US-12619055-B2 - Optical system, image projection apparatus, and imaging apparatus

US12619055B2US 12619055 B2US12619055 B2US 12619055B2US-12619055-B2

Abstract

The present disclosure is directed to an optical system internally having an intermediate imaging position that is conjugate to a magnification conjugate point on a magnification side and a reduction conjugate point on a reduction side, respectively, the optical system including: a magnification optical system having a plurality of lens elements, positioned on the magnification side with respect to the intermediate imaging position; and a relay optical system having a plurality of lens elements, positioned on the reduction side with respect to the intermediate imaging position, wherein a first lens element located closest to the magnification side among the plurality of lens elements in magnification optical system is an aspherical lens having a negative power, the optical system satisfies the conditions (1) to (3).

Inventors

Qinghua Zhao
Takuya Imaoka
Katsu Yamada

Assignees

PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20220519
Priority Date: 20200130

Claims (14)

1 . An optical system internally having an intermediate imaging position at which an intermediate image is formed, the intermediate imaging position being conjugate to a magnification conjugate point on a magnification side and a reduction conjugate point on a reduction side, respectively, the optical system comprising: a magnification optical system having a plurality of lens elements, positioned on the magnification side with respect to the intermediate imaging position; and a relay optical system having a plurality of lens elements, positioned on the reduction side with respect to the intermediate imaging position, wherein a first lens element located closest to the magnification side among the plurality of lens elements in the magnification optical system is an aspherical lens having a negative power, the optical system simultaneously satisfies the following conditions (1) to (3): wherein the plurality of lens elements include a lens element that satisfies both of the conditions (6) and (7) and one lens element that does not satisfy both of the conditions (6) and (7): 0.0055<Δ pgfn< 0.030 (1) 53< vdn< 58 (2) 0.28< fp/fr< 1.0 (3) | ym /( fw ·tan(ω m ))|<3.0 (6) Tg> 300° C. (7) where, Δpgfn=(ngn−nfn)/(nfn−ncn)−(−2.20599×10 −3 ·vdn+6.69612×10 −1 ), vdn is an Abbe number of the first lens element, ngn is a refractive index of the first lens element for a g-line, nfn is a refractive index of the first lens element for an F-line, non is a refractive index of the first lens element for a C-line, fp is a focal length of the magnification optical system, and fr is a focal length of the relay optical system at a wide-angle end, where, fw is a focal length of the entire optical system at the wide-angle end, om is a maximum half angle of view at the wide-angle end, ym is a height at the telephoto end at which the most off-axis main ray passes through a lens surface, and Tg is a glass transition point of lens material.
2 . The optical system according to claim 1 , wherein the first lens element has a first lens magnification side aspherical surface facing the magnification side and a first lens reduction side aspherical surface facing the reduction side, and the first lens magnification side aspherical surface and the first lens reduction side aspherical surface satisfies the following condition (8): dZ ( r )/ dr> 0 (8) where, r is a distance (r>0) from a vertex of a surface along a plane perpendicular to an optical axis of the optical system, and Z(r) is an amount of sag of the surface (in case that Z=0 at the vertex (r=0), where Z has a sign + for reduction side displacement with respect to the vertex, and a sign − for magnification side displacement).
3 . The optical system according to claim 1 , satisfying the following condition (9): 0.5<|( L 1 R 1+ L 1 R 2)/( L 1 R 2− L 1 R 1)|<5.0 (9) where, L1R1 is a center curvature radius of a first lens magnification side surface, and L1R2 is a center curvature radius of a first lens reduction side surface.
4 . The optical system according to claim 1 , wherein a second lens element is arranged on the reduction side of the first lens element, and the optical system satisfies the following condition (10): 1.2<| T 1/ fw|< 10.0 (10) where, T1 is an air distance between the first lens element and the second lens element, and fw is a focal length of the entire optical system at the wide-angle end.
5 . The optical system according to claim 1 , satisfying the following condition (11): 10.0<| f 1/ fw|< 16.0 (11) where, f1 is a focal length of the first lens element, and fw is a focal length of the entire optical system at the wide-angle end.
6 . The optical system according to claim 1 , satisfying the following condition (12): −8.0< f 1/ Y max<−1.0 (12) where, f1 is a focal length of the first lens element, and Ymax is a maximum image height.
7 . The optical system according to claim 1 , satisfying the following condition (13): 1.5<| f 1/ fp|< 10.0 (13) where, f1 is a focal length of the first lens element.
8 . The optical system according to claim 1 , satisfying the following condition (14): 1.0<| L 1 R 1/ L 1 R 2|<10.0 (14) where, L1R1 is a center curvature radius of the first lens magnification side surface, and L1R2 is a center curvature radius of the first lens reduction side surface.
9 . The optical system according to claim 1 , satisfying the following condition (15): 0.1 <TL 1/ Y max<5.0 (15) where, TL1 is a center thickness of the first lens element, and Ymax is a maximum image height.
10 . The optical system according to claim 1 , satisfying the following condition (16): 4< L 1 R 1/ Y max<10.5 (16) where, L1R1 is a center curvature radius of the first lens magnification side surface, and Ymax is a maximum image height.
11 . The optical system according to claim 1 , wherein during zooming the magnification optical system is fixed, and a part or all of the plurality of lens elements in the relay optical system is displaced along an optical axis.
12 . An image projection apparatus comprising: the optical system according to claim 1 ; and an image forming element that generates an image to be projected through the optical system onto a screen.
13 . An imaging apparatus comprising: the optical system according to claim 1 ; and an imaging element that receives an optical image formed by the optical system to convert the optical image into an electrical image signal.
14 . The optical system according to claim 1 , satisfying the following conditions (4) and (5): 7<| Ts/fw|< 15 (4) 2<| Tpr/fw|< 7 (5) where, Ts is the longest air distance along an optical axis in the magnification optical system, fw is the focal length of the entire optical system at the wide-angle end, and Tpr is a distance from a surface closest to the magnification side of the magnification optical system rear group to the intermediate imaging position.

Description

CROSS-REFERENCE OF RELATED APPLICATIONS This application is a continuation of International Patent Application No. PCT/JP2020/042917, filed on Nov. 18, 2020, which claims the benefit of Japanese Patent Application No. 2020-013668, filed on Jan. 30, 2020, the contents all of which are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to an optical system that forms an intermediate image. The present disclosure also relates to an image projection apparatus and an imaging apparatus using such an optical system. BACKGROUND Intermediate imaging-based optical systems have an advantage of achieving wide-angle projection with a short focal length and a wide screen, while the total length of the optical system tends to be increased, thereby rendering the optical system heavier. When attaching a portion of the optical system to an outside of a hosing of an image projection apparatus body, a moment acting on the center of gravity may cause the optical system to tilt relative to the apparatus body, thereby possibly degrading the optical performance. In order to reduce a weight of the optical system, it may be conceived that a lens made of a synthetic resin is used in lieu of a lens made of glass. Such a synthetic resin has a smaller specific gravity, a smaller thermal conductivity and a larger coefficient of linear expansion as compared to glass. Thus, the optical system can be lightweight. However if local temperature elevation and thermal deformation take place, some optical aberrations, in particular, chromatic aberration tends to be increased. This tendency is more remarkable in case of high-intensity projection. Patent Document 1 discloses a wide-angle imaging optical system, wherein the first lens L1a positioned closest to the magnification conjugate point has the largest diameter. The first lens L1a has aspherical double surfaces with quite complicated shapes, hence, it could be imagined to use a synthetic resin lens. However, such complicated aspherical shapes tend to be sensitive to thermal deformation. Therefore, it is expected that optical aberrations may be significantly degraded due to temperature elevation. PATENT DOCUMENT [Patent Document 1] JP 2019-174633 A SUMMARY The present disclosure provides an optical system that can reduce a moment acting on the center of gravity and mitigate thermal effect. The present disclosure also provides an image projection apparatus and an imaging apparatus using such an optical system. One aspect of the present disclosure is directed to an optical system internally having an intermediate imaging position that is conjugate to a magnification conjugate point on a magnification side and a reduction conjugate point on a reduction side, respectively, the optical system comprising: a magnification optical system having a plurality of lens elements, positioned on the magnification side with respect to the intermediate imaging position; anda relay optical system having a plurality of lens elements, positioned on the reduction side with respect to the intermediate imaging position,wherein a first lens element located closest to the magnification side among the plurality of lens elements in magnification optical system is an aspherical lens having a negative power,the optical system satisfies the following conditions (1) to (3): 0.0055<Δpgfn<0.030 (1) 53<vdn<58 (2) 0.28<fp/fr<1.0 (3) where, Δpgfn=(ngn−nfn)/(nfn−ncn)−(−2.20599×10−3·vdn+6.69612×10−1), vdn is an Abbe number of the first lens element, ngn is a refractive index of the first lens element for a g-line, nfn is a refractive index of the first lens element for an F-line, ncn is a refractive index of the first lens element for a C-line, fp is a focal length of the magnification optical system, and fr is a focal length of the relay optical system at a wide-angle end. Further, an image projection apparatus according to the present disclosure includes the above-described optical system and an image forming element that generates an image to be projected through the optical system onto a screen. Still further, an imaging apparatus according to the present disclosure includes the above-described optical system and an imaging element that receives an optical image formed by the optical system to convert the optical image into an electrical image signal. The optical system according to the present disclosure can reduce a moment acting on the center of gravity and mitigate thermal effect. Therefore, even in case of intense light passing through the lens elements, such as, high-intensity projection, the optical performance can be maintained. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a layout diagram showing an optical path at a wide-angle end in a zoom lens system of example 1 for an object distance of 1066 mm. FIGS. 2A-2C are layout diagrams of the zoom lens system of example 1 for an object distance of 1066 mm. FIGS. 3A-3C are longitudinal aberrations diagram of the zoom lens system of example