JPH0743528A - Filter device - Google Patents

Abstract

PURPOSE:To provide such a filter device that shields a photosensitive material from light entering at an angle except for a specified incident angle and that the light after transmitted through the filter has a certain wavelength. CONSTITUTION:This filter device consists of two narrow band interference filters 1, 3 on the surfaces of a transparent glass substrate 5 facing to each other. These filters 1, 3 have substantially same peak wavelength in the transmission spectra for light entering at a specified incident angle and have different peak shift in the spectrum for light entering at an angle different from the specified angle. Since peaks in the transmission spectra of the two filters 1, 3 for light entering at a specified incident angle are equal to each other, light entering perpendicularly to the filter device transmits through the filter device. Since peaks of transmission spectra of these narrow band interference filters 1, 3 for light entering at an angle except for the specified angle are different from each other, light incident to the filter device at an angle except for the specified angle can not transmit through the filter device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter device for selecting and transmitting synthetic light from a light source.

[0002]

2. Description of the Related Art For example, when the content of an original image for each color formed on a lith film is projected onto a color photosensitive material having a spectral sensitivity for exposure, the wavelength of illumination light is also selected corresponding to the original image for each color. There is a need. In this case, for example, a white light source and a narrow band interference filter are used to select the exposure wavelength. By arranging and using a narrow band interference filter between the light source and the photosensitive material, it is possible to select the light of a specific wavelength that reaches the photosensitive material from the light source.

When a narrow band interference filter is used in an exposure apparatus, the filter optical thin film is often designed on the basis of a required transmission spectrum for light that is vertically incident on the filter. If there is only vertical light incident on the filter in the exposure apparatus, this is not a problem, but if there is light obliquely incident on the filter, the oblique incident light has a transmission spectrum different from the design, The oblique transmission spectrum includes wavelengths shorter than the vertical transmission spectrum. Further, if it is a bandpass filter, light with a shorter wave than designed will be transmitted.

[0004]

When the photosensitive material has a spectral sensitivity and the respective sensitivity wavelengths are close to each other, the above constitution has the following problems. Of the light incident on the filter to select the specific wavelength for exposing the specific photosensitive layer, the vertically incident light passes through the specific photosensitive layer without changing the wavelength and exposes the specific photosensitive layer. The incident light has a wavelength slightly shorter than the specific wavelength after being obliquely transmitted, and the light having the short wavelength exposes the photosensitive layers having other close sensitivities. Therefore, when a specific photosensitive layer is exposed by the exposure device, the light obliquely incident on and transmitted through the filter undesirably exposes the other photosensitive layer, resulting in exposure crosstalk and accurate exposure. However, there is a problem that the image reproducibility is deteriorated.

An object of the present invention is to solve the above-mentioned conventional problems, and to provide a filter device in which light incident on the filter at angles other than a specific angle is blocked against the photosensitive material and the wavelength after passing through the filter becomes constant. To provide.

[0006]

The above object of the present invention can be achieved by the following constitutions. (1) A plurality of narrow-band interference filters having a plurality of narrow-band interference filters having substantially equal peak wavelengths of a spectrum incident and transmitted at a specific angle and different peak shift amounts of a spectrum incident and transmitted at an angle different from the specific angle. A filter device which is layered on a substrate transparent to the peak wavelength which is incident and transmitted at an angle.

(2) The plurality of narrow-band interference filters having substantially the same peak wavelengths of the vertically incident and transmitted spectra and different peak shift amounts of the obliquely incident and transmitted spectra are vertically incident and transmitted. A filter device that is layered on a substrate that is transparent to the peak wavelength.

In order to layer a plurality of narrow band interference filters on a substrate, they may be layered on opposite sides of the substrate or may be layered on one side of the substrate. Further, at least one narrow band interference filter may be layered on a plurality of substrates, and these may be further stacked. The larger the number of layered narrow band interference filters having different peak shift amounts, the greater the selective transmission effect of the target wavelength.

FIG. 1 shows transmission spectra of two narrow band interference filters. In Fig. 1, the horizontal axis represents wavelength (nm)
The vertical axis represents the transmittance (%). The transmission spectrum (a) of the vertically incident light and the transmission spectrum (b) of the obliquely incident light in the two narrow-band interference filters are shown as examples of specific incident angles.

As shown in (a), the peak of the spectrum vertically incident on and transmitted through the two narrow band interference filters is x.
Lights that are equal in nm, and thus are vertically incident on a filter device in which two narrow band interference filters are stacked, pass through the filter device as they are, and the combined spectrum does not change.

As shown in (b), the obliquely incident light has its peak of the spectrum vertically incident and transmitted shifted to the short wavelength direction. Since the narrow band interference filters have different peak shift amounts at the same oblique incident angle, the wavelength obliquely incident on one of the filters is yn.
m, and the wavelength that obliquely enters the other filter and transmits is znm, and ynm and znm are not equal. Therefore, the light of ynm obliquely transmitted through one filter obliquely enters the other filter. However, it does not pass through the other filter.

Therefore, the combined spectrum of the light obliquely incident on and transmitted through these two filters is close to zero, and the light obliquely incident on the filter device is blocked without passing through the filter device. Thus, the filter device is capable of transmitting light that is vertically incident and blocking light that is obliquely incident, but by designing the filter device on the basis of light that is incident at a specific angle that is not vertical, It is also possible to transmit light that is incident at a specific angle that is not vertical and block light that is incident at an angle that is different from this specific angle.

That is, a plurality of narrow-band interference filters in which the peak wavelengths of the spectrums incident and transmitted at a specific angle other than the vertical incidence are substantially equal, and the peak wavelengths of the spectra incident and transmitted at an angle different from the specific angle are different. By configuring the filter device using, it is possible to select and transmit specific obliquely incident light. For example,
This configuration corresponds to the case where the narrow band interference filter is arranged on the two substrates and the two substrates are arranged not in parallel to form the filter device. Further, for example, even when the narrow-band interference filters are arranged on both opposing surfaces of the substrate, the configuration in which the opposing both surfaces of the substrate are not parallel but wedge-shaped corresponds to the above configuration.

As the narrow band interference filter in the present invention, for example, a filter having a structure in which a plurality of oxide thin films and fluoride thin films are laminated and which causes light interference can be used. Further, as the narrow band interference filter, a filter in which a plurality of liquid crystal cells are laminated and an electric field is applied to each liquid crystal cell to refract light to cause interference can be used.

In the present invention, that the peak wavelengths are substantially equal means that the peak wavelength difference is within ± 2%. If the peak wavelengths are substantially equal, the vertically incident light of the same wavelength can pass through the plurality of narrow band interference filters. If the difference between the peak shift amounts of the plurality of narrow band interference filters is small, the half-value width of the peak of the transmitted light becomes low. Therefore, it is preferable that the difference between the peak shift amounts is large. The difference in peak shift amount is preferably 2% or more at 60 °.

In designing a plurality of narrow band interference filters, the peak wavelengths of the spectrums incident and transmitted at a specific angle are substantially equal, and the peak shift amounts of the spectrums incident and transmitted at an angle different from the specific angle are different. First, the target wavelength that becomes the peak wavelength of the transmission spectrum is set.
Then, based on the target wavelength, a plurality of refraction layers that cause interference due to refraction are designed. In the design of the refraction layer,
The number of layers, the material of the layers, and the thickness of the layers are designed based on the target wavelength. The refractive layers have different refractive indexes, and high refractive index layers and low refractive index layers are alternately laminated. The refractive index of each refraction layer is set according to the material and the thickness, which is a known method ("Optical thin film" by HAMacleod, published by Nikkan Kogyo Shimbun,
1989, pp. 47-51). To perform this calculation, for example Soft
ware Spectra, Inc. (USA) software TFCalc (Thin Film
Calculations) can be used.

The thickness of each layer is a value around m times λ / 4n of the target wavelength (n is the refractive index of the material, and m is a positive integer). As the number of layers increases, the half-width of the spectrum also decreases, and as the number of layers increases, the interference filter has a narrow band. Further, as the number of layers increases, the peak shift amount with respect to the incident angle increases.

Examples of materials used as the refraction layer and the refractive indexes when using the same are shown below. Low Refractive Material Calcium Fluoride Refractive Index 1.2〜
1.3 Silicon Oxide Refractive Index 1.4-2.0 Aluminum Oxide Refractive Index 1.5-1.7 Magnesium Fluoride Refractive Index 1.3-1.4 High Refractive Material Hafnium Dioxide Refractive Index 2.0-
2.1 Tantalum pentoxide Refractive index 2.1-2.2 Titanium dioxide Refractive index 2.2-2.7 Zirconium dioxide Refractive index 2.0-2.1 In addition, the said refractive index is a film-forming method, film-forming. It changes depending on the conditions and the wavelength. The above materials are merely examples, and other materials having the same function can be used.

[0019]

If the peaks of the transmission spectra of the light incident at the specific angles of the plurality of narrow band interference filters are substantially equal, the light corresponding to the peak wavelengths is transmitted by being incident at the specific angle. In addition, the spectrum peak of the light that is incident and transmitted at an angle different from this specific angle is different for each narrow band interference filter, so the light that is incident on and transmitted through the first narrow band interference filter at an angle different from the specific angle is , It cannot pass through the next narrow band interference filter. Therefore, the filter device can surely block the light incident at an angle different from the specific angle and surely transmit only the target wavelength incident at the specific angle. Since crosstalk between different photosensitive layers is prevented when the exposure is carried out in (1), accurate exposure can be carried out without the other photosensitive layers being fuzzed.

The filter device of the present invention is effective for exposing a light-sensitive material having the above-mentioned spectral sensitivity, but it can be used in any way as a filter for transmitting only incident light of a specific angle such as vertical incidence. It is possible. Further, by using such a filter device arranged between the diffusion surface light source and the condenser lens, it is possible to selectively transmit the light from the surface light source and condense it in a substantially point shape.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The filter device has a multilayer structure shown in FIG. The narrow band interference filters 1 and 3 are provided on both surfaces of the transparent glass substrate 5, that is, on the incident side surface and the output side surface. First narrow band interference filter (hereinafter referred to as the first filter) 1
1 is shown in Table 1, and the configuration of the second narrow band interference filter (hereinafter referred to as the second filter) 3 is shown in Table 2.

[0022]

[Table 1]

[0023]

[Table 2]

First filter 1 and second filter 3
Both have a nine-layer structure. The first layer, the third layer, the fifth layer, the seventh layer, and the ninth layer are made of titanium oxide so as to have a high refractive index. The second layer, the fourth layer, the sixth layer, and the eighth layer are made of magnesium fluoride so as to have a low refractive index. Thickness of each layer and Q
The WOT (1/4 wavelength optical film thickness) is as shown as a result as a result of being optimized for transmitting the target wavelength. In the above table, the first layer is on the glass substrate side, and this is the same in the following tables.

FIG. 3 shows the spectral transmittance of the vertically incident light of the first filter 1, and FIG. 4 shows the spectral transmittance of the vertically incident light of the second filter 3. The spectral transmittance of the first filter 1 has a peak at 400 nm. The spectral transmittance of the second filter 3 is 359 nm, 380 nm, 400 nm, 428n.
There is a peak at m. Since the two filters 1 and 3 have a peak at 400 nm for vertically incident light,
It is possible to transmit m vertically incident light. However, since the first filter 1 has no peak other than 400 nm,
The first filter 1 does not transmit light other than the vertically incident wavelength in the vicinity of 400 nm, and therefore, the vertically incident wavelength other than in the vicinity of 400 nm does not reach the second filter 3. Therefore, even if the second filter 3 has a peak other than 400 nm, vertically incident light other than near 400 nm is not emitted from the emission side of the second filter 3.

FIGS. 5, 6 and 7 show two filters 1, 3
FIG. 5 shows the angle dependence of the combined spectrum in a filter device having the transparent glass substrate 5 on both sides. FIG. 5 shows an incident angle of 0 ° (normal incidence), FIG. 6 shows an incident angle of 15 °, and FIG. 7 shows an incident angle of 30 °. Is the spectrum at. As shown in FIG. 5, the transmission spectrum of vertically incident light has peaks at wavelengths of 400 nm and 320 nm, and the transmittance at wavelength 400 nm is close to 90%.

As shown in FIG. 6, the transmission spectrum of light obliquely incident at 15 ° has wavelengths of 390 nm and 310 nm.
Has a peak at 1 and a peak at a wavelength shorter than that of vertically incident light is 1
The wavelength shifts about 0 nm, and the transmittance is 40 at the wavelength of 390 nm.
%, Which is a large decrease.

As shown in FIG. 7, the transmission spectrum of the light obliquely incident at 30 ° has a large peak with a transmittance of a little over 50% at a wavelength of 310 nm, but has almost no peak at other wavelengths. Therefore, when a photosensitive material having a spectral sensitivity of wavelength 400 nm and its vicinity is exposed by synthetic light, the wavelength of 400 n can be obtained by arranging the filter device having the above configuration between the light source emitting the synthetic light and the photosensitive material.
Only the photosensitive layer sensitive to m can be accurately exposed.

In the above case, the wavelength is 300 nm to 320.
An unnecessary wavelength peak occurs around nm. In some cases, this unnecessary wavelength peak may adversely affect the intended processing such as exposure of the photosensitive material. Therefore, in order to eliminate the influence of the peak of the unnecessary wavelength, another filter that transmits the light of the target wavelength and cuts the light of the unnecessary wavelength may be arranged and used together between the light source and the filter device. preferable. For this kind of filter,
For example, a bandpass filter can be used. In this case, since it is necessary to transmit the target wavelength even for obliquely incident light, a filter having a half width wider than that of the filter device is suitable for this purpose. Further, in order to block unnecessary wavelengths, it may be more appropriate to use a light absorption type filter.

Next, a filter device in which the number of layers of the filters 1 and 3 is increased to 13 will be described. Table 3 shows the configuration of the first filter 1, and Table 4 shows the configuration of the second filter 3.

[0031]

[Table 3]

[0032]

[Table 4]

First filter 1 and second filter 3
Are both 13-layered. 1st layer, 3rd layer, 5th layer,
The seventh layer, the ninth layer, the eleventh layer, and the thirteenth layer are made of titanium oxide so as to have a high refractive index. 2nd layer, 4th layer, 6th
The layer, the eighth layer, is made of magnesium fluoride so as to have a low refractive index. The thickness of each layer and QWOT (1/4 wavelength optical film thickness) are optimized to transmit the target wavelength,
It is exactly as shown.

The transmission spectral characteristics of this filter device depending on the incident angle are shown in FIGS. As shown in FIG. 8, the spectrum width was slightly wider for the vertically incident light. Further, as shown in FIGS. 9 and 10, it can be seen that the transmittance of the peak wavelength is lowered with respect to the obliquely incident light, and the blocking property with respect to the obliquely incident light is good. Also in the case of this filter device, since there are unnecessary peaks around the wavelengths of 300 nm to 340 nm, the wavelength of 3 nm may be set as necessary in the same manner as described above.
It is preferable to also use a filter that blocks light of 00 nm to 340 nm.

[0035]

According to the present invention, a filter device in which two filters having an incident angle dependency and different peak shift amounts are laminated transmits only light incident at a specific angle, and an angle different from the specific angle. Does not transmit the light incident at.
Therefore, since the light transmitted through the filter device has a constant wavelength, the photosensitive material having the spectral sensitivity is prevented from being clogged with other layers during the exposure with the light having the predetermined wavelength, thereby preventing the color mixture. The photosensitive material can be exposed with good reproducibility.

[Brief description of drawings]

FIG. 1 is a graph showing transmittance distributions of two narrow band interference filters.

FIG. 2 is a cross-sectional view of a filter device.

FIG. 3 is a graph showing a transmission spectrum of a first narrow band interference filter.

FIG. 4 is a graph showing a transmission spectrum of a second narrow band interference filter.

FIG. 5 is a graph showing a transmission spectrum of vertically incident light in the filter device according to the present invention.

FIG. 6 is a graph showing a transmission spectrum of light obliquely incident at 15 ° in the filter device according to the present invention.

FIG. 7 is a graph showing a transmission spectrum of light obliquely incident at 30 ° in the filter device according to the present invention.

FIG. 8 is a graph showing a transmission spectrum of vertically incident light in another filter device according to the present invention.

FIG. 9 is a graph showing a transmission spectrum of light obliquely incident at 15 ° in another filter device according to the present invention.

FIG. 10 is a graph showing a transmission spectrum of light obliquely incident at 30 ° in another filter device according to the present invention.

[Explanation of symbols]

 1 1st narrow band interference filter 3 2nd narrow band interference filter 5 Transparent glass substrate

Claims (2)

[Claims] 1. A plurality of narrow-band interference filters having substantially the same peak wavelengths of spectra that are incident and transmitted at a specific angle and different peak shift amounts of spectra that are incident and transmitted at an angle different from the specific angle. A filter device which is layered on a substrate transparent to the peak wavelength which is incident and transmitted at the specific angle. 2. The plurality of narrow-band interference filters having substantially the same peak wavelengths of vertically incident and transmitted spectra and different peak shift amounts of obliquely incident and transmitted spectra, wherein the peaks are vertically incident and transmitted. A filter device that is layered on a substrate that is transparent to wavelengths.