Dichroic mirror for separating/synthesizing light with a plurality of wavelengths and optical apparatus and detecting method using the same

• US 5,600,487 A
• Filed: 04/12/1995
• Issued: 02/04/1997
• Est. Priority Date: 04/14/1994
• Status: Expired due to Term

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Hosokawa, Hayami, Kiyomoto, Hironobu, Ekawa, Kouichi
• Primary Examiner(s): Epps, Georgia Y.
• Assistant Examiner(s): MACK, RICKY LEVERN
• Application Number:
  US08/420,594
• Time in Patent Office: 664 Days
• Field of Search: 359/634, 359/583, 359/838, 359/586, 359/587, 359/589, 359/359
• US Class Current: 359/634
• CPC Class Codes: G02B 27/1006 for splitting or combining different wavelengths G02B27/1086, G02B27/141 take precedence
• CPC Class Codes: G02B 27/104 for use with scanning systems scanning systems G02B26/10
• CPC Class Codes: G02B 27/1086 operating by diffraction only
• CPC Class Codes: G02B 27/141 using dichroic mirrors
• CPC Class Codes: G02B 27/142 Coating structures, e.g. thin films multilayers
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• CPC Class Codes: G02B 5/0833 comprising inorganic materials only
• CPC Class Codes: G02B 5/22 Absorbing filters G02B5/201 - G02B5/208 take precedence
• CPC Class Codes: G02B 5/281 designed for the infrared light
• CPC Class Codes: G02B 6/29361 Interference filters, e.g. multilayer coatings, thin film filters, dichroic splitters or mirrors based on multilayers, WDM filters
• CPC Class Codes: G02B 6/4246 Bidirectionally operating package structures
• CPC Class Codes: H04J 14/0201 Add-and-drop multiplexing

Abstract

A dichroic mirror of the present invention having a first portion including an H material layer having a high refractive index, and an M material layer having an intermediate refractive index, the H material layer and the M material layer being laminated repeatedly; and a second portion including an H material layer having a high refractive index, and an L material layer having a low refractive index, the H material layer and the L material layer being laminated repeatedly. An optical apparatus and detecting method of the present invention use the above dichroic mirror.

Claims

1. An optical apparatus comprising:

first light-emitting means and second light-emitting means for respectively emitting a first light beam and a second light beam having mutually different wavelengths, at least one of said first and second light beams being at least one of a divergent light beam and a convergent light beam; and

a dichroic mirror comprising an optical multi-layered film for transmitting one of said first and second light beam therethrough and reflecting the other of said first and second light beams to synthesize said first and second light beams;

wherein a characteristic of said dichroic mirror satisfies at least one of the relations;

λ

D>

(λ

1+λ

2)/2,

λ

D>

√

(λ

1+λ

2), and

X=cos^-1 [(2cos a-1)cos θ

],

where wavelengths of said first and second light beams are λ

1 and λ

2, respectively;

a wavelength in which a transmittance at a central angle of said dichroic mirror disposed in at least one of divergent and convergent optical paths becomes 1/2 of a maximum transmittance thereof is λ

D;

an incident angle of at least one of said divergent and convergent light beams on said dichroic mirror is centered at θ and

spans a range of a on either side of center angle θ

; and

an angle in which a transmittance with respect to a wavelength of at least one of (λ

1+λ

2)/2 and √

(λ

1×

λ

2) becomes 1/2 of the maximum transmittance is x.

2. An optical apparatus according to claim 1, further comprising a light-receiving section for receiving said synthesized by said dichroic mirror.

3. An optical apparatus comprising:

first light-emitting means and second light-emitting means for respectively emitting a first light beam and a second light beam having mutually different wavelengths, at least one of said first and second light beams being at least one of a divergent light beam and a convergent light beam; and

a dichroic mirror comprising an optical multi-layered film for transmitting one of said first and second light beams therethrough and reflecting the other of said first and second light beams to synthesize said first and second light beams;

wherein said dichroic mirror comprises a first portion comprising a plurality of repeating subportions, each subportion including a layer of a first material having a first refractive index and a layer of a second material having a second refractive index lower than said first refractive index, and a second portion comprising a layer of the first material and a layer of a third material having a third refractive index lower than said second refractive index.

4. An optical apparatus according to claim 3, wherein said first material is comprised of TiO₂, said second material is comprised of Al₂ O₃, and said third material is comprised of SiO₂.

5. An optical apparatus according to claim 3, further comprising a light-receiving section for receiving said first and second light beams synthesized by said dichroic mirror.

6. An optical apparatus comprising:

a dichroic mirror comprising an optical multi-layered film, and disposed in an optical path of synthesized light coming from a substantially same direction in a state in which a first light beam and a second light beam having mutually different wavelengths are mixed, said dichroic mirror separating said first light beam and said second light beam as one of said light beams is transmitted therethrough and the other of said light beams is reflected thereby, at least one of said first and second light beams is at least one of a divergent light beam and a convergent light beam; and

first light-receiving means and second light-receiving means for receiving the separated first light beam and second light beam, respectively;

wherein a characteristic of said dichroic mirror satisfies at least one of the relations of;

λ

D>

(λ

1+λ

2)/2,

λ

D>

√

(λ

1+λ

2), and

X=cos^-1 [(2cos a-1) cos θ

],

where wavelengths of said first and second light beams are λ

1 and λ

2, respectively;

a wavelength in which a transmittance at a central angle of said dichroic mirror disposed in at least one of divergent and convergent optical paths becomes 1/2 of a maximum transmittance thereof is λ

D;

an incident angle of at least one of said divergent and convergent light beams on said dichroic mirror is centered at θ and

spans a range of a on either side of center angle θ

; and

an angle in which a transmittance with respect to a wavelength of at least one of (λ

1+λ

2)/2 and √

(λ

1×

λ

2) becomes 1/2 of the maximum transmittance thereof is X.

7. An optical sensor apparatus according to claim 6, further comprising a light-projecting section for projecting a light beam including said first light beam and the wavelength of the second light beam.

10. An optical sensor apparatus according to claim 6, further comprising a light-projecting section for projecting a light beam including said first light beam and the wavelength of the second light beam.

8. An optical apparatus comprising:

a dichroic mirror comprising an optical multi-layered film, and disposed in an optical path of synthesized light coming from a substantially same direction in a state in which a first light beam and a second light beam having mutually different wavelengths are mixed, said dichroic mirror separating said first light beam and said second light beam as one of said light beams is transmitted therethrough and the other of said light beam is reflected thereby, at least one of said first and second light beams is at least one of a divergent light beam and a convergent light beam; and

first light-receiving means and second light-receiving means for receiving the separated first light beam and second light beam, respectively;

wherein said dichroic mirror comprises a first portion comprising a plurality of repeating subportions, each subportion including a layer of a first material having a first refractive index and a layer of a second material having a second refractive index lower than said first refractive index and a second portion comprising a layer first material and a layer of a third material having a third refractive index lower than said second refractive index.

9. An optical apparatus according to claim 8, wherein said first material is comprised of TiO₂, said second material is comprised of Al₂ O₃, and said third material is comprised of SiO₂.

11. A dichroic mirror comprising:

a first portion comprising a plurality of repeating subportions, each subportion including a layer of a first material having a first refractive index, and a layer of a second material having a second refractive index lower than said first refractive index, and

a second portion including a layer of said first material and a layer of a third material having a refractive index lower than said second refractive index.

12. A dichroic mirror according to claim 11, wherein each of the layers in said first portion are provided with the same optical thickness.

13. A dichroic mirror according to claim 11, further comprising a third portion, said third portion comprising a plurality of subportions, each subportion including a layer of said first material and a layer of said third material wherein each of the layers of the third portion are provided with the same optical thickness.

14. A dichroic mirror according to claim 12, further comprising a third portion, said third portion comprising a plurality of subportions, each subportion including a layer of said first material and a layer of said third material wherein each of the layers of the third portion are provided with the same optical thickness.

15. A dichroic mirror according to claim 13, wherein said optical thickness of each of said layers of said third portion is thinner than an optical thickness of the layers said first portion.

16. A dichroic mirror according to claim 14, wherein said optical thickness of each of said layers of said third portion is thinner than an optical thickness of the layers of said first portion.

17. A dichroic mirror according to claim 11, wherein said first material is comprised of TiO₂, said second material is comprised of Al₂ O₃, and said third material is comprised of SiO₂.

18. A dichroic mirror according to claim 13, wherein said first material is comprised of TiO₂, said second material is comprised of Al₂ O₃, and said third material is comprised of SiO₂.

19. A dichroic mirror according to claim 14, wherein said first material is comprised of TiO₂, said second material is comprised of Al₂ O₃, and said third material is comprised of SiO₂.

20. A dichroic mirror for use with first and second light beams having wavelengths λ

1 and λ

2 respectively, each of said light beams having an optical path, said mirror comprising;

a first portion comprising a plurality of subportions, each subportion comprising a layer of a first material and a layer of a second material, said first and second materials having a first difference in a refractive index, each of said layers being provided with the same optical thickness; and

a second portion comprising a layer of a third material and a layer of a fourth material, said third and fourth materials having a second difference in a refractive index, said second difference being greater than said first difference;

such that, when said dichroic mirror is positioned in said optical paths and one of said light beams is incident said dichroic mirror at an angle centered at θ and

spans a range of a on either side of the center angle θ

, a characteristic of said dichroic mirror satisfies at least one of the relations of;

λ

D>

(λ

1+λ

2)/2,

λ

D>

√

(λ

1+λ

2), and

X-cos^-1 [(2cos a-1)cos θ

],

wherein a wavelength is which a transmittance at a central angle of said dichroic mirror disposed in optical paths becomes 1/2 of a maximum transmittance thereof is λ

D;

wherein an angle in which a transmittance with respect to a wavelength of at least one of (λ

1+λ

2)/2 and √

(λ

1×

λ

2) becomes 1/2 of the maximum transmittance is represented by X.

21. A dichroic mirror according to claim 20, wherein one of said first and second materials and one of said third and fourth materials are of a same material.

22. A dichroic mirror according to claim 20, further comprising a third portion comprising a plurality of subportions, each subportion comprising a layer of a fifth material and a layer of a sixth material, the fifth and sixth materials having the first difference in a refractive index, said layers of fifth and sixth materials being provided with the same optical thickness, respectively, which is different from an optical thickness of said layers of first and second materials in said first portion.

23. A dichroic mirror according to claim 20, further comprising a fourth portion comprising a layer of a seventh material and a layer of an eighth material, which have a third difference in a refractive index, said third difference being greater than said first difference.

24. A dichroic mirror according to claim 20, wherein said first and third material are comprised of TiO₂, said second material is comprised of Al₂ O₃. and said fourth material is comprised of SiO₂.

25. A method for detecting an object to be detected, comprising the steps of:

emitting a first light beam and a second light beam whose wavelengths are different from each other, at least one of said first and second light beams being at least one of a divergent light beam and a convergent light beam;

making said first and second light beams incident on different surfaces of a dichroic mirror, said dichroic mirror transmitting one of said first and second light beams therethrough and reflecting the other of said first and second light beams thereby to synthesize said first and second light beams;

projecting said synthesized first and second light beams toward the object to be detected;

receiving said first and second light beams reflected by the object to be detected; and

detecting the object to be detected on the basis of amounts of the first light beam and the second light beam received;

wherein said dichroic mirror comprising an optical multi-layered film, and a characteristic of said dichroic mirror satisfies at least one of the relations of;

λ

D>

(λ

1+λ

2)/2,

λ

D>

√

(λ

1×

λ

2), and

X=cos^-1 [(2cos a-1) cos θ

], respectively;

where wavelengths of said first and second light beams are λ

1 and λ

2, respectively.

a wavelength in which a transmittance at a central angle of said dichroic mirror disposed in at least one of divergent and convergent optical paths becomes 1/2 of a maximum transmittance thereof is

an incident angle of at least one of said divergent and convergent light beams on said dichroic mirror is centered at θ and

spans a range of a on either side of center angle θ

; and

an angle in which a transmittance with respect to a wavelength of at least one of (λ

1+λ

2)/2 and √

(λ

1×

λ

2) becomes 1/2 of the maximum transmittance is X.

26. A method for detecting an object to be detected, comprising the steps of:

projecting a first light beam and a second light beam whose wavelengths are different from each other toward the object to be detected;

making said first and second light beam, which are at least one of a divergent light beam and convergent light beams to be detected, incident on a surface of a dichroic mirror;

transmitting one of said first and second light beams through said dichroic mirror and reflecting the other of said first and second light beams by said dichroic mirror to separate said light beam reelected by the object to be detected into said first and second beams;

receiving said separated first and second beams, respectively; and

detecting the object to be detected on the basis amounts of the first light beam and the second light beam received;

wherein said dichroic mirror comprising an optical mult-layered film, and a characteristic of said dichroic mirror satisfy at least one of relations of;

λ

D>

(λ

1+λ

2)/2,

λ

D>

√

(λ

1×

λ

2), and

X-cos^-1 [(2cos a-1) cos θ

],

where wavelengths of said first and second light beams are λ

1 and λ

2, respectively;

a wavelength in which a transmittance at a central angle of said dichroic mirror disposed in at least one of divergent and convergent optical paths becomes 1/2 of a maximum transmittance thereof is λ

D;

an incident angle of at least one of said divergent and convergent light beams on said dichroic mirror is centered at θ and

spans a range of a on either side of center angle θ

; and

an angle in which a transmittance with respect to a wavelength of at least one of (λ

1+λ

2)/2 and 4(λ

1×

λ

2) becomes 1/2 of the maximum transmittance is X.

27. A method for detecting an object to be detected, comprising the steps of:

emitting a first light beam and a second light beam whose wavelength are different from each other, at least one of said first and second light beams being one of a divergent light beam and a convergent light beam;

making said first and second light beams incident on different surfaces of a dichroic mirror, said dichroic mirror transmitting one of said first and second light beams therethrough and reflecting the other of said first and second light beams thereby to synthesize said first and second beams;

projecting said synthesized first and second light beams toward the object to be detected;

receiving said first and second light beams reflected by the object to be detected; and

detecting the object to be detected on the basis of amounts of the first light beam and the second light beam received;

wherein said dichroic mirror comprises;

a first portion comprising a plurality of subportions;

each subportion including a layer of a first material having a first refractive index, and a layer of a second material having a second refractive index lower than said first refractive index, and

a second portion including a layer of said first material and a layer of a third material having a third refractive index lower than said second refractive index.

28. A method for detecting an object to be detected, comprising the steps of:

emitting a first light beam and a second light beam whose wavelength are different from each other, at least one of said first and second light beams being one of a divergent light beam and a convergent light beam;

making said first and second light beams incident on different surfaces of a dichroic mirror, said dichroic mirror transmitting one of said first and second light beams therethrough and reflecting the other of said first and second light beams thereby to synthesize said first and second beams;

projecting said synthesized first and second light beams toward the object to be detected;

receiving said first and second light beams reflected by the object to be detected; and

detecting the object to be detected on the basis of amounts of the first light beam and the second light beam received;

wherein said dichroic mirror comprises;

a first portion comprising a plurality of subportions, each subportion including a layer of a first material and a layer of a second material which have a first difference in a refractive index, each of said layers of said first and second materials being provided with the same optical thickness; and

a second portion comprising a layer of a third material and a layer of a fourth which have a second difference in a refractive index, said second difference being greater than said first difference.

29. A method for detecting an object to be detected, comprising the steps of:

projecting a first light beam and a second light beam whose wavelengths are different from each other toward the object to be detected;

making said first and second light beam, which are at least one of a divergent light beam and convergent light beams to be detected, incident on a surface of a dichroic mirror;

transmitting one of said first and second light beams through said dichroic mirror and reflecting the other of said first and second light beams by said dichroic mirror to separate said light beam reflected by the object to be detected into said first and second beams;

receiving said separated first and second beams, respectively; and

detecting the object to be detected on the basis of amounts of the first light beam and the second light beam received;

wherein said dichroic mirror comprises;

a first portion comprising a plurality of subportions, each subportion including a layer of a first material having a first refractive index, and a layer of a second material having a second refractive index; and

a second portion comprising a layer of a first material having a first refractive index and a layer of a third material having a third refractive index.

30. A method for detecting an object to be detected, comprising the steps of:

projecting a first light beam and a second light beam whose wavelengths are close to each other toward the object to be detected;

making said first and second light beam, which are at least one of a divergent light beam and convergent light beams incident on a surface of a dichroic mirror;

transmitting one of said first and second light beams through said dichroic mirror and reflecting the other of said first and second light beams by said dichroic mirror to separate said light beam reflected by the object to be detected into said first and second beams;

receiving said separated first and second beams, respectively; and

detecting the object to be detected on the basis of amounts of the first light beam and the second light beam received;

wherein said dichroic mirror comprises;

a first portion comprising a plurality of subportions, each subportion including a layer of a first material and a layer of a second material which have a first difference in a refractive index, each of said layers of said first and second materials being provided with the same optical thickness; and

a second portion comprising a layer of a third material and a layer of a fourth material which have a second difference in a refractive index, said second difference being greater than said first difference.