JP7176331B2 - optical scanner - Google Patents

Description

The present invention relates to an optical scanning device, and more particularly to an optical scanning device that scans and irradiates an object with laser light.

The optical scanning device can be used for a projector, an optical communication switch, a laser processing device, a sensor, and the like. As an example of an optical scanning device, a distance measuring device called LIDAR (Light Detection and Ranging) is known. LIDAR is a sensor that optically measures the distance to surrounding objects. LIDAR irradiates an object with a pulsed laser beam and measures the distance from the round trip time until the laser beam reflected by the object returns. Recently, LIDAR is used for advanced driving assistance systems (ADAS) and automatic driving.

LIDAR includes, for example, a coaxial optical system system, a separate optical system system, and a CCD/CMOS image sensor system.
The coaxial optical system uses, for example, a polygon mirror or a MEMS (Micro Electro Mechanical System) mirror to scan light vertically and horizontally.

As for the separating optical system, a method has been proposed in which the output angle of light is changed by electrically changing the phase. This configuration has no moving parts and may be cheaper to manufacture than the coaxial optical system.
The optical scanning device is preferably capable of scanning various surrounding objects, and is preferably capable of scanning a wide range with laser light.

WO2017/154910

The present invention provides an optical scanning device capable of scanning light over a wide range.

An optical scanning device according to an aspect of the present invention includes a light source including a light emitting element that emits laser light, and a light source arranged in a traveling direction of the laser light emitted from the light source so that the incident laser light is substantially parallel to a first direction. a deflection device capable of deflecting and emitting in any direction; a first optical member that reflects the laser light emitted from the deflection device at an angle larger than the emission angle of the deflection device; and substantially parallel to the first direction. is the angle of reflection at the first optical member, and is a predetermined angle of reflection in a direction substantially parallel to a second direction different from the first direction, at the first optical member a second optical member that reflects the reflected laser light, the second optical member comprising a plurality of planar reflectors stacked in the first direction, each of the plurality of planar reflectors comprising: The rotation angles of the plurality of planar reflectors, which are arranged at positions rotated about a direction substantially parallel to the first direction, change from a minimum value to a maximum value at predetermined intervals in the first direction .

According to the present invention, it is possible to provide an optical scanning device capable of scanning light over a wide range.

FIG. 1 is a diagram schematically showing a configuration example of an optical scanning device according to a first embodiment of the invention. FIG. 2 is a diagram schematically showing one configuration example of the optical scanning device according to the first embodiment of the present invention. FIG. 3 is a diagram schematically showing the configuration of the deflection device (off state) of the optical scanning device of the first embodiment. FIG. 4 is a diagram schematically showing the configuration of the deflection device (on state) of the optical scanning device of the first embodiment. FIG. 5 is a diagram for explaining an example of the shape of the reflecting mirror of the first optical member in the optical scanning device of the first embodiment; FIG. 6 is a diagram for explaining an example of the positional relationship between the deflection device and the first optical member in the optical scanning device of the first embodiment; FIG. 7 is a diagram showing an example of the relationship between the incident angle and the outgoing angle of light on the reflecting mirror of the first optical member in the optical scanning device of the first embodiment. FIG. 8 is a diagram showing an example of the relationship between the incident angle and the outgoing angle of light on the reflecting mirror of the first optical member in the optical scanning device of the first embodiment. FIG. 9 is a diagram schematically showing one configuration example of the second optical member in the optical scanning device of the first embodiment. FIG. 10 is a diagram schematically showing a portion (1/2 pitch) of the second optical member in the optical scanning device of the first embodiment. FIG. 11 is a diagram of a part of the second optical member shown in FIG. 10 as viewed in the Z direction. 12A and 12B are diagrams schematically showing the movement of light emitted from the optical scanning device of the first embodiment to scan an object. FIG. 13 is a diagram schematically showing an example of the positional relationship between the first optical member and the deflection device of the optical scanning device of the second embodiment;

Hereinafter, embodiments will be described with reference to the drawings. However, the drawings are schematic or conceptual, and the dimensions and proportions of each drawing are not necessarily the same as the actual ones. Also, even when the same parts are shown in the drawings, there are cases in which the dimensional relationships and ratios are shown differently. In particular, several embodiments shown below are examples of apparatuses and methods for embodying the technical idea of the present invention. is not specified. In the following description, elements having the same functions and configurations are denoted by the same reference numerals, and redundant description will be given only when necessary.

[First embodiment]
1 and 2 are diagrams schematically showing one configuration example of the optical scanning device according to the first embodiment of the present invention.
The optical scanning device 10 of this embodiment scans a predetermined range of an object in an irradiation direction using, for example, a laser beam.

The operation of the optical scanning device 10 is controlled by a drive signal from the light source drive section 20 and a drive signal from the deflection device drive section 30 . The light source driving section 20 and the deflection device driving section 30 may be included in the optical scanning device 10 .

FIG. 1 shows the direction in which the laser beam is emitted from the light source 12 (X direction) and the direction in which the laser beam is emitted from the deflection device 14 (the direction rotated by the emission angle θo from the X direction toward the Z direction). 1 schematically shows an arrangement example of each component of the optical scanning device 10 when the optical scanning device 10 is viewed from a direction (Y direction) perpendicular to a plane (XZ plane) passing through.

FIG. 2 shows a plane (XY plane ) schematically shows an arrangement example of each component of the optical scanning device 10 when the optical scanning device 10 is viewed from a direction (Z direction) perpendicular to ).

The optical scanning device 10 includes a light source 12 , a deflection device 14 , a first optical member 16 and a second optical member 18 .
The light source 12 includes a light-emitting element (not shown) that emits, for example, laser light according to a drive signal output from the light source drive section 20 . The light emitting element emits laser light toward the deflection device 14 . The light emitting element is composed of a laser diode or the like. As the laser light, for example, infrared laser light (for example, wavelength λ=905 nm) is used. Also, the light emitting element can generate laser light as a pulse signal having a predetermined frequency (that is, pulsed laser light).

The light source driver 20 controls the operation of the light emitting elements of the light source 12 . The light source driver 20 controls the timing of pulses included in the laser light. The pulse timing includes the period of the pulse signal, the frequency of the pulse signal, and the pulse width.

The deflection device 14 is arranged in the traveling direction of the laser light emitted from the light source 12, receives the laser light emitted from the light source 12, and transmits the laser light. In addition, the deflection device 14 controls the emission angle θo of the laser light emitted from the light source 12 according to the driving signal output from the deflection device driving section 30 .

In the present embodiment, the deflection device 14 may be any device that deflects the laser light incident from the X direction in one direction (a direction substantially parallel to the Z direction) at the output angle θo. There is no need for directional and lateral deflection. In other words, the deflection device 14 can scan the incident laser light in the Z direction. The deflecting device 14 is driven so that the traveling direction of the laser light incident from the X direction is rotated by the output angle θo toward the Z direction.

The deflection device 14 comprises various optical elements with varying refractive indices. The deflection device 14 can use a thermo-optical element, an electro-optical element, an electro-absorption optical element, a free-carrier absorption optical element, a magneto-optical element, or the like. The deflection device 14 includes, for example, at least one optical element such as MEMS, LCOS (Liquid crystal on silicon), a polygon mirror, or a liquid crystal element.

In this embodiment, the deflection device 14 is composed of, for example, a liquid crystal element. The deflection device 14 includes a pair of substrates arranged facing each other and a liquid crystal layer sandwiched between the pair of substrates. On one substrate, it is possible to control the phase of light in each of a plurality of areas in front of the polarizing area.

FIG. 3 is a diagram schematically showing the configuration of the deflection device (off state) of the optical scanning device of the first embodiment.
FIG. 4 is a diagram schematically showing the configuration of the deflection device (on state) of the optical scanning device of the first embodiment.

The deflection device 14 has a liquid crystal panel. The liquid crystal panel includes substrates 21 and 22 arranged opposite to each other and a liquid crystal layer 23 sandwiched between the substrates 21 and 22 . Each of the substrates 21 and 22 is composed of a transparent substrate, for example, a glass substrate. The substrate 21 is arranged to face the light source 12, and the infrared laser from the light source 12 is incident on the liquid crystal layer 23 from the substrate 21 side. Note that the substrate 22 may be arranged on the light source 12 side.

The liquid crystal layer 23 is composed of a liquid crystal material enclosed in a region surrounded by a sealing material (not shown) that bonds the substrates 21 and 22 together. The sealing material is made of, for example, an ultraviolet curable resin, a thermosetting resin, or an ultraviolet/heat curable resin, and is cured by ultraviolet irradiation, heating, or the like after being applied to the substrate 21 or the substrate 22 in the manufacturing process. .

In the liquid crystal material, the orientation of the liquid crystal molecules is manipulated according to the electric field applied between the substrates 21 and 22, and the optical properties change. As the liquid crystal mode, for example, a homogeneous mode using positive (P-type) nematic liquid crystal is used.

That is, in the homogeneous mode, when no electric field is applied (off state), the liquid crystal molecules are oriented substantially horizontally with respect to the substrate surface, as shown in FIG. The alignment of the liquid crystal is controlled by alignment films (not shown) provided so as to sandwich the liquid crystal layer 23 . In the homogeneous mode liquid crystal molecular alignment, the long axes (directors) of the liquid crystal molecules are aligned substantially horizontally when no electric field is applied, and when an electric field is applied (on state), the director of the liquid crystal molecules is aligned as shown in FIG. tilts vertically.

As the liquid crystal mode, a vertical alignment (VA) mode using negative-type (N-type) nematic liquid crystal may be used. That is, in the VA mode, the liquid crystal molecules are oriented substantially perpendicular to the substrate surface when no electric field is applied. In the VA-mode liquid crystal molecular alignment, the long axes (directors) of the liquid crystal molecules are aligned substantially vertically when no electric field is applied, and the directors of the liquid crystal molecules are tilted horizontally when an electric field is applied.

A plurality of cell electrodes 25 arranged in a matrix are provided on the liquid crystal layer 23 side of the substrate 21 . An arbitrary number of cell electrode groups is called a unit electrode. The size of the unit electrode can be changed by changing the number of cell electrodes that compose it. A unit electrode includes one or a plurality of cell electrodes arranged in a matrix. The cell electrode 25 is composed of a transparent electrode, such as ITO (indium tin oxide).

The plurality of unit electrodes are electrically isolated from each other, and the plurality of cell electrodes 25 are electrically isolated from each other. That is, voltage control can be performed individually for each cell electrode 25, and voltage control can be performed for each unit electrode individually.

One common electrode 26 is provided on the liquid crystal layer 23 side of the substrate 22 . The common electrode 26 is planarly formed over the entire region of the liquid crystal panel where the liquid crystal layer 23 is provided. The common electrode 26 is composed of a transparent electrode, such as ITO.

As the liquid crystal panel, a transmissive liquid crystal panel (transmissive LCOS) using an LCOS (Liquid Crystal on Silicon) system may be used. By using transmissive LCOS, it becomes possible to finely process the electrodes, and a smaller liquid crystal panel can be realized. A transmissive LCOS uses a silicon substrate (or a silicon layer formed on a transparent substrate). A silicon substrate transmits light (including infrared light) having a specific wavelength or longer due to its bandgap, so LCOS can be used as a transmissive liquid crystal panel. By using LCOS, a liquid crystal panel with smaller cell electrodes can be obtained, so that the size can be further reduced. Further, since the mobility of the liquid crystal molecules is high, the laser can be scanned at high speed.

A deflection device driving section 30 outputs a drive signal for the liquid crystal display panel of the deflection device 14 . The deflection device driving section 30 applies a voltage to the common electrode 26 and each of the plurality of cell electrodes 25 to control the alignment state of liquid crystal molecules in the liquid crystal layer 23 .

First, the operation of the liquid crystal panel in the off state will be described. In the off state, no electric field is applied to the liquid crystal layer 23, and the liquid crystal molecules are aligned horizontally with respect to the substrate over the entire region of the liquid crystal layer 23. FIG. In this case, no refractive index gradient occurs in the liquid crystal layer 23 . Therefore, the infrared laser from the light source 12 enters the liquid crystal panel perpendicularly, and is emitted from the liquid crystal panel as it is without being refracted.

Next, the operation in the ON state of the liquid crystal panel will be described. In the following, an operation of scanning such that the traveling direction of the laser light rotates from the X-axis direction to the Z-axis side will be described as an example. In the ON state, a predetermined voltage is applied to the cell electrode 25 and the common electrode 26 from the deflection device driving section 30 .

For example, as shown in FIG. 4, in the liquid crystal layer 23, the liquid crystal molecules are aligned substantially vertically in a region where the applied voltage is high (high electric field), and the liquid crystal molecules are aligned in a region where the applied voltage is low (low electric field). It is oriented substantially horizontally, and in the intermediate region, it is oriented obliquely to the horizontal direction depending on the magnitude of the applied voltage. This produces a gradient in the refractive index in the direction perpendicular to the traveling direction of the infrared laser within the length W. When the infrared laser from the light source 12 is incident on the liquid crystal panel in a substantially vertical direction, refraction occurs, and the infrared laser is emitted from the liquid crystal panel at an emission angle θo.

The first optical member 16 is a reflecting mirror (θ scanning reflecting mirror) that reflects the laser beam emitted from the deflection device 14 in a predetermined direction.

FIG. 5 is a diagram for explaining an example of the shape of the reflecting mirror of the first optical member in the optical scanning device of the first embodiment;
FIG. 6 is a diagram for explaining an example of the positional relationship between the deflection device and the first optical member in the optical scanning device of the first embodiment;
Here, for example, it is assumed that the deflection device 14 is arranged at A (-L _A , 0, 0), and the laser light is emitted from there in the positive direction at the emission angle θo with respect to the X axis.

The shape of the reflecting mirror of the first optical member 16 can be represented by, for example, the following (formula 1).
x=az ² (1 formula)
Here, a is a coefficient, and the width and shape in the Y direction (depth direction) are determined according to mounting requirements.

When the reflection mirror shape of the first optical member 16 is adopted, the reflection angle β of the laser beam can be expressed by, for example, the following (Equation 2).
β=π-θo-2α (2 equations)

In the above (formula 2), α is a value represented by the following (formula 3).
α=tan ⁻¹ [1/{2(a·x _B ) ^1/2 }] (3 equations)
In the above equation (3), _xB is the X coordinate of the point where the laser beam and the reflection mirror of the first optical member 16 intersect, and is expressed by the following equation (4).

x _B = [1−2aL _A ·tan ² θo−(1−4aL _A ·tan ² θo) ^1/2 ]
/ (2a tan ² θo) (4 formulas)
As described above, the deflection device 14 can deflect the beam of laser light by the emission angle θo within the XZ plane. The output angle θo of the deflection device 14 is, for example, approximately 2° to 3°. It is reflected by the first optical member 16 at β (>output angle θo). That is, the first optical member 16 can reflect the laser light in a direction substantially parallel to the Z direction at an angle β that is larger than the emission angle θo of the deflection device 14 .

7 and 8 are diagrams showing an example of the relationship between the incident angle and the outgoing angle of light on the reflecting mirror of the first optical member in the optical scanning device of the first embodiment.

For example, when L _A =25 mm and a=0.2, when the incident angle θo of the laser beam to the first optical member 16 is 2°, the output angle β of the laser beam from the first optical member 16 is is enlarged to 19.9° with respect to the incident angle θo. Further, the enlargement ratio of the output angle β with respect to the incident angle θo of the laser beam in the first optical member 16 (output angle β/incidence angle θo) increases as the distance _LA between the deflection device 14 and the θ first optical member 16 increases. , and the larger the value of a, which represents the shape of the reflecting mirror of the first optical member 16, the larger.

The beam of laser light emitted from the first optical member 16 enters the second optical member 18 .
The second optical member 18 is a reflecting mirror (φ scanning reflecting mirror) that reflects the laser light incident from the first optical member 16 in a predetermined direction.

FIG. 9 is a diagram schematically showing one configuration example of the second optical member in the optical scanning device of the first embodiment.
FIG. 10 is a diagram schematically showing a portion (1/2 pitch) of the second optical member in the optical scanning device of the first embodiment.
FIG. 11 is a diagram of a part of the second optical member shown in FIG. 10 as viewed in the Z direction.
FIG. 10 shows, as an example, a portion (1/2 pitch) of the second optical member 18 in which a plurality of substantially rectangular parallelepiped planar reflectors 18A are stacked.

The reflecting mirror of the second optical member 18 has a spiral shape in which flat reflecting plates 18A are continuously stacked in the vertical direction (Z direction) at a pitch p. Each of the plurality of stacked planar reflectors 18A is rotated by a rotation angle γ about a direction substantially parallel to the Z direction. The rotation angle γ of the planar reflector 18A varies within the range of ±γ _MAX in the XY plane _. value) to γ _MAX (maximum value) at predetermined intervals (2γ _MAX /number of planar reflectors).

For example, as shown in FIG. 9, the second optical member 18 is configured such that the surface of the reflecting mirror changes smoothly by reducing the Z-direction width of each of the plurality of flat reflecting plates 18A.

The shape of the reflecting mirror of the second optical member 18 can be represented, for example, by the following formulas (5) to (7).
x=v・cosγ (5 equations)
y=v·sin γ (6 equations)
γ=γ _MAX [−1+(2/π)・cos ⁻¹ {cos(2πz/p)}] (Equation 7)
In addition, |v|<v0 in the above ( ₅ ) and (6). v ₀ is an implementation determined constant.

When a minute mirror piece (planar reflector 18A) in the xy plane has a rotation angle γ with respect to a direction parallel to the Y axis, the laser light coming from the negative direction of the Y axis (x=0) The beam is reflected in the direction of φ. At this time, φ can be expressed by the following (Equation 8).
φ=2γ (8 formulas)

That is, in the second optical member 18, the angle of reflection of the laser light in the direction substantially parallel to the Z direction is equal to the angle of reflection in the first optical member, and the angle of reflection of the laser light in the direction substantially parallel to the Y direction is equal to the angle of reflection of the laser light. It is twice the rotation angle γ of the flat reflector 18A into which the light is incident.
Therefore, the incident angle changes depending on the coordinate position in the Z-axis direction when the laser beam is incident on the second optical member 18 (assuming that the positional coordinate of the second optical member 18 is y=0, for example). The traveling direction of light (angle of reflection) also changes.

In this embodiment, the beam of laser light emitted from the first optical member 16 is directed to the second optical member 18 at the position of the rotational axis substantially parallel to the Z-axis direction of the plurality of planar reflectors 18A. It is assumed that the positions of the light source 12, the first optical member 16, and the second optical member 18 are adjusted so that the light is incident on the two optical members 18. The arrangement position is not limited to this.

12A and 12B are diagrams schematically showing the movement of light emitted from the optical scanning device of the first embodiment to scan an object.
As a result of reflection by the first optical member (θ scanning reflection mirror) 16 and the second optical member (φ scanning reflection mirror) 18, the laser light beam (θo deflection in the XZ plane) emitted from the deflection device 14 is x= _An example of laser scanning movement on a plane parallel to the YZ plane of LA is shown.

According to FIG. 11, the laser light emitted from the deflection device 14 was a one-dimensional deflection change (light deflected in one dimension (Z direction)), but the second optical member 16 passes through the second optical member The laser light emitted from the member 18 undergoes a two-dimensional deflection change (light deflected in two dimensions (Y direction and Z direction)). Also, the scanning range of the laser light is wider than when the laser light is emitted from the deflection device 14 .

As described above, according to the optical scanning device of this embodiment, it is possible to provide an optical scanning device capable of scanning light over a wide range.

[Second embodiment]
Next, the optical scanning device of the second embodiment will be described in detail with reference to the drawings.
In the following description, the same reference numerals are given to the same configurations as those of the optical scanning device of the above-described first embodiment, and the description thereof will be omitted.

FIG. 13 is a diagram schematically showing an example of the positional relationship between the first optical member and the deflection device of the optical scanning device of the second embodiment;
The optical scanning device 10 of this embodiment differs from the above-described first embodiment in the positional relationship between the first optical member 16 and the deflection device 14 .

For example, in the example shown in FIG. 6, the reflecting surface of the first optical member 16 is perpendicular to the traveling direction (X direction) of the laser beam at coordinates (0, y, 0). Therefore, when the laser beam emitted from the light source 12 is incident on the first optical member 16 at the coordinates (0, y, 0), the laser beam is not reflected toward the second optical member 18 and directed toward the light source 12 side. I'm going back.

Therefore, in the present embodiment, by shifting the arrangement position of the first optical member 16 to the negative side in the Z-axis direction, even when the laser light is not refracted by the deflection device 14, the laser light is emitted from the first optical member 16 as the light source. It avoids being reflected to the 12 side.

The example shown in FIG. 13 schematically shows the arrangement positions of the light source 12, the deflection device 14, the first optical member 16 and the second optical member 18 when the first optical member 16 is shifted by −A in the Z-axis direction. ing. That is, when the laser beam passes through the deflection device 14 without being deflected, the position where the laser beam is incident on the first optical member 16 and the reflecting surface of the first optical member 16 are perpendicular to the traveling direction of the laser beam. The light source 12, the deflection device 14, and the first optical member 16 are arranged so that the positions where the

In this case, similarly to FIG. 6, when the laser beam is emitted along the X-axis direction, the coordinates of incidence on the first optical member 16 are (x _B , 0, z _B −A). Further, even when the laser light is not refracted by the deflection device 14 and is incident on the first optical member 16 along the X-axis, the laser light is reflected by the second optical member 18 and reflected by the light source 12 . disappears.

Except for the above configuration, the optical scanning device of this embodiment has the same configuration as that of the above-described first embodiment. That is, according to this embodiment, it is possible to provide an optical scanning device capable of scanning light over a wide range.

In this embodiment, when the laser light passes through the deflection device 14 without being deflected, the position where the laser light is incident on the first optical member 16 and the reflecting surface of the reflecting mirror of the first optical member 16 are the positions of the laser light. The light source 12, the deflection device 14, and the first optical member 16 may be arranged so as to be different from the position perpendicular to the traveling direction. Therefore, other than the configuration shown in FIG. 13, for example, the traveling direction of the laser light emitted from the light source 12 may be arranged so as to deviate from the X direction. Even in this case, effects similar to those of the first embodiment can be obtained.

In each of the embodiments described above, an infrared laser is used as the laser light handled by the distance measuring device. However, it is not limited to this, and the distance measuring device according to the above embodiment can be applied to light other than infrared light.

The optical scanning device 10 of the above embodiment may be a distance measuring device mounted on a vehicle, but is not limited to this, and can be applied to various electronic devices having a laser beam scanning function.

That is, the optical scanning device 10 may further include a light-receiving section that detects laser light reflected by an object existing within a scanning range of the laser light. By detecting the reflected light at the light receiving unit, the optical scanning device 10 can detect the object and measure the distance to the object using the transmitted laser light and the received laser light. Become. The light-receiving section performs a laser light detection operation by restricting laser light incident on the light-receiving section to laser light incident from a specific direction.

The present invention is not limited to the above-described embodiments, and can be embodied by modifying the constituent elements without departing from the scope of the present invention. Furthermore, the above embodiments include inventions at various stages, and by appropriately combining a plurality of constituent elements disclosed in one embodiment or appropriately combining constituent elements disclosed in different embodiments, Various inventions can be constructed. For example, even if some components are deleted from all the components disclosed in the embodiments, if the problem to be solved by the invention can be solved and the effects of the invention can be obtained, these components are deleted. Embodiments can be extracted as inventions.

DESCRIPTION OF SYMBOLS 10... Optical scanning apparatus 12... Light source 14... Deflecting device 16... First optical member 18... Second optical member 18A... Planar reflector 20... Light source driving section 30... Deflecting device driving section.

Claims (7)

a light source including a light emitting element that emits laser light;
a deflection device disposed in the traveling direction of the laser light emitted from the light source, capable of deflecting and emitting the incident laser light in a direction substantially parallel to the first direction;
a first optical member that reflects the laser beam emitted from the deflection device at an angle larger than the emission angle of the deflection device;
so that the angle of reflection in the direction substantially parallel to the first direction is the angle of reflection at the first optical member and the predetermined angle of reflection in the direction substantially parallel to the second direction different from the first direction; a second optical member that reflects the laser beam reflected by the first optical member;
and
the second optical member includes a plurality of planar reflectors stacked in the first direction;
each of the plurality of planar reflectors is arranged at a position rotated about a direction substantially parallel to the first direction;
The optical scanning device , wherein the rotation angles of the plurality of planar reflectors change from a minimum value to a maximum value at predetermined intervals in the first direction . 2. The optical scanning device according to claim 1, wherein said first optical member has a hyperboloidal reflecting surface. 3. The optical scanning device according to claim ² , wherein the shape of the reflecting surface is x=az2, where z is the first direction and x is a direction substantially orthogonal to the first direction and the second direction. The angle of reflection of the laser light in a direction substantially parallel to the second direction is twice the angle of rotation.
The optical scanning device according to any one of claims 1 to 3. Let z be the first direction, x be the direction substantially orthogonal to the first direction and the second direction, γ _MAX be the maximum value of the rotation angle, and p be the pitch of the cycle at which the rotation angle changes, When the rotation angle of the second optical member is γ,
γ=γ _MAX [−1+(2/π)·cos−1{cos(2πz/p)}];
5. The optical scanning device according to claim 4. The optical scanning device according to any one of claims 1 to 5, wherein the deflection device includes a liquid crystal element. a position at which the laser beam is incident on the first optical member when the laser beam passes through the deflection device without being deflected; The light source, the deflection device, and the first optical member are arranged so that the positions are different from each other.
4. The optical scanning device according to claim 2 or 3.

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