Imaging optical system

• US 6,950,240 B2
• Filed: 04/16/2004
• Issued: 09/27/2005
• Est. Priority Date: 07/14/1999
• Status: Expired due to Term

• Current Assignee: NEC Display Solutions, Ltd. (NEC Corporation)
• Original Assignee: NEC Viewtechnology, Ltd. (NEC Corporation)
• Inventors: Matsuo, Eiki
• Primary Examiner(s): Schwartz, Jordan M.
• Assistant Examiner(s): STULTZ, JESSICA T
• Application Number:
  US10/826,479
• Publication Number:
  US 20040196568A1
• Time in Patent Office: 529 Days
• Field of Search: 359648- 51, 359/362, 359754- 6, 359/763, 359/771, 359/784, 359/793, 353 69- 70, 353/98
• US Class Current: 359/649
• CPC Class Codes: G02B 13/16 for use in conjunction with image converters or intensifiers , or for use with projectors, e.g. objectives for projection TV
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence
• CPC Class Codes: G02B 17/08 Catadioptric systems used in non-imaging applications G02B19/00
• CPC Class Codes: G02B 17/0812 off-axis or unobscured systems in which all of the mirrors share a common axis of rotational symmetry
• CPC Class Codes: G02B 17/0828 off-axis or unobscured systems in which all of the mirrors share a common axis of rotational symmetry
• CPC Class Codes: G02B 17/0844 off-axis or unobscured systems in which all of the mirrors share a common axis of rotational symmetry
• CPC Class Codes: G02B 17/0848 off-axis or unobscured systems in which not all of the mirrors share a common axis of rotational symmetry, e.g. at least one of the mirrors is warped, tilted or decentered with respect to the other elements
• CPC Class Codes: G02B 17/0852 having a field corrector only
• CPC Class Codes: G03B 21/10 Projectors with built-in or built-on screen
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066

Abstract

A luminous flux, from one conjugate surface (A), having an opening angle of at least 10° sequentially passes through a first optical system (30) having a luminous flux convergent action in the vicinity of its reference axis and a second optical system (31) having a luminous flux divergent action in the vicinity of its reference axis, and converges on another conjugate surface (B). A specific condition is given to the converging distance of each converging point at a luminous flux section including a principal ray according to the passing position of the luminous flux through the first optical system (30) to thereby implement an oblique-incident optical system having a half angle of at least 60° and a comparatively simple structure irrespective of a type of an optical element used.

Claims

1. An image optical system in which a plurality of light beams emerging from an image-forming device on a conjugate plane A and having a divergence angle of 10°

or greater is made obliquely incident upon a conjugate plane B to form on the conjugate plane B an enlarged image approximately similar to an image formed by the image-forming device, said image optical system comprising;

a first optical system and a second optical system,

the first optical system including a plurality of refracting optical elements having a common optical axis and having the function of converging the plurality of light beams emerging from the image-forming device on both of a first light beam cross section parallel to principal rays and a second light beam cross section intersecting the first light beam cross section,

the second optical system including a reflecting optical element having a free-form surface and having the function of converging light beams passing through the first optical system on the conjugate plane B,

the first optical system having a first reference axis passing through a position nearer to a light beam traveling through the shortest optical path from the conjugate plane A to the conjugate plane B than to a light beam traveling through the longest optical path from the conjugate plane A to the conjugate plane B, the first reference axis being perpendicular to the conjugate plane A,

the second optical system having a second reference axis passing through a position nearer to a light beam traveling through the shortest optical path from the conjugate plane A to the conjugate plane B than to a light beam traveling through the longest optical path from the conjugate plane A to the conjugate plane B, the second reference axis being perpendicular to the conjugate plane B,

wherein if the distance from the point of emergence on the first optical system to the point of incidence on the second optical system along the first reference axis is S1 and the distance from the point of emergence on the second optical system to the conjugate plane B along the second reference axis is S2;

if the maximum and minimum of the distance between a point of convergence in the first and second light beam cross sections of a light beam emerging from the first optical system at a point nearest to the first reference axis and the point of emergence on the first optical system are L11 and L21, respectively;

if the maximum and minimum of the distance between the point of convergence in the first and second light beam cross sections of a light beam emerging from the first optical system at a point remotest from the first reference axis and the point of emergence on the first optical system are L1n and L2n,

conditions expressed by

S1≦

L11≦

S1+S2

S1≦

L21≦

S1+S2

L11/L1n<

0.25

0<

L21/L2n<

1.5

are satisfied.

2. An image optical system in which a plurality of light beams emerging from an image-forming device on a conjugate plane A and having a divergence angle of 10°

or greater is made obliquely incident upon a conjugate plane B to form on the conjugate plane B an enlarged image approximately similar to an image formed by the image-forming device, said image optical system comprising;

a first optical system and a second optical system,

the first optical system including a plurality of refracting optical elements having a common optical axis and having the function of converging the plurality of light beams emerging from the image-forming device on both of a first light beam cross section parallel to principal rays and a second light beam cross section intersecting the first light beam cross section,

the second optical system including a reflecting optical element having a free-form surface and having the function of converging light beams passing through the first optical system on the conjugate plane B,

the first optical system having a first reference axis passing through a position nearer to a light beam traveling through the shortest optical path from the conjugate plane A to the conjugate plane B than to a light beam traveling through the longest optical path from the conjugate plane A to the conjugate plane B, the first reference axis being perpendicular to the conjugate plane A,

the second optical system having a second reference axis passing through a position nearer to a light beam traveling through the shortest optical path from the conjugate plane A to the conjugate plane B than to a light beam traveling through the longest optical path from the conjugate plane A to the conjugate plane B, the second reference axis being perpendicular to the conjugate plane B,

wherein if the distance from the point of emergence on the first optical system to the point of incidence on the second optical system along the first reference axis is S1 and the distance from the point of emergence on the second optical system to the conjugate plane B along the second reference axis is S2;

if the maximum and minimum of the distance between a point of convergence in the first and second light beam cross sections of a light beam emerging from the first optical system at a point nearest to the first reference axis and the point of emergence on the first optical system are L11 and L21, respectively;

if the maximum and minimum of the distance between the point of convergence in the first and second light beam cross sections of a light beam emerging from the first optical system at a point remotest from the first reference axis and the point of emergence on the first optical system are L1n and L2n, respectively;

if the distance along an arbitrary light beam from the first optical system to the second optical system is D1 and the distance along the arbitrary light beam from the second optical system to the conjugate plane B is D2,

conditions expressed by

S1≦

L11≦

S1+S2

S1≦

L21≦

S1+S2

L11/L1n<

0.25

0<

L21/L2n<

1.5

D1<

D2

are satisfied.

3. An image optical system in which a plurality of light beams emerging from an image-forming device on a conjugate plane A and having a divergence angle of 10°

or greater is made obliquely incident upon a conjugate plane B to form on the conjugate plane B an enlarged image approximately similar to an image formed by the image-forming device, said image optical system comprising;

a first optical system and a second optical system,

the first optical system including a plurality of refracting optical elements having a common optical axis and having the function of converging the plurality of light beams emerging from the image-forming device on both of a first light beam cross section parallel to principal rays and a second light beam cross section intersecting the first light beam cross section,

the second optical system including a reflecting optical element having a free-form surface and having the function of converging light beams passing through the first optical system on the conjugate plane B,

the first optical system having a first reference axis passing through a position nearer to a light beam traveling through the shortest optical path from the conjugate plane A to the conjugate plane B than to a light beam traveling through the longest optical path from the conjugate plane A to the conjugate plane B, the first reference axis being perpendicular to the conjugate plane A,

the second optical system having a second reference axis passing through a position nearer to a light beam traveling through the shortest optical path from the conjugate plane A to the conjugate plane B than to a light beam traveling through the longest optical path from the conjugate plane A to the conjugate plane B, the second reference axis being perpendicular to the conjugate plane B,

wherein if the distance from the point of emergence on the first optical system to the point of incidence on the second optical system along the first reference axis is S1 and the distance from the point of emergence on the second optical system to the conjugate plane B along the second reference axis is S2;

if the maximum and minimum of the distance between a point of convergence in the first and second light beam cross sections of a light beam emerging from the first optical system at a point nearest to the first reference axis and the point of emergence on the first optical system are L11 and L21, respectively;

if the maximum and minimum of the distance between the point of convergence in the first and second light beam cross sections of a light beam emerging from the first optical system at a point remotest from the first reference axis and the point of emergence on the first optical system are L1n and L2n, respectively;

if the difference between the maximum and minimum of the ratio S1/L1 of the distance L1 and the distance S1 is Δ

SL,

conditions expressed by

S1≦

L11≦

S1+S2

S1≦

L21≦

S1+S2

L11/L1n<

0.25

0<

L21/L2n<

1.5

are satisfied and at least one of conditions expressed by

S1/L11>

0.6

 

(S1+S2)/L2n<

1

Δ

SL>

0.6

is further satisfied.

4. An image optical system in which a plurality of light beams emerging from an image-forming device on a conjugate plane A and having a divergence angle of 10°

or greater is made obliquely incident upon a conjugate plane B to form on the conjugate plane B an enlarged image approximately similar to an image formed by the image-forming device, said image optical system comprising;

a first optical system and a second optical system,

the first optical system including a plurality of refracting optical elements having a common optical axis and having the function of converging the plurality of light beams emerging from the image-forming device on both of a first light beam cross section parallel to principal rays and a second light beam cross section intersecting the first light beam cross section,

the second optical system including a reflecting optical element having a free-form surface and having the function of converging light beams passing through the first optical system on the conjugate plane B,

the first optical system having a first reference axis passing through a position nearer to a light beam traveling through the shortest optical path from the conjugate plane A to the conjugate plane B than to a light beam traveling through the longest optical path from the conjugate plane A to the conjugate plane B, the first reference axis being perpendicular to the conjugate plane A,

the second optical system having a second reference axis passing through a position nearer to a light beam traveling through the shortest optical path from the conjugate plane A to the conjugate plane B than to a light beam traveling through the longest optical path from the conjugate plane A to the conjugate plane B, the second reference axis being perpendicular to the conjugate plane B,

wherein if the distance from the point of emergence on the first optical system to the point of incidence on the second optical system along the first reference axis is Si and the distance from the point of emergence on the second optical system to the conjugate plane B along the second reference axis is S2;

if the maximum and minimum of the distance between a point of convergence in the first and second light beam cross sections of a light beam emerging from the first optical system at a point nearest to the first reference axis and the point of emergence on the first optical system are L11 and L21, respectively;

if the maximum and minimum of the distance between the point of convergence in the first and second light beam cross sections of a light beam emerging from the first optical system at a point remotest from the first reference axis and the point of emergence on the first optical system are L1n and L2n, respectively;

if the distance along an arbitrary light beam from the first optical system to the second optical system is D1 and the distance along the arbitrary light beam from the second optical system to the conjugate plane B is D2; and

if the difference between the maximum and minimum of the ratio S1/L1 of the distance L1 and the distance S1 is Δ

SL,

conditions expressed by

S1≦

L11≦

S1+S2

S1≦

L21≦

S1+S2

L11/L1n<

0.25

0<

L21/L2n<

1.5

D1<

D2

are satisfied and at least one of conditions expressed by

S1/L11>

0.6

(S1+S2)/L2n<

1

Δ

SL>

0.6

is further satisfied.