ti, Zr, and Cu. More specifically, the buffer layer 24 is, for example, Ta (element), a NiCr alloy, TaN (tantalum nitride), or CuN (copper nitride). The buffer layer 24 has a thickness of, for example, 1 nm or more and 5 nm or less. The buffer layer 24 is, for example, amorphous. The buffer layer 24 is, for example, located between the seed layer 25 and the second electrode E2 and in contact with the second electrode E2. The buffer layer 24 suppresses the crystal structure of the second electrode E2 from affecting the crystal structure of the second ferromagnetic layer 22.

[0045] The seed layer 25 improves the crystallinity of layers stacked on the seed layer 25. The seed layer 25 is located, for example, between the buffer layer 24 and the ferromagnetic layer 26 and on the buffer layer 24. The seed layer 25 is made of, for example, Pt, Ru, Zr, or NiFeCr. The thickness of the seed layer 25 is, for example, 1 nm or more and 5 nm or less.

[0046] The cap layer 29 is located between the first ferromagnetic layer 21 and the first electrode E1. The cap layer 29 may include a perpendicular magnetization induction layer 28 stacked on the first ferromagnetic layer 21 and in contact with the first ferromagnetic layer 21. The cap layer 29 prevents damage to the lower layers during the process and improves the crystallinity of the lower layers during annealing. The thickness of the cap layer 29 is, for example, 10 nm or less so that the first ferromagnetic layer 21 is irradiated with sufficient light.

[0047] The perpendicular magnetization induction layer 28 induces perpendicular magnetic anisotropy in the first ferromagnetic layer 21. The perpendicular magnetization induction layer 28 is made of, for example, magnesium oxide, W, Ta, or Mo. When the perpendicular magnetization induction layer 28 is made of magnesium oxide, it is preferable that the magnesium oxide has oxygen deficiency to increase conductivity. The film thickness of the perpendicular magnetization induction layer 28 is, for example, 0.5 nm or more and 5.0 nm or less.

[0048] The insulating layer 30 is made of, for example, an oxide, nitride, or oxynitride of Si, Al, or Mg. The insulating layer 30 is made of, for example, silicon oxide (SiO x ), silicon nitride (SiN x ), silicon carbide (SiC), chromium nitride, silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al2O3), zirconium oxide (ZrO x ) etc.

[0049] The first electrode E1 is disposed, for example, on the side where the first magnetic element 2 is irradiated with light. The reflected light L2 is irradiated from the first electrode E1 side to the first magnetic element 2 and is irradiated at least to the first ferromagnetic layer 21. The first electrode E1 is made of a conductive material. The first electrode E1 is, for example, a transparent electrode that is transparent to light in the used wavelength range. The first electrode E1 preferably transmits, for example, 80% or more of light in the used wavelength range. The first electrode E1 is, for example, an oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or indium gallium zinc oxide (IGZO). The first electrode E1 may be configured to have multiple metal pillars in a transparent electrode material of these oxides. It is not essential to use such a transparent electrode material for the first electrode E1. A metal material such as Au, Cu, or Al may be used in a thin film to allow the irradiated light to reach the first ferromagnetic layer 21. When a metal is used as the material of the first electrode E1, the film thickness of the first electrode E1 is, for example, 3 to 10 nm. The first electrode E1 may have an anti-reflection film on the surface that is irradiated with light.

[0050] The second electrode E2 is located on the opposite side of the laminate 20 to the first electrode E1. The second electrode E2 is made of a conductive material. The second electrode E2 is made of a metal such as Cu, Al, or Au. Ta or Ti may be laminated above and below these metals. Alternatively, a laminated film of Cu and Ta, a laminated film of Ta, Cu, and Ti, or a laminated film of Ta, Cu, and TaN may be used. Alternatively, TiN or TaN may be used as the second electrode E2. The film thickness of the second electrode E2 is, for example, 200 nm to 800 nm.

[0051] The second electrode E2 may be transparent to light irradiated onto the first magnetic element 2. As with the first electrode E1, the second electrode E2 may be made of a transparent oxide electrode material such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or indium gallium zinc oxide (IGZO). Even when light is irradiated from the first electrode E1, the light may reach the second electrode E2 depending on the intensity of the light. In this case, however, since the second electrode E2 is made of a transparent oxide electrode material, light reflection at the interface between the second electrode E2 and a layer in contact with it can be suppressed compared to when the second electrode E2 is made of a metal.

[0052] A first signal S1 and a second signal S2, which are electrical signals, are input to the circuit 3. The first signal S1 is input to the circuit 3, for example, from the light-emitting unit 1. The first signal S1 is a signal corresponding to the light emission of the light-emitting unit 1. The first signal S1 is, for example, a part of a voltage signal applied from a power source to the laser light source of the light-emitting unit 1 when pulsed light is emitted from the laser light source. The first signal S1 is a signal corresponding to the timing at which light L1 is emitted from the light-emitting unit 1. The second signal S2 is input to the circuit 3, for example, from the first magnetic element 2. The second signal S2 is a signal corresponding to the irradiation of the reflected light L2 onto the first magnetic element 2. The second signal S2 is, for example, a part of the output voltage generated from the first magnetic element 2 when the reflected light L2 is irradiated onto the first magnetic element 2. The second signal S2 is a signal corresponding to the irradiation timing of the reflected light L2 onto the first magnetic element 2.

[0053] The circuit 3 includes, for example, a signal receiving unit, a counter, a processor, and a memory. The signal receiving unit has an input terminal to which the first signal S1 or the second signal S2 is input. There may be two separate input terminals, one to which the first signal S1 is input and one to which the second signal S2 is input, or there may be one common input terminal to which both the first signal S1 and the second signal S2 are input. The signal receiving unit may further include, for example, an amplifier that amplifies the signal input to the input terminal. The processor is, for example, a CPU (Central Processing Unit). The counter counts clock pulses for CPU operation. The memory stores, for example, the count number when the first signal S1 is received by the signal receiving unit and the count number when the second signal S2 is received by the signal receiving unit. As will be described in more detail below, the optical system 100 uses a counter, processor, and memory to determine the time difference ΔT between the emission of light L1 by the light-emitting unit 1 and the irradiation of reflected light L2 onto the first magnetic element 2, the distance between the optical device 10 and the irradiated object Ob, and a three-dimensional image of the irradiated object Ob.

[0054] Here, an example has been shown in which the counter, processor, and memory are included in the circuit 3, but an example may also be used in which these components are included in the external device 90 and not included in the circuit 3.

[0055] The external interface 4 communicates with an external device 90. The communication between the external interface 4 and the external device 90 may be wireless or wired. The external interface 4 is a communication adapter that establishes communication with the external device 90.

[0056] The external device 90 includes, for example, a computer, a control device, etc. The computer is, for example, an information processing device including a CPU (Central Processing Unit). The control device controls other devices based on signals from the optical device 10. For example, if the optical system 100 is incorporated in an automobile, the control device controls a control system of the automobile, such as the brakes, based on information about the distance between the optical device 10 and the irradiated object Ob communicated from the optical device 10. As described above, the external device 90 may also include a calculation device for calculating the time difference ΔT between the emission of the light L1 from the light-emitting unit 1 and the irradiation of the reflected light L2 to the first magnetic element 2, the distance between the optical device 10 and the irradiated object Ob, and a three-dimensional image of the irradiated object Ob.

[0057] Next, the operation of the optical system 100 according to the first embodiment will be described. First, a pulsed laser is emitted from the light-emitting unit 1. A first signal S1 corresponding to the emission of light L1 from the light-emitting unit 1 is input to the circuit 3. The first signal S1 is received by the signal-receiving unit, and the count number when the signal-receiving unit receives the first signal S1 is stored in memory.

[0058] A portion of the light L1 is collimated by the lens R1 and is irradiated onto the object to be irradiated Ob. The reflected light L2 reflected by the object to be irradiated Ob is collected by the lens R2 and is irradiated onto the first magnetic element 2. When the reflected light L2 is irradiated onto the first magnetic element 2, an output voltage is generated from the first magnetic element 2. In other words, the first magnetic element 2 converts the irradiated light into an electrical signal.

[0059] FIG. 3 is a diagram for explaining a first mechanism of operation of the first magnetic element 2 according to the first embodiment. FIG. 4 is a diagram for explaining a second mechanism of operation of the first magnetic element 2 according to the first embodiment. In FIGS. 3 and 4, only the first ferromagnetic layer 21, the second ferromagnetic layer 22, and the spacer layer 23 of the first magnetic element 2 are illustrated. In the upper graphs of FIGS. 3 and 4, the vertical axis represents the intensity of the reflected light L2 irradiated onto the first ferromagnetic layer 1, and the horizontal axis represents time. In the lower graphs of FIGS. 3 and 4, the vertical axis represents the resistance value of the first magnetic element 2 in the z direction, and the horizontal axis represents time.

[0060] The output voltage from the first magnetic element 2 changes with a change in the intensity of the reflected light L2 irradiated onto the first ferromagnetic layer 21. The change in the output voltage from the first magnetic element 2 is caused by a change in the resistance value in the stacking direction of the first ferromagnetic layer 21, the second ferromagnetic layer 22, and the spacer layer 23. Here, an example will be described in which the intensity of the light irradiated onto the first ferromagnetic layer 21 has two levels: a first intensity and a second intensity. The intensity of the light of the second intensity is assumed to be greater than the intensity of the light of the first intensity. The first intensity may be zero even if the intensity of the light irradiated onto the first ferromagnetic layer 21 is zero.

[0061] First, in a state where the first ferromagnetic layer 21 is irradiated with light of a first intensity (hereinafter referred to as the initial state), the magnetization M21 of the first ferromagnetic layer 21 and the magnetization M22 of the second ferromagnetic layer 22 are parallel, the resistance value of the first magnetic element 2 in the z direction indicates a first resistance value R1, and the magnitude of the output voltage from the first magnetic element 2 indicates a first value. The resistance value of the first magnetic element 2 in the z direction is determined by Ohm's law from the voltage generated across both ends of the first magnetic element 2 in the z direction by passing a sense current Is through the first magnetic element 2 in the z direction. The output voltage from the first magnetic element 2 is generated between the first electrode E1 and the second electrode E2. In the example shown in FIG. 3, the sense current Is is passed from the first ferromagnetic layer 21 to the second ferromagnetic layer 22. By passing the sense current Is in this direction, a spin transfer torque acts on the magnetization M21 of the first ferromagnetic layer 21 in the same direction as the magnetization M22 of the second ferromagnetic layer 22, and the magnetizations M21 and M22 become parallel in the initial state. Also, by passing the sense current Is in this direction, it is possible to prevent the magnetization M21 of the first ferromagnetic layer 21 from reversing during operation.

[0062] Next, the intensity of the reflected light L2 irradiated to the first ferromagnetic layer 21 changes from the first intensity to a second intensity. The second intensity is greater than the first intensity, and the magnetization M21 of the first ferromagnetic layer 21 changes from its initial state. The state of the magnetization M21 of the first ferromagnetic layer 21 when no light is irradiated to the first ferromagnetic layer 21 is different from the state of the magnetization M21 of the first ferromagnetic layer 21 when light of the second intensity is irradiated to the first ferromagnetic layer 21. The state of the magnetization M21 refers to, for example, the tilt angle or magnitude with respect to the z direction.

[0063] For example, as shown in Fig. 3, when the intensity of light irradiated to the first ferromagnetic layer 21 changes from a first intensity to a second intensity, the magnetization M21 tilts with respect to the z direction. Also, for example, as shown in Fig. 4, when the intensity of light irradiated to the first ferromagnetic layer 21 changes from the first intensity to the second intensity, the magnitude of the magnetization M21 decreases. For example, when the magnetization M21 of the first ferromagnetic layer 21 tilts with respect to the z direction due to the irradiation intensity of light, the tilt angle is greater than 0° and less than 90°.

[0064] When the magnetization M21 of the first ferromagnetic layer 21 changes from its initial state, the resistance value in the z direction of the first magnetic element 2 exhibits a second resistance value R2, and the magnitude of the output voltage from the first magnetic element 2 exhibits a second value. The second resistance value R2 is greater than the first resistance value R1, and the second value of the output voltage is greater than the first value. The second resistance value R2 is between the resistance value (first resistance value R1) when the magnetization M21 and the magnetization M22 are parallel and the resistance value when the magnetization M21 and the magnetization M22 are antiparallel.

[0065] In the case shown in FIG. 4, a spin transfer torque acts on the magnetization M21 of the first ferromagnetic layer 21 in the same direction as the magnetization M22 of the second ferromagnetic layer 22. Therefore, the magnetization M21 attempts to return to a state parallel to the magnetization M22, and when the intensity of the light irradiated to the first ferromagnetic layer 21 changes from the second intensity to the first intensity, the first magnetic element 2 returns to its initial state. In the case shown in FIG. 4, when the intensity of the light irradiated to the first ferromagnetic layer 21 returns to the first intensity, the magnitude of the magnetization M21 of the first ferromagnetic layer 21 returns to its original value, and the first magnetic element 2 returns to its initial state. In either case, the resistance value in the z direction of the first magnetic element 2 returns to the first resistance value R1. In other words, when the intensity of light irradiated to the first ferromagnetic layer 21 changes from the second intensity to the first intensity, the resistance value in the z-direction of the first magnetic element 2 changes from the second resistance value R2 to the first resistance value R1, and the magnitude of the output voltage from the first magnetic element 2 changes from the second value to the first value.

[0066] The output voltage from the first magnetic element 2 changes in response to a change in the intensity of light irradiated onto the first ferromagnetic layer 21, and the change in the intensity of the irradiated light can be converted into a change in the output voltage from the first magnetic element 2. In other words, the first magnetic element 2 can convert light into an electric signal.

[0067] Here, the case where the magnetization M21 and the magnetization M22 are parallel in the initial state has been described as an example, but the magnetization M21 and the magnetization M22 may be antiparallel in the initial state. In this case, the resistance value in the z direction of the first magnetic element 2 decreases as the state of the magnetization M21 changes (for example, as the angle of the magnetization M21 from the initial state increases). When the initial state is one in which the magnetization M21 and the magnetization M22 are antiparallel, it is preferable to flow the sense current Is from the second ferromagnetic layer 22 toward the first ferromagnetic layer 21. By flowing the sense current Is in this direction, a spin transfer torque acts on the magnetization M21 of the first ferromagnetic layer 21 in the opposite direction to the magnetization M22 of the second ferromagnetic layer 22, and the magnetization M21 and the magnetization M22 become antiparallel in the initial state.

[0068] Although the examples have been given in which the magnetization M21 and the magnetization M22 are parallel or antiparallel in the initial state, the magnetization M21 and the magnetization M22 may be orthogonal in the initial state. For example, this applies to a case in which the first ferromagnetic layer 21 is an in-plane magnetization film in which the magnetization M21 is oriented in any direction in the xy plane, and the second ferromagnetic layer 22 is a perpendicular magnetization film in which the magnetization M22 is oriented in the z direction in the initial state. Due to magnetic anisotropy, the magnetization M21 is oriented in any direction in the xy plane, and the magnetization M22 is oriented in the z direction, so that the magnetization M21 and the magnetization M22 are orthogonal in the initial state. This relationship may also be reversed. That is, in the initial state, the magnetization M21 may be oriented in the z direction, and the magnetization M22 may be oriented in any direction in the xy plane.

[0069] The first magnetic element 2 converts the reflected light L2 into an electrical signal, thereby generating a second signal S2 corresponding to the irradiation of the reflected light L2 onto the first magnetic element 2. The second signal S2 is input to the circuit 3. The second signal S2 is received by a signal receiving unit, and the count number when the signal receiving unit receives the second signal S2 is stored in memory.

[0070] The optical system 100 calculates the time difference ΔT between the emission of light L1 by the light-emitting unit 1 and the irradiation of reflected light L2 onto the first magnetic element 2, for example, based on the first signal S1 and the second signal S2 input to the circuit 3. Fig. 5 is a diagram showing an example of the first signal S1 and the second signal S2 in the optical system 100 according to the first embodiment.

[0071] There is a time difference between the time when the first signal S1 is input to the circuit 3 and the time when the second signal S2 is input to the circuit 3. This time difference corresponds to the time difference ΔT between the emission of light L1 from the light-emitting unit 1 and the irradiation of the reflected light L2 onto the first magnetic element 2. The time difference ΔT can be calculated, for example, as the difference between the time when the first signal S1 exceeds a predetermined threshold and the time when the second signal S2 exceeds a predetermined threshold. The time difference ΔT may also be calculated as the difference between the time when the first signal S1 reaches its maximum value and the time when the second signal S2 reaches its maximum value.

[0072] The time difference ΔT can be calculated from the difference between the count stored in memory when the first signal S1 is received and the count when the second signal S2 is received. The counter in circuit 3 counts clock pulses at a fixed reference period. Therefore, the time difference ΔT can be calculated by multiplying the difference in counts by the reference period of the clock pulse. For example, if light L1 is emitted from the light-emitting unit 1 at the nth count of the counter, and the first signal S1 is received by circuit 3, and then reflected light L2 is irradiated onto the first magnetic element 2 at the mth count, and the second signal S2 is received by circuit 3, then the time difference ΔT can be calculated as (mn) × t, where t is the reference period of the clock pulse.

[0073] Next, the circuit 3 performs an operation to calculate the distance between the irradiated object Ob and the optical device 10 based on the calculated time difference ΔT. Multiplying the time difference ΔT by the speed of light calculates the distance of the optical path from the light emitting unit 1 to the irradiated object Ob and from the irradiated object Ob to the first magnetic element 2. Assuming that the distances from the light emitting unit 1 to the irradiated object Ob and the distances between the first magnetic element 2 and the irradiated object Ob are approximately the same, the distance between the irradiated object Ob and the optical device 10 is calculated by multiplying the time difference ΔT by the speed of light and dividing the result by 2.

[0074] The circuit 3 may also perform an operation of obtaining a three-dimensional image of the irradiated object Ob from the reflected light L2. When obtaining a three-dimensional image of the irradiated object Ob, for example, a plurality of first magnetic elements 2 are arranged two-dimensionally. The three-dimensional image of the irradiated object Ob is obtained from information on the position of the first magnetic elements 2 that are irradiated with the reflected light L2 among the two-dimensionally arranged first magnetic elements 2, and information on the distance between each first magnetic element 2 and the irradiated object Ob, which is obtained from the time difference ΔT between the first signal and the second signal S2.

[0075] Information on the time difference ΔT between the emission of light L1 by the light-emitting unit 1 and the irradiation of the reflected light L2 onto the first magnetic element 2, the distance between the optical device 10 and the irradiated object Ob, and the three-dimensional image of the irradiated object Ob is converted into signals and input to the external interface 4. The external interface 4 communicates with an external device 90, and outputs this information to the outside.

[0076] If the external device 90 has a calculation device for calculating the time difference ΔT between the emission of light L1 from the light-emitting unit 1 and the irradiation of the reflected light L2 to the first magnetic element 2, the distance between the optical device 10 and the irradiated object Ob, and a three-dimensional image of the irradiated object Ob, the calculations for calculating these are performed in the external device 90 rather than in the circuit 3. If these calculations are performed in the external device 90, the first signal S1 and the second signal S2 are communicated to the external device 90 via the external interface 4.

[0077] As described above, the optical system 100 according to the first embodiment can obtain the time difference ΔT between the emission of light L1 by the light-emitting unit 1 and the irradiation of reflected light L2 onto the first magnetic element 2, the distance between the optical device 10 and the irradiated object Ob, or a three-dimensional image of the irradiated object Ob, based on the first signal S1 and the second signal S2.

[0078] Furthermore, the optical system 100 according to the first embodiment detects the reflected light L2 using the first magnetic element 2, and therefore can accurately measure the time difference ΔT, the distance between the optical device 10 and the irradiated object Ob, the three-dimensional image of the irradiated object Ob, etc. This is because the speed at which the output of an electrical signal rises after receiving light from the first magnetic element 2 is faster than that of a photodetector using a silicon semiconductor.

[0079] FIG. 6 shows the change over time in the output voltage from the first magnetic element 2 in the optical system 100 according to the first embodiment. From the time when the light-emitting unit 1 emits light L1 until the first magnetic element 2 is irradiated with reflected light L2, the output voltage from the first magnetic element 2 is a first value (e.g., 0 V). The time from when the light-emitting unit 1 emits light L1 until the first magnetic element 2 is irradiated with reflected light L2 is referred to as ToF (Time of Flight). When the first magnetic element 2 is irradiated with reflected light L2, the output voltage from the first magnetic element 2 gradually increases and exceeds a predetermined threshold. The time from when the first magnetic element 2 is irradiated with light (in the first embodiment, reflected light L2) until the output of the first magnetic element 2 exceeds a predetermined threshold is referred to as ToA (Time of Arrival) of the first magnetic element 2. As shown in FIG. 7, the time from when the first magnetic element 2 is irradiated with light (in the first embodiment, reflected light L2) until the output of the first magnetic element 2 reaches a maximum may also be referred to as ToA of the first magnetic element 2. The first magnetic element 2 has a shorter ToA than a photodetector using a silicon semiconductor.

[0080] The time difference ΔT between the emission of light L1 by the light-emitting unit 1 and the irradiation of the reflected light L2 onto the first magnetic element 2 is the sum of ToF and ToA. On the other hand, the parameter related to the distance between the irradiated object Ob and the light-emitting unit 1 is ToF, while ToA is a distance measurement error. Because the first magnetic element 2 has a short ToA, it can measure the time difference ΔT, the distance between the optical device 10 and the irradiated object Ob, the three-dimensional image of the irradiated object Ob, and the like with higher accuracy than a photodetector using a silicon semiconductor.

[0081] "Second embodiment" 8 is a schematic diagram of an optical system 101 according to the second embodiment. The optical system 101 according to the second embodiment differs from the optical system 100 according to the first embodiment in the configuration of the optical device 11. In the optical system 101, the same components as those in the optical system 100 are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0082] The optical device 11 includes, for example, a light emitting unit 1, a first magnetic element 2, a circuit 3, an external interface 4, a second magnetic element 5, lenses R1 and R2, and mirrors M1 and M2.

[0083] A portion of the light L1 emitted by the light-emitting unit 1 passes through the mirror M1, becomes parallel light by the lens R1, and reaches the object to be irradiated Ob. A portion of the light L1 emitted by the light-emitting unit 1 is irradiated onto the second magnetic element 5 via the mirrors M1 and M2. The mirror M1 is, for example, a half mirror. The optical path length of the light L1 between the light-emitting unit 1 and the second magnetic element 5 is negligibly small compared to the optical path length of the light L1 between the light-emitting unit 1 and the object to be irradiated Ob.

[0084] Fig. 9 is a cross-sectional view of the second magnetic element 5 according to the second embodiment. In Fig. 9, the direction of magnetization of the ferromagnetic material in the initial state is indicated by an arrow.

[0085] The second magnetic element 5 has at least a third ferromagnetic layer 51, a fourth ferromagnetic layer 52, and a second spacer layer 53. The second spacer layer 53 is located between the third ferromagnetic layer 51 and the fourth ferromagnetic layer 52. In addition to these, the second magnetic element 5 may also have a buffer layer 54, a seed layer 55, a ferromagnetic layer 56, a magnetic coupling layer 57, a perpendicular magnetization induction layer 58, a cap layer 59, and an insulating layer 60. The second magnetic element 5 is sandwiched between a third electrode E3 and a fourth electrode E4.

[0086] The third ferromagnetic layer 51, the fourth ferromagnetic layer 52, the second spacer layer 53, the buffer layer 54, the seed layer 55, the ferromagnetic layer 56, the magnetic coupling layer 57, the perpendicular magnetization induction layer 58, the cap layer 59, and the insulating layer 60 correspond to and have similar configurations as the first ferromagnetic layer 21, the second ferromagnetic layer 22, the spacer layer 23, the buffer layer 24, the seed layer 25, the ferromagnetic layer 26, the magnetic coupling layer 27, the perpendicular magnetization induction layer 28, the cap layer 29, and the insulating layer 30 of the first magnetic element 2, respectively. The third electrode E3 and the fourth electrode E4 correspond to and have similar configurations as the first electrode E1 and the second electrode E2 of the first magnetic element 2, respectively. Magnetization M51, magnetization M52, and magnetization M56 correspond to the magnetization M21, magnetization M22, and magnetization M26 of the first magnetic element 2, respectively.

[0087] In the second magnetic element 5, an output voltage, which is an electric signal, is generated when light is irradiated, in the same manner as the first magnetic element 2.

[0088] A first signal S1 and a second signal S2 are input to the circuit 3. The first signal S1 is input to the circuit 3 from the second magnetic element 5. The first signal S1 is a signal corresponding to the emission of light L1 from the light-emitting unit 1, and is, for example, an electrical signal generated from the second magnetic element 5 when part of the light L1 is irradiated onto the second magnetic element 5.

[0089] The operation of the optical system 101 according to the second embodiment differs from that of the optical system 100 in that a first signal S1 is input from the second magnetic element 5 to the circuit 3. A portion of the light L1 emitted by the light-emitting unit 1 is irradiated onto the second magnetic element 5 via mirrors M1 and M2. The second magnetic element 5 outputs a first signal S1, which is an electrical signal, when a portion of the light L1 is irradiated onto the second magnetic element 5. The first signal S1 is input to the circuit 3.

[0090] FIG. 10 illustrates an example of a first signal S1 and a second signal S2 in an optical system 101 according to the second embodiment. There is a time difference between the time when the first signal S1 is input to the circuit 3 and the time when the second signal S2 is input to the circuit 3. In the optical system 101, the time difference between the emission of light L1 from the light-emitting unit 1 and the irradiation of a portion of the light L1 onto the second magnetic element 5 is negligibly small. Therefore, the time difference between the time when the first signal S1 is input to the circuit 3 and the time when the second signal S2 is input to the circuit 3 corresponds to the time difference ΔT between the emission of light L1 from the light-emitting unit 1 and the irradiation of the reflected light L2 onto the first magnetic element 2. The time difference ΔT can be calculated, for example, as the difference between the time when the first signal S1 exceeds a predetermined threshold and the time when the second signal S2 exceeds a predetermined threshold. The time difference ΔT may also be calculated as the difference between the time when the first signal S1 reaches its maximum value and the time when the second signal S2 reaches its maximum value.

[0091] The operations of the circuit 3 , the external interface 4 and the external device 90 are the same as those of the optical system 100 .

[0092] Like the optical system 100 according to the first embodiment, the optical system 101 according to the second embodiment can obtain, based on the first signal S1 and the second signal S2, the time difference ΔT between the emission of light L1 by the light-emitting unit 1 and the irradiation of reflected light L2 to the first magnetic element 2, the distance between the optical device 11 and the irradiated object Ob, or a three-dimensional image of the irradiated object Ob. Furthermore, because the optical system 101 according to the second embodiment detects the reflected light L2 using the first magnetic element 2, it can accurately measure the time difference ΔT, the distance between the optical device 11 and the irradiated object Ob, a three-dimensional image of the irradiated object Ob, and the like. Furthermore, because the optical system 101 according to the second embodiment detects the reflected light L2 using the first magnetic element 2 and detects light L1 using the second magnetic element 5, by using two magnetic elements having similar ToA values ​​as the first magnetic element 2 and the second magnetic element 5, it can more accurately measure the time difference ΔT, the distance between the optical device 11 and the irradiated object Ob, a three-dimensional image of the irradiated object Ob, and the like.

[0093] "Third embodiment" 11 is a schematic diagram of an optical system 102 according to the third embodiment. The optical system 102 according to the third embodiment differs from the optical system 100 according to the first embodiment in the configuration of the optical device 12. In the optical system 102, the same components as those in the optical system 100 are denoted by the same reference numerals, and the description thereof will be omitted.

[0094] The optical device 12 includes, for example, a light emitting unit 1, a first magnetic element 2, a circuit 3, an external interface 4, lenses R1 and R2, and a plurality of mirrors M1.

[0095] A portion of the light L1 emitted by the light-emitting unit 1 is collimated by the lens R1 and reaches the irradiated object Ob. A portion of the light L1 emitted by the light-emitting unit 1 is irradiated onto the first magnetic element 2 via multiple mirrors M1. As shown in FIG. 11, the reflected light L2 from the irradiated object Ob also passes through the lens R2 and the mirror M1 and is irradiated onto the first magnetic element 2. The mirror M1 is, for example, a half mirror. The optical path length of the light L1 between the light-emitting unit 1 and the first magnetic element 2 is negligibly small compared to the optical path length of the light L1 between the light-emitting unit 1 and the irradiated object Ob.

[0096] A first signal S1 and a second signal S2 are input to the circuit 3. FIG. 12 is a diagram illustrating an example of the first signal S1 and the second signal S2 in the optical system 102 according to the third embodiment. Both the first signal S1 and the second signal S2 are input to the circuit 3 from the first magnetic element 2. The first signal S1 is a signal corresponding to the emission of light L1 from the light-emitting unit 1. For example, it is an electrical signal generated from the first magnetic element 2 when a portion of the light L1 is irradiated onto the first magnetic element 2. The second signal S2 is a signal corresponding to the irradiation of reflected light L2 onto the first magnetic element. For example, it is an electrical signal generated from the second magnetic element 2 when the reflected light L2 is irradiated onto the first magnetic element 2. There is a time difference between the time when the first signal S1 is input to the circuit 3 and the time when the second signal S2 is input to the circuit 3. In the optical system 102, the time difference between the emission of light L1 from the light-emitting unit 1 and the irradiation of a portion of the light L1 onto the first magnetic element 2 is negligibly small. Therefore, the time difference between the time when the first signal S1 is input to the circuit 3 and the time when the second signal S2 is input to the circuit 3 corresponds to the time difference ΔT between the emission of light L1 from the light-emitting unit 1 and the irradiation of reflected light L2 onto the first magnetic element 2. The time difference ΔT can be calculated, for example, as the difference between the time when the first signal S1 becomes greater than a predetermined threshold and the time when the second signal S2 becomes greater than a predetermined threshold. The time difference ΔT may also be calculated as the difference between the time when the first signal S1 reaches its maximum value and the time when the second signal S2 reaches its maximum value.

[0097] The operations of the circuit 3, the external interface 4, and the external device 90 are similar to those of the optical system 100. Also, in the optical device 12 of the optical system 102, similar to the optical device 10 of the optical system 100, a plurality of first magnetic elements 2 may be arranged one-dimensionally or two-dimensionally, in which case the light L1 may be irradiated onto the arranged plurality of first magnetic elements 2, or the light L1 may be irradiated onto one first magnetic element 2 of the arranged plurality of first magnetic elements 2.

[0098] Like the optical system 100 according to the first embodiment, the optical system 102 according to the third embodiment can obtain, based on the first signal S1 and the second signal S2, the time difference ΔT between the emission of light L1 by the light emitter 1 and the irradiation of the reflected light L2 onto the first magnetic element 2, the distance between the optical device 12 and the irradiated object Ob, or a three-dimensional image of the irradiated object Ob. Furthermore, because the optical system 102 according to the third embodiment detects the reflected light L2 using the first magnetic element 2, it can accurately measure the time difference ΔT, the distance between the optical device 12 and the irradiated object Ob, a three-dimensional image of the irradiated object Ob, and the like. Furthermore, because the optical system 102 according to the third embodiment detects the reflected light L2 and the light L1 using the same first magnetic element 2, it can reduce the difference between the ToA value when a portion of the light L1 is irradiated onto the first magnetic element 2 and the ToA value when the reflected light L2 is irradiated onto the first magnetic element 2, thereby more accurately measuring the time difference ΔT, the distance between the optical device 12 and the irradiated object Ob, a three-dimensional image of the irradiated object Ob, and the like.

[0099] "Fourth embodiment" 13 is a schematic diagram of an optical system 103 according to the fourth embodiment. The optical system 103 according to the fourth embodiment differs from the optical system 100 according to the first embodiment in the configuration of the optical device 13. In the optical system 103, the same components as those in the optical system 100 are denoted by the same reference numerals, and the description thereof will be omitted.

[0100] The optical device 13 includes, for example, a light-emitting unit 1, a first magnetic element 2, a circuit 3, an external interface 4, a light scanning mirror 6, a lens R3, and mirrors M1 and M2. The lens R3 collimates the light L1 and collects the reflected light L2. A first signal S1 is input from the light-emitting unit 1 to the circuit 3.

[0101] The optical scanning mirror 6 is, for example, a two-axis MEMS mirror that changes the reflection direction of light in the horizontal and vertical directions. The optical scanning mirror 6 can scan the light irradiation position on the irradiated object Ob by changing the reflection direction of the light L1. The optical system 103 uses the optical scanning mirror 6 to three-dimensionally scan the light irradiation position on the irradiated object Ob. The light L1 emitted by the light-emitting unit 1 is reflected by the optical scanning mirror 6 and irradiated onto the irradiated object Ob, and the reflected light L2 from the irradiated object Ob is reflected by the optical scanning mirror and irradiated onto the first magnetic element 2. In the optical device 13 shown in FIG. 13, the light L1 emitted by the light-emitting unit 1 passes through a mirror M1 and is converted into parallel light by a lens R3. The mirror M1 is, for example, a half mirror. The parallel light L1 is reflected by the optical scanning mirror 6 and irradiated onto the irradiated object Ob. The reflected light L2 from the object to be irradiated Ob is reflected by the optical scanning mirror 6, and then collected by the lens R3, and is irradiated onto the first magnetic element 2 via the mirrors M1 and M2.

[0102] Similar to the optical system 100 according to the first embodiment, the optical system 103 according to the fourth embodiment can obtain, based on the first signal S1 and the second signal S2, the time difference ΔT between the emission of light L1 by the light-emitting unit 1 and the irradiation of the reflected light L2 onto the first magnetic element 2, the distance between the optical device 13 and the irradiated object Ob, or a three-dimensional image of the irradiated object Ob. Furthermore, the optical system 103 can measure the distance between the optical device 13 and the irradiated object Ob for each position on the irradiated object Ob by using the optical scanning mirror 6 to perform measurements while changing the irradiation position of the light on the irradiated object Ob, and can obtain a three-dimensional image of the irradiated object Ob from this information. The optical system 103 can obtain a three-dimensional image of the irradiated object Ob even with only one first magnetic element 2. Multiple first magnetic elements 2 may be arranged one-dimensionally or two-dimensionally along a plane intersecting the irradiation direction of the reflected light L2. Furthermore, since the optical system 103 according to the fourth embodiment detects the reflected light L2 using the first magnetic element 2, it is possible to accurately measure the time difference ΔT, the distance between the optical device 13 and the irradiated object Ob, the three-dimensional image of the irradiated object Ob, etc.

[0103] "Fifth embodiment" 14 is a schematic diagram of an optical system 104 according to the fifth embodiment. The optical system 104 according to the fifth embodiment differs from the optical system 101 according to the second embodiment in the configuration of the optical device 14. In the optical system 104, the same components as those in the optical system 101 are denoted by the same reference numerals, and the description thereof will be omitted.

[0104] The optical device 14 is obtained by applying the optical scanning mirror 6, which is a characteristic component of the optical device 13 according to the fourth embodiment, to the optical device 11 according to the second embodiment. The optical device 14 includes, for example, a light-emitting unit 1, a first magnetic element 2, a circuit 3, an external interface 4, a second magnetic element 5, an optical scanning mirror 6, a lens R3, and multiple mirrors M1 and M2. The optical system 104 uses the optical scanning mirror 6 to three-dimensionally scan the irradiation position of the light on the irradiation object Ob. In the optical device 14 shown in FIG. 14, a portion of the light L1 emitted by the light-emitting unit 1 passes through multiple mirrors M1 and is converted into parallel light by the lens R3. The mirror M1 is, for example, a half mirror. The parallel light L1 is reflected by the optical scanning mirror 6 and irradiated onto the irradiation object Ob. The reflected light L2 from the irradiation object Ob is reflected by the optical scanning mirror 6, concentrated by the lens R3, and irradiated onto the first magnetic element 2 via the mirrors M1 and M2.

[0105] The optical system 104 according to the fifth embodiment can obtain the same effects as the optical system 103 according to the fourth embodiment.

[0106] "Sixth embodiment" 15 is a schematic diagram of an optical system 105 according to the sixth embodiment. The optical system 105 according to the sixth embodiment differs from the optical system 102 according to the third embodiment in the configuration of the optical device 15. In the optical system 105, the same components as those in the optical system 102 are denoted by the same reference numerals, and the description thereof will be omitted.

[0107] The optical device 15 is obtained by applying an optical scanning mirror 6, which is a characteristic configuration of the optical device 13 according to the fourth embodiment, to the optical device 12 according to the third embodiment. The optical device 15 includes, for example, a light-emitting unit 1, a first magnetic element 2, a circuit 3, an external interface 4, an optical scanning mirror 6, a lens R3, and a plurality of mirrors M1 and M2. The optical system 105 uses the optical scanning mirror 6 to three-dimensionally scan the irradiation position of light on the irradiation object Ob.

[0108] In the optical device 14 shown in Fig. 15, a portion of light L1 emitted from a light-emitting unit 1 passes through multiple mirrors M1 and is converted into parallel light by a lens R3. The mirror M1 is, for example, a half mirror. The parallel light L1 is reflected by an optical scanning mirror 6 and is irradiated onto an object to be irradiated Ob. The reflected light L2 from the object to be irradiated Ob is reflected by the optical scanning mirror 6, is collected by a lens R3, and is irradiated onto the first magnetic element 2 via the mirrors M1 and M2.

[0109] The optical system 105 according to the sixth embodiment can obtain the same effects as the optical system 103 according to the fourth embodiment.

[0110] The optical systems according to the above embodiments can be used for various purposes such as autonomous driving and surveying, and can be mounted on various devices such as automobiles, aircraft, robots, smartphones, etc. The optical systems according to the above embodiments can also be applied to, for example, MR (Mixed Reality) glasses, VR (Virtual Reality) glasses, etc.

[0111] (Application example) 16 is a schematic diagram of a device 201 according to a second application example. The device 201 is, for example, MR glasses.

[0112] The device 201 has an optical device 13 and an image device 80 in a frame F above a lens R6 of the glasses. Here, the optical device 13 is given as an example, but optical devices according to other embodiments may also be used.

[0113] The imaging device 80 includes a light-emitting unit 81, an s-polarizing plate 82, and a lens R5. The light-emitting unit 81 includes, for example, red, green, and blue laser diodes. The image output from the light-emitting unit 81 is reflected by a mirror M1 and a lens R6 and enters the eye EY.

[0114] λ / 4 plates P1 and P2 are arranged on both sides of lens R6, and s-polarizing plate P3 is arranged on the outermost surface of lens R6. An image output from light-emitting unit 81 becomes s-polarized light by passing through s-polarizing plate 82. The s-polarized image becomes p-polarized light by passing through λ / 4 plate P1 and λ / 4 plate P2. Because s-polarizing plate P3 cuts p-polarized light, the image output from light-emitting unit 81 is not output outside of lens R6.

[0115] The optical device 13 has, for example, a p-polarizer 7 between the light-emitting unit 1 and the optical scanning mirror 6. Light emitted from the light-emitting unit 1 becomes p-polarized by passing through the p-polarizer. The p-polarized light becomes s-polarized by passing through the λ / 4 plate P1 and the λ / 4 plate P2, and then passes through the s-polarizer P3 and is irradiated onto the object Ob. The reflected light from the object Ob passes through the s-polarizer P3, the λ / 4 plate P2, the lens R6, and the λ / 4 plate P1, is reflected by the optical scanning mirror 6, and is then irradiated onto the first magnetic element 2. The optical system 103 including the optical device 13 measures the distance to the object Ob and a three-dimensional image of the object Ob. The information measured by the optical system 103 is sent to the image device 80 and reflected in the image output from the light-emitting unit 81. The actual object Ob and a virtual image are simultaneously projected onto the human eye EY.

[0116] Although an example in which the optical device 13 is provided inside the lens R6 has been shown here, the optical device 13 may also be provided outside the lens R6. In this case, it is not necessary to specify the polarization of the light output from the optical device 13.

[0117] As described above, the present invention is not limited to the above-described embodiments and modifications, and various modifications and changes are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0118] 1,71,81...light emitting unit, 2...first magnetic element, 3...circuit, 4...external interface, 5...second magnetic element, 6,76...light scanning mirror, 7...p-polarizer, 10,11,12,13,14,15...optical device, 20...laminated body, 21...first ferromagnetic layer, 22...second ferromagnetic layer, 23...spacer layer, 24,54...buffer layer, 25,55...seed layer, 26,56...ferromagnetic layer, 27,57...magnetic coupling layer, 28,58...perpendicular magnetization induction layer, 29,59...capacitor Top layer, 30, 60...insulating layer, 51...third ferromagnetic layer, 52...fourth ferromagnetic layer, 53...second spacer layer, 70...imaging device, 72...light receiving section, 82...s polarizing plate, 90...external device, 100, 101, 102, 103, 104, 105...optical system, 200, 201...device, E1...first electrode, E2...second electrode, E3...third electrode, E4...fourth electrode, F...frame, L1...emitted light, L2...reflected light, Ob...irradiated object, S1...first signal, S2...second signal

Claims

1. a light emitting unit, a first magnetic element, and a circuit; the first magnetic element includes a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer; the first magnetic element is irradiated with light emitted from the light emitting unit and reflected by an irradiated object; a first signal corresponding to light emission from the light-emitting unit is input to the circuit; a second signal corresponding to irradiation of the reflected light onto the first magnetic element is input from the first magnetic element to the circuit; When the magnetization of the first ferromagnetic layer and the magnetization of the second ferromagnetic layer are parallel to each other in a state where the first magnetic element is not irradiated with light, a sense current is caused to flow from the first ferromagnetic layer to the second ferromagnetic layer; An optical device configured to flow a sense current from the second ferromagnetic layer to the first ferromagnetic layer when the magnetization of the first ferromagnetic layer and the magnetization of the second ferromagnetic layer are in an antiparallel relationship when light is not irradiated onto the first magnetic element.

2. The optical device according to claim 1 , wherein the first signal is input to the circuit from the light emitting portion.

3. Further comprising a second magnetic element; the second magnetic element includes a third ferromagnetic layer, a fourth ferromagnetic layer, and a second spacer layer sandwiched between the third ferromagnetic layer and the fourth ferromagnetic layer; a part of the light emitted by the light-emitting unit is irradiated onto the second magnetic element; The optical device according to claim 1 , wherein the first signal is input to the circuit from the second magnetic element.

4. a part of the light emitted by the light-emitting unit is also irradiated onto the first magnetic element; The optical device according to claim 1 , wherein the first signal is input to the circuit from the first magnetic element.

5. further comprising a light scanning mirror; At least a portion of the light emitted by the light-emitting unit is reflected by the optical scanning mirror and irradiated onto the irradiated body, and the reflected light from the irradiated body is reflected by the optical scanning mirror and irradiated onto the first magnetic element, An optical device according to any one of claims 1 to 4.

6. An optical device described in any one of claims 1 to 5, wherein the spacer layer is composed of a conductive layer, an insulator layer, or a layer including a current-carrying point formed by a conductor in a conductive material.

7. An optical device according to any one of claims 1 to 6, an optical system that determines a time difference between light emission by the light emitting unit and irradiation of the reflected light onto the first magnetic element based on the first signal and the second signal input to the circuit;

8. The optical system according to claim 7 , wherein the distance between the object and the optical device is determined based on the time difference.

9. An optical device according to any one of claims 1 to 6, an optical system for obtaining a stereoscopic image of the illuminated object from the reflected light;

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