Thermal dilation fiber optical flow sensor

• US 5,208,650 A
• Filed: 09/30/1991
• Issued: 05/04/1993
• Est. Priority Date: 09/30/1991
• Status: Expired due to Fees

• Current Assignee: The Government Of The United States As Represented By The Secretary Of The Navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Giallorenzi, Thomas G.
• Primary Examiner(s): Turner, Samuel A.
• Application Number:
  US07/767,189
• Time in Patent Office: 582 Days
• Field of Search: 356/345, 356/43, 356/44, 73/204.11, 73/204.16, 73/204.17, 73/204.13, 250/227.19, 250/227.27
• US Class Current: 356/477
• CPC Class Codes: G01F 1/661 using light
• CPC Class Codes: G01F 1/6884 making use of temperature dependence of optical properties

Abstract

A thermal dilation type optical flow sensor includes an optical heating sce for heating a flowing fluid and a sensor disposed in a downstream direction from said heating source wherein the sensor includes a probe for varying a reflected light according to the temperature of the probe, a Michelson type interferometer for measuring the temperature of the probe according to the phase of the reflected light, and a calculating device for determining the flow rate based on the temperature of the probe, the distance between the heating source and the probe, and the amount of heat produced by the heating source. In an alternative embodiment, a thermal dilation type optical flow sensor includes a reflecting probe disposed in a flowing fluid for reflecting an incident light with a phase varied according to the probe temperature, an optical heater for heating the probe with a predetermined heat, and a calculating device for calculating a flow rate based on the predetermined heat and the phase of the reflected light.

Claims

1. A thermal dilation type optical flow sensor comprising:

probe reflecting means disposed in a flowing fluid for reflecting incident coherent light within a light pipe, wherein a phase of a reflected light within said light pipe relative to a phase of said incident light varies according to a temperature of said probe means;

optical heating means for heating said probe means with a predetermined heat; and

measurement means for measuring said relative phase of said reflected light relative to said phase of said incident light and calculating said flow rate based on said relative phase of said reflected light relative to said incident light and said predetermined heat; and

wherein said probe reflecting means comprises;

an optical fiber disposed in said flowing fluid;

an absorbing cladding on a portion of said optical fiber comprising a material for absorbing light wherein said optical heating means comprises said absorbing material; and

a reflector disposed on a first end of said optical fiber, opposite to a second end connected to said measurement means.

2. A thermal dilation type optical flow sensor comprising:

probe reflecting means disposed in a flowing fluid for reflecting incident coherent light within a light pipe, wherein a phase of a reflected light within said light pipe relative to a phase of said incident light varies according to a temperature of said probe means;

optical heating means for heating said probe means with a predetermined heat; and

measurement means for measuring said relative phase of said reflected light relative to said phase of said incident light and calculating said flow rate based on said relative phase of said reflected light relative to said incident light and said predetermined heat; and

wherein said probe reflecting means comprises;

an optical fiber disposed in said flowing fluid;

a non-absorbing cladding on a portion of said optical fiber with an absorbing fiber jacket for absorbing light disposed therearound wherein said heating means is said absorbing fiber jacket; and

a reflector disposed on a first end of said optical fiber, opposite to a second end connected to said measurement means.

3. A thermal dilation type optical flow sensor comprising:

probe reflecting means disposed in a flowing fluid for reflecting incident coherent light within a light pipe, wherein a phase of a reflected light within said light pipe relative to a phase of said incident light varies according to a temperature of said probe means;

optical heating means for heating said probe means with a predetermined heat; and

measurement means for measuring said relative phase of said reflected light relative to said phase of said incident light and calculating said flow rate based on said relative phase of said reflected light relative to said incident light and said predetermined heat; and

wherein said probe reflecting means comprises;

an optical plate disposed in said flowing fluid, wherein said optical plate comprises a material for absorbing a portion of said light and said heating means heats the plate by the absorption of light energy in said material; and

a reflector disposed on a first side of said optical plate, opposite to a second side of said optical plate connected to said measurement means.