Luminescent decay time measurements by use of a CCD camera

The method of measuring a condition of a plurality of areas of a luminescent material that is characterized by emitting, in response to a pulse of excitation radiation, luminescent radiation having a rate of decay that is related to a level of said condition, comprising the steps of:

• directing repetitive pulses of excitation radiation against the luminescent material, thereby to cause the luminescent radiation to follow a repetitive cycle of building up during the excitation pulses and thence decaying between pulses at a rate related to said condition,
• positioning in a path of said luminescent radiation an array of charge coupled device elements,
• imaging said luminescent radiation onto said element array with said luminescent material areas matched to individual elements of said charge coupled device array,
• gating said charge coupled device array elements in synchronism with each other and with the excitation radiation pulses to operate during two different intervals relative to the luminescent material emission cycle,
• comparing an output during said two different intervals for the individual charge coupled device array elements, and
• converting the compared outputs to said condition, whereby the condition comparisons from each of the charge coupled device array elements corresponds to an area of the luminescent material.

A method of obtaining a visual image of a temperature profile across an area of a surface, comprising:

• coating said surface with a layer of luminescent material that is characterized by emitting, in response to a pulse of excitation radiation, luminescent radiation having a temperature related rate of decay,
• directing repetitive pulses of excitation radiation against the luminescent material layer, thereby to cause the luminescent material radiation emission to follow a repetitive cycle of building up during the excitation pulses and thence decaying between pulses an amount related to temperature,
• imaging said luminescent emission onto a two dimensional array of charge coupled device elements characterized by generating individual element signals representative of an accumulation of luminescent emission radiation intensity falling thereon over a period of time, thereby to detect said luminescent material emission from adjacent points of said surface area,
• gating said charge coupled device elements relative to timing of the excitation radiation pulses and during two different intervals of the luminescent radiation emission cycle, thereby to generate two individual charge coupled device element signals for a luminescent radiation cycle,
• comparing said two signals individually from the charge coupled device elements,
• converting the individual charge coupled device element signal comparison into temperature, and
• generating from the individual element temperature conversion a visual image corresponding to temperature across said surface area.

An imaging device, comprising:

• a video camera including a two-dimensional array of charge coupled device elements that are individually characterized by generating, after repetitively occurring frames, a signal that is related to an integrated value of electromagnetic radiation striking the element during the preceding frame,
• means including a timing circuit for controlling the timing of said camera frames,
• a source of excitation radiation for a luminescent material,
• means synchronized with said camera frame controlling means for causing said radiation source to emit a sequence of pulses with time durations therebetween, and
• means receiving the individual element signal outputs for comparing successively occurring pairs of such signals therefrom.

An infra-red camera, comprising:

• a video camera including a two-dimensional array of charge coupled device elements that are individually characterized by generating, after repetitively occurring frames, a signal that is related to an integrated value of electromagnetic radiation striking the element during the preceding frame,
• means including a timing circuit for controlling the timing of said camera frames,
• a screen having an infra-red absorbing layer on one side thereof and luminescent material on another side thereof, said luminescent material being characterized by emitting, in response to a pulse of excitation radiation, electromagnetic radiation having a rate of decay that is related to the temperature of the luminescent material,
• means for imaging an object onto said screen's infra-red absorbing layer, thereby to heat the screen in accordance with an infra-red emission image of the object,
• a source of excitation radiation directed at said screen's luminescent material layer, thereby causing an electromagnetic radiation emission therefrom with decay times that vary across the screen in accordance with the screen's temperature,
• means for imaging said luminescent material layer emission onto the charge coupled device element array,
• means synchronized with said camera frame controlling means for causing said radiation source to emit a sequence of pulses with time durations therebetween, and
• means receiving the individual element signal outputs for comparing successively occurring pairs of such signals therefrom.

A multi-channel condition measuring system, comprising:

• a plurality of optical fibers having individual sensors at one end thereof, the individual sensors including a quantity of luminescent material that is characterized by emitting, in response to a pulse of excitation radiation, luminescent radiation having a rate of decay that is related to said condition,
• an array of charge coupled device elements that are individually characterized by generating, after repetitively occurring frames, a signal that is related to an integrated value of electromagnetic radiation striking the element during the preceding frame,
• a source of excitation radiation for said luminescent material,
• optical means positioned at ends of said optical fibers opposite said sensors for coupling said excitation radiation thereinto and directing the luminescence from their individual sensors onto individual ones of said charge coupled device elements,
• means including a timing circuit for controlling the timing of said camera frames,
• means synchronized with said camera frame controlling means for causing said radiation source to emit a sequence of pulses with time durations therebetween, thereby to cause the luminescent material radiation emission to follow a repetitive cycle of building up during the excitation pulses and thence decaying between pulses in an amount related to a level of said condition, and
• means receiving the individual element signal outputs for comparing successively occurring pairs of such signals therefrom.