Periodic fringe imaging with structured pattern illumination and electronic rolling shutter detection

• US 9,386,236 B2
• Filed: 01/26/2015
• Issued: 07/05/2016
• Est. Priority Date: 01/26/2014
• Status: Expired due to Fees

• Current Assignee: Muller Imaging Technologies, Inc.
• Original Assignee: Muller Imaging Technologies, Inc.
• Inventors: Muller, Matthew Stefan
• Primary Examiner(s): Lam, Hung
• Application Number:
  US14/605,902
• Publication Number:
  US 20150215547A1
• Time in Patent Office: 526 Days
• Field of Search: 348/68, 348/70, 348/132, 348/136, 348/175, 348/177, 348/180, 348/226, 348/333.1, 348/370, 348/414.1, 348/744, 348/91, 348/2, 348/E13.018
• US Class Current: 1/1
• CPC Class Codes: G01J 3/2803 using photoelectric array detector
• CPC Class Codes: G02B 21/0032 Optical details of illumination, e.g. light-sources, pinholes, beam splitters, slits, fibers G02B21/0036 - G02B21/008; means for illumination of specimens in general G02B21/06
• CPC Class Codes: G02B 21/004 fixed arrays, e.g. switchable aperture arrays
• CPC Class Codes: G02B 21/008 Details of detection or image processing, including general computer control
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means
• CPC Class Codes: H04N 5/265 Mixing
• CPC Class Codes: H04N 5/74 Projection arrangements for image reproduction, e.g. using eidophor

Abstract

The present invention relates to a method of obtaining multiple images with a spatially varying periodic fringe pattern produced by a digital light projector that is spatially and temporally synchronized to the rolling shutter exposure of a two-dimensional pixel array detector. Two or more images obtained with phase-shifted spatial fringe patterns are combined to form a composite image with the spatial fringes and other unwanted scattered light removed.

Claims

1. A method for digital imaging, the method comprising the steps of:

operating a digital light projector to produce two or more linear illumination patterns having a pre-defined illumination pattern duty cycle that is less than 100%;

directing light from the two or more produced linear illumination patterns onto a target;

directing light from the target to a two dimensional pixel array detector having a rolling shutter exposure functionality and a pre-defined exposure time;

using a timing signal to control a spatial-temporal relationship between the rolling shutter exposure of the two dimensional pixel array detector and the two or more produced linear illumination patterns;

detecting a first image having a periodic variation in spatial intensity by setting the exposure time of the two dimensional pixel array detector to less than ten times an illumination pattern period;

adjusting a spatial-temporal relationship between the rolling shutter exposure of the pixel array detector and the two or more produced linear illumination patterns to detect one or more additional images having a change in at least one of an amplitude, frequency, or phase of a periodic variation in spatial intensity with respect to the first image; and

combining the first image and the one or more additional images to create a composite image.

2. The method of claim 1, wherein the step of operating the digital light projector to produce the two or more linear illumination patterns comprises operating a digital light projector having an illumination source, relay optics, driver electronics and a digital micromirror array.

3. The method of claim 1, wherein the step of adjusting the spatial-temporal relationship between the rolling shutter exposure and the two or more produced linear illumination patterns comprises using at least one of:

an illumination pattern exposure time;

an illumination pattern period;

an illumination pattern input trigger delay;

an illumination pattern output trigger delay;

a pixel array detector exposure time;

a pixel array detector pixel clock frequency;

a pixel array detector horizontal clock frequency;

a pixel array detector input trigger delay;

a pixel array detector output trigger delay;

at least one of a length, width, orientation, spacing and position of the two or more produced linear illumination patterns; and

a pixel array detector region of interest.

4. The method of claim 2, further comprising using image data obtained by the pixel array detector to adjust at least one of:

the spatial-temporal relationship between the rolling shutter exposure of the pixel array detector and the two or more produced linear illumination patterns;

the length, width, orientation, spacing or position of the two or more produced linear illumination patterns;

operating parameters of the illumination source, the operating parameters being selected from at least one of driving current, driving current frequency, driving current phase, driving current pulse width and duty cycle; and

operating parameters of the pixel array detector, the operating parameters being selected from at least one of frame rate, gain and pixel region of interest.

5. The method of claim 2, wherein the illumination source of the digital light projector is selected from at least one of:

a light emitting diode;

a fiber-coupled light emitting diode;

a fiber-coupled semiconductor laser source; and

a semiconductor laser source.

6. The method of claim 2, wherein the digital light projector further comprises a second illumination source for producing the two or more linear illumination patterns.

7. The method of claim 6, wherein at least one of the first and second illumination sources exhibits at least one operating parameter that is different from the other illumination source, the at least one operating parameter being selected from an illumination source wavelength, an illumination source output power, an illumination source driving current frequency, an illumination source driving current phase, and illumination source driving current pulse width and an illumination source duty cycle.

8. The method of claim 2, further comprising producing the two or more linear illumination patterns with a second digital light projector and directing produced light onto a second target.

9. The method of claim 8, wherein the two or more produced linear illumination patterns exhibit a feature that is different from the two or more illumination patterns produced by the first digital light projector, the feature being selected from at least one of:

a length, width, orientation, spacing and position of the two or more produced linear illumination patterns;

the illumination pattern period;

an illumination pattern exposure time;

the spatial-temporal relationship between the rolling shutter exposure of the pixel array detector and one of the two or more produced linear illumination patterns provided by the first digital light projector; and

operating parameters of the illumination source, the operating parameters being selected from driving current, driving frequency, driving phase, driving pulse width and duty cycle.

10. The method of claim 1, further comprising directing light from the target to a second pixel array detector having a rolling shutter exposure functionality with a pre-determined exposure time that is configured to be less than ten times the illumination pattern period to detect one or more additional images with a change in at least one of amplitude, frequency or phase of a periodic variation in spatial intensity with respect to a first image.

11. The method of claim 10, wherein the rolling shutter exposure of the second pixel array detector exhibits a feature different from the rolling shutter exposure of the first pixel array detector, the feature being selected from at least one of:

an orientation of the rolling shutter exposure;

an exposure time;

the spatial-temporal relationship between the rolling shutter exposure of the first pixel array detector and the two or more produced linear illumination patterns provided by the digital light projector; and

operating parameters of the first pixel array detector, the operating parameters being selected from frame rate, pixel clock frequency, horizontal clock frequency, gain and pixel region of interest.

12. The method of claim 8, further comprising directing light from the second target to a second pixel array detector having a rolling shutter exposure functionality with a pre-determined exposure time that is configured to be less than ten times the illumination pattern period to detect one or more additional images with a change in at least one of the amplitude, frequency or phase of a periodic variation in spatial intensity with respect to a first image.

13. The method of claim 1, further comprising directing light from the target to a second pixel array detector having a rolling shutter exposure functionality with at least one of a global reset feature and a pre-defined exposure time that is set to be greater than ten times the illumination pattern period to detect an image with lower amplitude in the periodic variation in spatial intensity with respect to the first image.

14. The method of claim 1, further comprising directing light from the target to a second pixel array detector having a global shutter exposure functionality.

15. The method of claim 1, wherein the step of producing an illumination pattern with a duty cycle less than 100% is achieved using at least one of:

an illumination source driving current having a duty cycle less than 100%; and

a digital micromirror array driving current having a duty cycle less than 100%.