JPH0915045A - Liquid crystal filter - Google Patents

Abstract

PURPOSE: To obtain a sharp wavelength peak and high resolution by forming a incident part from which a reflecting film is removed on the reflection film of a liquid crystal filter incident side board, and constituting so as to introduce the incident light on the incident part in the direction inclined to a cell normal. CONSTITUTION: A filter cell 1 has an incident side board 4 and an emitting side board 12 having reflecting films 3, 11 formed on the one side surfaces of glass boards 1, 10 and disposed mutially oppositedly the films 3, 11, and a liquid crystal 13 filled between the films 3 and 11. At this time, the film 3 of the board 4 is formed to have an incident part 5 from which the film 3 is removed in a spot manner, and so constituted that the incident light J0 is incident on the part 5 in the direction inclined at an angle θ from a cell normal (a). Thus, even if the reflectivities R1 , R0 of the films 3, 11 formed on the boars 4, 12 are increased, high permeability and high finesss can be obtained without reducing the incoident light amount into the cell 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal filter device applicable as a resonance / transmission filter of a specific wavelength in an optical multiplexing system.

[0002]

2. Description of the Related Art A liquid crystal filter device of this type is conventionally known as a liquid crystal etalon having a Fabry-Perot structure.

A filter cell 100 of such a liquid crystal filter device has glass substrates 101 and 1 as shown in FIG.
An incident-side substrate 103 and an outgoing-side substrate 112, each of which has reflective films 102 and 111 formed on one side surface of the substrate 10,
The reflective films 102 and 111 are arranged so as to face each other, and the liquid crystal 120 is filled between the reflective films 102 and 111. The incident light J ₀ is introduced into the filter cell 100 through the incident side substrate 103. The light is made incident and is repeatedly reflected in the cell, and only the wavelength corresponding to the resonance optical path length nd is emitted as resonance transmitted light J _T out of the filter cell via the emission side substrate 112.

At this time, the transmission wavelength characteristic of the liquid crystal filter device largely depends on the respective reflectances of the reflective films 102 and 111 formed on the substrates 103 and 112, respectively.
Therefore, the reflective films 102 and 111 are formed of the same material so that the respective reflectances R ₁ and R ₀ are equal (R ₁ = R ₀ ). If R ₁ > R ₀ ,
The initial reflected light J ₁ at the time of incidence becomes large, and conversely R ₁ <R ₀
In this case, the ratio of the light reflected by the reflection film 102 is reduced, and the transmitted light to the incident side substrate 103 is increased. Therefore, when the incident side substrate 1 is repeatedly reflected due to resonance,
The resonance reflected light J _R as the total sum of the transmitted light to the light source 03 is increased, and the resonance transmitted light J _T as the total sum of the light transmitted to the emission side substrate 112 is reduced accordingly, and the light loss is anyway. This is because it will become large. On the contrary, R
_{When 1} = R ₀ , the same amount of light is repeatedly reflected between the reflective films 102 and 111, and the loss of light can be suppressed.

On the other hand, in the transmission wavelength characteristic of the liquid crystal filter device, the resonance wavelength peak becomes sharper and the resolution becomes higher as the reflectances R ₀ and R ₁ become higher.

That is, the half width ε representing the transmission wavelength characteristic
Is inversely proportional to the magnitude of the reflectance, and as shown in FIG. 8, the reflectance (b) having a high reflectance is narrower than the reflectance (a) having a low reflectance, and the resonance wavelength peak becomes sharp. There is.
Further, the finesse F indicating the resolution is a ratio (F = 2π) between the distance between adjacent wavelengths (free spectral region) 2π and the half width ε.
/ Ε), and the larger this value, the larger the resolution. Therefore, the reflectances R ₁ and R of the reflection films 102 and 111 formed on the substrates 103 and 112, respectively.
_The higher ₀ is, the sharper the wavelength peak becomes, and the resolution of the liquid crystal filter device can be increased.

However, in such a state, the substrates 101, 1
The flatness (roughness) of 10 and the parallelism between the substrates 101 and 110 can be obtained only in the ideal state. In reality, such an ideal state is impossible, and the reflectances R ₁ and R _The initial reflected light J ₁ increases as ₀ increases (see FIG. 7).
This causes a loss of wavelength peak.

Therefore, conventionally, a measure has been taken to increase the number of reflecting mirrors without increasing the reflectance R ₁ (R ₀ ) of the reflecting film 102 (111) (Japanese Patent Laid-Open No. 6-90045).
No.).

That is, as shown in FIG. 9B, the filter cell 130 of this liquid crystal filter device has the same structure as the conventional filter cell 100 shown in FIG. 9B (FIG. 9A) but with the incident side substrate 103 and the outgoing side substrate. 112 glass substrates 101
1 and a dielectric coating 1 on the other side, respectively.
04 and 113 are applied. The dielectric coating 104 (113) is preferably formed of zirconium dioxide, titanium dioxide, zinc sulfide, a zinc selenium compound or a mixture thereof, and is provided on the side opposite to the reflective films 102 and 111 as shown in FIG. 9 (b). The resonance transmitted light J _T is increased by suppressing the reflected lights J ₂ and J ₃ (see FIG. 9A) reflected by the surface of the filter cell 1.
The loss of the wavelength peak of 30 can be suppressed, and the resolution of the liquid crystal filter device can be further improved.

In FIGS. 7 and 9, the incident angle of light is drawn at an angle so that the optical path can be seen, but in reality, θ = 0 °, and resonance occurs at the same portion.

[0011]

However, the filter cell 130 is such that the dielectric coatings 104 and 113 suppress only the reflected lights J ₂ and J _{3 which} are reflected by the surface on the side opposite to the reflective films 102 and 111. Therefore, it still has the initial reflected light J ₁ , and therefore the resonance transmitted light J _T cannot be sufficiently increased, and the resolution cannot be improved as expected.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a liquid crystal filter device having a sharp wavelength peak and high resolution.

[0013]

In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that an incident side substrate and an outgoing side substrate, each of which has a reflecting film formed on one side surface of a glass substrate, are subjected to the reflection. The films are arranged so as to face each other, and a liquid crystal is filled between the reflective films to form a filter cell,
A liquid crystal filter device in which incident light is made incident on the inside of the filter cell via the incident side substrate, and only wavelengths corresponding to the resonance optical path length in the cell are made to emerge outside the filter cell via the emission side substrate. In the above, in the case where the incident film is formed on the reflecting film of the incident side substrate by removing the reflective film, and the incident light is incident on the incident unit from a direction inclined with respect to the cell normal. It has a feature.

According to a second aspect of the present invention, there is provided the liquid crystal filter device according to the first aspect, wherein the reflecting film on the incident side substrate is one.
It is characterized by being formed from a 00% specular reflector.

According to a third aspect of the present invention, there is provided the liquid crystal filter device according to the first or second aspect, wherein the incident light is focused on the incident portion by an optical component, and It is characterized in that the incident portion is formed in a circular pin point that matches the converging shape.

[0016] Further, the invention according to claim 4 is the invention according to claim 1.
4. The liquid crystal filter device according to any one of items 1 to 3, wherein a dielectric coating is applied on the other side surface of the glass substrate that constitutes each of the incident side substrate and the emission side substrate. .

[0017]

Since the invention according to claims 1 to 4 has the above-mentioned structure, it has the following effect.

That is, according to the first aspect of the present invention, since the incident light is made incident on the incident portion where the reflection film is removed from the direction inclined with respect to the cell normal, it is generated by the reflection film at the time of incidence. The initial reflected light of the incident light is suppressed, the amount of incident light into the filter cell becomes substantially equal to the amount of the incident light, and once the light that has entered the filter cell does not return to the incident part within the cell. Only wavelengths corresponding to the resonance optical path length are resonated and emitted out of the filter cell via the emission side substrate.

Therefore, according to the first aspect of the invention, even if the reflectance of each reflection film formed on the incident side substrate and the emission side substrate is increased, the amount of incident light into the cell is not reduced, and the wavelength peak is reduced. Therefore, the reflectance can be increased to achieve high transmittance and high finesse.

According to the second aspect of the present invention, since the reflection film of the incident side substrate is formed of a 100% specular reflector, the light once entering the filter cell is formed on the incident side substrate without passing through the incident side substrate. Resonance occurs between the reflected film and the reflective film formed on the emission side substrate, and only the wavelength corresponding to the optical path length is emitted outside the cell via the emission side substrate.
In this way, all the light that has entered the cell is emitted to the outside of the cell via the emission side substrate, so even if the reflectance of the reflection film of the emission side substrate is increased, the emission side substrate Although the amount of light that passes through is reduced, the resonance transmitted light, which is the sum of the transmitted light to the emission side substrate calculated as an infinite series, increases, and high transmittance and high finesse can be achieved.

Further, according to the third aspect of the invention, the incident light is condensed by the optical component, and is made incident on the inside of the cell from the incident portion formed at the circular pin point matching the converging shape. The incident light can be efficiently incident into the cell with little loss due to reflection.

Further, according to the invention of claim 4, since the other side surface of the glass substrate constituting each of the incident side substrate and the emission side substrate is provided with a dielectric coating, the outer surface of the cell is covered with this dielectric coating. The loss of incident light that is going to enter the cell and transmitted light that is going to go out of the cell due to reflection on the outer surface of the cell is suppressed.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described based on illustrated embodiments.

1 to 3 show a liquid crystal filter device as a first embodiment. As shown in FIG. 2, the filter cell 1 of this liquid crystal filter device includes an incident side substrate 4 and an emission side substrate 12 each having a reflective film 3 and 11 formed on one side surface of a glass substrate 2 and 10, respectively. The reflective films 3 and 11 are arranged to face each other, and the liquid crystal 13 is filled between the reflective films 3 and 11.

At this time, the reflecting film 3 of the incident side substrate 4 is formed to have the incident portion 5 with the reflecting film 3 removed spotwise, and the incident light J ₀ is angled with respect to the cell normal a. The light is incident on the incident portion 5 from a direction inclined by θ.

The reflective films 3 and 11 are formed on the glass substrates 2 and 1, respectively.
It is formed by stacking metal oxides on the surface of No. 0 by the vapor deposition method. Particularly, the reflection film 3 of the incident side substrate 4 is easily formed according to the manufacturing process shown in FIG. 4, for example.

That is, first, the glass substrate 2 for the incident side substrate 4 is prepared (step a), and the reflection film 3 of this glass substrate 2 is prepared.
The mask material 7 is coated on the formation surface of (step b).
Next, the mask material 7 is etched to leave the mask material 7 only at the site where the incident portion 5 is formed (step c), and then the reflective film 3 is coated by vapor deposition (step d). After that, the reflective film 3 at the site can be removed together with the residual mask material 7 to form the reflective film 3 having the incident portion 5 (step e). The incident portion 5 formed in this manner is used for the incident light J
It can be formed into a shape that matches the projected shape of ₀ .

In this embodiment, the incident light J ₀ is condensed by using an optical component 6 such as a microlens or a collimator lens and is made incident on the inside of the cell from the incident portion 5.
In this way, when the incident light J ₀ is condensed by the optical component 6 on the incident part 5, the incident part 5 is formed in a circular pinpoint that matches the converging shape of the incident light J ₀ (see FIG. 3).

Further, the inclination angle θ of the incident light J _{0 from} the cell normal a is set so that the light J _LC (see FIG. 1) once incident on the cell does not return to the incident portion 5, 0 ° <
It is appropriately set within the range of θ <θ _C (critical angle for total reflection).

The liquid crystal cell device of the first embodiment thus configured, as shown in FIG. 1, the incident light J ₀ is the optical component 6
The light is focused on the incident part 5 and is incident on the inside of the cell from the incident part 5. For this reason, the initial reflected light J ₁ (FIG. 7) of the incident light J ₀ by the reflection film 102 generated in the conventional device is generated.
(See reference) is suppressed and the light J _LC entering the filter cell 1
Of the incident light J ₀ is substantially the same as that of the incident light J ₀ without decreasing, and the light J _LC once incident into the filter cell 1 resonates between the reflection films 3 and 11 without returning to the incident portion 5.
Only the wavelength corresponding to the resonance optical path length nd is emitted to the outside of the filter cell 1 via the emission side substrate 12.

At this time, the resonance reflected light J _R as the sum of the transmitted light returning to the incident side substrate 4 due to resonance and the emission side substrate 12
The resonance transmitted light J _T as the total sum of the transmitted light transmitted through is calculated as an infinite series, and the resonance reflected light J _R and the resonance transmitted light J _T become equal, and the initial reflected light J ₁ (see FIG. 7) The transmittance can be increased because there is no loss due to the occurrence of.

Therefore, in the liquid crystal filter device of the first embodiment, even if the reflectances R ₁ and R ₀ of the respective reflection films 3 and 11 formed on the incident side substrate 4 and the emission side substrate 12 are increased, the inside of the cell 1 is reduced. Since the amount of incident light on the light is not reduced and the wavelength peak is not lost, the reflectance R ₁ and R ₀ can be increased to achieve high transmittance and high finesse, resulting in a sharp wavelength peak. , The resolution is improved.

FIG. 5 shows a liquid crystal filter device as a second embodiment. Filter cell 20 of this liquid crystal filter device
Is different in that the reflection film 8 of the incident side substrate 9 is formed of a 100% specular reflector, and the other structure is the same as that of the filter cell 1 described above.

The reflective film 8 is formed by laminating a metal such as Au or Ag on the surface of the glass substrate 2 by vapor deposition or plating.

According to this filter cell 20, the light which once enters the filter 20 through the incident part 5 is reflected by the reflection film 8 and is not transmitted to the incident side substrate 9 side, and has a resonance optical path length nd. Since only the corresponding wavelength passes through the reflection film 11 and escapes only to the exit side substrate 12 side, the resonance transmitted light J _T becomes twice as large as that of the filter cell 1 described above. Therefore, sufficient transmitted light can be obtained even if the reflectance R ₀ of the reflection film 11 of the emission side substrate 12 is increased. That is, the reflective film 1
When the reflectance R _{0 of} 1 is increased, the amount of light transmitted through the reflective film 11 decreases with each reflection, but the resonance transmitted light J _T as the sum of transmitted light calculated as an infinite series increases.

Therefore, in the liquid crystal filter device of the second embodiment, the reflectance R ₀ of the reflection film 11 can be increased to achieve high transmittance and high finesse, resulting in a sharp wavelength peak and improved resolution. Becomes

FIG. 7 shows a filter cell 30 used in a liquid crystal filter device as a third embodiment. The filter cell 30 includes the reflection films 3 and 1 of the glass substrates 2 and 10 constituting the incident side substrate 16 and the emitting side substrate 18, respectively.
Dielectric coating 1 on the other side opposite to 1
5 and 17 are different, and the other structure is the same as that of the filter cell 1 described above.

The dielectric coatings 15 and 17 are formed of, for example, zirconium dioxide, titanium dioxide, zinc sulfide, zinc selenium compounds or mixtures thereof.

According to the filter cell 30, the dielectric coatings 15 and 17 reflect the incident light J ₀ and the resonant transmitted light J _T on the other side surfaces of the glass substrates 2 and 10 (reflected light of FIG. 9A). Since the light loss due to (corresponding to J ₂ and J ₃ ) is suppressed, the amount of incident light and the amount of transmitted light can be increased, and the resolution is further improved.

The filter cell 30 of the third embodiment is also used.
The reflection film 3 of the incident side substrate 16 can also be composed of the 100% specular reflector used in the filter cell 20 described above, and in this case also, the resolution is further improved.

[0041]

As described above in detail, the present invention has the following effects. That is, according to the first aspect of the invention, even if the reflectance of each reflection film formed on the incident side substrate and the emission side substrate is increased, the amount of incident light into the cell is not reduced, and the wavelength peak loss is reduced. Therefore, it is possible to increase the reflectance to achieve high transmittance and high finesse, and as a result, it is possible to provide a liquid crystal filter device having a sharp wavelength peak and high resolution.

According to the second aspect of the present invention, since all the light that has entered the cell is emitted to the outside of the cell through the emission side substrate, the reflectance of the reflection film of the emission side substrate is high. In this case, the amount of light transmitted through the emission side substrate decreases with each reflection, but the resonance transmitted light increases as the sum of the transmitted light to the emission side substrate calculated as an infinite series, resulting in high transmittance and high finesse. As a result, in addition to the effect of the invention described in claim 1, it is possible to provide a liquid crystal filter device having a sharper wavelength peak and a higher resolution.

According to the third aspect of the invention, the incident light is condensed by the optical component so that the incident light is incident on the cell meat from the incident portion formed at the circular pin point matching the converging shape. Therefore, the incident light can be efficiently incident into the cell in a state where the loss due to reflection is small, and as a result, in addition to the effect of the invention according to claim 1 or 2, a high resolution liquid crystal filter device having an improved incidence rate. Can be provided.

Further, according to the invention described in claim 4, since the dielectric coating is applied to the other side surface of the glass substrate constituting the incident side substrate and the emitting side substrate respectively, the outer surface of the cell is covered by this dielectric coating. Loss due to reflection on the outer surface of the cell of the incident light trying to enter the cell and the transmitted light going out of the cell is suppressed,
As a result, in addition to the effect of the invention described in any one of claims 1 to 3, it is possible to provide a high-resolution liquid crystal filter device in which the incident rate and the transmittance are further improved.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of light transmission in a cell of a liquid crystal filter device as a first embodiment.

FIG. 2 is a partial cross-sectional view of a filter cell of the liquid crystal filter device of FIG.

FIG. 3 is a plan view of a main part of the filter cell of FIG.

FIG. 4 is a schematic explanatory diagram of a manufacturing process of a reflective film of the filter cell of FIG.

FIG. 5 is a conceptual diagram of light transmission in a cell of a liquid crystal filter device as a second embodiment.

FIG. 6 is a partial cross-sectional view of a filter cell of a liquid crystal filter device as a third embodiment.

FIG. 7 is a conceptual diagram of light transmission in a cell of a conventional liquid crystal filter device.

FIG. 8 shows a transmission spectrum of a general liquid crystal filter device, (a) is a transmission spectrum diagram when a reflectance of a reflection film is low, and (b) is a transmission spectrum diagram when a reflectance of the reflection film is high. Is.

FIG. 9 is a conceptual diagram of light transmission of a conventional liquid crystal filter device, in which (a) is one without a dielectric coating,
(B) shows each with a dielectric coating.

[Explanation of symbols]

1,20,30 Filter cell 2,10 Glass substrate 3,8 Reflective film (incident side substrate) 4,9,16 Incident side substrate 5 Incident part 6 Optical component 11 Reflective film (exit side substrate) 12,18 Emission Side substrate 13 Liquid crystal 15 Dielectric coating (for incident side substrate) 17 Dielectric coating (for outgoing side substrate) a Cell normal line J ₀ Incident light nd Resonance optical path length

Claims (4)

[Claims] 1. An entrance-side substrate and an exit-side substrate each having a reflective film formed on one side surface of a glass substrate are arranged such that the reflective films face each other, and a liquid crystal is filled between the reflective films. A filter cell is configured to allow incident light to enter the filter cell via the incident side substrate, and only the wavelength corresponding to the resonant optical path length in the cell is passed through the exit side substrate to the outside of the filter cell. In the liquid crystal filter device configured to emit light to the incident side substrate, an incident portion is formed by removing the reflection film on the reflection film of the incident side substrate, and the incident light is incident from a direction inclined with respect to a cell normal line. A liquid crystal filter device, characterized in that the liquid crystal filter device is made to enter the part. 2. The liquid crystal filter device according to claim 1, wherein the reflection film of the incident side substrate is formed of a 100% specular reflector. 3. The liquid crystal filter device according to claim 1, wherein the incident light is configured to be condensed on the incident portion by an optical component, and the incident portion has the condensing shape. A liquid crystal filter device, characterized in that the liquid crystal filter device is formed in a matching circular pinpoint. 4. The liquid crystal filter device according to claim 1, wherein a dielectric coating is provided on the other side surface of the glass substrate that constitutes each of the incident side substrate and the emission side substrate. A liquid crystal filter device characterized by being provided.