JP6676974B2 - Object detection device - Google Patents

Description

  The present invention relates to an object detection device that detects an object by irradiating a light beam from a light source.

  2. Description of the Related Art In recent years, in fields such as automobiles and security robots, there has been an increasing demand for accurately detecting obstacles in a range where a moving object travels in order to prevent collision of the moving object. As a method of detecting such an obstacle, a radio wave radar that transmits a radio wave and detects a reflected wave has been proposed, but it is difficult to accurately grasp the position of a distant object from the viewpoint of resolution. is there.

  On the other hand, a laser radar employing the TOF (Time of Flight) method has already been developed. In the TOF method, the distance to the object can be measured by measuring the time required for the pulsed laser light to return after hitting the object. However, in a state where the laser beam is fixed, an object cannot be detected over a wide range. Therefore, it is necessary to scan the laser beam within a certain range.

  Patent Document 1 discloses a configuration in which a laser beam is reflected by a rotating mirror and scanning is performed toward an object. By the way, the laser radar adopting the TOF method generally detects the weak reflected light generated when irradiating a distant object with laser light, so that the amplification rate of an APD (avalanche photodiode) or the like is generally used. Uses high light receiving elements. On the other hand, it is difficult to make the reflecting surface of the mirror a perfect reflector, so that when laser light is incident on the mirror, it is inevitable that minute diffused light other than reflected light will occur, and this will cause stray light. If the light is received by a high-sensitivity light receiving element, erroneous detection may occur.

JP 2014-115182 A JP 2013-24867 A

  On the other hand, Patent Document 2 discloses a configuration in which a light beam emitted from an optical transmitter is reflected by a deflecting unit and travels to a monitoring area, and reflected light from an object is reflected by the deflecting unit and enters an optical receiver. Discloses a technique for suppressing stray light from entering an optical receiver by providing a cylindrical transmission lens barrel. However, in the configuration of Patent Document 2, stray light entering from outside the transmission barrel can be suppressed, but stray light entering the inside of the transmission barrel is repeatedly reflected on the inner peripheral surface and enters the optical receiver. Cannot be disturbed. In particular, when the diameter of the transmission lens barrel is reduced in order to reduce the size of the configuration, there is a strong possibility that stray light that has entered the inside of the transmission lens barrel will enter the optical receiver while maintaining a relatively high intensity, thereby causing erroneous detection. It is highly probable.

  The present invention has been made in view of such a problem, and it is an object of the present invention to provide an object detection device capable of effectively suppressing the influence of stray light when projecting a light beam and detecting a subject while reducing the size. Aim.

The object detection device of the present invention,
Light source,
A light beam emitted from the light source, a light projecting optical system that converts the light beam into a collimated light beam and emits the light toward an object;
A mirror unit that reflects the collimated light beam from the light projection optical system toward the object, and includes a mirror surface that reflects the reflected light beam from the object, and rotates around a rotation axis ,
A light receiving optical system that receives the reflected light beam reflected by the mirror surface,
A light receiving unit that receives the reflected light flux condensed by the light receiving optical system,
A housing provided with a rectangular cylindrical opening that allows the reflected light to pass therethrough,
The optical axis of the light projecting optical system is orthogonal to the rotation axis, the optical axis of the light receiving optical system is orthogonal to the rotation axis,
By rotating the mirror, the collimated light beam is scanned with respect to the object, and at least the cross section of the collimated light beam when entering the object is in the scanning direction of the collimated light beam. The dimension is shorter than the dimension in the scanning orthogonal direction orthogonal to it,
The light receiving unit has a light receiving surface whose dimension in a second direction corresponding to the scanning orthogonal direction is larger than a dimension in a first direction corresponding to the scanning direction,
The housing has a deflecting surface on a surface of the inner peripheral surface of the opening farther from the light source, and an intersection between an optical axis of the light projecting optical system and the mirror surface and the light receiving optical system. Stray light generated from the mirror surface between the optical axis of the system and the intersection of the mirror surface enters the opening while being inclined with respect to the optical axis of the light receiving optical system , enters the deflection surface and is reflected. When the deflecting surface is inclined in the first direction, a component of the stray light traveling in the first direction in the traveling direction of the stray light is incident on the light receiving surface of the light receiving unit as compared with before the incidence. It is to be increased later.

  Advantageous Effects of Invention According to the present invention, it is possible to provide an object detection device that can effectively suppress the influence of stray light when projecting a light beam and detecting a subject, while reducing the size.

1 is a schematic diagram showing a state in which a laser radar having a light emitting and receiving unit according to the present embodiment is mounted on a vehicle. FIG. 3 is a diagram illustrating a main part of a laser radar LR according to the present embodiment. FIG. 3 is a diagram illustrating the laser radar LR according to the present embodiment cut along a plane passing through the rotation axis RO and the optical axis. FIG. 5 is a diagram of the element holder HL2 viewed in the optical axis direction. It is a perspective view of an element holder HL2. FIG. 9 is a diagram illustrating a state in which a collimated light beam LB (indicated by hatching) emitted from the mirror unit MU scans a screen G, which is a detection range of the laser radar LR, according to rotation of the mirror unit MU. The vertical axis is a graph showing the signal intensity output from the light receiving surface PDa, and the horizontal axis is a graph showing the distance to the object. It is the figure which looked at the element holder HL2 'concerning a modification in the optical axis direction. It is a perspective view of an element holder HL2 'concerning a modification. FIG. 11 is a view of an element holder HL2 ″ according to another modification viewed in an optical axis direction. It is a perspective view of the element holder HL2 ″ concerning another modification. FIG. 4 is a sectional view similar to FIG. 3 of a laser radar according to another embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a state in which a laser radar as an object detection device according to the present embodiment is mounted on a vehicle. The laser radar LR of the present embodiment is provided behind the front window 1a of the vehicle 1 or behind the front grill 1b.

  FIG. 2 is a diagram illustrating a main part of the laser radar LR according to the present embodiment. FIG. 3 is a diagram illustrating the laser radar LR according to the present embodiment cut along a plane passing through the rotation axis RO and the optical axis. Here, the centers of the emitted light beam and the reflected light beam are indicated by solid lines or alternate long and short dash lines, but actually have a certain cross-sectional area. 2 and 3, a light emitting and receiving unit of the laser radar LR includes a semiconductor laser (light source) LD that emits a pulsed laser beam, and a collimating lens (a light emitting optical system) that converts divergent light from the semiconductor laser LD into a collimated beam. ) CL, a lens (light-receiving optical system) LS for condensing the light beam reflected from the scanned and projected object OBJ, a light-receiving unit PD for receiving the light condensed by the lens LS, and a rotating mirror unit (Mirror) MU. Here, the direction of the rotation axis RO of the mirror unit MU is defined as the Z direction, the optical axis direction of the semiconductor laser LD is defined as the X direction, and the direction orthogonal to the Z direction and the X direction is defined as the Y direction.

  The light emitting system LPS is constituted by the semiconductor laser LD and the collimating lens CL, and the light receiving system RPS is constituted by the lens LS and the light receiving unit PD. The light receiving unit PD has a light receiving surface PDa described later. The light beam emitted from the light projecting system LPS is longer in the sub-scanning angle direction than in the scanning angle direction in the measurement range of the object.

  In FIG. 3, an upper opening CSa and a lower opening CSb are formed in a box-shaped case CS fixed to a frame (not shown) of the laser radar LR. At the far end (the left end in the figure) of the upper opening CSa, a semiconductor laser LD bonded to the substrate ST is assembled. In the middle of the upper opening CSa, a light projecting optical system holder HL1 that holds the lens LS is assembled, and the laser light emitted from the semiconductor laser LD passes through the collimating lens CL as shown by a solid line, It passes through the upper opening CSa toward the mirror unit MU.

  On the other hand, the light receiving unit PD is mounted on the element holder HL2 mounted on the far end (left end in the figure) of the lower opening CSb, and the lens LS is mounted on the near end (right end in the figure) of the lower opening CSb. ing. A case is constituted by the case CS and the element holder HL2.

  FIG. 4 is a view of the element holder HL2 as viewed in the optical axis direction, and FIG. 5 is a perspective view of the element holder HL2. The element holder HL2 has a rectangular plate-shaped flange portion HL2a on which the light receiving portion PD is mounted on the back side, and a rectangular cylindrical portion HL2b joined to the front surface side of the flange portion HL2a. Here, the inside of the cylindrical portion HL2b fitted into the lower opening CSb forms an opening. Holes HL2p near the four corners of the flange portion HL2a are for inserting screws (not shown) for fixing the element holder HL2 to the case CS.

  A rectangular opening (also referred to as an opening) HL2c is formed in the center of the flange HL2a surrounded by the cylindrical portion HL2b. The light receiving surface PDa of the light receiving unit PD is exposed from the opening HL2c when viewed from the cylindrical portion HL2b side. The region other than the light receiving surface PDa exposed from the opening HL2c is a non-detection region where no light is detected. In a state where the light receiving surface PDa is assembled in the case CS, the dimension in the second direction (here, the Z direction) corresponding to the scanning orthogonal direction is larger than the dimension (horizontal) in the first direction (here, the Y direction). (Vertical) is larger.

On the inner peripheral surface of the cylindrical portion HL2b, the surface (lower side in FIGS. 4 and 5) away from the semiconductor laser LD is a deflection surface HL2d. More specifically, the deflection surface HL2d is parallel to the X direction, but is inclined at an inclination angle θ with respect to the Y direction. The inner peripheral surface of the cylindrical portion HL2b other than the deflection surface HL2d is parallel to the Y direction or the Z direction. Note that it is optional to incline the polarization plane HL2d also in the X direction. Here, the optical axis of the light projecting system LPS and the optical axis of the light receiving system RPS are parallel to each other and spaced apart in the Z direction (second direction), as shown in FIG. The dimension in the Z direction (second direction) of the light receiving surface PDa in the light receiving unit PD is H, the dimension in the Y direction (first direction) is W, and the inner dimension of the opening HL2c of the case CS (the optical axis of the light receiving system RPS). When the direction is defined as D at the position overlapping the center line in the Y direction on the light receiving surface PDa of the light receiving unit PD when viewed in the direction, the inclination angle θ that satisfies the following expression (1) is set. Is preferred. Thus, stray light traveling toward the central axis (X direction) of the cylindrical portion HL2b at the position of the light receiving portion PD can be reliably released to the outside of the light receiving surface.
(2 × tan α × tan θ) / D> W (1)
However,
θ: inclination angle θ (°) of the deflection surface HL2d with respect to the Y direction
α: diffusion angle (°) of stray light LST generated from second mirror surface M2 (or first mirror surface M1). Here, assuming that stray light LST becomes Lambertian diffusion, with respect to the optical axis of light receiving system RPS. The angle at which the intensity in the direction inclined by the diffusion angle is の of the maximum intensity, generally 60 °.

  In FIG. 2, a mirror unit MU having a substantially rectangular cylindrical shape is rotatably held around a rotation axis RO which is an axis, and four trapezoidal first mirror surfaces M1 are arranged on a lower outer periphery. In opposition thereto, four trapezoidal second mirror surfaces M2 are arranged on the upper outer periphery. The crossing angles of the first mirror surface M1 and the second mirror surface M2 which are vertically paired are different from each other. The optical axis of the light projecting system LPS is orthogonal to the rotation axis RO of the mirror unit MU, and the optical axis of the light receiving system RPS is parallel to the optical axis of the light projecting system LPS. The mirror unit MU is driven to rotate about a rotation axis RO by a motor attached to a frame (not shown).

  Next, the ranging operation of the laser radar LR according to the present embodiment will be described. 2 and 3, divergent light emitted intermittently in a pulse form from a semiconductor laser LD is converted into a parallel light flux by a collimating lens CL, and as shown by a solid line, a first mirror surface M1 of a rotating mirror unit MU. Is reflected at the point P1, and travels along the rotation axis RO, and is further reflected at the point P2 of the second mirror surface M2 and is scanned and projected toward the object OBJ.

  FIG. 6 is a diagram illustrating a state in which the collimated light beam LB (indicated by hatching) emitted in accordance with the rotation of the mirror unit MU scans the screen G that is the detection range of the laser radar LR. In the combination of the first mirror surface M1 and the second mirror surface M2 of the mirror unit MU, the intersection angles are different. The collimated light beam LB is sequentially reflected by the first and second mirror surfaces M1 and M2 that rotate, but the collimated light beam LB is first reflected by the first pair of first and second mirror surfaces M1 and M2. The light beam LB scans the uppermost region Ln1 of the screen G from left to right in the horizontal direction according to the rotation of the mirror unit MU. Next, the collimated light beam LB reflected by the second pair of the first mirror surface M1 and the second mirror surface M2 moves the second region Ln2 from the top of the screen G horizontally to the left according to the rotation of the mirror unit MU. From right to right. Next, the collimated light beam LB reflected by the third pair of the first mirror surface M1 and the second mirror surface M2 horizontally moves the third region Ln3 from the top of the screen G leftward according to the rotation of the mirror unit MU. From right to right. Next, the collimated light beam LB reflected by the fourth pair of the first mirror surface M1 and the second mirror surface moves the lowermost area Ln4 of the screen G horizontally from left to right in accordance with the rotation of the mirror unit MU. Is scanned. Thereby, scanning of one screen is completed. Then, after the mirror unit MU makes one rotation, if the first pair of the first mirror surface M1 and the second mirror surface M2 returns, the scanning from the top of the screen G is repeated again.

  2 and 3, of the light beams scanned and projected, the reflected light beam reflected on the object OBJ is incident on a point P3 on the second mirror surface M2 of the mirror unit MU, as indicated by a dashed line, and is reflected there. Then, the light travels along the rotation axis RO, is further reflected at the point P4 of the first mirror surface M1, is condensed by the lens LS, and passes through the inside of the lower opening CSb and the inside of the cylindrical portion HL2b of the element holder HL2. The light passes through and is detected by the light receiving surface PDa of the light receiving unit PD. A signal generated by the light receiving surface PDa receiving the light is transmitted from the light receiving unit PD to a control circuit (not shown), where the difference between the light emitting time of the semiconductor laser LD and the light receiving time of the light receiving unit PD is used to determine the target object. The distance is measured. Thus, the object OBJ can be detected in the entire range on the screen G.

  By the way, the mirror surfaces M1 and M2 of the mirror unit MU are formed, for example, by depositing a reflection film on a resin molding, but it is difficult to make the mirror surfaces M1 and M2 complete reflection surfaces. Therefore, when the laser beam enters the mirror surfaces M1 and M2, it is inevitable that a small amount of diffused light is generated. On the other hand, the reflected light from the object incident on the mirror unit MU is also very small, so that it may be difficult to distinguish the reflected light.

  For example, it is assumed that the collimated light beam LB emitted from the light projecting system LPS radially generates diffused light when entering the point P2 in FIG. Then, any one of the diffused lights becomes stray light LST and travels along the plane shown in FIG. 3 as shown by the dotted line, and is reflected on the point P5 of the first mirror surface M1, and then enters the lens LS. Then, the light may be condensed and further reflected on the inner peripheral surface of the element holder HL2 to reach the light receiving surface PDa.

  FIG. 7 is a graph in which the vertical axis indicates the signal intensity output from the light receiving surface PDa, and the horizontal axis indicates the distance to the object. In the figure, a graph A shows an example of the signal intensity based on the reflected light from the object, and a graph B shows an example of the signal intensity based on the stray light LST indicated by a dotted line in FIG. The graph C is a combination of the graphs A and B. When stray light occurs, a combined signal as shown in the graph C is input to a control circuit (not shown).

  Here, the control circuit determines that there is an object when the threshold value TH is exceeded. Therefore, based on the signal of the graph C, the midpoint D2 of the two intersections where the threshold value TH and the waveform C intersect is recognized as the distance to the object. On the other hand, based on the graph A based only on the reflected light from the actual object when no stray light is generated, the midpoint D1 of the two intersections where the threshold TH and the waveform A intersect is the true distance. Therefore, the control circuit may erroneously recognize the distance to the object by (D1-D2). Therefore, how to suppress stray light is an issue.

  In order to solve such a problem, in the present embodiment, the deflection surface HL2d is provided on the element holder HL2. Referring to FIG. 3, among the diffused light generated at the point P2, the stray light LST that passes through the elongated lower opening CSb of the case CS and reaches the light receiving surface PDa of the light receiving unit PD substantially along the plane shown in FIG. It can be said that it is limited to those that progress. Further, since the point P5 where the stray light LST enters exists between the point P1 and the point P4 from a geometrical viewpoint, the stray light LST reflected at the point P5 is incident obliquely with respect to the optical axis of the light receiving system RPS. Most of the light is reflected on the deflection surface HL2d of the element holder HL2.

  Assuming that the deflecting surface HL2d is parallel to the Y direction (θ = 0 °), the stray light LST traveling along the plane of FIG. 3 is reflected by the deflecting surface HL2d, and then is located at the center of the light receiving surface PDa. The light is incident, resulting in erroneous detection. In such a case, the Y direction component in the traveling direction of the stray light LST before and after reflection from the deflection surface HL2d is unchanged.

  In contrast, by tilting the deflecting surface HL2d at an inclination angle θ with respect to the Y direction as shown in FIG. 4, the stray light LST traveling along the plane of FIG. 3 travels after being reflected by the deflecting surface HL2d. In the direction, a Y-direction component (rightward component in FIG. 4) is given, and the light is incident rightwardly shifted with respect to the center of the light receiving surface PDa. Further, since the size of the light receiving surface PDa in the Y direction is smaller than the size in the Z direction, the possibility that the stray light LST is shifted to the right and incident on the non-detection region increases, thereby increasing the element holder HL2. It is possible to reduce the possibility of erroneous detection while reducing the size of the device. Incidentally, it is apparent that the deflection surface HL2d may be inclined in the opposite direction, and may be a curved surface as well as a flat surface.

  FIG. 8 is a view of the element holder HL2 ′ according to the modification in the optical axis direction, and FIG. 9 is a perspective view of the element holder HL2 ′ according to the modification. There is. In the present modification, as shown in FIG. 8, on the inner peripheral surface of the cylindrical portion HL2b, the surface on the side away from the semiconductor laser LD (the lower side in FIGS. 4 and 5) is the first deflection inclined to the opposite side. It is composed of a surface HL2e and a second deflecting surface HL2f, and has a mountain shape whose boundary is closest to the optical axis (FIG. 2) of the light receiving system RPS. The inclination angles θ of the first deflecting surface HL2e and the second deflecting surface HL2f with respect to the Y direction are preferably equal to each other in absolute value, and may be the same as or different from those in the above-described embodiment. According to this modification, when the stray light slightly deviated from the optical axis enters the lower opening CSb, the stray light deviated to the left from the optical axis as viewed in FIG. 8 enters the first deflection surface HL2e. 8, the stray light deviated to the right from the optical axis as viewed in FIG. 8 enters the second deflection surface HL2f and moves rightward with respect to the light receiving surface PDa. Therefore, the incidence on the light receiving surface PDa can be more effectively suppressed. Further, since the dimensions of the first deflection surface HL2e and the second deflection surface HL2f in the Z direction can be suppressed as compared with the above-described embodiment, the size of the element holder HL2 'can be reduced.

  FIG. 10 is a view of an element holder HL2 ″ according to another modification in the optical axis direction, and FIG. 11 is a perspective view of the element holder HL2 ″ according to another modification. It may differ from the actual case. In the present modified example, as shown in FIG. 10, on the inner peripheral surface of the cylindrical portion HL2b, the surface on the side away from the semiconductor laser LD (the lower side in FIGS. 4 and 5) is the first deflection inclined to the opposite side. It is composed of a surface HL2g and a second deflecting surface HL2h, and has a valley shape whose boundary is farthest from the optical axis (FIG. 2) of the light receiving system RPS. The inclination angles θ of the first deflecting surface HL2g and the second deflecting surface HL2h with respect to the Y direction are preferably equal to each other in absolute value, and may be the same as or different from those in the above-described embodiment. According to this modification, the size of the first deflecting surface HL2g and the second deflecting surface HL2h in the Z direction can be suppressed as compared with the above-described embodiment, so that the size of the element holder HL2 ″ can be reduced.

  FIG. 12 is a sectional view similar to FIG. 3 of a laser radar according to another embodiment. In the present embodiment, instead of the mirror unit, a single mirror MR having a mirror surface, which is rotatably arranged around the rotation axis RO, is provided. Other configurations are the same as those of the above-described embodiment.

  In FIG. 12, divergent light intermittently emitted in a pulse form from a semiconductor laser LD is converted into a parallel light flux by a collimating lens CL, and enters a point P1 on a rotating mirror MR as shown by a solid line. And is projected on the object OBJ side by scanning.

  On the other hand, among the light beams scanned and projected, the reflected light beam reflected on the object OBJ is incident on the point P4 of the mirror MR, as shown by the dashed line, reflected there, condensed by the lens LS, and condensed by the lens LS. The light passes through the inside of CSb and the inside of the cylindrical portion HL2b of the element holder HL2, and is detected on the light receiving surface PDa of the light receiving unit PD. In the present embodiment, an object within a range of 360 ° can be detected by rotating the mirror MR once. However, the mirror MR may be reciprocated at a certain angle. In any of the above embodiments, a similar deflecting surface may be provided on the inner peripheral surface of the lower opening CSb on the side remote from the semiconductor laser LD.

  The present invention is not limited to the embodiments described in the specification, and includes other embodiments and modifications, which will be apparent to those skilled in the art from the embodiments and ideas described in the present specification. It is. The description and examples of the specification are for the purpose of illustration only, and the scope of the present invention is indicated by the following claims. For example, all the contents of the present invention described with reference to the drawings can be applied to the embodiments. This laser radar can be applied not only to automobiles but also to flying objects, robots, surveillance cameras, and the like.

CL Collimating lens CS Case CSa Upper opening CSb Lower opening G Screen HL1 Projection optical system holder HL2, HL2 ', HL2 "element holder HL2a Flange HL2b Cylindrical part HL2c Opening HL2d First polarization plane HL2d Second deflection plane HL2e 1 deflecting surface HL2f 2nd deflecting surface HL2g 1st deflecting surface HL2h 2nd deflecting surface HL2p Hole LD Semiconductor laser Ln1 to Ln4 Area LPS Projection system LR Laser radar LS Lens LST Stray light M1 First mirror surface M2 Second mirror surface MR mirror MU Mirror unit OBJ Object PD Light receiving unit PDa Light receiving surface RO Rotation axis RPS Light receiving system ST Substrate

Claims (4)

Light source,
A light beam emitted from the light source, a light projecting optical system that converts the light beam into a collimated light beam and emits the light toward an object;
A mirror unit that reflects the collimated light beam from the light projection optical system toward the object, and includes a mirror surface that reflects the reflected light beam from the object, and rotates around a rotation axis ,
A light receiving optical system that receives the reflected light beam reflected by the mirror surface,
A light receiving unit that receives the reflected light flux condensed by the light receiving optical system,
A housing provided with a rectangular cylindrical opening that allows the reflected light to pass therethrough,
The optical axis of the light projecting optical system is orthogonal to the rotation axis, the optical axis of the light receiving optical system is orthogonal to the rotation axis,
By rotating the mirror, the collimated light beam is scanned with respect to the object, and at least the cross section of the collimated light beam when entering the object is in the scanning direction of the collimated light beam. The dimension is shorter than the dimension in the scanning orthogonal direction orthogonal to it,
The light receiving unit has a light receiving surface whose dimension in a second direction corresponding to the scanning orthogonal direction is larger than a dimension in a first direction corresponding to the scanning direction,
The housing has a deflecting surface on a surface of the inner peripheral surface of the opening farther from the light source, and an intersection between an optical axis of the light projecting optical system and the mirror surface and the light receiving optical system. The stray light generated from the mirror surface between the optical axis of the system and the intersection of the mirror surface enters the opening while being inclined with respect to the optical axis of the light receiving optical system , enters the deflection surface and is reflected. When the deflecting surface is inclined in the first direction, a component of the stray light traveling in the first direction in the traveling direction of the stray light is incident on the light receiving surface of the light receiving unit as compared with before the incidence. An object detection device that is to be increased later. The object detection device according to claim 1, wherein the deflection surface is inclined in one direction with respect to the first direction.   2. The object detecting device according to claim 1, wherein the deflection surface has two surfaces inclined in reverse to the first direction. The optical axis of the light projecting optical system and the optical axis of the light receiving optical system are spaced apart in the second direction, and the dimension of the light receiving surface of the light receiving section in the second direction The object detection device according to any one of claims 1 to 3, wherein H is the dimension in the first direction, W is the dimension in the first direction, and D is the internal dimension of the opening of the housing.
(2 × tan α × tan θ) / D> W (1)
However,
θ: inclination angle θ (°) of the deflection surface with respect to the first direction
α: diffusion angle of stray light generated from the mirror surface (°)

Images