Optical system having refracting surface and reflecting surface, and image capturing apparatus and projection apparatus including the same

Patent metadata

Field	Value
Publication number	US-10895724-B2
Application number	US-201816042990-A
Country	US
Kind code	B2
Filing date	Jul 23, 2018
Priority date	Jul 26, 2017
Publication date	Jan 19, 2021
Grant date	Jan 19, 2021

Abstract

An optical system includes a first optical element including a first reflecting region having a convex shape toward an enlargement side, a second optical element having a reduction-side surface having a convex shape toward the enlargement side, and a third optical element having an enlargement-side surface having a convex shape toward the enlargement side, wherein the reduction-side surface of the second optical element or the enlargement-side surface of the third optical element includes a second reflecting region, wherein the third optical element includes a refracting region having positive power, and wherein light from the enlargement side proceeds to a reduction side sequentially through a refracting region of the first optical element, the second reflecting region, the first reflecting region, a refracting region of the second optical element, and the refracting region of the third optical element.

First claim

What is claimed is:

1. An optical system comprising:
a first optical element including a first reflecting region having a convex shape toward an enlargement side;
a second optical element having a reduction-side surface having a convex shape toward the enlargement side; and
a third optical element having an enlargement-side surface having a convex shape toward the enlargement side,
wherein the reduction-side surface of the second optical element or the enlargement-side surface of the third optical element includes a second reflecting region,
wherein the third optical element includes a refracting region having positive power,
wherein light enters the enlargement side by entering the first optical element from the side of the first optical element furthest from the second optical element with respect to the first optical element proceeds to a reduction side sequentially via a refracting region of the first optical element, the second reflecting region, the first reflecting region, a refracting region of the second optical element, and the refracting region of the third optical element, and
wherein the following conditional expression is satisfied:
2.0≤ R 1/ L 1≤5.5

where a radius of curvature of a closest refracting surface, that is closest to the first optical element among refracting surfaces located on the reduction side of the first optical element, is R1, and a distance between the closest refracting surface and an optical surface including the second reflecting region is L1.

2. The optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.3≤ Lg/Lm≤ 0.95

where a total thickness of optical elements present between the first reflecting region and the second reflecting region is Lg, and a distance between an optical surface including the first reflecting region and an optical surface including the second reflecting region is Lm.

3. The optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.7≤ Rp/Rn≤ 1.3

where a radius of curvature of an optical surface including the first reflecting region is Rp, and a radius of curvature of an optical surface including the second reflecting region is Rn.

4. The optical system according to claim 1 , wherein a refractive index of a medium between the first optical element and the second optical element is smaller than a refractive index of the second optical element.

5. The optical system according to claim 1 , wherein the second reflecting region includes a reflecting portion configured to reflect a part of the light, and a light-blocking portion configured to block a part of the light.

6. The optical system according to claim 5 , wherein a diameter of the reflecting portion in a first direction perpendicular to an optical axis is larger than a diameter of the reflecting portion in a second direction perpendicular to the optical axis and the first direction, and the first reflecting region is located on one side with respect to the optical axis in the second direction.

7. The optical system according to claim 1 , wherein the first reflecting region is included in a reduction-side surface of the first optical element.

8. The optical system according to claim 1 , wherein the first optical element includes a refracting region having positive power.

9. The optical system according to claim 8 , wherein the first optical element is a positive meniscus lens.

10. The optical system according to claim 1 , wherein the second reflecting region is included in the reduction-side surface of the second optical element.

11. The optical system according to claim 1 , wherein the second optical element includes a refracting region having negative power.

12. The optical system according to claim 1 , wherein an enlargement-side surface of the second optical element has a convex shape toward the enlargement side.

13. The optical system according to claim 1 , wherein a reduction-side surface of the third optical element has a concave shape toward the enlargement side.

14. An image capturing apparatus comprising:
an image sensor configured to capture a physical body; and
the optical system according to claim 1 configured to form an image of the physical body on an imaging surface of the image sensor.

15. A distance measuring apparatus comprising:
the image capturing apparatus according to claim 14 configured to acquire image data of a physical body; and
a distance calculation unit configured to acquire distance information regarding a distance from the physical body, based on the image data.

16. An in-vehicle camera system comprising:
the distance measuring apparatus according to claim 15 ; and
a collision determination unit configured to determine whether there is a possibility of collision between a motor vehicle and the physical body, based on the distance information.

17. The in-vehicle camera system according to claim 16 , further comprising a control device configured to, in a case where it is determined that there is a possibility of collision between the motor vehicle and the physical body, output a control signal for producing a braking force in each wheel of the motor vehicle.

18. The in-vehicle camera system according to claim 16 , further comprising an alarm device configured to, in a case where it is determined that there is a possibility of collision between the motor vehicle and the physical body, give an alarm to a driver of the motor vehicle.

19. A projection apparatus comprising:
a display element configured to display an image; and
the optical system according to claim 1 configured to form an image on a display surface of the display element.

20. An optical system comprising:
a first optical element including a first reflecting region having a convex shape toward an enlargement side;
a second optical element having a reduction-side surface having a convex shape toward the enlargement side; and
a third optical element having an enlargement-side surface having a convex shape toward the enlargement side,
wherein the reduction-side surface of the second optical element or the enlargement-side surface of the third optical element includes a second reflecting region,
wherein the third optical element includes a refracting region having positive power,
wherein light from the enlargement side proceeds to a reduction side sequentially via a refracting region of the first optical element, the second reflecting region, the first reflecting region, a refracting region of the second optical element, and the refracting region of the third optical element, and
wherein the following conditional expression is satisfied:
2.0≤ R 1/ L 1≤5.5

where a radius of curvature of a closest refracting surface, that is closest to the first optical element among refracting surfaces located on the reduction side of the first optical element, is R1, and a distance between the closest refracting surface and an optical surface including the second reflecting region is L1.

21. An optical system comprising:
a first optical element including a first reflecting region having a convex shape toward an enlargement side;
a second optical element having a reduction-side surface having a convex shape toward the enlargement side; and
a third optical element having an enlargement-side surface having a convex shape toward the enlargement side
wherein the reduction-side surface of the second optical element or the enlargement-side surface of the third optical element inc

Assignees

• Canon Kk

Inventors

• Kajiyama Kazuhiko
• Maezawa Koji

Classifications

• G02B17/0812 Primary

  off-axis or unobscured systems in which all of the mirrors share a common axis of rotational symmetry · CPC title

• G02B17/0836

  using more than three curved mirrors (G02B17/0864, G02B17/0896 take precedence) · CPC title

• G02B17/08 Primary

  Catadioptric systems {(used in non-imaging applications G02B19/00)} · CPC title

• G02B17/0896

  with variable magnification or multiple imaging planes, including multispectral systems (systems with only refractive elements G02B15/14) · CPC title

• G02B17/0804 Primary

  using two curved mirrors (G02B17/0864, G02B17/0896 takes precedence) · CPC title