US 5,239,175 A · Color monitoring with data storage means

Abstract

Color changes in a target, such as a chemical sensor using a colorchanging indicator reagent to detect the presence of a poisonous gas, are continuously monitored by reflecting the target (10) on to a sensor (16) light originating from first one and then another light source (12a, 12b, etc), each having a different, known emission wavelength. In each cycle, direct light from the appropriate source is also collected by another sensor (14), connected in a closed loop (26) with circuitry in which the emission intensity is compared with a known reference value (38) and which adjusts the emission intensity so as to stabilize it at this constant reference value. Once this is stabilized, the reflected light intensity signal is passed to a data store (20), after which a divider (22) produces an output signal (36) representing the ratio of the reflected light intensities in two separate cycles originating from two different light sources (12a, 12b, etc). The conduct of each cycle is controlled by timing means (18). Where there are two light sources, the wavelength of the second (12b) is outside the response range of the target, that of the first (12a) being at or near the peak target response, so that all the divider output signals represent successive values of actual reflected light intensity. These signals can be processed to show the rate of color change in the target and used to operate e.g. an alarm.

Claims12

Dependent claims

Colour monitoring apparatus for monitoring a target, comprising:

means for providing a plurality of light sources capable of intermittent operation, each light source having effectively a single emission wavelength different from that of another light source,
timing means for causing each light source to operate in turn,
a reflected light sensor, for receiving light transmitted by the sources and reflected from the target,
a direct light sensor for providing an intensity output for light directly from each of said light sources,
means for controlling intensity of each of said light sources and for stabilising the source intensity of the emission from each source at a predetermined level,
a plurality of data stores, each arranged to receive from the reflected light sensor a signal representing the intensity of reflected light from a respective light source at a respective one of the emission wavelengths,
divider means for receiving the information held in the data stores and for giving output signals each representing the ratio of two of said reflected light intensities, and
signal processing means, said signal processing means including:
means for receiving and storing a predetermined number of successive output signals from the divider means;
and
means for comparing said predetermined number of output signals to give an output signal representing one of a degree and rate of change in the ratios of the reflected light intensities, whereby a change in the ratios of the reflected light intensities corresponds to a change in the colour of the target such that the colour monitoring apparatus continuously monitors colour changes in the target.

8 more elements

A method of continuously monitoring colour changes in a target, said method comprises the steps of:

(i) directing a first emission of light having a first emission wavelength from a first source towards the target and reflecting it from the target to a reflected light sensor so as to give first output signals responsive to the intensity of the reflected light and simultaneously directing the first emission to a direct light sensor to give second output signals responsive to the intensity of the emitted light;
(ii) comparing the second output signals with a known reference value, increasing the intensity of the light emitted from the first source, until it equals the reference value, and preventing any further increase therein so as to stabilise the first source intensity;
(iii) when the said first source intensity is stabilised, storing the first output signal then being given;
(iv) repeating steps (i) and (ii) but with a second emission of light from a second source having a second emission wavelength and a second source intensity, so that the reflected and direct light sensors give third and fourth output signals in place of the first and second output signals respectively;
(v) when the second source intensity is stabilised, storing the third output signal then being given;
(vi) dividing one of the stored first and third signals by the other to produce a fifth output signal representing the ratio of the intensities of reflected light derived form the first and second emissions;
(vii) timing the cycle comprising steps (i) to (vi) to take place over a predetermined period of time, and
(viii) repeating the cycle comprising steps (i) to (vi) at least once, receiving and storing the resulting succession of fifth output signals and comparing successive fifth output signals to give final output signals representing changes in the intensity of the light reflected from the target at at least one known wavelength,
the first and second emission wavelengths being chosen to be different from each other and each being effectively a signal wavelength.

6 more elements

Dependencies are inferred from the claim text.

Color monitoring with data storage means

Life of this patent

Color monitoring with data storage means

Life of this patent

Abstract

Claims12