JP2006308403A - Spectroscopy unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attempt to resolve a problem that conventional large-scale spectroscopes are highly efficient but system becomes large and expensive, a small-scale spectroscopes can operate easily at a comparatively low price but a linear array detector used as a detector is not adequate to detect a faint light and requires a certain light quantity, and a spectroscopes consisting of filters and PMTs requires a filter and the PMT for each fluorescence wavelength of the desired number and further, when fluorescence wavelengths are close to each other, the decomposition of wavelength is impossible by the use of the filter in some cases. <P>SOLUTION: The spectroscopy unit is so constituted that, while an edge 5 of the optical fiber 2 continuing into a photodetector 3 is made to face a chromatic aberration lens 1 so as to be arranged movably along the its optical axis 6, a movement control mechanism 7 capable of controlling the migration position is prepared and, a light shielding section is prepared at the central side of the core at the edge of optical fiber. For the optical fiber, it is desirable to adopt the multimode fiber with high NA. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a spectroscopic unit for adding a spectroscopic function to various apparatuses and systems.

  As a means for adding a spectroscopic function to various devices, systems, etc., there are firstly composed of a grating or a dispersion prism and a detector. Recently, a linear array detector such as a photodiode array or CCD is used as a detector. The number of small spectroscopes used has increased, and these spectrographs can easily obtain a spectroscopic spectrum at high speed.

  On the other hand, when detecting faint light such as fluorescence with high sensitivity, a configuration using a plurality of filters that allow only a target wavelength to pass and a PMT (photomultiplier tube) as a detector is also used.

Further, as means for easily adding a spectral function without using these configurations, Patent Document 1 discloses a pinhole arranged so that light from a sample is converged by a chromatic aberration lens and the converged light passes through. A configuration has been proposed in which the light is moved along the optical axis of the chromatic aberration lens in accordance with the wavelength, and the transmitted light from the pinhole is detected by a photodetector.
JP-A-1-188816

However, the above conventional techniques have the following problems.
1. A large spectroscope has high performance, for example, an automatic motor can be used to replace a filter that suppresses secondary light, but the apparatus is large and expensive.
2. Although a small spectroscope is relatively inexpensive and can be used easily, a linear array detector used as a detector is not suitable for detecting faint light and requires a light amount.
3. As a means for detecting faint light, a filter composed of a filter and a PMT requires a plurality of filters in accordance with a desired number of fluorescence wavelengths, and the PMT has the same number as the number of fluorescence to be detected. If the desired number of fluorescent wavelengths are close to each other, the filter may not be able to separate the wavelengths.
4. In Patent Document 1, it is necessary to use a lens having a small F value in order to effectively generate chromatic aberration. However, when the F value is small, a spherical aberration is also generated and the focal point converges. Since it is shifted on the optical axis, there is a disadvantage that light having different wavelengths also enters the detector.
In general, spherical aberration is an aberration that occurs in monochromatic light depending on the lens shape and does not collect light from one point on the axis. The farther from the center of the optical axis, that is, farther from the center of the lens, the peripheral side This is a phenomenon in which the focus shifts as the distance increases. This spherical aberration can be reduced by using a lens having a large F value, but in order to increase chromatic aberration, a lens having a large curvature radius is used, resulting in an increase in spherical aberration. It is difficult to solve these problems at the same time.

  An object of the present invention is to provide a spectroscopic unit that can use a spectroscopic function with high sensitivity and high wavelength resolution without using a conventional spectroscope. It is intended.

  In order to solve the above-described problems, in the present invention, the end of the optical fiber connected to the photodetector is placed facing the chromatic aberration lens so as to be movable along the optical axis, and the movement position can be controlled. Has proposed a spectroscopic unit that is equipped with a simple movement control mechanism and a light shielding part on the center side of the core at the end of the optical fiber.

  According to the present invention, in the above configuration, the movement control mechanism includes a storage unit that stores a correspondence relationship between the wavelength obtained based on the measurement using the light having a known wavelength and the position of the end of the optical fiber, and sets the desired wavelength. On the other hand, it has been proposed to obtain a position from the correspondence and move to that position.

  In the present invention described above, the optical fiber is preferably not a single mode fiber but a high NA multimode fiber.

  If the end of the optical fiber is positioned at a position where light of a certain wavelength passes through the peripheral side of the chromatic aberration lens and is focused, the wavelength is shorter than that, and the light passes through the center of the chromatic aberration lens and is focused on the vicinity of the end of the optical fiber. Can be shielded by a light shielding portion provided on the center side of the core at the end of the optical fiber, and the position at which the light having a certain wavelength passes through the center side of the chromatic aberration lens is focused on the end of the optical fiber. Since it is located farther from the chromatic aberration lens than the chromatic aberration lens, a part of the center side of the light with a certain wavelength is shielded by the light shielding part, but the other is within the core of the high NA optical fiber outside the light shielding part. Incident light can be detected by a photodetector.

  Thus, according to the present invention, it is possible to perform wavelength separation with high optical resolution by eliminating defocus due to spherical aberration of the chromatic aberration lens and enhancing the effect of chromatic aberration. Moreover, as a photodetector, it can apply also to the fluorescence sample etc. of a wavelength difference which cannot be spectrally separated by a filter by using high sensitivity photodetectors, such as PMT.

  The movement control mechanism is provided with a storage means for the correspondence between the wavelength obtained based on the measurement using the light having a known wavelength and the position of the end of the optical fiber, so that the position can be obtained from the correspondence for the desired wavelength. Can be quickly moved to that position.

  By moving to each position corresponding to a plurality of wavelengths one after another at a high speed, it is possible to measure light of a plurality of wavelengths.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a system diagram showing the configuration of a spectroscopic unit according to the present invention, and FIGS. 2 and 3 are explanatory diagrams schematically showing the operation and principle of the present invention.
Reference numeral 1 is a chromatic aberration lens, and 2 is an optical fiber. The optical fiber 2 is connected to the photodetector 3. As this photodetector 3, for example, a highly sensitive photodetector such as PMT is used. Reference numeral 4 denotes a moving mechanism. The moving mechanism 4 supports the end 5 of the optical fiber 2 so as to oppose the chromatic aberration lens 1 and supports the end 5 along the optical axis 6 of the chromatic aberration lens 1. It can be moved. Of course, as shown in the figure, the optical axis of the end portion 5 of the optical fiber 2 is made to coincide with the optical axis 6 of the chromatic aberration lens 1. The optical fiber 2 is not a single mode fiber but a high NA multimode fiber.

  Reference numeral 7 denotes a movement control mechanism for controlling the movement of the movement mechanism 4, and the movement control mechanism 7 includes a wavelength obtained based on measurement using light having a known wavelength and a position of the end portion 5 of the optical fiber 2. A storage means 8 for storing the correspondence relationship is provided, and the end of the optical fiber 2 is controlled by determining the position from the correspondence relationship stored in the storage means 8 for the desired wavelength to be measured and controlling the moving mechanism 4. The unit 5 is configured to move to the obtained position. When there are a plurality of wavelengths to be measured, each position is obtained and the moving mechanism 4 is controlled, and the end 5 of the optical fiber 2 is controlled to move to each position one after another at a high speed.

  As shown in FIG. 1 and FIG. 2, the light passing through the chromatic aberration lens 1 is focused at a position farther from the chromatic aberration lens 1 as the wavelength is longer due to chromatic aberration, and as shown in FIG. As described above, the focal point is set closer to the chromatic aberration lens 1 as it goes from the center side to the peripheral side of the chromatic aberration lens 1.

In FIG. 2, the difference in wavelength of light is represented by line types. For example, the solid line light L _{2 in} FIGS. 1 and 2 has a longer wavelength than the broken line light L ₃ , and is longer than the two-dot chain line light L _1. The wavelength is short. In the drawing, the light passing through the center side of the chromatic aberration lens 1 is distinguished by attaching the suffix i, and the light passing through the peripheral edge is appended by the suffix o.

As shown in FIGS. 2 and 3, the focal point f _3i formed by the light L _3i passing through the center side of the chromatic aberration lens 1 is transmitted through the peripheral side of the chromatic aberration lens 1 by the light L ₂ having a longer wavelength than the light L _3. It is close to the focal point f _2o .

Here, when measuring light of a certain wavelength, in this case, light L ₂ , as shown in FIG. 3, the movement control mechanism 7 controls the movement mechanism 4 so that the end face of the end portion 5 of the optical fiber 2 is moved. , The light L ₂ is brought to the position of the focal point f _2o that passes through the peripheral side of the chromatic aberration lens 1. Reference numeral 9 denotes a core of the optical fiber 2, 10 denotes a clad, and 11 denotes a light shielding portion.

In this state, the light L _{3i that} has passed through the center side of the chromatic aberration lens 1 with the light L ₃ having a shorter wavelength than the light L ₂ is shielded by the light shielding portion 11 provided on the center side of the core 9. Among the light L ₂ that has passed through the chromatic aberration lens 1, a part of the light L _2i that has passed through the center side of the chromatic aberration lens 1 is shielded by the light shielding unit 11, but the light that passes through the peripheral side of the chromatic aberration lens 1 is shielded. Since it is located outside the section 11, it can enter the core 9 of the optical fiber 2 and be detected by the photodetector 3.

  Here, if the light shielding unit 11 is increased, the ratio of light of the target wavelength that blocks the portion passing through the center side of the chromatic aberration lens 1 is increased as described above, so that the amount of light of the target wavelength is small. However, the wavelength resolution is increased. Therefore, the light shielding unit 11 can be appropriately determined in consideration of the wavelength resolution and the light quantity.

  Since the light shielding unit 11 prevents light from entering the core 9 of the optical fiber 2, the light shielding unit 11 may be configured to reflect, scatter, or absorb light. For example, by forming a scratch on the corresponding core 9, It can be easily scattered.

  In this way, according to the present invention, the defocus due to the spherical aberration of the chromatic aberration lens 1 is eliminated, and the effect of chromatic aberration is enhanced, so that wavelength separation with high optical resolution becomes possible. By using a high-sensitivity photodetector, the present invention can be applied to a fluorescent sample having a wavelength difference that cannot be separated by a filter having the configuration shown as the conventional example.

  As described above, in the present invention, the movement control mechanism 7 is provided with a storage unit that stores the correspondence between the wavelength obtained based on the measurement using the light having a known wavelength and the position of the end portion 5 of the optical fiber 2. The position of the light having the wavelength can be obtained from the correspondence relationship, and based on this, the moving mechanism 4 can quickly move to the position.

  And it can measure with respect to the light of a plurality of wavelengths by moving to each position corresponding to a plurality of wavelengths one after another at high speed.

Next, an embodiment using the present invention will be described in the case of simultaneously detecting ECFP and EYFP of fluorescent proteins often used for FRET (fluorescence energy transfer).
First, ECFP as a donor has a maximum excitation wavelength of 433 nm and a maximum fluorescence wavelength of 474 nm. On the other hand, the acceptor EYFP has a maximum excitation wavelength of 512 nm and a maximum fluorescence wavelength of 575 nm.
Therefore, considering the case where a laser diode (LD) having a wavelength of 405 nm is used for ECFP excitation and BK7 is used as the material of the chromatic aberration lens 1, the refractive indexes at the respective wavelengths are 1.53024 at 405 nm, 1.52329 at 5474 nm, and 587 nm. 1.51680.
On the other hand, when a lens with an effective diameter of 3.6 mm and a focal length of 6 mm is used as the chromatic aberration lens 1, the focal length f (405 nm) at each wavelength is 5.85 mm, f (474 nm) is 5.93 mm, and f (587 nm). Is 6.00mm.
Since the NA of the chromatic aberration lens 1 is 0.29 from the above-described dimensions, the NA of the optical fiber 2 is 0.29 or more. For example, the multimode type optical fiber 2 having a core 9 diameter of 200 μm is used.
At this time, the shift of the focal position in the direction of the optical axis 6 due to the spherical aberration of the chromatic aberration lens 1 is 159 μm, and the focal length of the light at the periphery of the chromatic aberration lens 1 is 5.69 mm at f (405 nm) and 5.77 at f (474 nm). mm and f (587 nm) are 5.84 mm.
As described above, the focal length of 5.84 mm corresponding to the peripheral portion of the chromatic aberration lens 1 and the focal length of 5.85 mm corresponding to the central portion of the chromatic aberration lens 1 having the excitation laser wavelength of 405 nm are substantially the same positions. The laser light is also detected at the same time.

Therefore, if 20% of the center side of the chromatic aberration lens 1 is shielded and the core 9 of the end 5 of the optical fiber 2 is aligned with the focal position of the light passing through the peripheral edge of the chromatic aberration lens 1, the effective chromatic aberration lens 1 at that time is effective. Since the magnitude of light passing through 20% on the center side of the diameter is about 61 μm at the largest 405 nm, the light shielding portion 11 shields the end face of the core 9 of the optical fiber 2 by φ61 μm. As described above, since light shielding is only required to scatter light as described above, the method is easily damaged.
The moving distance in the direction of the optical axis 6 of the end portion 5 of the optical fiber 2 necessary for detecting two fluorescences of EYFP and EYFP is 150 μm, and the optical fiber 2 is moved using a PZT stage as the moving mechanism 4. It was controlled by the control mechanism 7 to scan the moving distance at a high speed, and the PMT was used as the high-sensitivity photodetector 3 to perform simultaneous measurement, and it was possible to acquire an optical signal with little noise at each wavelength.

Since the present invention is as described above, the following effects are obtained and the industrial applicability is great.
1. A spectral function with high sensitivity and high wavelength resolution can be realized with a simple configuration without using a conventional spectroscope composed of a grating or dispersion prism and a detector, or a filter.
2. It can also be applied to a fluorescent sample having a small wavelength difference that cannot be separated by a filter.

It is a systematic diagram which shows the structure of the spectroscopy unit which concerns on this invention. It is explanatory drawing which shows typically the operation | movement of this invention, and its principle. It is explanatory drawing which shows typically the operation | movement of this invention, and its principle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chromatic aberration lens 2 Optical fiber 3 Optical detector 4 Movement mechanism 5 Optical fiber end part 6 Optical axis 7 Movement control mechanism 8 Storage means 9 Core 10 Clad 11 Light-shielding part

Claims (3)

The end of the optical fiber connected to the optical detector is opposed to the chromatic aberration lens and is installed so as to be movable along the optical axis, and a movement control mechanism capable of controlling the movement position is provided. Spectroscopic unit characterized in that a light-shielding part is provided at the center side of The movement control mechanism is provided with a memory means for storing the correspondence relationship between the wavelength obtained based on the measurement with the light having a known wavelength and the position of the end of the optical fiber, and obtaining the position from the correspondence relationship with respect to the desired wavelength. The spectroscopic unit according to claim 1, wherein the spectroscopic unit is moved to the position. 2. The spectroscopic unit according to claim 1, wherein the optical fiber is a high-NA multimode fiber.

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