Patent Description:
Among reflecting devices, a so-called ranging sensor is proposed as an optical scanning device that measures a distance from a measurement position to a target. The ranging sensor acquires distance data by adopting a so-called time-of-fight (TOF) mode, outputting phase difference information between a light emitting timing and a light receiving timing using a pulse-modulated light source, and calculating the output phase difference information signal.

As the optical scanning device that is the reflecting device in which a measurement range is made a wide angle, there is a ranging sensor that adopts a motor and drives the motor to perform optical scanning. For example, a ranging sensor that adopts a polygon mirror as a laser light reflecting member and combines the polygon mirror with a motor is proposed. In addition, a ranging sensor that adopts a driving motor and rotates an overall configuration of an optical system provided for the ranging sensor using the driving motor is known.

Meanwhile, so-called light detection and ranging (LiDAR) is proposed as a remote sensing technique using light. LiDAR measures scattered light for laser irradiation in which light is emitted in a pulse shape, and thereby can analyze a distance to a target located at a long distance and a quality of the target. Application of LiDAR to an advanced driver assistance system (ADAS), automated driving, etc. as the optical scanning device is being investigated.

At least a camera, a laser, and LiDAR are required in an ADAS, automated driving, or the like. The camera and the laser are mainly used to find information about surroundings of a vehicle, and the LiDAR is used as backup to radar. If a vehicle itself performs safe and correct determination, the capacity to perform accurate detection of the target and classification of the target is important in the ADAS, the automated driving, or the like. For this reason, an optical scanning device acting as a reflecting device in which an area of a mirror part is large and a measurement range is made a wide angle is required.

Meanwhile, an oscillation mirror element in which a size of the mirror part is not reduced and which can cope with a high resonance frequency is proposed (e.g., Patent Literature <NUM>). This oscillation mirror element mutually couples a pair of first drive parts, and provides a coupling part in which the mirror part is coupled to a portion between the pair of first drive parts, so that the mirror part is directly coupled to the coupling part. For this reason, in comparison with a case in which the coupling part and the mirror part are indirectly coupled via a twisting bridge part having an elongated shape, rigidity of a connection portion between the mirror part and the coupling part can be increased.

However, the reflecting device in which the measurement range can be made the wide angle by adopting the motor has a problem that a geometry of the entire reflecting device is enlarged because the motor is adopted. Even when the mirror area of the reflecting device is configured to be increased, the entire reflecting device is enlarged. Especially, to adopt the optical scanning device as vehicle-mounted LiDAR, the optical scanning device needs to be made smaller than an optical scanning device that is a conventional reflecting device, and the wide angle scanning may be possible. Further, even when the optical scanning device is an optical scanning device that is a downsized reflecting device, a mirror area occupied in the entire device may be large.

The oscillation mirror element set forth in Patent Literature <NUM> has a following issue that, since the configuration in which the mirror part is directly coupled to the coupling part is adopted, and the rigidity of the connection portion between the mirror part and the coupling part is merely increased, it is not easy to realize the high resonance frequency while maintaining a large area of the mirror part.

One or some exemplary embodiments of the invention is to provide a reflecting device in which a mirror area is large, wide angle scanning is possible, and a size thereof is reduced. In addition, one or some exemplary embodiments of the invention is to provide a downsized reflecting device that is a metal mirror suitable as a ranging sensor, and has a suitable specification, particularly, as vehicle-mounted LiDAR.

The inventors of the invention achieved the invention based on the finding that an oscillation part made up of a mirror part and hinge parts of a reflecting device is formed of a material having a predetermined tensile strength, and the inventors are focused on a relation between a mass (M) of the mirror part and a resonance frequency (f<NUM>) of the oscillation part, and thereby a downsized reflecting device in which a mirror area is large and wide angle scanning is possible can be provided.

A reflecting device includes an oscillation part, and the oscillation part includes a mirror part supported on a support frame, and a hinge part engaging the mirror part and the support frame, wherein the mirror part oscillates with respect to the support frame, the hinge parts have a tensile strength of <NUM> MPa or higher, and a mass M of the mirror part and a resonance frequency f<NUM> of the oscillation part satisfy relational expression (<NUM>) below, <MAT>.

In an embodiment of the reflecting device, wherein a thinning part is formed on a surface different from a reflecting surface of the mirror part; and the mass M of the mirror part and the resonance frequency f<NUM> of the oscillation part satisfy relational expression (<NUM>) below, <MAT>.

In an embodiment of the reflecting device, wherein the mirror part includes a metal part and a reflecting part joined with the metal part; and a reflecting layer is formed on a top surface of the reflecting part.

In an embodiment of the reflecting device, wherein an area S <NUM> of the reflecting part and an area S2 of the metal part satisfy relational expression (<NUM>) below, <MAT>.

In an embodiment of the reflecting device, wherein the hinge part is formed of a metal.

In an embodiment of the reflecting device, wherein the metal part has a fixing part for fixing an electromagnetically driving magnet to the mirror part; and the reflecting device has a thinning part around the fixing part.

In an embodiment of the reflecting device, wherein a piezoelectric element is mounted on the support frame.

In an embodiment of the reflecting device, wherein the tensile strength of the hinge part is <NUM> MPa or lower.

In an embodiment of the reflecting device, wherein a dimension of a length of the hinge part which is parallel to an oscillation axis is <NUM> or less.

In an embodiment of the reflecting device, wherein the oscillation part is formed to be symmetrical with respect to a center of the mirror part.

In an embodiment of the reflecting device, wherein the hinge part being extended from a middle portion of left and right lateral surfaces of the mirror part, and is engaged with an inside of the support frame.

In an embodiment of the reflecting device, wherein a thinning rate OP (%) calculated by forming a thinning part on a surface different from a reflecting surface of the mirror part is <NUM>% or higher and <NUM>% or lower.

In an embodiment of the reflecting device, wherein the resonance frequency f<NUM> of the oscillation part is set, and an angle generated during the oscillation part is oscillated with respect to the support frame by the resonance frequency f<NUM> is set to a mechanical swing angle θMech; and the mechanical swing angle θMech ranges from <NUM> degree to <NUM> degree.

In an embodiment of the reflecting device, wherein a minimum value of the resonance frequency f<NUM> of the oscillation part is <NUM>; and a maximum value of the resonance frequency f<NUM> of the oscillation part is <NUM>.

In an embodiment of the reflecting device, further comprising: a coil, wherein the coil faces the electromagnetically driving magnet.

According to an embodiment of the invention, a reflecting device in which a mirror area is large and wide angle scanning is possible can be provided. An embodiment of the invention includes the following.

Hereinafter, embodiments of the invention will be described on the basis of the drawings.

<FIG> are perspective views illustrating an outline of a reflecting device <NUM> of a first embodiment. <FIG> is a perspective view illustrating a top surface side of the reflecting device <NUM>. As illustrated in <FIG>, the reflecting device <NUM> includes a mirror part <NUM> that is supported inside a support frame <NUM> having a plate shape, and hinge parts <NUM> that engage the mirror part <NUM> and the support frame <NUM>. The mirror part <NUM> and the hinge parts <NUM> constitute an oscillation part <NUM>. The hinge parts <NUM> extend from the middles of left and right lateral surfaces of the mirror part <NUM>, and are engaged with the inside of the support frame <NUM>. The oscillation part <NUM> is formed to be symmetrical with respect to the mirror part <NUM> to enable the mirror part <NUM> to oscillate in a well-balanced way. That is, the oscillation part <NUM> is not particularly restricted as long as it is formed such that symmetry is maintained with respect to the center of the mirror part <NUM>, and may be in point symmetry or in line symmetry with respect to the center of the mirror part <NUM>. A shape of each hinge part <NUM> need only be a shape in which the hinge part engages the mirror part <NUM> and the support frame <NUM> and can oscillate the mirror part <NUM>, and may be a rectilinear shape, a meander shape, or the like.

The support frame <NUM> is formed of a metal. The metal that can be adopted for the support frame <NUM> may be a metal that is used as a so-called metal frame and has an excellent metal fatigue property. As the metal that can be adopted for the support frame <NUM>, high-strength stainless, a special metal, or the like having a high tensile strength may be adopted. The support frame <NUM> can be obtained by forming it in a predetermined shape using pressing, etching, etc. like a typical metal frame.

The hinge parts <NUM> are twisted, and thereby the oscillation part <NUM> oscillates with respect to the support frame <NUM>. The oscillation part <NUM> oscillates about an oscillation axis <NUM> inside the support frame <NUM> at a predetermined angle. The hinge parts <NUM> may be formed of a metal having a tensile strength of <NUM> MPa or higher. When the tensile strength of the hinge parts <NUM> is <NUM> MPa or higher, an influence of stress resulting from the twisting of the hinge parts <NUM> can be avoided. When the tensile strength of the hinge parts <NUM> is <NUM> MPa or lower, fatigue resistance to the twisting of the hinge parts <NUM> is improved. The tensile strength is measured by the method of tensile test for metallic materials prescribed by JIS Z <NUM>. As a metal of which the oscillation part <NUM> is formed, SUS <NUM>, SUS <NUM>, and SUS <NUM> can be given as an example in addition to special metals.

<FIG> is a perspective views illustrating a bottom surface side of the reflecting device <NUM>. As illustrated in <FIG>, the reflecting device <NUM> includes an electromagnetically driving magnet <NUM> on a bottom surface of the mirror part <NUM>. The electromagnetically driving magnet <NUM> generates a driving force that oscillates the oscillation part <NUM> using a coil <NUM> provided to face the electromagnetically driving magnet <NUM>. The bottom surface <NUM> of the mirror part <NUM> and the electromagnetically driving magnet <NUM> are fixed not to be separated even when the oscillation part <NUM> oscillates. For example, the bottom surface <NUM> of the mirror part <NUM> and the electromagnetically driving magnet <NUM> may be bonded by a curable adhesive such as an epoxy adhesive, a silicone resin, an acrylic resin, a UV curable resin, or the like.

The electromagnetically driving magnet <NUM> is not particularly restricted as long as it can generate a magnetic field required to greatly twist the hinge parts <NUM> of the oscillation part <NUM>. For example, as the electromagnetically driving magnet <NUM>, a neodymium magnet, an alnico magnet, or a ferrite magnet, each of which has a high magnetic flux density and a very strong magnetic force, may be used.

<FIG> is a top view illustrating the mirror part <NUM> having a reflecting surface (a mirror surface) of the reflecting device <NUM>. As illustrated in <FIG>, the mirror part <NUM> functions as a reflecting surface (a mirror surface). The mirror part <NUM> reflects laser light generated by a laser light generation part (not shown). The mirror part <NUM> has a surface that is processed in whole or in part by a mirror polishing treatment or the like to function as the reflecting surface (the mirror surface). The mirror part <NUM> may include a reflecting film formed of an aluminum thin film, a gold thin film, a silver thin film, a dielectric, etc., a reflecting layer in which the reflecting film is laminated, or a reflecting layer formed of aluminum, gold, silver, or a dielectric to function as the reflecting surface (the mirror surface).

<FIG> are conceptual views illustrating a driving principle of the reflecting device <NUM>. <FIG> is a perspective view illustrating an outline of the reflecting device <NUM> that includes the mirror part <NUM> supported inside the support frame <NUM>, the electromagnetically driving magnet <NUM> on the bottom surface <NUM> of the mirror part <NUM>, and the coil <NUM> that faces the electromagnetically driving magnet <NUM>. When the reflecting device <NUM> illustrated in <FIG> is cut along broken line A-A, a sectional structure of the reflecting device <NUM> is obtained.

<FIG> is a sectional view illustrating an A-A sectional structure of the reflecting device <NUM>. As illustrated in <FIG>, the reflecting device <NUM> includes the electromagnetically driving magnet <NUM> on the bottom surface of the mirror part <NUM>, and the coil <NUM> at a position opposite to the electromagnetically driving magnet <NUM>. The electromagnetically driving magnet <NUM> generates a magnetic field M1 in an arrow direction. When an alternating current i flows to the coil <NUM>, a magnetic field M2 is generated at the coil <NUM> in an arrow direction. An attractive force and a repulsive force are generated between the electromagnetically driving magnet <NUM> and the coil <NUM>. The mirror part <NUM> is oscillated by the attractive force and the repulsive force.

Resonance of the oscillation part <NUM> is generated by applying an AC voltage of the same frequency as a resonance frequency of the oscillation part <NUM> made up of the mirror part <NUM> and the hinge parts <NUM> to the coil <NUM>. In this way, the reflecting device <NUM> can reflect laser light at a wide angle to perform optical scanning by twisting the hinge parts <NUM> constituting the oscillation part <NUM> using the resonance of the oscillation part <NUM>. Since the reflecting device <NUM> can greatly twist the oscillation part <NUM> with respect to the support frame <NUM> using the resonance, the reflecting device <NUM> has high efficiency and can obtain a great optical scanning angle. A method of generating the resonance of the oscillation part <NUM> is not particularly restricted, but a piezoelectric driving method or the like in which a piezoelectric element is mounted on the support frame <NUM>, or an electromagnetic driving method or the like may be adopted.

<FIG> is a model diagram illustrating a state of optical scanning based on the reflecting device <NUM>. The laser light L generated from the laser light generation part (not shown) is reflected by the mirror surface (the reflecting surface) provided on the top surface of the mirror part <NUM>. The hinge parts <NUM> constituting the oscillation part <NUM> are twisted, and thereby the mirror part <NUM> oscillates about the oscillation axis <NUM>. When the mirror part <NUM> is oscillated, the mirror surface (the reflecting surface) is also oscillated. As the mirror surface (the reflecting surface) of the mirror part <NUM> oscillates, an angle at which the laser light L is reflected is also changed. As the mirror part <NUM> oscillates, the optical scanning angle θ is changed.

A technical feature of the reflecting device <NUM> of an embodiment of the invention is the oscillation part <NUM> made up of the mirror part <NUM> and the hinge parts <NUM>. Hereinafter, the way the mirror part <NUM> and the hinge parts <NUM> are designed in order to maximize the mirror area of the mirror part <NUM> and enable wide angle scanning in the reflecting device <NUM> will be described.

<FIG> is a model diagram illustrating dimensional parameters required when the mirror part <NUM> and the hinge parts <NUM> of the reflecting device <NUM> are designed. As illustrated in <FIG>, the oscillation part <NUM> is made up of the mirror part <NUM> and the hinge parts <NUM>. Parameters determining a shape and size of each hinge part <NUM> are a length Lf [mm] of each hinge part <NUM>, a width 2a [mm] of each hinge part <NUM>, and a thickness 2b [mm] of each hinge part <NUM>. The length Lf [mm] of each hinge part <NUM> is a distance from an end of the mirror part <NUM> to an end of the support frame <NUM>.

The parameters determining a shape and size of each mirror part <NUM> are divided into those for determining the mirror area of the mirror surface (the reflecting surface) and those required when the mirror part <NUM> is processed. The parameters for determining the mirror area are a width Lm [mm] of the mirror part <NUM> and a length D [mm] of the mirror part <NUM>. That is, the product of the width Lm [mm] of the mirror part <NUM> and the length D [mm] of the mirror part <NUM> determines the mirror area of the mirror surface (the reflecting surface) of the mirror part <NUM>.

The mirror part <NUM> illustrated in <FIG> is configured such that the length D [mm] of the mirror part <NUM> is set to be longer than the width Lm [mm] of the mirror part <NUM>, but it is not limited thereto and can be appropriately modified according to the specification of the reflecting device <NUM>. That is, the width Lm [mm] of the mirror part <NUM> and the length D [mm] of the mirror part <NUM> may be identical in the mirror part <NUM>. In addition, the width Lm [mm] of the mirror part <NUM> may be set to be longer than the length D [mm] of the mirror part <NUM>.

The parameters required when the mirror part <NUM> is processed are a thickness tm [mm] of the mirror part <NUM>, and a thinning rate OP [%] calculated by forming a recess <NUM> and an opening <NUM> that are thinning parts in order to reduce weight of the bottom surface that is the surface different from the reflecting surface of the mirror part <NUM>. When a structure of the mirror part <NUM> is a structure in which a reflecting member (a glass substrate) is attached to a top surface <NUM> that is the reflecting surface of the mirror part, a thickness [mm] of the reflecting member (the glass substrate) and a thickness [mm] of an adhesive used when the reflecting member (the glass substrate) is attached to the top surface <NUM> of the mirror part <NUM> are also necessary parameters.

The thinning rate OP [%] may range from <NUM>% to <NUM>% in view of a mechanical strength and weight reduction of the mirror part <NUM>. When the thinning rate OP [%] is <NUM>% or more, an effect of the weight reduction of the mirror part <NUM> can be obtained and the length of each hinge part <NUM> can be reduced. When the thinning rate OP [%] is <NUM>% or less, the mechanical strength of the mirror part <NUM> can be maintained.

When the recess <NUM> and the opening <NUM> that are the thinning parts are not formed in the bottom surface <NUM> that is the surface different from the reflecting surface of the mirror part <NUM> in the structure of the mirror part <NUM>, no thinning parts need to be provided. When the structure of the mirror part <NUM> is not the structure in which the reflecting member (the glass substrate) <NUM> is attached to the top surface <NUM> of the mirror part <NUM>, the thickness [mm] of the reflecting member (the glass substrate) <NUM> and the thickness [mm] of the adhesive do not need to be provided.

As illustrated in <FIG>, the resonance frequency f<NUM> [Hz] of the oscillation part <NUM> made up of the mirror part <NUM> and the hinge parts <NUM> is set, and an angle generated when the oscillation part <NUM> oscillates with respect to the support frame <NUM> due to the resonance frequency is set to a mechanical swing angle θMech [deg.

The reflecting device <NUM> of the first embodiment is a downsized reflecting device <NUM> in which a mirror area is large and wide angle scanning is possible, and is particularly characterized in that it has a specification suitable for vehicle-mounted LiDAR. From this technical viewpoint, a maximum value MAX and a minimum value MIN of parameters required to determine a structure of the reflecting device that is made much smaller than a conventional reflecting device are set for each of the aforementioned parameters.

<FIG> is a model diagram illustrating a specification of the oscillation part <NUM> made up of the mirror part <NUM> and the hinge parts <NUM> of the reflecting device <NUM>. As a specification of the mirror part <NUM>, the width Lm of the mirror part <NUM> is selected from a range of <NUM> to <NUM>, and the length D of the mirror part <NUM> is selected from a range of <NUM> to <NUM>, so that the width and length of the mirror part <NUM> are set to Lm <NUM> [mm] × D <NUM> [mm]. Further, the minimum value MIN of the resonance frequency f<NUM> of the oscillation part <NUM> is set to <NUM>, and the maximum value MAX of the resonance frequency f<NUM> is set to <NUM>. The range of the resonance frequency f<NUM> is set from the viewpoint that the reflecting device <NUM> is set to the specification suitable for the vehicle-mounted LiDAR. The mechanical swing angle θMech [deg. ] of the reflecting device <NUM> ranges from <NUM> degree to <NUM> degree that is the specification suitable for the vehicle-mounted LiDAR, and can be set to <NUM> degree such that the wide angle scanning is possible.

The parameters required to determine the structure of the reflecting device <NUM> are used, a value of each parameter is changed, and a relation between a mass M [mg] of the mirror part <NUM> and the resonance frequency f<NUM> [kHz] of the oscillation part <NUM> is calculated.

Here, as the length Lf [mm] of each hinge part <NUM> becomes short, the reflecting device <NUM> can be downsized, and thus the mass M of the mirror part <NUM> and the resonance frequency f<NUM> of the oscillation part <NUM> when the length Lf [mm] of each hinge part <NUM> is minimum are set to optimum solutions. In the reflecting device of the embodiment of the invention, the length Lf [mm] of each hinge part <NUM> is defined as a distance between the mirror part <NUM> and the support frame <NUM> without depending on the shape of each hinge part <NUM>.

<FIG> is a graph illustrating the relation between the resonance frequency f<NUM> [kHz] of the oscillation part <NUM> and the mass M [mg] of the mirror part <NUM> in the reflecting device <NUM> of the first embodiment. As illustrated in <FIG>, as a result of changing each parameter to design the reflecting device <NUM> such that the length of each hinge part <NUM> is minimum, if the mass M [mg] of the mirror part <NUM> and the resonance frequency f<NUM> [kHz] of the oscillation part <NUM> satisfy relational expression (<NUM>) below, it is ascertained that the downsized reflecting device <NUM> in which the area of the mirror part <NUM> can be widely formed and the wide angle scanning is possible is provided. Further, it is also ascertained that, in the reflecting device <NUM> of the first embodiment, a dimension of the length of each hinge part <NUM> which is parallel to the oscillation axis <NUM> can be set to <NUM> or less.

In relational expression (<NUM>), "<NUM>*f<NUM> + <NUM>" on the right indicates a boundary line that determines an upper limit of the mass M [mg] of the mirror part <NUM>. In relational expression (<NUM>), "<NUM>*f<NUM> + <NUM>" on the left indicates a boundary line that determines a lower limit of the mass M [mg] of the mirror part <NUM>. A region enclosed by the boundary lines that determine the upper and lower limits of the mass M [mg] of the mirror part <NUM> is the specification of the mirror part <NUM> of the reflecting device <NUM> of the first embodiment.

When the mass M [mg] of the mirror part <NUM> is a region below the boundary line that determines the upper limit, the entire reflecting device can be downsized. When the mass M [mg] of the mirror part <NUM> is a region above the boundary line that determines the lower limit, a mechanical swing angle θMech [deg. ] of the oscillation part <NUM> in which the wide angle scanning is possible can be achieved.

In this way, by performing design using the parameters required for the structural design, the reflecting device <NUM> of the first embodiment is turned out to be the downsized reflecting device in which the length of each hinge part <NUM> is set to the minimum value, the mirror area of the mirror part <NUM> can be increased, and the wide angle scanning is possible. Further, the reflecting device <NUM> of the first embodiment is turned out to be the downsized reflecting device that has the specification suitable for the vehicle-mounted LiDAR by performing optimization.

Next, a method of manufacturing the reflecting device <NUM> of the first embodiment will be described. A metal is punched to be an outer frame shape of the support frame <NUM>. A resist is formed on a surface of the support frame <NUM> at a position corresponding to the oscillation part <NUM> made up of the mirror part <NUM> and the hinge parts <NUM>. The metal is processed by etching using the resist as a mask. The oscillation part <NUM>, which is included in the support frame <NUM> formed of a common metal and is made up of the mirror part <NUM> and the hinge parts <NUM>, is integrally formed by etching so as to have a predetermined shape and thickness. Reflecting devices of second to sixth embodiments to be described below are also equally manufactured. When the recess or the opening that is the thinning part is formed in the bottom surface of the mirror part <NUM>, the bottom surface is subjected to etching.

<FIG> are perspective views illustrating an outline of a reflecting device <NUM> of a second embodiment. <FIG> is a perspective view illustrating a top surface side of the reflecting device <NUM>. As illustrated in <FIG>, a basic structure of the reflecting device <NUM> is identical to that of the reflecting device <NUM> of the first embodiment.

<FIG> is a perspective view illustrating a bottom surface side of the reflecting device <NUM> of the second embodiment. As illustrated in <FIG>, the reflecting device <NUM> includes an electromagnetically driving magnet <NUM> on a bottom surface of a mirror part <NUM>. The electromagnetically driving magnet <NUM> is fixed to a recess <NUM> that is a thinning part provided the bottom surface of the mirror part <NUM>. <FIG> is an enlarged view of a bottom surface <NUM> of a mirror part <NUM>. As illustrated in <FIG>, the bottom surface <NUM> of the mirror part <NUM> is configured to leave an outer edge of the mirror part <NUM> as an outer frame, the inside of the mirror part <NUM> is thinned to form the recess <NUM>.

That is, a level difference is provided on the bottom surface <NUM> of the mirror part <NUM> by half etching, and the electromagnetically driving magnet <NUM> is fixed to the recess <NUM> of the half-etched mirror part <NUM>. A portion that is not half-etched becomes the outer edge. A width of the outer edge is not particularly restricted, but it may be identical to a width 2a of each hinge part <NUM> from the viewpoint of reducing a mass of the mirror part <NUM>.

<FIG> is a sectional view illustrating a B-B sectional structure of the reflecting device <NUM> of the second embodiment. As illustrated in <FIG>, since the recess <NUM> is formed by thinning the bottom surface <NUM> of the mirror part <NUM>, the reflecting device <NUM> of the second embodiment can largely reduce a mass corresponding to the recess <NUM> in comparison with the mass of the mirror part <NUM> of the first embodiment which is not thinned.

In the reflecting device <NUM> of the second embodiment, parameters required to determine structures of the mirror part <NUM> and the hinge parts <NUM> are set. These parameters are used, a value of each parameter is changed, and a relation between a mass M [mg] of the mirror part <NUM> and a resonance frequency f<NUM> [kHz] of the oscillation part <NUM> is calculated. The mass M of the mirror part <NUM> and the resonance frequency f<NUM> of the oscillation part <NUM> when a length Lf [mm] of each hinge part <NUM> is minimum are set to optimum solutions.

<FIG> is a graph illustrating the relation between the resonance frequency f<NUM> [kHz] of the oscillation part <NUM> and the mass M [mg] of the mirror part <NUM> in the reflecting device <NUM> of the second embodiment. As illustrated in <FIG>, as a result of changing each parameter to design the reflecting device <NUM> such that the length of each hinge part <NUM> is minimum, if the mass M [mg] of the mirror part <NUM> and the resonance frequency f<NUM> [kHz] of the oscillation part <NUM> satisfy relational expression (<NUM>) below, it is ascertained that the downsized reflecting device <NUM> in which an area of the mirror part <NUM> can be widely formed and wide angle scanning is possible is provided. Further, it is also ascertained that, in the reflecting device <NUM> of the second embodiment, a dimension of the length of each hinge part <NUM> which is parallel to an oscillation axis <NUM> can be set to <NUM> or less.

In relational expression (<NUM>), "<NUM>*f<NUM> - <NUM>" that is present on the right side indicates a boundary line that determines an upper limit of the mass M [mg] of the mirror part <NUM> having the recess <NUM>. In relational expression (<NUM>), "<NUM>*f<NUM> + <NUM>" that is present on the left side indicates a boundary line that determines a lower limit of the mass M [mg] of the mirror part <NUM> having the recess <NUM>.

A region enclosed by the boundary lines that determine the upper and lower limits of the mass M [mg] of the mirror part <NUM> having the recess <NUM> that is the thinning part is a specification of the mirror part <NUM> of the reflecting device <NUM> of the second embodiment. As illustrated in <FIG>, in the reflecting device <NUM> of the second embodiment, since the bottom surface <NUM> of the mirror part <NUM> is thinned and the recess <NUM> is formed, the upper limit of the mass of the mirror part <NUM> is lower than that in the reflecting device <NUM> of the first embodiment.

When the mass M [mg] of the mirror part <NUM> having the recess <NUM> is a region below the boundary line that determines the upper limit, the entire reflecting device can be downsized. When the mass M [mg] of the mirror part <NUM> is a region above the boundary line that determines the lower limit, a mechanical swing angle θMech [deg. ] of the oscillation part <NUM> in which the wide angle scanning is possible can be achieved.

In this way, the reflecting device <NUM> of the second embodiment can largely reduce the mass M of the mirror part <NUM> because the bottom surface <NUM> of the mirror part <NUM> is thinned to thereby form the recess <NUM>. Since the mass M of the mirror part <NUM> can be largely reduced, the length of each hinge part <NUM> of the reflecting device <NUM> can be further shortened. For this reason, the reflecting device <NUM> can be further downsized as a whole. The reflecting device <NUM> can be set to have a specification suitable, particularly, for the vehicle-mounted LiDAR, and can be used as a downsized reflecting device.

<FIG> are perspective views illustrating an outline of a reflecting device <NUM> of a third embodiment. <FIG> is a perspective view illustrating a top surface side of the reflecting device <NUM>. As illustrated in <FIG>, a basic structure of the reflecting device <NUM> is identical to that of the reflecting device <NUM> of the first embodiment.

A mirror part <NUM> of the reflecting device <NUM> of the third embodiment includes a reflecting part <NUM> on a top surface <NUM> of the mirror part <NUM>. That is, the mirror part <NUM> of the reflecting device <NUM> of the third embodiment is made up of top surface <NUM> of the mirror part <NUM> that is present on the same plane as the support frame <NUM> and the reflecting part <NUM> that is fixed to the top surface <NUM> of the mirror part <NUM>. That is, the mirror part <NUM> of the reflecting device <NUM> of the third embodiment is made up of the reflecting part <NUM> and a metal part of the top surface <NUM> of the mirror part <NUM>, and adopts a "double mirror part structure S" in which these members are joined.

In the mirror part <NUM>, the metal part constituting the top surface <NUM> of the mirror part <NUM> and the reflecting part <NUM> are joined, and a reflecting film <NUM> acting as a reflecting layer is formed on a top surface of the reflecting part <NUM>. The reflecting part <NUM> is not particularly restricted as long as it is a member that can be fixed to the mirror part <NUM> and a member capable of forming the reflecting film <NUM> on the top surface thereof. As the reflecting part <NUM>, a glass substrate may be given as an example.

<FIG> is a perspective view illustrating a bottom surface side of the reflecting device <NUM> of the third embodiment. As illustrated in <FIG>, the reflecting device <NUM> includes an electromagnetically driving magnet <NUM> on a bottom surface <NUM> of a mirror part <NUM>. Four openings 142a, 142b, 142c and 142d acting as thinning parts are provided in the bottom surface of the mirror part <NUM>. The four openings 142a to 142d are formed in the bottom surface <NUM> of the mirror part <NUM> to leave a magnet receiving surface <NUM> for fixing the electromagnetically driving magnet <NUM> to the bottom surface of the mirror part <NUM>.

As illustrated in <FIG>, the magnet receiving surface <NUM> has a circular shape to fix the electromagnetically driving magnet <NUM> and the bottom surface <NUM> of the mirror part <NUM>. That is, the magnet receiving surface <NUM> is formed on the bottom surface of the mirror part <NUM>, the magnet receiving surface <NUM> is disposed in the center of the bottom surface, and the four openings 142a to 142d are provided.

Shapes of the openings <NUM> are not particularly restricted as long as the openings <NUM> can fix the electromagnetically driving magnet <NUM> to the bottom surface <NUM> of the mirror part <NUM> and maintain a sufficient mechanical strength with respect to oscillation of an oscillation part <NUM>. The number of openings <NUM> is not also particularly restricted as long as the openings <NUM> can fix the electromagnetically driving magnet <NUM> to the bottom surface <NUM> of the mirror part <NUM> and have a sufficient mechanical strength with respect to the oscillation of an oscillation part <NUM>. All of the four openings 142a, 142b, 142c and 142d may be the same shape or different shapes.

The mirror part <NUM> of the reflecting device <NUM> of the third embodiment is characterized in that it includes the reflecting part <NUM> on the top surface <NUM> of the mirror part <NUM> and an area S1 of the reflecting part <NUM> and an area S2 of the metal part constituting the top surface <NUM> of the mirror part <NUM> satisfy relational expression (<NUM>) below.

Relational expression (<NUM>) above means that the area S1 of the reflecting part <NUM> is larger than the area S2 of the metal part that is joined with the reflecting part <NUM> and is the top surface <NUM> of the mirror part <NUM> which supports the reflecting part <NUM>. The top surface <NUM> of the mirror part <NUM> which supports the reflecting part <NUM> is thinned, and thereby an area joined with the reflecting part <NUM> is reduced. For this reason, the area S <NUM> of the reflecting part <NUM> is larger than the area S2 of the metal part.

<FIG> is a top view of the top surface side of the mirror part <NUM> of the reflecting device <NUM> of the third embodiment. As illustrated in <FIG>, the mirror part <NUM> adopts the "double mirror part structure S" that is made up of the top surface <NUM> of the mirror part <NUM> and the reflecting part (the glass substrate) <NUM> fixed to the top surface <NUM>. Since an outer frame shape of the top surface <NUM> of the mirror part <NUM> and a shape of the reflecting part (the glass substrate) <NUM> are the same, and the reflecting film <NUM> can be provided on the reflecting part (the glass substrate) <NUM>, a mirror area can be improved.

Means for fixing the top surface <NUM> of the metal part and the reflecting part (the glass substrate) <NUM> that constitute the mirror part <NUM> is not particularly restricted. For example, an epoxy-based adhesive may be coated on the top surface <NUM> of the mirror part <NUM>, the reflecting part (the glass substrate) <NUM> may be placed on the top surface <NUM> on which the epoxy-based adhesive is coated, and then the top surface <NUM> and the reflecting part (the glass substrate) <NUM> may be bonded and fixed.

In this way, since the mirror part <NUM> is thinned to form the four openings 142a to 142d that are the thinning parts, the reflecting device <NUM> of the third embodiment can largely reduce a mass M of the mirror part <NUM>. Since the mass M of the mirror part <NUM> can be largely reduced, a length of each hinge part <NUM> of the reflecting device <NUM> can be further shortened. For this reason, the reflecting device <NUM> can be downsized as a whole. As is apparent from <FIG>, the four openings 142a to 142d that are the thinning parts are formed around the mirror part <NUM> to be symmetrical. It is also ascertained that, in the reflecting device <NUM> of the third embodiment, a dimension of the length of each hinge part <NUM> which is parallel to an oscillation axis <NUM> can be set to <NUM> or less.

In the reflecting device <NUM> of the third embodiment, since the reflecting part (the glass substrate) <NUM> is formed on the top surface of the mirror part <NUM>, a degree of flatness of the mirror part <NUM> can be largely improved, and optical properties of the reflecting device can be improved. As a result, the reflecting device <NUM> of the third embodiment can be set to have a specification suitable, particularly, for the vehicle-mounted LiDAR, and can be used as a downsized reflecting device.

<FIG> is a top view of a top surface side of a mirror part <NUM> of a reflecting device <NUM> of a fourth embodiment. As illustrated in <FIG>, the mirror part <NUM> adopts the above "double mirror part structure S. " An outer frame shape of a top surface <NUM> of a metal part constituting the mirror part <NUM> and a shape of a reflecting part (a glass substrate) <NUM> are the same. In the reflecting device <NUM> of the fourth embodiment, since the mirror part <NUM> is thinned to thereby form two openings 144a and 144b that are thinning parts, a mass M of the mirror part <NUM> can be largely reduced. Since the mass M of the mirror part <NUM> can be largely reduced, a length of each hinge part <NUM> of the reflecting device <NUM> can be further shortened. As is apparent from <FIG>, the two openings 144a and 144b that are the thinning parts are formed around the mirror part <NUM> to be symmetrical. It is also ascertained that, in the reflecting device <NUM> of the fourth embodiment, a dimension of the length of each hinge part <NUM> which is parallel to an oscillation axis <NUM> can be set to <NUM> or less.

<FIG> is a top view of a top surface side of a mirror part <NUM> of a reflecting device <NUM> of a fifth embodiment. As illustrated in <FIG>, the mirror part <NUM> adopts the above "double mirror part structure S. " An outer frame shape of a metal part constituting the mirror part <NUM> and a shape of a reflecting part (a glass substrate) <NUM> are not the same. Upper and lower portions of the metal part constituting the mirror part <NUM> are removed, and the mirror part <NUM> has a metal material of which two left and right mirror parts <NUM> coupled perpendicular to hinge parts <NUM> are formed, and a circular fixing part for fixing an electromagnetically driving magnet <NUM> to the mirror part <NUM>.

In this way, in the reflecting device <NUM> of the fifth embodiment, since two openings 146a and 146b, which are removed by thinning a part of the mirror part <NUM>, are provided around the fixing part are formed, and are thinning parts, are formed, a mass M of the mirror part <NUM> can be largely reduced. Since the mass M of the mirror part <NUM> can be largely reduced, a length of each hinge part <NUM> of the reflecting device <NUM> can be further shortened. As is apparent from <FIG>, the two openings 146a and 146b that are the thinning parts are formed around the mirror part <NUM> to be symmetrical. It is also ascertained that, in the reflecting device <NUM> of the fifth embodiment, a dimension of the length of each hinge part <NUM> which is parallel to an oscillation axis <NUM> can be set to <NUM> or less.

<FIG> is a top view of a top surface side of a mirror part of a reflecting device <NUM> of a sixth embodiment. As illustrated in <FIG>, the mirror part <NUM> adopts the above "double mirror part structure S" like the third embodiment. The mirror part <NUM> is formed only by a circular fixing part by which a metal part constituting the mirror part <NUM> fixes an electromagnetically driving magnet <NUM> to the mirror part <NUM>. In this way, in the reflecting device <NUM> of the sixth embodiment, surroundings of the fixing part are thinned (thinning part <NUM>), and thereby a mass M of the mirror part <NUM> can be largely reduced. Since the mass M of the mirror part <NUM> can be largely reduced, a length of each hinge part <NUM> of the reflecting device <NUM> can be further shortened. It is also ascertained that, in the reflecting device <NUM> of the sixth embodiment, a dimension of the length of each hinge part <NUM> which is parallel to an oscillation axis <NUM> can be set to <NUM> or less.

Claim 1:
A reflecting device (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), comprising:
an oscillation part (<NUM>), comprising:
a mirror part (<NUM>), supported on a support frame (<NUM>); and
a hinge part (<NUM>), engaging the mirror part (<NUM>) and the support frame (<NUM>),
wherein the mirror part (<NUM>) oscillates with respect to the support frame (<NUM>),
the hinge part (<NUM>) has a tensile strength of <NUM> MPa or higher,
a mass M [mg]. of the mirror part (<NUM>) and a resonance frequency f<NUM> [kHz], of the oscillation part (<NUM>) satisfy relational expression (<NUM>) below, <MAT>
wherein
the oscillation part (<NUM>) is formed to be symmetrical with respect to a central axis of the mirror part (<NUM>) and
the hinge part (<NUM>) being extended from a middle portion of left and right lateral surfaces of the mirror part (<NUM>), and is engaged with an inside of the support frame (<NUM>),
wherein the reflective device is characterized in that,
the mirror part (<NUM>) includes a metal part (<NUM>) and a reflecting part (<NUM>) joined with the metal part (<NUM>);
a reflecting layer (<NUM>) is formed on a top surface (<NUM>) of the reflecting part (<NUM>);
the reflecting part (<NUM>) is joined and fixed to a part of the metal part (<NUM>), and the mirror part (<NUM>) other than the part of the metal part
is thinned which is a thinning part (<NUM>, <NUM>, 142a, 142b, 142c, 142d, 144a, 144b, 146a, 146b) formed on a surface different from a reflecting surface of the mirror part (<NUM>);
the metal part (<NUM>) has a fixing part (<NUM>) for fixing an electromagnetically driving magnet (<NUM>) to the mirror part (<NUM>), wherein the electromagnetically driving magnet (<NUM>) generates a driving force that oscillates the oscillation part (<NUM>) using a coil (<NUM>) provided to face the electromagnetically driving magnet (<NUM>); and
the thinning part (<NUM>, <NUM>, 142a, 142b, 142c, 142d, 144a, 144b, 146a, 146b) is around the fixing part (<NUM>).