Filter for TV and video cameras
An infrared-cut filter for TV and video cameras was calculated and fabricated. The filter contains 28 alternating SiO₂ and TiO₂ layers. The filter was calculated using the principle of unequal-thickness layers. This filter has a transmittance of 95 % in 400 to 650 nm range and 1 % in 700 to1150 nm r...
Збережено в:
| Дата: | 2005 |
|---|---|
| Автори: | , , , , |
| Формат: | Стаття |
| Мова: | English |
| Опубліковано: |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2005
|
| Назва видання: | Semiconductor Physics Quantum Electronics & Optoelectronics |
| Онлайн доступ: | http://dspace.nbuv.gov.ua/handle/123456789/120647 |
| Теги: |
Додати тег
Немає тегів, Будьте першим, хто поставить тег для цього запису!
|
| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | Filter for TV and video cameras / L.I. Berezhinsky, Dae-Yong Park, Chang-Min Sung, Kwang-Ho Kwon, Sang -Hoon Chai // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2005. — Т. 8, № 1. — С. 106-109. — Бібліогр.: 5 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
irk-123456789-120647 |
|---|---|
| record_format |
dspace |
| spelling |
irk-123456789-1206472017-06-13T03:06:36Z Filter for TV and video cameras Berezhinsky, L.I. Dae-Yong Park Chang-Min Sung Kwang-Ho Kwon Sang-Hoon Chai An infrared-cut filter for TV and video cameras was calculated and fabricated. The filter contains 28 alternating SiO₂ and TiO₂ layers. The filter was calculated using the principle of unequal-thickness layers. This filter has a transmittance of 95 % in 400 to 650 nm range and 1 % in 700 to1150 nm range. 2005 Article Filter for TV and video cameras / L.I. Berezhinsky, Dae-Yong Park, Chang-Min Sung, Kwang-Ho Kwon, Sang -Hoon Chai // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2005. — Т. 8, № 1. — С. 106-109. — Бібліогр.: 5 назв. — англ. 1560-8034 PACS: 68.55.J; 42.79.Fm http://dspace.nbuv.gov.ua/handle/123456789/120647 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| description |
An infrared-cut filter for TV and video cameras was calculated and fabricated. The filter contains 28 alternating SiO₂ and TiO₂ layers. The filter was calculated using the principle of unequal-thickness layers. This filter has a transmittance of 95 % in 400 to 650 nm range and 1 % in 700 to1150 nm range. |
| format |
Article |
| author |
Berezhinsky, L.I. Dae-Yong Park Chang-Min Sung Kwang-Ho Kwon Sang-Hoon Chai |
| spellingShingle |
Berezhinsky, L.I. Dae-Yong Park Chang-Min Sung Kwang-Ho Kwon Sang-Hoon Chai Filter for TV and video cameras Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Berezhinsky, L.I. Dae-Yong Park Chang-Min Sung Kwang-Ho Kwon Sang-Hoon Chai |
| author_sort |
Berezhinsky, L.I. |
| title |
Filter for TV and video cameras |
| title_short |
Filter for TV and video cameras |
| title_full |
Filter for TV and video cameras |
| title_fullStr |
Filter for TV and video cameras |
| title_full_unstemmed |
Filter for TV and video cameras |
| title_sort |
filter for tv and video cameras |
| publisher |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| publishDate |
2005 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/120647 |
| citation_txt |
Filter for TV and video cameras / L.I. Berezhinsky, Dae-Yong Park, Chang-Min Sung, Kwang-Ho Kwon, Sang -Hoon Chai // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2005. — Т. 8, № 1. — С. 106-109. — Бібліогр.: 5 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
| work_keys_str_mv |
AT berezhinskyli filterfortvandvideocameras AT daeyongpark filterfortvandvideocameras AT changminsung filterfortvandvideocameras AT kwanghokwon filterfortvandvideocameras AT sanghoonchai filterfortvandvideocameras |
| first_indexed |
2025-07-08T18:16:42Z |
| last_indexed |
2025-07-08T18:16:42Z |
| _version_ |
1837103687334363136 |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2005. V. 8, N 1. P. 106-109.
© 2005, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
106
PACS: 68.55.J; 42.79.Fm
Filter for TV and video cameras
L.I. Berezhinsky1, Dae-Yong Park2, Chang-Min Sung2, Kwang-Ho Kwon3, and Sang-Hoon Chai4
1 Institute of Semiconductor Physics, NAS of Ukraine, 45, prospect Nauky, 03028 Kyiv, Ukraine
Phone: +38 (044) 525-5778. E-mail: lib1938@yahoo.com
2 Havit Information Co., 59-3 Jang-Dong, Yusong-gu, Daejeon, 305-343, Korea
E-mail: bspark@havit.co.kr
3 Department of Electronic Engineering, Hanseo University, 360, Daegok-Ri, Haemi-Myun, Seosan, Choongnam,
356-820, Korea. E-mail: khkwon@creneed.com
4 Department of Electronic Engineering, Hoseo University, 21, Sechul-Ri, Baebang-Myun, Asan, Choongnam, 336-
795, Korea
Abstract. An infrared-cut filter for TV and video cameras was calculated and
fabricated. The filter contains 28 alternating SiO2 and TiO2 layers. The filter was
calculated using the principle of unequal-thickness layers. This filter has a transmittance
of 95 % in 400 to 650 nm range and 1 % in 700 to1150 nm range.
Keywords: interference coating, multilayer interference filter, cut filter.
Manuscript received 14.01.05; accepted for publication 18.05.05.
It is necessary to use infrared-cut filters to create a high-
quality image using TV and video cameras in natural
(solar) light. This necessity is caused by the following
fact. Human eyes perceive light within the spectral range
400 to 700 nm. However, the photosensitivity of a
photodetector (as a rule, is a silicon-target matrix used in
TV and video cameras reaches up to 1200 nm. Therefore,
the presence of a photocurrent produced by 700 to
1200 nm waves in a total electric signal is undesirable
because it does not carry any useful information about
image colors. This allows to formulate the following
requirements for optical properties of filters: the
transmittance in 400 to 650 nm range should be not less
than 90 – 95 % and no more than 1 % in 700 to1200 nm
range.
In [1], it was reported about the filter provided the
transmittance of more than 90 % in 400 to 700 nm range
and less than 1 % in 700 to 930 nm one. At the same
time, this filter has the very high transmittance (80 –
90 %) in the region of 1000 to 1200 nm. It seems that the
role of this transmittance can be ignored because the
photosensitivity of silicon in this region is very small.
However, a simple calculation shows that it is not so.
The solar radiation power in 1000 to 1200 nm range near
the Earth surface contains from 18 to 20 % of the solar
radiation power in the whole visible region of 400 to
650 nm. Therefore, the contribution into a total
photocurrent from 1000 to 1200 nm waves can be
appreciable despite the small photosensitivity of silicon
in this region. In this article, we describe a filter with the
transmittance of about 95 % within the region of 400 to
650 nm and its improved characteristics in the region of
1000 to 1200 nm.
The filter represents the system (nHnL) NnH of
alternating layers with high- and low-refractive indexes
and optical thickness nd = λ / 4 (λ – characteristic
wavelength, d – layer thickness). As nL material we used
SiO2 with the refractive index nL = 1.45454, and as nH
material we used TiO2 with nH = 2.25565. According to
M. Born and E. Wolf [2], the reflection of a multilayer
system reaches 99 % at N = 6, i.e., a filter must contain
13 alternating layers nH, nL, nH, nL,…, nH.
A band where the filter has a very high reflection is
called the suppression band, designated as R100. The
wavelength corresponding to the middle of R100 band is
designated as λ0 (reference wavelength). The layers have
the optical thickness equal to λ0 / 4.
The half-width of R100 band in the units g = λ0 / λ
depends only on the difference between refractive
indexes nH and nL and is defined by the following
expression [3]:
LH
LHarcsin2
nn
nng
+
−
π
=Δ . (1)
Let us define the width of R100 band for our data.
The high reflection region of our filter should extend
from 700 to 1200 nm. The center of this range lies at
λ0 = 950 nm. Substituting nH = 2.25565 and
nL = 1.45454 into (1) we get Δg ≈ 0.13. R100 bandwidth
has the value of λ0·2Δg = 247 nm. Thus, our materials
SiO2 and TiO2 can supply only 247 nm R100 bandwidth,
while the filter bandwidth should have its extent of
1200 – 700 = 500 nm. It means that to construct a filter
with 500 nm R100 bandwidth it is necessary to use two
(or three) systems of layers with different reference
wavelengths λ0' and λ0". The wavelengths λ0' and λ0" are
chosen from the requirement that the bands of high
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2005. V. 8, N 1. P. 106-109.
© 2005, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
107
reflection partly overlap. It is clear that the formation of
R100 band with the width of 500 nm by means of two-
layer systems with different λ0' and λ0" using
2SiOn and
2TiOn is a very difficult task. At the same time, the
usage of three-layer systems makes the filter design very
complex, and its practical realization is very difficult.
We have constructed a filter of two systems such as
(HL)6H with λ0' = 736 nm and λ0" = 900 nm and
achieved further widening R100 band by means of
suppression (increasing) of lateral transmittance minima.
We obtained the suppression band from 680 to 1050 nm
with transmittance of 1 to 1.5 %. However, a large
number of lateral transmittance minima arises on the
shortwave side of this band in the region of 400 to
650 nm and on the longwave one of 1050 nm. The
lateral minima in the region of 400 to 650 nm are
generated by the layer system at λ0' = 736 nm, and the
ones with wavelengths longer than 1050 nm are
generated by the layer system at λ0" = 900 nm. The
number of these lateral minima is equal to the number of
layers in every system, and their depths reach 60 %.
Hence, the problem of a filter construction lies in
elimination of these minima and preservation of the
transmittance in the range of 400 to 600 nm at the level
of 95 % and vice versa increasing the depth of
transmittance minima down to zero in the region of 1050
to1200 nm.
There are a few receptions to correct the
transmittance on both sides of R100 band. One of them is
to use layers with unequal optical thicknesses according
the condition
nHhH + nLhL = λ0 / 2, (2)
where hH and hL are geometrical thicknesses of layers
with a high- and low-refractive indexes. The
transmittance is increased in a shortwave range of R100
band and simultaneously is decreased in a longwave
range when nHhH / nLhL > 1. The relation nHhH / nLhL < 1
gives the opposite result.
A very effective method for increasing the
transmittance of a lateral minimum is creation of the last
nL layer at the optical thickness λ0 / 8 on the surface of
this multilayer system. However, it should be noted that
the use of such layer as well as introduction of matching
layers between the substrate and multilayer system does
not allow to obtain the transmittance more than 80 % in
400 to 420 nm range.
The range of 400 to 420 nm is shortwave in relation
to R100 band with the center at λ0' = 736 nm. However, it
can be considered as the longwave one in relation to R100
band with the center at λ01, which satisfies the condition
nHhH = nLhL = (3/4)λ01 (3)
or
(3/4) λ01= (1/4) λ0'; λ01 < λ0'. (4)
Fig. 1. Optical characteristic of IR-cut filter (simulation): 1 –
this work, 2 – filter from [1].
Fig. 2. Optical characteristic of the real IR-cut filter
(experiment).
Fig. 3. Optical characteristics of IR-cut filters, produced by
Melles Griot (USA) (1) and Taeyoung (Korea) (2).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2005. V. 8, N 1. P. 106-109.
© 2005, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
108
The design and layer thicknesses of the IR cut-filter.
Layer Material Refractive index Optical thickness (in λ0)
1 SiO2 1.45454 0.170
2 TiO2 2.25565 0.332
3 SiO2 1.45454 0.335
4 TiO2 2.25565 0.329
5 SiO2 1.45454 0.332
6 TiO2 2.25565 0.325
7 SiO2 1.45454 0.331
8 TiO2 2.25565 0.316
9 SiO2 1.45454 0.330
10 TiO2 2.25565 0.316
11 SiO2 1.45454 0.330
12 TiO2 2.25565 0.316
13 SiO2 1.45454 0.330
14 TiO2 2.25565 0.316
15 SiO2 1.45454 0.295
16 TiO2 2.25565 0.250
17 SiO2 1.45454 0.270
18 TiO2 2.25565 0.250
19 SiO2 1.45454 0.270
20 TiO2 2.25565 0.250
21 SiO2 1.45454 0.265
22 TiO2 2.25565 0.235
23 SiO2 1.45454 0.270
24 TiO2 2.25565 0.240
25 SiO2 1.45454 0.275
26 TiO2 2.25565 0.235
27 SiO2 1.45454 0.285
28 TiO2 2.25565 0.285
Substrate Glass 1.51218
It means that we can consider a band with the center λ01
as a band of the next order concerning the band with the
center λ0'. Therefore, if we change the transmittance of
the filter in the longwave range for λ0' band, we
simultaneously in the same way change the
transmittance in the longwave range for λ01 band, i.e., in
400 – 420 nm range. On this basis, we have used layers
of an unequal optical thickness for increasing the
transmittance in the longwave range of λ0' = 736 nm.
Choosing the layer geometrical thickness we used the
relationship
α·nHhH + (2 – α) nLhL = λ0' / 2, (5)
where the coefficient α < 1 and nHhH = nLhL = λ0'/4. For
optimizing the value of α, we used the geometrical
thicknesses hH' and hL' with the relation
nLhL' / nHhH' = 1.2. The transmittance of 90 to 95 % in
the range 400 to 420 nm was obtained for these layer
thicknesses. However, the transmittance in the range of
550 to 650 nm was decreased. We have tried to improve
the reduction of transmittance in the range of 500 to
650 nm introducing the additional and matching layers.
The deposition of the latter layer with λ0'/8 optical
thickness allowed to increase the transmittance in this
range up to 80 %. Further magnification was achieved
by the introduction of the matching λ0'/4 layer between
the substrate and multilayer system.
The refractive index of the matching layer can be
found from the relationship [4]
SEnNn = , (6)
where NE is the effective refractive index of the
multilayer system, and nS is the refractive index of the
substrate. It may happen so that a substance with
refractive index n is nonexistent in nature. In this case, it
is possible to construct system of three layers such as
(aHbLaH) that will play functionally the same role as
well as a quarter-wave layer with refractive index n.
Coefficients a and b can be determined by the method of
effective layers [5]. For our case, the refractive index of
the matching layer and its design was calculated in [1].
The filter was constructed on the basis of two-layer
systems with the reference waves λ0' = 736 nm and
λ0" = 900 nm. After the combination of these systems on
the substrate, the optimization of the layer thickness at
the interface of these systems was carried out using a
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2005. V. 8, N 1. P. 106-109.
© 2005, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
109
computer. The final filter contains 28 layers and has the
structure (0.44L, 0.88H, 0.44L)0.5L(HL)12H0.5L. The
layer thicknesses are summarized in Table. The
transmittance of the calculated filter and filter from [1] is
shown in Fig. 1. It is seen that, in the visible range, the
transmittance is nearly the same for both filters and
reaches 95 % in 450 to 620 nm range. The transmittance
of the calculated filter averages about 2 to 3 % higher
than that of the filter in [1]. In the infrared region,
however, the distinction of transmittance is drastic. The
calculated filter has the transmittance close to zero in the
region from 700 to 1030 nm, 5 % – in the region of 1050
to 1120 nm, and, only for 1150–1200 nm, the trans-
mittance band of more than 80 % is observed.
The transmittance of the obtained filter
manufactured using the above-mentioned design is
shown in Fig. 2. The small (~ 3 %) transmittance
reduction of the real filter as compared with the
simulated one is caused by monitoring errors for layer
thicknesses during manufacturing. The accuracy of the
latter was ± 2 nm. For comparison, the transmittance of
available commercial filters comprising 29 to 30 layers
and manufactured by Taeyoung (Korea) and Melles
Griot (USA), which are used in modern TV and video
cameras, are shown in Fig. 3.
References
1. L. Berezhinsky, K.H. Kwon, B.S. Park, Infrared-cut
filter // Jpn J. Appl. Phys. 40, N 10, p. 5953-5954
(2001).
2. M. Born and E. Wolf, Principles of optics.
Pergamon Press, Oxford, 2nd ed., p. 51 (1964).
3. T.N. Nikolayeva, Interference coverings,
Mashinostroyeniye, Leningrad (1973) (in Russian) .
4. H.A. Macleod, Thin-film optical-filters. Adam
Hilger, Bristol, p. 73 (1986).
5. L.I. Epstein, The design of optical filters // J. Opt.
Soc. Amer. 12, N 11, p. 806-810 (1952).
|