1. A wavelength agile illumination system comprising:
a laser producing a pulse of light of less than 1000 femtoseconds duration;
a non-linear optical fiber receiving the pulse of light to produce a multi-frequency light pulse; and
a frequency dependent light retarder receiving the multi-frequency light pulse to produce a light signal with time varying frequency and having a center frequency that increases monotonically over time.
2. The wavelength agile illumination system of claim 1 wherein the frequency dependent light retarder is a length of dispersion-compensating fiber optic cable.
3. The wavelength agile illumination system of claim 1 wherein the frequency dependent light retarder is a combination of at least two consecutive lengths of fiber optic cable, a first providing increased delay in lower frequencies of the light pulse and a second providing increased delay in higher frequencies of the light pulse.
4. The wavelength agile illumination system of claim 1 including a spectral filter receiving the light signal with time varying frequency to selectively pass only a range of the frequencies of the light signal with time varying frequency.
5. The wavelength agile illumination system of claim 1 including a test element receiving the light signal with time varying frequency and further including a sensor for providing amplitude measurements of the light signal with time varying frequency, after passing through the test element.
6. The wavelength agile illumination system of claim 5 wherein the test element is a chamber positioned between the frequency dependent light retarder and the sensor, the chamber receiving materials to be analyzed by selective attenuation of light of the light signal with time varying frequency.
7. The wavelength agile illumination system of claim 5 wherein the test element is a sensor element modifying frequencies of the light signal with time varying frequency according to a sensor parameter to be measured.
8. The wavelength agile illumination system of claim 1 wherein the light signal with time varying frequency includes the wavelength of 1400 nanometers and has a bandwidth of greater than 100 nanometers.
9. The wavelength agile illumination system of claim 1 wherein the light retarder is a length of fiber optic cable providing increased delay in higher frequencies of the light pulse.
10. The wavelength agile illumination system of claim 1 wherein the light retarder is a length of fiber optical cable providing increased delay in lower frequencies of the light pulse.
11. A method of producing high-rate frequency swept light signals comprising the steps of:
(a) producing a multi-frequency pulse of light having less than a 1000 femtosecond duration wherein the light source is a narrow band laser providing a narrow frequency pulse to a non-linear optical cable; and
(b) passing the pulse through a fiber optic cable to selectively delay certain frequencies of light to produce a light signal with time varying frequency having a center frequency that increases monotonically over time.
12. The method of claim 11 wherein the fiber optic cable is a length of dispersion-compensating fiber optic cable.
13. The method system of claim 12 wherein the fiber optic cable is a combination of at least two consecutive lengths of fiber optical cable, a first providing increased delay in lower frequencies of the light pulse and a second providing increased delay in higher frequencies of the light pulse.
14. The method of claim 11 including the step of passing the light signal with time varying frequency through a filter to selectively pass only a range of the frequencies of the light signal with time varying frequency.
15. The method of claim 11 including a test element receiving the light signal with time varying frequency and further including the step of sensing amplitude measurements of the light signal with time varying frequency after passing through the test element.
16. The method of claim 11 wherein the light signal with time varying frequency includes the wavelength of 1400 nanometers.
17. The method of claim 16 wherein the light signal with time varying frequency provides a frequency scan rate of greater than 1 nmns.
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 vehicular brake hydraulic pressure control apparatus, comprising:
control valve units for switching between communication and shut-off of a fluid path communicated from a hydraulic pressure source to a wheel brake and switching between communication and shut-off of a fluid path communicated from the wheel brake to a reservoir; and
a control section for performing pitching reducing control to reduce occurrence of pitching on a vehicle caused by swinging of a weight, by controlling the control valve units to switch respective brake hydraulic pressures that act on the respective wheel brakes under a pressure decreasing state, a holding state, and a pressure increasing state,
wherein the control section performs the pitching reducing control, based on a weight distribution ratio between front wheels and rear wheels during deceleration, and comprises:
a distribution ratio calculating section for calculating the weight distribution ratio from deceleration of the vehicle detected from an acceleration sensor;
a vehicle speed calculating section for calculating a vehicle speed; and
a determining section for determining whether or not to perform the pitching reducing control,
and wherein the determining section determines to perform the pitching reducing control in case that conditions are satisfied, the conditions including at least that:
the calculated vehicle speed is lower than a predetermined speed at which pitching tends to occur; and
braking operation is being performed.
2. The vehicular brake hydraulic pressure control apparatus according to claim 1,
wherein the control section controls the each control valve unit such that:
if the weight distribution ratio is larger than or equal to a predetermined first threshold, the brake hydraulic pressure acting on the wheel brake be in the pressure decreasing state; and
if the weight distribution ratio is smaller than the predetermined first threshold, the brake hydraulic pressure acting on the wheel brake be in the pressure increasing state or the holding state.
3. The vehicular brake hydraulic pressure control apparatus according to claim 2,
wherein the control section controls the each control valve unit such that, if the weight distribution ratio is smaller than the first threshold and larger than or equal to a second threshold that is smaller than the first threshold, the brake hydraulic pressure acting on the wheel brake be in the pressure increasing state or the holding state.
4. The vehicular brake hydraulic pressure control apparatus according to claim 3,
wherein if the weight distribution ratio is smaller than the second threshold and a conditionconditions required for executing anti-lock brake control are satisfied, the control section performs the anti-lock brake control.
5. The vehicular brake hydraulic pressure control apparatus according to claim 1,
wherein the control section controls the each control valve unit such that, when an elapsed time of a control to make the brake hydraulic pressure acting on the wheel brake be in the holding state has become a predetermined time, the brake hydraulic pressure acting on the wheel brake turns into the pressure increasing state.
6. The vehicular brake hydraulic pressure control apparatus according to claim 2,
wherein the control section controls the each control valve unit such that, when an elapsed time of a control to make the brake hydraulic pressure acting on the wheel brake be in the holding state has become a predetermined time, the brake hydraulic pressure acting on the wheel brake turns into the pressure increasing state.
7. The vehicular brake hydraulic pressure control apparatus according to claim 3,
wherein the control section controls the each control valve unit such that, when an elapsed time of a control to make the brake hydraulic pressure acting on the wheel brake be in the holding state has become a predetermined time, the brake hydraulic pressure acting on the wheel brake turns into the pressure increasing state.
8. The vehicular brake hydraulic pressure control apparatus according to claim 4,
wherein the control section controls the each control valve unit such that, when an elapsed time of a control to make the brake hydraulic pressure acting on the wheel brake be in the holding state has become a predetermined time, the brake hydraulic pressure acting on the wheel brake turns into the pressure increasing state.
9. The vehicular brake hydraulic pressure control apparatus according to claim 1, further comprising:
a failure deciding section for determining whether or not the acceleration sensor is normally functioning,
wherein the pitching reducing control is performed only when the failure deciding section determines that the acceleration sensor is normally functioning.