Scanning optical system and radar

1. A scanning optical system, comprising:

a rotatable mirror unit including a first mirror surface inclining relative to a rotation axis and a second mirror surface; and

a light projecting system including at least one light source which emits a light flux toward an object through the mirror unit;

the mirror unit including multiple mirror pairs comprising the first mirror surfaces and the second mirror surfaces,

wherein the respective intersection angles of the multiple mirror pairs are different from each other,

wherein a light flux emitted from the light source is reflected on the first mirror surface of the mirror unit, then, proceeds to the second mirror surface, further is reflected on the second mirror surface, and is projected so as to scan on the object correspondingly to rotation of the mirror unit,

wherein the light flux emitted from the light projecting system is made longer in a sub scanning angle direction than in a scanning angle direction in a measurement range of the object, and

wherein at least one mirror pair of the mirror unit satisfies the following conditional expression,

|θ1−90|×|α|≤225  (1)

wherein, in the expression, θ1 is an intersection angle (°) other than 90° between the first mirror surface and the second mirror surface, and α is a rotation angle (°).

2. The scanning optical system described in claim 1 , wherein the mirror unit includes mirror pairs in which the intersection angle (°) is 90°.

3. The scanning optical system described in claim 1 , further comprising:

a deflecting element which changes a proceeding direction of a light flux emitted from the light projecting system and is disposed between the light source and the mirror unit.

4. The scanning optical system described in claim 1 , further comprising a deflecting element to change a proceeding direction of a light flux emitted from the light projecting system disposed between the light source and the mirror unit, and an angle of a sub scanning angle in an intersection angle between the first mirror surface and the second mirror surface is made to continue.

5. The scanning optical system described in claim 1 , wherein the mirror unit is made of a resin.

6. The scanning optical system described in claim 1 , wherein in the case where an intersection angle between the first mirror surface and the second mirror surface in the mirror unit is other than 90 degrees, the following conditional expression is satisfied,

β≤30  (2)

wherein, in the conditional expression, β is an angle (°: referred to as an incident angle) of a light flux entering the first mirror surface relative to a plane orthogonal to the rotation axis.

7. The scanning optical system described in claim 1 , wherein the light projecting system comprises multiple light projecting systems, and wherein respective light fluxes emitted from the multiple light projecting systems have respective different angles relative to a plane orthogonal to the rotation axis when entering the first mirror surface.

8. The scanning optical system described in claim 1 , further comprising:

a light receiving system to receive reflected light rays of a light flux projected so as to scan on the object via the mirror unit.

9. The scanning optical system described in claim 8 , wherein the reflected light rays from the object are reflected on the second mirror surface, further reflected on the first mirror surface, and then received by the light receiving system.

10. The scanning optical system described in claim 8 , wherein the light receiving system includes a light receiving sensor constituted by multiple light receiving elements so as to at least divide a view field in a long side direction of a light flux emitted from the light projecting system.

11. The scanning optical system described in claim 1 , wherein

a light emitting timing of the light source at the time of projecting a light flux onto a mirror pair in which an intersection angle is farther from 90° is made slower than a light emitting timing of the light source at the time of projecting a light flux onto a mirror pair in which an intersection angle is closer to 90°.

12. A laser radar, comprising:

a scanning optical system comprising:

a rotatable mirror unit including a first mirror surface inclining relative to a rotation axis and a second mirror surface; and

a light projecting system including at least one light source which emits a light flux toward an object through the mirror unit;

the mirror unit including multiple mirror pairs comprising the first mirror surfaces and the second mirror surfaces,

wherein the respective intersection angles of the multiple mirror pairs are different from each other,

wherein a light flux emitted from the light source is reflected on the first mirror surface of the mirror unit, then, proceeds to the second mirror surface, further is reflected on the second mirror surface, and is projected so as to scan on the object correspondingly to rotation of the mirror unit,

wherein the light flux emitted from the light projecting system is made longer in a sub scanning angle direction than in a scanning angle direction in a measurement range of the object, and

wherein the mirror unit includes at least one mirror pair satisfying the following conditional expression,

|θ1−90|×|α|≤225  (1)

wherein, in the expression, θ1 is an intersection angle (°) other than 90° between the first mirror surface and the second mirror surface, and α is a rotation angle (°).