KR101154714B1 - Planar spectrometer - Google Patents

Abstract

The present invention relates to a flat plate spectroscope, wherein, in a flat plate spectrometer having a plate light guide plate and a plate diffraction grating, at least one reflective mirror having a concave reflection surface is provided at an edge region of the plate light guide plate. By reflecting the light incident on the flat light guide plate through the reflective surface to converge in the direction of the flat diffraction grating, the optical alignment is simple, miniaturization is possible, and the effect of making a low cost spectrometer easily have.

Spectrometer, concave reflecting mirror, light guide plate, non-uniform diffraction grating

Description

Flat Spectrometer {PLANAR SPECTROMETER}

The present invention relates to a flat plate spectrometer, and more particularly, to a flat plate spectrometer capable of spectroscopically incident light of a point light source using one concave reflection mirror and a diffraction grating to form an image as output light of a point light source.

In general, the spectrometer has a wide range of applications. Among them, the spectrometer can be used for fruit sugar selector, etc. Since fruit sugar selector was first imported into Korea in 1996, it has been used for fruit size, color and sugar selection in large agricultural bakery since the late 1990s.

On the other hand, domestic universities and research institutes have conducted the study of predicting sugar and acidity by spectroscopic measurement using precision spectrophotometer on several fruits.In the Rural Agricultural Research Institute of Korea, the sugar and acidity of citrus fruits and potatoes are used as rural supply type. An online confectionery was developed to measure.

The developed conveyor for conveyors is equipped with 300W halogen lamps and on-line spectroscopy (CCD) sensor, which measures the absorption scattering spectrum of the shipped fruit in real time and uses sugar regression (PLSR) to measure sugar and acidity. Predict and classify

Since then, the online snacks have been extended to pears, apples, peaches, and citrus fruits, and have been distributed to about 30 agricultural cooperatives and crop groups around the country. In addition, since the sugar content system has been developed into mobile and portable devices that can be utilized on-site in production farms and distribution markets, etc., it has already begun to be marketed in Japan.

Such portable devices can be applied not only to sugar meters but also to various light sensor technologies such as environment, health care, and quality control. In addition, portable devices require additional features such as miniaturization, low cost, impact resistance, low power consumption and convenience. Therefore, the technology of low cost, miniaturization and impact resistance is very important in the current spectrometer market.

The small spectrometers currently developed have almost a diffraction grating type. Until now, most spectrometers have used a method in which parallel light is incident on a flat diffraction grating having a uniform lattice period. In this method, a point light source (or light of an input slit) incident and diverging to a spectrometer is converted into parallel light by, for example, a mirror or a lens, and then diffracted by a diffraction grating and then converged by using a mirror or a lens. By forming an image on the output point light source (or output slit), the wavelength is separated.

This method is used in optical systems such as Zeiss and Ocean Optics, which uses two concave mirrors and a holographic diffraction grating to separate the wavelength in three-dimensional space. Free space optics have been developed. However, these techniques can obtain excellent spectral characteristics by constructing sophisticated diffraction gratings and optical mirrors in free space, but the size of the spectrometer is large, expensive, and weak in impact. Therefore, optical alignment is complicated, miniaturization and mass production are difficult, and it is disadvantageous for low cost.

Accordingly, Hamamatsu Co., Ltd. has developed a spectroscopic optical system that compensates for these shortcomings and uses an optical glass as an optical medium. The spectroscopic optical system has a structure in which a free space is replaced with glass as an optical medium and a concave mirror and a hologram grating are combined with the glass. However, this product is excellent in impact resistance and wavelength resolution but is rather inconvenient to be widely applied to integrated microscopic optical sensors such as bio and medical.

On the other hand, as another method of forming a spectroscopic optical system, there is a method using a two-dimensional planar optical system, for example, by using only one concave reflector shaped diffraction grating having a uniform lattice period (e.g., a Roland grating). And a method of constituting an optical system. In this method, since the diffraction grating is concave, the optical system is very simple since the imaging and diffraction spectroscopy are simultaneously performed on the incident or exit point light source (or slit).

Representative technologies for such planar optics include a spectrometer from Germany's Beringer Ingelheim (microparts), developed for use in portable biosensors or health care. This spectrometer uses LIGA technology to process concave reflection gratings on the cross-section of a planar PMMA optical waveguide and couples the PD-array to the optical waveguide. To configure. The PMA optical waveguide is made by spin coating on a silicon substrate, and the diffraction grating is fabricated using LIGA technology, which is easy to mass produce. However, a spectrometer using LIGA technology has a disadvantage in that resolution is one of the important characteristics of the spectrometer. The reason for this is that the diffraction grating manufactured by LIGA technology exhibits unstable characteristics of the optical medium by using a polymer material that is less accurate in its geometric shape and that the refractive index changes significantly with temperature change. In addition, it is difficult to produce a diffraction grating on a concave surface, and the diffraction grating is relatively expensive.

Accordingly, in order to manufacture a compact and inexpensive spectrometer, a planar diffraction grating is used for a two-dimensional flat plate optical system. A spectrometer using a two-dimensional flat plate optical system is generally implemented using a uniform planar diffraction grating. Recently, however, there has been a great deal of interest in non-uniform gratings (eg, gratings that use holograms to converge spectroscopy to a point or computer generated holograms) that can make an incident light source an exit light source without a mirror or lens. This is concentrated.

In other words, by implementing a spectrometer using a flat diffraction grating having a non-uniform lattice spacing, it is possible to properly design the diffraction grating so that the divergent light of the point light source is diffracted at the diffraction grating and converges to different points according to the wavelength of the incident light. .

This concept can be explained with reference to FIG. 1, which is a cross-sectional view for describing a spectrometer implemented by a conventional plate-type rotary grating. Referring to FIG. 1, light having a wavelength λ from the optical fiber 100 is incident on an appropriately designed diffraction grating 110 while spreading, and the diffraction grating is designed to converge the light to an appropriate point 120.

When the wavelength of the incident light varies from λ to another wavelength, λ ', the point of convergence (hereinafter, the point of convergence), that is, the position of the focus, can be estimated by calculation. This calculation can be done using the well-known Fresnel-Kirchhoff equation, where the diffracted light in each grating of the diffraction grating 110 produces a location where a certain constructive interference occurs at a certain point. Will be found.

FIG. 2 is a graph for explaining a movement trajectory of a convergence point position according to a change in light wavelength estimated by a Fresnel-Kirchhoff equation in a conventional spectrometer. Referring to FIG. 2, a position 200 at which light converges at a wavelength of 1.0 μm and a position 210 at which light converges at a wavelength of 1.5 μm can be seen, and points between the two positions 200 and 210 are 1.0 μm. Represent the locations where light of larger and smaller wavelengths of less than 1.5 μm converge. As the wavelength changes, each wavelength converges at its respective location 220, shown by the dotted line.

As can be seen in FIG. 2, when the diffraction grating 110 is properly designed, even when light is incident on the diffraction grating 110 directly from the point light source or the optical fiber 100, the diffraction grating 110 may converge to different points depending on the wavelength.

However, in this case, the angle A of the trajectory 220 formed by the position of the convergence points according to the wavelength is very large with the line 230 parallel to the line where the diffraction grating is located. In other words, the distance to the convergence points varies greatly. At this time, for example, when the optical system of the spectrometer is located in a flat light guide plate having a larger refractive index than air, and the light receiving element is located outside the light guide plate, the focused light does not escape to the outside of the light guide plate by total internal reflection of the light guide plate and reaches the light receiving element. The problem is that you can't.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a flat spectrometer that can easily produce an unbalanced diffraction grating for increasing the spectroscopic efficiency of the spectrometer.

Another object of the present invention is to provide a plate-type spectrometer that is simple in optical alignment, miniaturized, and can be simply manufactured at low cost.

In order to achieve the above object, a first aspect of the present invention is a flat plate spectrometer having a plate light guide plate and a plate diffraction grating, the at least one having a reflective surface concave in the edge region of the plate light guide plate A reflective mirror is provided, and reflects the light incident on the flat light guide plate through the reflective surface to converge in the direction of the flat diffraction grating to provide a flat spectroscope.

The planar spectrometer further includes an optical fiber capable of injecting light into the planar light guide plate and a light receiving element provided at a predetermined region of the end of the planar light guide plate on which light diffracted by the planar diffraction grating converges. desirable.

Preferably, the light receiving element is formed on a predetermined cross section of the flat light guide plate so as to face each other with the flat diffraction grating, or a 45 ° inclined plane is formed on a predetermined cross section of the flat light guide plate facing the flat diffraction grating. The light diffracted light may be formed in a predetermined region of an upper surface of the flat light guide plate which is reflected and emitted from the 45 ° inclined plane.

Preferably, the flat light guide plate has a constant thickness of 0.5 to 1.5 mm, and may be formed to have a larger refractive index than air.

Preferably, the planar light guide plate may be formed of a quartz glass substrate or a sodium-borosilicate glass substrate.

Preferably, the reflective mirror may be in the form of a curved surface or a non-curved surface having a predetermined radius of curvature.

Preferably, the reflecting mirror may have an aluminum or silver coated reflecting surface.

Preferably, the plate-shaped diffraction grating may have a non-uniform lattice spacing such that the diffraction angle according to the wavelength of light reflected by the reflection mirror may be continuously varied.

Preferably, the flat diffraction grating may be formed by a process such as holographic exposure or photolithography.

Preferably, the flat diffraction grating is formed of a silicon substrate having a (1, x, x) plane and the asymmetry of the diffraction grating acid is controlled by an x value, but the x value may be 0 or 1.

According to the flat spectroscope of the present invention as described above, by using a flat light guide plate and a flat diffraction grating as an optical medium there is an advantage that the mass production of the spectroscope is easy and the manufacturing cost can be reduced.

In addition, according to the present invention, by processing the input light in a two-dimensional flat light guide plate instead of a three-dimensional space there is an advantage that the mass production is easy, the spectrometer can be miniaturized and the resolution can be effectively adjusted.

In addition, according to the present invention, the optical properties of the spectrometer are stabilized and the reliability is improved by forming a flat light guide plate using a quartz glass material, and the mass diffraction grating is easily formed by using a photomask technology. have.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

3 is a perspective view illustrating a flat spectroscope according to an embodiment of the present invention.

Referring to FIG. 3, the planar spectrometer according to an exemplary embodiment of the present invention is distributed according to the planar light guide plate 300, the reflecting mirror 310, the planar diffraction grating 320, the optical fiber 330, and the wavelength. It includes a light receiving element 340 capable of detecting light.

The planar light guide plate 300 may be formed by a quartz wafer or a glass plate material having a predetermined thickness, for example, a quartz glass substrate or a sodium-borosilicate (Pyrex or Borofloat) glass substrate. It is possible to be formed by.

At this time, for example, the coefficient of thermal expansion of the sodium-borosilicate glass is almost the same as the coefficient of thermal expansion (about 3 × 10 ⁻⁶ ) of silicon used as the material of the flat diffraction grating 320 so that the diffraction grating can be adhered to the glass plate. It can minimize the stress that occurs when. Also, for example, the coefficient of thermal expansion of quartz glass is about 0.5 × 10 ⁻⁶ , which is somewhat different from that of silicon, but is advantageous in the construction of an optical system as a high quality optical material.

The flat light guide plate 300 has a refractive index value greater than that of air. Therefore, properly incident light propagates along the flat light guide plate 300 by the internal reflection principle.

Hereinafter, the planar light guide plate 300 according to an exemplary embodiment of the present invention will be described using a quartz wafer having a well known refractive index. Of course, it is also possible to use other light guide plate materials other than quartz wafers as long as they are not limited thereto and can be applied to an embodiment of the present invention.

On the other hand, the upper and lower surfaces of the planar light guide plate 300 may be laminated with a low refractive coating film such as optical polymer or spin-on-glass (SOG), for example, due to contamination This will prevent scattering and help total reflection. In addition, the upper portion of the low refractive coating layer may be laminated with the high refractive coating layer again, for example, by collecting scattering or stray light generated in the flat light guide plate 300, such scattering or stray light as the noise to the optical sensor train It is possible to prevent the incident.

The reflective mirror 310 may be formed with a concave reflective surface in a predetermined region of the edge end of the flat light guide plate 300. For example, a predetermined region of the edge end of the flat light guide plate 300 may be formed by being polished in the form of an arc or the like and then coated with optical reflection, and one or two or more reflective mirrors 310 may be formed. In order to downsize the spectrometer, it is preferable that one reflection mirror 310 is formed.

In this case, the reflective surface may be coated by, for example, a metal or a dielectric such as silver or aluminum, or a multilayer thin film formed thereof. Such a reflective surface may be formed, for example, in the form of a curved surface having a constant radius of curvature or in the form of a non-curved surface, but is not limited thereto.

On the other hand, the light reflected through the reflective mirror 310 is incident on the flat diffraction grating 320. The flat diffraction grating 320 typically has a non-uniform lattice spacing, ie a variable lattice spacing. This lattice spacing is determined by, for example, calculating the period of the lattice so that light according to the wavelength is collected along a specific point (for example, an output slit or output point light source) in determining the lattice spacing of the flat diffraction grating 320. Therefore, the flat diffraction grating applied to the present invention is also referred to as a computer generated hologram (CGH) diffraction grating, for example.

In this case, the specific points are areas in which the planar spectrometer according to an embodiment of the present invention connects the points where light is transmitted by decomposing the wavelength, and these points are positioned according to the design of the planar diffraction grating 320. Can vary. On the other hand, for example, a photodiode (PD) is formed at the specific point, or an optical fiber block is formed to extract light separated by wavelength.

The flat diffraction grating 320 may be formed by directly exposing, for example, a hologram exposure method, or may be formed through a process such as photolithography. When the photolithography process is used, for example, a mask pattern is formed on a silicon wafer or the like. It may then be formed by wet etching.

The method of forming the flat diffraction grating 320 will be described in more detail, for example, by exposing the silicon substrate to the [110] direction by, for example, a photolithography process such as a CGH mask or hologram exposure described above. For example, it may be formed by etching using an anisotropic wet etching solution such as potassium hydroxide (KOH) to form a lattice groove line having a (111) plane on the silicon substrate. At this time, the silicon substrate is a substrate in the (1, x, x) direction made by cutting a silicon single crystal ingot in a specific slope, 'x' is a value from 0 to 1.

In addition, the shape of the grating may vary depending on the 'x' value and may form a blazed grating. The inclination angle of the flat diffraction grating 320 may be determined such that the incident light and the diffracted light have a reflection law at the grating plane so that the grating has the maximum diffraction efficiency at the designed order and wavelength.

In addition, in the formation of a grating using, for example, a mask as described above, a flat surface having a predetermined width formed by an etching mask is formed on the upper part of the lattice, and to reduce the width, for example, a phase mask or an electron beam exposure method. And the like can be used.

In addition, the flat diffraction grating 320 may be fixed to an appropriate position of the flat light guide plate 300 through, for example, epoxy.

The optical fiber 330 is formed at a predetermined cross section of the end of the flat light guide plate 300 to inject light into the light guide plate. For example, a low numerical aperture optical fiber 330 may be used.

(여기서,

은 도광판 또는 광섬유의 굴절률)인 광섬유 또는 광섬유 블록일 수 있다. 또한 예컨대, 평판형 도광판(300)에 수직한 방향 성분의 입사광이 크지 않아서 평판형 회절격자(320)에서 원추형 회절(Conical Diffraction)을 무시할 수 있을 정도의 NA값을 갖는 광섬유 또는 광섬유 블록일 수 있다.Here, the low numerical aperture optical fiber is, for example, the numerical aperture of the light emitted from the optical fiber or the optical fiber block (ie, the lens assembly or core diffusion optical fiber, etc. attached to the optical fiber terminal) or the light incident to the planar light guide plate 300. Numerical aperture

(here,

May be an optical fiber or an optical fiber block). Also, for example, since the incident light of a direction component perpendicular to the planar light guide plate 300 is not large, the planar diffraction grating 320 may be an optical fiber or an optical fiber block having a NA value such that conical diffraction can be ignored. .

과 같은 회절식에서 도광판 내의 전파상수

의 성분들 중

의 값 (즉, 기판에 수직한 방향으로 광의 퍼짐각)이 크지 않 아 회절광의 수렴특성이

에 의해 거의 영향을 받지 않으며, 따라서 각 파장별 수렴점들이 충분히 작게 결상되어 수광소자(340)에 포함된 단위센서들 간에 큰 영향을 주지 않을 정도의 NA값을 갖는 광섬유 또는 광섬유 블록을 의미한다(여기서, x는 격자들의 배열방향, y는 기판에 수직한 방향 z는 기판에 평행하고 격자배열에 수직한 방향을 나타낸다).That is, for example,

Propagation constant in LGP in diffraction equation such as

Of the components of

(I.e. the spread angle of light in the direction perpendicular to the substrate) is not large and the convergence characteristic of the diffracted light

It is hardly influenced by, and thus means an optical fiber or an optical fiber block having NA values such that convergence points of each wavelength are sufficiently small to have little effect on the unit sensors included in the light receiving element 340 ( Where x is the array direction of the gratings, y is the direction z perpendicular to the substrate, and z is the direction parallel to the substrate and perpendicular to the grid array).

The light receiving element 340 serves to receive light diffracted and emitted by the flat diffraction grating 320 and may be formed of, for example, a photodiode PD. The light receiving element 340 may be formed as one or a plurality of sensor lines, and may be formed at a position facing the flat diffraction grating 320 of the edge end section of the flat light guide plate 300.

Of course, the light receiving element 340 may be formed in other areas other than the above, for example, may be formed on the upper surface of the flat light guide plate 300 (not shown).

For example, a 45 ° inclined plane is formed on the surface of the planar light guide plate 300 to which the diffracted light is emitted, for example, with respect to the surface of the planar light guide plate 300, and then the light diffracted by the planar diffraction grating 320 The light receiving element 340 is formed on the upper surface of the flat light guide plate 300 from which light is emitted by reflecting from the 45 ° inclined plane to be perpendicular to the flat light guide plate 300 at the edge of the flat light guide plate 300. can do.

That is, the light incident on the cross-section of the planar light guide plate 300 by the optical fiber 330 is diverged along the planar light guide plate 300 to the reflection mirror 310, and then the planar diffraction is performed on the reflection mirror 310. Converging along the planar light guide plate 300 to the grating 320 and diffracted from the planar diffraction grating 320, and located at the edge of the planar light guide plate 300 facing the planar diffraction grating 320. It is possible to emit vertically from the planar light guide plate 300 by the 45 ° inclined plane, and to be received by the light receiving element 340 located on the surface of the flat light guide plate 300 facing the 45 ° inclined plane.

4 is a graph illustrating a result of calculating a position where light is focused for each wavelength through computer calculation. Referring to FIG. 4, the location 410 where the 1.0 μm wavelength is focused and the location 420 where the 1.5 μm wavelength is focused can be identified. In addition, wavelengths between 1.0 μm and 1.5 μm result in focusing at a point between each of the positions 410 and 420.

Properly designed plate diffraction grating 320 may cause the trajectory 430 of the points where focusing is formed as the wavelength changes to be substantially parallel to the line on which the plate diffraction grating 320 is placed. Accordingly, the angle between the direction in which the light is reflected by the flat diffraction grating 320 and the trajectory 430 becomes smaller than the total internal reflection angle, and the light reflected by the flat diffraction grating 320 is high when the optical system is located. It can be pulled out of the medium of refractive index.

For example, as in the case of FIG. 2 described above, light is directly directed from the optical fiber (100 of FIG. 2) to the flat diffraction grating (110 of FIG. 2) without using the reflection mirror 310 applied to the embodiment of the present invention. In the case of incident light, it was difficult to form the focusing trajectory at an angle equal to or less than the total internal reflection angle, so it was difficult to extract the light out of the medium having a high refractive index in which the optical system of the spectroscope was located. It is possible to easily allow the light reflected from the grating 320 to escape out of the high refractive index medium in which the optical system of the spectrometer is located.

5 and 6 are perspective views for explaining the operation of the flat spectroscope according to an embodiment of the present invention.

Referring to FIG. 5, incident light 510 having various wavelengths is incident through the input side optical fiber 330. The incident light 510 spreads in the horizontal direction in the planar light guide plate 300, but proceeds in the dotted direction of FIG. 5 along the planar light guide plate 300 by a total internal reflection phenomenon in the vertical direction. At this time, the dotted line representing the incident light 510 represents an approximate boundary of the path in which the light spreads, and does not mean that the light proceeds only in the dotted line.

The incident light 510 spreading along the planar light guide plate 300 meets the reflecting surface of the reflecting mirror 310, and the reflected light 520 reflected from the reflecting surface proceeds toward the planar diffraction grating 320. do. Here, the reflective mirror 310 may be formed in a concave shape toward the optical fiber 330 having a constant radius of curvature, for example, the incident light 510 incident and spread from the optical fiber 330 is reflected from the reflective mirror 310. Afterwards, it gradually progresses toward the flat diffraction grating 320.

Referring to FIG. 6, the directions of the diffracted light beams 510a and 510b diffracted and reflected by the flat diffraction grating 320 may be confirmed. The flat diffraction grating 320 may be in different directions depending on the wavelength of light. Advance the light.

Thus, for example, light having a wavelength of a may travel along the path of 510a of FIG. 6 to converge to a point 520a of FIG. 6, and light having a wavelength of b may travel along the path of 510b of FIG. 6. Converge to point 520b of six. At this time, if the wavelength has a value between a and b, the gathering point may also converge to the middle point of 520a of FIG. 6 and 520b of FIG. 6.

Accordingly, the flat spectroscope according to an embodiment of the present invention can separate light by wavelength.

7 is a cross-sectional view for explaining a method of designing a plate-type diffraction grating applied to an embodiment of the present invention.

6 and 7, the flat diffraction grating 320 may reflect the light reflected from the reflective mirror 310 to the reflected light 710, that is, the light incident on the flat diffraction grating 320 to different points according to the wavelengths. For example, since the grating serves as a reflective grating, each grating spacing must be determined accordingly.

For example, when light having a wavelength λ in vacuum is reflected by the reflecting mirror 310 and reaches an arbitrary first point 720 on the surface of the flat diffraction grating 320, the phase of the light at this time is referred to as φ1 and another arbitrary It can be said that the phase when it reaches the second point 730 is φ2, where the phase φ is generally well known that there is a relationship between the distance L through which light travels and the following equation (1).

는 빛의 파장,

는 평판형 도광판(300)에서의 빛의 유효굴절률을 의미한다. here

Is the wavelength of light,

Denotes an effective refractive index of light in the flat light guide plate 300.

로 나타낼 수 있고, 제2 지점(730)에서 광의 위상은

로 나타낼 수 있다. For example, the distance traveled from the optical fiber 330 to the first point 720 is referred to as L ₁ , and the distance traveled from the optical fiber 330 to the second point 730 is referred to as L ₂ . If the phase of the light at the first point 720 is

And the phase of the light at the second point 730 is

It can be represented as.

In this case, the lattice spacing of the planar diffraction grating 320 is designed so that the light reflected at the first point 720 and the light reflected at the second point 730 are collected at an arbitrary third point 740. Here, for example, the distance from the first point 720 to the third point 740 _is referred to as L _(9-11) , and the distance from the second point 730 to the third point 740 is referred to as L _{(10−). 11)} , the phase of the light at the third point 740 is an integer of 2π so that the light reflected at the first point 720 and the light reflected at the second point 730 converge to the third point 740. It must be doubled. Therefore, Equation 2 below should be satisfied.

Where m is any integer.

In this case, if the position of the first point 720 and the second point 730 is properly adjusted, the values of L ₁ , L ₂ , L _(9-11) and L _(10-11) are changed accordingly. The coordinates of the first point 720 and the second point 730 are determined to satisfy the equation (2) in the m value. Then, the light reflected at the first point 720 and the light reflected at the second point 730 cause constructive interference at the third point 740, and eventually light is collected at the third point 740.

In a preferred embodiment of the present invention, the first point 720 is first determined, and the coordinates of the second point 730 are determined by the above-described method. Thereafter, the coordinates of the second point 730 where the coordinates are determined can be found, and the coordinates of the other point can be continually repeated to find the coordinates of the diffraction grating.

After determining the lattice spacing of the planar diffraction grating 320 for a particular wavelength [lambda] in this manner, all light having the wavelength [lambda] converges to a particular point, for example, the third point 740. On the other hand, for example, light having λ ', which is a wavelength different from the wavelength λ, is concentrated at a point different from the third point 740 described above, for example, the fourth point 750. If you keep finding the points that are concentrated according to the wavelength, you can get the location where the light converges.

Although preferred embodiments of the flat spectroscope according to the present invention have been described above, the present invention is not limited thereto, and various modifications are made within the scope of the claims and the detailed description of the invention and the accompanying drawings. It is possible and this also belongs to the present invention.

1 is a cross-sectional view for explaining a spectrometer implemented by a conventional plate-type rotary grating.

FIG. 2 is a graph for explaining a movement trajectory of a convergence point position according to a change in light wavelength estimated by a Fresnel-Kirchhoff equation in a conventional spectrometer.

3 is a perspective view illustrating a flat spectroscope according to an embodiment of the present invention.

4 is a graph illustrating a result of calculating a position where light is focused for each wavelength through computer calculation.

5 and 6 are perspective views for explaining the operation of the flat spectroscope according to an embodiment of the present invention.

7 is a cross-sectional view for explaining a method of designing a plate-type diffraction grating applied to an embodiment of the present invention.

Claims (10)

In the flat spectroscope having a light incident from the optical fiber and having a flat light guide plate and a flat diffraction grating, At least one reflective mirror having a concave reflective surface is provided in an edge region of the flat light guide plate, and reflects light incident on the flat light guide plate through the reflective surface to converge in the direction of the flat diffraction grating. , The flat diffraction grating has a non-uniform lattice spacing and is formed of a silicon substrate of (1, x, x) plane so that the diffraction angle according to the wavelength of the light reflected by the reflection mirror can be continuously varied. Asymmetry of is controlled by the x value, wherein the x value is 0 or 1, In transmitting incident light incident on the flat diffraction grating to different points according to wavelengths, a distance traveled by the incident light to a first point is referred to as L ₁ , and the incident light reaches a second point. Assuming that the distance traveled is L ₂ , the distance from the first point to the third point _is called L _(9-11) and the distance from the second point to the third point _is called L _(10-11) , Determining coordinates of the first point and the second point to satisfy Equation 2 at a specific m value so that the light reflected at the first point and the light reflected at the second point are collected at a third point. Flat spectrometer, characterized in that (Equation 2)

Where m is any integer. The method according to claim 1, The flat spectroscope further comprises an optical fiber capable of injecting light into the flat light guide plate and a light receiving element provided at a predetermined region of the end of the flat light guide plate to which light diffracted by the flat diffraction grating is converged. Flat spectrometer. The method of claim 2, The light receiving element is formed on a predetermined end surface of the planar light guide plate so as to face each other with the planar diffraction grating, or a 45 ° inclined plane is formed on a predetermined end surface of the planar light guide plate facing each other with the planar diffraction grating. And a light is formed in a predetermined region of an upper surface of the flat light guide plate which is reflected by the 45 ° inclined plane. The method according to claim 1, The planar light guide plate has a constant thickness of 0.5 to 1.5 mm and has a refractive index larger than air. delete The method according to claim 1, The reflecting mirror is a flat spectrometer, characterized in that the curved surface having a predetermined curvature radius or in the form of a non-curved. The method according to claim 1, And said reflecting mirror has an aluminum or silver coated reflecting surface. delete The method according to claim 1, And said flat diffraction grating is formed by a process such as holographic exposure or photolithography. delete

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