JP2013170867A - Spectroscopic measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spectroscopic measurement device capable of acquiring light having a desired wavelength with a high resolution.SOLUTION: A spectroscopic camera 1 comprises: a telecentric optical system 11 on which measuring object light is made incident; a wavelength variable interference filter 5 and a wavelength switching section 12 for taking out light having a predetermined wavelength from the incident light; and an imaging section 13 for receiving the light. The wavelength variable interference filter 5 comprises: a fixed substrate; a movable substrate disposed opposite to the fixed substrate; a fixed reflection film provided on the fixed substrate; a movable reflection film provided on the movable substrate and disposed opposite to the fixed reflection film via a gap between the reflection films; and an electrostatic actuator for changing a gap amount of the gap between the reflection films. The wavelength switching section 12 comprises: a plurality of band-pass filters having transmission wavelength ranges different from one another; and a filter switching circuit 18 for switching among the plurality of band-pass filters disposed in an optical path.

Description

  The present invention relates to a spectroscopic measurement apparatus including a wavelength variable interference filter that extracts light having a predetermined wavelength from incident light.

Conventionally, a wavelength variable interference filter is known in which a pair of reflecting films are opposed to each other, and only light of a predetermined wavelength that has been strengthened by multiple interference by the pair of reflecting films is transmitted or reflected among incident light (for example, patents) Reference 1).
The wavelength λ of light extracted by such a wavelength variable interference filter satisfies the condition shown in the following formula (1).

[Equation 1]
mλ = 2nd cos θ (1)

  In the formula (1), n is the refractive index of the medium between the reflective films (n = 1 in the case of air), and d is the distance between the reflective films. M is an order and takes an integer (m = 1, 2, 3,...). That is, the spectral characteristics of the wavelength tunable interference filter have a plurality of peak wavelengths having different orders m.

JP-A-1-94312

As shown in the above equation (1), when light in a wide wavelength band is incident on the wavelength tunable interference filter, light corresponding to a plurality of peak wavelengths is transmitted, and only light for a specific peak wavelength is transmitted. There was a problem that it would be inconvenient when extracting.
Further, in the wavelength variable interference filter, it is necessary to make light incident on each reflection film vertically. In particular, in a spectroscopic measurement device that acquires a spectral image using a wavelength variable interference filter, it is necessary to align the wavelength for each pixel with the wavelength of the spectral image that is desired to be acquired. However, there is a problem that the light is not extracted and the resolution is lowered.

  An object of this invention is to provide the spectrometer which can acquire the light of a desired wavelength with high resolution.

  The spectroscopic measurement apparatus according to the present invention includes a telecentric optical system into which light to be measured is incident, a wavelength variable interference filter that extracts light having a predetermined wavelength from light transmitted through the telecentric optical system, and a plurality of bandpass filters having different transmission wavelengths And a wavelength switching unit having the bandpass filter disposed in the optical path of the measurement target light, or filter switching means for taking out from the optical path, and the light transmitted through the wavelength tunable interference filter and the wavelength switching unit. And a light receiving portion for receiving light.

In the present invention, the measurement target light incident from the incident optical system is incident on the wavelength switching unit and the wavelength variable interference filter. Here, from the wavelength variable interference filter, as described above, peak wavelengths corresponding to a plurality of orders are extracted from the incident light. On the other hand, in the present invention, only the light that has passed through the bandpass filter disposed on the optical path in the wavelength switching unit is extracted from the extracted light of the plurality of peak wavelengths, and the light of other wavelengths is shielded. It becomes the composition to be done. Therefore, even if the incident light has a wide wavelength band, only light having a desired wavelength can be extracted.
In addition, the measurement target light incident on the wavelength tunable interference filter is guided to the wavelength tunable interference filter by the telecentric optical system. The telecentric optical system is an optical system having an exit pupil at infinity. In the light emitted from such a telecentric optical system, since the principal ray is parallel to the optical axis, it is possible to suppress a decrease in resolution in the wavelength variable interference filter.

In the spectroscopic measurement device of the present invention, the bandpass filter transmits a visible light bandpass filter that transmits a visible light region and blocks light in other wavelength regions, and transmits a near infrared region and transmits other wavelength regions. It is preferable to have a near-infrared high-pass filter for blocking.
According to the present invention, when a near-infrared high-pass filter is used, light having a peak wavelength appearing in the near-infrared region of the wavelength variable interference filter is transmitted and light having a peak wavelength appearing in the visible light region or the ultraviolet region is blocked. can do. When a visible light bandpass filter is used, light having a peak wavelength appearing in the visible light region of the wavelength variable interference filter can be transmitted, and light appearing in the near infrared region or ultraviolet region can be blocked.
That is, by controlling the wavelength switching unit and switching the band-pass filter disposed in the optical path, it is possible to measure the amounts of near-infrared light and visible light included in one measurement target light.

  In the spectrometer of the present invention, the wavelength tunable interference filter includes a first substrate, a second substrate disposed to face the first substrate, a first reflective film provided on the first substrate, A second reflection film provided on the second substrate and arranged to face the first reflection film via a gap between reflection films; and a gap amount changing unit that changes a gap amount of the gap between reflection films; It is preferable to provide.

  In the present invention, the variable wavelength interference filter has a configuration in which the first reflective film and the second reflective film are disposed on the first substrate and the second substrate, respectively, and the gap amount of the gap between the reflective films can be changed by the gap amount changing unit. It becomes. In such a configuration, the thickness dimension of the variable wavelength interference filter can be suppressed to the thickness dimension of the first substrate and the second substrate. Therefore, the configuration of the spectroscopic measurement apparatus can be simplified and downsized.

In the spectroscopic measurement apparatus of the present invention, it is preferable that the telecentric optical system is arranged to guide the principal ray of incident light perpendicularly to the surface of the first reflective film.
In the present invention, the principal ray of the incident light can be incident perpendicularly to the surface of the first reflective film by the telecentric optical system. Therefore, light having a desired wavelength corresponding to the gap amount of the gap between the reflection films can be accurately extracted from the wavelength variable interference filter, and accurate spectroscopic measurement can be performed. In addition, since the incident light can be incident perpendicularly to the first reflecting film regardless of the incident position (pixel position) of the incident light, a spectral image having a constant wavelength can be acquired regardless of the pixel position. Can do.

In the wavelength tunable interference filter according to the aspect of the invention, it is preferable that the telecentric optical system is disposed so as to guide a principal ray of incident light perpendicularly to a surface of the second reflective film.
In the present invention, the principal ray of the incident light can be incident perpendicularly to the surface of the second reflective film by the telecentric optical system. Therefore, also in the present invention, light having a desired wavelength corresponding to the gap amount of the gap between the reflection films can be accurately extracted from the wavelength variable interference filter, and accurate spectroscopic measurement can be performed. In addition, since the incident light can be incident perpendicularly to the first reflecting film regardless of the incident position (pixel position) of the incident light, a spectral image having a constant wavelength can be acquired regardless of the pixel position. Can do.

In the spectroscopic measurement apparatus of the present invention, it is preferable that the filter switching unit includes a moving unit that moves the bandpass filter in and out of an optical path and a switching circuit unit that controls the moving unit.
In the present invention, the bandpass filter can be easily moved in and out of the optical path by controlling the moving unit by the switching circuit unit. Therefore, the configuration can be simplified and the drive control of the bandpass filter can be simplified.

The figure which shows schematic structure of the spectroscopic camera of one Embodiment which concerns on this invention. The figure which shows the example of the optical path of the light guide | induced by the telecentric optical system of one Embodiment. The top view which shows schematic structure of the wavelength variable interference filter of one Embodiment. FIG. 4 is a cross-sectional view of the variable wavelength interference filter when FIG. The figure showing the transmittance | permeability characteristic of a visible light region band pass filter. The figure showing the transmittance | permeability characteristic of a near-infrared region high pass filter. The figure showing the spectral characteristic of the wavelength variable interference filter whose gap between reflection films is 610 nm. The figure showing the spectral characteristic of the wavelength variable interference filter whose gap between reflection films is 460 nm. The figure showing the spectral characteristic of the wavelength variable interference filter whose gap between reflection films is 380 nm.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings.
[Configuration of Spectrometer]
FIG. 1 is a diagram showing a schematic configuration of a spectroscopic camera 1 according to an embodiment of the present invention.
The spectroscopic camera 1 corresponds to the spectroscopic measurement apparatus of the present invention, and is an apparatus that acquires a spectroscopic image for each wavelength from measurement target light (image light) reflected by the object X.
As shown in FIG. 1, the spectroscopic camera 1 includes a telecentric optical system 11 (incident optical system), a wavelength switching unit 12, a wavelength variable interference filter 5, an imaging unit 13 (detection unit), and IV conversion. 14, an amplifier 15, an A / D converter 16, a voltage control circuit 17, a filter switching circuit 18, and a control circuit unit 20.

The imaging unit 13 receives the light transmitted through the wavelength variable interference filter 5 and outputs a detection signal (current) corresponding to the light intensity (light quantity) of the received light.
The IV converter 14 converts the detection signal input from the imaging unit 13 into a voltage value and outputs the voltage value to the amplifier 15.
The amplifier 15 amplifies a voltage (detection voltage) corresponding to the detection signal input from the IV converter 14.
The A / D converter 16 converts the detection voltage (analog signal) input from the amplifier 15 into a digital signal and outputs the digital signal to the control circuit unit 20.
The voltage control circuit 17 applies a voltage to an electrostatic actuator 56 (described later) of the wavelength variable interference filter 5 based on the control of the control circuit unit 20.

[Configuration of telecentric optical system]
FIG. 2 is a diagram illustrating an example of an optical path of light guided by the telecentric optical system 11. In FIG. 2, the wavelength switching unit 12 is omitted, but in practice, between the telecentric optical system 11 and the wavelength tunable interference filter 5, the visible light bandpass filter 121 or the near infrared band highpass filter 122 is used. Is arranged.

As shown in FIG. 2, the telecentric optical system 11 is composed of optical components such as a plurality of lenses.
The telecentric optical system 11 guides light incident from a range (field angle) that can be imaged by the spectroscopic camera 1 to the variable wavelength interference filter 5 through a plurality of lenses. At this time, the telecentric optical system 11 transmits the incident light so that the principal ray is parallel to the optical axis and orthogonal to the fixed reflection film 54 and the movable reflection film 55 of the wavelength variable interference filter 5 described later. Guide to the imaging unit 13.

Note that the orthogonality described here may be an angle that does not cause a shift in the peak wavelength of the transmitted light that has passed through the wavelength tunable interference filter 5. The peak wavelength of the transmitted light transmitted from the tunable interference filter 5 changes greatly as the amount of change in the incident angle increases. As the wavelength increases, the amount of fluctuation of the peak wavelength also increases. Therefore, in the lens design of the telecentric optical system 11, it may be set as appropriate depending on how much peak wavelength variation is allowed for the wavelength range desired to be transmitted by the variable wavelength interference filter 5.
For example, when light of 1100 nm is incident on the wavelength tunable interference filter 5, the peak wavelength fluctuates by 1 nm because the incident angle is shifted by 2.7 degrees. Therefore, when the wavelength variable interference filter 5 is used to split the wavelength region of 1100 nm or less, if the amount of fluctuation of the peak wavelength due to the incident angle of the principal ray is to be suppressed to 1 nm or less, the main flux of the light beam guided by the telecentric optical system 11 can be reduced. It is necessary to keep the tilt of the light beam within 2.7 degrees.

[Configuration of wavelength switching unit and imaging unit]
The wavelength switching unit 12 includes a visible light band-pass filter 121, a near-infrared band high-pass filter 122, a filter switching circuit 18, and a filter moving unit (not shown).
The visible light band-pass filter 121 and the near-infrared high-pass filter 122 are provided with a motor for moving in and out of the optical path (not shown), and the filter switching circuit 18 based on a signal from the control circuit unit 20 described later. By the control, the motor is driven to switch the filter disposed in the optical path.

FIG. 5 is a diagram showing the transmission characteristics of the visible light bandpass filter 121, and FIG. 6 is a diagram showing the transmission characteristics of the near-infrared band highpass filter 122.
As shown in FIG. 5, the visible light region bandpass filter 121 transmits light in the visible light region and blocks light in other wavelength regions. In the present embodiment, the visible light bandpass filter 121 has a transmission characteristic for light of 450 nm to 650 nm.
As shown in FIG. 6, the near-infrared high-pass filter 122 transmits light in the near-infrared region and blocks light in other wavelength regions. In the present embodiment, the near-infrared high-pass filter 122 has transmission characteristics for light from 760 nm to 1200 nm.
The transmission characteristics of the visible light band-pass filter 121 and the near-infrared band high-pass filter 122 shown in FIGS. 5 and 6 are examples in the present invention, and have transmission characteristics for other wavelength ranges. Also good. For example, a filter having transmission characteristics with respect to light in a wider wavelength band of about 360 nm to 700 nm may be used as the visible light bandpass filter 121.

The wavelength switching unit 12 may have any structure as long as it can switch between the visible light bandpass filter 121 and the near infrared highpass filter 122, which are bandpass filters.
For example, the wavelength switching unit 12 includes a rotating plate pivotally supported by a rotation driving unit so that the visible light band-pass filter 121 and the near-infrared band high-pass filter 122 are arranged on the rotating plate. Also good. That is, a configuration may be adopted in which the rotation plate is rotated by driving the rotation drive unit according to a signal from the control circuit unit 20 described later, and the filter disposed in the optical path is switched.

  The imaging unit 13 captures (detects) light (image light) emitted from the variable wavelength interference filter 5 and acquires a spectral image.

[Configuration of wavelength tunable interference filter]
Next, the wavelength variable interference filter 5 will be described with reference to the drawings.
FIG. 3 is a plan view showing a schematic configuration of the variable wavelength interference filter 5. 4 is a cross-sectional view of the variable wavelength interference filter 5 taken along the line IV-IV in FIG.
As shown in FIG. 3, the wavelength variable interference filter 5 is, for example, a rectangular plate-shaped optical member. As shown in FIG. 4, the variable wavelength interference filter 5 includes a fixed substrate 51 and a movable substrate 52. The fixed substrate 51 and the movable substrate 52 are each formed of, for example, various types of glass such as soda glass, crystalline glass, quartz glass, lead glass, potassium glass, borosilicate glass, and non-alkali glass, or crystal. . The fixed substrate 51 and the movable substrate 52 include a bonding film in which the first bonding portion 513 of the fixed substrate 51 and the second bonding portion 523 of the movable substrate are formed of, for example, a plasma polymerization film mainly containing siloxane. 53 (first bonding film 531 and second bonding film 532) are integrally formed by bonding.

The fixed substrate 51 is provided with a fixed reflective film 54 constituting the first reflective film of the present invention, and the movable substrate 52 is provided with a movable reflective film 55 constituting the second reflective film of the present invention. The fixed reflection film 54 and the movable reflection film 55 are disposed to face each other via the gap G1 between reflection films (the gap of the present invention). The wavelength variable interference filter 5 is provided with an electrostatic actuator 56 that is used to adjust (change) the gap amount of the inter-reflection film gap G1. The electrostatic actuator 56 corresponds to a gap amount changing unit in the present invention. The electrostatic actuator 56 includes a fixed electrode 561 provided on the fixed substrate 51 and a movable electrode 562 provided on the movable substrate 52. These fixed electrode 561 and movable electrode 562 are opposed to each other through an interelectrode gap G2. Here, the electrodes 561 and 562 may be provided directly on the substrate surfaces of the fixed substrate 51 and the movable substrate 52, respectively, or may be provided via other film members. Here, the gap amount of the inter-electrode gap G2 is larger than the gap amount of the inter-reflection film gap G1.
Further, in the filter plan view as shown in FIG. 3 in which the wavelength variable interference filter 5 is viewed from the thickness direction of the fixed substrate 51 (movable substrate 52), the plane center point O of the fixed substrate 51 and the movable substrate 52 is fixed reflection. It coincides with the center point of the film 54 and the movable reflective film 55 and coincides with the center point of the movable part 521 described later.
In the following description, the wavelength tunable interference filter 5 was seen from a plan view seen from the thickness direction of the fixed substrate 51 or the movable substrate 52, that is, from the stacking direction of the fixed substrate 51, the bonding film 53, and the movable substrate 52. The plan view is referred to as a filter plan view.

(Configuration of fixed substrate)
In the fixed substrate 51, an electrode arrangement groove 511 and a reflection film installation part 512 are formed by etching. The fixed substrate 51 is formed to have a thickness larger than that of the movable substrate 52, and the fixed substrate is caused by electrostatic attraction when a voltage is applied between the fixed electrode 561 and the movable electrode 562 or internal stress of the fixed electrode 561. There is no 51 deflection.
Further, a notch 514 is formed at the apex C1 of the fixed substrate 51, and a movable electrode pad 564P described later is exposed on the fixed substrate 51 side of the wavelength variable interference filter 5.

The electrode arrangement groove 511 is formed in an annular shape centering on the plane center point O of the fixed substrate 51 in the filter plan view. The reflection film installation part 512 is formed so as to protrude from the center part of the electrode arrangement groove 511 toward the movable substrate 52 in the plan view. The groove bottom surface of the electrode arrangement groove 511 is an electrode installation surface 511A on which the fixed electrode 561 is arranged. In addition, the protruding front end surface of the reflection film installation portion 512 is a reflection film installation surface 512A.
In addition, the fixed substrate 51 is provided with electrode extraction grooves 511B extending from the electrode arrangement grooves 511 toward the vertexes C1 and C2 of the outer peripheral edge of the fixed substrate 51.

A fixed electrode 561 is provided on the electrode installation surface 511 </ b> A of the electrode arrangement groove 511. More specifically, the fixed electrode 561 is provided in a region of the electrode installation surface 511 </ b> A that faces a movable electrode 562 of the movable portion 521 described later. In addition, an insulating film for ensuring insulation between the fixed electrode 561 and the movable electrode 562 may be stacked over the fixed electrode 561.
The fixed substrate 51 is provided with a fixed extraction electrode 563 extending from the outer peripheral edge of the fixed electrode 561 in the direction of the vertex C2. The extended leading end portion of the fixed extraction electrode 563 (portion located at the vertex C2 of the fixed substrate 51) constitutes a fixed electrode pad 563P connected to the control circuit unit 20.
In the present embodiment, a configuration in which one fixed electrode 561 is provided on the electrode installation surface 511A is shown. For example, a configuration in which two concentric circles centered on the plane center point O are provided (double electrode configuration). ) Etc.

As described above, the reflective film installation portion 512 is formed in a substantially cylindrical shape that is coaxial with the electrode arrangement groove 511 and has a smaller diameter than the electrode arrangement groove 511, and is formed on the movable substrate 52 of the reflection film installation portion 512. An opposing reflection film installation surface 512A is provided.
As shown in FIG. 4, a fixed reflection film 54 is installed in the reflection film installation portion 512. As the fixed reflective film 54, for example, a metal film such as Ag or an alloy film such as an Ag alloy can be used. For example, a dielectric multilayer film in which the high refractive layer is TiO ₂ and the low refractive layer is SiO ₂ may be used. Further, a reflective film in which a metal film (or alloy film) is laminated on a dielectric multilayer film, a reflective film in which a dielectric multilayer film is laminated on a metal film (or alloy film), a single refractive layer (TiO ₂ or SiO ₂₎ and a metal film (or alloy film) and the like may be used reflective film formed by laminating a.

  Further, an antireflection film may be formed at a position corresponding to the fixed reflection film 54 on the light incident surface of the fixed substrate 51 (the surface on which the fixed reflection film 54 is not provided). This antireflection film can be formed by alternately laminating low refractive index films and high refractive index films, and reduces the reflectance of visible light on the surface of the fixed substrate 51 and increases the transmittance.

  Of the surface of the fixed substrate 51 that faces the movable substrate 52, the surface on which the electrode placement groove 511, the reflective film installation portion 512, and the electrode extraction groove 511B are not formed by etching constitutes the first joint portion 513. The first bonding portion 513 is provided with a first bonding film 531. By bonding the first bonding film 531 to the second bonding film 532 provided on the movable substrate 52, as described above, The fixed substrate 51 and the movable substrate 52 are joined.

(Configuration of movable substrate)
The movable substrate 52 includes a circular movable portion 521 centered on the plane center point O in the filter plan view as shown in FIG. 3, a holding portion 522 that is coaxial with the movable portion 521 and holds the movable portion 521, A substrate outer peripheral portion 525 provided outside the holding portion 522.
Further, as shown in FIG. 3, the movable substrate 52 is formed with a notch 524 corresponding to the vertex C2, and when the wavelength variable interference filter 5 is viewed from the movable substrate 52 side, the fixed electrode pad is formed. 563P is exposed.

The movable part 521 is formed to have a thickness dimension larger than that of the holding part 522. For example, in this embodiment, the movable part 521 is formed to have the same dimension as the thickness dimension of the movable substrate 52. The movable portion 521 is formed to have a diameter larger than at least the diameter of the outer peripheral edge of the reflection film installation surface 512A in the filter plan view. The movable part 521 is provided with a movable electrode 562 and a movable reflective film 55.
Similar to the fixed substrate 51, an antireflection film may be formed on the surface of the movable portion 521 opposite to the fixed substrate 51. Such an antireflection film can be formed by alternately laminating a low refractive index film and a high refractive index film, reducing the reflectance of visible light on the surface of the movable substrate 52 and increasing the transmittance. Can be made.

The movable electrode 562 is opposed to the fixed electrode 561 through the inter-electrode gap G2, and is formed in an annular shape having the same shape as the fixed electrode 561. In addition, the movable substrate 52 includes a movable extraction electrode 564 that extends from the outer peripheral edge of the movable electrode 562 toward the vertex C <b> 1 of the movable substrate 52. The extended leading end portion of the movable extraction electrode 564 (the portion located at the vertex C1 of the movable substrate 52) constitutes a movable electrode pad 564P connected to the control circuit unit 20.
The movable reflective film 55 is provided at the center of the movable surface 521A of the movable part 521 so as to face the fixed reflective film 54 with the gap G1 between the reflective films. As the movable reflective film 55, a reflective film having the same configuration as that of the fixed reflective film 54 described above is used.
In the present embodiment, as described above, an example in which the gap amount of the interelectrode gap G2 is larger than the gap amount of the inter-reflection film gap G1 is shown, but the present invention is not limited to this. For example, when using infrared rays or far infrared rays as the measurement target light, the gap amount of the reflection film gap G1 may be larger than the gap amount of the interelectrode gap G2 depending on the wavelength range of the measurement target light.

The holding part 522 is a diaphragm that surrounds the periphery of the movable part 521, and has a thickness dimension smaller than that of the movable part 521. Such a holding part 522 is easier to bend than the movable part 521, and the movable part 521 can be displaced toward the fixed substrate 51 by a slight electrostatic attraction. At this time, since the movable portion 521 has a thickness dimension larger than that of the holding portion 522 and becomes rigid, even when the holding portion 522 is pulled toward the fixed substrate 51 by electrostatic attraction, the shape of the movable portion 521 changes. Absent. Therefore, the movable reflective film 55 provided on the movable portion 521 is not bent, and the fixed reflective film 54 and the movable reflective film 55 can be always maintained in a parallel state.
In this embodiment, the diaphragm-like holding part 522 is illustrated, but the present invention is not limited to this. For example, a configuration in which beam-like holding parts arranged at equiangular intervals around the plane center point O are provided. And so on.

  As described above, the substrate outer peripheral portion 525 is provided outside the holding portion 522 in the filter plan view. The surface of the substrate outer peripheral portion 525 that faces the fixed substrate 51 includes a second joint portion 523 that faces the first joint portion 513. The second bonding portion 523 is provided with the second bonding film 532. As described above, the second bonding film 532 is bonded to the first bonding film 531, so that the fixed substrate 51 and the movable substrate 52 are bonded. Are joined.

[Operation of tunable interference filter]
In the wavelength variable interference filter 5 as described above, the fixed electrode pad 563P and the movable electrode pad 564P are connected to the control circuit unit 20 described later via the voltage control circuit 17, respectively.
Therefore, when the control circuit unit 20 applies a voltage between the fixed electrode 561 and the movable electrode 562 via the fixed electrode pad 563P and the movable electrode pad 564P, the movable unit 521 is moved to the fixed substrate 51 side by electrostatic attraction. It is displaced to. Thereby, it is possible to change the gap amount of the gap G1 between the reflection films to a predetermined amount.

  Further, as described above, the light incident on the wavelength tunable interference filter 5 by the telecentric optical system 11 is orthogonal to the surfaces of the fixed reflection film 54 and the movable reflection film 55, and the chief ray is relative to the optical axis. Parallel. Therefore, the angle of the incident light does not change depending on the position (pixel position) in the plane of the fixed reflective film 54 or the movable reflective film 55. For this reason, it is possible to extract light of a desired measurement target wavelength based on the gap amount of the gap G1 between the reflection films, regardless of the pixel position of the measurement target light (image light). Thereby, the imaging unit 13 can capture a spectral image corresponding to the wavelength to be measured.

[Configuration of control circuit section]
Returning to FIG. 1, the control circuit unit 20 of the spectroscopic camera 1 will be described.
The control circuit unit 20 is configured by combining, for example, a CPU and a memory, and controls the overall operation of the spectroscopic camera 1. As illustrated in FIG. 1, the control circuit unit 20 includes a band pass filter switching unit 21, a filter driving unit 22, and a captured image acquisition unit 23.
In addition, the control circuit unit 20 includes a storage unit (not shown) that stores various data, and the storage unit stores the wavelength variable interference filter for the drive voltage applied to the electrostatic actuator 56 of the wavelength variable interference filter 5. V-λ data indicating the relationship of the wavelength of light transmitted through 5 is stored.

  The band-pass filter switching unit 21 controls the motors provided in the visible light band-pass filter 121 and the near-infrared high-pass filter 122 by sending a signal to the filter switching circuit 18 of the wavelength switching unit 12, and enters the optical path. The filters 121 and 122 to be arranged are switched.

The filter drive unit 22 sequentially switches the voltage applied to the electrostatic actuator 56 of the wavelength variable interference filter 5 based on the V-λ data stored in the storage unit, and the wavelength of the light transmitted through the wavelength variable interference filter 5 Switch sequentially.
The captured image acquisition unit 23 acquires a captured image (spectral image) captured by the imaging unit 13.

[Spectral image acquisition method]
Next, a method for acquiring a spectral image by the spectral camera 1 as described above will be described with a specific example.
The spectroscopic camera 1 performs a manual imaging process for acquiring a spectral image of a desired wavelength according to an operation of an operator and an automatic imaging process for automatically acquiring a spectral image corresponding to a plurality of wavelengths for an imaging target.
First, acquisition of a spectral image by manual imaging processing will be described.
When the wavelength of the spectral image to be picked up by the operator is designated, the filter driving unit 22 sets the voltage to be applied to the wavelength variable interference filter 5 based on the V-λ data stored in the storage unit. Thereby, the voltage set to the electrostatic actuator 56 of the wavelength variable interference filter 5 is applied from the voltage control circuit 17, and the gap amount of the gap G1 between the reflection films is set to a predetermined value.
In addition, the band pass filter switching unit 21 controls the filter switching circuit 18 so that one of the visible light band-pass filter 121 and the near-infrared high-pass filter 122 having transmission characteristics with respect to a specified wavelength is an optical path. Place in.

For example, when a red (610 nm) spectral image is acquired, the gap amount of the gap G1 between the reflection films is set to 610 nm. FIG. 7 is a diagram showing the spectral characteristics of the wavelength tunable interference filter 5 when the gap amount of the reflection film gap G1 is set to 610 nm.
As shown in FIG. 7, in this example, in the spectral characteristics of the tunable interference filter 5, the primary peak wavelength appears near 1220 nm, the secondary peak wavelength appears near 610 nm, and the tertiary peak wavelength appears near 406 nm. appear. In this case, by blocking the light having the primary peak wavelength and the tertiary peak wavelength from the light incident on the wavelength tunable interference filter 5, the light having the target secondary peak wavelength (610 nm) is transmitted from the wavelength tunable interference filter 5. It is injected. That is, in this example, the bandpass filter switching unit 21 arranges a visible light bandpass filter 121 having spectral characteristics with respect to light of 450 nm to 650 nm as shown in FIG. 5 in the optical path. Thereby, the light of a primary peak wavelength and the light of a tertiary peak wavelength can be interrupted | blocked, and the spectral image with respect to a secondary peak wavelength (red light) can be imaged in the imaging part 13. FIG.

For example, when acquiring a blue (460 nm) spectral image, the gap amount of the gap G1 between the reflection films is set to 460 nm. FIG. 8 is a diagram showing the spectral characteristics of the wavelength tunable interference filter 5 when the gap amount of the reflection film gap G1 is set to 460 nm.
As shown in FIG. 8, in the case of this example, in the spectral characteristics of the tunable interference filter 5, the primary peak wavelength appears near 920 nm, and the secondary peak wavelength appears near 460 nm. In this case, the light of the primary peak wavelength (460 nm) is emitted from the wavelength variable interference filter 5 by blocking the light of the primary peak wavelength from the light incident on the wavelength variable interference filter 5. That is, in this example, the bandpass filter switching unit 21 arranges a visible light bandpass filter 121 having spectral characteristics with respect to light of 450 nm to 650 nm as shown in FIG. 5 in the optical path. Thereby, the light of a primary peak wavelength can be interrupted | blocked and the spectral image with respect to a secondary peak wavelength (blue light) can be imaged in the imaging part 13. FIG.

Furthermore, for example, when acquiring near-infrared light having a wavelength of 760 nm, the gap amount of the inter-reflection film gap G1 is set to 380 nm. FIG. 9 is a diagram showing the spectral characteristics of the wavelength tunable interference filter 5 when the gap amount of the inter-reflective film gap G1 is set to 380 nm.
As shown in FIG. 9, in the case of this example, in the spectral characteristics of the wavelength tunable interference filter 5, the primary peak wavelength appears near 760 nm and the secondary peak wavelength appears near 380 nm. Here, the light with a wavelength of 760 nm is the light with the shortest wavelength that can be transmitted when the near-infrared high-pass filter 122 shown in FIG. 6 is used. Therefore, the band pass filter switching unit 21 can transmit the light of 760 nm which is the primary peak wavelength and block the light after the secondary peak wavelength by arranging the near infrared region high pass filter 122 in the optical path. it can. Thereby, the imaging unit 13 can capture a spectral image for the primary peak wavelength (760 nm).

Next, an automatic imaging process for automatically acquiring a spectral image of each wavelength from the visible light region to the near infrared region will be described below.
In the automatic imaging process, the filter drive unit 22 sequentially switches the voltage applied to the electrostatic actuator 56 of the wavelength variable interference filter 5 and sequentially switches the light having the peak wavelength that passes through the wavelength variable interference filter 5. The bandpass filter switching unit 21 controls the bandpass filter switching unit 21 every time the voltage applied to the electrostatic actuator 56 is switched by the filter driving unit 22, so that the visible light bandpass filter 121 is included in the optical path. And a state in which the near-infrared high-pass filter 122 is disposed are alternately switched.
Thereby, it is possible to acquire light of two peak wavelengths each time the gap amount of the gap G1 between the reflection films in the wavelength variable interference filter 5 is changed. For example, as shown in FIG. 7, when the gap amount of the reflection film gap G <b> 1 is set to 610 nm, the imaging unit 13 has a secondary peak in a state where the visible light bandpass filter 121 is arranged in the optical path. A spectral image corresponding to the wavelength (610 nm) can be taken. Moreover, in a state where the near-infrared high-pass filter 122 is disposed in the optical path, the imaging unit 13 can capture a spectral image corresponding to the primary peak wavelength (1220 nm).

[Effects of Embodiment]
In the spectroscopic camera 1 of the present embodiment, a telecentric optical system 11 is used as an incident optical system that guides light to the wavelength variable interference filter 5, and the incident measurement target light (image light) is a fixed reflection film of the wavelength variable interference filter 5. 54 and the movable reflective film 55 are always incident perpendicularly. For this reason, the image light transmitted through the wavelength variable interference filter 5 becomes image light having the same wavelength in each pixel, and a spectral image corresponding to the desired wavelength can be taken.
Further, the wavelength switching unit 12 switches between a state in which the visible light bandpass filter 121 is disposed in the optical path and a state in which the near-infrared band highpass filter 122 is disposed. Therefore, even when the wavelength variable interference filter 5 has a plurality of peak wavelengths as the spectral characteristics, the wavelength switching unit 12 extracts a specific peak wavelength corresponding to the bandpass filter arranged in the optical path, Light of peak wavelength can be shielded. Thereby, even when light having a wide wavelength band of, for example, about 450 nm to 1300 nm is incident as measurement target light (image light), a spectral image corresponding to a specific peak wavelength can be captured.

  Further, in the present embodiment, the bandpass filter transmits the visible light band and blocks the light in the other wavelength range, and the visible light bandpass filter 121 that transmits the near-infrared band and blocks the other wavelength range. And a near infrared region high-pass filter 122. Generally, when the gap between the reflective films of the wavelength variable interference filter 5 is controlled so that visible light is transmitted as the secondary peak wavelength, light in the near infrared region is transmitted as the primary peak wavelength. Here, by using the visible light bandpass filter 121, the primary peak wavelength of light in the near infrared region can be blocked, and by using the near infrared region highpass filter 122, the secondary peak in the visible light region. Wavelength can be cut off. As described above, in the present embodiment, the wavelength switching unit 12 is controlled to switch the bandpass filter disposed in the optical path, whereby the near-infrared spectrum is obtained from one measurement target light (image light). An image and a spectral image in the visible light range can be taken respectively.

  The wavelength switching unit 12 includes a visible light band-pass filter 121, a near-infrared band high-pass filter 122, a filter switching circuit 18, and a filter moving unit. Then, the filter switching circuit 18 drives the filter moving unit based on the signal from the bandpass filter switching unit 21, so that the bandpass filter (visible light bandpass filter 121 or near red) disposed in the optical path is driven. The outer high pass filter 122) is switched. In such a configuration, the configuration of the wavelength switching unit 12 can be simplified, and the peak wavelength extracted from the wavelength tunable interference filter 5 can be easily switched simply by driving the moving unit.

[Modification]
It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.

For example, in the above-described embodiment, the visible light bandpass filter 121 and the near-infrared band highpass filter 122 are illustrated as the bandpass filters, but the present invention is not limited to this. As the band-pass filter in the present invention, any filter may be used as long as it transmits light in a specific wavelength range and can block light in other wavelength ranges. For example, in addition to the visible light bandpass filter 121 and the near-infrared highpass filter 122, the wavelength switching unit 12 may further include a lowpass filter that transmits the ultraviolet region and blocks light in other wavelength regions. Good. In such a configuration, an ultraviolet spectral image can be acquired by providing an imaging device having sensitivity to ultraviolet light as the imaging unit 13.
Moreover, although the example using one visible light range band pass filter 121 was shown, it is good also as a structure which uses a blue filter, a green filter, and a red filter, for example. In this case, for example, even when the interval between the peak wavelengths of the light transmitted through the wavelength variable interference filter 5 is narrow (when the third-order peak wavelength or the fourth-order peak wavelength appears in the visible light region), the desired peak wavelength is obtained. A corresponding spectral image can be acquired.

Moreover, in the said embodiment, although it was set as the structure which makes the light which permeate | transmitted the wavelength switch part 12 inject into the wavelength variable interference filter 5, it is not limited to this. The wavelength switching unit 12 in the present invention may be arranged at any position on the optical path in the spectroscopic camera 1. For example, the wavelength switching unit 12 may be disposed between the wavelength variable interference filter 5 and the imaging unit 13. In this case, light having a plurality of peak wavelengths is transmitted from the wavelength variable interference filter 5, but light other than the desired wavelength can be blocked by the filter of the wavelength switching unit 12 in the subsequent stage.
In addition, as the arrangement position of the wavelength switching unit 12, a configuration in which the wavelength switching unit 12 is arranged between a plurality of lenses constituting the telecentric optical system 11 or a configuration provided in front of the incident optical system may be employed.

In each of the above embodiments, the electrostatic actuator 56 that varies the gap amount of the inter-reflective film gap G1 by electrostatic attraction by applying a voltage is exemplified as the gap amount changing unit of the wavelength variable interference filter 5. However, the present invention is not limited to this.
For example, instead of the fixed electrode 561, a first dielectric coil may be arranged, and a dielectric actuator in which a second dielectric coil or a permanent magnet is arranged instead of the movable electrode 562 may be used.
Further, a piezoelectric actuator may be used instead of the electrostatic actuator 56. In this case, for example, the lower electrode layer, the piezoelectric film, and the upper electrode layer are stacked on the holding unit 522, and the voltage applied between the lower electrode layer and the upper electrode layer is changed as an input value, so that the piezoelectric film is expanded and contracted. Thus, the holding portion 522 can be bent.

  Further, although the spectroscopic camera 1 is illustrated as the spectroscopic measurement apparatus of the present invention, the present invention can also be applied to a colorimetry apparatus that measures the color of the measurement target light incident on the incident optical system.

  In addition, the specific structure for carrying out the present invention can be appropriately changed to other structures and the like within a range in which the object of the present invention can be achieved.

  DESCRIPTION OF SYMBOLS 5 ... Variable wavelength interference filter, 11 ... Telecentric optical system (incident optical system), 12 ... Wavelength switching unit, 13 ... Imaging unit (light receiving unit), 18 ... Filter switching circuit, 51 ... Fixed substrate (first substrate), 52 ... movable substrate (second substrate), 54 ... fixed reflective film (first reflective film), 55 ... movable reflective film (second reflective film), 56 ... electrostatic actuator (gap amount changing unit), 121 ... visible light region Band pass filter (band pass filter), 122... Near infrared region high pass filter (band pass filter).

Claims (6)

A telecentric optical system into which light to be measured is incident;
A variable wavelength interference filter for extracting light of a predetermined wavelength from the light transmitted through the telecentric optical system;
A wavelength switching unit having a plurality of bandpass filters having different transmission wavelengths, and a filter switching unit that arranges the bandpass filter in the optical path of the measurement target light, or extracts the optical signal from the optical path;
A light receiving unit that receives light transmitted through the wavelength variable interference filter and the wavelength switching unit;
A spectroscopic measurement device comprising: The spectroscopic measurement device according to claim 1,
The bandpass filter includes a visible light bandpass filter that transmits the visible light region and blocks light in other wavelength regions, and a near infrared region highpass filter that transmits the near infrared region and blocks other wavelength regions. A spectroscopic measurement device comprising: The spectroscopic measurement device according to claim 1 or 2,
The wavelength variable interference filter is:
A first substrate;
A second substrate disposed opposite the first substrate;
A first reflective film provided on the first substrate;
A second reflective film provided on the second substrate and disposed opposite the first reflective film with a gap between the reflective films;
A gap amount changing unit that changes a gap amount of the gap between the reflective films;
A spectroscopic measurement device comprising: The spectrometer according to claim 3,
The said telecentric optical system is arrange | positioned so that the principal ray of incident light may be guide | induced perpendicularly | vertically with respect to the surface of said 1st reflective film. In the spectroscopic measurement device according to claim 3 or 4,
The said telecentric optical system is arrange | positioned so that the chief ray of incident light may be guide | induced perpendicularly | vertically with respect to the surface of said 2nd reflective film. In the spectroscopic measurement device according to any one of claims 1 to 5,
The spectroscopic measurement apparatus, wherein the filter switching unit includes a moving unit that moves the bandpass filter in and out of an optical path, and a switching circuit unit that controls the moving unit.

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