JP2000205954A - Spectroscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously measure multipoints with high efficiency and high accuracy without having a movable part by providing a spectral means composed of a prism having two spherical surfaces and a concave mirror having a spherical surface. SOLUTION: A prism 1 has two spherical surfaces 3, 7, and is formed of a material of quality having a refractive index (n). When arranging an object 11 in the vicinity of an external conjugate surface 13, in the case where an input space medium is air, the first spherical surface 3 forms a virtual image 15 of the object 11 in the vicinity of a stigmatic internal conjugate surface 17 at a distance of R1/n from the center 5. A point 15 is positioned at an intersection between a circle 17 and a circle 19, and the second spherical surface 7 forms a second virtual image 21 on a stigmatic external conjugate surface 23. The image is relayed to a concave mirror 27 having the curve center 29 arranged in the almost middle between a point 21 and a point 25. The light reflected by the concave mirror 27 concentrates on the point 25. The reflected light again reaches the second spherical surface 7 of the prism 1 to place a focus on a fourth virtual image 31. Finally, the first spherical surface 3 of the prism 1 forms a real image 33 on the last image forming point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectroscopic device, and more particularly to a spectroscopic device capable of high-accuracy simultaneous multipoint analysis.

[0002]

2. Description of the Related Art Conventionally, as a spectroscopic device for analyzing the spectrum of light such as visible light, infrared light and ultraviolet light, for example, there are an RGB method using three red, green and blue sensors and a grating method using a diffraction grating element. Was.

[0003]

In the conventional RGB system, for example, the spectrum is obtained by calculation based on the detection values of the three color sensors, so that it lacks accuracy and definition and only one point can be measured at a time. There was a problem. Further, in the grating method, there is a problem of a failure or an error due to the presence of a movable part in the optical system, and there is also a problem that the measurement target is limited because the diffraction efficiency is not constant due to the brazing characteristics. Furthermore, it is necessary to use a blocking filter to generate higher-order wavelengths, so it is difficult to perform a wide-range spectroscopic analysis at a time, and the essential problem that the diffraction efficiency differs depending on the polarization characteristics of incident light. There was also. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a spectroscopic device that has no moving parts, has high efficiency, and can perform multipoint simultaneous measurement with high accuracy.

[0004]

According to the present invention, there is provided a spectroscopic apparatus, comprising: a prism having two spherical surfaces each having an inner and an outer conjugate surface; and a spectral device comprising a concave mirror having a spherical surface. Further, it is characterized in that it has a slit mounted on the incident portion of the light to be measured and a two-dimensional optical sensor mounted on the image forming portion. According to the present invention,
By using a specially shaped prism, it is possible to manufacture a compact spectroscope that is highly efficient, has no moving parts, and does not depend on polarization. Furthermore, by combining it with a slit and a two-dimensional CCD sensor, it is possible to simultaneously produce multiple points of spectrum. Can be measured with high accuracy.

[0005]

Embodiments of the present invention will be described below in detail. First, a prism and a concave mirror which are components of the optical system of the spectroscopic device will be described. FIG. 1 is an explanatory diagram showing the configuration of the optical system of the spectroscopic device of the present invention. One of the main components of the present invention is a prism 1 having two spherical surfaces. Referring to FIG. 1, a prism 1 has two spherical surfaces 3 and 7, and is formed of a material having a refractive index n. First
Has a point 5 at the center and a radius R1. The second spherical surface 7 has a center at the point 9 and a radius of R2.

An object 11 (usually an input aperture of a spectroscopic device) is provided with an external aberration-free conjugate surface 13 with respect to the first spherical surface 3.
Is arranged in the vicinity of. If the input space medium is air, the astigmatic outer conjugate surface of the spherical surface 3 has the same center at 5
Thus, a circle having a radius R1 is obtained. The first spherical surface 3 forms a virtual image 15 of the object in the vicinity of the stigmatic internal conjugate plane 17 at a distance of R1 / n from the center 5. In other words, after refraction by the spherical surface 3, the light from the object 11 spreads so that the point 15 is a light source.

[0007] The point 15 is located at the intersection of the circle 17 and the circle 19 which is the aberration-free internal conjugate surface of the second prism spherical surface 7. A circle 19, which is a stigmatic internal conjugate surface of the second prism spherical surface 7, has a center of 9 and a radius of R2 / n. Therefore, the second spherical surface 7 is located on the external conjugate surface 23 having no aberration.
A second virtual image 21 is formed. The aberration-free outer conjugate surface 23 is also a circle having a center of 9 and a radius of R2 * n. Therefore,
Light is output from the prism 1 as if the light were emitted from the point 21.

In the image, the center 29 of the curve is at points 21 and 25
Is relayed to the concave mirror 27 arranged substantially in the middle of the above. The light reflected by the concave mirror 27 is concentrated on a point 25. The reflected light again reaches the second spherical surface 7 of the prism and focuses on the fourth virtual image 31. Finally, the first spherical surface 3 of the prism forms a real image 33 at the last imaging point. The points 31 and 33 are located near the aberration-free conjugate plane of the first surface 3 of the prism. Ray path 34 shows the path of a single wavelength ray near the center of the spectral region to be covered. In the case of other wavelengths, the position of the virtual image is slightly shifted due to the difference in the refractive index of the material of the prism. The actual displacement is the (up and down) shift of the position of the final image 33 by the wavelength constituting the spectrum on the image plane 35 substantially perpendicular to the direction of the incident light.

FIG. 2 is an explanatory diagram showing a procedure for designing the optical system of FIG. First, the radius R1 of the first spherical surface 3 of the prism 1 is selected, and the refractive index n of a given prism material
Determines the conjugate planes 13 and 17 having no aberration.
The object 11 and its first virtual image 15 are arranged on a line 16 passing through the center 5 of the first spherical surface 3 of the prism 1. Second
Then, the distance between the object 11 and the final image 33 is selected. Then, the fourth virtual image 31 is a line 32 connecting the center 5 of the first spherical surface 3 of the prism and the final image 33 and the aberration-free internal conjugate plane 1
It is located at the intersection with 7.

Third, the radius R2 of the second prism spherical surface 7
Is selected, and the conjugate planes 19 and 23 having no aberration are determined. For the first virtual image 15 to be imaged on the stigmatic internal conjugate surface 19 of the second prism spherical surface 7, the center 9 of the second prism spherical surface 7 is located on the center 15 on the arc 18 having the radius R2 / n. Be placed. The distance between the center 5 and the center 9 affects the resolution. Fourth, a second virtual image is formed at the intersection of a straight line 20 passing through the center 9 of the second prism spherical surface 7 and the first virtual image 15 and the astigmatic outer conjugate surface 23 of the second prism spherical surface 7. 2
1 is arranged.

Fifth, a third virtual image 25 is arranged on a straight line 30 passing through the center 9 of the second prism spherical surface 7 and the fourth virtual image 31. With respect to center 9, points 31 and 25 are determined by the well-known law of refraction. Sixth, the reflecting mirror 2 is arranged such that the second virtual image is relayed to the third virtual image position 25.
7 is determined. Second prism spherical surface 7
The radius (R3) of the curve of the reflecting mirror 27 is selected so that it is appropriately separated between the mirror 27 and the mirror.

Seventh, to optimize performance, computerized optical design techniques that balance unremovable system aberrations over the entire target wavelength can be used. This approach is known to generate a first answer that allows the program to quickly converge to a good answer.

The selection of the material of the prism depends on the light conductivity and dispersion (change in the refractive index depending on the wavelength) in the target wavelength band. In the visible wavelength band, glass prisms and CCD elements are combined to form high performance devices. In the ultraviolet region, fused silica or magnesium fluoride can be used as the prism material. In the infrared region, depending on the target wavelength,
Calcium fluoride, sodium chloride, magnesium oxide, potassium chloride, potassium bromide are suitable.

FIG. 3 is an explanatory diagram showing one system in which a plurality of types of prisms are used in combination in order to extend the cover wavelength range of the spectroscope. This device is used, for example, to observe infrared light having a wavelength of 2.9 to 13.5 micrometers. External incident light is focused at a point 11 by an optical system (not shown). The light then reaches a spectral beam splitter 51 that transmits wavelengths between 6.5 and 13.5 micrometers and reflects wavelengths between 2.9 and 6.5 micrometers.

The transmitted light 52 is dispersed and re-imaged by the sodium chloride prism 53 and the concave reflecting mirror 55, for example, as described above. The dispersion spectrum of this channel is detected and recorded by the infrared detecting element array 57. The reflected light 59 is reflected by the calcium chloride prism 63
The light is similarly dispersed by the reflecting mirror 65 and forms an image on the second array 61.

In the embodiment described above, the ratio of the object to the image is 1: 1. FIG. 4 shows a lens 79 in the optical path.
The method of adding another ratio to make the ratio different is shown. This method is necessary to match the image size to the available detector 72 size. In this example, the light 73 from the object 71 (for example, including three wavelengths) has a relatively small focal ratio (f /
spread by number). The light is dispersed and re-imaged by the prism 75 and mirror 77 relating to the double astigmatism theory described above.

The dispersed beam 78 reaches a lens 79 that changes the substantial focal length of the system before reaching focus. In the example shown, a convex lens 79 that produces an expanded spectrum is used. An additional advantage of this configuration is that overall image accuracy is improved because the prism 75 operates in a less divergent (small f / number) beam. On the sensor 72 at the focal point, an expanded spectrum is obtained which is distributed over three wavelengths as shown in the upper right of FIG.

Although the optical system for generating the spectrum has been described above, the concave mirror (27, 55, 65, 77) is used as a concave mirror (27, 55, 65, 77) in order to increase the permissible error with respect to the displacement of the mounting position and improve the quality of the optical image. Symmetrical conical shapes can be used. Furthermore, the spherical surface of the concave mirror and the spherical surface of the prism can be made coaxial in order to simplify the optical alignment.

The tolerances affected by the air space between the second spherical surface of the prism and the concave mirror are the most critical.
However, known manufacturing errors (eg, radius and thickness) can be corrected during assembly. By adjusting the focus or slightly moving the focal plane, the main part of the error (the assembly error due to the assembly or the influence of heat) can be corrected. By making the cylindrical edge of the prism coaxial with the center of the concave mirror, the shape of the prism can be simplified. This allows the prism to be manufactured by a relatively simple method using conventional optical techniques, where the accuracy can be verified using simple mechanical tools.

By using only spherical surfaces for the prisms and mirrors, satisfactory image accuracy can be achieved as is. However, the accuracy of the image is further improved by making the mirror a spherical surface (at a wavelength of 632.8 nanometers) separated from the spherical surface by two to four wavelengths.

Next, an example of the configuration of the entire optical system of the spectrometer will be described. FIG. 5 is an explanatory diagram illustrating an example of the configuration of the entire optical system of the spectrometer in the visible region. The spectroscopic device 80
A dispersive optical system including the prism 81 and the concave mirror 82, an input optical system for inputting light emitted from an object to the dispersive optical system, and a detecting unit for detecting a spectrum generated by the dispersive optical system.

Lens 88 as a component of the input optical system
Focuses light emitted from the measurement object 89 (for example, a color print on the XY movable table) at the input point (11 in FIG. 1) of the dispersive optical system. As the lens 88, a commercially available camera interchangeable lens can be used. Half mirror 8
Reference numeral 6 reflects a part of the light from the object to be measured at a fixed rate, and inputs the reflected light to the color CCD camera 87. Color CCD
As the camera 87, a commercially available camera can be used.
A color video signal (for example, an NTSC signal) including the spectrum measurement range of the measurement target 89 is output. Note that the half mirror 86 and the CCD camera 87 are for allowing the user to easily specify the location to be measured, and are not necessary for the spectrum measurement itself.

The slit 85 is provided at the input point of the dispersion optical system (FIG. 1).
This is a plate having a rectangular opening (slit) arranged in 11). The length of the opening in the longitudinal direction depends on the magnification of the dispersive optical system and the size of the CCD element serving as the detection means.
For example, it is 5 mm, and the width of the opening is, for example, about several tens to 100 microns. If the light amount is sufficient, the narrower the aperture, the better the wavelength resolution. The longitudinal direction of the opening is perpendicular to the direction in which light is dispersed by the dispersion optical system. Therefore, light passing through each point of the slit is dispersed in a direction perpendicular to the longitudinal direction of the slit,
On the CCD chip in the upper part of FIG. 5, which is an image forming point (33 in FIG. 1), a two-dimensional optical signal whose spectrum is the position of each slit in the horizontal direction and the spectrum of each point of the slit in the vertical direction is formed.

The plane mirror 84 is provided to change the direction of the input light by approximately 90 degrees in order to easily take in the input light, and the device can be designed without using it. It is. Further, the direction of the light before being dispersed and formed into an image may be changed by a plane mirror. Further, in FIG. 5, the enlargement lens 79 as shown in FIG. 4 is not used, but it is of course possible to use it.

A monochrome CCD camera 83, which is a detecting means for detecting the dispersed spectrum light, is arranged at an image point (33 in FIG. 1), detects the intensity of the two-dimensional spectrum light, and outputs a video signal. I do. As the CCD image pickup device, for example, a chip size is 6 × 5 mm, the number of pixels is about 700 × horizontal × 500, and a wavelength range is 400 to 110.
A commercially available product of 0 nanometers can be used. The CCD image pickup device (chip) is mounted at a position rotated by 90 degrees, and one line of horizontal scanning of the CCD corresponds to spectrum data (one vertical line on the CCD chip in FIG. 5) at an arbitrary point of the slit. . The output video signal may be, for example, an NTSC video signal.

FIG. 6 is a block diagram showing a configuration example of the entire spectroscopic system. The output signal of the color CCD camera 87 of the spectroscopic device 80 is input to the monitor device 90, and the measurement target (for example, a color print) 8 on the XY movable table 96 is output.
A predetermined area including nine spectrum measurement areas (rectangular areas surrounded by dotted lines) is displayed. The dotted rectangle indicating the spectrum measurement area on the monitor screen is previously written on the screen, or a rectangular image is generated electronically and combined with the image from the CCD camera 87.

The output signal of the monochrome CCD camera 83 for spectrum detection is input to the computer 91, and luminance information corresponding to each pixel is captured as a digital image signal by, for example, a well-known video capture function.
As the computer 91, for example, a commercially available personal computer or workstation can be used, and a video signal input means such as a video capture card is mounted. A well-known keyboard 92, mouse 93, CRT display 94, and printer 95 are connected to the computer 91.
The Y movable table device 96 is connected by, for example, a well-known RS-232C interface.

The user first sets the monitor 90 so that the spectrum measurement area is at a desired position on the measurement target 89.
And operate keyboard 92, mouse 93, etc.
Move the Y movable table. Next, the computer 91
Is instructed to take in the output signal of the CCD camera 83 for spectrum measurement.

The computer 91 captures a video signal using, for example, a video capture function,
Various corrections relating to the D element and spectrum analysis with a desired resolution are performed, for example, a three-dimensional graph is displayed on the display 94, or printed by the printer 95. The resolution in the longitudinal direction of the slit can be arbitrarily set, for example, as long as the maximum value is 150 or less.

FIG. 7 is an explanatory diagram showing the configuration of a second embodiment of the input optical system of the spectrometer. For example, when measuring a light-emitting object such as a discharge tube 98 or a light bulb, the pinhole 9 having no aberration can be measured even if the efficiency is low.
7 can be used. As an input optical system of the second embodiment of the spectroscopic device 80, a pinhole 97 is provided instead of the lens 88 of FIG. 5 which is the first embodiment.

An image of the object to be measured is formed on the slit 85 by the pinhole 97, and only the light that reaches the slit portion of the image is input to the dispersive optical system, dispersed and reaches the CCD camera 83. If the discharge tube 98 is arranged on, for example, an XY movable table, a two-dimensional spectral distribution in the discharge tube 98 can be automatically measured, which is useful for analyzing a discharge state, designing electrodes, and the like. Pinhole 97 and slit 85
Passes through the prism 81 and the concave mirror 82 only in a limited range. Therefore,
The prism 81 and the concave mirror 82 may be cylindrical surfaces instead of spherical surfaces.

FIG. 8 is an explanatory diagram showing the configuration of a third embodiment of the input optical system of the spectrometer. For example, a three-dimensional object 1
When measuring spectra at a plurality of points of 00, an optical fiber 99 can be used. As the input optical system of the third embodiment of the spectroscopy device 80, the end of the optical fiber 99 aligned with the position of the opening of the slit 85 of FIG. Optical fiber 99
For example, a lens is attached to the other end 101 of the object 100.
The light emitted from the measurement point of the object 100 is taken into the optical fiber at a position away from the optical fiber.

By arranging, for example, 100 optical fibers 99 and arranging the other end 101 two-dimensionally in 10 rows × 10 columns, it is possible to simultaneously input spectrum information at 100 two-dimensional measurement points of the object. . Others
The arrangement of the other end 101 is arbitrary, and a plurality of objects can be measured at the same time.

While the embodiment of the present invention has been disclosed above, the present invention may have the following modifications. In the embodiment, the monitor means and the spectrum measuring means are separated from each other. However, the monitor image may be taken into the computer 91 and displayed on the display device simultaneously with or after switching the spectrum information. As the sensor, C
Although an example using a CD image sensor has been disclosed, any sensor other than a CCD, such as a CMOS sensor, a photodiode array, or an image pickup tube, can be used as long as the sensor can detect light intensity.

Although an example using an XY movable table has been disclosed as an embodiment, if it is difficult to move an object, the spectroscopic device 80 may be moved or rotated. In the embodiment, the example in which the optical path is turned back by the concave mirror is disclosed. However, the spectral device can be configured only by the prism without the concave mirror. In this case, the number of components is reduced, but the size of the apparatus is increased and the resolution is deteriorated.

[0036]

As described above, in the present invention,
The spectroscopic device includes a prism having two spherical surfaces and a spectroscopic unit including a concave mirror having a spherical surface, and further includes a slit mounted on an incident portion of the measured light, and a two-dimensional optical sensor mounted on an image forming portion. Have. Therefore, according to the present invention, by using the prism and the concave mirror, there is an effect that it is possible to manufacture a small-sized spectroscope having high efficiency, having no movable portion, and having no polarization dependency. In addition, by combining with a slit and a two-dimensional CCD sensor,
At the same time, there is an effect that a spectrum at multiple points can be measured with high accuracy. Furthermore, there is an effect that an object of an arbitrary size at an arbitrary distance can be measured from a minute object to a huge structure at a distance. Therefore, by using the spectroscopic device of the present invention, color measurement, analysis, discrimination, and the like of any display such as printed matter, agricultural products, liquid crystal, CRT, and projection type can be processed at high speed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of an optical system of a spectroscopic device of the present invention.

FIG. 2 is an explanatory diagram showing a design procedure of the optical system of FIG. 1;

FIG. 3 is an explanatory diagram showing one system in which a plurality of types of prisms are used in combination.

FIG. 4 is an explanatory diagram showing a method of adding a lens 79 to the optical path to obtain another ratio.

FIG. 5 is an explanatory diagram showing an example of the configuration of the entire optical system of the spectroscopic device in the visible region.

FIG. 6 is a block diagram illustrating a configuration example of an entire spectroscopic system.

FIG. 7 is an explanatory diagram showing a configuration of a second embodiment of the input optical system of the spectroscopic device.

FIG. 8 is an explanatory diagram showing a configuration of a third embodiment of the input optical system of the spectroscopic device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Prism, 3 ... 1st spherical surface, 7 ... 2nd spherical surface, 11
... object, 13 ... external conjugate plane, 15 ... virtual image of the object, 17
... internal conjugate plane, 18 ... arc, 19 ... conjugate plane, 20, 30,
32: straight line, 21: second virtual image, 23: external conjugate plane, 2
Reference numeral 5: third virtual image, 27: concave mirror, 29: center, 31: fourth virtual image, 33: real image of an imaging point, 35: imaging surface, 51 ...
Beam splitter, 52: transmitted light, 53, 63: prism, 55, 65: concave mirror, 57, 61: detecting element array, 59: reflected light, 71: target object, 72: sensor, 73
... light beam, 75 ... prism, 77 ... concave mirror, 78 ... scattered beam, 79 ... lens, 80 ... spectroscope, 81
... Prism, 82 ... Concave mirror, 83 ... CCD camera, 84
... plane mirror, 85 ... slit, 86 ... half mirror, 87
... CCD camera, 88 ... Lens, 89 ... Measurement object, 9
0: Monitor device, 91: Computer, 92: Keyboard, 93: Mouse, 94: Display, 95: Printer, 96: XY movable table, 97: Pinhole, 98
... discharge tube, 99 ... optical fiber

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G020 AA03 AA04 AA05 CA01 CB04 CB31 CB42 CB43 CC02 CC14 CC15 CC42 CC47 CD06 CD12 CD13 CD24 CD33 CD52 2H042 CA17 2H087 KA12 TA03 TA04

Claims (5)

[Claims] 1. A spectroscopic apparatus comprising: a spectroscopic unit comprising a prism having two spherical surfaces each having an inner and an outer conjugate surface, and a concave mirror having a spherical surface. 2. A slit mounted on an incident portion of the light to be measured so that a longitudinal direction is perpendicular to a direction in which the light is dispersed by the spectral unit, and a two-dimensional light mounted on an image forming unit of the spectral unit. The spectroscopic device according to claim 1, further comprising a sensor. 3. An input optical system for forming an image of an object to be measured at the position of the slit, movable table means for moving the object to be measured at least in a direction perpendicular to the longitudinal direction of the slit, and the movable table means The spectrometer according to claim 2, further comprising: a computer that controls the temperature and analyzes an output signal from the optical sensor. 4. The spectroscope according to claim 3, wherein said input optical system is a pinhole means. 5. A plurality of optical fibers mounted on the incident portion of the light to be measured, the plurality of optical fibers having one end linearly arranged so that the arrangement direction is perpendicular to the direction of light dispersion by the dispersing means, The spectroscopic device according to claim 1, further comprising a two-dimensional optical sensor attached to the imaging unit.