Gas visualizing apparatus and method for detecting gas leakage from tanks or piping

• US 5,430,293 A
• Filed: 04/15/1994
• Issued: 07/04/1995
• Est. Priority Date: 10/08/1991
• Status: Expired due to Fees

• Current Assignee: Osaka Gas Company Limited
• Original Assignee: Osaka Gas Company Limited
• Inventors: Nishio, Takeshi, Kanagawa, Toshihide, Sumida, Koichi, Sato, Tominori
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Glick, Edward J.
• Application Number:
  US08/228,146
• Time in Patent Office: 445 Days
• Field of Search: 250/338.5, 250/330, 250/332, 250/339.13, 250/340, 250/341, 356/437
• US Class Current: 250/330
• CPC Class Codes: G01M 3/38 by using light G01M3/02 takes precedence

Abstract

A gas visualizing apparatus includes an image sensor for detecting infrared light radiated or reflected from a background of a gas leak monitoring territory A, a laser source for emitting a detection infrared beam in two-dimensional form toward the gas leak monitoring territory A, the detection infrared beam having a wavelength absorbable by a gas "g" to be detected and a CRT for displaying information relating to gas leakage as a two-dimensional visible image corresponding to the gas leak monitoring territory A. The laser source includes a beam expander for converging or diverging the detection infrared beam to vary an area of the gas leak monitoring territory A. The image sensor includes a transmission and width varying device for setting the infrared light entering the image sensor to a band substantially centering on the wavelength of the detection infrared beam, and varying a width of the band, to realize an excellent visible image.

Claims

1. A gas visualizing apparatus comprising:

planar infrared detecting means for detecting infrared light radiated or reflected from a background of a gas leak monitoring territory;

planar infrared emitting means for emitting a detection infrared beam in two-dimensional form toward said gas leak monitoring territory, said detection infrared beam having a wavelength absorbable by a gas to be detected;

display means for displaying information relating to gas leakage as a two-dimensional visible image corresponding to said gas leak monitoring territory;

said planar infrared emitting means including irradiated area varying means for converging or diverging said detection infrared beam to vary an area of said gas leakage monitoring territory;

said planar infrared detecting means including transmission bandwidth varying means for setting a band of said infrared light incident to said planar infrared detecting means to a band which includes at least a portion of an absorption band substantially centering on the wavelength of said detection infrared beam where infrared light of this band is absorbed in said gas, said transmission bandwidth varying means also varying a width of said incident band so as to vary a ratio between an amount of information relating to said gas and an amount of information relating to said background within said incident band; and

monitor mode switching means for switching between a passive mode in which only said planar infrared detecting means is operated to detect the infrared light radiated from the background of said gas leak monitoring territory detection information thereby obtained being displayed on said display means as the information relating to gas leakage, and an active mode in which both said planar infrared emitting means and said planar infrared detecting means are operated, detection information thereby obtained being displayed on said display means as the information relating to gas leakage.

2. A gas visualizing apparatus as claimed in claim 1, wherein said planar infrared emitting means provides such an output that, when said detection infrared beam is expanded to irradiate said gas leak monitoring territory, energy of said detection infrared beam reflected from said background at least corresponds to a sum of energy radiated from said background and energy of sunlight in daytime.

3. A gas visualizing apparatus as claimed in claim 1, further comprising gas leak discriminating means for determining occurrence of gas leakage based on the detection information provided by said planar infrared detecting means, said mode switching means being operable to select said passive monitor mode in a normal situation and to automatically switch to said active monitor mode when said gas leak discriminating means determines occurrence of gas leakage.

4. A gas visualizing apparatus as claimed in claim 3, wherein said transmission bandwidth varying means provides a narrower transmission band in said active monitor mode than in said passive monitor mode.

5. A gas visualizing apparatus as claimed in claim 4, wherein said incident band includes a wavelength of 3.39 um, and said width of said incident band is variable between 0.1 and 2 um.

6. A gas visualizing apparatus comprising:

planar infrared detecting means for detecting infrared light radiated or reflected from a background of a gas leak monitoring territory;

planar infrared emitting means for emitting a detection infrared beam in two-dimensional form toward said gas leak monitoring territory, said detection infrared beam having a wavelength absorbable by a gas to be detected;

display means for displaying information relating to gas leakage as a two-dimensional visible image corresponding to said gas leak monitoring territory;

said planar infrared emitting means including irradiated area varying means for converging or diverging said detection infrared beam to vary an area of said gas leak monitoring territory;

said planar infrared detecting means including;

transmission bandwidth varying means for setting a band of said infrared light incident to said planar infrared detecting means to a band which includes at least a portion of an absorption band substantially centering on the wavelength of said detection infrared beam where infrared light of this band is absorbed in said gas, said transmission bandwidth varying means also varying a width of said incident band so as to vary a ratio between an amount of information relating to said gas and an amount of information relating to said background within said incident band; and

detection area varying means operable, upon detection of gas leakage within said gas leak monitoring territory, to zoom up a portion of said gas leak monitoring territory including a gas leaking area so as to allow said planar infrared emitting means to emit said detection infrared beam toward said portion of the gas leak monitoring territory;

gas leak discriminating means for discriminating an occurrence of gas leakage when a linear time-differentiated value or a quadratic time-differentiated value of a picture-element brightness signal of a common picture element of at least two images detected at different timings by said planar infrared detecting means exceeds a predetermined threshold value; and

storage time controlling means for controlling an accumulation time period of said detection infrared beam within a range free from screen brightness saturation, so as to adjust sensitivity of said planar infrared detecting means.

7. A gas visualizing apparatus comprising:

planar infrared detecting means for detecting infrared light radiated or reflected from a background of a gas leak monitoring territory;

planar infrared emitting means including an He--Ne laser light source for emitting a detection infrared beam in two-dimensional form toward said gas leak monitoring territory, said detection infrared beam having a wavelength absorbable by a gas to be detected;

display means for displaying information relating to gas leakage as a two-dimensional visible image corresponding to said gas leak monitoring territory;

said planar infrared emitting means including irradiated area varying means for converging or diverging said detection infrared beam to vary an area of said gas leak monitoring territory;

said planar infrared detecting means including;

transmission bandwidth varying means for setting a band of said infrared light incident to said planar infrared detecting means to a band between 0.1 and 0.22 μ

um, said band includes at least a portion of an absorption band substantially centering on a wavelength of 3.39 μ

m of said detection infrared beam where infrared light of this band is absorbed in said gas, said transmission bandwidth varying means also varying a width of said incident band so as to vary a ratio between an amount of information relating to said gas and an amount of information relating to said background within said incident band, and

detection area varying means operable, upon detection of gas leakage within said gas leak monitoring territory, to zoom up a portion of said gas leak monitoring territory including a gas leaking area so as to allow said planar infrared emitting means to emit said detection infrared beam toward said portion of said gas leak monitoring territory;

gas leak discriminating means for discriminating an occurrence of gas leakage when a linear time-differentiated value or a quadratic time-differentiated value of a picture element brightness signal of a common picture element of at least two images detected at different timings by said planar infrared detecting means exceeds a predetermined value; and

storage time controlling means for controlling an accumulation time period of said detection infrared beam within a range free from screen brightness saturation, so as to adjust a sensitivity of said planar infrared detecting means.

8. A gas visualizing apparatus comprising:

planar infrared detecting means for detecting infrared light, in two-dimensional form, radiated or reflected from a background of a gas leak monitoring territory;

display means for displaying information from said planar infrared detecting means as a two-dimensional visible image corresponding to said gas leak monitoring territory;

transmission bandwidth varying means for setting a band of said infrared light incident to said planar infrared detecting means to a band which includes at least a portion of an absorption band where an infrared light of said band is absorbed in a gas to be detected, said transmission bandwidth varying means also varying a width of said incident band so as to vary a ratio between an amount of information relating to said gas and an amount of information relating to said background within said incident band;

gas leak discriminating means for determining an occurrence of gas leakage when a linear time-differentiated value or a quadratic time-differentiated value of a picture element brightness signal of a common picture element of at least two images detected at different timings by said planar infrared detecting means exceeds a predetermined threshold value; and

storage time controlling means for controlling an accumulation time period of said detection infrared beam within a range free from screen brightness saturation, so as to adjust sensitivity of said planar infrared detecting means.

9. A gas visualizing apparatus comprising:

planar infrared detecting means for detecting infrared light, in two-dimensional form, radiated or reflected from a background of a gas leak monitoring territory;

display means for displaying information from said planar infrared detecting means as a two-dimensional visible image corresponding to said gas leak monitoring territory;

transmission bandwidth varying means for setting a band of said infrared light incident to said planar infrared detecting means to a band between 1 μ

m and 2 μ

m, said band includes at least a portion of an absorption band where infrared light of said band is absorbed in a gas to be detected, said transmission bandwidth varying means also varying a width of said incident band so as to vary a ratio between an amount of information relating to said gas and an amount of information relating to said background within said incident band;

gas leak discriminating means for determining occurrence of gas leakage when a linear time-differentiated value or quadratic time-differentiated value of a picture element brightness signal of a common picture element of at least two images detected at different timings by said planar infrared detecting means exceed a predetermined threshold value; and

storage time controlling means for controlling an accumulation time period of the detection infrared beam within a range free from screen brightness saturation, so as to adjust a sensitivity of said planar infrared detecting means.