JP2000199818A - Optical filter and optical shutter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a filter capable of largely shifting the wavelength area of fetched light by providing an actuator changing a distance between 1st and 2nd substrates and shifting the wavelength area of emitted light. SOLUTION: Plural PZTs 15 are arranged as the actuator between the substrates 11 and 12. By applying voltage to the PZT 15 from a driving circuit 16 by a control circuit 17, the PZT 15 is extended toward both ends by an amount in accordance with the voltage, so that a distance D between the substrates 11 and 12 is changed. Incident light beams made parallel beams are given to the filter 1 from an oblique direction so as to obtain a specified incident angle θwith respect to reflection films 13 and 14, and the light beams having the various number of reflecting times are included in the light beams transmitted through the film 14, whereby the light beams interfere with each other. By such interference, in what wavelength the phases of the light beams coincide depends on the distance D between the substrates 11 and 12. Therefore, when the distance D between the substrates 11 and 12 is changed, a wavelength region where the intensity of the emitted light beam is high is shifted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical filter and an optical shutter, and more particularly, to a filter and a shutter using an etalon.

[0002]

2. Description of the Related Art A reflection film having a high reflectance is formed on one side.
A device for taking out light in a certain wavelength range included in incident light by arranging a plurality of transparent substrates facing each other at regular intervals with the reflective film inside, and reflecting and interfering the incident light between the reflective films. , Has long been known as an etalon and is used as an optical filter. In recent years, an etalon filter in which the wavelength range of light to be extracted is variable has been proposed.

For example, in US Pat. No. 5,150,236,
Liquid crystal is filled between the substrates of the Fabry-Perot etalon, and the voltage applied to the liquid crystal is changed to shift the wavelength range of the light to be extracted. FIG. 13 shows the configuration of this filter. Two transparent substrates 51 and 52 are arranged in parallel to face each other, and reflection films 53 and 54 having a predetermined reflectance are provided on the facing surfaces of the substrates 51 and 52, respectively. A liquid crystal 55 is filled between the substrates 51 and 52, and a variable output power supply 56 for applying a voltage to the liquid crystal 55 is provided.

Light having a spread in wavelength is given from one substrate 51 to the reflection films 53 and 54 at a predetermined incident angle θ. This light passes through the reflecting films 53 and 54 one by one according to the reflectivity of the reflecting films 53 and 54, and
The reflection is repeated between 3, 54. The light transmitted through the reflective films 53 and 54 includes many light beams having different numbers of reflections, and these light beams interfere with each other, and a wavelength having a substantially uniform phase is extracted as emitted light. The refractive index of the liquid crystal 55 changes according to the applied voltage, and therefore, the phase of light passing through the liquid crystal 55 also changes according to the applied voltage. Thereby, the reflection film 5
The wavelengths at which the phases of the lights passing through 3, 54 are uniform also change, and the wavelength range of the emitted light can be shifted by the applied voltage.

In US Pat. No. 5,212,584, a medium whose refractive index changes depending on temperature is filled between substrates.
It has been proposed to shift the wavelength range of light to be extracted by changing the heat applied to the medium.

As described above, a conventional filter using an etalon uses an electro-optical material or a thermo-optical material as a medium through which light passes, thereby making the refractive index of the medium variable.
The wavelength of the light to be extracted is shifted. Typical applications of these filters are wavelength selection and spectral sensors in wavelength division multiplexed optical communications. In these applications, very high resolution wavelength selectivity is required, but the wavelength range to be selected is generally narrow.

[0007]

However, since the change width of the refractive index of the electro-optic material or the thermo-optic material is small, the wavelength range of the light to be extracted cannot be shifted too much by using these materials. For example, it is difficult to shift the wavelength range over several hundred nm, and an etalon filter capable of extracting an arbitrary wavelength range from visible light has not been realized.

The present invention has been made in view of the above problems, and has as its object to provide a filter capable of greatly shifting the wavelength range of light to be extracted, and a shutter using the filter.

[0009]

In order to achieve the above object, according to the present invention, opposing surfaces are arranged to face each other so as to be parallel, and a reflection film having a predetermined reflectance is provided on each opposing surface. A transparent first substrate and a second substrate, and the incident light from the first substrate side is reflected by the reflection film of the second substrate and the reflection film of the first substrate to cause interference,
A filter that emits light in a part of the wavelength range of the incident light to the second substrate side or the first substrate side, comprising an actuator that changes a distance between the first substrate and the second substrate; The wavelength range of the emitted light can be shifted.

[0010] This filter repeatedly reflects light on the reflective film provided on the first substrate and the reflective film provided on the second substrate to cause interference, thereby rejecting a part of incident light to the second substrate.
And the rest of the incident light is emitted to the first substrate side. Which wavelength light reinforces due to interference depends on the distance between the first substrate and the second substrate, and changing this distance shifts the wavelength region of high intensity contained in the emitted light. The filter is provided with an actuator for changing the distance between the first substrate and the second substrate, whereby the wavelength range of the emitted light can be easily and largely shifted. For example, the wavelength range of the emitted light can be shifted over the entire range of visible light.

Any actuator may be used, and an actuator may be selected according to the use of the filter. For example, if a piezo transducer (PZT) that expands and contracts according to an applied voltage is used, the distance between the substrates can be changed at high speed and with high accuracy.

In the filter having the above structure, the distance between the first substrate and the second substrate is changed via the actuator, and the first substrate and the second substrate at each point within the change range are changed.
Control means for controlling the residence time of the interval between the substrates,
The wavelength distribution of the emitted light may be made variable.

The wavelength range of the light emitted from the filter is determined at any point in time by the distance between the substrates. By changing the distance between the substrates to shift the wavelength range, a distribution of the wavelength of the emitted light can be brought about. it can. If the interval between the substrates is repeatedly changed in a short cycle, the wavelength distribution is averaged over time, and the filter emits light having the wavelength distribution.

The intensity of the individual wavelengths in the wavelength distribution depends on what value and for how long the substrate spacing is set,
By providing a control means for controlling this, various wavelength distributions can be realized. For example, if the distance between the substrates is changed at a constant speed between the first value and the second value, a wavelength distribution having uniform intensity over a certain range can be obtained, and the distance between the substrates can be changed from the first value to the second value. If the values are alternately set to the same value at the same time, a wavelength distribution including two wavelength ranges having substantially equal intensities can be obtained.

In the present invention, by changing the distance between the first substrate and the second substrate via the actuator through the filter having the above configuration, the state of the filter can be changed so that the wavelength range of the emitted light is a predetermined wavelength. A shutter for setting light in a first wavelength range and a second status in which the wavelength range of the emitted light does not include the predetermined wavelength range; By causing light in a predetermined wavelength range to enter the filter and switching between emission and blocking of light in the predetermined wavelength range according to the state of the filter, a shutter function is realized.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a filter and a shutter according to the present invention will be described with reference to the drawings. FIG.
FIG. 1 schematically shows the configuration of the filter 1 according to one embodiment of the present invention and the effect of the filter 1 on light. The filter 1 includes a transparent first substrate 11 and a second substrate 12 made of glass, and the substrates 11 and 12 are arranged to face each other. Inner surfaces of substrates 11 and 12, ie, opposing surfaces 11
a and 12a are finished as high-precision planes, and are set parallel to each other. The outer surfaces 11b, 12b of the substrates 11, 12 are not parallel to the opposing surfaces 11a, 12a, and the cross sections of the substrates 11, 12 are slightly wedge-shaped.

On the opposing surfaces 11a and 12a of the substrates 11 and 12, reflection films 13 and 14 are provided substantially over the entire area except the peripheral portion. The reflection film 13 is set so as to uniformly reflect the entire wavelength range of the incident light, and the reflectance r with respect to light from the surface side is a value close to 1, for example, about 0.8 to 0.9. The reflectance of the reflection film 13 with respect to light from the substrate 11 side is small, and most of the light is transmitted. Reflective film 1
4 is set exactly the same as the reflection film 13.

A plurality of PZTs 15 are arranged as actuators between the substrates 11 and 12, and both ends of each PZT 15 are fixed to the periphery of the opposing surfaces 11a and 11b by an adhesive. Each PZT 15 is provided with a drive circuit 16 for supplying an applied voltage, and wiring for voltage supply from the drive circuit 16 is connected to both ends of the PZT 15. The filter 1 includes a control circuit 17 for controlling each drive circuit 16, and the output voltage of each drive circuit 16 is individually controlled by the control circuit 17. When a voltage is applied from the drive circuit 16, the PZT 15 expands in both end directions by an amount corresponding to the voltage. Thereby, the substrates 11, 12
Is changed.

The filter 1 is provided with a parallel beam of incident light, which is obliquely applied to the reflection films 13 and 14 so as to have a predetermined incident angle θ. The incident light is applied to the substrates 11, 1
2 may be provided from either side, but here, the description will be made assuming that the first substrate 11 is provided. The incident light is
1 and the reflection film 13 to reach the reflection film 14.
Most of this light is reflected according to the reflectance r of the reflective film 14, and only the remaining part passes through the reflective film 14. Reflective film 14
Is transmitted through the substrate 12 and becomes emitted light.

The light reflected by the reflection film 14 reaches the reflection film 13 and is largely reflected according to the reflectance r.
Only a part is emitted light (not shown). The light reflected by the reflection film 13 reaches the reflection film 14 again, and most of the light is reflected, and only part of the light is emitted light. The light is thereafter reflected by the reflective film 13, 1
The light is repeatedly reflected by the light source 4, and all light is emitted during that time. Hereinafter, the outgoing light on the second substrate 12 side is also referred to as transmitted light, and the outgoing light on the first substrate 11 side is also referred to as reflected light.

Light transmitted through the reflective film 14 includes light having various numbers of reflections, such as 0, 2, and 4, the number of reflections, and these lights interfere with each other. I do. Due to this interference, light having substantially the same phase is strengthened, and light having substantially the opposite phase is weakened, and a plurality of wavelength regions having high intensity appear in the light emitted from the substrate 12 side. The wavelengths of the light whose phases match each other depend on the distance D between the substrate 11 and the substrate 12, and therefore, when the distance D between the substrate 11 and the substrate 12 changes, the wavelength region where the intensity of the emitted light is high shifts.

The light transmitted through the reflective film 13 includes light having various numbers of reflections, such as one, three, and five times. When these lights interfere with each other, the outgoing light (reflected light) on the substrate 11 side becomes light obtained by removing the outgoing light (transmitted light) on the substrate 12 side from the incident light.

In the filter 1, by applying a voltage to the PZT 15, the distance D between the substrate 11 and the substrate 12 is changed to shift the wavelength range of the emitted light. At this time, the control circuit 17 makes the amount of expansion of each PZT 15 the same so that the distance between the substrates 11 and 12 is always uniform. For this reason, uniform interference occurs throughout the filter 1, and the wavelength range of the emitted light is not deformed and noise is not mixed into the emitted light. A part of the light transmitted through the reflection films 13 and 14 is transmitted to the outer surfaces 11 b and 1 of the substrates 11 and 12.
It is reflected by 2b and reenters between the reflection films 13 and 14,
Since the outer surfaces 11b and 12b are not parallel to the opposing surfaces 11a and 11b, the light does not cause noise in the emitted light.

The transmittance T of the filter 1, that is, the ratio of the intensity of the outgoing light on the substrate 12 side to the incident light is obtained by the equation (1) known as a Fabry-Perot etalon. T = 1 / {1 + F · sin ² (δ / 2)} (1)

Here, δ is a phase difference determined by the refractive index n of the medium between the substrates 11 and 12, the interval D between the substrates 11 and 12, the incident angle θ, and the wavelength λ of the incident light. ). δ = 4π · n · D · cos (θ) / λ (2)

F is the reflectance r of the reflection films 13 and 14
And is obtained by equation (3). F = 4 · r ² / (1−r ² ) ² (3)

As is apparent from the equation (1), the transmittance T is maximized when the phase difference δ in the equation (2) is 0, ± 2π, ± 2π.
4π... When the refractive index n and the incident angle θ of the medium between the substrates 11 and 12 are constant, the phase difference δ is proportional to the distance D between the substrates 11 and 12, and inversely proportional to the wavelength λ. Therefore, a high-intensity wavelength region appears regularly in transmitted light, and the high-intensity wavelength region can be shifted by changing the distance D between the substrates 11 and 12. At this time, the shift amount of the center wavelength in each of the wavelength regions having high intensity is proportional to the change amount of the interval D.

Specific examples of the transmittance T of the filter 1 are shown in FIGS.
As shown in FIG. These figures show the visible light wavelength range of 400 to
It shows the transmittance calculated for the entire 700 nm.
FIG. 2 shows that the reflectance r of the reflection films 13 and 14 is 0.8, the incident angle θ is 30 °, and the medium between the substrates 11 and 12 is air (refractive index n).
= 1), the transmittance when the distance D between the substrates 11 and 12 is set such that the transmittance is maximum at the wavelength λ = 550 nm. At this time, the interval D is 423 nm. λ =
50% or more transmittance in the range of 530 to 570 nm, λ =
The transmittance is 80% or more in the range of 510 to 590 nm.

FIGS. 3 and 4 show substrates 11, 12 respectively.
From the values in FIG. 2 at −77 nm and +3
The transmittance when 346 nm and 462 nm are changed by 9 nm. In FIG. 3, the wavelength region of high intensity is shifted by 100 nm to the short wavelength side and the center wavelength is 450.
In FIG. 4, the wavelength region with high intensity is shifted by 50 nm to the longer wavelength side and the center wavelength is 600 nm.
It has become. The wavelength region having a high intensity is slightly narrowed by shifting the distance between the substrates 11 and 12 to the shorter wavelength side.
No significant waveform change occurs. In FIG. 4, a part of the adjacent wavelength region having high intensity appears near 400 nm.

As described above, by changing the distance D between the substrates 11 and 12, it is possible to largely shift the wavelength region having a high intensity. The amount by which the interval D should be changed is on the order of the wavelength of the light to be extracted. In the filter 1 of this embodiment, PZT having an extremely high resolution of about nm is used as an actuator for changing the interval D between the substrates 11 and 12. Therefore, the interval D and therefore the center wavelength of the wavelength range can be controlled with high accuracy. Further, the PZT can be driven at a high speed of about μsec, and the change of the interval D, that is, the shift of the wavelength range can be performed in a very short time. The actuator is PZ
It is also possible to use one other than T, and an appropriate actuator may be selected according to the use of the filter.

As shown in FIG. 5, the light emitted from the first substrate 11 can be used. In this mode of use, the filter 1 is of a reflection type, and in the mode of use of FIG. 2 utilizing the emitted light on the second substrate 12 side, the filter 1 is of a transmission type. The relationship between the reflectance R and the transmittance T of the filter 1 is R = 1-T if negligible absorption is ignored. As described above, the reflected light is light obtained by removing transmitted light from incident light.
As an example, FIG. 6 shows the reflectance R of the filter 1 when the transmittance T is as shown in FIG. When white light is made incident on the filter 1, the reflected light and the transmitted light have a complementary color relationship with each other. For example, it can be used as a complementary color filter.

The wavelength range where the intensity of light included in the light emitted from the filter 1 is high is fixed at a point in time by the distance D between the substrates 11 and 12 at that time. However, changing the spacing D can result in a wavelength distribution in the outgoing light over the entire period of the change. In particular, if the interval D is repeatedly changed in a cycle shorter than the light use time, the wavelength distribution is averaged over time, and the filter 1 emits light having the wavelength distribution. Since the intensity of each wavelength in the wavelength distribution depends on what value and how long the interval D between the substrates 11 and 12 is set, by controlling the changing speed of the interval D by the control circuit 17, Any wavelength distribution can be obtained.

Voltage applied to PZT 15 and filter 1
7 to 9 illustrate the relationship between the wavelength distributions of the outgoing light beams. 7A shows the time change of the applied voltage, and FIG. 7B shows the wavelength distribution of the light transmitted through the filter 1. In this example, a constant voltage V1 is always applied, and only one wavelength region with high intensity appears in the transmitted light.

In the example shown in FIG. 8, as shown in (a) or (b), the application voltage is linearly changed between two voltages V1 and V2. At this time, the voltage V
One change between V1 and V2 shifts the wavelength region of high intensity as shown in (c). When this change of the applied voltage is repeated, the time-averaged wavelength distribution becomes as shown in (d). In this control, the filter 1 functions as a band-pass filter that transmits a part of B light to G light among blue (B) light, green (G) light, and red (R) light included in visible light. .

In the example of FIG. 9, as shown in FIG. 9A, the applied voltage is increased from V1 to V2 at a constant speed, and
3, increasing from V3 to V4 at a constant speed, immediately increasing to V5, further increasing to V6 at a constant speed, and returning to V1. At this time, as shown in (b), the wavelength range of high intensity gradually shifts in three ranges according to the voltage change from V1 to V2, from V3 to V4, and from V5 to V6,
In the range corresponding to the abrupt voltage change from V2 to V3 and from V4 to V5, a wavelength region with high intensity does not appear. By repeating the change of the applied voltage, the wavelength distribution averaged over time is as shown in FIG. In this control, the filter 1 functions as a color filter that transmits B light, G light, and R light, and hardly transmits intermediate color light.

As described above, the filter 1 is a PZT15
The wavelength distribution can be arbitrarily set by controlling the voltage applied to the filter, and can be used as a multifunctional filter. In particular, since PZT responds quickly to the applied voltage,
The cycle of changing the applied voltage can be made extremely short, and the filter 1 can provide light having a uniform wavelength distribution even when the use time of one emitted light is short and about 100 μsec or even shorter. .

The filter 1 capable of changing the wavelength range where the intensity of the emitted light is high also functions as a shutter for the entire incident light or a shutter for light in a specific wavelength range included in the incident light. That is, if the wavelength range where the intensity of the emitted light is high is set outside the wavelength range of the incident light, the entire incident light can be blocked, and if it is set outside the specific wavelength range, the light in that wavelength range is blocked. be able to. It is also possible to set a plurality of specific wavelength ranges and sequentially switch the light to be blocked. Even when the filter 1 functions as a shutter, the characteristics of the PZT 15 are utilized to provide a shutter with excellent responsiveness.

FIG. 10 shows an example of the use of the filter 1 as a shutter. In this example, the filter 1 is incorporated in a transmission type color image reading device 2. The reading device 2 includes a filter 1, a light source unit 21, a detection unit 25, and a transport unit 29. The color image F to be read is arranged between the filter 1 and the detection unit 25, is conveyed by the conveyance unit 29 in a direction perpendicular to the light transmitted through the filter 1, and is read one by one.

The light source 21 is a lamp 2 that emits white light.
2. A reflector 23 that reflects the light of the lamp 22 and a collimator lens 24 that causes the light reflected by the reflector 23 to enter the filter 1 as a parallel light flux. The detection unit 25 includes a large number of charge-coupled devices (CCDs).
An area sensor 26 arranged in a dimension, a signal processing circuit 27 for processing an output signal of the area sensor 26, and an image forming lens 28 for forming light transmitted through the filter 1 and the color image F on a light receiving surface of the area sensor 26. Become.

The signal processing circuit 27 individually generates a B signal representing an image of B light, a G signal representing an image of G light, and an R signal representing an image of R light from the output signal of the area sensor 26. Each CCD of the area sensor 26 is set to be sensitive to all wavelengths of visible light. As a result, the reading device 2 can select three types of CCs selectively sensitive to the B light, the G light, and the R light.
It has three times the resolution of a device in which Ds are alternately arranged. B light is applied to the area sensor 26 having such a setting,
If the G light and the R light are guided simultaneously, the signal processing circuit 27 cannot perform signal processing correctly.

Therefore, the filter 1 transmits the B light, the G light, and the R light individually for a predetermined time. When transmitting each color light, the control circuit 17 causes the filter 1 to function as a band-pass filter. Filter 1 is B light, G light, R light
After transmitting one of the lights, the signal processing circuit 2
7 processes the output signal of the area sensor 26. If the area sensor 26 receives visible light during this time, an error occurs in the signal of the next color light. For this reason, the control circuit 17 sets the wavelength range of the transmitted light of the filter 1 outside the wavelength range of the visible light until the next color light is transmitted, and causes the filter 1 to function as a shutter for the visible light.

When the processing of the signal processing circuit 27 is completed, the filter 1 transmits the next color light, and thereafter blocks visible light for a period required for the signal processing. When all the processes of the B light, the G light, and the R light are completed, the transport unit 29 transports the color image F by a distance corresponding to the size of the area sensor 26, and sets the next reading area between the filter 1 and the area sensor 26. Position. During this time, the filter 1 also blocks visible light. By repeating this process, the entire color image F is read. If the color image is continuous like a photographic film, the filter 1 blocks visible light even during frame advance.

Here, the filter 1 is connected to the light source 2
1 and the image F to be read, the filter 1 may be arranged between the image F and the detection unit 25. When the shutter 1 and the light source unit 21 of the color image reading device 2 are taken out, the light source device is provided with a shutter, and can be used for an image display device such as a projector.

The opposing surfaces 11a and 12a of the two substrates 11 and 12 of the filter 1 must always be set in parallel.
For this reason, the P attached to the peripheral portions of the substrates 11 and 12
It is preferable to provide a plurality of ZTs 15 instead of one. PZT
15 preferred arrangement examples are shown in the front view of FIG.

In FIG. 11, (a) shows two substrates 11 and 12 with two wide PZTs 15a and 15b opposed to each other.
Are arranged along the sides. (B) is a diagram in which four wide PZTs 15a to 15d are arranged along the sides of the substrates 11 and 12 so as to face each other.
(C) shows three narrow PZTs 15a to 15c mounted on a substrate 1.
It is arranged near two adjacent corners 1 and 12 and near the center of the opposite side. (D) shows four narrow PZT1s.
5a to 15d are arranged at four corners of the substrates 11 and 12.

As described above, in this embodiment, the PZT 15 is fixed to the substrates 11 and 12 using an adhesive, but a filter may be manufactured by combining the PZT 15 and the substrates 11 and 12 by another method. . One example is shown in the perspective view of FIG.

In FIG. 12, two wide PZTs 15
a and 15b are arranged to face each other, and the substrate 11 and the substrate 12 are connected by two coil springs 18a and 18b.
The substrates 11 and 12 are urged in a direction in which the interval is reduced. P
When a voltage is applied, the ZTs 15a and 15b
8a, 18b, the substrates 11, 12
Change the interval. Opposing surfaces 11a of the substrates 11, 12;
Grooves corresponding to the width and thickness of the PZTs 15a and 15b are formed in the 12a, and both ends of the PZTs 15a and 15b are inserted into these grooves. Thereby, the facing surface 11
The movement of the PZTs 15a and 15b along the directions a and 12a is prevented.

PZ perpendicular to substrates 11 and 12
The length of T15 defines the distance between the substrates 11 and 12, and greatly affects the performance of the filter 1. The length of the PZT 15 in this direction needs to be set as precisely as possible, but a processing error may occur,
Further, in the case of fixing by bonding, even if the precision of the length of the PZT 15 is high, the substrates 11, 12 may be formed depending on the thickness of the adhesive.
May be uneven.

However, the unevenness of the interval between the substrates 11 and 12 at the time of manufacturing the filter 1 can be easily removed at the time of use by the applied voltage. For example, consider a case in which the lengths of the four PZTs 15a to 15d are all different, including the thickness of the adhesive, in the configuration of FIG. The length of PZTs 15a to 15d is L1 to L1, respectively.
L4, and if L1 <L2 <L3 <L4,
Voltages E1 to E4 having a relationship of E1>E2>E3> E4 are applied to the PZTs 15a to 15d, respectively. That is, by applying a relatively large voltage to a short PZT and relatively expanding the PZT relatively, all PZTs are expanded.
The lengths of T15a to 15d can be matched.

As described with reference to FIG. 1, the filter 1 is provided with the drive circuit 16 for each of the plurality of PZTs 15 in order to perform the above-described correction. The control circuit 17 includes a non-volatile memory that stores the length of each PZT 15 at the time of fabrication.
The output voltage of the drive circuit 16 is individually controlled. Thereby, the interval between the substrates 11 and 12 of the filter 1 is always kept uniform.

As described above, the uniform spacing between the substrates 11 and 12 can be always ensured because the applied voltage, which is a control signal, is converted into a change in physical magnitude, and the change in the magnitude is converted. PZ that transmits directly to the substrates 11, 12 without any intervention
This is largely due to the use of T as an actuator.

Although the example in which the medium between the substrates 11 and 12 is air has been described here, the entire filter 1 is housed in a transparent container, and the space between the substrates is evacuated, or another filter having a high refractive index is used. A medium may be present between the substrates.

[0053]

According to the filter of the present invention, the distance between the two substrates can be freely changed by the actuator, so that the shift amount of the wavelength range of the outgoing light increases and the incident light having a wide wavelength range. , A desired wavelength range can be selected. For example, blue light, green light, and red light can be arbitrarily extracted from light in the entire visible region, and can be used for reading and displaying a color image. In addition, depending on which side of the two substrates emits light, a filter of a transmission type or a reflection type is provided, which is easy to use and can use any light having a complementary color relationship.

Further, by changing the distance between the two substrates via the actuator and controlling the residence time of the distance between the substrates at each point within the range to be changed, the wavelength distribution of the light to be extracted can be arbitrarily set. Can be set.

Further, by changing the distance between the two substrates via the actuator and setting the filter so that the wavelength range of the emitted light includes and does not include the predetermined wavelength range, the light in the predetermined wavelength range is obtained. Shutter.
If a plurality of spaced wavelength ranges are set as predetermined wavelength ranges and the wavelength range of the light emitted from the filter includes these wavelength ranges in order, it is possible to sequentially switch the wavelength range of the light to be extracted.

[Brief description of the drawings]

FIG. 1 shows the configuration of a filter according to an embodiment of the present invention;
The side view which shows the effect | action with respect to light typically.

FIG. 2 is a diagram showing an example of transmittance of the filter.

FIG. 3 is a view showing transmittance when the substrate interval of the filter is reduced.

FIG. 4 is a view showing transmittance when the substrate interval of the filter is increased.

FIG. 5 is a side view showing an embodiment in which the filter is used as a reflection type.

FIG. 6 is a diagram showing an example of the reflectance of the filter.

FIG. 7 is a diagram showing an example of a relationship between a voltage applied to PZT of the filter and a wavelength distribution of emitted light.

FIG. 8 is a diagram showing another example of the relationship between the voltage applied to PZT of the filter and the wavelength distribution of emitted light.

FIG. 9 is a diagram showing still another example of the relationship between the voltage applied to PZT of the filter and the wavelength distribution of emitted light.

FIG. 10 is a diagram illustrating a schematic configuration of a color image reading apparatus that uses the filter as a shutter.

FIG. 11 is a front view showing an example of disposing PZT of the filter.

FIG. 12 is a perspective view showing another configuration example of the filter.

FIG. 13 is a side view schematically showing a configuration of a conventional filter and an action on light.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 filter 11, 12 substrate 11a, 12a substrate facing surface 13, 14 reflective film 15 PZT (actuator) 16 drive circuit 17 control circuit 2 color image reading device 21 light source unit 22 lamp 23 reflector 24 collimator lens 25 detector 26 area sensor 27 Signal processing circuit 28 Imaging lens

Continued on the front page F term (reference) 2H041 AA21 AB10 AB14 AB15 AB16 AC08 AZ01 AZ05 2H048 GA13 GA25 GA51 GA61 GA62 5G435 AA00 BB17 CC12 DD04 DD13 FF03 GG01 GG02 GG13 GG28

Claims (3)

[Claims] A transparent substrate having a reflective film having a predetermined reflectance provided on each of the opposed surfaces, wherein the first and second substrates are provided with a reflective film having a predetermined reflectance;
The incident light from the first substrate side is transmitted to the reflection film of the second substrate and the first substrate.
The light is reflected by the reflection film of the first substrate to cause interference, so that light in a part of the wavelength range of the incident light is transmitted to the second substrate or the first substrate.
A filter that emits light toward the substrate side, the actuator including an actuator that changes a distance between the first substrate and the second substrate, wherein a wavelength range of the emitted light can be shifted. 2. The method according to claim 1, wherein the distance between the first substrate and the second substrate is changed via the actuator, and the dwell time of the distance between the first substrate and the second substrate at each point within the range to be changed. 2. The filter according to claim 1, further comprising a control unit for controlling a wavelength distribution of the emitted light. 3. A shutter for light in a predetermined wavelength range, wherein the filter according to claim 1 and the distance between the first substrate and the second substrate are changed via the actuator. Controlling means for setting a state to a first state in which the wavelength range of the emitted light includes the predetermined wavelength range and a second state in which the wavelength range of the emitted light does not include the predetermined wavelength range, A shutter in which the light in the predetermined wavelength range is switched between emitting and blocking the light in the predetermined wavelength range depending on the state of the filter.