Method and system of reducing false triggering of an X-ray sensor

• US 8,324,587 B2
• Filed: 01/25/2012
• Issued: 12/04/2012
• Est. Priority Date: 10/27/2008
• Status: Active Grant

• Current Assignee: Dental Imaging Technologies Corporation (Envista Holdings Corporation)
• Original Assignee: Imaging Sciences International LLC (Envista Holdings Corporation)
• Inventors: Zeller, Uwe
• Primary Examiner(s): Sung, Christine
• Application Number:
  US13/358,125
• Publication Number:
  US 20120119099A1
• Time in Patent Office: 314 Days
• Field of Search: 250/370.09
• US Class Current: 250/370.09
• CPC Class Codes: A61B 6/4233 using matrix detectors
• CPC Class Codes: A61B 6/508 for non-human patients
• CPC Class Codes: A61B 6/51 for dentistry
• CPC Class Codes: G01T 1/17 Circuit arrangements not adapted to a particular type of detector pulse-selection circuits H03K, G01R
• CPC Class Codes: G01T 1/2928 using solid state detectors
• CPC Class Codes: G03B 42/042 for dental applications radiation diagnosis specially adapted for dentistry A61B6/51; individual packages for X-ray film G03C3/003
• CPC Class Codes: H01L 27/146 Imager structures
• CPC Class Codes: H04N 23/30 for generating image signals from X-rays
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 5/32 Transforming X-rays cameras or camera modules for generating image signals from X-rays H04N23/30; circuitry of SSIS for transforming X-rays into image signals H04N25/30

Abstract

A system and method for automatic detection of x-rays at an x-ray sensor. A source emits x-ray radiation towards an x-ray sensor, and the x-ray sensor automatically detects the x-ray radiation. The x-ray sensor automatically detects x-ray radiation by evaluating a time series and determining that a voltage threshold is crossed a certain amount of time earlier than the average time it takes the voltage threshold to be crossed from dark current and other noise.

Claims

1. A method of automatically detecting x-ray radiation with an x-ray sensor, the method comprising:

resetting a pixel array;

determining a dark current time;

measuring an elapsed time since resetting of the pixel array;

performing a comparison; and

determining that x-ray radiation has been received at at least a portion of the pixel array based on the comparison.

2. The method of claim 1, wherein performing the comparison includes comparing a difference between the elapsed time and the dark current time with at least one of

a predetermined value, and

a product of a fine tuning variable and a standard deviation of the dark current time.

3. The method of claim 2, wherein x-ray radiation is determined to have been received at the at least a portion of the pixel array if the difference is greater than the at least one of the predetermined value or the standard deviation.

4. The method of claim 1, wherein the dark current time is determined based on iteratively calculating an elapsed time between a reset of the pixel array and a determination that a trigger threshold has been crossed.

5. The method of claim 1, wherein the dark current time indicates a temperature of the x-ray sensor.

6. The method of claim 5, further comprising generating an error condition if the temperature of the x-ray sensor indicated by the dark current exceeds a predetermined level.

7. The method of claim 1, further comprising determining that a trigger threshold has been crossed, wherein the threshold is a predetermined voltage level, and wherein the predetermined amount of charge stored on the at least a portion of the pixel array causes a voltage potential at a diode to drop below the threshold.

8. The method of claim 1, further comprising

determining that x-ray radiation is no longer being received, and

reducing an integration time for a subsequent x-ray radiation exposure based on a duration of x-ray radiation received at the at least a portion of the pixel array.

9. An x-ray sensor that automatically detects receipt of x-rays, the x-ray sensor including a processor and a pixel array, the processor configured to:

reset the pixel array;

determine that a trigger threshold has been crossed,

measure an elapsed time since resetting of the pixel array;

determine an average dark current trigger time;

perform a comparison based upon the elapsed time and the average dark current trigger time;

determine that x-ray radiation has been received at at least a portion of the pixel array based on the comparison; and

upon determining that x-ray radiation has been received, output data from the pixel array to be used to generate an x-ray image.

10. The x-ray sensor of claim 9, wherein the processor is further configured to perform the comparison by comparing a difference between the elapsed time and the average dark current trigger time with at least one of

a predetermined value, and

a product of a fine tuning variable and a standard deviation of the average dark current trigger time.

11. The x-ray sensor of claim 10, wherein x-ray radiation is determined to have been received at the at least a portion of the pixel array if the difference is greater than the at least one of the predetermined value or the standard deviation.

12. The x-ray sensor of claim 11, wherein the average dark current trigger time is based on iteratively calculating an elapsed time between a reset of the pixel array and a determination that the threshold has been crossed due to dark current.

13. The x-ray sensor of claim 9, wherein the average dark current trigger time indicates a temperature of the x-ray sensor.

14. The x-ray sensor of claim 13, wherein the processor is further configured to generate an error condition if the temperature of the x-ray sensor indicated by the average dark current trigger time exceeds a predetermined level.

15. An x-ray sensor that automatically detects receipt of x-rays, the x-ray sensor including a processor and a pixel array, the processor configured to:

reset the pixel array;

determine that a trigger threshold based on dark current has been crossed,

measure an elapsed time since resetting of the pixel array;

determine an average dark current trigger time;

perform a comparison based upon the elapsed time and the average dark current trigger time;

determine that x-ray radiation has been received at at least a portion of the pixel array based on the comparison; and

upon determining that x-ray radiation has been received, output image data from the pixel array.