ABSTRACT
This full-field transmission-type three-dimensional (3D) optical microscope is constructed based on the angle deviation method (ADM) and the algorithm of reflectivity-height transformation (RHT). The surface height is proportional to the deviation angle of light passing through the object. The angle deviation and surface height can be measured based on the reflectivity closed to the critical angle using a parallelogram prism and two CCDs.
ABSTRACT
We propose a method for small displacement measurement based on the angle deviation to phase change transformation. The phase change of common-path heterodyne interferometry due to the angle deviation of incidence of a light at interfaces caused by the displacement is detected by a lock-in amplifier. To obtain more accurate results we used an angular amplifier to increase the angle deviation and utilized a surface plasmon resonance (SPR) sensor to enhance the performance of phase detection. When a translator moves one of two face-to-face plane mirrors at an end and then rotates it a small angle, a light is incident onto the mirrors and reflected N times. The outgoing light is also deflected N times of the angle and incident into a SPR sensor. Thus the phase shift due to the angle deviation is amplified N times. The accumulated phase shift is proportional to the amplified angle deviation and displacement. Therefore, the phase change is obtained and the displacement is measured. The amount of movement required can be as low as 0.13 µm without an SPR sensor or 0.08 µm with an SPR sensor. The maximum measurement range can reach 1000 µm.
ABSTRACT
This study examines the use of reflectivity-height transformation in full-field angle-deviation microscopes (ADM). In such microscopes, two light intensity distribution images of a prism's total internal reflection and critical angle are obtained separately with two charge-coupled devices (CCDs), and are converted into a reflectivity profile point-to-point and then into angle of deviation matrix after the beam is reflected by the test sample; finally, the surface height of the sample is found through the triangular geometrical relationship. This method obtains the image through the effective imaging area of CCD. Once the two-dimensional (2D) image is obtained, the third dimension, height, is added to create a full-field 3D surface profile. Its conversion process is nonlinear; therefore, compensation must be made to reduce measurement errors. The optical magnification of high vertical resolution full-field 3D reflection-type ADM could reach >250 times, thus providing submicron measurements with nanometer vertical resolution and allowing for the simultaneous measurement of 2D and 3D images. Small defects on both transparent and nontransparent surfaces can be rapidly detected.
ABSTRACT
We propose a nonscanning three-dimensional (3D) optical microscope based on reflectivity-height transformation in applications of biological and transparent plate measurements. The reflectivity of a prism can be transformed to the surface height of the specimen based on geometrical optics and the principle of internal reflection. Thus, the pattern of reflectivity is representative of the surface profile. Using charge-coupled device cameras to obtain the two-dimensional image patterns and combining with its reflectivity pattern, the 3D profile can be generated. The lateral resolution is determined by the diffraction limit, and the vertical resolution is better than several nanometers according to the incident angle and polarization used.
Subject(s)
Imaging, Three-Dimensional , Microscopy , Depth Perception , Equipment Design , Imaging, Three-Dimensional/instrumentation , Imaging, Three-Dimensional/methods , Microscopy/instrumentation , Microscopy/methods , Optics and PhotonicsABSTRACT
We present a new microscopy technique that we call transmission angle deviation microscopy (TADM). It is based on common-path heterodyne interferometry and geometrical optics. An ultrahigh sensitivity surface plasmon resonance (SPR) angular sensor is used to expand dynamic measurement ranges and to improve the axial resolution in three-dimensional optical microscopy. When transmitted light is incident upon a specimen, the beam converges or diverges because of refractive and/or surface height variations. Advantages include high axial resolution (approximately 32 nm), nondestructive and noncontact measurement, and larger measurement ranges (+/- 80 microm) for a numerical aperture of 0.21 in a transparent measurement medium. The technique can be used without conductivity and pretreatment.
