1. An ultrasound diagnostic apparatus comprising:
an ultrasound probe that performs ultrasound transmissionreception in Doppler mode and ultrasound transmissionreception in other mode than Doppler mode; and
a Doppler processing unit that performs quadrature detection on an echo signal generated from the ultrasound transmissionreception for Doppler mode and then generates a Doppler spectrum signal,
wherein the Doppler processing unit includes a signal estimation unit that performs an extrapolation process to estimate missing part of the Doppler spectrum signal resulting from the ultrasound transmissionreception for other mode.
2. The ultrasound diagnostic apparatus according to claim 1,
wherein the signal estimation unit performs an extrapolation process based on a temporal change of a frequency for the Doppler spectrum signal.
3. The ultrasound diagnostic apparatus according to claim 2,
wherein a temporal change of a frequency for the Doppler spectrum signal is equivalent to a temporal change of an average frequency for a frequency spectrum for the Doppler spectrum signal.
4. The ultrasound diagnostic apparatus according to claim 2,
wherein a temporal change of a frequency for the Doppler spectrum signal is equivalent to a temporal change of a frequency having peak power in a frequency spectrum for the Doppler spectrum signal.
5. The ultrasound diagnostic apparatus according to claim 2,
wherein a temporal change of a frequency for the Doppler spectrum signal is equivalent to a temporal change of a maximum frequency in a frequency spectrum for the Doppler spectrum signal.
6. The ultrasound diagnostic apparatus according to claim 1,
wherein the signal estimation unit settles a data interval according to a subject region, the data interval being configured to find an extrapolation function used for an extrapolation process.
7. The ultrasound diagnostic apparatus according to claim 2,
wherein the signal estimation unit settles a data interval according to a subject region, the data interval being configured to find an extrapolation function used for an extrapolation process.
8. The ultrasound diagnostic apparatus according to claim 3,
wherein the signal estimation unit settles a data interval according to a subject region, the data interval being configured to find an extrapolation function used for an extrapolation process.
9. The ultrasound diagnostic apparatus according to claim 4,
wherein the signal estimation unit settles a data interval according to a subject region, the data interval being configured to find an extrapolation function used for an extrapolation process.
10. The ultrasound diagnostic apparatus according to claim 5,
wherein the signal estimation unit settles a data interval according to a subject region, the data interval being configured to find an extrapolation function used for an extrapolation process.
11. The ultrasound diagnostic apparatus according to claim 1,
wherein the Doppler processing unit uses a Fourier transform process to generate the Doppler spectrum signal.
12. The ultrasound diagnostic apparatus according to claim 2,
wherein the Doppler processing unit uses a Fourier transform process to generate the Doppler spectrum signal.
13. The ultrasound diagnostic apparatus according to claim 3,
wherein the Doppler processing unit uses a Fourier transform process to generate the Doppler spectrum signal.
14. The ultrasound diagnostic apparatus according to claim 4,
wherein the Doppler processing unit uses a Fourier transform process to generate the Doppler spectrum signal.
15. The ultrasound diagnostic apparatus according to claim 5,
wherein the Doppler processing unit uses a Fourier transform process to generate the Doppler spectrum signal.
16. The ultrasound diagnostic apparatus according to claim 6,
wherein the Doppler processing unit uses a Fourier transform process to generate the Doppler spectrum signal.
17. A method for generating a Doppler spectrum signal comprising the steps of:
performing ultrasound transmissionreception in Doppler mode and ultrasound transmissionreception in other mode than Doppler mode;
performing quadrature detection on an echo signal generated from the ultrasound transmissionreception for Doppler mode;
generating a Doppler spectrum signal; and
performing an extrapolation process to estimate missing part of the Doppler spectrum signal resulting from the ultrasound transmissionreception for other mode.
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. A frequency converter for converting a single mode input beam at a fundamental frequency to an output beam at a converted frequency, comprising:
a plurality of spaced optical components defining a resonant cavity and configured to shape the input beam with at least one beam waist in the cavity, the shaped beam having a section selected from the group consisting of at least one divergent section, collimated section and a combination of these; and
a non-linear crystal located within the cavity in:
the divergent beam section of the shaped beam with a Rayleigh range smaller than a round trip length of the cavity, the crystal being located so that a center of the crystal is spaced from the beam waist along a beam path, or
the collimated beam section with a Rayleigh range greater than the round trip length.
2. The converter of claim 1, wherein the crystal is selectively positioned in a plurality of locations along the beam path so that the cavity is impedance matched at each location of the crystal for a given power of the input beam, therefore the converter is operable at a maximum conversion efficiency in a range of powers of the input beam.
3. An optical system comprising:
a continuous wave source emitting a coherent, single frequency and single mode (\u201cSM\u201d) beam at a fundamental frequency;
a collimator configured to collimate the beam downstream from the source; and
a frequency converter of claim 1.
4. The optical system of claim 3, wherein the crystal is selectively positioned in a plurality of locations along the beam path so that the cavity is impedance matched at each location of the crystal for a given power of the input beam, therefore the converter is operable at a maximum conversion efficiency in a range of powers of the input beam.
5. The optical system of claim 3, wherein the source includes a fiber laser or semiconductor laser or solid state laser or gas laser.
6. The optical system of claim 3 further comprising:
a laser head spaced from the source,
a booster fiber amplifier amplifying the beam at the fundamental frequency and mounted in the laser head along with the frequency converter, and
a fiber cable coupling the source and booster.
7. A method of reducing an optical power density on an exit face of and within a volume of a non-linear crystal located within a frequency converter, comprising:
continuously coupling a single frequency, single mode beam at the fundamental frequency into a resonator cavity of the frequency converter;
shaping the beam to form at least one beam waist within the cavity; and
placing a non-linear crystal within the cavity in a:
divergent beam with a Rayleigh range smaller than a cavity round trip length so that a center of the crystal is spaced from the beam waist along a beam path, or
collimated beam with a Rayleigh range greater than the cavity round trip length.
8. The method of claim 7, wherein the crystal is selectively positioned in a plurality of locations along the beam path so that the cavity is impedance matched at each location of the crystal for a given power of the input beam, therefore the frequency converter is operable at a maximum conversion efficiency in a range of powers of the input beam