JP2000047102A - Reflection preventive film, lens, and projection television using the film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize reflection on the entire lens element by forming a multi- layered reflection preventive film of two-layered constitution which has a specific reflection factor. SOLUTION: The lens has the two-layered reflection preventive film, which has a reflection factor of <=1.0% to a light beam of specific wavelength made incident at a specific angle. The two-layered constitution has two kinds of different refractive index by, for example, SiO as the 1st layer and MgF2, etc., as the 2nd layer and the film thickness 28 and 29 are made optimum not to a light beam 26 which is made incident vertically on a lens element 9, but to a light beam 27 which is made incident at an angle θ approximately a quarter as large as the maximum incidence angle. This constitution minimize the incidence angle dependency and minimizes the reflection over the entire lens element surface. Because of the two-layered constitution, the base material and film are nearly equal in expansion and contraction difference due to a temperature difference and the stress applied to the film is reduced to suppress peeling and obtain high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer anti-reflection film for a lens element disposed, for example, in a projection lens for a projection television, and more particularly, to suppress reflection in a two-layer anti-reflection film to improve the contrast performance of a projection television. It is related to. Further, the present invention is not limited to the projection lens, and may include a lens having a multilayer antireflection film, a lens having a multilayer reflection film, and a multilayer reflection film of a lens element disposed on a lens (including a planar lens) which receives an enlarged incident light in a traveling direction of a light beam. The present invention relates to an optical device, an optical component, and the like using a lens having the same.

[0002]

2. Description of the Related Art A multilayer anti-reflection coating applied to a lens element of a projection lens in a projection television for enlarging and projecting an original image displayed on an image source such as a red, green and blue projection cathode ray tube onto a screen comprises: Conventionally, a vacuum evaporation method is applied to the surface of a lens element to maximize the anti-reflection effect with respect to light rays that are perpendicularly incident on the lens element.

Further, in order to minimize the incident angle dependence of the anti-reflection film, Japanese Patent Application Laid-Open Nos.
As disclosed in JP-A-121001, the most common multilayer antireflection film has a film configuration of three or more layers.

[0004] Japanese Patent Application Laid-Open No. 63-172201 discloses a two-layer antireflection film.
The gazette discloses that "the object is to provide a two-layer antireflection film having adhesion, heat resistance, and moisture resistance" and "in order from the glass and plastic substrate side, a first material having a higher refractive index than the substrate. A cerium oxide (CeO2) as a layer, and a SiOx (1 <x <2) as a second layer of a material having a lower refractive index than that of the substrate;
It states that "there is no change over time and the antireflection effect can be maintained for a long time."

[0005]

When an anti-reflection film having two or less layers is applied to a lens element of a projection lens of a projection television, the thickness of the anti-reflection film of the prior art is such that a light beam which is perpendicularly incident on the lens element. Is a film thickness that minimizes the reflectance of. According to this conventional anti-reflection film of a projection lens, the anti-reflection effect depends on the incident angle of the light beam, so that a lens element in which a light beam from a bright spot on an image display unit is disposed on the projection lens as in a projection television. In the case of an optical system that enters the lens element in a certain angle range, the reflectivity of the light beam obliquely incident on the lens element becomes higher than the reflectivity of the light beam incident perpendicularly. There is a problem that it cannot be obtained sufficiently. This problem has not been solved by the above-mentioned prior art.

[0006] The reflected light returns to the image display unit and shines other than the original image, so that the contrast is reduced.
As a result, there is a problem that the contrast in the set is reduced.

Further, in order to minimize the dependence of the angle of incidence on the antireflection film, the prior art requires a film configuration of three or more layers, which is costly, and the reliability of the film is low with respect to the temperature between the film layers. There is a problem that the difference becomes large and cracks and peeling occur due to the difference in the amount of contraction and expansion of the film when the temperature changes.

For this reason, even in the case of an optical system in which a light beam having an angle range is incident on the lens element, the reflectivity of the entire lens element is reduced by using an inexpensive and highly reliable two-layered antireflection film. It is an issue to suppress the light rays returning to the image display unit.

An object of the present invention is to solve the problem of the multilayer antireflection film in the lens element of the projection lens according to the prior art, and to suppress the reflectance of the entire lens element even when there is a light beam incident at an angle. An object of the present invention is to provide a two-layer antireflection film for preventing light returning to the image display unit and a projection lens for projection using the antireflection film to improve the contrast performance of the set.

The object of the present invention is not limited to an antireflection film of a projection television, but also suppresses the reflectance of a two-layer reflection film such as a lens used in another optical system and enhances the antireflection effect of the multilayer reflection film. It is in.

[0011]

According to the present invention, there is provided a lens having two layers of an anti-reflection film, wherein the anti-reflection film has a predetermined angle with respect to the anti-reflection film. The lens has a reflectance of 1.0% or less with respect to an incident light beam of a specific wavelength.

In order to achieve the above object, a multilayer antireflection film according to the present invention is a lens having two layers of antireflection films, wherein the antireflection films have a predetermined angle with respect to the antireflection films. The lens has a reflectance of 0.75% or less with respect to a light beam having a specific wavelength incident thereon.

According to another aspect of the present invention, there is provided a lens having a two-layer antireflection film, wherein the antireflection film is incident on the antireflection film at a predetermined angle. 0.5% reflectivity for light of wavelength
Lens.

Further, in order to achieve the above object, the multilayer antireflection film according to the present invention, in any one of the above lenses, sets the predetermined angle to be substantially 1 / the maximum incident angle to the lens. 4 angle.

In order to achieve the above-mentioned object, according to the present invention, in any one of the above-mentioned lenses, the predetermined angle is set to 1/6 or more of a maximum incident angle on the lens.
An angle within a range of / 3 or less.

In order to achieve the above object, according to the present invention, in any one of the above lenses, the predetermined angle is set to at least 1/12 of a maximum incident angle on the lens.
The angle is set to be within 3/8 or less.

In order to achieve the above object, according to the present invention, in any one of the above lenses, the first layer is formed of SiO (silicon monoxide) and the second layer is formed on the entire surface of the lens from the lens surface. Is composed of two layers of MgF2 (magnesium fluoride) having different refractive indices.

In order to achieve the above object, according to the present invention, in a lens having two layers of an antireflection film, the thickness of the antireflection film is set at a specific wavelength λ nm incident on the antireflection film. For light rays, it is in the range of (λ + 25) / 4 nm or more and (λ + 40) / 4 nm or less.

In order to achieve the above object, according to the present invention, in a lens having two layers of an antireflection film, the thickness of the antireflection film is a specific wavelength λ nm incident on the antireflection film. For light rays, it is in the range of (λ + 25) / 4 nm or more and (λ + 55) / 4 nm or less.

In order to achieve the above object, according to the present invention, in a lens having two layers of an antireflection film, the thickness of the antireflection film is set at a specific wavelength λ nm incident on the antireflection film. With respect to the light beam, the range is (λ + 15) / 4 nm or more and (λ + 90) / 4 nm or less.

In order to achieve the above object, the present invention provides a projection television having any one of the above-mentioned lenses, wherein the contrast can be set to 100 or more.

In order to achieve the above object, the present invention provides a projection television having any one of the above-mentioned lenses, which has a contrast of from 90 to 10.
It is assumed that the projection television can be set to a range of 0.

In order to achieve the above-mentioned object, the present invention provides a projection television having any one of the above-mentioned lenses, which has a contrast of from 80 to 10.
It is assumed that the projection television can be set to a range of 0.

In order to achieve the above object, according to the present invention, an original image displayed on a red, green, and blue image source is enlarged and projected on a screen. The thickness of the anti-reflection coating applied to the entire surface of the projection lens composed of a plurality of lenses arranged is a film that minimizes the reflectance for light rays incident at an angle that is not perpendicular to the anti-reflection coating. Thickness.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a projection optical system according to an embodiment using the present invention. Reference numeral 2 denotes a fluorescent surface of the projection tube 1, reference numeral 3 denotes a projection tube panel, reference numeral 5 denotes a bracket, and reference numeral 9 denotes a concave lens element. A refrigerant 4 is sealed in a space obtained by the projection tube panel 3, the bracket 5 and the concave lens element 9. Further, on the front surface of the concave lens element, the lens elements 10, 11, 12, 13, and 14 are arranged on the optical axis LL 'via the outer barrel while being held at a predetermined position of the inner barrel.

In such a configuration, light rays from the bright point P0 on the optical axis LL 'on the phosphor screen are applied to the lens elements 9, 10, 11, 12, 13, and 14 in the range from the upper limit light RAY1 to the lower limit light RAY2. Pass through.

FIG. 2 is a sectional view showing another ray path in the projection optical system of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 2, light rays from the luminescent spot P3 on the phosphor screen other than the optical axis LL 'are
At 1, 12, 13 and 14, it passes through the range from RAY13 to RAY14.

The lens elements in the projection lens of the projection optical system shown in FIGS. 1 and 2 include, for example, SiO on the first layer and MgF2 on the second layer in order from the lens element side.
A multilayer antireflection film having a two-layer structure having different types of refractive indices has a maximum antireflection effect with respect to a wavelength of a light beam incident at an angle of about ４ of a maximum incident angle in a light beam range incident on each lens element. Each layer is formed so as to have a film thickness of (incident light wavelength / 4). here,
The incident light wavelengths are wavelengths λRmax, λBmax, λGmax indicating peak energies of spectral distributions in respective image lights obtained by the respective red, blue, and green projection tubes.
And the thickness of the antireflection film can be set according to each wavelength. FIG. 16 shows a configuration diagram of the lens element taking the lens element 9 as an example.

In FIG. 16, reference numeral 24 denotes a first layer anti-reflection film of the lens element 9; 25, a second layer anti-reflection film;
8 is the thickness of the antireflection film 24, 29 is the antireflection film 2
5. Here, the film thicknesses 28 and 29 are not set to the optimum film thickness for the light beam 26 perpendicularly incident on the lens element 9 but for the light beam 27 incident at an angle θ of about １ ／ of the maximum incident angle. To an optimum film thickness.

According to such a configuration, the incident angle dependence can be minimized even in a two-layer antireflection film, so that the reflection over the entire surface of the lens element can be minimized.

The emission spectrum distribution of the phosphor corresponding to red, green and blue of the projection tube 1 in the configuration of FIG. 1 will be described. FIG. 7 shows a characteristic diagram of the emission spectrum distribution of the phosphor in the green projection tube 1. The vertical axis indicates relative energy (%) and the horizontal axis indicates wavelength λ (nm).

As shown in FIG. 7, the emission spectrum of the green phosphor has a spurious component (sub-peak λGSmax wavelength) existing in the short wavelength (blue) side wavelength region with respect to the main wavelength λGmax showing the peak energy near 545 nm. 4
95 nm) and spurious components (sub-peaks of 590 nm and λGLmax6
30 nm).

FIG. 8 is a characteristic diagram showing the emission spectrum distribution of the phosphor in the red projection tube 1. The vertical axis indicates relative energy (%), and the horizontal axis indicates wavelength λ (nm). The emission spectrum shows a spurious component (sub-peak λRSmax wavelength 585n) that is present in the vicinity of 580 nm to 600 nm, which is a wavelength region on the short wavelength (green) side, with respect to the main wavelength component showing a peak energy near 612 nm.
m) and a spurious component (sub-peak λRLmax wavelength 63) near 630 nm which is a wavelength region on the long wavelength (red) side.
5 nm).

Similarly, the emission spectrum distribution of the phosphor used in the blue projection tube has the characteristic of showing a mountain-shaped broad peak with a peak at the main wavelength of 460 nm.

Among the light beams emitted from the respective projection tubes 1 having the above characteristic wavelengths, the wavelength of the light beam at which the effect of the antireflection film is maximized is obliquely incident with respect to the light beam which is perpendicularly incident on the lens element. Light beam shifts in the short wavelength direction. Specifically, taking the case of the green phosphor as an example, when a light beam having a dominant wavelength (545 nm) is vertically incident, the light beam is incident at an angle on an antireflection film formed with an optimum film thickness (545/4 nm). Then, the wavelength at which the antireflection effect is maximized is 54.
The wavelength becomes shorter than 5 nm, and the reflection effect at the main wavelength cannot be sufficiently obtained. Therefore, in order to obtain the best anti-reflection effect when the light of the main wavelength of each phosphor is obliquely incident, the amount of shift of the wavelength is considered in advance to optimize the light of the main wavelength when the light is obliquely incident. Therefore, the thickness of each layer of the antireflection film needs to be set thicker.

In the projection optical system according to the first embodiment shown in FIG. 1, since the maximum incident angle on each lens element is about 60 degrees, the antireflection film is about 1 /
The film thickness was optimal for a light beam incident at 15 degrees, which is an incident angle of 4. Here, the numerical value of 1/4 of the maximum incident angle is an optimum value obtained from the simulation result of the reflected light design of the projection television, but is a value close to 1/4 or a value that does not approximate to 1/4. Even so, the present invention is within a range in which equivalent effects can be obtained. In the first embodiment, an optimal case will be described.

Here, the shift amount of the light beam incident at 15 degrees with respect to the vertical incidence is about 30 nm in the short wavelength direction from the experiment, so that in the case of the red phosphor, the main wavelength (610 n) is used.
The film thickness of each layer was set to 640/4 nm in consideration of the shift amount at an incident angle of 15 degrees with respect to m). That is, 640 nm
An anti-reflection film is formed which has a characteristic that the reflectance becomes minimum when the light beam is incident vertically.

Similarly, in the case of a green phosphor, the dominant wavelength (5
The thickness was set to 575/4 nm in each layer in consideration of the shift amount at the time of incidence of 15 degrees with respect to 45 nm). That is, 57
An anti-reflection film having a characteristic that the reflectance becomes minimum when a light beam of 5 nm is vertically incident is formed.

Further, similarly, in the case of a blue phosphor, the thickness of each layer was set to 480/4 nm in consideration of the shift amount at the time of incidence of 15 degrees with respect to the main wavelength (450 nm). That is,
An anti-reflection film having a characteristic that the reflectance becomes minimum when a light beam of 480 nm is vertically incident is formed.

According to the multilayer antireflection film having such a structure, reflection at the lens element can be suppressed to the minimum.

The relationship between the projection tube 1 where the effect appears most and the lens element 9 closest thereto will be described in detail as an example.

FIG. 3 shows a ray tracing diagram from the bright spot P0 at the center of the phosphor screen 2 to the lens element 9 in the above configuration.

As shown in FIG. 3, the light beam at the luminance point P0 at the center of the fluorescent screen 2 is applied to the lens element 19 from RAY5 to RAY6.
Incident in the range of Light rays having an incident angle in the range of RAY1 to RAY2 are transmitted without being reflected by the lens element 19,
Rays at incident angles in the range from RAY5 to RAY2 and RAY2 to RAY6 are transmitted light (RAY3 and RAY4) and reflected light (RAY3 'and RAY3).
4 '), but has the effect of reducing the energy of the reflected light.

FIG. 4 shows a first example of a ray tracing diagram from the point other than the bright spot at the center of the fluorescent screen 2 to the lens element 9 in the above configuration.

FIG. 4 shows a case where the luminescent spot P2 is located at about 0.2 from the center when the diagonal distance from the center of the phosphor screen 2 is 1.0. At this time, the light beam at the luminance point P2 enters the lens element 19 in the range from RAY11 to RAY12. At this time, light rays in the range of RAY7 to RAY8 are transmitted without being reflected by the lens element 9, and light rays in the range of RAY7 to RAY11 and RAY8 to RAY12 are transmitted light (RAY9 and RY8).
AY10) and reflected light (RAY9 ′ and RAY10 ′) are generated, but there is an effect of reducing the energy of the reflected light.

FIG. 5 shows a second example of a ray tracing diagram from the point other than the bright spot at the center of the phosphor screen 2 to the lens element 9 in the above configuration.

FIG. 5 shows a case where the bright spot P3 is located at about 0.5 from the center when the diagonal distance from the center of the phosphor screen 2 is 1.0. At this time, the light beam at the luminance point P3 enters the lens element 9 in the range from RAY16 to RAY18. In this case, light rays in the range from RAY13 to RAY14 are transmitted without being reflected by the lens element 1. RAY13 to RAY17
Light rays in the range from RAY14 to RAY18 are transmitted light (RAY15
RAY16) and reflected light (RAY15 ′ and RAY16 ′), but has the effect of reducing the energy of the reflected light.

FIG. 6 shows a third example of a ray tracing diagram from the point other than the bright spot at the center of the fluorescent screen 2 to the lens element 9 in the above configuration.

FIG. 6 shows a case where the bright spot P4 is located at about 0.9 from the center when the diagonal distance from the center of the phosphor screen 2 is 1.0. At this time, the light beam at the luminance point P4 enters the lens element 9 in the range from RAY21 to RAY22. In this case, the light rays in the range from RAY13 to RAY14 are transmitted without being reflected by the lens element 9. RAY13 to RAY17
Light rays in the range from RAY14 to RAY18 are transmitted light (RAY15
RAY16) and reflected light (RAY15 'and RAY16') are generated, but there is an effect of suppressing the energy of the reflected light.

According to the above-described antireflection effect, there is an effect of suppressing the energy of the light reflected by the lens element at all the bright spots on the fluorescent screen 2. That is, since the energy returning to the fluorescent screen 2 can be reduced, the contrast of the original image and the set of the fluorescent screen 2 can be improved.

In the first embodiment, the incident angle is set to 1
The optimum film thickness of the anti-reflection film in the case of 5 degrees has been described. However, the same effect can be obtained as long as the angle is close to 1/4 of the maximum incident angle to the lens element. A range within which equivalent effects can be obtained is within the scope of the present invention.

Next, as a second embodiment of the present invention, a case will be described below in which two types of antireflection films, a V coat antireflection film and a U coat antireflection film, are used. Second
Also in the embodiment, a case will be described in which the maximum incidence angle of the light beam on the lens element is set to 60 degrees and the reflectance is optimal for the light beam of a specific wavelength whose incident angle is 15 degrees.

FIG. 9 shows the characteristics of one embodiment of the V coat antireflection film corresponding to red. On the horizontal axis is the wavelength of the incident light (n
m), and the vertical axis indicates the reflectance (%) for a vertically incident light beam.

As shown in FIG. 9, the V coat having the reflectance characteristic of the condition (1) after the shift is formed on the graph of the condition (2) having the reflectance characteristic under the condition before the shift. It becomes optimal when the light of the main wavelength is incident at 15 degrees in the red phosphor, and the effect of the antireflection film of the present invention can be obtained.

FIG. 10 shows the characteristics of one embodiment of the V coat antireflection film corresponding to green.

The horizontal axis shows the wavelength (nm) of the incident light, and the vertical axis shows the reflectance (%).

As shown in FIG. 10, a V coat having the reflectance characteristic of the condition (1) after the shift is formed on the graph of the condition (2) having the reflectance characteristic under the condition before the shift. This is optimal when the light of the main wavelength is incident at 15 degrees in the green phosphor, and the effect of the antireflection film of the present invention can be obtained.

FIG. 11 shows the characteristics of one embodiment of the U-coat antireflection film corresponding to red.

The horizontal axis shows the wavelength (nm) of the incident light, and the vertical axis shows the reflectance (%).

As shown in FIG. 11, the U-coat having the reflectance characteristic of the condition (1) after the shift is formed on the graph of the condition (2) having the reflectance characteristic under the condition before the shift. This is optimal when the light of the main wavelength enters the red phosphor at 15 degrees, and the effect of the antireflection film of the present invention can be obtained.

FIG. 12 shows the characteristics of one embodiment of the U-coat antireflection film corresponding to green.

The horizontal axis shows the wavelength (nm) of the incident light, and the vertical axis shows the reflectance (%).

As shown in FIG. 12, the U coat having the reflectance characteristic of the condition (1) after the shift is formed on the graph of the condition (2) having the reflectance characteristic under the condition before the shift. It is optimal for a green phosphor, and the effect of the antireflection film of the present invention can be obtained.

In the above description of the first and second embodiments, it has been described that the film thickness is optimum for an incident angle of １ ／ of the maximum incident angle. Alternatively, even in a range that does not approximate １ ／, the same effect of reducing the reflectance can be obtained. The details will be described with reference to the graph of FIG. 17 showing the relationship between the incident angle of light rays and the reflectance.

FIG. 17 is a graph showing the relationship between the incident angle θ and the reflectance when a conventional anti-reflection film (two layers) having an optimum film thickness for vertically incident light is used. On the other hand, the graph is a relationship diagram between the incident angle θ and the reflectance when an antireflection film (two layers) having an optimum film thickness is used for a light beam with an incident angle of 15 degrees. From comparison of these two graphs, it is understood that the dependency of the incident angle on the antireflection effect is lower when the antireflection film having the optimum thickness in consideration of the incident angle is used. Further, from the viewpoint of the antireflection effect, the conditions for setting the optimum thickness of the antireflection film are 1 /
The same effect is obtained not only in the case of 4 (θ = 15) but also in the range of 1/6 to 1/3 (10 <θ <20).
It is considered that even in the range of / 12 to 3/8 (5 <θ <22.5), it is possible to obtain the effect of the reflectance similar to that in the above range.

Further, in the first and second embodiments, the shift amount when the anti-reflection film is set to the optimum film thickness is described as 30 nm. However, the same reflectance reduction is possible when the shift amount is in the range of 25 nm to 40 nm. And the shift amount is from 25 nm to 5
The same effect can be obtained even in the range of 5 nm. Further, even in the range of 15 nm to 90 nm, a similar effect can be obtained as compared with the case of three or more layers (see FIG. 14).

Next, FIG. 13 shows the reflectance characteristics when green light is incident on the number of film layers (two layers and three layers).
The horizontal axis shows the wavelength (nm) of the incident light, and the vertical axis shows the reflectance (%).

FIG. 13 shows the reflectance when the anti-reflection film is composed of three layers (coat 1) and when the anti-reflection film is composed of two layers (coat 2). It is understood that the reflectance of the coat 1 becomes flat with respect to the wavelength by increasing the number of films. On the other hand, the coat 2 of the present invention has an optimum reflectivity for a light beam having a shifted wavelength in consideration of the incident angle, and has an effect comparable to the reflectivity effect of the coat 1 with a simpler film configuration than the coat 1. It is possible to get.

Next, when comparing the reflectance of a lens element having two layers of antireflection films, it was found that the reflectance was 1% in the antireflection film having the optimum film thickness in the case of normal incidence. In consideration of the incident angles described in the first and second embodiments, the antireflection film under a certain vapor deposition condition is reduced by 0.67%, which is 33% lower than the conventional one.
Although the above results were obtained in this experiment, the reflectance can be further reduced to 0.5% or less by adjusting the deposition conditions of the antireflection film.

The contrast was 69 in the case of using a two-layer lens element when the film thickness was optimum for normal incidence, whereas the contrast of the lens of the first and second embodiments was improved. When the element was used, it was 101, and the result was improved by 30% as compared with the conventional case.

Here, the value of 2 in consideration of the incident angle of the present invention is used.
FIG. 14 shows the effect of contrast in a projection television using a lens element having a layered anti-reflection film, taking green as an example. In FIG. 14, the horizontal axis indicates the film thickness ×
4 (nm), the vertical axis is contrast.

FIG. 14 shows that when the shift amount is 25 nm to 40 nm, the contrast exceeds 100, and it is possible to obtain an image with the best contrast.

When the shift amount is 25 nm to 55 nm, the contrast is close to 100, and an effect comparable to the optimum range can be obtained. Further, the shift amount is 15 nm to 9
Even in the case of 0 nm, the contrast can be maintained at 90 or more.

The evaluation method is as follows.
The reflectance is measured by a reflectance measuring device (Hitachi's U-321 spectrophotometer)
0) was actually measured and evaluated. Regarding the contrast, an evaluation pattern was transferred to a projection tube and measured and evaluated.

FIG. 15 shows a contrast evaluation pattern. As shown in FIG. 15, a band of 1/5 of the width w is alternately displayed in white and black on the phosphor screen, and the center w / 25 of the center white band is displayed.
In addition, the luminance of the black band w / 25 on both sides was measured, and the luminance ratio between the two was determined to evaluate.

As a method of measuring the film thickness, in addition to the method of measuring with a film thickness measuring device, the transmittance is optimized when the light beam is incident while changing the wavelength of the light beam. There is a method of calculating theoretically by taking a correlation with the film thickness to be formed.

Further, since the antireflection film of the present invention has a two-layer structure, the difference in expansion and contraction due to the temperature difference between the substrate and the film is almost equal, so that the stress applied to the film is reduced. Peeling or the like can be suppressed, and a highly reliable antireflection film can be obtained.

In the above embodiment, the case where the lens element of the present invention is used for a projection television has been described. However, the present invention is not limited to the projection television.
Even when the lens element of the present invention is used for other optical devices, glasses, goggles, and the like, a similar effect can be obtained in terms of antireflection.

[0081]

As described above, according to the present invention, 2
The anti-reflection effect of the lens can also be improved by the anti-reflection film having a layer structure. In particular, the above-described multilayer anti-reflection film having the two-layer structure is applied to the lens element disposed on the projection lens for a projection television. This has an effect of minimizing reflection on the entire surface of the lens element. In addition, since light rays returning from the lens element to the phosphor screen are reduced, a projection television equipped with a projection lens using the same also has an effect of improving contrast performance.

Further, two kinds of substances (for example, SiO and MgF)
Because of the two-layer configuration according to 2), there is an effect that the reliability is high and can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a projection optical system and a ray path according to an embodiment using the present invention.

FIG. 2 is a sectional view showing another ray path in a projection optical system using the present invention.

FIG. 3 is a ray tracing diagram from a bright spot at the center of a phosphor screen to a lens element.

FIG. 4 is a first example of a ray tracing diagram from a point other than the bright spot at the center of the phosphor screen to the lens element 1;

FIG. 5 is a second example of a ray tracing diagram from a point other than the bright spot at the center of the phosphor screen to the lens element 1.

FIG. 6 is a third example of a ray tracing diagram from a point other than the bright spot at the center of the phosphor screen to the lens element 1.

FIG. 7: Emission spectrum distribution of green phosphor

FIG. 8: Emission spectrum distribution of red phosphor

FIG. 9 is a characteristic diagram of one embodiment of a V coat antireflection film corresponding to red.

FIG. 10 is a characteristic diagram of one embodiment of a V coat antireflection film corresponding to green.

FIG. 11 is a characteristic diagram of one embodiment of a U-coated antireflection film corresponding to red.

FIG. 12 is a characteristic diagram of one embodiment of a U-coat antireflection film corresponding to green.

FIG. 13 is a graph showing the reflectance characteristics of the number of film components in the case of green.

FIG. 14 is a diagram showing the relationship between film thickness and contrast in the case of green.

FIG. 15 is an evaluation pattern diagram of contrast.

FIG. 16 is a configuration diagram in which two layers of antireflection films are provided on a lens element.

FIG. 17 is a graph showing the dependence of the antireflection effect on the incident angle.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Projection tube, 2 ... Fluorescent surface, 3 ... Face panel, 4 ... Refrigerant, 5 ... Bracket, 6 ... Hold down fitting, 7 ... Inner barrel 8 ... Outer barrel, 9 ... Lens element, 10 ... Lens element 11 ... Lens element, 12 ... Lens element, 1
3 ... Lens element, 14 ... Lens element, P
0, P1, P2, P3, P4: Bright point RAY11, RAY7, RAY13, RAY19: Upper limit light, RAY2, R
AY8, RAY14, RAY20: Lower limit light, LL ': Optical axis RAY3, RAY3', RAY5, RAY4, RAY4'RAY6, RAY
9, RAY9 ', RAY11, RAY10, RAY10', RAY11
2, RAY115, RAY15 ', RAY17, RAY16, RAY16
', RAY18, RAY21, RAY22 ... ray path, 23 ... incident angle θ, 24 ... first layer antireflection film, 25 ... second layer antireflection film, 26 ... vertically incident light ray, 27 ... incident angle The light ray of θ, 28: thickness of the first layer, 29: thickness of the second layer

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazunari Nakagawa 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Within the Visual Information Media Division of Hitachi, Ltd. (72) Inventor Seiji Okamoto Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa No. 292 F-term (Reference) 2H087 KA07 PA06 PA17 PB06 QA01 QA18 2K009 AA05 CC03

Claims (14)

[Claims] 1. A lens having two layers of an antireflection film, wherein the antireflection film has a reflectance of 1.0 with respect to a light beam of a specific wavelength incident on the antireflection film at a predetermined angle. %. 2. A lens having two layers of an antireflection film, wherein the antireflection film has a reflectance of 0.75 with respect to a light beam of a specific wavelength incident on the antireflection film at a predetermined angle. %. 3. A lens having two layers of an anti-reflection film, wherein the anti-reflection film has a reflectance of 0.5 with respect to a light of a specific wavelength incident on the anti-reflection film at a predetermined angle. %. 4. The lens according to claim 1, wherein the predetermined angle is substantially one-fourth of a maximum incident angle on the lens. lens. 5. The lens according to claim 1, wherein the predetermined angle is set to an angle within a range of ６ to １ ／ of a maximum incident angle to the lens. A lens characterized in that: 6. The lens according to claim 1, wherein the predetermined angle is set to an angle within a range from 1/12 to ／ of a maximum incident angle to the lens. A lens characterized in that: 7. The lens according to claim 1, wherein the first surface of the lens has a first surface extending from the lens surface.
A lens comprising a two-layer film having two different refractive indexes of SiO (silicon monoxide) and a second layer of MgF2 (magnesium fluoride). 8. A lens having two antireflection films, wherein the thickness of the antireflection film is (λ + 25) / 4 with respect to a light beam having a specific wavelength λnm incident on the antireflection film.
A lens characterized by being in the range of not less than nm and not more than (λ + 40) / 4 nm. 9. A lens having two antireflection films, wherein the thickness of the antireflection film is (λ + 25) / 4 with respect to a light beam having a specific wavelength λnm incident on the antireflection film.
A lens characterized by being in the range of not less than nm and not more than (λ + 55) / 4 nm. 10. A lens having two antireflection films, wherein the thickness of the antireflection film is (λ + 15) / 4 with respect to a light beam having a specific wavelength λnm incident on the antireflection film.
A lens characterized by being in the range of not less than nm and not more than (λ + 90) / 4 nm. 11. A projection television having a lens according to any one of claims 1 to 10,
A projection television, wherein the contrast can be set to 100 or more. 12. A projection television having the lens according to claim 1.
A projection television, wherein the contrast can be set in a range of 90 to 100. 13. A projection television having the lens according to claim 1.
A projection television, wherein the contrast can be set in a range of 80 to 100. 14. A projection lens comprising a plurality of lenses disposed in front of an image source used in a projection television for enlarging and projecting an original image displayed on a red, green and blue image source onto a screen. An anti-reflection film, wherein the anti-reflection film applied to the entire surface of the lens has a thickness that minimizes the reflectance with respect to light rays incident at an angle that is not perpendicular to the anti-reflection film.