Dichroic mirror and projector having the same

Claim 2

A dichroic mirror for reflecting a beam of a given color, comprising: a substrate; and a multilayered film formed on said substrate, said multilayered film being constituted by a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the beam incident side, said first dichroic reflecting layer having a smaller reflection range of one of two orthogonal polarized components of the beam than the other of the two orthogonal polarized components, said intermediate layer rotating a polarization plane of at least part of a beam of the one component of the beam passing through said first dichroic reflecting layer, and said second dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said intermediate layer.

Claim 3

A mirror according to claim 1, wherein said second dichroic reflecting layer has characteristics of at least one end of a long- and short-wavelength sides of the reflection range for the other component of the beam similar to those of the reflection range of the other component in said first dichroic reflecting layer.

Claim 4

A mirror according to claim 1, wherein said substrate comprises parallel plates.

Claim 5

A mirror according to claim 1, wherein said substrate comprises a prism.

Claim 6

A mirror according to claim 1, wherein said intermediate layer comprises a halfwave plate for rotating the polarization plane of the at least part of the beam through 90` .

Claim 7

A mirror according to claim 1, wherein said intermediate layer comprises a first halfwave plate for rotating the polarization plane of the at least part of the beam through 90°; and said mirror further comprises a second halfwave plate formed on a side opposite to said intermediate layer through said second dichroic reflecting layer, said first halfwave plate having a high-index axis having substantially the same direction as that of a low-index axis of said second halfwave plate.

Claim 8

A mirror according to claim 1, wherein an air layer is formed between said first dichroic reflecting layer and said intermediate layer.

Claim 9

A mirror according to claim 1, wherein an air layer is formed between said intermediate layer and said second dichroic reflecting layer.

Claim 10

A dichroic mirror for reflecting a red beam, comprising: a substrate; and a multilayered film formed on said substrate, said multilayered film being constituted by a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of the red beam, said first dichroic reflecting layer having a smaller reflection range of a P-polarized component of the beam than that of an S-polarized component thereof, said intermediate layer rotating, through substantially 90` , at least part of a beam of the P-polarized component of the beam passing through said first dichroic reflecting layer, said second dichroic reflecting layer having short-wavelength characteristics of the reflection range of the S-polarized component of the red beam to be almost equal to short-wavelength characteristics of the reflection range of the S-polarized component in said first dichroic reflecting layer, and said second dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said intermediate layer.

Claim 11

A dichroic mirror for reflecting a red beam, comprising: a substrate; and a multilayered film formed on said substrate, said multilayered film being constituted by a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of the red beam, said first dichroic reflecting layer having a smaller reflection range of a P-polarized component of the beam than that of an S-polarized component thereof, said intermediate layer rotating, through substantially 90` , at least part of a beam of the P-polarized component of the beam passing through said first dichroic reflecting layer, said second dichroic reflecting layer having short-wavelength characteristics of the reflection range of the S-polarized component of the red beam to be almost equal to short-wavelength characteristics of the reflection range of the S-polarized component in said first dichroic reflecting layer, and said second dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said intermediate layer.

Claim 12

A mirror according to claim 9, wherein said intermediate layer comprises a first X/2 (where λ is a wavelength of the at least part of the beam) plate; and said mirror further comprises a second X/2 plate formed at a side opposite to said intermediate layer through said second dichroic reflecting layer, said first X/2 plate having a high-index axis having a direction substantially the same as that of a low-index axis of said second X/2 plate.

Claim 13

A mirror according to claim 9, wherein said substrate comprises parallel plates.

Claim 14

A mirror according to claim 11, wherein said parallel plates comprise a pair of plates which sandwich said multilayered film.

Claim 15

A mirror according to claim 9, wherein said substrate comprises a pair of prisms which sandwich said multilayered film.

Claim 16

A dichroic mirror for reflecting a blue beam, comprising: a substrate; and a multilayered film formed on said substrate, said multilayered film being constituted by a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of the blue beam, said first dichroic reflecting layer having a smaller reflection range of a P-polarized component of the beam than that of an S-polarized component thereof, said intermediate layer rotating, through substantially 90°, at least part of a beam of the P-polarized component of the beam passing through said first dichroic reflecting layer, said second dichroic reflecting layer having long-wavelength characteristics of the reflection range of the S-polarized component of the blue beam to be almost equal to long-wavelength characteristics of the reflection range of the S-polarized component in said first dichroic reflecting layer, and said second dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said intermediate layer.

Claim 17

A dichroic mirror for reflecting a blue beam, comprising: a substrate; and a multilayered film formed on said substrate, said multilayered film being constituted by a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of the blue beam, said first dichroic reflecting layer having a smaller reflection range of a P-polarized component of the beam than that of an S-polarized component thereof, said intermediate layer rotating, through substantially 90°, at least part of a beam of the P-polarized component of the beam passing through said first dichroic reflecting layer, said second dichroic reflecting layer having long-wavelength characteristics of the reflection range of the S-polarized component of the blue beam to be almost equal to long-wavelength characteristics of the reflection range of the S-polarized component in said first dichroic reflecting layer, and said second dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said intermediate layer.

Claim 18

A mirror according to claim 14, wherein said intermediate layer comprises a first X/2 (where λ is a wavelength of the at least part of the beam) plate; and said mirror further comprises a second X/2 plate formed at a side opposite to said intermediate layer through said second dichroic reflecting layer, said first X/2 plate having a high-index axis having a direction substantially the same as that of a low-index axis of said second X/2 plate.

Claim 19

A mirror according to claim 14, wherein said substrate comprises parallel plates.

Claim 20

A mirror according to claim 16, wherein said parallel plates comprise a pair of plates which sandwich said multilayered film.

Claim 21

A mirror according to claim 14, wherein said substrate comprises a pair of prisms which sandwich said multilayered film.

Claim 22

A dichroic mirror for reflecting a green beam, comprising: a substrate; and a multilayered film formed on said substrate, said multilayered film being constituted by a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of the green beam, said first dichroic reflecting layer having a smaller reflection range of a P-polarized component of the beam than that of an S-polarized component thereof, said intermediate layer rotating, through substantially 90°, at least part of a beam of the P-polarized component of the beam passing through said first dichroic reflecting layer, said second dichroic reflecting layer having long- and short-wavelength characteristics of the reflection range of the S-polarized component of the green beam to be almost equal to long- and short-wavelength characteristics of the reflection range of the S-polarized component in said first dichroic reflecting layer, and said second dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said intermediate layer.

Claim 23

A dichroic mirror for reflecting a green beam, comprising: a substrate; and a multilayered film formed on said substrate, said multilayered film being constituted by a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of the green beam, said first dichroic reflecting layer having a smaller reflection range of a P-polarized component of the beam than that of an S-polarized component thereof, said intermediate layer rotating, through substantially 90°, at least part of a beam of the P-polarized component of the beam passing through said first dichroic reflecting layer, said second dichroic reflecting layer having long- and short-wavelength characteristics of the reflection range of the S-polarized component of the green beam to be almost equal to long- and short-wavelength characteristics of the reflection range of the S-polarized component in said first dichroic reflecting layer, and said second dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said intermediate layer.

Claim 24

A mirror according to claim 19, wherein said intermediate layer comprises a first X/2 (where λ is a wavelength of the at least part of the beam) plate; and said mirror further comprises a second X/2 plate formed at a side opposite to said intermediate layer through said second dichroic reflecting layer, said first X/2 plate having a high-index axis having a direction substantially the same as that of a low-index axis of said second X/2 plate.

Claim 25

A mirror according to claim 19, wherein said substrate comprises parallel plates.

Claim 26

A mirror according to claim 21, wherein said parallel plates comprise a pair of plates which sandwich said multilayered film.

Claim 27

A mirror according to claim 19, wherein said substrate comprises a pair of prisms which sandwich said multilayered film.

Claim 28

An optical apparatus having a color separation system, said color separation system receiving first and second beams having different colors, said system comprising a dichroic mirror for reflecting the first beam and transmitting the second beam to separate the first beam from the second beam, said mirror having a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of each of the first and second beams, said first dichroic reflecting layer having a smaller reflection range of one of two orthogonal polarized components of the first beam than that of the other of the two orthogonal polarized components, said intermediate layer rotating a polarization plane of at least part of a remaining beam of the one component of the first beam passing through said first dichroic reflecting layer, and said second dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said intermediate layer.

Claim 29

An optical apparatus having a color separation system, said color separation system receiving first and second beams having different colors, said system comprising a dichroic mirror for reflecting the first beam and transmitting the second beam to separate the first beam from the second beam, said mirror having a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of each of the first and second beams, said first dichroic reflecting layer having a smaller reflection range of one of two orthogonal polarized components of the first beam than that of the other of the two orthogonal polarized components, said intermediate layer rotating a polarization plane of at least part of a remaining beam of the one component of the first beam passing through said first dichroic reflecting layer, and said second dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said intermediate layer.

Claim 30

An apparatus according to claim 24, wherein said second dichroic reflecting layer has characteristics of at least one end of a long- and short-wavelength sides of the reflection range for the other component of the beam similar to those of the reflection range of the other component in said first dichroic reflecting layer.

Claim 31

An apparatus according to claim 24, wherein said intermediate layer comprises a halfwave plate for rotating the polarization plane of the at least part of the beam through 90` .

Claim 32

An apparatus according to claim 24, wherein said intermediate layer comprises a first halfwave plate for rotating the polarization plane of the at least part of the beam through 90°; and said mirror further comprises a second halfwave plate formed on a side opposite to said intermediate layer through said second dichroic reflecting layer, said first halfwave plate having a high-index axis having a direction substantially the same as that of a low-index axis of said second halfwave plate.

Claim 33

An optical apparatus having a color synthesis system, said color synthesis system receiving first and second beams having different colors, said system comprising a dichroic mirror for reflecting the first beam and transmitting the second beam to separate the first beam from the second beam, said mirror having a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of each of the first and second beams, said first dichroic reflecting layer having a smaller reflection range of one of two orthogonal polarized components of the first beam than that of the other of the two orthogonal polarized components, said intermediate layer rotating a polarization plane of at least part of a remaining beam of the one component of the first beam passing through said first dichroic reflecting layer, and said second dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said intermediate layer.

Claim 34

An optical apparatus having a color synthesis system, said color synthesis system receiving first and second beams having different colors, said system comprising a dichroic mirror for reflecting the first beam and transmitting the second beam to separate the first beam from the second beam, said mirror having a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of each of the first and second beams, said first dichroic reflecting layer having a smaller reflection range of one of two orthogonal polarized components of the first beam than that of the other of the two orthogonal polarized components, said intermediate layer rotating a polarization plane of at least part of a remaining beam of the one component of the first beam passing through said first dichroic reflecting layer, and said second dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said intermediate layer.

Claim 35

An apparatus according to claim 28, wherein said intermediate layer comprises a halfwave plate for rotating the polarization plane of the at least part of the beam through 90` .

Claim 36

An apparatus according to claim 28, wherein said intermediate layer comprises a first halfwave plate for rotating the polarization plane of the at least part of the beam through 90°; and said mirror further comprises a second halfwave plate formed on a side opposite to said intermediate layer through said second dichroic reflecting layer, said first halfwave plate having a high-index axis having a direction substantially the same as that of a low-index axis of said second halfwave plate.

Claim 37

A projector comprising: radiation beam supply means for supplying a radiation beam including first and second beams having different colors; a color separation system for separating the radiation beam into the first and second beams, said color separation system having a dichroic mirror, said mirror having a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of each beam to reflect the first beam and transmit the second beam so as to separate the first beam from the second beam, said first dichroic reflecting layer having a smaller reflection range of one of two orthogonal polarized components of the first beam than that of the other of the two orthogonal polarized components, said intermediate layer rotating a polarization plane of at least part of a remaining beam of the one component of the first beam passing through said first dichroic reflecting layer, and said second dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said intermediate layer; means for modulating the first beam from said color separation system and generating a first image; means for modulating the second beam from said color separation system and generating a second image; and means for projecting the first and second images.

Claim 38

A projector comprising: radiation beam supply means for supplying a radiation beam including first and second beams having different colors; a color separation system for separating the radiation beam into the first and second beams, said color separation system having a dichroic mirror, said mirror having a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of each beam to reflect the first beam and transmit the second beam so as to separate the first beam from the second beam, said first dichroic reflecting layer having a smaller reflection range of one of two orthogonal polarized components of the first beam than that of the other of the two orthogonal polarized components, said intermediate layer rotating a polarization plane of at least part of a remaining beam of the one component of the first beam passing through said first dichroic reflecting layer, and said second dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said intermediate layer; means for modulating the first beam from said color separation system and generating a first image; means for modulating the second beam from said color separation system and generating a second image; and means for projecting the first and second images.

Claim 39

A projector according to claim 31, wherein said intermediate layer comprises a halfwave plate for rotating the polarization plane of the at least part of the beam through 90` .

Claim 40

A projector according to claim 31, wherein said intermediate layer comprises a first halfwave plate for rotating the polarization plane of the at least part of the beam through 90°; and said mirror further comprises a second halfwave plate formed on a side opposite to said intermediate layer through said second dichroic reflecting layer, said first halfwave plate having a high-index axis having a direction substantially the same as that of a low-index axis of said second halfwave plate.

Claim 41

A projector comprising: supply means for supplying first and second beams having different colors; first beam generating means for modulating the first beam from said supply means and generating a beam representing a first image; second beam generating means for modulating the second beam from said supply means and generating a beam representing the second image; a color synthesis system for synthesizing the beams representing the first and second images, said system having a dichroic mirror, and said mirror having a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of the first beam to reflect the beam representing the first image and transmit the beam representing the second image to synthesize the beam representing the first image with the beam representing the second image, said first dichroic reflecting layer having a smaller reflection range of one of two orthogonal polarized components of the first beam than that of the other of the two orthogonal polarized components, said intermediate layer rotating a polarization plane of at least part of a remaining beam of the one component of the first beam passing through said first dichroic reflecting layer, and said second dichroic reflecting layer reflects the at least part of the beam whose polarization plane is rotated by said intermediate layer; and means for projecting the first and second images by using the beams representing the first and second images from said color synthesis system.

Claim 42

A projector comprising: supply means for supplying first and second beams having different colors; first beam generating means for modulating the first beam from said supply means and generating a beam representing a first image; second beam generating means for modulating the second beam from said supply means and generating a beam representing the second image; a color synthesis system for synthesizing the beams representing the first and second images, said system having a dichroic mirror, and said mirror having a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of the first beam to reflect the beam representing the first image and transmit the beam representing the second image to synthesize the beam representing the first image with the beam representing the second image, said first dichroic reflecting layer having a smaller reflection range of one of two orthogonal polarized components of the first beam than that of the other of the two orthogonal polarized components, said intermediate layer rotating a polarization plane of at least part of a remaining beam of the one component of the first beam passing through said first dichroic reflecting layer, and said second dichroic reflecting layer reflects the at least part of the beam whose polarization plane is rotated by said intermediate layer; and means for projecting the first and second images by using the beams representing the first and second images from said color synthesis system.

Claim 43

A projector according to claim 34, wherein said intermediate layer comprises a halfwave plate for rotating the polarization plane of the at least part of the beam through 90` .

Claim 44

A projector according to claim 34, wherein said intermediate layer comprises a first halfwave plate for rotating the polarization plane of the at least part of the beam through 900; and said mirror further comprises a second halfwave plate formed on a side opposite to said intermediate layer through said second dichroic reflecting layer, said first halfwave plate having a high-index axis having a direction substantially the same as that of a low-index axis of said second halfwave plate.

Claim 45

A projector according to claim 34, wherein said supply means includes: radiation beam supply means for supplying a radiation beam including first and second beams having different colors; and a color separation system for separating the radiation beam into the first and second beams, said color separation system having a dichroic mirror, said mirror having a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the incident side of each beam to reflect the first beam and transmit the second beam so as to separate the first beam from the second beam, said first dichroic reflecting layer having a smaller reflection range of one of two orthogonal polarized components of the first beam than that of the other of the two orthogonal polarized components, said intermediate layer rotating a polarization plane of at least part of a remaining beam of the one component of the first beam passing through said first dichroic reflecting layer, and said second dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said intermediate layer.

Claim 46

A projector according to claim 37, wherein said color separation system is used as said color synthesis system.

Claim 47

A projector comprising: radiation beam supply means for supplying a radiation beam including first and second beams having different colors; a first image generator for reflecting and modulating the first beam and generating a first image; a second image generator for reflecting and modulating the second beam and generating a second image; an optical system for separating the radiation beam into the first and second beams and directing the first and second beams toward said first and second image generators, and for synthesizing the first and second beams reflected and modulated by said first and second image generators, said system having a dichroic mirror, and said mirror having a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the side of said supply means to reflect the first beam and transmit the second beam, said first dichroic reflecting layer having a smaller reflection range of one of two orthogonal polarized components of the first beam than the other of the two orthogonal polarized components, said intermediate layer rotating a polarization plane of at least part of a remaining beam of the one component of the first beam passing through said first dichroic reflecting layer, and said second dichroic reflecting layer reflects the at least part of the beam whose polarization plane is rotated by said intermediate layer; and means for receiving through said optical system the first and second beams reflected and modulated by said first and second image generators and projecting the first and second images by using the first and second beams.

Claim 48

A projector comprising: radiation beam supply means for supplying a radiation beam including first and second beams having different colors; a first image generator for reflecting and modulating the first beam and generating a first image; a second image generator for reflecting and modulating the second beam and generating a second image; an optical system for separating the radiation beam into the first and second beams and directing the first and second beams toward said first and second image generators, and for synthesizing the first and second beams reflected and modulated by said first and second image generators, said system having a dichroic mirror, and said mirror having a first dichroic reflecting layer, an intermediate layer, and a second dichroic reflecting layer in the order named from the side of said supply means to reflect the first beam and transmit the second beam, said first dichroic reflecting layer having a smaller reflection range of one of two orthogonal polarized components of the first beam than the other of the two orthogonal polarized components, said intermediate layer rotating a polarization plane of at least part of a remaining beam of the one component of the first beam passing through said first dichroic reflecting layer, and said second dichroic reflecting layer reflects the at least part of the beam whose polarization plane is rotated by said intermediate layer; and means for receiving through said optical system the first and second beams reflected and modulated by said first and second image generators and projecting the first and second images by using the first and second beams.

Claim 49

A projector according to claim 39, wherein said intermediate layer comprises a halfwave plate for rotating the polarization plane of the at least part of the beam through 90` .

Claim 50

A projector according to claim 39, wherein said intermediate layer comprises a first halfwave plate for rotating the polarization plane of the at least part of the beam through 90°: and said projector further comprises a second halfwave plate formed on a side opposite to said intermediate layer through said second dichroic reflecting layer, said first halfwave plate having a high-index axis having a direction substantially the same as that of a low-index axis of said second halfwave plate.

Claim 51

A projector according to claim 39, wherein said optical system comprises a crossed dichroic prism having said mirror.

Claim 52

A projector according to claim 39, wherein the second beam includes third and fourth beams having colors different from each other and from that of the first beam; said second image generator comprises a first optical modulator for reflecting and modulating the third beam and forming a third image, and a second optical modulator for reflecting and modulating the fourth beam and forming a fourth image; and said optical means comprises a second dichroic mirror, said second dichroic mirror having a third dichroic reflecting layer, a second intermediate layer, and a fourth dichroic reflecting layer in the order named from the side of said supply means to reflect the third beam and transmit the fourth beam, said third dichroic reflecting layer having a smaller reflection range of one of two orthogonal polarized components of the third beam than that of the other of the two orthogonal polarized components, said second intermediate layer rotating a polarization plane of at least part of a remaining beam of the one component of the third beam passing through said third dichroic reflecting layer, and said fourth dichroic reflecting layer reflecting the at least part of the beam whose polarization plane is rotated by said second intermediate layer.

Claim 53

A projector according to claim 39, wherein said first and second image generators partially rotate the polarization planes of the first and second beams to generate the first and second images.

Claim 54

A projector according to claim 44, wherein said supply means comprises a radiation source for generating the radiation beam, and a polarizing beam splitter for directing the radiation beam from said radiation source toward said optical system and directing the first and second beams reflected and modulated by said first and second image generators toward said image projecting means through said optical system.

Claim 55

A dichroic mirror having a multilayered film for reflecting a beam of a given color, said multilayered film being constituted by a first reflecting layer consisting of a dielectric multilayered film, an intermediate layer consisting of a halfwave plate, and a second reflecting layer consisting of a dielectric multilayered film in the order named from the beam incident side.

Claim 56

A dichroic mirror having a multilayered film for reflecting a beam of a given color, said multilayered film being constituted by a first reflecting layer consisting of a dielectric multilayered film, an intermediate layer consisting of a halfwave plate, and a second reflecting layer consisting of a dielectric multilayered film in the order named from the beam incident side.

Claim 57

A dichroic mirror having a multilayered film for reflecting a beam of a given color, said multilayered film being constituted by a first reflecting layer consisting of a dielectric multilayered film, an intermediate layer consisting of a halfwave plate, a second reflecting layer consisting of a dielectric multilayered film, and an auxiliary layer consisting of a halfwave plate and having a low-index axis parallel to a high-index axis of said intermediate layer in the order named from the beam incident side.

Claim 58

A dichroic mirror having a multilayered film for reflecting a beam of a given color, said multilayered film being constituted by a first reflecting layer consisting of a dielectric multilayered film, an intermediate layer consisting of a halfwave plate, a second reflecting layer consisting of a dielectric multilayered film, and an auxiliary layer consisting of a halfwave plate and having a low-index axis parallel to a high-index axis of said intermediate layer in the order named from the beam incident side.

Claim 59

A dichroic mirror having a multilayered film for reflecting a polarized beam of a given color and transmitting a polarized beam of a color different from the given color, said multilayered film being constituted by a first reflecting layer consisting of a dielectric multilayered film, an intermediate layer consisting of a halfwave plate, a second reflecting layer consisting of a dielectric multilayered film, and an auxiliary layer consisting of a halfwave plate in the order named from the incident side of the beam of the given color, said auxiliary layer having a axis parallel to a high-index axis of said intermediate layer and substantially compensating for a change in a polarization plane of the polarized beam of the color different from the given color, and the change occurring in said intermediate layer.

Claim 60

A dichroic mirror having a multilayered film for reflecting a polarized beam of a given color and transmitting a polarized beam of a color different from the given color, said multilayered film being constituted by a first reflecting layer consisting of a dielectric multilayered film, an intermediate layer consisting of a halfwave plate, a second reflecting layer consisting of a dielectric multilayered film, and an auxiliary layer consisting of a halfwave plate in the order named from the incident side of the beam of the given color, said auxiliary layer having a axis parallel to a high-index axis of said intermediate layer and substantially compensating for a change in a polarization plane of the polarized beam of the color different from the given color, and the change occurring in said intermediate layer.