JP2009128193A - Wavelength sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength sensor with simple constitution, while having high resolution. <P>SOLUTION: The wavelength sensor detecting the wavelength of light includes: a collimate lens 1; an interference instrument 4 which emits interference light due to the interference with the light from the collimate lens 1, which includes two facing reflecting surfaces, and in which the distance between the reflecting surfaces varies continuously; a photodetector 5 for detecting the interference light transmitted through the interference instrument 4; and a reflecting surface adjustment mechanism for adjusting the distance between the reflecting surfaces and the angle between reflecting plates. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wavelength sensor that detects a change in wavelength.

  As this type of wavelength sensor, for example, there is one using a diffraction grating such as a transmission type or a reflection type (Patent Document 1). As described above, in a wavelength sensor using a diffraction grating, it is necessary to increase the density (lines / mm) of grooves formed on the grating surface of the diffraction grating in order to increase the wavelength resolution.

  However, there are problems that it is difficult to process the diffraction grating and that the cost is increased.

Another problem is that the diffraction grating must be exchanged depending on the wavelength band to be detected.
JP 2006-162509 A

  Accordingly, the present invention has been made in order to solve the above-mentioned problems all at once, and it is a main intended problem to provide a wavelength sensor having a simple configuration while having high resolution.

  That is, the wavelength sensor according to the present invention is a wavelength sensor that detects the wavelength of light, and emits interference light by interfering light from the collimating lens and the collimating lens, and has two reflecting surfaces facing each other. An interferometer in which the distance between the reflecting surfaces continuously changes, a photodetector that detects interference light transmitted through the interferometer, a distance between the reflecting surfaces, and an angle between the reflecting plates And a reflecting surface adjusting mechanism for adjusting.

  If this is the case, it is possible to detect the intensified interference light by multiple reflection and interference of light by the two reflecting surfaces facing each other, and the wavelength can be increased with high resolution by the principle of a so-called Fabry-Perot interferometer. Can be detected. In addition, the interferometer is composed of two opposing reflecting surfaces, and the distance between the reflecting surfaces and the angle between the reflecting surfaces can be adjusted by the reflecting surface adjusting mechanism. The wavelength resolution can be easily adjusted, and the distance and angle can be adjusted to be suitable for the wavelength band to be detected.

  Further, a diffraction grating that splits the light from the collimator lens for each wavelength between the collimator lens and the interferometer, and the light incident surface of the interferometer in a linear form for each color light split by the diffraction grating It is desirable that a cylindrical lens for condensing light is provided.

  In this case, light having a wide wavelength band is split with low resolution by the diffraction grating and the cylindrical lens, and then enters the interferometer. Since the light is dispersed with high resolution by the interferometer, the measurement band of the interferometer having a narrow measurement band is widened, and the resolution of the wavelength sensor can be improved. Note that the resolution of resolution by the diffraction grating and the cylindrical lens is slightly smaller than the wavelength measurement band of the interferometer. In addition, the spectral direction of the previous stage and the spectral direction of the interferometer are made orthogonal.

  Furthermore, it is desirable that an imaging lens is provided between the interferometer and the photodetector. In this case, since the image on the exit surface of the interferometer can be formed on the photodetector, the resolution of the wavelength sensor can be further improved.

  According to the present invention configured as described above, a wavelength sensor having a high resolution and a simple configuration can be provided.

  An embodiment of the present invention will be described below with reference to the drawings.

  1 is a schematic configuration diagram of the wavelength sensor 100 according to the present embodiment, and FIG. 2 is a perspective view illustrating an optical arrangement of the wavelength sensor 100.

  <Device configuration>

  As shown in FIG. 1, the wavelength sensor 100 according to the present embodiment includes a collimating lens 1, a cylindrical lens 11, a diffraction grating 2, a cylindrical lens 3, an interferometer 4, a photodetector 5, and these. A casing 6 for housing. The collimating lens 1, the cylindrical lens 11, the diffraction grating 2, the cylindrical lens 3, the interferometer 4, and the photodetector 5 are fixed in the casing 6.

  Hereinafter, each part will be described.

  The collimating lens 1 converts light guided into the casing 6 by an optical fiber 7 connected to the side wall of the casing 6 into a parallel light beam.

  The cylindrical lens 11 condenses the parallel light beam emitted from the collimating lens 1 in a linear shape.

  The diffraction grating 2 separates the light from the cylindrical lens 11 for each wavelength. Specifically, as shown in FIG. 2, the diffraction grating 2 separates each color light in the Z-axis direction.

  The cylindrical lens 3 condenses each color light separated from the diffraction grating 2 in a linear shape. Specifically, each color light becomes parallel light on the light incident surface 401 of the interferometer 4 in the Z-axis direction. Like that.

  In the present embodiment, the optical axes of the collimating lens 1 and the cylindrical lens 11 and the optical axes of the diffraction grating 2 and the cylindrical lens 3 are shifted as shown in FIG. Thereby, the first-order diffracted light from the diffraction grating 2 can be used. The shifted angle is an angle at which the optical axis of the first-order diffracted light from the diffraction grating 2 and the optical axis of the cylindrical lens 3 are parallel.

  The interferometer 4 emits interference light by interfering with the light from the collimating lens 1. Specifically, the interferometer 4 has two reflecting surfaces 411 and 421 facing each other, and between the reflecting surfaces 411 and 421. The distance changes continuously. More specifically, the interferometer 4 has a structure in which two glass flat plates 41 and 42 having light transmittance are overlapped with a gap therebetween. Reflecting surfaces 411 and 421 on which a reflective coating is applied are formed on the opposing surfaces of the reflecting plates 41 and 42.

  The photodetector 5 detects the interference light obtained by the interferometer 4 and can use, for example, an area image sensor.

  Therefore, the wavelength sensor 100 of the present embodiment includes the reflection surface adjustment mechanism 8. The reflecting surface adjusting mechanism 8 adjusts the distance H between the reflecting surfaces 411 and 421 and the angle α between the reflecting plates 411 and 421 (see FIG. 3). The reflecting surface adjusting mechanism 8 of the present embodiment adjusts the distance H between the two glass flat plates 41 and 42 constituting the interferometer 4 and the angle α of the glass flat plates 41 and 42, and detects the wavelength band. In addition, the distance H and the angle α are adjusted so as to enable high-resolution detection.

  The reflecting surface adjusting mechanism 8 of the present embodiment is provided between the holding member 1 that holds the reflecting plate 411 and the holding member 2 that holds the reflecting plate 421, and the holding member 1 and the holding member 2. , And a mover for adjusting the angle between the reflecting plate 411 and the reflecting plate 421, and a mover driving unit using a worm gear for moving the mover. Further, the mover driving unit is provided with a knob for operating the worm gear.

  The reflecting surface adjusting mechanism 8 of the present embodiment is configured such that when the knob is rotated, the mover is moved by the worm gear and the angle of the reflecting plate 421 is adjusted.

  Next, the resolution of the wavelength sensor 100 configured as described above is shown in FIG. At this time, the distance H between the reflecting surfaces 411 and 421 is 0.1 mm, the angle α between the reflecting surfaces 411 and 421 is 2 ″ (seconds), and the reflectance R is 0.99. Is a refractive index, and n = 1 in FIG.

  At this time, the difference Δx in the peak position between the mth order and the (m + 1) th order is 32.6 mm, and the wavelength difference Δλ between the mth order and the (m + 1) th order at the same position in the interferometer 4 is 2 nm. It can be seen that the wavelength resolution δλ of the wavelength sensor 100 is 0.0064 nm.

  The difference Δx between the peak positions of the m-th order and (m + 1) -th order of the interference light (constant wavelength) is

  It is. From this (Equation 1), it can be seen that when the angle α or the refractive index n is decreased, the interval between the peak positions is widened.

  The wavelength difference Δλ between the m-th order and the (m + 1) -th order at the same position in the interferometer 4 is

  It is. From this (Equation 2), it can be seen that when the distance H or the refractive index n is decreased, the interval between the peak positions is increased.

  The wavelength resolution δλ of the interferometer is

  It is.

  Furthermore, the rate of change of the peak position of the interference light with respect to the wavelength change of the wavelength sensor 100 is

  It is. From this (Equation 4), it can be seen that if the angle α is reduced and m is increased (distance H is increased), the wavelength change sensitivity of the wavelength sensor 100 increases.

  Spectroscopy at the diffraction grating 2 is performed with a resolution equal to or less than the wavelength difference Δλ in the above (Equation 2). Further, the minimum distance H between the reflecting surfaces 411 and 421 is changed according to the resolution of the diffraction grating 2.

  When the resolution of the diffraction grating 2 is high, the minimum distance H between the reflecting surfaces 411 and 421 is increased. Then, it can be seen that the resolution of the wavelength sensor 100 is increased.

  When the reflectivity R of the interferometer 4 is large, the wavelength resolution δλ of the wavelength sensor 100 is large.

  Furthermore, the size of the glass flat plates 41 and 42 of the interferometer 4 needs to be larger than the peak position difference Δx.

  <Effect of this embodiment>

  According to the wavelength sensor 1 according to the present embodiment configured as described above, it is possible to detect the interference light strengthened by the multiple reflection and interference of the light by the two reflecting surfaces 411 and 421 facing each other. -The wavelength can be detected with high resolution by the principle of the Perot interferometer. Further, the interferometer 4 is composed of two reflecting surfaces 411 and 421 facing each other, and the reflecting surface adjusting mechanism 8 can adjust the distance H between the reflecting surfaces 411 and 421 and the angle α between the reflecting surfaces 411 and 421. Therefore, the wavelength resolution δλ can be easily adjusted by adjusting the distance H and the angle α. Therefore, the distance H and the angle α suitable for the wavelength band to be detected can be easily adjusted.

  <Other modified embodiments>

  The present invention is not limited to the above embodiment. In the following description, the same reference numerals are given to members corresponding to the above-described embodiment.

  For example, an imaging lens may be provided between the interferometer 4 and the photodetector 5. In this case, since the interference light from the interferometer 4 can be condensed and incident on the photodetector 5, the resolution of the wavelength sensor can be further improved.

  In addition, some or all of the above-described embodiments and modified embodiments may be combined as appropriate, and the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. .

The equipment block diagram which shows the wavelength sensor which concerns on one Embodiment of this invention. The typical perspective view which shows the optical arrangement | positioning of the wavelength sensor in the embodiment. The schematic diagram which shows the distance and angle between reflective surfaces. The figure which shows the optical arrangement | positioning of a wavelength sensor concretely. The figure which shows the resolution | decomposability of the wavelength sensor in the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Wavelength sensor 1 ... Collimating lens 11 ... Cylindrical lens 2 ... Diffraction grating 3 ... Cylindrical lens 4 ... Interferor 411, 421 ... Reflecting surface H ... Reflecting surface (Shortest) distance α between the reflection surfaces 5... The photodetector 8... Reflection surface mirror installation mechanism

Claims (3)

A wavelength sensor for detecting the wavelength of light,
A collimating lens,
Interfering light emitted from the collimating lens by interfering with light from the collimating lens, having two reflecting surfaces facing each other, and a distance between the reflecting surfaces continuously changing;
A photodetector for detecting interference light transmitted through the interferor;
A wavelength sensor comprising: a reflection surface adjustment mechanism that adjusts a distance between the reflection surfaces and an angle between the reflection plates.   Between the collimating lens and the interferometer, a diffraction grating that splits the light from the collimating lens for each wavelength, and each color light split by the diffraction grating is linearly collected on the light incident surface of the interferometer. The wavelength sensor according to claim 1, further comprising a cylindrical lens that emits light.   The wavelength sensor according to claim 1, wherein an imaging lens is provided between the interferometer and the photodetector.