JP7099514B2 - Scanning optical system and rider - Google Patents

Description

The present invention relates to a scanning optical system and a lidar, and more particularly to a scanning optical system for scanning light and a rider using the scanning optical system.

The scanning optical system is a projection system that reflects the laser light from the laser light source on the scanning mirror and projects it while scanning it two-dimensionally, and a photodiode that reflects the reflected light returned from an object existing within the scanning range. It is equipped with a light receiving system that receives light from such as.

The lidar is also called a laser radar, and the laser beam is scanned and projected toward the measurement space using such a scanning optical system, and the time difference between the projection and the light receiving the reflected light by the photodiode is used. Seeking distance.

In the conventional scanning optical system, there is a technique for increasing the power by combining the laser beams of a plurality of laser light sources (Japanese Patent Laid-Open No. 2005-292156). In addition, there is a technique for improving signal vs. noise (SN) and reducing the size of the device by collecting the outputs from a plurality of laser light sources at one point using a mirror that coaxializes the outputs (Japanese Patent Laid-Open No. 2004-170965).

However, in the conventional technique, when a plurality of light sources are used, the position of the mirror to be coaxialized is not fixed, and a loss occurs in the laser beam emitted when the plurality of laser light sources are coaxialized. There was a problem of doing it.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a scanning optical system capable of reducing the loss of laser light when laser light from a plurality of laser light sources is coaxialized. It is to be.

Another object of the present invention is to provide a lidar using a scanning optical system capable of reducing the loss of laser light when laser light from a plurality of laser light sources is coaxialized.

The above object of the present invention is achieved by the following means.

(1) A floodlight system having a plurality of light sources and a plurality of floodlight lenses for incident light from the plurality of light sources, respectively.
A scanning mirror that reflects the light projected from the projection system, scans and projects it toward the measurement space, reflects it on an object, and reflects the returned light.
A light receiving element having a light receiving element that receives light, and a light receiving optical element that condenses the return light reflected by the scanning mirror on the light receiving element, and a light receiving system.
A first main surface having a region in which the reflective material does not exist and a region in which the reflective material is formed surrounding the region in which the reflective material does not exist is arranged facing the scanning mirror and is projected from the projection system. A coaxialized mirror that allows the light to pass through the region where the reflecting material does not exist in the direction of the scanning mirror, and reflects the return light from the scanning mirror in the direction of the light receiving system by the reflecting material.
Have,
A scanning optical system in which the coaxial mirror is arranged so as to satisfy the following equation (1) when the distance from the emission surface of the light source to the first main surface of the coaxial mirror is ML.

f + h / tanθ ≤ ML ≤ f + h / tanθ + 2L / tanθ ... (1)
However, in the equation (1), h is the distance from the optical center of the floodlight lens toward the outer periphery of the lens, f is the focal distance of the floodlight lens, and L is the distance from the optical center of the floodlight lens to the plurality of the light sources. The distance of the light beam to the projection light axis after the light is coaxialized, θ is the projection axis in order to direct the direction of the light emitted from the light source toward the projection light axis by the projection lens. It is the angle to tilt.

(2) The plurality of light sources according to (1) above, wherein the optical axes of the light sources are arranged so as to be offset from the optical center of the respective light projectors in a direction away from the light projector axes. Scanning optical system.

(3) The direction in which the scanning mirror scans light is set as the main scanning direction, and the direction orthogonal to the main scanning direction is set as the sub-scanning direction.
The size of the area of the coaxialized mirror in the sub-scanning direction in which the reflective material does not exist is smaller than the effective diameter of the condensing optical element, and the light of the plurality of light sources is coaxialized from the optical center of the projectile lens. The scanning optical system according to (1) or (2) above, wherein the distance L of the later light beam to the light projection axis is larger.

(4) A plurality of the light receiving elements are arranged in the direction along the sub-scanning direction, and the light emitted from the plurality of light sources is a long spot luminous flux in the direction along the sub-scanning direction so as to correspond to the plurality of the light receiving elements. The scanning optical system according to (3) above, which is projected so as to be.

(5) The scanning optical system according to (3) or (4) above, wherein the emission surface of the light source is longer in the sub-scanning direction than in the main scanning direction.

(6) Of the plurality of the projection lenses, at least one is a dicing lens cut out so as to leave a portion necessary for projecting the light incident from the light source. The scanning optical system according to any one of 5).

(7) The scanning optical system according to any one of (1) to (6) above, wherein the plurality of light sources are two.

(8) At least one of the plurality of light sources is any one of (1) to (7) above, wherein the optical path of the emitted light is changed in the direction of the coaxial mirror by an optical path changing element. The scanning optical system described in 1.

(9) The scanning optical system according to any one of (1) to (8) above, wherein the light receiving element has a plurality of light receiving elements so as to have two or more pixels in the sub-scanning direction.

(10) The scanning optical system according to any one of (1) to (9) above, wherein the region of the coaxial mirror in which the reflective material does not exist is an opening.

(11) The scanning optical system according to any one of (1) to (10) above is provided.
A rider that measures the distance from the position where the light source is placed to the object based on the timing of light emission from the light source and the timing of light reception by the light receiving element.

It is sectional drawing which shows the rider which concerns on this embodiment. It is a perspective view which shows the light-receiving unit. It is a top view of the floodlight system part. It is a side view of the light projection system part seen from the direction indicated by the arrow A in FIG. It is explanatory drawing for demonstrating the 2nd example of a coaxialized mirror. It is a side view which the 2nd example of the coaxial mirror was seen from the 1st main surface side. It is explanatory drawing for demonstrating a dicing lens. It is explanatory drawing for demonstrating coaxialization. It is explanatory drawing for demonstrating operation of Embodiment. It is explanatory drawing for demonstrating the movement of a rider.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

In the scanning optical system of the present embodiment, the laser beam is reflected by the polygon mirror to scan the inside of the measurement space two-dimensionally, while the reflected light from an object or the like is reflected by the polygon mirror again and guided to the photodiode. This makes it possible to obtain information regarding a plurality of directions facing the measurement space. The rider obtains the distance from the time from when the laser beam scanned by this scanning optical system is emitted until the photodiode receives light, and the obtained distance is called a distance image, which is an object seen from the rider's installation position. 3D information such as the direction of and the distance to the object is acquired.

(Rider composition)
FIG. 1 is a cross-sectional view showing a rider according to the present embodiment.

The rider 10 includes a light emitting / receiving unit 11 and a control unit 12, and is housed in a housing 57.

The light emitting / receiving unit 11 is a scanning optical system, and the details will be described later.

The control unit 12 obtains a distance according to the time difference between the emission of the laser light from the floodlight system 501 (described later) and the light reception by the light receiving system 505 (described later). From the obtained distance, a distance image composed of a plurality of pixels showing the distribution of the distance value to the object in the measurement space is generated. Distance images are also called range point cloud data or distance maps.

The control unit 12 is a computer that controls distance calculation, laser light emission timing, rotation of the polygon mirror 53, and the like. Such a control unit 12 may be configured by, for example, a circuit such as FPGA (Field-Programmable Gate Array) or ASIC (Application Specific Integrated Circuit).

The box-shaped housing 57 is attached to a part of 100 such as a vehicle or a structure. The position to attach the rider depends on the usage pattern of the rider. The housing 57 has an upper wall 57a, a lower wall 57b facing the upper wall 57a, and a side wall 57c connecting the upper wall 57a and the lower wall 57b. An opening 57d is formed in a part of the side wall 57c, and a transparent plate 58 is attached to the opening 57d.

(Light receiving / receiving unit)
The light emitting / receiving unit 11 will be described. FIG. 2 is a perspective view showing a light emitting / receiving unit. FIG. 3 is a plan view of the floodlight system portion, and FIG. 4 is a side view of the floodlight system portion seen from the direction indicated by the arrow A in FIG.

The light emitting / receiving unit 11 has a polygon mirror 53 and a light emitting / receiving unit 50. The light emitting and receiving unit 50 includes a light emitting system 501, a coaxial mirror 503, and a light receiving system 505.

(Polygon mirror)
The polygon mirror 53 is a scanning mirror. The polygon mirror 53 has at least one mirror surface. In this embodiment, it has eight mirror surfaces. The polygon mirror 53 scans and projects the laser beam from the projection system 501 toward the measurement space by the rotating mirror surface, and also reflects the reflected light from the object. The reflected light (also referred to as return light) from the object reflected by the polygon mirror 53 is received by the light receiving system 505.

As shown in FIG. 1, the polygon mirror 53 is connected to the motor shaft 56a of the motor 56 fixed to the housing 57, and is rotated by the rotation of the motor 56. In the present embodiment, for example, the axis (rotational axis) of the motor shaft 56a extends in the Z direction, which is the vertical direction, and the XY plane formed by the X and Y directions orthogonal to the Z direction is the horizontal plane. However, the axis of the motor shaft 56a may be tilted with respect to the vertical direction.

The polygon mirror 53 has a shape in which two quadrangular pyramids are joined in opposite directions and integrated. Therefore, it has four pairs of mirror surfaces that are inclined in the direction of facing each other in pairs. The pair of mirror surfaces includes a first mirror surface M1 and a second mirror surface M2, a third mirror surface M3 and a fourth mirror surface M4, a fifth mirror surface M5 and a sixth mirror surface M6, and a seventh mirror surface M7 and a third mirror surface. 8 Mirror surface M8 (a part of each mirror surface M1 to 8 is not shown).

As shown in FIG. 1, the first mirror surface M1, the third mirror surface M3, the fifth mirror surface M5, and the seventh mirror surface M7 have different inclination angles α with respect to the polygon mirror rotation axis 52. Similarly, the second mirror surface M2, the fourth mirror surface M4, the sixth mirror surface M6, and the eighth mirror surface M8 have different inclination angles β with respect to the polygon mirror rotation axis 52. The tilt angle is an extension line of each mirror surface and angles α and β formed by a portion where the extension line intersects the polygon mirror rotation axis 52. In FIG. 1, the tilt angle α of the first mirror surface M1 and the tilt angle β of the second mirror surface M2 are shown, but the same applies to the other mirror surfaces (however, the tilt angle itself is the mirror surface as described above. Different for each). In addition, when each mirror surface is described generically or without distinction, it is referred to as a mirror surface M.

Each mirror surface M is formed by depositing a reflective film on the surface of a resin material (for example, PC (polycarbonate)) in the shape of a polygon mirror 53.

In the rider, the direction in which the laser beam is scanned by the rotation of the polygon mirror 53 is defined as the main scanning direction, and the direction orthogonal to the main scanning direction is defined as the sub-scanning direction.

(Coaxial mirror)
In FIG. 3, the projected light axis Ls of the laser light beam after coaxialization, which will be described later, is used, and the projected laser light beam is reflected from the object and is incident on the light receiving system 505 via the polygon mirror 53. Let it be Lr. The coaxial mirror 503 makes the light projection axis Ls and the return light optical axis Lr coincide with each other. A mirror that aligns the optical axes of the light projecting system 501 and the light receiving system 505 in this way is sometimes referred to as a completely coaxial mirror.

(First example of coaxial mirror)
Here, two examples of the coaxial mirror will be described. The first example is the coaxial mirror 503 shown in FIG.

As shown in FIG. 3, in the coaxialized mirror 503, a reflective material 534 that reflects laser light is formed on a transparent base material 533, for example, a first main surface 531 of a base material 533 such as glass or resin. .. The first main surface 531 is a surface facing the polygon mirror 53 and the light receiving system 505. The surface facing the floodlight system 501 is the second main surface 541.

The coaxial mirror 503 is provided with an opening 532 in a part thereof, and the laser light from the projection system 501 is passed through the opening 532. Naturally, there is no reflective material in the opening 532. As shown in FIG. 4, the size of the opening 532 is rectangular in the vertical direction ha and the horizontal direction hb in the present embodiment. The vertical direction ha is a sub-scanning direction, which is a direction in which two coaxial laser beams are lined up. The size of the opening 532 will be described later.

A reflective material 534 is formed so as to surround the opening 532. Then, the coaxial mirror 503 reflects the return light (Lr in FIG. 3) reflected from the polygon mirror 53 in the direction of the light receiving system 505 by the reflective material 534.

As described above, in the first example of the coaxialized mirror 503, by having the opening 532, the laser light from the projection system 501 is passed in the direction of the polygon mirror 53, and the return light reflected from the polygon mirror 53 is passed. Is reflected in the direction of the light receiving system 505. The position of the coaxial mirror 503 is adjusted so that the laser light from the light projecting system 501 is passed through the opening 532 and the return light is reflected in the direction of the light receiving system 505.

(Second example of coaxial mirror)
FIG. 5 is an explanatory diagram for explaining a second example of the coaxialized mirror, and is a plan view of the floodlight system 501 portion as in FIG. 3. FIG. 6 is a side view of the second example of the coaxial mirror as viewed from the first main surface side.

In the second example 5032 of the coaxialized mirror, as shown in FIG. 5A, a reflective material 534 that reflects the laser beam is formed on the first main surface 531 of the transparent base material 533, as in the first example. ing. In the arrangement of the second example 5032 of the coaxialized mirror, as in FIG. 3, the first main surface 531 faces the polygon mirror 53 and the light receiving system 505.

The second example 5032 of this coaxialized mirror has no opening and has a light transmitting portion 535 as a region in which the reflective material 534 does not exist in a part thereof. A reflective material 534 is formed so as to surround the light transmitting portion 535. In the second example 5032 of the coaxialized mirror, the laser light from the light projecting system 501 is transmitted through the light transmitting portion 535 in the direction of the polygon mirror 53.

In FIG. 5, a first example of the coaxial mirror 503 is shown as FIG. 5 (b) below FIG. 5 (a). In the second example 5032 of the coaxial mirror shown in FIG. 5 (a) and the first example of the coaxial mirror 503 shown in FIG. 5 (b), the optical axis Ls of the projection system 501 that transmits or passes through each of them is It is shown to be the same.

With reference to FIGS. 5A and 5B, the width through which light passes in the second example 5032 of the coaxial mirror is W2, and the width through which light passes in the first example of the coaxial mirror 503 is W1. The difference between these widths W1 and W2 is ΔW, and it can be seen that the second example 5032 of the coaxial mirror has a wider region through which light can be transmitted than the first example.

Therefore, in the second example 5032 of the coaxialized mirror, the opening portion 532 as in the first example is provided by providing the light transmitting portion 535 that does not form the reflective material 534 on a part of the transparent base material 533. In comparison, the reflective material 534 can have the same area and shape to transmit more light. Conversely, if the width for transmitting light is the same, the area of the reflective material can be increased, so that more return light can be reflected to the light receiving system 505.

In the second example 5032 of the coaxial mirror, other configurations and arrangements are the same as those of the first example of the coaxial mirror 503, and thus the description thereof will be omitted.

In the following description, the first example of the coaxial mirror 503 will be used, but the same applies to the second example 5032 of the coaxial mirror.

(Light projection system)
With reference to FIGS. 2 to 4, the floodlight system 501 includes a plurality of semiconductor lasers (first semiconductor laser 511, second semiconductor laser 521) that emit laser light toward the polygon mirror 53, and a plurality of corresponding semiconductor lasers. It has a projection lens (first lens 512, second lens 522) and a prism mirror 513 that reflects the laser light from the first semiconductor laser 511 in the direction of the coaxialized mirror 503.

Both the first semiconductor laser 511 and the second semiconductor laser 521 are laser light sources and emit pulsed laser light. In the present embodiment, the shape of the exit surface is longer in the sub-scanning direction (vertical direction) than in the main scanning direction (horizontal direction). This makes it easy to widen the shape of the spot luminous flux (spot luminous flux 600 described later) projected by using the two light sources in the sub-scanning direction in the present embodiment. Further, in the present embodiment, the rider 10 is installed so that the main scanning direction is the horizontal direction, which is the horizontal direction of the screen. On the other hand, the sub-scanning direction is the vertical direction.

The first lens 512 and the second lens 522, which are floodlight lenses, are collimator lenses that convert diffused light from their respective semiconductor lasers into parallel light.

In this embodiment, the first lens 512 uses a dicing lens. The dicing lens is used by cutting out only the portion necessary for converting the light into parallel light.

FIG. 7 is an explanatory diagram for explaining the dicing lens. 7 (a) shows a reference example, and FIGS. 7 (b) and 7 (c) show the present embodiment.

The lens is often used so that the light Lx0 passing on the optical axis of the semiconductor laser 901 and the optical center O of the lens 902 coincide with each other, as shown in FIG. 7A.

The laser light from the semiconductor laser 901 has a certain range. Therefore, the light Lx1 and Lx2 from the central portion of the semiconductor laser 901 are projected in parallel with the light Lx0 on the optical axis by passing through the lens 902 (the light has an angle of view of 0 degrees).

On the other hand, the light Lx11, Lx12, and Lx13 and the light Lx21, Lx22, and Lx23 emitted from one end of the semiconductor laser 901 pass through the lens 902 so as to intersect each other with respect to the light Lx0 on the optical axis. (The light is emitted in a direction that is tilted (the light is not at an angle of view of 0 degrees).

The optical center O of the lens is the optical center of the lens, not the center of the diameter in the actual shape of the lens. Therefore, the optical center of the lens does not change even if the shape in the radial direction of the lens changes.

In the present embodiment, as shown in FIG. 7B, the position of the first semiconductor laser 511 with respect to the first lens 512 is arranged at a position deviated from the optical center O of the first lens 512. Such an arrangement is called off-axis. As a result, of the light from the first semiconductor laser 511, the light La1 emitted from the end of the first semiconductor laser 511 passes through the optical center O of the first lens 512 and is perpendicular to the surface of the first lens 512. It is projected in the direction. The light La0 and the light La2 deviated from the optical center O of the first lens 512 are projected in a direction inclined with respect to the direction perpendicular to the surface of the first lens 512. This inclination becomes the sub-scanning direction viewing angle θ described later, and generally changes depending on how much the position of the semiconductor laser is shifted with respect to the optical center O of the lens (distance off the axis). That is, the larger the deviation of the optical axis of the semiconductor laser with respect to the optical center O of the lens, the larger the inclination.

The portion of the lens used in such an off-axis arrangement is only the portion through which light passes. In this embodiment, only the lower half shown from the optical center O of the first lens 512 is used.

Therefore, in the present embodiment, the first lens 512 is a dicing lens in which only the necessary portion is cut off (the unnecessary portion is cut off) as shown in FIG. 7 (c). By using such a dicing lens, the device configuration can be reduced in size and weight.

In the present embodiment, by using this dicing lens, the second lens 522 can be arranged directly under the prism mirror 513 as shown in FIGS. 2 to 4. Thereby, when the laser beams L1 and L2 (see FIG. 3) from the two laser light sources (first semiconductor laser 511 and the second semiconductor laser 521) are coaxialized, the optical axes of the two laser beams are set by the dicing lens. Can be made closer than when is not used. When coaxializing, the accuracy of coaxialization of the laser light is improved by making the optical axes of the two laser lights as close as possible, and the opening 532 (or the light transmitting portion 535, or the like) of the coaxialized mirror 503 or less. Similarly) can be made smaller. If the opening 532 can be made as small as possible, the area where the reflective material 534 is formed for light reception can be made wider.

On the other hand, the second lens 522 is used with the normal lens shape. However, the second lens 522 may also be used as a dicing lens in order to reduce the size and weight.

Although the first lens 512 is used as a dicing lens here, the present invention is not limited to such a lens form, and as shown in FIG. 7B, the first lens 512 is also a non-dicing lens. May be used.

With reference to FIGS. 2 to 4, the prism mirror 513 is an optical path changing element. As is well known, the prism mirror 513 has a reflective material 534 formed on the slope of the prism to serve as a reflective surface, and light is applied to this to change the optical path. In the present embodiment, the laser light L2 from the second semiconductor laser 521 is not emitted in the direction of the opening 532 of the coaxial mirror 503. Therefore, the prism mirror 513 is used to change the optical path of the laser light L2 from the second semiconductor laser 521 toward the opening 532 of the coaxialized mirror 503. By using the prism mirror 513 in this way, the degree of freedom in design when arranging the laser light source is increased, and it also contributes to the miniaturization of the device. The optical path changing element is not limited to the prism mirror 513, and a mirror having a reflective material formed on the base material may be used.

(Coaxial)
Coaxialization will be described.

FIG. 8 is an explanatory diagram for explaining coaxialization. Here, both the first lens 512 and the second lens 522 are shown as normal lens shapes for the sake of clarity. The lens actually used may be a dicing lens as described above. Also, the prism mirror is omitted.

In the present embodiment, as shown in FIG. 8, the center of the laser light flux after coaxialization is defined as the light projection axis Ls.

The first semiconductor laser 511 and the second semiconductor laser 521 are arranged off-axis with respect to the first lens 512 and the second lens 522, respectively. In both the first semiconductor laser 511 and the second semiconductor laser 521, the distance h (the height from the optical axis) from the optical center O of the respective lenses 512 and 522 toward the outer peripheral direction of the lens is a sub-scanning rather than the main scanning direction. Long in the direction. The diameter h of the exit surface determines the height (image height) of the image of the projected light, and is called the height h of the optical axis (also referred to as the height of the light source). The height h of the optical axis increases as the distance from the optical center of the lens increases (the height of the optical axis increases toward the direction of the arrow h in FIG. 8), and the image height of the light projected thereby also increases. It gets higher.

Of the light from the first semiconductor laser 511, the light La1 passing through the optical center O of the first lens 512 is substantially parallel to the projected optical axis Ls. On the other hand, the light La0 that coincides with the optical axis of the first semiconductor laser 511 and the light La2 from the position where the height h of the optical axis is high at the end of the first semiconductor laser 511 are separated from the optical center O of the first lens 512. Go through the position. Therefore, as shown in the figure, the light La0 and La2 are bent in the direction of the light projection axis Ls and then spread. At this time, the angle at which the light from the first semiconductor laser 511 is tilted in the direction of the projected optical axis Ls is set to θ. Since this θ determines the size of the projected light image in the sub-scanning direction, it is called the sub-scanning direction viewing angle θ. The angle θ itself is the angle between the light most greatly bent by the floodlight lens and the light projecting optical axis Ls. In the present embodiment, the angle formed by the light La2 passing through the end of the first lens 512 and the direction parallel to the floodlight axis Ls (the same direction as La1) of the light from the first semiconductor laser 511 is defined as the sub-scanning direction. The viewing angle is θ.

Similarly, among the laser light from the second semiconductor laser 521, the light Lb1 passing through the optical center O of the second lens 522 is parallel to the light projecting axis Ls and is located at a position away from the optical center O of the second lens 522. The passing light Lb0 and Lb2 are bent in the direction of the light projection axis Ls and then spread. Of the light from the second semiconductor laser 521, the angle formed by the light Lb2 passing through the end of the second lens 522 and the direction parallel to the projected optical axis Ls (the same direction as Lb1) is defined as the sub-scanning direction viewing angle θ. ..

As a result, the diffused light output from the first semiconductor laser 511 and the second semiconductor laser 521 becomes collimated parallel light and is projected in the polygon mirror 53 direction.

The coaxialized light is projected from the second main surface 541 side of the coaxialized mirror 503 toward the polygon mirror 53 through the opening 532 of the first main surface 531 in which no reflective material is present. If the position of the coaxialized mirror 503 and the width of the coaxialized light do not become an appropriate size, a part of the light is blocked without passing through the opening 532 (called vignetting), and a plurality of laser beams are emitted. Despite the coaxialization, the intensity of the laser beam is not as high as expected.

Therefore, in the present embodiment, the positional relationship between the laser light from each of the semiconductor lasers 511 and 521 and the coaxialized mirror 503 is optimized in order to effectively enhance the light intensity of the plurality of laser lights.

For this optimization, when the distance from the emission surface (origin 0) of the light source to the first main surface 531 of the coaxial mirror 503 is ML, the coaxial mirror 503 satisfies the following equation (1). To place.

f + h / tanθ ≤ ML ≤ f + h / tanθ + 2L / tanθ ... (1)
However, in the equation (1), h is the diameter of the light on the emission surface of the laser light source, f is the focal distance of the floodlight lens, and L is the optical center O of the floodlight lens after coaxializing the light of a plurality of laser light sources. The distance of the light beam to the projection light axis Ls (referred to as the distance L between the lens center and the projection light axis), θ is for directing the direction of the light emitted from the light source toward the projection light axis Ls by the projection lens. It is an angle tilted with respect to the floodlight axis Ls.

Here, the diameter h of light on the emission surface of the laser light source, the focal distance f of the lens, the distance L between the center of the lens and the light beam projection axis, and the viewing angle θ in the sub-scanning direction are the first semiconductor laser 511 and the first. The same applies to the lens 512 and the second semiconductor laser 521 and the second lens 522. Further, the origin 0 is the emission surface of the second semiconductor laser 521. The details of the origin will be described later.

The action of satisfying this equation (1) will be described. FIG. 9 is an explanatory diagram for explaining the operation of the present embodiment. In FIG. 9, since the laser beam is output as a pulse, this is schematically shown.

As shown in FIG. 9, the laser light from the first semiconductor laser 511 passes through the first lens 512 and is projected. At this time, the light La1 passing through the optical center O of the lens (at a position where the height of the optical axis is low) is projected along the light projection axis Ls. Then, the light La1 is projected through substantially the outer circumference of the coaxialized light flux at a position close to the lens. On the other hand, the light La0 and La2 that do not pass through the optical center O of the lens (the position where the height of the optical axis is high) are emitted toward the light projection axis Ls, intersect the light projection axis Ls, and then spread further. It is flooded like this. The light Lb0, Lb1 and Lb2 from the second semiconductor laser 521 are also projected in the same manner although the light is bent in the opposite direction.

Of the light of the first semiconductor laser 511 and the second semiconductor laser 521, the light La1 and Lb1 passing through the optical center O of the lens (that is, passing through a position where the height of the optical axis is low) are in the coaxialized luminous flux. Then, it advances at the position farthest from the light projection axis Ls. These light components are small because they pass through the optical center O and pass through the range where the light does not bend. On the other hand, the light composed of La0 and La2, Lb0 and Lb2 passing through a position deviated from the optical center O of the lens (that is, passing through a position where the height of the optical axis is high) occupies most of the coaxialized luminous flux. ..

Then, the luminous flux composed of La0 and La2 and Lb0 and Lb2, which occupy most of this, temporarily becomes thin, intersects each other, and then spreads. Therefore, by arranging the coaxial mirror 503 so that the opening 532 comes to the narrow portion of the luminous flux composed of La0 and La2 and Lb0 and Lb2, the kerella is eliminated (or reduced). It is possible to effectively increase the light intensity and project light. The laser light flux after being coaxialized is reflected by the polygon mirror 53, scanned and projected toward the measurement space.

The ML of the above equation (1) indicates the range of the narrowed portion of the luminous flux composed of La0 and La2 and Lb0 and Lb2. As described above, in the present embodiment, the distance ML from the origin of the coaxialized mirror 503 is set to satisfy the equation (1) (ML condition range), so that the intensity of the laser light from the two semiconductor lasers 511 and 521 is high. Can be optimized and the strength can be as expected. Further, as a result, the intensity of the reflected light from the object existing in the scanned measurement space is also increased, and the efficiency of light emission and reception is increased.

Here, an example of the distance ML from the origin of the coaxial mirror 503 will be introduced. Diameter of semiconductor laser (height of optical axis) h = 0.36 mm, focal length f = 10 mm, sub-scanning direction viewing angle θ = 2 ° (tan θ = 0.03492), distance between lens optical center and projected optical axis L = 5 mm.

When these values are applied to the equation (1), the left side of the equation (1) = 20.3091 mm and the right side = 306.672 mm. Therefore, in this example, the emission surface of the second semiconductor laser 521 is set as the origin 0, and the first main surface 531 of the coaxialized mirror 503 is arranged between 20.3091 and 306.672 mm from the origin. It is possible to increase the light intensity of the luminous flux that is coaxialized and projected. By the way, in this example, since the viewing angle in the sub-scanning direction is θ = 2 °, the two laser beams spread 2 ° from each other from the projection light axis Ls, so that the coaxialized luminous flux is sub-scanned. It will be projected toward the measurement space as a spot luminous flux with a spread of 4 ° according to the direction.

(Size of opening)
The size of the opening 532 of the coaxial mirror 503 will be described (the same applies to the second example 5032 of the coaxial mirror). In the opening 532, the size ha in the sub-scanning direction is set to be not less than the distance L between the optical center of the lens and the optical axis of the light projection and not more than the effective diameter of the condenser lens (described later). As a result, the laser light emitted from the two coaxialized semiconductor lasers 511 and 521 is not lost at the opening 532, and the loss of the reflected light (signal component) from the object due to the opening 532 is also minimized. be able to. Therefore, the SN is improved by setting the size ha of the opening 532 to such a size and setting the position of the coaxial mirror 503 described above to satisfy the equation (1).

The size Hb corresponding to the main scanning direction of the opening 532 is not particularly limited as long as it is equal to or larger than the diameter of the laser light emitted from the emission surface of one semiconductor laser (diameter in the main scanning direction). However, if it is made too large, stray light or the like coming from other parts may enter the light receiving system 505, so it is preferable to make it as small as possible.

(Optical path length)
The optical path length will be described. With reference to FIG. 3, the optical path length from the emission surface of the first semiconductor laser 511 to the first main surface 531 of the coaxial mirror 503 is defined as Ld1. The optical path length from the emission surface of the second semiconductor laser 521 to the first main surface 531 of the coaxial mirror 503 is Ld2. Ld2 is the sum of the optical path length Ld2 (1) from the emission surface of the second semiconductor laser 521 to the prism mirror 513 and the optical path length Ld2 (2) from the prism mirror 513 to the first main surface 531 of the coaxialized mirror 503. The length.

In the present embodiment, the optical path length Ld1 and the optical path length Ld2 are arranged so as to be different in order to further reduce the size of the apparatus. Then, Ld2> Ld1. When the optical path lengths of the plurality of laser beams coaxialized in this way are different, the emission surface having the longer optical path length is set as the origin. This is because, as explained using FIG. 9, most of the laser light is bent in the direction of the light projection axis Ls by passing through the lens, once intersects with the light projection axis Ls, and then from the origin. The longer the distance (farther), the wider it becomes. Therefore, by placing the origin on the side with the longer optical path length to the first main surface 531 of the coaxial mirror 503, the origin is from the origin of the coaxial mirror 503 according to the equation (1), which is suitable for the arrangement of the coaxial mirror 503. The distance ML can be obtained.

(Light receiving system)
Next, the light receiving system 505 will be described. With reference to FIGS. 2 and 3, the light receiving system 505 receives light and outputs an electric signal corresponding to the intensity of the received light, and the photodiode 551 reflects the light reflected from the coaxialized mirror 503. It has a condenser lens 552 that concentrates light on the light. The condenser lens 552 is a condenser optical element, and although the lens is shown here, a reflector (reflector) may be used in addition to the lens.

The photodiode 551 is a light receiving element, and at least one is provided. When a plurality of photodiodes 551 are provided, for example, a plurality of photodiodes having two or more pixels are installed so that the pixels are lined up in the sub-scanning direction.

The condenser lens 552 collects the light reflected from the object existing in the measurement space through the polygon mirror 53 and the light reflected from the coaxialized mirror 503 to the photodiode 551. Therefore, when a plurality of photodiodes 551 are provided, the condenser lens 552 concentrates the light in the sub-scanning direction on the plurality of photodiodes 551. Therefore, the effective diameter of the condenser lens 552 is defined as the range of the diameter of the condenser lens 552 in the sub-scanning direction that can be focused on a plurality of photodiodes 551.

(Rider's movement)
Next, the operation of the rider will be described. FIG. 10 is an explanatory diagram for explaining the operation of the rider. FIG. 10 shows a state in which the laser spot luminous flux 600 is scanned and projected in the measurement space by the lidar 10 according to the rotation of the polygon mirror 53.

As described above, the coaxialized laser light flux from the projection system 501 is projected in a pulse shape and incident on the first mirror surface M1 of the rotating polygon mirror 53. After that, the laser light beam is reflected by the first mirror surface M1, further reflected by the second mirror surface M2, and then transmitted through the transparent plate 58 toward the external measurement space, for example, as shown in FIG. It is scanned and projected as a laser spot light beam 600 (indicated by hatching) having a vertically long rectangular cross section. The vertically long shape of the laser spot luminous flux 600 is the spot luminous flux obtained according to the sub-scanning direction viewing angle θ already described.

The projected laser spot luminous flux 600 is reflected by the objects 601 and 602 existing in the measurement space and returned as reflected light. In the coaxial projection / light receiving system, the return light of the projected laser spot luminous flux 600 is detected. In the figure, the object 601 is a vehicle and the object 602 is a person. Of course, buildings and structures other than these are also detected as objects.

In the combination of the pair of mirrors of the polygon mirror 53, as described above, the four pairs have different tilt angles with respect to the polygon mirror rotation axis 52. The coaxialized laser light beam (hereinafter simply referred to as laser light beam) is first reflected by the first pair of first mirror surface M1 and second mirror surface M2, and is one of the measurement spaces according to the rotation of the polygon mirror 53. The top region Ln1 is scanned horizontally from left to right. Next, the laser light beam is reflected by the second pair of the third mirror surface M3 and the fourth mirror surface M4, and the second region Ln2 from the top of the measurement space is horizontally left in accordance with the rotation of the polygon mirror 53. Scanned from to the right. Next, the laser light beam is reflected by the third pair of the fifth mirror surface M5 and the sixth mirror surface M6, and the first region Ln3 from the top of the measurement space is horizontally left in accordance with the rotation of the polygon mirror 53. Scanned from to the right. Next, the laser luminous flux is reflected by the 4th pair of the 7th mirror surface M7 and the 8th mirror surface M8, and the lowermost region Ln4 of the measurement space is horizontally moved from left to right according to the rotation of the polygon mirror 53. Is scanned to.

In this way, one scan of the entire measurement space that can be measured by the rider 10 is completed. The images obtained by scanning the regions Ln1 to Ln4 are combined to obtain one frame FL. Then, after the polygon mirror 53 makes one rotation, it returns to the first pair of the first mirror surface M1 and the second mirror surface M2 again, and thereafter, scanning from the uppermost region Ln1 of the measurement space to the lowest region Ln4. Is repeated to obtain the next frame FL.

In FIG. 1, a part of the laser light reflected by hitting an object among the scanned and projected laser light passes through the transparent plate 58 again and is incident on the second mirror surface M2 of the polygon mirror 53 in the housing 57. It is reflected here, further reflected by the first mirror surface M1, and guided to the light receiving system 505. In the light receiving system 505, as described above, light is received by the photodiode 551, and if there are a plurality of photodiodes 551, they are detected for each pixel. At this time, the control unit 12 obtains the distance to the object based on the emission timing of the semiconductor laser and the light receiving timing of the photodiode 551. More specifically, for example, the distance from the position where the light source is installed, that is, the distance from the installation position of the rider 10 to the object due to the time difference between the time when the laser beam is emitted from the semiconductor laser and the time when the photodiode 551 receives the light. Is obtained. Such a method of obtaining a distance is called ToF (Time of Flight). As a result, it is possible to detect an object in the entire area in the measurement space and obtain a frame FL of a distance image having distance information for each pixel. The distance image may be transmitted to a distant monitor via a network (not shown) or the like and displayed, or stored in the non-volatile memory 124. Further, the obtained distance image may be stored as background image data for object detection by the background subtraction method.

According to this embodiment, the following effects are obtained.

According to the present embodiment, the positions of the two semiconductor lasers 511 and 521 and the coaxialized mirror 503 that passes or transmits each laser light from these are set to the positions satisfying the equation (1) (ML condition range). The intensity of the laser light from the two semiconductor lasers 511 and 521 can be optimized to the expected intensity.

So far, as a method of synthesizing an optical path from a laser light source, a method using a polarizing element such as a polarizing beam splitter or a half mirror has been known. However, when such a polarizing element or a mirror is used, the amount of reflected light from the object is different, so that subsequent processing is required, and the optical unit becomes large. In this embodiment, as described above, only by optimizing the position of the coaxialized mirror 503, the intensity of the coaxialized laser light in the floodlight system 501 is optimized without using a polarizing element or a half mirror. Can be done. Further, by determining not only the position of the coaxialized mirror 503 but also the size of the opening 532 and the light transmitting portion 535, the reflected light from the polygon mirror 53 can be efficiently guided to the photodiode 551, and the detection performance can be obtained. Is improved.

Further, in the present embodiment, the floodlight system 501 is composed of a prism mirror 513, a coaxialized mirror 503, a plurality of semiconductor lasers, and a lens (collimator lens) corresponding to each. Therefore, a simpler configuration can be obtained than when a polarizing element or a half mirror is used, and the projected laser luminous flux can be made uniform in the sub-scanning direction. Further, since the number of optical components is small, when the fields of view of the light projecting system 501 and the light receiving system 505 are matched, adjustment for adjusting the light emission timing, the pulse width, and the light projecting position becomes easy.

Further, in the present embodiment, since the laser spot light flux long in the sub-scanning direction can be obtained by the two light sources, the number of parts constituting the projection system 501 can be suppressed and the cost can be reduced. Further, this makes it easy to widen the projection field of view in the sub-scanning direction even with a small number of light sources.

Further, the coaxialized mirror 503 reflects the return light, which is the reflected light from the object existing in the measurement space, in the direction of the light receiving system 505. In the light receiving system 505, a plurality of photodiodes 551 can be arranged according to the length obtained by the viewing angle in the sub-scanning direction when coaxialized.

Further, in the present embodiment, the laser light of one of the plurality of semiconductor lasers bends the optical path by using the prism mirror 513. This makes it easier to avoid the problem of interference between components when arranging circuit boards and supports associated with a plurality of semiconductor lasers. In addition, since the optical axes of a plurality of semiconductor lasers can be brought close to each other in a state parallel to each other on the emission side, the size on the projection side can be compressed with respect to the sub-scanning direction, and as a result, the light receiving aperture can be increased, so that the detection distance can be extended. It is possible to reduce the size of the device.

Further, the rider 10 of the present embodiment can reduce the size and weight of the entire device configuration by using the above-mentioned light emitting and receiving unit 11, and can output the light of a plurality of semiconductor lasers together as expected. Therefore, it is possible to detect an object farther from the rider installation position and measure the distance as compared with the case where one semiconductor laser is used.

In the embodiment, two examples of the semiconductor laser (laser light source) have been described, but the number of semiconductor lasers is not limited to two, and a larger number may be provided.

Further, in the embodiment, the second semiconductor laser 521 uses a prism mirror 513 to bend an optical path in the direction of the coaxialized mirror 503, but the laser beams of the two semiconductor lasers are coaxial without using the prism mirror 513. It may be made to emit in the direction of the conversion mirror 503. Further, in this case, by using the second lens 522 corresponding to the second semiconductor laser 521 as a dicing lens, the optical axes of both can be brought closer to each other.

Further, in the embodiment, the polygon mirror 53, which is a scanning mirror, has four pairs in the rotation direction, for a total of eight faces, but the number of mirrors may be any number. Further, the form is not limited to a pair of two sheets.

Although the embodiments to which the present invention is applied have been described above, the present invention is not limited to these embodiments. In addition, the present invention can be modified in various ways based on the configurations described in the claims, and these are also within the scope of the present invention.

This application is based on Japanese Patent Application No. 2018-029918 filed on February 22, 2018, the disclosure of which is incorporated by reference in its entirety.

11 Light receiving unit,
12 Control unit,
50 Light receiving part,
53 polygon mirror,
57 housing,
501 floodlight system,
503 Coaxial mirror,
505 light receiving system,
511 1st semiconductor laser,
512 1st lens,
513 prism mirror,
521 2nd semiconductor laser,
522 second lens,
531 First main surface,
532 opening,
533 base material,
534 Reflective material,
535 light transmitting part,
551 photodiode,
552 Condensing lens.

Claims (11)

A floodlight system having a plurality of light sources and a plurality of floodlight lenses for incident light from the plurality of light sources, respectively.
A scanning mirror that reflects the light projected from the projection system, scans and projects it toward the measurement space, reflects it on an object, and reflects the returned light.
A light receiving element having a light receiving element that receives light, and a light receiving optical element that condenses the return light reflected by the scanning mirror on the light receiving element, and a light receiving system.
A first main surface having a region in which the reflective material does not exist and a region in which the reflective material is formed surrounding the region in which the reflective material does not exist is arranged so as to face the scanning mirror and is projected from the projection system. A coaxialized mirror that allows the emitted light to pass in the direction of the scanning mirror through a region in which the reflecting material does not exist, and reflects the return light from the scanning mirror in the direction of the light receiving system by the reflecting material.
Have,
A scanning optical system in which the coaxial mirror is arranged so as to satisfy the following equation (1) when the distance from the emission surface of the light source to the first main surface of the coaxial mirror is ML.
f + h / tanθ ≤ ML ≤ f + h / tanθ + 2L / tanθ ... (1)
However, in the equation (1), h is the distance from the optical center of the floodlight lens toward the outer periphery of the lens, f is the focal distance of the floodlight lens, and L is the distance from the optical center of the floodlight lens to the plurality of the light sources. The distance of the light beam to the projection light axis after the light is coaxialized, θ is the projection axis in order to direct the direction of the light emitted from the light source toward the projection light axis by the projection lens. It is the angle to tilt. The scanning optical system according to claim 1, wherein the plurality of the light sources are arranged so that the optical axis of each of the light sources is displaced from the optical center of the respective light projecting lens in a direction away from the light projecting axis. .. The direction in which the scanning mirror scans light is the main scanning direction, and the direction orthogonal to the main scanning direction is the sub-scanning direction.
The size of the area of the coaxialized mirror in the sub-scanning direction in which the reflective material does not exist is smaller than the effective diameter of the condensing optical element, and the light of the plurality of light sources is coaxialized from the optical center of the projectile lens. The scanning optical system according to claim 1 or 2, wherein the distance L of the later light beam to the projected optical axis is larger than that of the light beam. A plurality of the light receiving elements are arranged in the direction along the sub-scanning direction, and the light emitted from the plurality of light sources becomes a long spot luminous flux in the direction along the sub-scanning direction so as to correspond to the plurality of the light receiving elements. The scanning optical system according to claim 3, which is projected onto the light source. The scanning optical system according to claim 3 or 4, wherein the emission surface of the light source is longer in the sub-scanning direction than in the main scanning direction. Any one of claims 1 to 5, wherein at least one of the plurality of projection lenses is a dicing lens cut out so as to leave a portion necessary for projecting light incident from the light source. The scanning optical system described in 1. The scanning optical system according to any one of claims 1 to 6, wherein the plurality of light sources are two. The scanning optical according to any one of claims 1 to 7, wherein at least one of the plurality of light sources has an optical path of emitted light changed in the direction of the coaxial mirror by an optical path changing element. system. The scanning optical system according to any one of claims 1 to 8, wherein the light receiving element has a plurality of light receiving elements so as to have two or more pixels in the sub-scanning direction. The scanning optical system according to any one of claims 1 to 9, wherein the region of the coaxial mirror in which the reflective material does not exist is an opening. The scanning optical system according to any one of claims 1 to 10 is provided.
A rider that measures the distance from the position where the light source is placed to the object based on the timing of light emission from the light source and the timing of light reception by the light receiving element.

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