WO2017215569A1

WO2017215569A1 - Optical scanning sensor

Info

Publication number: WO2017215569A1
Application number: PCT/CN2017/087960
Authority: WO
Inventors: 李毅; 周泽明
Original assignee: 北京飞思迈尔光电科技有限公司
Priority date: 2016-06-12
Filing date: 2017-06-12
Publication date: 2017-12-21
Also published as: CN107490792A

Abstract

An optical scanning sensor, comprising a light source, a light emitting unit (7-2), a light receiving unit (7-1), an optical receiver, a deflection unit, a curved diffuser (1), a rotating unit (9) and an angle encoder, wherein the deflection unit comprises a reflecting mirror (2) and a mirror bracket (3); the rotating unit comprises a hollow part (91) and a driving element (16); the light emitting unit comprises a basic light emitting unit, and the basic emitting unit and the light receiving unit are optical systems having transmitting and receiving at a same shaft, and are located on a same side of the mirror; light that is reflected from a target area and deviated by the mirror enters the light receiver by means of a through hole of the hollow part. The mirror is fixed to the rotating unit by means of the mirror bracket, and rotates for 360 degrees under the driving of the drive element.

Description

Optical scanning sensor

Technical field

The invention relates to an optical scanning sensor.

Background technique

A range-type optical scanning sensor (generally referred to as a range-type lidar, Lidar) requires one or more specific spatial sections (planar or tapered sections) of the environment to be used at a fixed scanning frequency (eg 25 Hz). For the distance measurement, the basic measurement method is the "time-of-flight" measurement method, that is, the laser light wave is emitted at a specific spatial angle, and the laser light wave reflected by the target surface at the spatial angle is detected, and the laser light wave is calculated from the emission to the reflection. The time of flight back, the distance value is obtained by Time-Distance-Conversion (TDC). The obtained raw measurement data is a spatial polar coordinate representation, which is a coordinate origin of a fixed point in the scanning sensor optical structure (generally located on the rotating axis of the rotating scanning structure), and the spatial angle has a fixed resolution (for example, 0.5°). ). In most application environments, in addition to the clear accuracy requirements for the measured distance values, there is also a clear accuracy requirement for the two-dimensional spatial angle at which each measurement is taken.

Summary of the invention

The main object of the present invention is to provide a compact transceiving coaxial optical scanning sensor that solves several problems in the structural design of the conventional optical scanning ranging device. Compared to conventional laser radars, the present invention has definite advantages in terms of structural strength, miniaturization design, full-angle scanning capability, and efficient use of reflected light from a target area.

The present invention provides an optical scanning sensor. The optical scanning sensor includes a light source that emits light, a light projecting unit that directs the emitted light toward the mirror, and a deflection unit that includes a mirror and a mirror holder that deflects the emitted light and directs it to the target area and The light reflected by the target area is deflected and directed to the light receiving unit; the light receiving unit directs the light reflected by the target area to the light receiver; the light receiver receives the light reflected by the target area introduced by the light receiving unit; and the rotating unit includes the hollow part and the driving a light transmissive cover capable of transmitting light reflected by the emitted light and the target area; an angle encoder for recording the angle information of the mirror; wherein the transparent cover is a curved transmissive cover, and the hollow member has a middle portion The through hole is rotatable about a central axis thereof by the driving element, the mirror and the rotating unit are connected by a mirror bracket, the light projecting unit includes a basic light projecting unit, and the basic light projecting unit and the light receiving unit are Transceiving a coaxial optical system and located at the mirror On the same side, light reflected by the target region deflected by the mirror enters the light receiver through the through hole of the hollow member. The basic light projecting unit and the light receiving unit are transmitting and receiving coaxial systems, which means that the basic light projecting unit and the light receiving unit have an optical axis coincident. Compared with the traditional transceiver off-axis system, the transmission and reception coaxial system can reduce the optical measurement dead zone. The deflection unit rotates around the central axis of the hollow member as the hollow member is driven by the drive member. In addition, the hollow member may be upper and lower portions, the lower portion is not rotated, and the upper portion is rotatable and connected to the mirror bracket.

The curved transparent cover of the present invention is a transparent casing including a light passing window, and the light passing window is capable of transmitting light and light reflected from the target area. The inner and outer surfaces of the curved transparent cover are central axis-symmetric rotating curved surfaces, and the rotating axis is the optical axis of the coaxial transceiver system, and is also the rotating axis of the rotating unit. Its busbar is an optically optimized curve, preferably a circular arc or a parabola. The curved transmissive cover converges the light reflected from the target area, and enables more reflected light to be received by the optical receiver than the conventional planar and tapered transmissive cover, thereby improving the measurement capability. The reasons are summarized as follows:

1) The ability to measure a distant target is determined by the energy of the reflected light of the target received by the light receiving unit. Since the reflected light of the distant target that can enter the light receiving unit approximates the parallel light, and the spatial energy density is substantially uniform, the reflected light energy is proportional to the outer portion of the light transmissive cover for the light receiving unit that determines the shape of the light receiving section (for example, a circular shape). The effective light-passing area, the long-distance target reflected light in the area can pass through the transparent cover and finally enter the light-receiving unit;

2) for a flat translucent cover of uniform thickness, the effective light-passing area is equal to the effective light-receiving area of the light-receiving unit;

3) For a tapered translucent cover of uniform thickness, the vertical cross section is a parallelogram, and the effective light-passing area in the vertical direction is equal to the effective light-receiving area of the light-receiving unit; the horizontal cross-section is circular, and the approximately parallel reflected light to the distant target There is a convergence effect, and the effective light-passing area in the horizontal direction is larger than the effective light-receiving area of the light-receiving unit; therefore, the effective light-passing area of the tapered transparent cover is larger than the effective light-passing area of the light-receiving unit;

4) For a spherical translucent cover of uniform thickness, the vertical section is a part of a circle, preferably semicircular, and the horizontal section is circular, and the approximately parallel reflection light of the distant target has a converging effect, so the two directions The effective light-passing area above is larger than the effective light-receiving area of the light-receiving unit, and the upper radius is smaller, the curvature is larger, and the convergence effect is more obvious. In contrast, the upper radius of the tapered light-transmissive cover is larger and the curvature is more Small, the convergence effect is relatively weak; therefore, the effective light-passing area of the spherical transparent cover is larger than the effective light-passing area of the tapered transparent cover; therefore, the spherical transparent cover enables the light-receiving unit to receive more reflected light energy, In the case of a tapered translucent cover, the range of the ranging system is increased.

5) Further, the outer curved surface and the inner curved surface of the transparent cover can be designed as different curved surfaces, so that the cross section at the light passing window is closer to the convex lens, and the convergence effect of the approximately parallel reflected light of the distant target is stronger, further Increase the effective light-passing area and increase the range of the range.

Further, a central axis of the hollow member and an optical axis of the basic light projecting unit and the light receiving unit are coincident.

Further, the basic light projecting unit and the light receiving unit are located in a through hole of the hollow member or above the through hole. The fact that all or part of the basic light projecting unit and the light receiving unit are located in the through hole belongs to the category of "the basic light projecting unit and the light receiving unit are located in the through hole of the hollow member".

Further, the basic light projecting unit employs a basic emission lens or a basic emission lens group. The emitted light emitted by the light source is directed to the mirror via a basic emitting lens or a basic emitting lens group, and is deflected by the mirror and directed to the target area.

Further, the light receiving unit employs a receiving lens or a receiving lens group. The receiving lens or receiving lens group directs light reflected from the target area deflected by the mirror toward the light receiver.

Further, a gap hole is formed in the middle of the receiving lens or the receiving lens group, and the basic transmitting lens or the basic transmitting lens group is located in a clearance hole of the receiving lens, and the basic transmitting lens coincides with the optical axis of the receiving lens .

Further, the drive element includes a power component and a transmission component. The transmission member is coupled between the power member and the hollow member such that the hollow member rotates under the driving of the power member.

Further, the power component may be any form of power supply device, preferably a motor, such as a shaft motor, etc., and the power may be transmitted to the hollow member to be rotated by a belt or gear transmission.

In addition, the rotating unit may be a hollow motor. The mirror rotates under the driving of the hollow motor. The hollow motor has a through hole in the middle thereof, and the light reflected from the target area deflected by the mirror passes through the through hole of the hollow motor and is received by the light receiver. The hollow motor needs to have low vibration and low noise characteristics at a relatively high rotational speed, so that it can be preferably applied to the optical scanning sensor.

Another object of the present invention is to provide an optical scanning sensor that prevents stray light from entering the optical receiver by providing a light blocking diaphragm, thereby improving measurement accuracy and effective range, and avoiding a blind measurement blind spot.

Further, the light blocking diaphragm is located at an upper edge of the hollow member to prevent stray light reflected by the curved transparent cover from entering the light receiver. Preferably, the light blocking diaphragm is placed vertically along the upper edge of the hollow member. Preferably, the light blocking diaphragm is a cylindrical structure. Preferably, the light blocking diaphragm is located at an outer edge of the light receiving unit.

Another object of the present invention is to provide an optical scanning sensor, which can be a top pull screw by using a top pull mechanism, fix the mirror, and adjust the angle of the mirror by adjusting the top pull structure, and simultaneously pull the top The assembly method of the screw fixing and the quick-drying high-strength glue (such as UV glue) is to ensure the accuracy of the mirror angle and the firmness of the bonding, and the equipment assembly cost is saved.

The present invention provides an optical scanning sensor that mounts the mirror to a rotating unit such that the mirror rotates with the rotating unit.

Further, the mirror bracket is composed of at least two supporting walls and at least three mounting legs, and the mirror is mounted on an upper end of the supporting wall, and the mounting leg has at least one adjusting hole and at least one fixing hole. The mirror holder is fixed to the rotating unit by a fixing device. Further, the fixing device may be a screw, and may be any other form of mechanically fixed connection. The mirror angle can be adjusted by adjusting the tension of the adjustment device in the adjustment hole. Further, the adjusting device may be a screw, and may be a universal joint, a mechanical arm or the like. The adjusting device and the fixing device function as a pulling mechanism to adjust the angle of the mirror. Preferably, the pulling mechanism is a top pull screw. The specific adjustment method is: i) fixedly connecting the mirror bracket to the mirror; ii) connecting the mirror bracket and the rotating unit through the screw in the fixing hole; iii) inserting the screw into the adjusting hole of the mounting foot, and adjusting The length of the screw adjusts the mirror angle to a preset angle. It should be noted that any other design that conforms to the form of the top pull mechanism and has the same effect as the top pull screw of the present invention should be considered as being included in the present invention.

Preferably, the support walls are evenly arranged along the edge of the mirror, and the plurality of mounting feet are equally spaced. More preferably, the mirror bracket is composed of two support walls and four mounting feet. The two supporting walls are symmetrically arranged along the two sides of the mirror, and the four mounting feet are arranged at intervals of 90°.

Further, the mounting foot further includes a glue injection groove. More preferably, the glue injection groove is a stepped structure with an upper width and a lower width. The structure of the upper width and the lower width is used to ensure that the glue injection tank has a certain role in the glue injection. The glue referred to herein may be any glue, preferably a quick-drying glue, more preferably a fast-drying type high-strength glue such as UV glue which can be rapidly solidified under ultraviolet light baking to function as a quick connecting member. The mirror bracket and the rotating unit may be fixedly connected by glue. Through the cooperation of the top pulling mechanism and the glue, the fixing of the mirror bracket and the rotating unit and the precise adjustment of the mirror angle are realized. The specific steps are: i) fixing the mirror bracket to the mirror; ii) connecting the mirror bracket to the rotating unit through the screw in the fixing hole; iii) inserting the screw into the adjusting hole of the mounting foot, and adjusting the screw Length, adjusts the mirror angle to a preset angle. The glue is injected into the glue injection groove on the mounting foot, so that the mounting foot and the rotating unit are bonded and fixed after the glue is cured. Here, the use of UV glue can reduce the curing time of the glue, thereby reducing equipment assembly time and reducing equipment assembly costs.

Further, the side end of the mirror is connected to the rotating unit through the mirror bracket, and the bottom end of the mirror is directly connected to the rotating unit. More preferably, the mirror is directly connected to the light blocking light column, so that the mirror and the rotating unit are more A fixed point that allows the mirror to remain more stable while rotating.

Further, the mirror is elliptical, and more preferably, a mirror of a special shape is designed to have an elliptical shape as above, so as to reduce the weight as much as possible without losing the light receiving area; the lower fixed edge is designed to be Three straight sides, the bottom side is connected with the rotating unit, also to reduce the weight, and at the same time facilitate the mold opening production. At the same time, the mirror and the rotating unit support at multiple points, which ensures the stability of the mirror under continuous rotation.

The optical scanning sensor provided by the present invention can realize a multi-layer scanning function by adding an extension member or the like. Further, the extension component may be an extended light projecting unit or other expansion component. Enter one Steps, the number of the extended light projecting units may be determined according to a required vertical scanning angle range (-n° to n°, n is an arbitrary positive number) and a vertical scanning angle interval m°, preferably 2n/m . The extended light projecting unit is an extended emission lens or an extended emission lens group.

Further, the extended light projecting units are arranged at equal intervals on the outer circumference of the light receiving unit.

Further, an optical axis of the extended light projecting unit and an optical axis of the light receiving unit intersect at a back focus of the light receiving unit.

Further, the angle between the optical axis of the extended light projecting unit and the optical axis of the light receiving unit is the same, which is half (n/2°) of the vertical scanning angle range.

When the optical scanning sensor is operated, when the mirror starts to rotate under the driving of the rotating unit, in the vertical scanning direction, the light emitted by the light source through each of the extended emitting lenses has the same amplitude (n°) and different phases ( The inverse sinusoid with a pitch of 360/2n° scans the space; in the horizontal scanning direction, the space is scanned by the inverse cosine curve of the same amplitude (360°) and phase (360/2n pitch) Thereby, target information in the range of the vertical angle -n° to n° and the horizontal 360° is obtained. At this time, the vertical scanning angle of the light emitted from the light source through the basic emitting lens is 0°, and the horizontal scanning angle is the same as the mirror rotation angle. In order to increase the spatial coverage density of the horizontal and vertical scanning directions, at least two auxiliary extended emitting lenses or auxiliary extended emitting lens groups may be added, and the optical axis of the auxiliary extended emitting lens or the auxiliary extended emitting lens group and the receiving lens or receiving The angle of the optical axis of the lens group is less than half of the range of the vertical scanning angle.

It should be noted that the light source of the present invention comprises a light source of any form, which may be a laser emitted by a laser emitter, which may be a microwave or an LED light source. Preferably it is a laser, the source being a semiconductor laser. The angle encoder is used to record the angle information of the rotation of the reflective lens, and the angle encoder can be a spatial angle positioning code wheel. The light receiver may be any form of photoelectric conversion device such as a light receiver circuit board, or a light beam may be temporarily collected only in the unit, and then transferred to another region by, for example, optical fiber or the like to perform a process including photoelectric conversion. The light beam reflected by the outside is received by the light receiving unit and transmitted to the data processing unit, and processed to obtain information such as the distance of the object to be measured.

DRAWINGS

FIG. 1 is a schematic diagram of an optical scanning sensor with a hollow motor as a rotating unit.

Fig. 2 is a schematic view showing the rotation of the hollow member by the shaft motor.

Figure 3 shows a schematic diagram of an optical scanning sensor for a light blocking diaphragm.

FIG. 4 is a schematic diagram of the optical path of the stray light reflected back through the transmissive cover into the blind spot of the optical receiver after the baffle stop is set.

Figure 5 is a top plan view of the mirror holder.

detailed description

The following description is presented to disclose the invention to enable those skilled in the art to practice the invention. The preferred embodiments in the following description are by way of example only, and other obvious variations will occur to those skilled in the art. The basic principles of the invention as defined in the following description may be applied to other embodiments, modifications, improvements, equivalents, and other embodiments without departing from the spirit and scope of the invention.

FIG. 1 shows an optical scanning sensor provided by the present invention. As shown in FIG. 1, an optical scanning sensor includes a spherical transmissive cover 1, a mirror 2, a mirror holder 3, a spatial angular positioning disk 6, a hollow motor 9, a receiving lens 7-1, and a basic emitting lens 7-2. The receiving lens barrel 15, the light receiver circuit board 11, the light receiver circuit board positioning mechanism 10, the basic support structure 12, the laser light emitting driving circuit board 13, and the laser light transmitting fiber 14. The laser transmission fiber 14 functions to transmit a signal of the laser emission driving circuit board. The basic transmitting lens 7-2 is integrated with the receiving lens 7-1 on one side of the mirror. The basic transmitting lens 7-2 coincides with the optical axis of the receiving lens 7-1 and coincides with the central axis of the hollow motor. The mirror holder 3 is composed of two support walls 21 and four mounting feet 22 (Fig. 5). The two support walls 21 are symmetrically arranged along both side edges of the mirror 2, and the four mounting legs 22 are arranged at intervals of 90°. The mirror 2 is fixed directly above the through hole of the hollow motor 9 by the mirror holder 3, and the mirror 2 is inclined at 45°. The hollow motor 9 supplies power to the mirror holder 3, so that the mirror holder 3 drives the mirror 2 to rotate, thereby deflecting the beam and performing rotational scanning to realize 360° scanning of the device. The mirror bracket 3 mounting leg 22 has an adjustment hole 4 and a fixing hole 5. A glue injection groove 20 is also provided on the mounting foot 22. Under the driving of the hollow motor 9, the mirror holder 3 drives the mirror 2 to rotate, so that the emitted light beam 23-1 (Fig. 4) and the received beam can be deflected by the mirror 2 to achieve a 360° scan, thereby obtaining the distance of the target area. And other information. In a preferred embodiment, the basic emitting lens and the receiving lens may be placed in a cavity of the hollow motor or partially disposed in the cavity of the hollow motor, so that space multiplexing can be realized, the whole structure is compact, and the device volume is reduced.

Compared with the traditional cone-shaped transparent cover, under the same optical engineering parameters, such as the effective optical aperture r of the receiving lens, the refractive index k of the transparent cover material, and the same thickness w of the transparent cover, the curved surface is transparent. A cover, such as a spherical transmissive cover or a parabolic translucent cover, can significantly increase the range and accuracy of the optical scanning sensor. The transparent cover of the curved surface can be a transparent cover with uniform thickness of inner and outer curved surfaces, or the outer curved surface and the inner curved surface can be designed into different curved surfaces, so that the convergence effect of the approximately parallel reflected light of the distant target is stronger, and the effective effect is further improved. Increase the range of the light receiving area. In one embodiment, under the condition of r=16mm, k=1.54, w=2mm, the outer effective light-passing area of the spherical translucent cover with the uniform thickness of the inner and outer curved surfaces is 1.3 times of the tapered translucent cover, and the corresponding optics The theoretical limit of the scanning sensor can be increased by about 14%. In the measurement test of the technical verification prototype, using the above optical engineering parameters, the same projecting optical engineering parameters and the effective laser emission power, the limit measurement distance for the 10% surface reflectance target, using the shaft motor and 62 ° inclination cone The optical scanning sensor of the translucent cover has a range of 40 meters, while the range of the compact spherical transmissive cover with a hollow motor can increase the range by 35%.

2 is a modified example of an optical scanning sensor rotation unit including a hollow member 91 having a through hole in the middle of the hollow member, and a hollow bearing member 18 having a hollow bearing member 18 for ensuring the hollow member 91 at the external motor 16 uses the gear 17 to drive the lower rotation, thereby driving the mirror holder 3 and the mirror 2 to rotate, thereby achieving 360° scanning of the device. The receiving lens barrel 15 can be placed in the cavity of the hollow member 91 or partially placed in the cavity of the hollow member 91, so that space multiplexing can be realized, the whole machine is compact in structure, and the volume of the device is reduced.

FIG. 3 shows an example of adding a light blocking diaphragm to the optical scanning sensor. A light blocking diaphragm 19 is disposed on the upper edge of the hollow motor 9. The height of the light blocking diaphragm is L, and a circle is formed around the receiving lens. shape. As shown in FIG. 4, after the light blocking diaphragm 19 is disposed, the stray light 23-2 reflected by the translucent cover 1 is blocked by the light blocking diaphragm so that the stray light entering the plane of the photosensitive surface is away from the optical receiver circuit board 11. Photosensitive surface 11-1 significantly reduces stray light levels.

In another embodiment of the present invention, an assembled connection of the mirror holder to the rotating unit and a manner of adjusting the angle of the mirror are provided. In the first step, the mirror 2 is adjusted to a desired angle, and is connected to the mirror bracket 3; in the second step, the mirror bracket 2 is fixed on the upper cover of the hollow motor 9 by a screw through a fixing hole 5 in the mounting leg 22. The glue glue 20 is filled with UV glue. Next, the angle of the mirror is fine-tuned by adjusting the screws in the four adjustment holes 4 on the mounting foot 22, and the angle of each dimension is adjusted using a pair of adjusting screws in the adjusting hole to make it more precise. The specific adjustment method is as follows: tightening the screw in the fixing hole, adjusting the screw in the adjusting hole, and adjusting the degree of close fitting of the mounting foot 22 of the mirror bracket 3 and the upper cover of the hollow motor 9 to make the mirror bracket 3 slightly move, thereby Drive the fine adjustment of the angle of the mirror 2 to the required precise angle. Then, after UV light irradiation, the UV glue between the mounting leg 22 of the mirror holder 3 and the upper cover of the hollow motor 9 is rapidly solidified, thereby ensuring that the mirror angle is accurately fixed during the assembly of the device.

In another embodiment of the present invention, an example of an extension of an optical scanning sensor implementing a multi-layer scanning function is provided. On the basis of the optical scanning sensor shown in FIG. 1, 16 extended emission lenses (not shown) are equally spaced on the outer circumference of the receiving lens 7-1, and the angle between the optical axis and the optical axis of the receiving lens is 4 °, when the mirror 2 starts to rotate under the driving of the hollow motor 9, in the vertical scanning direction, the light emitted by the light source through each of the extended emitting lenses has the same amplitude (8°) and different phases (the spacing is 22.5°). The chord curve scans the space; in the horizontal scanning direction, the space is scanned by the inverse cosine curve of the same amplitude (360°) and phase (distance 22.5°), and the optical scanning sensor can realize the vertical The scanning angle ranges from -8° to +8°, and the vertical scanning angle is 1°. The basic emission lens or the basic emission lens group in this embodiment may also be omitted.

In another embodiment of the present invention, an optical scanning sensor is provided to implement a multi-layer scanning function. An example of an extension. On the basis of the optical scanning sensor shown in FIG. 1, eight extended emission lenses (not shown) are equally spaced on the outer circumference of the receiving lens 7-1, and the angle between the optical axis and the optical axis of the receiving lens is 2 °, when the mirror 2 starts to rotate under the driving of the hollow motor 9, in the vertical scanning direction, the light emitted by the light source through each of the extended emitting lenses has the same amplitude (4°) and different phases (with a pitch of 45°). The chord curve scans the space; in the horizontal scanning direction, the space is scanned by the inverse cosine curve of the same amplitude (360°) and phase (45° pitch), and the optical scanning sensor can realize the vertical The scanning angle ranges from -4° to +4°, and the vertical scanning angle is 1°. The basic emission lens or the basic emission lens group in this embodiment may also be omitted.

Claims

An optical scanning sensor comprising:

a light source that emits light;

a light projecting unit that directs the emitted light to the mirror;

a deflection unit comprising a mirror and a mirror holder, the mirror deflecting and guiding the emitted light to the target area and deflecting the light reflected by the target area and guiding the light to the light receiving unit;

a light receiving unit that directs light reflected by the target area to the light receiver;

a light receiver that receives light reflected by a target area introduced by the light receiving unit;

a rotating unit comprising a hollow part and a driving element;

a translucent cover capable of transmitting light reflected by the emitted light and the target area;

An angle encoder for recording mirror angle information;

The light transmissive cover is a curved transmissive cover, and the hollow member has a through hole in the middle thereof, which can be rotated around the central axis by the driving component, and the mirror and the rotating unit are connected by the mirror bracket. The light projecting unit includes a basic light projecting unit, and the basic light projecting unit and the light receiving unit are light transmitting and receiving coaxial optical systems and are located on the same side of the mirror, and the light reflected by the target area deflected by the mirror The through hole of the hollow member enters the light receiver.
The optical scanning sensor according to claim 1, wherein the curved transparent cover is a spherical transmissive cover or a parabolic translucent cover.
The optical scanning sensor according to claim 1, wherein a central axis of said hollow member coincides with an optical axis of said basic light projecting unit and said light receiving unit.
The optical scanning sensor according to any one of claims 1 to 3, wherein said driving member comprises a power member and a transmission member, said transmission member being coupled between said power member and said hollow member, said hollow The component rotates under the driving of the power component.
The optical scanning sensor according to any one of claims 1 to 3, wherein the rotating unit is a hollow motor.
The optical scanning sensor of claim 1 further comprising a light blocking diaphragm positioned above said hollow member.
The optical scanning sensor according to claim 1, wherein said light projecting unit further comprises at least two extended light projecting units.
The optical scanning sensor according to claim 7, wherein said extended light projecting unit is equally spaced on an outer circumference of said light receiving unit.