What is claimed is:
1. A particle size distribution monitor, comprising:
a transducer adapted to be a source of ultrasonic energy and positioned in contact with a suspension containing a percent by volume of particles in a liquid, the transducer transmitting ultrasonic energy through the suspension wherein the energy comprises a wideband pulse containing a range of frequency components;
a transducer adapted to be a receiver of ultrasonic energy and positioned in contact with said suspension to receive said wideband range of ultrasonic energy which has passed through the suspension;
a first means adapted to accept a signal from said receiver and make an instantaneous determination of the attenuation of the wideband ultrasonic energy in passing through the suspension.
2. The monitor of claim 1, further comprising a second means adapted to develop an output representative of the total particle size distribution of the suspension.
3. The monitor of claim 1, wherein the first means includes a logarithmic preamplifier for said signal.
4. The monitor of claim 1, wherein
the first means comprises an AD digitizer for said signal, an FFT analyzer for the digitized signal, and means to obtain the magnitude of the FFT data representing the measured attenuation; and
the second means comprises means to determine an estimated PSD and means to compare the estimated PSD with the measured attenuation and determine the goodness of the fit.
5. The monitor of claim 4, wherein the first means further comprises a logarithmic preamplifier that compresses said signal from the receiver before it is processed by the AD digitizer.
6. The monitor of claim 4, wherein the first means further comprises a means of controlling an additional attenuation of said signal from the receiver before it is processed by the AD digitizer.
7. The monitor of claim 1, wherein the source of ultrasonic energy has a center frequency in the range of from 100 kHz to 5 MHz for determining the attenuation in a suspension comprising particles which make up 10% or more by volume of the suspension.
8. The monitor of claim 1, wherein the source of ultrasonic energy has a center frequency in the range of from 5 MHz to 50 MHz for determining the attenuation in a suspension comprising particles which make up 15% or less by volume of the suspension.
9. The monitor of claim 1, wherein the transducer to transmit the beam of energy and the transducer to receive the beam of energy are the same transducer and further comprising a reflector positioned in the suspension opposite the transducer and wherein the transducer is adapted to receive multiple echoes of energy from the reflector and determine a corrected attenuation value from the information in the multiple echoes.
10. The monitor of claim 1, wherein the first means adapted to make an instantaneous determination of the attenuation of the ultrasonic energy in passing through the suspension is a computer that is remotely positioned from the transducers and is connected to the transducers by a fiber optic cable.
11. A method of monitoring the particle size distribution of particles in a suspension under dynamic conditions, comprising the steps of:
transmitting a first pulse of ultrasonic energy containing a wideband range of frequency components through the suspension which attenuates the pulse;
receiving the attenuated pulse after it has passed through the suspension;
developing a first signal representative of the attenuated first pulse;
digitizing the first signal with a high speed analog-to-digital converter to form a time domain signal;
applying a Fourier transform to convert the time domain signal to an equivalent frequency domain signal, or spectrum, for each signal;
converting the spectrum into dB to express the attenuation as a function of frequency.
12. The method of claim 11, further comprising developing the attenuation to determine the total particle size distribution of the suspension and presenting said determination as an output.
13. The method of claim 11, wherein the step of transmitting a first pulse of ultrasonic energy containing a wideband range of frequency components through the suspension, comprises transmitting the energy through a suspension comprising sub-micron particles.
14. The method of claim 11, further comprising:
reflecting the first pulse with a reflector;
detecting a first echo of the first pulse that has traveled over a first path length and determining the spectrum of the first echo;
detecting a second echo of the first pulse that has traveled over a second path length and determining the spectrum of the second echo;
determining the difference between the first echo spectrum and second echo spectrum and dividing the difference by the difference between the first path length and second path length to obtain an attenuation corrected for system variations.
15. The method of claim 11, wherein the step of transmitting a first pulse of ultrasonic energy containing a wideband range of frequency components through the suspension comprises transmitting through a suspension containing 10% or more of particles by volume and the wide bandwidth of the first pulse has a center frequency of 5 MHz or less.
16. The method of claim 11, wherein the step of transmitting a first pulse of ultrasonic energy containing a wideband range of frequency components through the suspension comprises transmitting through a suspension containing 10% or less of particles by volume and the wide bandwidth of the first pulse has a center frequency of 5 MHz or more.
17. The method of claim 11, wherein the transmitting and receiving occur along an acoustic path that has a length greater than 0.25 inches (0.64 cm).
18. A method of utilizing particle size monitoring to control a process for precipitating particles, comprising:
repeatedly applying the method of claim 11 to collect data continuously about the attenuation of an ultrasonic pulse passed through a master batch of a solution which has a particle size that is changing;
generating a signal when the particle size reaches a predetermined attenuation value;
withdrawing a sub-batch of solution after the signal is generated;
predetermining a concentration of a second solution to be added to the withdrawn sub-batch based on the measured attenuation signal at the time of withdrawal;
adding said predetermined concentration of second solution to the sub-batch to precipitate particles.
19. The method of claim 18, wherein the master batch is a metal salt solution and the particles precipitated are metal particles.
20. The method of claim 19, wherein the metal salt solution is a silver salt solution and the particles precipitated are silver particles.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An optical device comprising:
a polarizer having a polarizing layer that consists of triacetylcellulose-free and uniaxially extended polyvinyl alcohol, the polarizing layer absorbing polarized light in a direction parallel to the uniaxially extending direction and transmitting polarized light in a direction perpendicular to the uniaxially extending direction;
a first light-transmissive substrate bonded on one surface of the polarizing layer of the polarizer by a first bonding material; and
a second light-transmissive substrate bonded on the other surface of the polarizing layer of the polarizer by a second bonding material;
the first light-transmissive substrate and the second light-transmissive substrate being made of an inorganic material, and
the optical device not including an organic material except the polarizing layer, the first bonding material and the second bonding material.
2. The optical device according to claim 1,
at least one of the first light-transmissive substrate and the second light-transmissive substrate being made of sapphire or quartz.
3. The optical device according to claim 1,
at least one of the first light-transmissive substrate and the second light-transmissive substrate being made of quartz glass, hard glass or other light-transmissive glasses.
4. The optical device according to claim 1,
at least one of the first light-transmissive substrate and the second light-transmissive substrate being made of crystalline glass or sintered body of cubic crystal.
5. The optical device according to claim 1,
at least one of the first light-transmissive substrate and the second light-transmissive substrate being made of a material having an optic axis, and
the first light-transmissive substrate and the second light-transmissive substrate being arranged with respect to the polarizing layer so that the optic axis of the light-transmissive substrate made of the material having the optic axis is substantially parallel or substantially perpendicular to the polarization axis of the polarizing layer.
6. The optical device according to claim 1,
the first light-transmissive substrate and the second light-transmissive substrate being made of the same material.
7. A method for manufacturing an optical device including a polarizer having a polarizing layer and a first light-transmissive substrate and a second light-transmissive substrate that are made of an inorganic material having an optic axis, the method comprising:
applying a pressure-sensitive-adhesive to one surface of the polarizing layer of the polarizer, the polarizing layer consisting of triacetylcellulose-free and uniaxially extended polyvinyl alcohol, the polarizing layer absorbing polarized light in a direction parallel to the uniaxially extending direction and transmitting polarized light in a direction perpendicular to the uniaxially extending direction;
bonding the one surface of the polarizing layer and the first light-transmissive substrate with the pressure-sensitive-adhesive;
applying an adhesive to the other surface of the polarizing layer of the polarizer; and
bonding the other surface of the polarizing layer and the second light-transmissive substrate with the adhesive, in this order,
the optical device not including an organic material except the polarizing layer, the pressure-sensitive-adhesive and the adhesive.
8. The method for manufacturing an optical device according to claim 7,
between the bonding the polarizing layer and the first light-transmissive substrate and the application of the adhesive, performing heat treatment for the polarizing layer bonded on the first light-transmissive substrate with the pressure-sensitive-adhesive.
9. The method for manufacturing an optical device according to claim 7,
in the bonding the polarizing layer and the first light-transmissive substrate, the polarizing layer and the first light-transmissive substrate are bonded so that the optic axis of the first light-transmissive substrate and the polarization axis of the polarizing layer become substantially parallel or substantially perpendicular to each other, and
in the bonding the polarizing layer and the second light-transmissive substrate, the polarizing layer and the second light-transmissive substrate are bonded so that the optic axis of the second light-transmissive substrate and the polarization axis of the polarizing layer become substantially parallel or substantially perpendicular to each other.
10. The method for manufacturing an optical device according to claim 7,
an ultraviolet hardening adhesive being used as the adhesive, and
in the bonding the polarizing layer and the second light-transmissive substrate, casting ultraviolet rays to the adhesive to harden the adhesive.
11. The optical device according to claim 1,
the materials of the first and second light-transmissive substrates having a smaller coefficient of thermal expansion than that of the polarizer.
12. The optical device according to claim 1,
at least one of the first and second light-transmissive substrates being made of a material having no optic axis.
13. The method for manufacturing an optical device according to claim 7,
the materials of the first and second light-transmissive substrates having a smaller coefficient of thermal expansion than that of the polarizer.
14. The method for manufacturing an optical device according to claim 7,
at least one of the first and second light-transmissive substrates being made of a material having no optic axis.