TWI472725B - Lens-chromatism spectrum measurement device and spectrum measurement method - Google Patents

Description

Lens color difference spectrum measuring device and spectral measuring method

The present invention relates to a lens color difference type spectral measuring device and a method for performing a spectral measurement using the device.

A spectrometer or spectrometer is a device that decomposes complex light into spectral lines, and then through the display and analysis of the instrument, and is often used to compare components such as elements contained in the analysis object. The conventional spectrometer or spectrometry technology is a spectroscopic spectrum type, which mainly transmits the light emitted by the light source through the dispersive element, and the light of different wavelengths contained therein can be separately arranged at different positions according to the optical characteristics of the dispersive element. Finally, the wavelength of each of the rays is discriminated by detecting the position of the light at each of the separated wavelengths.

Figure 1 shows a conventional krypton spectrometer that uses a 稜鏡6 to split the incoming light into different sources of light at different locations. Figure 2 shows a conventional grating spectrometer that uses a grating 7 to split the incoming light into different sources of light at different locations. The elements 61 and 71 in the two examples are detected as being separated into light rays at different positions, and are light detecting elements.

Although the detection technology of ultra-dense pixels and ultra-high resolution capability can be produced by the improvement of the process technology, the detection capability of the spectrometer can be improved, but the spectroscopic mechanism of the dispersive element (such as germanium or grating) is still used for the spectral detection. There are certain limits. Although the light can be amplified or the imaging position is extended, the phase of the light of different wavelengths after the splitting can be amplified. For position, but these methods will introduce complex optical noise at the same time, or increase the volume of the light detecting device. Another solution for increasing the resolution of the relative positions of light rays of different wavelengths is to achieve a better spectroscopic effect by changing the line width of the grating, which is quite difficult to manufacture and costly.

Furthermore, for the limitation of the optical limit of the two dispersive elements of 稜鏡 and grating, a Fabry-Perot interferometric (or interferometric) spectrometer is further developed, which has a very high dispersion rate for the measured light, thus Extremely high spectral resolution is available, but the spectrometer requires relatively complex optical system components and electronic circuitry to achieve its powerful spectral detection capabilities, resulting in high price points.

In addition, U.S. Patent No. 7,483, 135 B2 discloses an astigmatic aperture (Astigmatic Aperturing) for a confocal spectrometer, which is different from the conventional method of using a confocal lens with a focusing lens (pinhole), which utilizes an astigmatic lens. The horizontal axis and the vertical axis have different magnification characteristics and are matched with pinholes, which successfully focus the light to be measured on two different focal planes, which can more effectively filter out defocused light and contribute to the position of the pinhole. Arrangement and aperture size arrangement to facilitate the splitting and judgment of the back end monochromator, but it does not directly use the optical astigmatism method for spectral color separation and detection. In addition, in 2011, Zheng Zhongxiang et al. published the paper "Development of a Freedom Laser Optical Ruler for Tool Machine Error Detection", which revealed that it is installed in a semiconductor mine using a simple arrangement of a grating and a one-dimensional photodetector. The wavelength of the semiconductor laser can be quantitatively measured (about 10 ^-6 ), and the function of detecting and feedback control wavelength is realized, but the resolution is limited by the resolution of the one-dimensional photodetector. Ability and the size of the laser spot. For example, "Chromatic aberration short-wave infrared spectroscopy: Nanoparticle spectra without a spectrometer" (Anal. Chem., Vol. 85, pp. 137-1071) published by Jason K. Streit et al. in 2013 discloses that a general fluorescent microscope is used. For short-wavelength infrared (SWIR), which has quite serious lens chromatic aberration defects, the surface of the carbon nanotube is detected. The mechanism is to use different wavelengths to have different focus positions for the same objective lens. Finally, the difference in depth of focus is determined by the image device. To determine the characteristics of the surface of the carbon nanotubes.

The main object of the present invention is to provide a lens chromatic aberration type spectral measuring device, which can greatly improve the discrimination ability for light of different wavelengths compared with the existing light detecting device, and can be easily achieved without complicated electronic processing and calculation. The utility model utilizes a general optical lens to have different focus characteristics for incident light of different wavelengths, and the astigmatism detecting component has ultra-high sensitivity characteristics for defocus signals of different focal points, thereby greatly improving the analytical ability for the spectrum to 10 ^-3 nanometer (pm) or less.

Another object of the present invention is to provide a lens color difference spectrum measuring device which has the advantages of high reliability, small volume, high economic efficiency, high accuracy, and simple structure of the device itself.

To this end, the spectral measuring device of the present invention comprises a light collecting system and an astigmatism detecting system, wherein the light collecting system is composed of a pinhole and a color difference focusing lens, which can receive different signals emitted by a light source. Light of a wavelength and focusing the light at different focal positions according to its different wavelengths, after which the light is further introduced into an astigmatism detection system for spectral measurement of the light, wherein the astigmatism detection system is comprised of a focusing lens , a light guiding lens group, an astigmatic lens and an optical detector.

The spectral measuring device of the present invention is compared with the above-mentioned document disclosed by Zheng Zhongxiang et al. in 2011. The detection mechanism used in the document is "traditional grating spectrometer detection technology", and the invention uses the technique of "lens color difference type". The splitting elements used in the two are different, and the invention of the present invention is relatively easy to implement and the cost and process difficulty are greatly reduced.

Moreover, the spectral measurement device of the present invention is compared with the above-mentioned document disclosed by Jason K. Streit et al., the biggest difference being the difference between the signal detecting devices used by the two; and Jason K. Streit et al. CCD and other imaging devices calculate the focus position by judging the spot size. However, the sensitivity is limited by the CCD's own ability to solve the problem. Therefore, a more complex image recognition software is needed. The invention is based on the detection mechanism of the astigmatism method. In this case, the variation of the focus point can be obtained simply by the voltage change, which is more intuitive and easy to analyze and process.

Features of the present invention can be more easily understood by the embodiments and the drawings disclosed in the following embodiments.

1‧‧‧Spectrum measuring device

2‧‧‧Lighting system

21‧‧‧ pinhole

23‧‧‧chromatic aberration focusing lens

25‧‧‧ Focus position

3‧‧‧ astigmatism detection system

31‧‧‧focus lens

33‧‧‧Light guiding lens set

331‧‧‧Mirror

333‧‧‧ Collimating lens

335‧‧ ‧beam splitter

35‧‧‧ astigmatic lens

37‧‧‧Photodetector

5‧‧‧Light source to be tested

6‧‧‧稜鏡

61‧‧‧Light detection components

7‧‧‧Raster

71‧‧‧Light detection components

F‧‧‧Focus area

1 is a schematic view of a prior art krypton spectrometer; FIG. 2 is a schematic view of a prior art grating spectrometer; FIG. 3 is a perspective view of the spectrometric measuring device of the present invention; Schematic diagram of the dispersion technique of light; FIG. 5 is an example of the relationship between the wavelength change of the light passing through the color difference focusing lens and the focus position; FIG. 6 is a graph showing the relationship between the focus position and the voltage obtained by the astigmatism method of the photodetector. An example; and FIG. 7 shows an example of a displacement signal diagram of a distance difference (Δ f ) between two focal points corresponding to light of two different wavelengths of 650 nm and 790 nm measured by a photodetector.

Fig. 3 is a view showing an embodiment of the lens color difference spectrum measuring device of the present invention.

The spectral measuring device 1 mainly comprises a light collecting system 2 and an astigmatism detecting system 3. The light collecting system 2 is composed of a pinhole 21 and a color difference focusing lens 23, and the astigmatism detecting system 3 is composed of a focusing lens 31, a light guiding lens group 33, an astigmatic lens 35 and a light detector 37. Composition.

As shown in FIG. 3, the light having different wavelengths emitted by a light source to be tested 5 enters the light collecting system 2 of the spectral measuring device 1 of the present invention, and the light passing through the pinhole 21 is incident and passed through the color difference focusing lens 23. Wherein, the color difference focusing lens 23 can be a general optical lens, a ball lens or a focusing lens, etc. having any focus or any numerical aperture (N/A), one of which A practical example is a lens having a numerical aperture of 0.4, as described below.

After the incident light passes through the chromatic aberration focusing lens 23, that is, due to the principle of optical chromatic aberration (refer to FIG. 4, that is, optically, the lens cannot focus the color light of various wavelengths at the same point; since the lens has different wavelengths of light The different refractive indices, which occur as "dispersion phenomena", cause the light to be focused at different positions depending on the different wavelengths it has. The relationship between the different wavelengths of the light and its corresponding focus position is as follows:

Wherein f denotes the focal length of the color difference focusing lens 23, and the focal length can be used to derive the position of the actual beam focus; B and C are the lens material coefficients of the Cauchy's equation; λ represents the wavelength of the incident light; P _Lens represents the color difference The lens constant of the focusing lens. For example, a plastic aspherical lens with a numerical aperture of 0.4 is used as the color difference focusing lens 23, and its effective focal length is 0.33 mm; FIG. 5 shows the different wavelengths of the light and the corresponding focus focus position when the color difference focusing lens 23 is used. A relationship graph. F in Fig. 3 is an illustration of a focus area formed by different focus focus positions of light of respective wavelengths.

After the light passes through the color difference focusing lens 23 and is focused at different positions according to different wavelengths, it then enters the astigmatism detecting system 3 of the spectral measuring device 1; the light passes through the focusing lens 31 and the light guiding lens group 33, and It is guided to the astigmatic lens 35. As shown in FIG. 3, the light guiding lens group 33 includes a mirror 331, a collimating lens 333, and a beam splitter 335.

With regard to the astigmatic lens 35, which has different longitudinal and lateral magnification curvatures, different imaging spots will be generated for different focus positions, causing aberrations; such aberrations can be detected by the photodetector 37, thus The position of the focus of the different wavelengths of light is derived, and the signals of different wavelengths of the respective rays are further estimated. Wherein, the photodetector 37 can be any photoelectric conversion component, for example, an optoelectronic detection amplification integration circuit, and it is judged that different voltage positions are used for the photodetector to obtain different voltage values; as shown in FIG. A graph showing the relationship between the focus position and the voltage obtained by using the photodetection amplification integrated circuit as the photodetector 37, which respectively displays Far focus, Focus, and Near Focus. The photoelectric conversion of the photoelectric integrated detection circuit can be used to obtain the relationship between the focus position and the voltage, which is called S-Curve, which can also be called a focus error signal; and after correction, the voltage and displacement can be known. In the relative relationship, the signal signal is accessed and the displacement analysis is performed by the signal acquisition device to determine the actual intersection position, and finally the wavelength of the light wave of the incident light can be determined. 7 is a view showing a difference in focus position between two wavelengths of 650 nm and 790 nm obtained by using a photodetection amplification integrated circuit as the photodetector 37 (P1 is a focus position of light of a wavelength of 650 nm; and P2 is a focus of light of a wavelength of 790 nm). The position of the focal position distance difference (Δ f = P2 - P1) caused by the position. As can be seen from the above, the spectrometry device 1 can detect the difference in the focus position of a light passing through the chromatic aberration focusing lens 23 via the photodetector 37, and can indirectly know the wavelength information of the incident light.

The spectral measuring device 1 of the present invention has a very high spectral resolution capability, even up to a level below 10 ^-3 nm (pm). For example, the spectral relationship can be determined by the data relationship shown in FIG. 5 and FIG. The device 1 can obtain a focus position distance difference of about 150 nm or more for a wavelength change of 1 nm; and if the resolution is further improved, it is only necessary to select a color difference focus lens 23 having a suitable P _Lens lens constant or change the color difference. The parameters of the focus lens 23 are focused.

In addition, the commercially available optical disk drive read head also has the structure of the astigmatism detecting system 3 of the spectral measuring device 1 of the present invention as shown in FIG. 3, so the astigmatism detecting system 3 of the present invention can directly use any commercially available model. The CD player read head is replaced by a holographic optical element (HOE), and the optical signal detected by the photodetector 37 is externally captured. The photoelectric signal conversion and the appropriate interface output the relationship between the focus position and the voltage to know the wavelength information of the incident light. From the way of this case, it is possible to obtain a simple and economical spectral measurement method that has not been available in the past.

It should be understood that the illustrative embodiments are merely illustrative of the invention and those skilled in the art Many variations of the embodiments described above can be devised without departing from the scope of the invention. It is therefore intended that all such changes be included within the scope of the following claims and their equivalents.

1‧‧‧Spectrum measuring device

2‧‧‧Lighting system

21‧‧‧ pinhole

23‧‧‧chromatic aberration focusing lens

25‧‧‧ Focus position

3‧‧‧ astigmatism detection system

31‧‧‧focus lens

33‧‧‧Light guiding lens set

331‧‧‧Mirror

333‧‧‧ Collimating lens

335‧‧ ‧beam splitter

35‧‧‧ astigmatic lens

37‧‧‧Photodetector

5‧‧‧Light source to be tested

Claims (11)

A spectrometric measuring device (1) comprising a light collecting system (2) comprising: a pinhole (21) for allowing light having a different wavelength to be emitted from a light source to be tested (5) And a color difference focusing lens (23), wherein the light collected by the pinhole (21) can be respectively focused on different positions according to different wavelengths; an astigmatism detecting system (3) comprising: a focusing lens (31); a light guiding lens group (33); an astigmatic lens (35) having different longitudinal and lateral magnification curvatures; and a photodetector (37); wherein the focusing lens (31) receives The light is focused by the color difference focusing lens (23), and the light guiding lens group (33) directs the light received by the focusing lens (31) to the astigmatic lens (35), and the light is guided through the image The diffusing lens (35) is in turn detected by the photodetector (37). The spectral measuring device (1) of claim 1, wherein the light guiding lens group (33) comprises a mirror (331), a collimating lens (333) and a beam splitter (335). A spectral measuring device (1) according to claim 1, wherein the color difference focusing lens (23) is an optical lens, a ball lens or a focusing lens which can have any focal length or any numerical aperture. The spectral measuring device (1) of claim 1, wherein the photodetector (37) is a photoelectric conversion element. The spectral measuring device (1) of claim 4, wherein the photodetector (37) is photodetectable Amplify the integrated circuit. The spectral measuring device (1) of claim 1, wherein the astigmatism detecting system (3) is a CD player read head. A method for measuring a spectrum includes the following steps: a light source having a different wavelength emitted by a light source to be tested (5) passes through a pinhole (21); and the light passing through the pinhole (21) passes through a color difference Focusing the lens (23) such that the light is respectively focused at different positions according to different wavelengths thereof; and the light that has passed through the color difference focusing lens (23) and has been respectively focused at different positions according to different wavelengths thereof a focusing lens (31) and a light guiding lens group (33) are guided to an astigmatic lens (35) having different longitudinal and lateral magnification curvatures, and the astigmatic lens (35) can correspond to different wavelengths of the light Aberration is caused by different positions of the focus; and the aberration is detected by a photodetector (37) to further obtain the information of each wavelength of the light. The method of claim 7, wherein the light guiding lens group (33) comprises a mirror (331), a collimating lens (333) and a beam splitter (335). The method of claim 7, wherein the color difference focusing lens (23) is an optical lens, a ball lens or a focusing lens that can have any focal length or any numerical aperture. The method of claim 7, wherein the photodetector (37) is a photoelectric conversion element. The method of claim 10, wherein the photodetector (37) is a photodetection amplification integration circuit.