Optics: measuring and testing – Refraction testing
Reexamination Certificate
2002-04-16
2004-11-02
Toatley, Jr., Gregory J. (Department: 2877)
Optics: measuring and testing
Refraction testing
C356S134000, C356S135000
Reexamination Certificate
active
06813014
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to technology about magnetic fluids. More particularly, the present invention relates to the method of designing a magnetic fluid with a desired value of refractive index. Moreover, the refractive index of the magnetic fluid can be tuned around the designed value as needed.
2. Description of Related Art
Ferrofluids are a type of magnetic fluid that typically consisting of colloidal magnetic particles such as magnetite or manganese-zinc ferrites, disposed with the aid of surfactant in a continuous carrier phase. The average diameter of the disposed magnetic particles conventionally ranges about between 5-10 nm. Each particle has a constant magnetic dipole moment proportional to its size that can align with an external magnetic field.
Ferrofluids experience body forces in homogeneous magnetic fields, that allows their position to be manipulated and thus enable the construction of devices, such as rotary seals, bearings, and related mechanical devices. Ferrofluids can also be used in display device that uses a magnetic field to capture an opaque magnetic fluid in a pre-determined optical pattern. As the technology is continuously developed, it can be expected to have more various applications with ferrofluids in the future.
Usually, the magnetic fluid includes the magnetic particles in a fluid base. For example, the magnetic fluids include water/kerosene/heptan-based Fe
3
O
4
/MnFe
2
O
4
/CoFe
2
O
4
. Since the nature of matter, the magnetic fluid naturally has a refractive index. The refractive index is related to the properties of the magnetic fluid. If the refractive index of the magnetic fluid can be designed and tuned according to the design requirement, magnetic fluid would be more powerful for its application. However, how to design and tune the refractive index of the magnetic fluid is still not being well investigated.
SUMMARY OF THE INVENTION
The invention provides a method for forming a magnetic fluid, of which the refractive index is designed to at a desired quantity without magnetic field presented.
The invention provides a system for forming a magnetic fluid, of which the refractive index is designed to at a desired quantity without magnetic field presented.
The invention provides a method for forming a magnetic fluid, of which the refractive index is tunable to a desired quantity.
The invention provides a system for forming a magnetic fluid, of which the refractive index is tunable to a desired quantity.
The invention provides a measuring system for measuring the refractive index of the magnetic fluid base on a critical angle at which a total reflection occurs with respect to an incident light.
As embodied and broadly described herein, the invention provides a method for designing and tuning a refractive index of a magnetic fluid that is performed by adjusting some characteristic parameters. The characteristic parameters include the type of carrier, the type of magnetic particles, the concentration of the magnetic ingredient; the wavelength of an intended light onto the magnetic fluid layer; the strength of applied magnetic field; the sweep rate of the magnetic field; the direction of the applied magnetic field; the strength of applied magnetic field associated with the thickness of the magnetic fluid layer; and the strength of applied magnetic field associated with the temperature. A magnetic fluid with a designed value of refractive index under zero magnetic field is synthesized by carefully selecting the carrier, the type of magnetic particles and the volume concentration of the magnetic particles, and this value can further be tuning around the designed value by changing the forgoing characteristic parameters.
The invention also provides another method for measuring a refractive index of a magnetic fluid layer under an environment with a condition, wherein the magnetic fluid layer has a magnetic ingredient and is injected in a cell of a substrate. The method comprises putting a prism on the magnetic fluid layer, wherein a side surface against a right angle of the prism contacts with the magnetic fluid layer. The prism has a prism refractive index n
p
. An incident light is incident onto the magnetic fluid layer through the prism with in an incident angle &thgr;
i
with respect to a normal direction. An intensity of the reflected light is measured, so as to determine whether or not a critical angle for total reflection by the magnetic fluid layer is achieved under the incident angle &thgr;
i
=&thgr;
it
, where &thgr;
it
is the value of incident angle &thgr;
t
at which the total refraction occurs at the interface between the prism and magnetic fluid layer. The refractive index of the magnetic fluid layer is determined according to a formula of
n
MF
=
1
2
(
2
n
p
2
-
2
sin
2
θ
it
-
2
sin
θ
i
t
)
,
where n
MF
is a quantity of the refractive index of the magnetic fluid layer.
The invention also provides a system to measure a refractive index of a magnetic fluid layer, wherein the refractive index is tunable. The system comprises a substrate to hold the magnetic fluid layer, wherein the magnetic fluid layer has a magnetic ingredient in a fluid base. A measuring subsystem to measure the refractive index of the magnetic fluid layer, wherein the measuring system allows the refractive index to be tuned under at least one of a plurality of measuring conditions. The conditions comprise the type of carrier, the type of magnetic particles, the concentration of the magnetic ingredient; the wavelength of an intended light onto the magnetic fluid layer; the strength of applied magnetic field; the sweep rate of the magnetic field; the direction of the applied magnetic field; the strength of applied magnetic field associated with the thickness of the magnetic fluid layer; and the strength of applied magnetic field associated with the temperature.
In the foregoing measuring subsystem, it measures the refractive index of the magnetic fluid layer according to a critical angle for total reflection with respect to an incident light.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 6086780 (2000-07-01), Hong et al.
Hong Chin-Yih Rex
Horng Herng-Er
Tse Wan-Sun
Yang Hong-Chang
Yang Shieh-Yueh
J. C. Patents
Merlino Amanda
Toatley , Jr. Gregory J.
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