TWI437215B - Micro spectrometer with stray light filtering structure - Google Patents

Description

Micro spectrometer with stray light filtering structure

This invention relates to a spectrometer, and more particularly to a microspectrometer having a stray light filtering configuration.

The photometry of the radiation source is usually measured using a spectrometer, which requires a slit structure to control a certain amount of light source into it, and then a diffraction grating to cooperate with a collimator and a correction lens ( The combination of correcting lenses focuses the output spectral components on an image plane. A light sensor can be placed on the image plane so that individual spectral components can be obtained. However, the results detected by the spectrometer's photosensor are not available in some cases because there is a lot of stray light that enters the slit and reaches the diffraction grating, which in turn affects the diffraction grating. Diffraction results. Therefore, the input source must be well controlled, which limits the application level of traditional spectrometers.

Figure 6 shows a schematic diagram of a conventional spectrometer 100. As shown in FIG. 6, the conventional spectrometer 100 includes a light source 110, an input portion 120, a collimating mirror 130, a planar grating 140, a focusing mirror 150, and a linear photo sensor 160. The light source 110 outputs the optical signal 200 through the input unit 120 and passes through the collimating mirror 130 in the free space to reach the planar grating 140. The macroscopic profile of the diffraction pattern 142 of the planar grating 140 is a plane. The planar grating 140 is more suitable for the conventional processing method of scribing a diffraction pattern with a diamond knife, but it is therefore impossible to make the outline of the grating. The surface has a focusing effect, so that after the planar grating 140 separates the optical signal into a plurality of spectral components, in order to focus the spectral components on the linear photosensor 160, it is necessary to add the focusing mirror 150. Therefore, the optical path of the entire spectrometer 100 is long and relatively bulky. However, because of this, the amount of light entering the conventional spectrometer can be large, and the influence of stray light on the diffraction result is small, so the conventional spectrometer does not necessarily need to consider the influence of the stray light on the signal to be measured.

Accordingly, it is an object of the present invention to provide a miniature spectrometer having a stray light filtering configuration for blocking the travel of stray light to a micro-diffractive grating that affects the sensing results of the entire spectrometer.

To achieve the above object, the present invention provides a micro spectrometer having a stray light filtering structure including an input portion, a stray light filtering structure, and a micro-diffractive grating. The input unit receives a first optical signal and a second optical signal. The stray light filtering structure filters out the second optical signal and includes a first filtering section and a second filtering section. The first filter section has a first toothed structure. The second filter section has a second tooth structure disposed at a relative position with the first tooth structure, and an optical path is defined between the first tooth structure and the second tooth structure for the first optical signal to pass, and The second optical signal is filtered into the first filtering section or the second filtering section. The micro-diffraction grating receives the first optical signal constructed by the stray light filtering and separates the first optical signal into a plurality of spectral components.

In order to make the above content of the present invention more obvious, the following is a special The preferred embodiment, in conjunction with the drawings, is described in detail below.

1 shows a top view of a microspectrometer having a stray light filtering configuration in accordance with a preferred embodiment of the present invention. 2 shows a side view of a miniature spectrometer in accordance with a preferred embodiment of the present invention. As shown in Figures 1 and 2, the microspectrometer of the present invention includes an input portion 10, a stray light filtering structure 20, and a micro-diffraction grating 30. Of course, the spectrometer may further include a photo sensor 40, a housing 80 and a light emitting device 60. The input unit 10, the stray light filtering structure 20, the micro diffraction grating 30, and the photo sensor 40 are mounted in the casing 80. The macroscopic profile of the diffraction pattern 32 of the micro-diffraction grating 30 includes one of the reflective curved surfaces shown in FIG. 1, instead of the plane as shown in the conventional FIG. 6, which serves to pass the micro-diffractive grating 30. The light is focused onto the front light sensor 40. Light emitting device 60 can also be secured to housing 80. Since the diffraction grating 30 can utilize ultra-thin tiny parts manufactured by microelectromechanical process (MEMS), semiconductor process, photolithography electroforming (LIGA) or other processes, it can be called a micro-diffraction grating, so The spectrometer of the invention can be referred to as a miniature spectrometer.

The input unit 10 includes a slit structure for receiving a first optical signal S1 and a second optical signal S2, wherein S1 is directly into the micro spectrometer of the present invention from a suitable preset angle. The light signal to be measured that arrives at the micro-diffraction grating 30 (as shown in FIG. 1), and S2 enters the spectrometer from the range of the above-mentioned appropriate preset angle, and if it is not filtered, it will undergo several degrees of reflection or other The unpredictable optical path will then arrive at the micro-diffraction grating 30 at an unpredictable angle The number (Figure 1), which may itself be part of the optical signal to be measured, has become unusable stray light after the above path. The stray light filtering structure 20 can be disposed between the input portion 10 and the micro-diffractive grating 30 for filtering the second optical signal S2 and includes a first filtering section 22 and a second filtering section 24.

The first filter section 22 has a sheet-like structure and has a first toothed structure 22T. The second filter section 24 has a sheet-like structure and has a second toothed structure 24T that is placed in a relative position with the first toothed structure 22T. An optical passage 26 is defined between the first tooth structure 22T and the second tooth structure 24T for the passage of the first optical signal S1 entering from the input portion 10 at an appropriate predetermined angle to reach the micro diffraction grating 30. The first and second filter sections 22, 24 include a plurality of sharp serrations for blocking the second optical signal S2 (ie, stray light) and guiding it into the groove between the serrations to prevent The two optical signals S2 travel to the micro-diffraction grating 30 after various unpredictable paths. The first filter section 22 and the second filter section 24 are located on the same plane.

The micro-diffraction grating 30 is configured to receive the first optical signal S1 of the structure 20 by the stray light filtering and separate the first optical signal S1 into a plurality of spectral components C.

In order to obtain these spectral components C for processing, the photosensor 40 can be utilized to receive such spectral components C. These spectral components C can be converted into digital signals after subsequent processing. In the present embodiment, the number of such spectral components C that can be focused on the photosensor 40 is greater than two.

In order to facilitate the installation of the stray light filtering structure 20, the housing 80 has a plurality of The positioning post 80R, the first filtering section 22 and the second filtering section 24 have a plurality of positioning holes 22H, 24H. The positioning posts 80R are respectively inserted into the positioning holes 22H, 24H, so that the positioning holes 22H, 24H respectively surround the positioning post 80R, and the positioning effect is achieved. It should be noted that the first filter section 22 and the second filter section 24 may be in an integrally formed configuration.

The light-emitting device 60 is configured to generate a first light signal S1 and a second light signal S2 after a light source passes through a sample 70, such as a test paper or other object to be tested.

In addition, the micro spectrometer may further include a waveguide device 50 including a first waveguide sheet 52 and a second waveguide sheet 54 facing each other to interact with the input portion 10, the stray light filtering structure 20, and the micro diffraction grating. The light path 26 is defined in common so that the first light signal S1 can be reflected and traveled in the light channel 26. Since the amount of light entering the micro spectrometer is small, the waveguide 50 is generally used to reduce the light loss, and the stray light filtering structure 20 is used to filter out stray light.

A so-called miniature spectrometer in which the micro-diffraction grating 30 is fabricated by a microelectromechanical process (MEMS) or semiconductor process. The height of the diffraction pattern 32 of the micro-diffraction grating 30 is generally about several tens of micrometers to several hundreds of micrometers. Therefore, the first filtering section 22 and the second filtering section 24 are generally also used in the tens of micrometers to hundreds of micrometers. The thickness is formed to form a light tunnel 26 having a height of several tens of micrometers to hundreds of micrometers. This miniature spectrometer has a small amount of light entering, unlike conventional polarizers that have a large amount of light entering the device. In the case of a large amount of light, the effect of stray light on the diffraction result is small, so the conventional spectrometer does not need to consider this problem. In the case of a small amount of light, the filtering of stray light is quite important. because The inventor of the present invention actually discovered this problem when developing this product, so it was proposed to solve this problem by having a high-efficiency stray light filtering structure, and it has been proved to be quite good.

Figure 3 is a schematic illustration of the theory of the Rowland circle of the prior art illustrating the ability of the miniature spectrometer of the present invention to focus on a straight line of sensors. As shown in FIG. 3, according to the theory of Rowland circle, after the incident light passes through the slit structure 10, the stray light filtering structure 20 filters out unnecessary components and finally reaches the micro-diffraction grating 30'. The micro-diffraction grating 30' produces a diffraction and focuses imaging on the Roland circle RC. Thus, a light sensor 40 that intersects the Roland circle RC can receive at least two spectral components. Since the diffraction pattern of the micro-diffraction grating 30' suitable for the Roland circle has a fixed pitch, only the spectral components can be focused and imaged at two points of the line. Changing the pitch can change the size of the Roland circle, so the diffraction pattern is designed to have a non-fixed pitch, and at least three spectral components can be focused on the straight line, that is, the effect of FIG. 1 is achieved.

Therefore, the photo sensor 40 of FIG. 1 can have a plurality of photosensitive cells 42, such as two, three or more, and the photosensitive cells 42 are arranged in a line.

It is worth mentioning again that the stray light signal can contain not only the noise but also the optical signal to be measured with the wrong angle of incidence. In the case where the stray light filtering structure 20 is not provided, such an optical signal having an incorrect incident angle passes through the input portion 10 and is reflected by the housing 80 several times to reach the micro-diffractive grating 30, thereby interfering with To the diffraction result. In addition, it is also possible to add between the micro diffraction grating 30 and the photo sensor 40. A stray light filtering structure 20 is installed.

Figure 4 shows a schematic diagram of the filtering principle of a stray light filtering construction. The preset angle is 2 θ, which is related to the first tooth structure 22T of the first filter section 22 and the second tooth structure 24T of the second filter section 24, wherein the angle θ is the first optical signal S1 The angle θ with respect to the optical axis of the input portion 10 is defined by the first tooth structure 22T, and the angle 2 θ-θ is defined by the second tooth structure 24T. The entry angle of the second optical signal S2 is greater than the angle 2 θ, and the entry angle of the first optical signal S1 is less than the angle 2 θ. The first optical signal S1 does not enter the filtering section and is therefore not consumed by the filtering section. The second optical signal S2 will enter one of the triangular recesses of the filtering section and be reflected back and forth inside to be weak. In this way, the second optical signal S2, which would otherwise cause the stray optical signal, can be eliminated by the filtering section, so that the spectral components to be obtained are more clearly defined.

Figure 5 shows a schematic representation of the results of the reflection of the smooth sidewalls. In order to demonstrate the efficacy of the stray light filtering construction, Applicants specifically provide a first smooth side wall 21 and a second smooth side wall 23 in place of the first filter section 22 and the second filter section 24 of FIG. The first smooth sidewall 21 and the second smooth sidewall 23 do not have a toothed structure. Therefore, the second optical signal S2 is reflected by the smooth sidewalls 21 and 23 and gradually moves in the direction of the micro-diffraction grating 30. This interferes with the measurement results of the spectrometer.

In the miniature spectrometer of the present invention, the diffraction grating is an ultra-thin micro-component that can be fabricated using a microelectromechanical process (MEMS) or semiconductor process. Generally, the diffraction pattern of a micro-diffraction grating has a height of only about tens of micrometers to hundreds of micrometers. In order to prevent the light source to be measured from being scattered in the free space, the ultra-thin micro-diffractive grating is only connected. Receiving light of a diffraction pattern irradiated to the above-mentioned height of several tens of micrometers to several hundred micrometers, a waveguide sheet is generally formed by a material having a better reflectance, and the micro-diffraction grating is sandwiched up and down to form an optical signal waveguide. After the light source signal enters the micro spectrometer from the input section, most of the light (including stray light) can reach the micro-diffraction grating by the action of the waveguide. Despite this, the amount of light entering a miniature spectrometer is still small compared to conventional large spectrometers, and the filtering of stray light is quite important in the case of a small amount of light.

In addition, the aforementioned preset angle depends on the size of the grating and the optical path. In a preferred embodiment, the preset angle can be 4 degrees (2 degrees left and right), and the preset angle of the present invention is obvious compared to a preset angle of about 10 degrees (5 degrees left and right) of a conventional spectrometer. A lot smaller. Therefore, the filtering of stray light is more important.

With the spectrometer of the present invention, unnecessary stray light components can be filtered out to avoid interference with spectral components and affect the interpretation results of the photosensor. The thickness of the stray light filtering structure can be quite thin and can be made of metal, plastic or semiconductor materials. When the inventor implemented the architecture according to FIG. 1, the results of installing a stray light filtering structure and a stray light filtering structure were compared, and it was found that a spectrometer equipped with a stray light filtering structure can obtain better interpretation results. . Therefore, the spectrometer of this case does have a substantial increase in its performance.

The planar stray light filtering structure of the present invention is particularly suitable for a micro spectrometer compared to a stereoscopic stray light filtering structure of a conventional optical device such as a camera or an optical pen.

The specific embodiments set forth in the detailed description of the preferred embodiment are only The present invention is not limited to the above embodiments, and various changes are made without departing from the spirit of the invention and the scope of the following claims. range.

C‧‧ ‧ spectral component

H‧‧‧ Height

RC‧‧‧Roland

S1‧‧‧first optical signal

S2‧‧‧second optical signal

10‧‧‧ Input Department

20‧‧‧ stray light filtering structure

21‧‧‧First smooth side wall

22‧‧‧First filter section

22T‧‧‧First tooth structure

22H, 24H‧‧‧ positioning holes

23‧‧‧Second smooth side wall

24‧‧‧Second filter section

24T‧‧‧second tooth structure

26‧‧‧Light channel

30, 30'‧‧‧ miniature diffraction grating

32‧‧‧Diffraction pattern

40‧‧‧Light sensor

50‧‧‧Wave device

52‧‧‧First waveguide

54‧‧‧Second waveguide

60‧‧‧Lighting device

70‧‧‧sample

80‧‧‧shell

80R‧‧‧ positioning column

100‧‧‧ Spectrometer

110‧‧‧Light source

120‧‧‧ Input Department

130‧‧ ‧collimating mirror

140‧‧‧Flat grating

142‧‧‧Diffraction pattern

150‧‧‧Focus mirror

160‧‧‧Linear light sensor

200‧‧‧Optical signal

1 shows a top view of a microspectrometer having a stray light filtering configuration in accordance with a preferred embodiment of the present invention.

2 shows a side view of a miniature spectrometer in accordance with a preferred embodiment of the present invention.

Figure 3 shows a perspective view of another spectrometer of the present invention.

Figure 4 shows a schematic diagram of the filtering principle of a stray light filtering construction.

Figure 5 shows a schematic representation of the results of the reflection of the smooth sidewalls.

Figure 6 shows a schematic of a conventional spectrometer.

C‧‧ ‧ spectral component

S1‧‧‧first optical signal

S2‧‧‧second optical signal

10‧‧‧ Input Department

20‧‧‧ stray light filtering structure

22‧‧‧First filter section

22H, 24H‧‧‧ positioning holes

22T‧‧‧First tooth structure

24‧‧‧Second filter section

24T‧‧‧second tooth structure

26‧‧‧Light channel

30‧‧‧Micro Diffraction Grating

32‧‧‧Diffraction pattern

40‧‧‧Light sensor

50‧‧‧Wave device

60‧‧‧Lighting device

70‧‧‧sample

80‧‧‧shell

80R‧‧‧ positioning column

Claims (16)

A miniature spectrometer having a stray light filtering structure, comprising: an input portion for receiving a first optical signal entering the interior of the micro spectrometer from a predetermined angle and entering from a range of the preset angle a second optical signal inside the micro spectrometer; a stray light filtering structure for filtering the second optical signal, the stray light filtering structure comprising: a first filtering section having a first tooth structure; And a second filter segment having a second tooth structure disposed at an opposite position to the first tooth structure, wherein the first tooth structure and the second tooth structure define an optical path for the Passing the first optical signal and filtering the second optical signal into the first filtering section or the second filtering section; and a micro-diffraction grating receiving the structure by the stray light filtering The first optical signal separates the first optical signal into a plurality of spectral components, wherein the stray light filtering structure is disposed between the input portion and the micro-diffractive grating. The micro spectrometer of claim 1, further comprising: a photo sensor for receiving the spectral components. The microspectrometer of claim 2, wherein the number of the spectral components that can be focused on the photosensor is greater than two. The micro spectrometer of claim 2, wherein the photo sensor has a plurality of photosensitive cells, and the photosensitive cells are arranged in a line. The micro spectrometer of claim 2, further comprising: a housing, wherein the input portion, the stray light filtering structure, the micro-diffractive grating, and the photo sensor are mounted in the housing . The micro spectrometer of claim 5, wherein the housing has a plurality of positioning posts, the first filtering section and the second filtering section having a plurality of positioning holes, the positioning holes respectively surrounding the Positioning column. The micro spectrometer of claim 2, further comprising a light emitting device for emitting a light source through a sample to generate the first optical signal and the second optical signal. The micro spectrometer of claim 1, wherein the first filter segment and the second filter segment are on the same plane. The micro spectrometer of claim 1, wherein the preset angle is substantially equal to 4 degrees. The micro spectrometer of claim 1, wherein the first filter section and the second filter section are integrally formed. The micro spectrometer of claim 1, wherein the micro-diffraction grating has a diffraction pattern, and the macroscopic profile of the diffraction pattern comprises a curved surface. The micro spectrometer of claim 1, further comprising a waveguide device comprising a first waveguide sheet and a second waveguide sheet, the two facing each other to interact with the input portion, the stray light filtering structure And the micro-diffraction grating jointly defines the optical channel, so that the first optical signal can be reflected and traveled in the optical channel. A spectrometer comprising: an input unit for receiving a first optical signal entering the interior of the spectrometer from a predetermined angle and a second optical signal entering the interior of the spectrometer from a range of the preset angle; a stray light filtering structure comprising a first filtering section having at least one first tooth structure for filtering the second optical signal; a micro diffraction grating receiving the structure by the stray light filtering The first optical signal separates the first optical signal into a plurality of spectral components; and a photo sensor receives the light separated by the micro-diffractive grating. The spectrometer of claim 13, wherein the second optical signal enters the first filtering sections and is filtered by multiple reflections. A spectrometer comprising: an input portion; a micro-diffraction grating, receiving a first optical signal passing through the input portion, and separating the first optical signal into a plurality of spectral components; a stray light filtering structure comprising a first filtering section of the at least one first tooth structure for filtering out light of the spectral components beyond a predetermined angle, and causing the spectral components to fall within the preset angle Light passes through; and a light sensor receives light that is constructed by filtering the stray light. The spectrometer of claim 15, wherein the light outside the predetermined angle of the spectral components enters the first filtering sections and is filtered by multiple reflections.