TWI642939B - Optical system for detecting cantilever deformation and applications thereof - Google Patents

Abstract

This case relates to an optical cantilever deformation detection system and its application. The invention relates to a cantilever having a corresponding physical deformation and a corresponding deformation, wherein a laser beam projects a beam onto the cantilever, and the beam is reflected by the cantilever to generate a plurality of reflected lights of different optical path distances through an optical system, and then The processing unit calculates the shape of the cantilever according to the intensity of the plurality of reflected light projected onto the optical detector, so as to expand the detectable range of the cantilever-shaped variable, and the high sensitivity can be achieved. The invention also relates to the use of a photoacoustic spectroscopy apparatus and a scanning probe microscopy comprising the optical cantilever deformation detecting system described above.

Description

Optical cantilever deformation detection system and its application

The invention relates to an optical cantilever deformation detecting system which can expand the detectable range of the cantilever variable and can simultaneously take into consideration the high sensitivity. The invention further relates to a photoacoustic spectrum detector comprising the above optical cantilever deformation detecting system and an application of a scanning probe microscope.

Press, cantilever is a structure with one end fixed and one end without beam, which is used as a sensor from atomic force microscope. Cantilever sensors have been widely used in biomedical research and environmental testing in recent years, such as probe profilers and biochemical sensors (Bio) because of their characteristics of calibration-free and extremely sensitive. -chemical sensors) and other devices.

The cantilever can be divided into three types according to the sensing target and the principle, namely a resonant frequency sensor, a composite material sensor and a surface stress sensor. Among them, the resonant frequency cantilever sensor is mainly used to measure the surface quality change of the cantilever, which is very suitable for measuring the platform of small mass, such as protein or bacteria. The composite cantilever sensor technology is mainly used to measure temperature changes. In addition, when the environment around the cantilever changes or chemical or physical reactions occur directly on the surface of the cantilever, the mechanical properties of the cantilever surface are changed, called surface stress. When the reaction occurs only on a single side of the cantilever, the asymmetrical stress change will cause compressive or tensile stress, which in turn causes the cantilever to bend upward or downward. Surface stress type cantilever sensors are currently the most versatile technology.

Surface stress type cantilever can be mainly divided into optical cantilever and piezoresistive cantilever according to its detection technology. The optical cantilever uses the optical lever technology to concentrate the laser beam on the unbundled end of the cantilever, and uses the position sensor to record the reflected spot at the beam reflection end. When the cantilever is flexed and deformed, the laser spot projected on the position sensor will also be displaced. After the displacement is properly corrected and converted, the cantilever shape variable can be obtained by reverse. Although the cantilever sensor has high sensitivity characteristics, the detectable range of the cantilever variable is limited.

In view of the above, the present invention provides an optical cantilever deformation detecting system that expands the detectable range of the cantilever-shaped variable and can take into consideration high sensitivity as its main purpose.

According to a first aspect of the present invention, an optical cantilever deformation detecting system includes: at least one cantilever, which is a structure in which one end is fixed at the other end and is not bundled, and the corresponding deformation can be caused by external physical quantity change. a laser light source, wherein a light beam is projected onto the cantilever to generate a primary reflected light projected in one direction; an optical system is located in the direction, and the primary reflected light is formed into a plurality of different optical path distances Secondary reflected light; at least one optical detector receiving the plurality of reflected lights to output a corresponding one of the current signals; and a processing unit coupled to the optical detector to receive the current signal to calculate The cantilever is a one-shaped variable.

In a preferred embodiment, the optical system has at least one beam splitter and a mirror spaced along the direction.

In another preferred embodiment, the optical system has a crystal having at least one beam splitter and a plurality of reflective surfaces, the primary reflected light and the multiple reflected light entering and exiting the crystal via one of the beamsplitters. In a more preferred embodiment, the reflective surface can be a mirror.

In a preferred embodiment, the optical detector can be a two-quadrant or four-quadrant photodiode.

In a preferred embodiment, the number of optical detectors corresponds to the amount of the multiple reflected light.

In a preferred embodiment, the cantilever surface is provided with a reflective layer.

According to a second aspect of the present invention, there is provided a photoacoustic spectroscopy apparatus comprising: at least: a chamber for accommodating a test object; a light source providing a light beam to the chamber; and an optical cantilever deformation The detecting system detects the corresponding deformation caused by the change of the physical quantity in the chamber by the cantilever.

According to a third aspect of the present invention, there is provided a scanning probe microscopy comprising: a scanning platform having a surface for placing a test object to drive the object to be tested; and the optical cantilever deformation described above a detecting system, the cantilever is provided with a probe on a surface of the scanning platform, the processing unit can control a displacement state of the scanning platform; and a developing unit is connected to the processing unit.

Unless otherwise stated, the following terms used in the specification and claims of the present application have the definitions given below. It is to be understood that the singular <RTI ID=0.0>&quot;&quot;&quot;&quot;&quot; A single item. In addition, the open-ended conjunctions such as "including" and "having" used in the claims are intended to mean that the components or components described in the claims are not excluded. It should also be noted that the term "or" generally includes "and/or" in the sense, unless the content clearly indicates otherwise. The term "about" as used in the specification and claims of this application is intended to modify any error that may vary slightly, but such minor changes do not alter the nature.

Referring to FIG. 1 , the optical cantilever deformation detecting system 2 includes at least:

At least one of the cantilevers 21 is a structural body that is fixed at one end and has no bundle at the other end, and can be deformed correspondingly by external physical quantities.

A laser light source 22 provides a light beam L1 projected onto the cantilever 21 to generate a primary reflected light L2 projected in a direction T1; in a preferred embodiment, the cantilever 21 and the laser light source 22 can be further disposed There is a focusing lens (not shown), and a surface of the cantilever 21 can be provided with a reflective layer (not shown) to increase the reflection effect.

An optical system 23 is located in the direction T1, and the primary reflected light L2 can be formed into a plurality of multiple reflected lights having different optical path distances; in a preferred embodiment, the optical system has a spacing along the direction T1. At least one beam splitter and a mirror, the beam splitter splits an incident light into a transmitted light and a reflected light, the transmitted light traveling along the optical path of the incident light. In the embodiment shown in the figure, there are a first beam splitter 231, a second beam splitter 232 and a mirror 233, respectively, and the same optical path along the direction T1; wherein the primary reflected light L2 passes through the first beam splitter 231 The light beam is divided into a first multiple reflected light L3 and a first transmitted light L4, and the first multiple reflected light L3 is projected on the optical detector 24, and the optical path distance of the first multiple reflected light L3 is the shortest The first transmitted light L4 is split into a second multiple reflected light L5 and a second transmitted light L6 through the second beam splitter 232, and the second multiple reflected light L5 is projected onto the optical detector. 24, and the optical path distance of the second multiple reflected light L5 is centered; and the second transmitted light L6 is formed by the mirror 233 to form a third multiple reflected light L7 projected on the optical detector 24, and the third The multiple-reflected light L7 has the longest optical path distance. Although the specification and the illustrated optical system have two beamsplitters and one mirror, three multiple reflected lights can be formed, but the number of beamsplitters can be changed according to the number of multiple reflected lights required. To form N-channel multiple reflected light, the optical system needs to have (N-1) beamsplitters.

The at least one optical detector 24 receives the first multiple reflected light L3, the second multiple reflected light L5, and the third multiple reflected light L7 to output a corresponding one of the current signals. The optical detector 24 can be a two-quadrant or four-quadrant photodiode for sensing the intensity of incident light. The corresponding current signal is output according to the intensity of the incident light detected by each photodiode. Although the description and drawings show that the number of optical detectors 24 is one and can receive a plurality of reflected lights, the number of optical detectors 24 can also correspond to the number of the multiple reflected lights, for example, for example. After being processed by the optical system 23, the system has three multiple reflected lights, and can be respectively projected to three optical detectors 24 for signal output.

A processing unit 25 is coupled to the optical detector 24 to receive the current signal to calculate a shape variable of the cantilever.

The processing unit 25 calculates the shape variable of the cantilever according to the intensity of the first multiple reflected light L3, the second multiple reflected light L5, and the third multiple reflected light L7 projected onto the optical detector 24. The third multi-reflected light L7 having the longest optical path distance can only detect a relatively small range of cantilever-shaped variables, but has high sensitivity to the cantilever micro-miniature variable, and the second-order reflection with the optical path distance being centered. The light L5 and the first plurality of reflected light L3 having the shortest optical path distance can respectively detect relatively large cantilever-shaped variables, so as to expand the detectable range of the cantilever-shaped variable, and the characteristics of high sensitivity can be taken into consideration.

In another preferred embodiment, to reduce the length and volume of the optical system described above, the optical system has a crystal 234 having at least one beam splitter and a plurality of reflective surfaces as shown in FIG. In the illustrated embodiment, the first beam splitter 231 is provided and the interior of the crystal 234 is covered with a reflective surface 235. Although the specification illustrates and illustrates that the crystal 234 has four faces, the crystal 234 can have any shape known to those of ordinary skill in the art, and the reflective face can be a mirror. The primary reflected light L2 is split into a first multiple reflected light L3 and a first transmitted light L4 via the first beam splitter 231, and the multiple reflected light L3 is projected onto the optical detector 24. And the optical path distance of the first multiple reflected light L3 is short; and the first transmitted light L4 enters the crystal 234 and is reflected by the complex reflecting surface 235, and finally forms a second multiple reflection through the first beam splitter 231. The light L5 is projected on the optical detector 24, and the optical path distance of the second multiple reflected light L5 is long.

The invention utilizes an optical system composed of a beam splitter and a mirror, and can form a plurality of reflected light of a plurality of different optical path distances by the reflected light of the cantilever, and expand the cantilever by using the multiple reflected light to project the intensity of the optical detector. The detectable range of the shape variable can be combined with high sensitivity. The optical cantilever deformation detection system of the invention can be widely used in the fields of semiconductor industry, precision machinery, micro-electromechanical system and nanotechnology, for example, for photoacoustic spectroscopy 3, as shown in FIG. 3, which at least includes a chamber 31 for accommodating the object to be tested; a light source 32 for supplying a light beam to the chamber 31; and an optical cantilever deformation detecting system 2 for detecting the physical quantity in the chamber 31 by the cantilever 21 The corresponding deformation caused by the change. The photoacoustic spectroscopy is mainly used for gas detection, and the light source 32 is irradiated onto the gas sample sealed in the chamber 31. The gas sample absorbs the light energy and converts it into the kinetic energy of the gas molecules, thereby generating pressure fluctuations, and the pressure fluctuations allow the cantilever 21 corresponding deformation, the processing unit detects the deformation variable, and can determine the type and concentration of the gas sample.

In another preferred embodiment, it is used in a scanning probe microscope 4, which is shown in FIG. 4, and includes at least a scanning platform 41 on the surface of which a sample to be tested 42 is placed to drive the object to be tested. The displacement of the measuring object 42; the above-mentioned optical cantilever deformation detecting system 2, the cantilever 21 is provided with a probe 43 on the surface of the scanning platform 41, the processing unit 25 can control the displacement state of the scanning platform 41; The image unit 44 is connected to the processing unit 25. When the tip end of the probe 43 is in contact with the surface of the object to be tested 42, since the elastic modulus of the cantilever 21 is equivalent to the force between the atoms, the force of the atom at the tip of the probe 43 and the atom on the surface of the object to be tested 42 causes the cantilever 21 to be vertical. The force direction moves, and the source of the force includes the Coulomb repulsive force between the probe 43 and the Van der Waals force of the surface and the outer electrons of the probe 43 and the surface. Therefore, the surface of the object to be tested 42 is undulating, and the cantilever 21 is deformed up and down. The scanning platform 41 (which may be a piezoelectric material scanner with three-axis displacement capability) enables the object to be tested 42 to scan back and forth in a selected area, the processing unit 25 detects the cantilever 21 shape variable, and the processing unit 25 controls the scanning. The platform 41 is combined with the fine adjustment function on the height axis, and the distance between the probe 43 and the object to be tested 42 is adjusted to maintain the fixed atoms during the scanning process. Therefore, when scanning an area, the vertical fine-tuning distance is performed by a two-dimensional internal function. It is stored and an atomic force image of the so-called scanning area is formed by the developing unit 44, which generally corresponds to an image of the surface of the scanning area, which is also called a height image.

The above embodiments are intended to be illustrative of the present invention, and are not intended to limit the scope of the invention, and various modifications and changes may be made without departing from the scope of the invention.

L1‧‧‧ Beam

L2‧‧‧A reflected light

L3‧‧‧First multiple reflected light

L4‧‧‧first transmitted light

L5‧‧‧Second multiple reflected light

L6‧‧‧second transmitted light

L7‧‧‧ third reflected light

T1‧‧ direction

2‧‧‧Optical cantilever deformation detection system

21‧‧‧ cantilever

22‧‧‧Laser light source

23‧‧‧Optical system

231‧‧‧First Beamsplitter

232‧‧‧Second beam splitter

233‧‧‧Mirror

234‧‧‧ crystal

235‧‧‧reflecting surface

24‧‧‧ Optical detector

25‧‧‧Processing unit

3‧‧‧Photoacoustic spectroscopy

31‧‧‧ chamber

32‧‧‧Light source

4‧‧‧Scanning Probe Microscope

41‧‧‧Scanning platform

42‧‧‧Test object

43‧‧‧Probe

44‧‧‧Developing unit

1 is a schematic view of a first embodiment of a detection system according to the present invention; FIG. 2 is a schematic view showing a second embodiment of the detection system of the present invention; and FIG. 3 is a detection system of the present invention. A schematic diagram of a photoacoustic spectroscopy detector; and FIG. 4 is a schematic diagram of a detection system applied to a scanning probe microscopy apparatus according to the present invention.

Claims (9)

An optical cantilever deformation detecting system comprising: at least one cantilever, which is a structural body fixed at one end and not bundled at the other end, which can be deformed by external physical quantity; a laser light source is provided a light beam is projected on the cantilever to generate a primary reflected light projected in one direction; an optical system is located in the direction, and the primary reflected light is formed into a plurality of multiple reflected lights having different optical path distances; at least one optical detection The detector receives the plurality of reflected lights to output a corresponding one of the current signals; and a processing unit is coupled to the optical detector to receive the current signal to calculate a shape variable of the cantilever. The optical cantilever deformation detecting system of claim 1, wherein the optical system has at least one beam splitter and a mirror arranged at intervals in the direction. The optical cantilever deformation detecting system of claim 1, wherein the optical system has a crystal having at least one beam splitter and a plurality of reflecting surfaces, and the one-time reflected light and the multi-reflected light are split by one of the light The mirror enters and exits the crystal. The optical cantilever deformation detecting system of claim 3, wherein the reflecting surface is a mirror. The optical cantilever deformation detecting system according to any one of claims 1 to 4, wherein the optical detector is a two-quadrant or four-quadrant photodiode. The optical cantilever deformation detecting system according to any one of claims 1 to 4, wherein the number of the optical detectors corresponds to the number of the multiple reflected lights. The optical cantilever deformation detecting system according to any one of claims 1 to 4, wherein the cantilever surface is provided with a reflective layer. A photoacoustic spectroscopy apparatus comprising: at least one chamber for accommodating a sample to be tested; a light source for providing a light beam to the chamber; and an optical cantilever deformation according to any one of claims 1 to 7. The detecting system detects the corresponding deformation caused by the change of the physical quantity in the chamber by the cantilever. A scanning probe microscopy comprising at least: a scanning platform having a surface for placing a test object to drive the object to be tested; and the optical cantilever deformation according to any one of claims 1 to 7. a detecting system, the cantilever is provided with a probe on a surface of the scanning platform, the processing unit can control a displacement state of the scanning platform; and a developing unit is connected to the processing unit.