We proposed a three-dimensional (3-D) microscope with a magnification of 50X based on the principle of angle
deviation microscopy for measuring the transparent materials. We utilized a parallel beam like uncountable probes to
sense a specimen. After sensing, each light may be deflected a small angle due to the non-smooth surface or/and the
change of refractive index. A parallelogram prism is used to acquiring all the deflective angles by measuring the
reflectivity of prism based on the critical angle method. Thus, the surface height is proportional to the deflective angle
and the reflectivity. Using two CCDs is to record the intensity patterns on conditions of TIR and the critical angle,
respectively. The CCDs are located at the image planes, one is in the TIR path, and the other is in the critical angle path,
respectively. Thus, the reflectivity pattern can be calculated and transformed into the 3-D surface profile. In our
experiment, the lateral and vertical resolutions can be demonstrated within submicron and 1 nm, respectively.
This paper presents a study of the lateral and axial resolutions of a transmission laser-scanning angle-deviation microscope (TADM) with different numerical aperture (NA) values. The TADM is based on geometric optics and surface plasmon resonance principles. The surface height is proportional to the phase difference between two marginal rays of the test beam, which is passed through the test medium. We used common-path heterodyne interferometry to measure the phase difference in real time, and used a personal computer to calculate and plot the surface profile. The experimental results showed that the best lateral and axial resolutions for NA = 0.41 were 0.5 μm and 3 nm, respectively, and the lateral resolution breaks through the diffraction limits.
Transmission-type laser scanning angle deviation microscopy (TADM) with NA=0.65 for three dimension (3D)
measurement is presented. It is based on the theorems of geometrical angular deviation and surface plasmon resonance
(SPR) and the use of the common-path heterodyne interferometry. When a laser beam defocuses on the surface of a
transparent sample, the transmission light will be deviated a small angle from the optical axis and the deviation angle is
proportional to the defocus length and the square of the numerical aperture. We used a SPR angular sensor and the
common-path heterodyne interferometry to measure this deviation angle. Scanning the sample, the phase profile was
measured and transferred to surface height pattern, the 3D surface profile was obtained in real-time. The results showed
that the dynamic range and lateral and axial resolutions were equal to ±5.6 μm, 0.3 μm, and 3 nm, respectively.
An application of surface plasmon resonance (SPR) angular sensor in the surface defect measurement is
proposed. The method based on geometrical optics, SPR effects and heterodyne interferometry technique could
transform a phase shift into a surface height. As a beam normally is incident into a plate that is with a very small
apex angle, the angle is a function of the flatness or defect directly. Thus, to scan the specimen, the surface defect or
its flatness is detected. It has some merits, such as, simple, sensitive, and real-time measurements.
An application of D-type optical fiber sensor (OFS) in the temperature measurement is proposed. The sensor
based on attenuated total reflection (ATR) effect could be like as a probe to sense a liquid or gas temperature in
real-time. We use the optical spectrum method combining with the minimum value of relative power ratio technique
to analyze and record the temperature. The temperature resolution is in the region of 0.01°C for the measuring range
of 24~75°C. It has some merits, such as, simple, sensitive, and remote test.
For improving the sensitivity of a D-type SPR fiber sensor, we simulated the optimum parameters, such as, the thickness of coatings, the length of sensor, and the angle of incidence for different ranges of refractive index. These simulations are based on SPR theory and the intensity and phase methods. It is clearly that, the sensitivity is improved by increasing the length of sensor and/or the thickness of the gold film. And the sensitivity of the phase method is higher than the intensity method by two orders. It is used to detect the
refractive index or concentration of gas or liquid in real-time, and it has some merits, such as, small, simple, cheaper, and in vivo test.
A new method for small displacement measurement based on surface plasmon resonance and heterodyne interferometry is presented. A heterodyne light is focused on a mirror and reflected from it, and then it is incident on a prism which was coated with a thin gold film. When the mirror or the objective lens has a small displacement, the light will be converging or diverging into the prism, and the phase variation between two parts of the test beam under the condition of surface plasmon resonance (SPR) can be measured by using a two-segment photodiode and a lock-in amplifier. This phase difference between two parts of the test beam is proportional to the departure of the mirror from the focal plane, so the displacement can be obtained in real-time. It has some merits, such as, simple, stable, very high sensitivity and resolution. And its resolution is better than 1nm.
For improving the sensitivity of a SPR biosensor, we proposed a new combination of the thin silver (Ag) and SiO2 films, and used the common-path heterodyne interferometry. Although the Ag film has higher sensitivity than the gold (Au) film1, but Ag has toxicity for many media and it is easy to be oxidized. In order to enhance the sensitivity and protect the tested medium not to directly contact with Ag, we selected a coating of SiO2 on the Ag film for the reason of it is cheaper and easy to obtain. The simulations and experimental results are shown that its best resolution could reach to the value of 6.9×10-9RIU.
A new idea for a D-type optical fiber sensor based on Kretschmann's configuration is proposed. The sensing device is a D-type single mode fiber with a half-polished core, and a thin film layer of gold deposited on the flat side of the sensor. In order to achieve the best sensitivity of the D-type optical fiber sensor, we must choose suitable parameters, e.g., the thickness of the thin film layer of gold and the length of the sensor. We found that the experimental results are in good correspondence with theoretical results. The sensor's sensitivity can reach 2×10–4 refractive index unit (RIU) at least. Because the sensor has some merits, e.g., small size, less costly, smaller sample volume, easy measurement, and suitability for in vivo testing, etc., the D-type optical fiber sensor is valuable for chemical, biological, and biochemical sensing.
A heterodyne dispersion meter based on total-internal reflection effects and common-path configuration is presented. It is used to measuring the dispersion power of an optical material or component for many applications in industries. The phase difference between S and P-polarizations at the total-internal reflection condition can be extracted and measured accurately by using heterodyne interferometry. The constants of dispersion formulas built by traditional ways could be revised by this method. It has some merits, such as, high resolution and stability, easy to operate, and real-time measurement.
A new method for measuring a very small displacement is presented. The principles of the measurement are based on the critical angle method and confocal technology. It will increase the lateral and longitudinal resolutions higher than 0.3μm and 5nm, respectively, and the maximum displacement could be above 12μm. This optical structure could be applied to measure some messages for optical surface, bio-medical science, and nanotechnology in the future. The new technique has some merits, such as a simple and compact optical setup, high sensitivity, and high resolution.
A new type of fiber optical liquid refractometer based on total-internal reflection heterodyne interferometry (TIRHI) is proposed. The phase shift difference due to the TIR effects between the P and S-polarizations is measured using heterodyne interferometry with a D-type fiber sensor. Substituting the phase shift difference into Fresnel's equations, the refractive index can be calculated. It has some merits, such as, high sensitivity and stability, small size and real-time measurement.