CN-122029470-A - Optical system and image pickup apparatus

Abstract

To provide an optical system which is compact and has high optical performance. The optical system reflects light from an object side by a first reflecting surface and further reflects the light by a second reflecting surface to guide the light to an image side. The optical system includes a diffractive surface or a supersurface having controlled wavelength dispersion characteristics. Order the Is the abbe number of the diffraction surface or the super surface, the following condition is satisfied: 。

Inventors

• TASHIRO YOSHIHISA

Assignees

• 佳能株式会社

Dates

Publication Date

20260512

Application Date

20240730

Priority Date

20231016

Claims (14)

1. 1. An optical system that reflects light from an object side by a first reflecting surface and further reflects the light by a second reflecting surface to guide the light to an image side, Wherein the optical system comprises a diffractive surface having controlled wavelength dispersion characteristics, Wherein the following equation is satisfied: , Wherein the method comprises the steps of Is the Abbe number of the diffraction surface, the reference wavelength is the d-line, the principal dispersion is the F-line and the C-line, 、 And (d) sum Is the optical path difference function at d-line, F-line, and C-line, and 、 And (d) sum Is the surface optical path difference dispersion at d-line, F-line, and C-line, the following condition is satisfied: 。
2. 2. The optical system of claim 1, wherein at least one of the first and second reflective surfaces comprises a concave mirror and has a positive optical power.
3. 3. The optical system according to claim 1 or 2, wherein the following condition is satisfied: , Where f is the focal length of the optical system and fm is the focal length of the diffraction surface.
4. 4. An optical system according to any one of claims 1 to 3, wherein the following condition is satisfied: , Where fm is the focal length of the diffraction surface and fr is the focal length of the reflection surface having the strongest optical power among the first and second reflection surfaces.
5. 5. The optical system according to any one of claims 1 to 4, wherein the diffraction surface is disposed closer to an object than the first reflection surface, and Wherein the following conditions are satisfied: , Where D1 is the optical effective diameter of the first reflective surface, f is the focal length of the optical system, and Fno is the full aperture ratio of the optical system.
6. 6. The optical system according to any one of claims 1 to 5, wherein the following condition is satisfied: , Where OAL is the total optical length of the optical system and f is the focal length of the optical system.
7. 7. The optical system of any one of claims 1 to 6, wherein the diffractive surface has positive optical power.
8. 8. The optical system according to any one of claims 1 to 7, wherein both of the first reflecting surface and the second reflecting surface are semi-transmissive reflecting surfaces, and Wherein the light from the object side is directed to the image side such that the light passes through the first reflective surface, is reflected by the second reflective surface, is reflected by the first reflective surface, and passes through the second reflective surface.
9. 9. The optical system according to any one of claims 1 to 7, wherein the first reflecting surface has a non-reflecting portion that allows the light to pass therethrough, and Wherein the light from the object side is directed to an image side such that the light is reflected by the first reflective surface, reflected by the second reflective surface, and passes through the non-reflective portion.
10. 10. The optical system according to any one of claims 1 to 9, wherein the optical system comprises at least one refractive lens.
11. 11. The optical system of claim 10, wherein the refractive lens comprises a positive lens and a negative lens.
12. 12. The optical system according to any one of claims 1 to 11, wherein the following condition is satisfied: , wherein among all refractive lenses included in the optical system, Is the optical power of the ith refractive lens counted from the object side, Is the d-line based abbe number of the ith refractive lens, Is of all refractive lenses And f is the focal length of the optical system.
13. 13. An optical system that reflects light from an object side by a first reflecting surface and further reflects the light by a second reflecting surface to guide the light to an image side, Wherein the optical system comprises a supersurface having controlled wavelength dispersion characteristics, Wherein the following condition is satisfied: , Wherein the method comprises the steps of Is the Abbe number of the super surface, the reference wavelength is d line, the main dispersion is F line and C line, 、 And (d) sum Is the optical path difference function at d-line, F-line, and C-line, and 、 And (d) sum Is the surface optical path difference dispersion at d-line, F-line, and C-line, the following condition is satisfied: 。
14. 14. An image pickup apparatus comprising: The optical system according to any one of claims 1 to 13, and An image sensor configured to capture an object through the optical system.

Description

Optical system and image pickup apparatus Technical Field The present invention relates to an optical system suitable for an image pickup apparatus such as a digital camera. Background An optical system for a compact image pickup apparatus is required to reduce the number of lenses in order to reduce the total optical length. Patent document 1 discloses an optical system that reduces the number of lenses using a planar lens having a diffraction surface, and reduces the size by folding an optical path using two reflection surfaces. Patent document 2 discloses an optical system in which two semi-transmissive reflective surfaces are used to fold an optical path to reduce an optical length. Prior art literature Patent literature Patent document 1 U.S. patent application publication No. 2022/01231016 Patent document 2 Japanese patent No. 6778823 Disclosure of Invention Problems to be solved by the invention In the case of using a normal diffraction surface having uncontrolled wavelength dispersion characteristics as in patent document 1, its abbe number is-3.45, which corresponds to extremely high dispersion. Considering chromatic aberration generated in such a case, it is difficult to provide a large optical power (reciprocal of focal length) to the diffraction surface, and thus there is a limit in further reduction of the number of lenses and further reduction of the optical length. In patent document 2, since the semi-transmissive reflective surface is configured as a planar surface for the purpose of reducing the back focal length of the lens, it is difficult to reduce the number of lenses of the optical system and achieve a higher specification. The present invention is to provide an optical system having a reduced size and high optical performance by reducing the number of lenses and the total optical length. Means for solving the problems An optical device according to an aspect of the present invention reflects light from an object side by a first reflecting surface and further reflects the light by a second reflecting surface to guide the light to an image side. The optical system includes a diffractive surface or a supersurface having controlled wavelength dispersion characteristics. Order theIs the abbe number of the diffraction surface or the super surface, the following condition is satisfied: 。 an image pickup apparatus having the above optical system also constitutes another aspect of the present invention. ADVANTAGEOUS EFFECTS OF INVENTION The present invention can provide an optical system having a reduced size and high optical performance by reducing the number and total optical length of lenses. Drawings Fig. 1 is a cross-sectional view of an optical system according to example 1. Fig. 2 is a longitudinal aberration diagram of an optical system according to example 1. Fig. 3 is a cross-sectional view of an optical system according to example 2. Fig. 4 is a longitudinal aberration diagram of an optical system according to example 2. Fig. 5 is a cross-sectional view of an optical system according to example 3. Fig. 6 is a longitudinal aberration diagram of an optical system according to example 3. Fig. 7 is a cross-sectional view of an optical system according to example 4. Fig. 8 is a longitudinal aberration diagram of an optical system according to example 4. Fig. 9 is a cross-sectional view of an optical system according to example 5. Fig. 10 is a longitudinal aberration diagram of an optical system according to example 5. Fig. 11 is a cross-sectional view of an optical system according to example 6. Fig. 12 is a longitudinal aberration diagram of an optical system according to example 6. Fig. 13 is a cross-sectional view of an optical system according to example 7. Fig. 14 is a longitudinal aberration diagram of an optical system according to example 7. Fig. 15 is a cross-sectional view of an optical system according to example 8. Fig. 16 is a longitudinal aberration diagram of an optical system according to example 8. Fig. 17 is a cross-sectional view of an optical system according to example 9. Fig. 18 is a spot diagram of an optical system according to example 9. Fig. 19 illustrates a configuration using polarization. Fig. 20 illustrates an image pickup apparatus including any one of the optical systems according to examples 1 to 9. Detailed Description Hereinafter, examples of the present invention will be described with reference to the drawings. Before describing examples 1 to 9, matters common to each example will be explained. Fig. 1, 3, 5, 7, 9, 11, 13, 15, and 17 illustrate configurations of optical systems according to examples 1 to 9, respectively. The optical system according to each example is used as an imaging optical system in image pickup apparatuses such as digital cameras and film-based cameras, and also in image pickup apparatuses mounted in smart phones, tablet computers, and the like. In each figure, the left side is the object side and the right side is the image side