JPH11271143A - Spectroscope and optical spectrum analyzer using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a spectroscope which can absorb a change in an optical axis, which can be miniaturized and whose spectral resolution can be enhanced and to realize an optical spectrum analyzer which uses it. SOLUTION: In a spectroscope 51 a collimating mirror 4 by which light, to be measured, passed through a slit 1 is changed into parallel light so as to be reflected is installed, a wavelength dispersion element 5 by which reflected light from the collimating mirror 4 is radiated at respectively different angles at every wavelength is installed, a condensing mirror 6 on which respective beams of radiated light from the wavelength dispersion element 5 are incident is installed, an optical switch means 11 by which reflected light condensed by the condensing mirror 6 is scanned is installed, and a photodetector 12 on which transmitted light from the optical switch means 11 is incident is installed. Consequently, it is not required to sequentially drive the photodetector 12 differently from conventional cases, and it is not required that a signal processing part such as a multiplexer or the like which is used to drive the photodetector and to fetch a signal should be formed on the same board. As a result, the photodetector 12 can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polychromator type spectrometer, and more particularly to a spectrometer having an improved light receiving system of a photodetector and an optical spectrum analyzer using the same.

[0002]

2. Description of the Related Art In a conventional spectroscope using a polychromator, light to be measured is separated by a wavelength dispersive element such as a diffraction grating for each wavelength and incident on an array type photodetector. Since the position of the light spot generated by the photodetector differs depending on the wavelength, it is possible to measure the light spectrum by detecting the light intensity at each light receiving element of the array element.

FIG. 7 is a block diagram showing an example of an optical spectrum analyzer using such a conventional spectroscope. In FIG. 7, 1 is a slit, 2 is an optical shutter,
Reference numeral 3 denotes a depolarizing element, 4 denotes a collimating mirror, 5 denotes a wavelength dispersion element such as a diffraction grating, 6 denotes a condensing mirror, and 7 denotes a photodetector (hereinafter simply referred to as an optical detector) in which a plurality of light receiving elements are arranged in an array. 8 is a drive circuit, 9 is an arithmetic circuit,
Reference numeral 10 denotes display means, and 100 denotes light to be measured. Also, 1 to
Reference numeral 7 denotes a spectroscope 50.

The light to be measured 100 passes through the slit 1 and enters the collimating mirror 4 via the depolarizing element 3. The reflected light from the collimating mirror 4 is incident on a wavelength dispersion element 5 such as a diffraction grating, and the emitted light is incident on a condenser mirror 6. Then, the reflected light from the condenser mirror 6 is condensed on the photodetector 7. Further, the supply of the measured light 100 to the wavelength dispersion element 5 and the like by the optical shutter 2 is appropriately restricted.

[0005] The output signal of the photodetector 7 is connected to a drive circuit 8 for driving the light receiving element and reading out the signal, and the drive signal from the drive circuit 8 is connected to the photodetector 7. The output signal of the drive circuit 8 is connected to the arithmetic circuit 9 and
Are connected to the display means 10.

Now, the operation of the conventional example shown in FIG. 7 will be described with reference to FIG. FIG. 8 is a plan view showing an arrangement state of a plurality of light receiving elements constituting the photodetector 7. The incident light 100 passing through the slit 1 becomes parallel light via the depolarizing element 3 and the collimating mirror 4, and is incident on the wavelength dispersion element 5 such as a diffraction grating. The light to be measured 100 is transmitted through the depolarizing element 3 to remove the polarization dependence of the wavelength dispersion element 5.

The wavelength dispersion element 5 such as a diffraction grating emits incident light at different angles depending on the wavelength of the incident light. These emitted lights are condensed on the photodetector 7 by the condensing mirror 6 and detected.

At this time, the wavelength dispersion element 5 transmits the light 10
Since the emission angle of the emitted light differs depending on the wavelength of 0, the position of the light spot focused on the photodetector 7 differs according to the wavelength. Therefore, the light intensity detected by each light receiving element constituting the photodetector 7 also differs.

For example, when the photodetector 7 is "E00" in FIG.
1 "," E002 "," E003 "," E004 ","
It is assumed that each of the light receiving elements is formed in a strip shape and includes six light receiving elements indicated by E005 "and" E006. "At this time, a light spot of a certain wavelength indicated by" SP01 "in FIG. The light is collected on the light receiving element indicated by “E002”.
The focusing position changes in the “x-axis direction” in FIG. 8 as the wavelength changes.

Further, such a photodetector uses a light receiving element that covers the wavelength range of the light to be measured. For example, in a short wavelength range of 1 μm or less, “Si” is used. In a long wavelength region such as 3 μm ”or“ 1.5 μm ”,“ InGaAs ”or“ Ge ”is used.

The drive circuit 8 sequentially drives each light-receiving element constituting the photodetector 7 by a drive signal and reads out an output signal from the light-receiving element. For example, “E00” in FIG.
The drive circuit 8 sequentially scans the light receiving elements 1 "to" E006 "and reads out the light intensity detected by the light receiving elements.

Since the light intensities detected by the respective light receiving elements constituting the photodetector 7 are different from each other as described above, the light intensities detected by the respective light receiving elements are sequentially plotted, so that the An optical spectrum can be obtained.

That is, the arithmetic circuit 9 performs appropriate arithmetic processing on an optical spectrum in which output signals from the respective light receiving elements read out by the drive circuit 8 are sequentially plotted, generates a display signal, and outputs the display signal to the display means 10. Reference numeral 10 performs display based on a display signal from the arithmetic circuit 9.

As a result, it is possible to measure and display the optical spectrum of the measured light 100. In addition, the measured light 100
In the case of laser light, it is possible to accurately estimate the center wavelength of the laser light by assuming that the light spot incident on each light receiving element has a Gaussian distribution.

[0015]

However, in the spectroscope 50 as shown in FIG. 7, the photodetector 7 is constituted by arranging light-receiving elements of "InGaAs" in an array. In this case, it is difficult to form a signal processing unit such as a multiplexer for driving each light receiving element or extracting a signal like “Si” on the same substrate, and the light receiving element formed of “InGaAs” is difficult. The photodetector 7 is configured by hybridly connecting a signal processing unit formed of “Si” by wire bonding or the like. Therefore, there is a problem that it is difficult to reduce the size of the photodetector and the number of input / output terminals for driving the signal processing unit increases.

Although it is possible to improve the spectral resolution by increasing the number of light receiving elements and increasing the number of light receiving elements as in "Si", the signal processing section and its wiring area become large. There was a problem that miniaturization would be difficult.

In the case of the arrangement of the light receiving elements as shown in FIG. 8, considering the fluctuation of the optical axis in the "y-axis direction" in FIG. 8 of the focused light spot, the larger ".DELTA.y" in FIG. 8, the better. ,
On the other hand, in order to improve the spectral resolution, the smaller “Δx” in the “x-axis direction” in FIG. 8 is, the better. However, there is a problem that it is difficult to realize such a shape because the yield is reduced.

FIG. 8 shows a graph for improving the spectral resolution.
In the case where the distance between the light receiving elements indicated by the middle “Δd” is reduced, adjacent light receiving elements are affected.
There is a problem that it is also difficult to reduce the interval indicated by Δd ″. Therefore, the problem to be solved by the present invention is to provide a spectroscope that can absorb optical axis fluctuation, reduce the size, and improve the spectral resolution. And an optical spectrum analyzer using the same.

[0019]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a spectroscope in which a collimator converts a measured light passing through a slit into parallel light and reflects the collimated light. A mating mirror, a wavelength dispersive element that emits reflected light from the collimating mirror at different angles for each wavelength, a light condensing mirror to which light emitted from the wavelength dispersive element is incident, and a light condensing mirror By providing an optical switch for scanning the reflected light condensed from the mirror and a photodetector to which the transmitted light from the optical switch enters, downsizing can be achieved and the number of input / output terminals can be reduced. Will be possible. Further, the reliability of the optical system is improved.

According to a second aspect of the present invention, in a spectroscope,
A collimating lens that converts the light to be measured that has passed through the slit into parallel light and transmits the light; a wavelength dispersion element that emits light transmitted from the collimating lens at different angles for each wavelength; A condenser lens into which the emitted light is incident, optical switch means for scanning transmitted light condensed from the condenser lens, and a photodetector to which transmitted light from the optical switch means is incident. Accordingly, the size can be reduced and the number of input / output terminals can be reduced. Further, the reliability of the optical system is improved.

According to a third aspect of the present invention, in the spectroscope according to the first or second aspect of the present invention, the optical switch means includes a plurality of pairs of electrodes sandwiching a liquid crystal arranged in an array. By sequentially applying a voltage to one of the pair of electrodes and scanning reflected light or transmitted light collected from the light collecting mirror or the light collecting lens, downsizing is possible, The number of input / output terminals can be reduced. Further, the reliability of the optical system is improved.

According to a fourth aspect of the present invention, in the spectroscope according to the third aspect of the present invention, since the interval between the pair of electrodes is arranged close to each other, a portion that cannot be received by the photodetector is very small. Since the light intensity decreases, the light intensity of the measured light can be obtained accurately.

According to a fifth aspect of the present invention, in the spectroscope according to the third aspect of the present invention, the width between the pair of electrodes is made smaller than the radius of the light spot to be focused.
Since the transmitting area is subdivided, the spectral resolution is improved.

According to a sixth aspect of the present invention, there is provided the spectroscope according to the fifth aspect of the present invention, wherein a voltage is applied to a plurality of electrodes of the pair of electrodes to change an area through which light passes. By doing so, the transmission area can be made variable, so that various measurements can be made with the optimum transmission light width for the light spot focused on the optical switch means.

According to a seventh aspect of the present invention, in the spectroscope according to the sixth aspect of the present invention, the shape of the light spot condensed on the optical switch means is reduced by slightly sweeping the area through which light passes. It becomes possible to analyze.

According to an eighth aspect of the present invention, there is provided a spectroscope according to the first or second aspect, and arithmetic and control means for controlling the optical switch means and reading and processing an output signal of the photodetector. By providing the display means for displaying based on the output of the arithmetic processing means, the size can be reduced and the number of input / output terminals can be reduced. further,
The reliability of the optical system is improved.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration block diagram showing an embodiment of an optical spectrum analyzer using a spectroscope according to the present invention. In FIG. 1, reference numerals 1 to 6, 9, 10, and 100 denote the same reference numerals as those in FIG. Is a readout circuit, and 14 is a drive circuit. Further, 1 to 6, 11 and 12 constitute a spectroscope 51, and 9, 13 and 14 constitute an operation control means 52, respectively.

The light to be measured 100 passes through the slit 1 and enters the collimating mirror 4 via the depolarizing element 3. The reflected light from the collimating mirror 4 is incident on a wavelength dispersion element 5 such as a diffraction grating, and the emitted light is incident on a condenser mirror 6. Then, the reflected light from the condenser mirror 6 is condensed on the optical switch means 11, and the light transmitted through the optical switch means 11 is incident on the photodetector 12. Further, the supply of the measured light 100 to the wavelength dispersion element 5 and the like by the optical shutter 2 is appropriately restricted.

The output signal of the photodetector 12 is output to the readout circuit 1
3 and the output signal of the read circuit 13 is connected to the arithmetic circuit 9. On the other hand, a drive signal from the drive circuit 14 is connected to the optical switch means 11, and a drive information signal from the drive circuit 14 is connected to the arithmetic circuit 9. Further, the output signal of the arithmetic circuit 9 is connected to the display means 10.

The operation of the embodiment shown in FIG. 1 will now be described with reference to FIG.
This will be described with reference to FIGS. FIG. 2 is an explanatory view showing the configuration of the optical switch means 11, and FIGS. 3 and 4 are explanatory views for explaining the operation of the optical switch means.

Since the basic operation is the same as that of the conventional example shown in FIG. 7, the description of this part is omitted. Optical switch means 1
Numeral 1 is installed at the focal position of a light collecting mirror, which is the position of a conventional photodetector. On the other hand, the photodetector 12 is provided behind the photodetector 12, and its size is large enough to receive the light transmitted through the optical switch means 11.

The optical switch means 11 is composed of a substrate in which liquid crystal indicated by “LC” in FIG. 2 is sealed and “PE01” and “P” in FIG.
E02 "," PE03 "," PE04 "and" PE0 "
A plurality of pairs of electrodes sandwiching the liquid crystal shown in 5 "are arranged in an array.

In FIG. 2, "SW01", "SW02", "SW0" in which the other end is connected to one of the pair of electrodes.
3 ”,“ SW04 ”and“ SW05 ”, and a voltage source“ Vs ”in FIG. 2 connected to the other of the pair of electrodes and the other end of the switch circuit are part of the drive circuit 14. Is composed.

The liquid crystal molecules such as "LC01" shown in FIG. 3 have a scattering plate because the liquid crystal molecules are oriented in various directions when no electric potential is applied to a pair of electrodes shown as "PE01" in FIG. Function as On the other hand, as shown in FIG.
When a potential is applied to the pair of electrodes shown in the middle “PE01”, the liquid crystal molecules are oriented in the same direction, and thus function as a transmission plate.

That is, the drive circuit 14 is switched to "SW0" in FIG.
1 "to" SW05 "are sequentially turned on.
And a pair of electrodes “PE01”
Since a voltage is applied to the part of ".about.PE05" and sequentially changes from the scattering plate to the transmission plate, only the transmitted light is incident on the photodetector 12 provided behind.

Further, since the photodetector 12 is a single light receiving element, the readout circuit 13 simply reads out the output signal from which the transmitted light has been detected to obtain the optical spectrum of the light to be measured as in the conventional case. be able to.

In other words, there is no need to sequentially drive the light receiving elements as in the prior art, and there is no need to form a signal processing unit such as a multiplexer for driving the light receiving elements or extracting a signal on the same substrate. Since the photodetector 12 is composed of a single light receiving element, only two output terminals are required, and the number of input / output terminals is extremely reduced.

As a result, the optical switch means is provided in front of the photodetector, and the optical switch means scans the light incident on the photodetector, thereby eliminating the need to form a signal processing unit on the same substrate. The size of the detector can be reduced.
Also, the number of input / output terminals can be reduced. Furthermore, since the transmission portion of the optical switch means in the "y-axis direction" can be easily enlarged, incident light due to optical axis fluctuation hardly comes off the photodetector, and the reliability of the optical system is improved.

Further, since it is not necessary to hybrid-connect the light receiving element formed of "InGaAs" and the signal processing section formed of "Si" by wire bonding or the like, noise mixed from wiring by wire bonding or the like is also reduced. it can.

However, in the optical switch means as shown in FIG. 2, a pair of electrodes "PE" as shown by "GAP01" in FIG.
01 ”and“ PE02 ”or“ GAP0 ”in FIG.
2 "and a pair of electrodes" PE02 "and" PE0 ".
3 ”, the light incident on this portion is not incident on the photodetector 12, and the photodetector 1
Since there is a portion that cannot be received in step 2, it is difficult to accurately obtain the light intensity of the measured light.

FIG. 5 is an explanatory view showing another structure of the optical switch means. The optical switch means is composed of a substrate in which liquid crystal indicated by "LC" in FIG. 5 is sealed and "PE11", "PE" in FIG.
PE12 "," PE13 "," PE14 "and" PE1 "
A plurality of pairs of electrodes sandwiching the liquid crystal shown in 5 "are arranged in an array.

In FIG. 5, "SW11", "SW12", "SW1" in which the other end is connected to one of the pair of electrodes.
3 ”,“ SW14 ”and“ SW15 ”, and a voltage source“ Vs ”in FIG. 5 connected to the other of the pair of electrodes and the other end of the switch circuit are part of the drive circuit 14. Is composed.

Here, the point different from the optical switch means shown in FIG. 2 is that the interval between the pair of electrodes is arranged so close that the dielectric breakdown between the electrodes does not occur. That is,
A pair of electrodes "PE1" as shown by "GAP11" in FIG.
The distance between "1" and "PE12" or "GAP12" in FIG.
The distance between the pair of electrodes "PE12" and "PE13" as shown in FIG. For this reason, the portion that cannot be received by the photodetector 12 is greatly reduced, so that the light intensity of the measured light can be accurately obtained.

FIG. 6 is an explanatory view showing another configuration of the optical switch means. The optical switch means is composed of a substrate in which liquid crystal indicated by “LC” in FIG. 6 is sealed and “PE21”, “PE” in FIG.
PE22 "," PE23 "," PE24 "and" PE2 "
A plurality of pairs of electrodes sandwiching the liquid crystal shown in 5 "are arranged in an array.

In FIG. 6, "SW21", "SW22", "SW2" in which the other end is connected to one of the pair of electrodes.
3 ”,“ SW24 ”and“ SW25 ”, and a voltage source indicated by“ Vs ”in FIG. 6 connected to the other of the pair of electrodes and the other end of the switch circuit are a part of the drive circuit 14. Is composed.

Here, the point different from the optical switch means shown in FIG. 2 or FIG. 5 is that the width between a pair of electrodes is made sufficiently smaller than the radius of the light spot to be focused. That is, a pair of electrodes “PE21” indicated by “W001” in FIG.
Is the width of “Δxp” and the radius of the light spot converged on the optical switch means is “ω”, and the following relationship is satisfied. Δxp << ω (1)

Therefore, the transmission area is subdivided, so that the spectral resolution is improved. Further, in such a configuration, the transmission area can be varied by controlling a switch circuit such as “SW21” in FIG. 6 and simultaneously applying a voltage to a plurality of electrodes. For this reason, various measurements can be made with the transmitted light width that is optimal for the light spot focused on the optical switch means.

Further, by controlling a switch circuit such as "SW21" in FIG. 6 to sweep the transmission area slightly, it is also possible to analyze the shape of the light spot focused on the optical switch means. It is also possible to correct the measurement result based on the analysis result.

In the description of FIGS. 2, 5 and 6, a plurality of switch circuits and voltage sources have been described as part of the drive circuit 14, but they may also be configured as part of the optical switch means 11. Absent.

Although the reflection optical system is exemplified as the optical system, a transmission optical system using a lens or the like may be used. For example, the optical system may be configured by replacing the collimating mirror with a collimating lens and replacing the condenser mirror with a condenser lens.

Although the diffraction grating is exemplified as the wavelength dispersion element, a prism or the like may be used.

In FIG. 1, the optical shutter 2 and the depolarizing element 3 are not essential components and can be omitted.

[0053]

As is apparent from the above description,
According to the present invention, the following effects can be obtained. According to the first to third aspects of the present invention, the photodetector can be miniaturized by providing the optical switch means in front of the photodetector and scanning the light incident on the photodetector by the optical switch means. Thus, the number of input / output terminals is reduced. Further, the reliability of the optical system is improved.

According to the invention of claim 4, the distance between the pair of electrodes is such that the electrodes are arranged close to each other.
Since the portion that cannot be received by the photodetector is greatly reduced, the light intensity of the measured light can be accurately obtained.

According to the fifth aspect of the present invention, since the width between the pair of electrodes is made smaller than the radius of the light spot to be condensed, the transmission area is subdivided, so that the spectral resolution is improved. I do.

According to the invention of claim 6, the transmission area is made variable by applying a voltage to a plurality of electrodes of the plurality of pairs of electrodes to change the area through which light is transmitted. Therefore, it is possible to perform various measurements with the optimum transmission light width for the light spot focused on the optical switch means.

According to the seventh aspect of the present invention, the shape of the light spot focused on the optical switch can be analyzed by sweeping the transmission area minutely. It is also possible to correct the measurement results.

According to the invention of claim 8, by using the spectroscope according to the present invention for an optical spectrum analyzer, the photodetector can be downsized and the number of input / output terminals can be reduced. Further, the reliability of the optical system is improved.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing one embodiment of an optical spectrum analyzer using a spectroscope according to the present invention.

FIG. 2 is an explanatory diagram showing a configuration of an optical switch means.

FIG. 3 is an explanatory diagram for explaining the operation of the optical switch means.

FIG. 4 is an explanatory diagram for explaining the operation of the optical switch means.

FIG. 5 is an explanatory diagram showing another configuration of the optical switch means.

FIG. 6 is an explanatory diagram showing another configuration of the optical switch means.

FIG. 7 is a configuration block diagram illustrating an example of an optical spectrum analyzer using a conventional spectroscope.

FIG. 8 is a plan view showing an arrangement state of a plurality of light receiving elements constituting a photodetector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Slit 2 Optical shutter 3 Depolarization element 4 Collimating mirror 5 Wavelength dispersion element 6 Condensing mirror 7, 12 Photodetector 8, 14 Drive circuit 9 Arithmetic circuit 10 Display means 11 Optical switch means 13 Readout circuit 50, 51 Spectrum Device 52 arithmetic control means 100 light to be measured

Claims (8)

[Claims] 1. A spectroscope, comprising: a collimating mirror that converts a measured light passing through a slit into parallel light and reflects the light; and a wavelength dispersion that emits reflected light from the collimating mirror at different angles for each wavelength. An element, a condenser mirror on which reflected light from the wavelength dispersive element is incident, an optical switch for scanning outgoing light condensed from the condenser mirror, and an incident light transmitted from the optical switch. A spectroscope comprising: a photodetector; 2. A spectroscope, comprising: a collimating lens for transmitting light to be measured having passed through a slit into parallel light and transmitting the light; and a wavelength dispersion for emitting transmitted light from the collimating lens at different angles for each wavelength. An element, a condensing lens into which light emitted from the wavelength dispersive element is incident, an optical switch for scanning transmitted light condensed from the condensing lens, and an incident light transmitted from the optical switch. A spectroscope comprising: a photodetector; 3. An optical switch means comprising: a plurality of pairs of electrodes sandwiching a liquid crystal arranged in an array; and applying a voltage to one of the plurality of pairs of electrodes sequentially to collect the light. 3. The spectroscope according to claim 1, wherein said spectroscope scans reflected light or transmitted light converged from a mirror or said condenser lens. 4. The spectroscope according to claim 3, wherein a distance between said pair of electrodes is arranged close to each other. 5. The apparatus according to claim 3, wherein a width between said pair of electrodes is smaller than a radius of a light spot to be focused.
The spectrometer described. 6. The spectroscope according to claim 5, wherein a voltage is applied to a plurality of electrodes of the pair of electrodes to change an area through which light is transmitted. 7. A spectroscope according to claim 6, wherein said area through which light passes is slightly swept. 8. A spectroscope according to claim 1 or 2, an arithmetic control means for controlling said optical switch means and reading and processing an output signal of said photodetector, and based on an output of said arithmetic processing means. An optical spectrum analyzer comprising: display means for performing display.