JPS6038682B2 - trimming filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a trimming filter having comb-shaped transmission characteristics in the visible range.

Conventionally, in frequency-separated single-tube color television cameras, the transmission characteristics of the dye used in the stripe filter for music, green (G), and red (R) overlap each other in their respective peripheral wavelength regions. Therefore, it is not possible to strictly separate the incident light into blue, green, and red. That is, even the light that has passed through the green region of the stripe filter contains a slight light component in the blue or red region, so the color reproducibility cannot necessarily be said to be good.
Conventionally, an attempt was made to improve color reproducibility by layering a trimming filter with a color separation stripe filter, such as "Optical System of a Single-Tube Color Film Camera," Television, Reijaku No. 2, No. 1, 1972. .

This relates to the color reproducibility of color films, and in particular, a trimming filter has been disclosed that makes light in the green region have characteristics close to a line spectrum. The shape of this trimming filter is as follows, assuming that the input o is the design wavelength.
It is formed by sandwiching the layer with school caps on both sides.

As described above, the ideal trimming filters shown in the past have a spectrum close to the line spectrum, and the transmitting region is also in the green wavelength band. On the contrary,
A trimming filter for normal color photography needs to have a sufficiently wide transmission band in order to transmit light in each wavelength band (R, G, B) in terms of light quantity.

Also, a filter is required that can efficiently separate the light beams of each wavelength band using a single filter. An object of the present invention is to provide a trimming filter having characteristics that meet such requirements.

In the trimming filter according to the present invention, the design wavelength (reference wavelength) that exists between 40° and 70° is omitted.
In contrast, by making each layer constituting the filter basically have an optical thickness of 0, the components of the incident light can be absorbed into the blue band, green band, and red band. A separating trimming filter is obtained.

The optical thickness of each layer constituting the filter is determined by the basic film thickness theory described above. Between 5% and 5%, that is, 0^. X・-
o5 and blank. X. If it is between 95 and 95, it can be used for practical purposes.

In the trimming filter according to the present invention, the light components of each band are separated by having a valley of transmittance, or in other words, a peak of reflectance, near the 48th point and the spot. However, the value of the transmittance valley can be controlled to a desired value by adjusting the refractive index of the material constituting each layer or the number of layers. In view of the number of layers constituting the trimming filter, in order to satisfy the color separation characteristics and to facilitate manufacturing, it is appropriate that the number of layers is from 3 to 7 layers. In order to make the transmittance trough 70% or less with this number of layers, the refractive index ratio of the high refractive index layer and the intermediate refractive index layer used in the trimming filter is 1.4 or more, and the refractive index ratio of the intermediate refractive index layer is 1.4 or higher. The refractive index ratio of the low refractive index layer is 1
．． 05 or higher is desirable. In addition, here, high refractive index is 1
．． 8 or more, low refractive index refers to 1.5 or less, and the remaining 1.8
A refractive index between and 1.5 is defined as an intermediate refractive index. In the trimming filter according to the present invention, if the film thickness of the above-mentioned structure is taken, alternate layers of high refractive index layers and intermediate refractive index layers, alternate layers of high refractive index layers and low refractive index layers, or intermediate refractive index layers can be obtained. It may be an alternating layer of a high refractive index layer and a low refractive index layer, or an alternating layer including a high refractive index layer, an intermediate refractive index layer, and a low refractive index layer.

When the trimming filter according to the present invention is applied to a single-tube color television camera using a color separation filter, the wavelength band that is most harmful in light quantity among the wavelength band portions that overlap with the stripe filter is removed. By blocking light, the S/N ratio and color reproducibility are improved.

The present invention will be explained in detail below. Figures 1 and 2 are
FIG. 1 is a diagram showing the configuration of a trimming filter according to the present invention, which will be described later. FIG. 1 shows a case of three layers, and FIG. 2 shows a case of five layers.

In the figure, ni is the refractive index of the i-th layer measured from the substrate S, di is the geometric thickness of the i-th layer, ns is the refractive index of the substrate, and the ratio is the external layer in contact with the outermost layer. is the refractive index of the medium. FIG. 3 shows the first trimming filter according to the present invention.
This is a diagram showing the transmittance characteristic curve of the example, and the vertical axis is the transmittance T (
%), and the wavelength (nm) is taken as the axis.

The method of preparing the koji in the characteristic curve diagram shown below is the same as that shown in FIG. The film structure corresponding to the characteristic curve shown in FIG. 3 is a three-layer structure as shown in FIG. 1, and the data are shown in Table 1. Table 1 As shown in Table 1, from the substrate side (ratio=1.52), a first layer consisting of Z2 as a high refractive index film, a second layer mainly composed of Si02 as a low refractive index layer, Furthermore, it is composed of a third layer made of AI2Q as an intermediate refractive index film, and the optical thickness of each layer is 130 Kagawa.

Since the standard wavelength input is 52 degrees, the trimming filter is set at 0. It is formed of alternating layers having an optical thickness of . As shown in FIG. 3, a comb-shaped trimming filter is obtained which has a transmittance of 70% in the vicinity of 48 mm and 58 mm, and has a transmittance of 90% to 100% in the other visible wavelength bands. FIG. 4 is a diagram showing a transmittance characteristic curve of a second embodiment of the trimming filter according to the present invention.

The film structure for the characteristic curve shown in FIG. 4 is a three-layer structure as shown in FIG. 1, and the data are shown in Table 2. Table 2 As shown in Table 2, from the substrate (ratio=1.52), the first layer consisting of 2 of Z as a high refractive index film and S as a low refractive index film.
The second layer mainly composed of i02, Z2 as a high refractive index film.
The optical film layer of each layer is 130 layers.

Since the reference wavelength (0) is 52 mm, the trimming filter is formed of alternating layers having an optical thickness of 0 (open) and 0 (in). As shown in Figure 4, there is a trough with a transmittance of 50% near the 47th and 58th points, and in the other visible regions, there is a valley with a transmittance of 50%.
A comb-shaped trimming filter having a transmittance of 0% or more is obtained. FIG. 5 is a diagram showing a transmittance characteristic curve of a third embodiment of the trimming filter according to the present invention.

The film structure for the characteristic curve shown in FIG. 5 is a five-layer structure as shown in FIG. 2, and the data are shown in Table 3. Table 3 As shown in Table 3, from the substrate (ratio: 1.52), a layer consisting of 2 of Z as a high refractive index layer is added to the first layer, third layer and fifth layer.
a second layer of a tank made of MgF2 as a low refractive index layer;
and a configuration arranged in the fifth layer.

The standard wavelength input is 52 mark skin, so all trimming is included. It is formed from alternating layers having a film thickness of .

As shown in FIG. 5, a comb-shaped trimming filter is obtained that has valleys with a transmittance of approximately 20% near the 48th and 58th edges, and has a transmittance of approximately 90% or more in other regions. FIG. 6 is a diagram showing a transmittance characteristic curve of a fourth embodiment of the trimming filter according to the present invention.

The membrane structure for the characteristic curve shown in FIG. 6 is a five-layer structure as shown in FIG. 2, and Table 4 shows the data. Table 4 No. 4
As shown in the table, the first
AI203 is used as an intermediate refractive index film in the third layer and the fifth layer.
In the second and fourth layers, a layer in which M is 2 is arranged as a low refractive index film.

Since the reference wavelength is 52 degrees, the trimming filter is formed of alternating layers having an optical thickness of 0. As shown in Fig. 6, a comb-shaped trimming filter has a trough with a transmittance of 70% near the 47th and 58th wavelength bands, and a transmittance of around 95% in the other visible wavelength bands. can get. FIG. 7 is a diagram showing a transmittance characteristic curve of a fifth embodiment of the trimming filter according to the present invention. The film structure corresponding to the characteristic curve shown in FIG. 7 is a three-layer structure as shown in FIG. 1, and the data are shown in Table 5. As shown in Table 5, the first and third layers from the substrate are made of Zr02 as high refractive index films, and the second layer is made of N203 as intermediate refractive index films. are arranged.

Since the reference wavelength input is 52, the trimming filter is empty. It is composed of alternating layers having an optical thickness of . As shown in FIG. 7, a comb-shaped trimming filter is obtained that has valleys with a transmittance of 55% near the 47th track and 57th track, and has a transmittance of approximately 85% or more at other visible peaks. FIG. 8 of Table 5 is a diagram showing the transmittance characteristic curve of the sixth embodiment of the trimming filter according to the present invention.

The film formation for the characteristic curve shown in FIG. 8 is the same as the film structure shown in the second example, but the optical film thickness of the second layer is 5%.
The data are shown in Table 6.
．． Table 6 As shown in Table 6, the first and third layers are made of Z2 with a high refractive index and have an optical thickness of 130 mm. A low refractive index layer mainly composed of Si02 is provided with an optical thickness of 136 mm.

As shown in Figure 8, there are valleys with transmittance of 55% near 48 and 59 points, and also in other visible regions? It has a transmittance of 5% or more. The characteristic curve shown in FIG.
Although the performance is degraded compared to the characteristic curve shown in FIG. 4 in that there is a relatively large ripple near the 4-way separation, the effect is sufficiently exhibited when used in practical use. As shown in the examples above, in the present invention, 48 skin,
The valley of transmittance near 58 mm corresponds to ￥・＾・i・
This is the peak of the reflectance when the film thickness is 258 mm on the side.

Therefore, it has the advantage that the interval between the valleys of each transmittance and the balance of each transmittance can be maintained with good reproducibility. Therefore, the present invention provides a filter having a membrane structure that is extremely easy to manufacture. Also, compared to other methods, for example, in the construction of the '21 interference filter, in which a narrow half-value film is coated on both sides of the substrate, '1} has a narrow half-value width. Large ripples remain on both sides of the valley, resulting in an overall low transmittance, and in case (2), there are drawbacks such as the inside of the transmission band and the inside of the transmittance valley being inappropriate.
On the other hand, the comb-shaped color separation correction trimming filter of the present invention has an excellent effect in that it has narrow valleys, high transmittance, and a wide transmission band. Furthermore, it is easy to apply the comb-shaped color separation correction trimming filter according to the present invention to a frequency separation three-tube or two-tube color television camera.

Also, other filters used in television camera optical systems,
For example, it is also possible to provide the trimming filter of the present application on the side of the filter for ultraviolet light removal, infrared light removal, and color temperature correction on which the interference film is not provided.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a trimming filter with a three-layer structure according to the present invention, FIG. 2 is a diagram showing a trimming filter with a five-layer structure according to the present invention, FIGS. 3, 4, 5, and 6. 7 and 8 are diagrams showing transmittance characteristic curves of trimming filters according to the present invention, respectively. S...Substrate, nj...Refractive index of the i-th layer from the substrate, di...Geometric thickness of the i-th layer from the substrate, ratio... ...Refractive index of external medium, ns...
Refractive index of the substrate, T...Transmittance, ^...Wavelength, Input o...Reference wavelength. Younger brother figure 2 figure 3 figure 4 younger brother figure 6 figure 7 figure 8

Claims (1)

[Claims] 1 High refractive index material with a refractive index of 1.8 or more, a refractive index of 1.
Optical optical The target film thickness is (10)/4λ_0×0.95 (
10) A trimming filter characterized by laminating layers existing between 10)/4λ_0×1.05.