Method For Analyzing Spectral Data Using Halograms

Abstract

A signal obtained by an analytical instrument is converted into a light and shade spectrum by an electron exposure unit, the said light and shade spectrum then being formed into a hologram. Unknown samples are qualitatively and quantitatively analyzed by correlating the hologram formed by a given unknown sample with the hologram of a known sample. Further, if the output signal from an interference spectrometer is fed into the exposure unit, a light and shade spectrum in the form of a hologram is produced. By applying Fraunhofer diffraction, Fourier transformed spectrum in reverse corresponding to a wave number is derived from the said hologram.

Description

This invention relates to a method and apparatus for processing data in an analytical instrument. More particularly, this invention relates to a method and apparatus for processing the data obtained from an analytical instrument into data from which the spectral pattern of the specimen can be discerned.

Generally, data provided by an analytical instrument is recorded on chart paper as a two-dimensional spectrum. For example, in the case of nuclear magnetic resonance apparatus, the abscissa of the recorded spectrum represents the swept high frequency and the ordinate represents the signal intensity. The spectrum thus obtained contains micro-information pertaining to the sample, the said information being analyzed by comparing the said spectrum with the spectrum of a known sample. The comparison is usually entrusted to the judgment of the research worker involved with the result that when the spectrum of the known sample and the spectrum of the unknown sample have similar peaks, it is difficult to make a precise comparison. Again, this method is extremely time consuming inasmuch as the unknown spectrum has to be compared with the spectra of a large number of known samples.

Another method of data processing is to use an interference spectrometer. In this case, a ray of light generated by a light source is split into two rays of light, one ray being reflected by a movable reflector, the other by a fixed reflector. The two light rays are then unified by the beam splitter. As a result, the increase or decrease of the light intensity is determined by the interference of the two light rays and detected by a detector. Further, by scanning the said movable reflector, the variation of the interference pattern, determined by the difference in the optical path, is also detected. Advantages claimed for this type of spectrometer are high S/N (signal to noise) ratio and short measuring time. Disadvantages, however, as in the case of the aforegoing, include time consuming data processing, caused by the fact that the detected spectrum is a Fourier transformed spectrum of the light generated by the light source.

In accordance with this invention, the output signal from any one of a number of types of analytical instrument is converted into a one-dimensional spectrum such as a light and shade or uneven spectrum. Subsequently, a hologram of such a spectrum is formed and the pattern is discerned by correlation. Correlation is carried out by fixing two holograms together and irradiating them with a laser beam. By so doing, the spectrum obtained by the analytical instrument is automatically analyzed both speedily and easily. It should be mentioned here, however, that since the patterns of any two two-dimensional spectra are different due to the difference in sample quantity and density, it is impossible to discern the hologram pattern by correlating the said two two-dimensional spectra.

Again, in accordance with this invention, the output signal from an interference spectrometer is similarly converted into a one-dimensional spectrum such as a light and shade or uneven spectrum, the said spectrum serving as a hologram. Pattern discernment is also effected by correlation. Since, in this case, the hologram is reversely Fourier transformed by Fraunhofer diffraction, the data obtained from the interference spectrometer is optically analyzed both speedily and easily.

One object of this invention is to provide a method and apparatus for processing data optically in an analytical instrument.

Another object of this invention is to provide a method and apparatus for processing data rapidly in an analytical instrument.

Various other objects and advantages of this invention will become apparent from the following detailed description made with reference to the accompanying drawings in which:

FIG. 1 shows a nuclear magnetic resonance apparatus according to this invention.

FIG. 2 shows an output signal wave form of the nuclear magnetic resonance apparatus recorded on chart paper.

FIG. 3 shows a light and shade spectrum obtained by the apparatus shown in FIG. 1.

FIG. 4 shows an optical system for producing a hologram.

FIG. 5 shows a optical system for correlating any two holograms.

FIG. 6 shows another embodiment for producing a one dimensional spectrum.

FIG. 7 shows a mass spectrometer according to this invention.

FIG. 8 shows a liquid chromatograph according to this invention.

FIG. 9 shows a spectrometer according to this invention.

FIG. 10 shows an interference spectrometer according to this invention.

FIG. 11 shows a light and shade spectrum produced by the spectrometer shown in FIG. 10.

FIG. 12 shows an optical system for carrying out Fraunhofer diffraction.

Referring to FIG. 1, a sample is enclosed in a probe 1, DC and high frequency magnetic fields are produced around the said probe by an electro-magnet 2 and a high frequency coil 3 to which a high frequency is supplied by a sweep generator 4. By sweeping the high frequency, high frequency energy is absorbed by the sample at certain frequencies. The absorption signal is detected by a circuit 5 and a detector 6. FIG. 2 shows the output signal wave form of the detector 6. Normally, the spectrum shown in FIG. 2 is obtained by means of a recorder. According to this invention, however, the said spectrum is converted into a light and shade or uneven spectrum by feeding the output signal of the detector 6 into an electron beam exposure unit 7.

An electron beam produced by a filament 8 is controlled by a grid 9 in circuit with the detector 6, accelerated by an anode 10, and focused by an electron lens 11. The focused electron beam is deflected by a deflecting coil 12 and irradiated on a movable plate 13 arranged on rollers 14 so that the electron beam is scanned at right angles to the direction of plate movement. By so doing, a light and shade spectrum as shown in FIG. 3 is recorded on the plate 13 according to the intensity of the electron beam.

The said light and shade spectrum is then converted into a hologram. FIG. 4 shows an embodiment for producing such a hologram. In the figure, a laser beam generated by a laser 21 such as a He-Ne laser is split into two beams by a beam splitter 22. One beam is diffracted by a plate 23, on which the light and shade spectrum is recorded, and then irradiated on a film plate 24. The other beam is reflected by a reflector 25, bent by a prism 26 and then irradiated on the said film plate 24. By so doing, the two beams form an interference pattern, viz, a hologram which is recorded on the film plate 24.

The recognition of the spectrum pattern obtained by the analytical instrument can be effected by the hologram according to this invention. Correlation of any tow holograms is effected by fixing them together and irradiating a laser beam on the fixed holograms. FIG. 5 shows the optical system for effecting the above correlation. In the figure, a laser beam is irradiated on and diffracted by the fixed holograms 31 and 32. The diffracted laser beam is then focused on a screen 33 by a cylindrical lens 34. If both holograms 31 and 32 have the same pattern, a light spectrum is produced on the screen 33. Conversely, if their patterns are different, the light spectrum does not appear on the screen. Therefore, by using a hologram of an unknown sample as the hologram 31 and a hologram of a known sample as the hologram 32, the unknown sample can be qualitatively analyzed.

It is also possible to quantitatively analyze the unknown sample. The density of the interference pattern changes according to the intensity of the output signal produced by the analytical instrument. In the correlation, even if one hologram has the same pattern as the other, the brightness of the spectrum on the screen changes according to the difference in the densities of the two holograms. This being so, the unknown sample can be quantitatively analyzed by observing the spectrum brightness.

FIG. 6 shows another embodiment using an electro-optics element for forming a light and shade or uneven spectrum. In the figure, a monochromatic light generated by a light source 41 passes through an electro-optics element 42, such as a KDP or ADP element, is focused by a cylindrical lens 47 and then irradiated a silver halide coated plate 43 which is moved by a motor 44. The output voltage of a detector 6 is applied to electrodes 45 and 46. Thus, the transmissivity of the light passing through the electro-optics element varies according to the output voltage of the detector 6 with the result that a light and shade spectrum is recorded on the plate 43. By coating the plate surface with photoresist instead of silver halide, an uneven spectrum can be recorded on the plate.

FIG. 7 shows a mass spectrometer according to this invention. In the figure, an ion beam emitted from an ion source 51 is accelerated by acceleration slits 52 and then passes through a magnetic field produced by an electro-magnet 53 to which an excitation current is supplied by a variable power source 54. The accelerated ion beam is dispersed according to the ion mass-to-charge (m/e) ratio by the said magnetic field. Only ions having a certain mass-to-charge ratio pass through a slit 55, the said ions being detected by an ion collector 56. The output signal of the collector 56 is fed into the electron beam exposure unit 7 via an amplifier 57. By varying the intensity of the magnetic field produced by the electro-magnet 53, a light and shade or uneven spectrum is recorded by the electron beam exposure unit. The said spectrum is then converted into a hologram by the optical system shown in FIG. 4.

FIG. 8 shows a liquid chromatograph according to this invention. An eluant 61 in an eluant reservoir 62 is fed into a column 63, containing a fixed phase 64 such as ion exchange resin, via a pipe 65 by a pump 66. A liquid sample is injected into the column 63 via a sample inlet port 67 which is separated into its various components according to the chromatograph phenomenon by the fixed phase. The separated components are then detected by a detector 68, and the eluant and liquid sample passed through the detector 68 is collected in a reservoir 69. The signal detected by the detector 68 is fed into the electron beam exposure unit 7 via an amplifier 70 so as to record a one-dimensional spectrum.

FIG. 9 shows a spectrometer according to this invention. In the figure, light from a light source (not shown) passes through an inlet slit 81 into a monchromator 82. The light is reflected by a reflector 83 and irradiated on a rotatable grating 84 so that the irradiated light is dispersed in accordance with the wavelength. The dispersed light is reflected by a reflector 85, passes through an outlet slit 86 and is detected by a detector 87 such as a photomultiplier. The detected electrical signal is fed into the electron beam exposure unit 7 via an amplifier 88 so as to record a one-dimensional spectrum such as a light and shade or uneven spectrum.

FIG. 10 shows an interference spectrometer according to this invention. In the figure, a light generated by a light source 91 is made to form a parallel ray of light by a lens 92. The parallel light is split into two rays of light by a beam splitter 93 so that the split rays are directed to movable and fixed mirrors 94 and 95 respectively. The said movable mirror 94 is moved at a constant speed by a motor 96. The light reflected by the movable mirror 94 passes through the beam splitter 93 and is focused on a detector 97 by a lens 98. The amplitude Fa (.nu.) of this light is expressed as follows:

Fa (.nu.) .varies. A (.nu.) cos 2.pi.(ft - 21.nu.)

where A(.nu.) is the amplitude of the light generated by the light source 91, f is the light frequency, .nu. is the wave number (i.e., reciprocal of wave length) of the light and l is the distance between the beam splitter 93 and the movable mirror 94.

On the other hand, the amplitude Fb (.nu.) of the light reflected by the fixed mirror 95, which is similarly reflected by the beam splitter 93 and focused on the detector 97 by the lens 98, is expressed as follows:

Fb (.nu.) .varies. A (.nu.)cos 2 .pi.[ft- 2 (l +.DELTA.) .nu.]

where .DELTA. is half the optical path difference between the two rays of light.

The said two rays of light cause an interference phenomenon to occur on the detector screen, the amplitude F (.DELTA.) of the detected light being expressed as follows: ##SPC1##

Further, the energy intensity of the light is equal to F.sup.2 (.DELTA.) and is expressed as follows:

Since I (.DELTA.) is proportional to the squared average value of the optical disturbance, the time factor included in the amplitude F (.DELTA.) disappears.

I (.DELTA.) is represented as an interferogram which is a Fourier transformed spectrum of the energy intensity of the light generated by the light source. A spectrum corresponding to the wave number is obtained by carrying out the Fourier transformation of I (.DELTA.) in reverse. Normally, I (.DELTA.) is transformed by an electronic computer by which means transformation is extremely complicated and elaborate. Optical transformation, on the other hand, as effected by this invention, simplifies the process appreciably.

The signal detected by the detector 97 is amplified by an amplifier 99 and fed into the electron beam exposure unit 7. The resultant light and shade spectrum as shown in FIG. 11 is then recorded on the plate 100, the information intensity contained thereon being expressed as follows:

where .gamma. is the gradient of the linear part of the plate transfer curve and x is defined by the relation 2 .DELTA./M where M is a constant.

Further, since the light and shade spectrum recorded on the plate 100 represents the interference pattern, that is to say, the hologram formed by the two rays of light, the reverse Fourier transformed spectrum can be obtained therefrom by Fraunhofer diffraction. FIG. 12 shows the optical system of this said diffraction. Here, a monochromatic light 101, such as a laser light, is irradiated on the plate 100 where the light and shade spectrum is recorded and diffracted. The diffracted light is then focused on a screen 102 by a cylindrical lens 103.

In this system, the amplitude T(x) of the diffracted light is expressed as follows: ##SPC2##

Now, according to Fraunhofer's diffraction theory, the amplitude D (.xi.) of the spectrum projected on the screen 102 is given as follows: ##SPC3##

where .xi. is the distance from the screen center 0, R is a constant defined by the relation 2 .pi. .nu.'/f, is the wave number of the incident light 101 and is the focal length of the cylindrical lens 103, thus, the energy intensity I (.xi.) of the light projected on the screen is equal to D.sup.2 (.xi.) and is expressed as follows:

In the above relationship, the first term expresses the zero order transmission diffracted light, the second term expresses the +1 order diffracted light and the third term expresses the -1 order diffracted light. Considering the +1 order diffracted light, when

light possessing energy .pi..sup.2 .nu..sup.2 A.sup.4 (.nu.) is projected on the screen 102. As a result, when a light spot is projected on a point which is at a distance d from the center 0, the wave number of the light spot spectrum is calculated by the following relationship:

.nu. =d .nu.'/M f'

Consequently, the entire spectrum is obtained by calculating the wave number of each light spot spectrum appearing on the screen. Since, however, the diffracted light rays of the +1 and -1 order diffracted light are symmetrical, it is sufficient to calculate one order only. In addition, the spectrum pattern can be discerned by means of a hologram by using the optical system shown in FIG. 5.

Claims

Having thus described the invention with the detail and particularity as required by the Patent Laws, what is desired protected by Letters Patent is set forth in the following claims:

1. A method of analyzing spectral data received from an analytical instrument which produces the information signal from a sample comprising the steps for:

A. converting the information signal into a one-dimensional spectrum;

B. forming a hologram of said one-dimensional spectrum;

C. juxtaposing the hologram of step B with holograms of known samples and passing light therethrough;

D. observing the light passed therethrough to correlate the spectrum of the sample with the known samples.