JP2001318221A - Optical filter intercepting long wavelength, optical filter intercepting short wavelength, cross prism, cross mirror and liquid crystal projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively decrease the difference in characteristics for S-polarized light and P-polarized light and deterioration in the characteristics with changes in the incident angle in an optical filter, which intercepts light of long wavelength or in an optical filter which intercepts light of short wavelength. SOLUTION: The optical filter intercepts light at long wavelength and consists of an optical multilayered film 30 and a pair of transparent substrates 10, 20 holding the film 30. At least either the half-value wavelength in the spectral transmittance for the P-polarized light or the half-value wavelength in the spectral transmittance for S-polarized light is in the range of 570 to 620 nm, and the difference of the half value wavelength between for the P-polarized light and the S-polarized light is <=50 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a long wavelength cutoff optical filter, a short wavelength cutoff optical filter, a cross prism,
Related to cross mirrors and liquid crystal projectors.

[0002]

2. Description of the Related Art A plurality of dielectric thin films of optically transparent materials having different refractive indices are stacked to reflect (or transmit) light in a specific wavelength region and transmit (or transmit) light in a wavelength region other than the above-mentioned region. Optical multilayer films for reflection) have been widely known,
Used in various optical devices. The “long-wavelength cutoff optical filter” mainly includes red light (approximately 57 wavelengths).
This is a filter that reflects light having a component of 0 nm or more at a high reflectance and transmits light having a shorter wavelength than red light at a high transmittance. This long-wavelength cutoff optical filter is a long-wavelength reflection mirror from a different point of view. The “short-wavelength cutoff optical filter” is a filter that mainly reflects blue light (light having a component of approximately 530 nm or less in wavelength) with a high reflectance and transmits light with a wavelength longer than the blue light with a high transmittance. This short-wavelength cutoff optical filter is a short-wavelength reflection mirror from a different point of view. When the above-described long-wavelength cutoff optical filter and short-wavelength cutoff optical filter are combined, “color separation” of light and “color synthesis” of color-separated light can be performed. For example, when white light is made incident on a long wavelength cutoff optical filter, a red light component included in the white light is separated as reflected light. Next, when the light transmitted through the long wavelength cutoff optical filter is made incident on the short wavelength cutoff optical filter, the blue light component is separated as reflected light. The green light component is separated by passing through the short wavelength cutoff optical filter. In this manner, white light can be separated into red, green, and blue color components. Conventionally known long wavelength cutoff optical filters and short wavelength cutoff optical filters have the following problems. First, the characteristics are different depending on whether the incident light is s-polarized light or p-polarized light. Second, the characteristics are significantly deteriorated when the incident angle changes from the normal angle. As an example,
FIG. 12 relates to the characteristics of a long wavelength cutoff optical filter that has been conventionally implemented. This long-wavelength wavelength filter has a “regular incident angle” set to 45 degrees.
(a) shows the characteristics when the S-polarized light and the P-polarized light are incident on the long wavelength cutoff optical filter at a regular incident angle: 45 degrees. Curve 12-1 shows the spectral transmittance for S-polarized light, and curve 12-2 shows the spectral transmittance for P-polarized light.

As shown in FIG. 12A, this long-wavelength cutoff optical filter functions as a good long-wavelength cutoff optical filter or a long-wavelength reflection mirror for S-polarized light, but functions as a long-wavelength reflection mirror for P-polarized light. It cannot work well. FIG.
(B) shows that the incident angle of the incident light is the regular incident angle (4
5 °), the changes in the spectral transmittance when the angles are 40 ° and 50 ° are shown. When the incident angle becomes 50 degrees, the spectral transmittance becomes as shown by a curve 12-11 for S-polarized light, and as shown by a curve 12-21 for P-polarized light. When the incident angle becomes 40 degrees, the spectral transmittance becomes as shown by a curve 12-12 for S-polarized light, and as shown by a curve 12-22 for P-polarized light. In other words, even if a good spectral transmittance is exhibited for S-polarized light incident at a normal incident angle: 45 degrees, the incident angle is 4 degrees.
When the angle changes to 0 or 50 degrees, even for S-polarized light,
The cutoff wavelength (cutoff wavelength) changes greatly. FIG. 13 relates to the characteristics of a short-wavelength cutoff optical filter that is conventionally implemented. This short-wavelength wavelength filter also has the “regular incident angle” set to 45 degrees. (a)
Is the normal incidence angle: 4 for the short wavelength cutoff optical filter.
The graph shows characteristics when S-polarized light and P-polarized light are respectively incident at 5 degrees. Curve 13-1 shows the spectral transmittance for S-polarized light, and curve 13-2 shows the spectral transmittance for P-polarized light.
As shown in FIG. 13A, this short-wavelength cutoff optical filter functions as a good short-wavelength cutoff optical filter or short-wavelength reflection mirror for S-polarized light, but functions sufficiently for P-polarized light. I can't. FIG. 13B shows a change in the spectral transmittance when the incident angle of the incident light is 40 degrees and 50 degrees with respect to the normal incident angle (45 degrees). When the incident angle becomes 50 degrees, the spectral transmittance becomes as shown by a curve 13-11 for S-polarized light, and as shown by a curve 13-21 for P-polarized light. When the incident angle becomes 40 degrees, the spectral transmittance becomes as shown by a curve 13-12 for the S-polarized light, and the curve 1 for the P-polarized light.
As shown in 3-22. That is, the normal incident angle: 45
Even if it shows good spectral transmittance for S-polarized light incident with a degree, if the incident angle changes to 40 degrees or 50 degrees, the cut-off wavelength (cut-off wavelength) also greatly changes for S-polarized light. .

When a filter or mirror using an optical multilayer film is used, linearly polarized light separated by a polarizing beam splitter or the like is often used in order to reduce light loss accompanying transmission or reflection. In such a case, if the optical characteristics of the filter or the mirror differ depending on whether the incident light is the S-polarized light or the P-polarized light, the filter or the mirror restricts the polarization state of the incident light, which is not preferable. Also,
When using a filter or a mirror whose optical characteristics are significantly degraded due to a change in the incident angle, it is necessary to determine the direction of the incident light with extremely high accuracy, and it becomes difficult to use a light beam having a certain degree of divergence and convergence. This is a severe limitation on optical design.

[0005]

SUMMARY OF THE INVENTION In view of the above, the present invention addresses the above-mentioned problems in long-wavelength cutoff optical filters and short-wavelength cutoff optical filters, namely, differences in characteristics between S-polarized light and P-polarized light and changes in incident angle. It is an object to effectively reduce the accompanying characteristic deterioration.

[0006]

The long-wavelength cutoff filter of the present invention is an "optical filter for blocking long-wavelength light" and is specified as follows. That is, the long-wavelength cutoff filter includes at least an optical multilayer film and a pair of transparent substrates sandwiching the optical multilayer film. At least one of the half-value wavelength of the spectral transmittance for P-polarized light (the wavelength at which the transmittance becomes 50%) and the half-value wavelength of the spectral transmittance for S-polarized light is in the range of 570 to 620 nm. Furthermore, the “difference in each half-value wavelength” for P-polarized light and S-polarized light is 5
0 nm or less (claim 1). Such a long-wavelength cut-off optical filter has at least two layers between a pair of transparent substrates.
An optical multi-layer film composed of seven optical films and at least one adhesive layer for adhering the optical multi-layer film to the transparent substrate can be arranged (claim 2). A particularly preferred configuration is one in which the adhesive layer is composed of one layer and the optical multilayer film is composed of 37 layers. In this case, the refractive index of the adhesive layer is 1.50 to 1.50.
1.52, the first of the 37 multilayer optical multilayer films.
The refractive index of the layer and the 37th layer is in the range of 1.62 to 1.64, and the refractive index of the even-numbered layer of the 2nd to 36th layers is in the range of 1.70 to 2.11. , The refractive index of the odd-numbered layer is in the range of 2.30 to 2.50.
(Claim 3). In this case, when the optical film thickness of the even-numbered layer in the optical multilayer film: d _2n (n = 1, 2, 3,... 18), the same film thickness for d = 4 to 15: d _{8 to} d ₃₀ =
Assuming that 1, d ₂ = 0.25, d ₄ = 1.120, d ₆
= 1.08, d ₃₂ = 1.08, d ₃₄ = 1.120, d ₃₆
= 0.25, and the thickness of the odd-numbered layer: d _{2n + 1} (n =
0, 1, 2, 3,. . 18), when the same film thickness for d = 3 to 15: d _{7 to} d ₃₁ = 1, d ₃ = 1.
06, d ₅ = 1.04, d ₃₃ = 1.04, d ₃₅ = 1.0
6, and d ₁ and d ₃₇ are both preferably 0.75 or less (claim 4). Long wavelength cutoff optical filter of the fourth aspect, in the material, the pair of the transparent substrates formed of glass, a first layer and a 37 layer of the optical multilayer film is formed by Al ₂ O _3, the The even-numbered layer of the second to 36th layers is L
a ₂ O ₃ · 1.2 Al ₂ O _{3 is used} to form odd-numbered layers of TiO 2
₂ can be configured respectively (claim 5).

In the long wavelength cutoff optical filter according to the fifth aspect, the optical film thickness of each layer of the optical multilayer film is set to the first value.
Layer and the 37th layer with a wavelength of 0.3
02λ, wavelength of the second layer and the 36th layer: λ = 600 nm
0.077λ with respect to the wavelength of the third and 35th layers:
0.328λ for λ = 600 nm, wavelength of the fourth and 34th layers: 0.346λ for λ = 600 nm,
The fifth and 33rd layers have a wavelength of 0.321λ for λ = 600 nm, and the sixth and 32nd layers have a wavelength of λ = 60 nm.
0.334λ for 0 nm, and 0.309λ for the seventh to 31st layers for a wavelength: λ = 600 nm (claim 6). In the long-wavelength cutoff optical filter according to any one of the first to sixth aspects, the incident angle on the optical multilayer film can be set to approximately 45 degrees (claim 7). The short-wavelength cutoff filter of the present invention is an “optical filter that blocks short-wavelength light” and is specified as follows. That is, the short-wavelength cutoff optical filter includes at least an optical multilayer film and a pair of transparent substrates sandwiching the optical multilayer film. At least one of the half-value wavelength of the spectral transmittance for P-polarized light and the half-value wavelength of the spectral transmittance for S-polarized light is in the range of 485 to 530 nm.
Furthermore, the “difference between half-value wavelengths” for P-polarized light and S-polarized light
Is 50 nm or less (claim 8). Such a short-wavelength cutoff optical filter includes an optical multilayer film including at least 27 optical films between a pair of transparent substrates, and at least one adhesive layer for bonding the optical multilayer film to the transparent substrate. (Claim 9). A particularly preferred configuration is one in which the adhesive layer is composed of one layer and the optical multilayer film is composed of 37 layers. In this case, the refractive index of the adhesive layer is 1.50.
To 1.52, the refractive index of the first and 37th layers in the 37-layer optical multilayer film is in the range of 1.62 to 1.64, and an odd number of the second to 36th layers. The refractive index of the first layer is in the range of 1.70 to 2.11, and the refractive index of the even-numbered layer is in the range of 2.30 to 2.50 (claim 10).

In this case, when the optical film thickness of the even-numbered layer in the optical multilayer film: d _2n (n = 1, 2, 3,... 18), the same film thickness for d = 4 to 15: d ₈ to d ₃₀ =
Assuming that 1, d ₂ = 0.5, d ₄ = 0.92, d ₆ =
0.92, d ₃₂ = 0.950, d ₃₄ = 1.0, d ₃₆ =
0.5, and the thickness of the odd-numbered layer: d _{2n + 1} (n = 0,
1, 2, 3,. . 18), when the same film thickness for d = ₃ to 14: d _{7 to} d ₂₉ = 1, d ₃ = 1.0,
_{d 5 = 0.95, d 31 =} 0.92, d 33 = 0.92, d
₃₅ = 1.0, and d ₁ and d ₃₇ are both preferably 1.45 or more (claim 11). In the long-wavelength cutoff optical filter according to the eleventh aspect, the pair of transparent substrates is formed of glass, and the first and 37th layers of the optical multilayer film are formed of A.
formed by l ₂ O _3, that the odd-numbered layer of the second layer to the 36th layer is formed by _{La 2 O 3 · 1.2Al 2 O} 3, respectively constituting the even-numbered layers by TiO ₂ (Claim 12). In the short-wavelength cutoff optical filter according to the twelfth aspect, the optical thickness of each layer of the optical multilayer film is set to 0.302λ for the first layer and the 37th layer for the wavelength: λ = 700 nm, Wavelength of the 36th layer: λ = 4
0.161λ for 25 nm, the third and 35th layers have a wavelength of 0.323λ for λ = 425 nm, and the fourth layer has a wavelength of 0.297λ for λ = 425 nm, 34th.
Layer: 0.323λ for wavelength: λ = 425 nm, 5th
Layer 0.307λ for wavelength: λ = 425 nm, third
The third layer has a wavelength of 0.297λ for λ = 425 nm, the sixth layer has a wavelength of 0.297λ for λ = 425 nm, and the 32nd layer has a wavelength of 0.397λ for λ = 425 nm.
The 31st layer has a wavelength of 0.297 for λ = 425 nm.
λ, the seventh to thirtieth layers can be set to 0.323λ with respect to the wavelength: λ = 425 nm (claim 13). In the short-wavelength cutoff optical filter according to any one of claims 8 to 13, the incident angle on the optical multilayer film can be set to approximately 45 degrees (claim 14). Note that the above “La”
₂ O ₃ 1.2 Al ₂ O ₃ ”is trade name“ Substance M3
It is commercially available as "Merck GmbH", and is hereinafter simply referred to as "M3" to avoid complication.

The "cross prism" of the present invention comprises a long-wavelength cutoff optical filter according to claim 7, wherein the transparent substrate is a prism, and a short-wavelength cutoff optical filter, wherein the transparent substrate is a prism. Are constructed by combining the optical multilayer films so as to be orthogonal to each other.
5). The long-wavelength blocking optical filter according to claim 7, wherein the "cross mirror" of the present invention uses a transparent substrate as a prism;
A short-wavelength cutoff optical filter according to claim 14 wherein the transparent substrate is a prism is combined with each other so that the respective optical multilayer films are orthogonal to each other (claim 16). A liquid crystal projector according to a seventeenth aspect has a liquid crystal display for red, blue, and green, a lighting unit, a light combining unit, and an imaging optical system. The “liquid crystal display for red” is a reflection type liquid crystal display that displays an image of a red image component.
The “liquid crystal display for blue” is a reflection type liquid crystal display that displays an image of a blue image component. The “green liquid crystal display” is a reflective liquid crystal display that displays an image of a green image component. "Illumination means" is means for irradiating the liquid crystal display with light. `` Photosynthesis means ''
Is means for combining light spatially modulated by the image of each liquid crystal display as a single light flux. The “imaging optical system” displays a color image by forming an image of the light combined by the light combining means on a screen. The cross prism according to claim 15 is used as a part of the illumination means and the light combining means. The liquid crystal projector according to the eighteenth aspect has a liquid crystal display for red, blue, and green, an illuminating unit, a light combining unit, and an imaging optical system. The imaging optical system is the same as that of the seventeenth aspect. The liquid crystal displays for red, blue, and green respectively display images of red, blue, and green components, but are of a "transmissive type" unlike the one described in claim 17. The "illuminating means" is a means for irradiating each of the liquid crystal displays with light. The “light combining unit” is a unit that combines light spatially modulated by the image of each liquid crystal display as a single light flux. The cross mirror according to claim 16 is used as the light combining means.

[0010]

In FIG. 1, reference numeral 30 denotes an optical multilayer film, and reference numerals 10 and 20 denote a pair of transparent substrates sandwiching the optical multilayer film 30. The optical multilayer film 30 is formed on the surface of the transparent substrate 10,
0. The number of optical films in the optical multilayer film 30 is at least 27 layers. The above configuration is common to the long wavelength cutoff optical filter and the short wavelength cutoff optical filter. Depending on the specific configuration of the optical multilayer film 30, it is determined whether to be a long wavelength cutoff optical filter or a short wavelength cutoff optical filter. If the number of optical films in the optical multilayer film 30 is smaller than 27, the optical characteristics for P-polarized light will be insufficient. In order to improve the optical characteristics with respect to the P-polarized light, the number of layers of the optical film is preferably as large as possible, but from the viewpoint of actual production, the upper limit of the number of layers is considered to be about 60 layers. FIG. 2 shows a cross prism according to an embodiment of the present invention. The optical multilayer film 31 has a function of blocking long wavelength light (reflecting long wavelength light), and the optical multilayer film 32 has a function of blocking short wavelength light (reflecting short wavelength light). These optical multilayer films 31, 32 are combined so as to be orthogonal to each other, and prisms 11, 12, 2
1 and 22. Each optical multilayer film is formed on one of the prisms supporting the optical multilayer film and is bonded to the other prism by an adhesive layer. For example, as shown in FIG.
When a (parallel light flux) is incident, the incident white light is incident on the optical multilayer films 31 and 32 at an incident angle of 45 degrees, but the red light component is reflected by the long wavelength cutoff filter 31. The light is emitted from the prism 11 as “red light”. Further, the blue light component is short-wavelength cutoff optical filter 32.
Is emitted from the prism 22 as “blue light”. Further, the green light component passes through both the optical multilayer films 31 and 32, and is emitted from the prism 12 as “green light”. As described above, by using the cross prism shown in FIG. 2, the white light is converted into the red light
It can be separated into blue light and green light. FIG. 3 shows an embodiment of the cross mirror according to claim 16.
The cross mirror is structurally the same as the cross prism shown in FIG. Therefore, the same reference numerals as in FIG. 2 are used.

When a cross mirror is used, color synthesis can be performed. As shown in the figure, red light (supposed to be a parallel light beam) is incident on the prism 11 from the slope thereof, and
When green light (supposed to be a parallel light beam) is incident on the inclined surface of the prism 2 and blue light (supposed to be a parallel light beam) is incident on the prism 22 from the inclined surface, these color lights are converted into the optical multilayer films 31 and 32. At an incident angle of 45 degrees. The red light is reflected by the optical multilayer film 31, the blue light is reflected by the optical multilayer film 32, and the green light is transmitted through both the optical multilayer films 31 and 32. Therefore, these lights are color-combined with each other.

[0012]

Here, specific examples of the long wavelength cutoff optical filter will be described. Example 1 Long-wavelength blocking optical filter Material Film thickness Film thickness ratio Transparent substrate Glass prism First layer Al ₂ O ₃ 0.302λ (λ = 400 nm) 0.65 Second layer M3 0.077λ (λ = 600 nm) 0.25 Three-layer TiO ₂ 0.328λ (λ = 600 nm) 1.06 Fourth layer M3 0.346λ (λ = 600 nm) 1.12 Fifth layer TiO ₂ 0.321λ (λ = 600 nm) 1.04 Sixth layer M3 0.334λ ( λ = 600 nm) 1.08 Seventh layer TiO ₂ 0.309λ (λ = 600 nm) 1.0 Eighth layer M3 0.309λ (λ = 600 nm) 1.0 Ninth layer TiO ₂ 0.309λ (λ = 600 nm) 0 10th layer M3 0.309λ (λ = 600 nm) 1.0 11th layer TiO ₂ 0.309λ (λ = 600 nm) 1.0 12th layer M3 0.309λ (λ = 600 nm) 1.0 13th layer TiO ₂ 0.309 λ (λ = 600 nm) 1.0 Fourteenth layer M3 0.309λ (λ = 600 nm) 1.0 Fifteenth layer TiO ₂ 0.309λ (λ = 600 nm) 1.0 Sixteenth layer M3 0.309λ (λ = 600 nm) 1 . 0 17th layer TiO ₂ 0.309λ (λ = 600 nm) 1.0 18th layer M3 0.309λ (λ = 600 nm) 1.0 19th layer TiO ₂ 0.309λ (λ = 600 nm) 1.0 20th layer M3 0.309 λ (λ = 600 nm) 1.0 21st layer TiO ₂ 0.309λ (λ = 600 nm) 1.0 22nd layer M3 0.309λ (λ = 600 nm) 1.0 23rd layer TiO ₂ 0.309λ (λ = 600 nm) 1.0 24th layer M3 0.309λ (λ = 600 nm) 1.0 25th layer TiO ₂ 0.309λ (λ = 600 nm) 1.0 26th layer M3 0.309λ (λ = 600 nm) 1.0 27th layer TiO ₂ 0.309λ (λ = 600 nm) 1.0 28th layer M3 0.309λ (λ = 600 nm) 1.0 29th layer TiO ₂ 0.309λ (λ = 600 nm) 1.0 30th layer M3 0.309λ (λ = 600 nm) ) 1.0 31st layer TiO ₂ 0.309λ (λ = 600 nm) 1.0 32nd layer M3 0.334λ (λ = 600 nm) 1.08 33rd layer TiO ₂ 0.321λ (λ = 600 nm) 1.04 34th Layer M3 0.346λ (λ = 600 nm) 1.12 35th layer TiO ₂ 0.328λ (λ = 600 nm) 1.06 36th layer M3 0.077λ (λ = 600 nm) 0.25 37th layer Al ₂ O ₃ 0.302λ (λ = 400 nm) ) 0.65 adhesive layer substrate glass prism.

The refractive index of Al ₂ O ₃ is 1.63 and M 3
Has a refractive index of 1.865 and TiO _{2 has} a refractive index of 2.391.
It is. The refractive index of the adhesive layer is 1.51, and the refractive index of the glass prism is 1.517. FIG. 4A shows the first embodiment.
3 shows the spectral transmittance at an incident angle of 45 ° (normal incident angle) of the long wavelength cutoff optical filter. Curve 4-1 is for S-polarized light, and curve 4-2 is for P-polarized light. FIG. 4B shows the spectral transmittance when the incident angle to the long-wavelength cutoff optical filter of the first embodiment is changed to 50 degrees and 40 degrees with respect to 45 degrees (normal incident angle). I have. Curve 4-11 shows that the incident angle of S-polarized light is 5
When the angle reaches 0 degrees, the curve 4-12 is also when the angle reaches 40 degrees. A curve 4-21 is obtained when the incident angle of the P-polarized light is 50 degrees, and a curve 4-22 is obtained when the incident angle is also 40 degrees. When the optical characteristics shown in FIG. 4 are compared with the optical characteristics of the conventional long-wavelength cutoff optical filter shown in FIG. 12, the following can be immediately understood. That is, first, at the normal incident angle, the minimum value of the transmittance of the P-polarized light is smaller than that of the conventional example, and the minimum value of the transmittance for the P-polarized light is improved to almost zero. Secondly, at a normal incident angle: 45 degrees, the difference between the half-value wavelengths of the transmittances for S and P polarized lights is as follows.
In the conventional example, the thickness is 75 nm or more.
m, and the difference in optical characteristics between S-polarized light and P-polarized light is greatly reduced. Incidentally, the half-value wavelength of the transmittance for S-polarized light is 571 nm, and that for P-polarized light is 599 nm. Third, deterioration of optical characteristics due to a change in the incident angle is effectively reduced. This is shown in FIG. 4B and FIG.
It will be clear if (b) is compared. That is, the first embodiment
Is an optical filter that blocks long-wavelength light, and includes at least an optical multilayer film (first to thirty-seventh layers).
And a pair of transparent substrates (glass prisms) that sandwich the substrate
At least one of the half-value wavelength (599 nm) of the spectral transmittance for P-polarized light and the half-value wavelength (571 nm) of the spectral transmittance for S-polarized light is 57%.
It is in the range of 0 to 620 nm, and the difference (28 nm) between each half-value wavelength for P-polarized light and S-polarized light is 50 nm or less (Claim 1).

The space between the pair of transparent substrates is at least
Also, an optical multilayer film composed of 27 optical films and this optical multilayer film
It is composed of at least one adhesive layer for adhering the film to the transparent substrate.
(Claim 2), the adhesive layer is one layer, and the bending of the adhesive layer
The folding ratio is in the range of 1.50 to 1.52, and the optical multilayer
With a 37-layer configuration, the first layer and the 37th layer have a refractive index of 1.6.
2 to 1.64, and among the second to thirty-sixth layers.
The refractive index of the even-numbered layer is in the range of 1.70 to 2.11.
And the refractive index of the odd-numbered layer is in the range of 2.30 to 2.50.
(Claim 3). In addition, even-numbered optical multilayer films
Optical thickness of eye layer: d_2n(N = 1, 2, 3,... 1
8) In the same film thickness for d = 4 to 15: d₈~
d₃₀= 1, d_Two= 0.25, d_Four= 1.12
0, d₆= 1.08, d₃₂= 1.08, d_{Three Four}= 1.12
0, d₃₆= 0.25, and the thickness of the odd-numbered layer: d
_{2n + 1}(N = 0, 1, 2, 3,... 18), n =
Same film thickness for 3 to 15: d₇~ D_{Three 1}= 1
D_Three= 1.06, d_Five= 1.04, d₃₃= 1.04,
d₃₅= 1.06 and d₁And d₃₇But both are 0.75 or less
(Claim 4). In addition, a pair of transparent substrates
(Glass prism), the first layer of the optical multilayer film
And the 37th layer is made of Al_TwoO_ThreeFormed from the second layer to the
The even-numbered layer of the 36 layers is La_TwoO_Three・ 1.2Al_Two
O_Three(M3), and the odd-numbered layers are made of TiO. _TwoTo
(Claim 5). And optical multilayer film
The optical thickness of each layer is such that the first layer and the 37th layer have a wavelength:
0.302λ for λ = 400 nm, second layer and
36 layers have a wavelength of 0.077λ for λ = 600 nm,
The third layer and the 35th layer have a wavelength: λ = 600 nm.
0.328λ, the fourth and 34th layers have a wavelength: λ = 60
0.346λ for 0 nm, 5th layer and 33rd layer
Wavelength: 0.321λ for λ = 600nm, 6th layer and
And the 32nd layer has a wavelength of 0.33 for λ = 600 nm.
4λ, 7th to 31st layers for wavelength: λ = 600 nm
Is 0.309λ (claim 6),
The angle of incidence is used as approximately 45 degrees (claim 7). Next
Example 2 is an example of a “short wavelength cutoff optical filter”.
It is.

Example 2 Short-wavelength cutoff optical filter Material Film thickness Film thickness ratio Transparent substrate Glass prism First layer Al ₂ O ₃ 0.302λ (λ = 700 nm) 1.53 Second layer TiO ₂ 0.161λ (λ = 425 nm) 0.50 Third layer M3 0.323λ (λ = 425 nm) 1.00 Fourth layer TiO ₂ 0.297λ (λ = 425 nm) 0.92 Fifth layer M3 0.307λ (λ = 425 nm) 0.95 Sixth layer TiO ₂ 0.297λ (λ = 425 nm) 0.92 Seventh layer M3 0.323λ (λ = 425 nm) 1.0 Eighth layer TiO ₂ 0.323λ (λ = 425 nm) 1.0 Ninth layer M3 0.323λ (λ = 425 nm) 1.0 1.0 10th layer TiO ₂ 0.323λ (λ = 425 nm) 1.0 11th layer M3 0.323λ (λ = 425 nm) 1.0 12th layer TiO ₂ 0.323λ (λ = 425 nm) 1.0 13th layer M3 0.323λ (λ = 425nm) 1.0 14th layer _{TiO 2 0.323λ (λ = 425nm)} 1.0 15th layer M3 0.323λ (λ = 425nm) 1.0 16 layer TiO ₂ 0.323 (λ = 425nm) 1.0 17 layer M3 0.323λ (λ = 425nm) 1.0 18 layer _{TiO 2 0.323λ (λ = 425nm)} 1.0 19 layer M3 0.323λ (λ = 425nm) 1 . 0 20th layer TiO ₂ 0.323λ (λ = 425 nm) 1.0 21st layer M3 0.323λ (λ = 425 nm) 1.0 22nd layer TiO ₂ 0.323λ (λ = 425 nm) 1.0 23rd layer M3 0.323 λ (λ = 425 nm) 1.0 24th layer TiO ₂ 0.323λ (λ = 425 nm) 1.0 25th layer M3 0.323λ (λ = 425 nm) 1.0 26th layer TiO ₂ 0.323λ (λ = 425 nm) 1.0 27th layer M3 0.323λ (λ = 425 nm) 1.0 28th layer TiO ₂ 0.323λ (λ = 425 nm) 1.0 29th layer M3 0.323λ (λ = 425 nm) 1.0 30th layer TiO ₂ 0.323λ (λ = 425 nm) 1.0 31st layer M3 0.297λ (λ = 425 nm) 0.92 32nd layer TiO ₂ 0.307λ (λ = 425 nm) 0.95 33rd layer M3 0.297λ (λ = 425 nm) ) 0.92 4-layer _{TiO 2 0.323λ (λ = 425nm)} 1.0 35 layer M3 0.323λ (λ = 425nm) 1.0 36 layer _{TiO 2 0.161λ (λ = 425nm)} 0.50 37th layer Al ₂ O ₃ 0.302λ (λ = 700 nm) 1.53 Adhesive layer Substrate Glass prism.

The refractive index of the adhesive layer is 1.51, and the refractive index of the glass prism is 1.517. FIG. 5A shows the spectral transmittance of the long wavelength cutoff optical filter of the second embodiment at an incident angle of 45 degrees (normal incident angle). Curve 5-1 is S
For polarized light, curve 5-2 is for P-polarized light. FIG. 5B shows the spectral transmittance when the incident angle to the long-wavelength cutoff optical filter of the second embodiment is changed to 50 degrees and 40 degrees with respect to 45 degrees (normal incident angle). I have. Curve 5-11 shows that the incident angle of S-polarized light is 50.
At that time, curve 5-12 is also at 40 degrees. A curve 5-21 is obtained when the incident angle of the P-polarized light is 50 degrees, and a curve 5-22 is obtained when the incident angle is also 40 degrees. When the optical characteristics shown in FIG. 5 are compared with the optical characteristics of the conventional long wavelength cutoff optical filter shown in FIG. 13, the following can be immediately understood. First, at a normal incident angle, the minimum value of the transmittance of P-polarized light is smaller than that of the conventional example, and the minimum value of the transmittance of P-polarized light is improved to almost zero. Second, at a normal angle of incidence: 45 degrees,
The difference between the half-value wavelengths of the transmittance for the S and P polarized light is 90 nm or more in the conventional example, but is about 28 nm in the second embodiment, and the difference between the optical characteristics for the S polarized light and the P polarized light is greatly reduced. Incidentally, the half value wavelength of the transmittance for S-polarized light is 519 nm, and that for P-polarized light is 491 nm. Third
In addition, the deterioration of the optical characteristics due to the change in the incident angle is effectively reduced. This will be clear from the comparison between FIG. 5B and FIG. 13B. That is, the optical filter of Example 2 is an optical filter that blocks short-wavelength light, and includes at least an optical multilayer film (first to thirty-seventh layers) and a pair of transparent substrates (a glass prism) that sandwich the optical multilayer film. ), And the half-value wavelength (49) in the spectral transmittance for P-polarized light.
1 nm) and the half-value wavelength (5
19 nm) is at least 485 to 530 nm.
And the difference (28 nm) between each half-value wavelength for P-polarized light and S-polarized light is 50 nm or less (claim 8). In addition, between the pair of transparent substrates, an optical multilayer film including at least 27 optical films and at least one adhesive layer for bonding the optical multilayer film to the transparent substrate are configured. 10).

Further, the adhesive layer is one layer, and the refractive index of this adhesive layer is
Rate is in the range of 1.50 to 1.52 and the optical multilayer film is 3
The first and 37th layers have a refractive index of 1.62 in a seven-layer structure.
~ 1.64, which is odd among the second to thirty-sixth layers.
The refractive index of the number-th layer is in the range of 1.70 to 2.11.
And the refractive index of the even-numbered layer is in the range of 2.30 to 2.50.
(Claim 10), the even-numbered optical multilayer film
Optical thickness of layer: d_2n(N = 1,2,3, ... 18)
Where n = 4 to 15 and the same film thickness: d₈~ D₃₀=
When set to 1, d_Two= 0.5, d_Four= 0.92, d₆=
0.92, d₃₂= 0.950, d₃₄= 1.0, d₃₆=
0.5, the thickness of the odd-numbered layer: d_{2n + 1}(N = 0,
1, 2, 3,. . 18), for n = 3 to 14
The same thickness: d ₇~ D₂₉= 1, d_Three= 1.0,
d_Five= 0.95, d₃₁= 0.92, d₃₃= 0.92, d
₃₅= 1.0 and d₁And d₃₇But both are 1.45 or more
(Claim 11). Further, a pair of transparent substrates (glass plates)
Rhythm) is made of glass, and the first layer of the optical multilayer film and
And the 37th layer is Al_TwoO_ThreeAnd the second to thirty-sixth layers.
The odd-numbered layer of the layers is La_TwoO_Three・ 1.2Al_TwoO
_Three(M3), the even-numbered layers are TiO_TwoBy
(Claim 12), and the optical
The first layer and the 37th layer have a wavelength of λ = 700 nm.
0.302λ, the second layer and the 36th layer have a wavelength: λ
= 0.161λ for 425 nm, third layer and third
The five layers have a wavelength of 0.323λ for a wavelength of λ = 425 nm,
Four layers have a wavelength of 0.297λ for λ = 425 nm,
Thirty-four layers have a wavelength of 0.323λ for λ = 425 nm,
The fifth layer has a wavelength: 0.307λ for λ = 425 nm,
The 33rd layer has a wavelength of 0.297 for λ = 425 nm.
λ, sixth layer is 0.297 for wavelength: λ = 425 nm
λ, the 32nd layer is 0.30 for wavelength: λ = 425 nm
7λ, the 31st layer is 0.2 for the wavelength: λ = 425 nm.
97λ, 7th to 30th layers correspond to wavelength: λ = 425 nm.
Is 0.323λ (claim 13). Also optical multilayer
The angle of incidence on the film is used as approximately 45 degrees.
4). In the first and second embodiments described above, in the first and second layers,
In the composed optical multilayer film, "Low optical thickness
The part where the refractive index layer and the high refractive index layer are laminated monotonously and alternately
Minutes ”, for example, the seventh to 31st layers in Example 1
Each layer constituting part of the seventh layer to the thirtieth layer in Example 2.
Is called a “basic periodic layer”.

As can be seen from the first and second embodiments, in these embodiments, the thickness of each layer is equal to the thickness of the basic periodic layer on both sides (the glass prism side) of the portion constituting the basic periodic layer. Differently, each layer has an individual thickness. This is because the thickness of each layer in the above-described portion (the portion on both sides of the basic periodic layer) is reduced in order to reduce the amplitude of “waves of transmittance (called ripples) in the high transmittance portion in the spectral transmittance characteristics”. This is the result of optimizing. One of the features of the present invention is that, in the low refractive index layer and the high refractive index layer constituting the optical multilayer film, the refractive index of the low refractive index layer is higher than that of the conventional material (1.70 to 2). .11). As described above, by using a material having a higher refractive index for the low refractive index layer than the conventional material (having a refractive index of 1.68 or less), the difference between the optical characteristics for S-polarized light and the optical characteristics for P-polarized light (in the above example, For example, the difference in the half-value wavelength in the spectral transmittance characteristic between the S-polarized light and the P-polarized light can be reduced. If the refractive index of the low refractive index layer is smaller than 1.70, the above “difference in half-value wavelength” cannot be reduced to 50 nm or less. Conversely, when the refractive index of the low refractive index layer is larger than 2.11, the difference between the refractive index of the high refractive index layer and the refractive index of the high refractive index layer becomes small, so that a multilayer film of 100 layers or more is required to obtain desired optical characteristics. Lacks practicality in terms of productivity. Here, as a comparative example, an example of “when the refractive index of the low refractive index layer is lower than 1.70” will be given for each of the long wavelength cutoff optical filter and the short wavelength cutoff optical filter. FIG. 6 shows the characteristics (spectral transmittance) of the long-wavelength cutoff optical filter in a manner similar to FIG. In the spectral transmittance shown in FIG.
1 is for an incident angle of 45 degrees for s-polarized light, and curve 6-2 is for an incident angle of 45 degrees for p-polarized light. In FIG. 6B, curves 6-11 and 6
The curve -12 indicates the case where the incident angle changes to 50 degrees and 40 degrees for the S-polarized light, and the curves 6-21 and 6-22 indicate the cases where the incident angles change to 50 degrees and 40 degrees for the P-polarized light.

FIG. 7 shows the characteristics (spectral transmittance) of the short-wavelength cutoff optical filter according to FIG. FIG. 7 (a)
In the spectral transmittance shown in FIG. 7, curve 7-1 is for an incident angle of 45 degrees with respect to S-polarized light, and curve 7-2 is for P
Incident angle for polarized light: 45 degrees. FIG.
In (b), curves 7-11 and 7-12 are obtained when the incident angles of the S-polarized light are changed to 50 degrees and 40 degrees,
Curves 7-21 and 7-22 are obtained when the incident angles of the P-polarized light are changed to 50 degrees and 40 degrees. In the examples shown in FIGS. 6 and 7, the material of the high refractive index layer is TiO ₂ , and the material of the low refractive index layer is Al ₂ O ₃ (refractive index: 1.63). In each case, the film thickness on both sides of the basic periodic layer is optimized to reduce the ripple. The number of layers of the optical multilayer film is shown in FIG.
In the example of FIG. 7, there are 19 layers, and in the example of FIG. 7, there are 21 layers. These FIG. 6,
In the example of FIG. 7, the difference between the half-value wavelengths for the S-polarized light and the P-polarized light is larger than 50 nm. Further, the minimum transmittance for P-polarized light does not become zero. Also in the examples shown in FIGS. 6 and 7, the minimum transmittance for P-polarized light can be made closer to 0 by increasing the number of optical multilayer films. However, the difference between the half-value wavelengths for S-polarized light and P-polarized light cannot be reduced. Another feature of the present invention is that the number of optical multilayer films is 27 or more. Increasing the number of layers of the optical multilayer film is particularly effective for improving characteristics for P-polarized light. When the number of layers of the optical multilayer film is 26 or less, the improvement of the characteristics with respect to S-polarized light is not sufficient. As a comparative example, an example of the spectral transmittance when the number of layers of the optical multilayer film is small will be described for each of the long wavelength cutoff optical filter and the short wavelength cutoff optical filter.
FIG. 8 shows characteristics (spectral transmittance) of a long-wavelength cutoff optical filter.
Is shown in FIG. In the spectral transmittance shown in FIG. 8A, the curve 8-1 shows an incident angle of S-polarized light: 45.
Curve 8-2 is for an incident angle of 45 degrees for P-polarized light. In FIG. 8B, curves 8-11 and 8-12 indicate that the incident angle is 5 for S-polarized light.
It is a case where it changes to 0 degree and 40 degrees, and curve 8-2
1,8-22 have an incident angle of 50 degrees and 40 for P-polarized light.
This is the case when the temperature changes.

FIG. 9 shows the characteristics (spectral transmittance) of the short-wavelength cutoff optical filter in accordance with FIG. FIG. 9 (a)
In the spectral transmittance shown in FIG. 7, curve 9-1 is for an incident angle of 45 degrees with respect to S-polarized light, and curve 9-2 is for P.
Incident angle for polarized light: 45 degrees. FIG.
In (b), curves 9-11 and 9-12 are obtained when the incident angles of the S-polarized light are changed to 50 degrees and 40 degrees, respectively.
Curves 9-21 and 9-22 are obtained when the incident angles of the P-polarized light are changed to 50 degrees and 40 degrees. In the examples shown in FIGS. 8 and 9, the material of the high refractive index layer is TiO ₂ , and the material of the low refractive index layer is M3 as in the first and second embodiments. In each case, the film thickness on both sides of the basic periodic layer is optimized to reduce the ripple. The number of optical multilayer films is 25 in the example of FIG. 8 and 23 in the example of FIG. 8 and 9, the difference in half-value wavelength for S-polarized light and P-polarized light is smaller than 50 nm, but the minimum transmittance for P-polarized light does not become zero. Also in the examples shown in FIGS. 8 and 9, the minimum transmittance for P-polarized light can be made substantially zero by increasing the number of layers of the optical multilayer film and setting the number of layers to 27 or more. FIG. 10 shows an embodiment of the liquid crystal projector according to claim 17. A white lamp denoted by reference numeral 110 emits white light from a light source. The emitted light is reflected by a reflector 111, an ultraviolet component and an infrared component are cut by a filter 112, and a light beam diameter is reduced by a condenser lens system 113. The light beam whose light beam diameter has been reduced passes through the fly-eye lens 114, and passes through the lenticular lens 115 to the polarizing beam splitter array 116 and the half-wave plate 11.
7, the light enters the prism 120 via the lenticular lens 118 and the condensing lens 119, is totally reflected by the inclined surface, and enters the polarization beam splitter 121.

The linear polarization state realized by the half-wave plate 116 and the polarization beam splitter array 117 is set so that the polarization beam splitter 121 becomes S-polarized light. All the light beams incident from the polarization beam splitter 12
The light is reflected by 1 and enters the cross prism 100. The cross prism 100 is the same as that described with reference to FIG. 2 (Claim 15), and the optical multilayer film of the long-wavelength cutoff optical filter according to the first embodiment is used. The optical multilayer film of the second embodiment is used. The luminous flux incident on the cross prism 100 from the polarization beam splitter 121 is the S beam of each optical multilayer film.
The color component is separated according to the spectral transmittance characteristic of the polarized light, and the red component light enters the red liquid crystal display RD via the condenser lens 122. Similarly, the color-separated blue component light is passed through the condenser lens 123 to the blue liquid crystal display BD.
And the green component light enters the green liquid crystal display GD via the condenser lens 124. The red liquid crystal display RD, the blue liquid crystal display BD, and the green liquid crystal display GD display images of red, blue, and green image components, respectively. Since the liquid crystal display for each color is a reflection type, it reflects the incident light side. Each reflected light flux is 2 by each color image component.
In addition to being dimensionally modulated, the polarization plane is rotated 90 degrees by the polarization plane rotation effect of the liquid crystal display for each color, and becomes P-polarized light with respect to the cross prism 100 and the optical film of the polarization beam splitter. The reflected light flux of each color is incident on the cross prism 100, reflected and transmitted according to the spectral transmittance of each optical multilayer film in the cross prism 100 for P-polarized light, and color-combined, transmitted through the polarization beam splitter 121, and formed into an imaging optical system 200. To form a color image on a screen (not shown). As is apparent from the above description, the white lamp 11
0, reflector 111, filter 112, condenser lens system 113, fly-eye lens 114, lenticular lens 115, polarizing beam splitter array 116,
波長 wavelength plate 117, lenticular lens 118, condenser lens 119, prism 120, polarization beam splitter 121, cross prism 100, condenser lens 122,
Reference numerals 123 and 124 constitute "illuminating means for irradiating the liquid crystal display for each color with light". Also, the cross prism 100
Is used as a part of the “illumination unit” as described above, and is also used as a photosynthesis unit.

That is, the liquid crystal projector whose embodiment is shown in FIG. 10 includes a red liquid crystal display RD for displaying a red image component image, a blue liquid crystal display BD for displaying a blue image component image, and a green image display. A liquid crystal display GD for green for displaying an image of the component, illumination means 110 to 124, 100 for irradiating the liquid crystal display for each color with light;
A light combining means 100 for combining light spatially modulated by an image of each liquid crystal display as a single light flux, and an image forming apparatus for forming a color image by forming the light combined by the light combining means on a screen. Optical system 200
16. The liquid crystal projector according to claim 15, wherein the liquid crystal displays RD, BD, and GD for each color are of a reflection type.
The cross prism 100 described above is used as “a part of an illumination unit and a light combining unit”.
7). FIG. 11 schematically shows an embodiment of a liquid crystal projector according to the present invention. To avoid clutter,
The same reference numerals as those in FIG. 10 are used for those which do not seem to be confused. White lamp 11 as a light source
The light beam radiated from 0 is condensed by a condenser lens 113, and a polarizing optical system denoted by reference numeral 150 (FIG. 10).
Are similar to those of the fly-eye lens 114 to the condenser lens 119) and are incident on the cross prism 100. The linearly polarized light is S-polarized light with respect to the optical multilayer film of the cross prism 100. The cross prism 100 separates an incident light beam into red, blue, and green light beams. The red light is reflected by the mirrors M3 and M4 and the condenser lens 122.
And enters the transmissive red liquid crystal display RDT. The blue light enters the transmissive blue liquid crystal display BDT via M1 and M2 and the condenser lens 123. Also,
The green light is incident on the transmission type green liquid crystal display GDT via the condenser lens 124. Each liquid crystal display displays an image of a corresponding color image component, and two-dimensionally modulates transmitted light. The light beam transmitted through the liquid crystal display for each color enters the cross mirror 300. Cross mirror 300
Is described with reference to FIG. 3 (Claim 16). The three light beams that are incident are color-combined and emitted toward the imaging optical system 200. The imaging optical system 200 forms an incoming light beam as a “color image” on a screen (not shown).

That is, the liquid crystal projector of the embodiment shown in FIG. 11 has a red liquid crystal display RDT for displaying a red image component image, a blue liquid crystal display BDT for displaying a blue image component image, and a green image. A green liquid crystal display GDT for displaying component images, and illuminating means 110 to 113 and 15 for irradiating the liquid crystal display for each color with light.
0, M1 to M4, 122 to 124, light combining means 300 for combining light spatially modulated by the image of each liquid crystal display as a single light flux, and light combined by the light combining means on a screen. By imaging
A liquid crystal display RD for each color in a liquid crystal projector having an imaging optical system 200 for displaying a color image.
T, BDT, and GDT are transmission types, and the cross mirror 300 according to claim 16 is used as a light combining means (claim 18).

[0024]

As described above, according to the present invention, a novel long-wavelength cutoff optical filter, short-wavelength cutoff optical filter, cross prism, cross mirror, and liquid crystal projector can be realized. The long-wavelength cutoff optical filter and short-wavelength cutoff optical filter of the present invention have a small "difference in optical characteristics between S-polarized light and P-polarized light" as described above, and have a good blocking effect for each polarized light. The cross prism / cross mirror of the present invention can perform color separation and color synthesis well by combining the filter of the present invention. The liquid crystal projector of the present invention can perform good color image display by performing color separation and color synthesis using the cross mirror and the cross prism of the present invention.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a long wavelength cutoff optical filter and a short wavelength cutoff optical filter of the present invention.

FIG. 2 is a diagram for explaining a cross filter according to the present invention.

FIG. 3 is a diagram for explaining a cross mirror according to the present invention.

FIG. 4 is a diagram showing optical characteristics of an example of a long wavelength cutoff optical filter.

FIG. 5 is a diagram showing optical characteristics of an embodiment of a short wavelength cutoff optical filter.

FIG. 6 is a diagram showing optical characteristics of a comparative example of a long wavelength cutoff optical filter.

FIG. 7 is a diagram illustrating optical characteristics of a comparative example of the short wavelength cutoff optical filter.

FIG. 8 is a diagram showing optical characteristics of another comparative example of the long wavelength cutoff optical filter.

FIG. 9 is a diagram showing optical characteristics of another comparative example of the short wavelength cutoff optical filter.

FIG. 10 is a diagram showing one embodiment of a liquid crystal projector.

FIG. 11 is a diagram showing another embodiment of the liquid crystal projector.

FIG. 12 is a diagram illustrating optical characteristics of a conventional example of a long wavelength cutoff optical filter.

FIG. 13 is a diagram illustrating optical characteristics of a conventional example of a short wavelength cutoff optical filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Transparent substrate 20 Transparent substrate 30 Optical multilayer film 40 Adhesive layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H048 GA04 GA18 GA19 GA46 GA51 2H088 EA12 EA14 EA15 EA16 HA13 2H091 FA01X FA01Z FA07X FA07Z FA21X FA21Z FA41X FA41Z FB06 FD06 FD14 GA17 KA01 LA15 MA07

Claims (18)

[Claims] 1. An optical filter for blocking long-wavelength light, comprising at least an optical multilayer film and a pair of transparent substrates sandwiching the optical multilayer film. A long-wavelength cutoff optical filter, wherein at least one of the half-value wavelengths of the spectral transmittance for polarized light is in the range of 570 to 620 nm, and the difference between each half-value wavelength for the P-polarized light and the S-polarized light is 50 nm or less. 2. A long-wavelength cutoff optical filter according to claim 1, wherein a space between the pair of transparent substrates is an optical multilayer film comprising at least 27 optical films, and the optical multilayer film is adhered to the transparent substrate. 1. A long-wavelength cutoff optical filter comprising at least one adhesive layer. 3. The optical filter according to claim 2, wherein the adhesive layer has one layer, and the adhesive layer has a refractive index of 1.50 to 1.0.
52, the optical multilayer film has 37 layers, the first layer and the 37th layer have a refractive index of 1.62 to 1.64, and the second layer to the third layer have a refractive index of 1.62 to 1.64.
The even-numbered layer of the six layers has a refractive index of 1.70 to 2.1.
1, and the refractive index of the odd-numbered layer is 2.30 to
2. A long-wavelength cutoff optical filter, which is in the range of 2.50. 4. The optical filter according to claim 3, wherein the optical film thickness of the even-numbered layer in the optical multilayer film is d.
_2n (n = 1, 2, 3,... 18), n = 4 to 1
The same film thickness with respect to 5: When d _{8 to} d ₃₀ = 1, d ₂ =
0.25, d ₄ = 1.120, d ₆ = 1.08, d ₃₂ =
1.08, d ₃₄ = 1.120, a d ₃₆ = 0.25, the odd-numbered layer of thickness in the optical multilayer film: d
_{In 2n + 1} (n = 0, 1, 2, 3,... 18), n =
Same thickness for 3-15: When the _{d 7 ~d 31 = 1, d} 3 = 1.06, d 5 = 1.04, d 33 = 1.04,
A long-wavelength cutoff optical filter, wherein d ₃₅ = 1.06 and d ₁ and d ₃₇ are both 0.75 or less. 5. The long wavelength cutoff optical filter according to claim 4, wherein the pair of transparent substrates are formed of glass, the first layer and the 37th layer of the optical multilayer film are formed of Al ₂ O ₃ , The even-numbered layer among the layers to the 36th layer is La
A long-wavelength cut-off optical filter formed of ₂ O ₃ · 1.2 Al ₂ O ₃ , wherein the odd-numbered layers are formed of TiO ₂ . 6. The optical filter according to claim 5, wherein the optical film thickness of each layer of the optical multilayer film is 0.302λ with respect to the wavelength: λ = 400 nm. Second
Layer and the thirty-sixth layer have a .lambda.
077λ, the third layer and the 35th layer have a wavelength of λ = 600 n
0.328λ for m, the fourth and 34th layers are 0.346λ for wavelength: λ = 600 nm, and the fifth and 33rd layers are 0.321 for wavelength: λ = 600 nm.
λ, the sixth layer and the 32nd layer have a wavelength of λ = 600 nm, 0.334λ, and the seventh to 31st layers have a wavelength of λ = 60 nm.
A long-wavelength cutoff optical filter characterized by 0.309λ with respect to 0 nm. 7. The long-wavelength cutoff optical filter according to claim 1, wherein an incident angle to the optical multilayer film is set to approximately 45 degrees. 8. An optical filter for blocking short-wavelength light, comprising at least an optical multilayer film and a pair of transparent substrates sandwiching the optical multilayer film. A short-wavelength cutoff optical filter, wherein at least one of the half-value wavelengths of the spectral transmittance for polarized light is in the range of 485 to 530 nm, and the difference between each half-value wavelength for the P-polarized light and the S-polarized light is 50 nm or less. 9. The short-wavelength cutoff optical filter according to claim 8, wherein a space between the pair of transparent substrates is an optical multilayer film comprising at least 27 optical films, and the optical multilayer film is adhered to the transparent substrate. A short-wavelength cut-off optical filter comprising at least one adhesive layer. 10. The optical filter according to claim 9, wherein the adhesive layer has one adhesive layer, and the adhesive layer has a refractive index of 1.50 to 1.0.
52, the optical multilayer film has 37 layers, the first layer and the 37th layer have a refractive index of 1.62 to 1.64, and the second layer to the third layer have a refractive index of 1.62 to 1.64.
The odd-numbered layer of the six layers has a refractive index of 1.70 to 2.1.
1 and the refractive index of the even-numbered layer is 2.30 to
2. A short-wavelength cut-off optical filter, which is in the range of 2.50. 11. The optical filter according to claim 10, wherein the optical film thickness of the even-numbered layer in the optical multilayer film is d.
_2n (n = 1, 2, 3,... 18), n = 4 to 1
The same film thickness with respect to 5: When d _{8 to} d ₃₀ = 1, d ₂ =
_{0.5, d 4 = 0.92, d} 6 = 0.92, d 32 = 0.9
50, d ₃₄ = 1.0, d ₃₆ = 0.5, and the thickness of the odd-numbered layer in the optical multilayer film: d _{2n + 1} (n = 0,
1, 2, 3,. . 18), when the same film thickness for d = ₃ to 14: d _{7 to} d ₂₉ = 1, d ₃ = 1.0,
_{d 5 = 0.95, d 31 =} 0.92, d 33 = 0.92, d
_35. A short-wavelength cut-off optical filter, wherein ₃₅ = 1.0 and d ₁ and d ₃₇ are both 1.45 or more. 12. The short-wavelength cutoff optical filter according to claim 11, wherein the pair of transparent substrates is formed of glass, the first and 37th layers of the optical multilayer film are formed of Al ₂ O ₃ , The odd-numbered layer among the layers to the 36th layer is La
A short-wavelength cut-off optical filter formed of ₂ O ₃ · 1.2 Al ₂ O ₃ , wherein the even-numbered layers are formed of TiO ₂ . 13. The short-wavelength cutoff optical filter according to claim 12, wherein the optical film thickness of each layer of the optical multilayer film is 0.302λ with respect to the wavelength: λ = 700 nm. Second
Layer and the thirty-sixth layer have a wavelength of 0.4 mm for λ = 425 nm.
161λ, the third layer and the 35th layer have a wavelength of λ = 425n.
0.323λ for m, wavelength of the fourth layer: λ = 425n
0.297λ with respect to m, the wavelength of the 34th layer is λ = 425.
0.323λ with respect to nm, wavelength of the fifth layer: λ = 425
0.307λ with respect to nm, and the 33rd layer has a wavelength of λ = 42.
0.297λ for 5 nm, wavelength of the sixth layer: λ = 42
0.297λ for 5 nm, the 32nd layer has a wavelength: λ = 4
0.307λ for 25 nm, the 31st layer has a wavelength: λ =
A short-wavelength cutoff optical filter, wherein 0.297λ is applied to 425 nm, and the wavelength of the seventh to 30th layers is 0.323λ to 425 nm. 14. The short-wavelength cutoff optical filter according to claim 8, wherein an incident angle to the optical multilayer film is set to approximately 45 degrees. 15. The optical filter according to claim 7, wherein the transparent substrate is a prism, and the short-wavelength optical filter according to claim 14, wherein the transparent substrate is a prism. A cross prism that is combined in such a way that 16. The optical filter according to claim 7, wherein the transparent substrate is a prism, and the short-wavelength optical filter according to claim 14, wherein the transparent substrate is a prism. A cross mirror that is combined in such a way that 17. A liquid crystal display for red for displaying an image of a red image component, a liquid crystal display for blue for displaying an image of a blue image component, a liquid crystal display for green for displaying an image of a green image component, Illuminating means for irradiating the liquid crystal display with light, light combining means for combining light spatially modulated by the image of each liquid crystal display as a single light flux, and forming an image of the light combined by the light combining means on a screen. Thereby, in a liquid crystal projector having an image forming optical system for displaying a color image, the liquid crystal display for each color is of a reflection type, and the cross prism according to claim 15 is used as a part of an illumination unit and a light combining unit. A liquid crystal projector characterized by the above-mentioned. 18. A liquid crystal display for red for displaying an image of a red image component, a liquid crystal display for blue for displaying an image of a blue image component, a liquid crystal display for green for displaying an image of a green image component, Illuminating means for irradiating the liquid crystal display with light, light combining means for combining light spatially modulated by the image of each liquid crystal display as a single light flux, and forming an image of the light combined by the light combining means on a screen. A liquid crystal projector having an image forming optical system for displaying a color image, wherein the liquid crystal displays for the respective colors are transmissive, and wherein the cross mirror according to claim 16 is used as a light combining means. .