Apparatus and method to reduce vignetting in microscopic imaging

Patent metadata

Field	Value
Publication number	US-10502944-B2
Application number	US-201715752778-A
Country	US
Kind code	B2
Filing date	Oct 2, 2017
Priority date	Oct 2, 2017
Publication date	Dec 10, 2019
Grant date	Dec 10, 2019

Abstract

A method for altering the intensity of light across the field of view of an image sensor in a microscope apparatus having a light source, an image sensor having pixels, and a specimen stage, wherein light from the light source travels along a light path to the specimen stage and then to the image sensor includes interposing a programmable spatial light modulator, pSLM, in the light path between the light source and the image sensor, the pSLM having a plurality of pixels; and modulating the intensity of light passing through one or more pixels of the plurality of pixels of the pSLM to produce an altered illumination landscape at the field of view of the image sensor that differs from an unaltered illumination landscape that would otherwise be produced at the image sensor. Vignetting can be specifically addressed.

First claim

What is claimed is:

1. A method for correcting the intensity of light across the field of view of an image sensor in a microscope apparatus to correct for the vignetting of light from a light source of the microscope apparatus, the microscope apparatus including an image sensor having pixels, and a specimen stage, wherein light from the light source travels along a light path to the specimen stage and then to the image sensor the method comprising the steps of:
interposing a programmable spatial light modulator, pSLM, in the light path between the light source and the image sensor, the pSLM having a plurality of pixels;
modulating the intensity of light passing through one or more pixels of the plurality of pixels of the pSLM to produce an altered illumination landscape at the field of view of the image sensor that reduces the effects of vignetting of light that would otherwise be produced at the image sensor,

wherein, prior to the step of modulating, the method further includes the step of:
assessing a reference illumination landscape of the microscope apparatus, said step of assessing including:
placing a reference specimen in the field of view of the image sensor,
defining a plurality of segments of the pSLM, each segment having one or more pixels,
illuminating the reference specimen with the light source at a power level P 1 , and
separately measuring the intensity of light reaching the image sensor through each segment of the pSLM at power level P 1 , by separately allowing each segment to transmit light while the remaining segments block at least a portion of light, and

wherein said step of modulating the intensity of light passing through the pSLM includes:
identifying the segment with the lowest intensity of the reference illumination landscape, herein Smin, having an intensity ISmin; and
reducing the intensity of light passing through each of the pixels of the segments of the pSLM that are greater than ISmin at power level P 1 to more closely approach ISmin.

2. The method of claim 1 , wherein the pSLM is selected from the group consisting of liquid crystal displays, liquid crystal on silicon, digital micro-mirror devices, and suspended particle devices.

3. The method of claim 1 , wherein the altered illumination landscape has a uniformity of light intensity wherein light intensity across the field of view is within +/−5% of the average intensity across the field of view.

4. The method of claim 1 , wherein the intensity of light passing through the one or more pixels in said step of modulating is controlled by input from a processor.

5. The method of claim 4 , wherein, in said step of modulating the intensity of light, the processor controls the intensity of light passing through the one or more pixels of the pSLM by electrical signals to the one or more pixels.

6. The method of claim 1 , wherein, in said step of separately allowing each segment to transmit light while the remaining segments block at least a portion of light, the segments that block at least a portion of light transmit light at the lowest intensity permitted by the pSLM.

7. The method of claim 1 , wherein the segments defined in said step of defining a plurality of segments of the pSLM include annular segments and a center segment.

8. The method of claim 1 , wherein the reference specimen is a reference material that provides a substantially uniform background based on reflectivity, wherein reflectivity does not vary by more than 5% across the entire field of view of the image sensor.

9. The method of claim 8 , wherein, in said step of modulating the intensity of light, the processor controls the intensity of light passing through the one or more pixels of the pSLM by electrical signals to the one or more pixels.

10. The method of claim 8 , wherein, prior to said step of modulating, the method further includes the step of:
assessing a reference illumination landscape of the microscope apparatus, said step of assessing including:
placing a reference specimen in the field of view of the image sensor,
defining a plurality of segments of the pSLM, each segment having one or more pixels,
illuminating the reference specimen with the light source at a power level P 1 , and

separately measuring the intensity of light reaching the image sensor through each segment of the pSLM at power level P 1 , by separately allowing each segment to transmit light while the remaining segments block at least a portion of light.

11. The method of claim 1 , wherein the reference specimen does not present a uniform background, and the microscope is defocused to blur the reference specimen to provide a substantially uniform background based on reflectivity, wherein reflectivity does not vary by more than 5% across the entire field of view of the image sensor.

12. The method of claim 1 , further comprising an alignment step prior to said step of assessing a reference illumination landscape, said alignment step being selected from:
a. an active area defining step comprising:
i. successively activating each pixel of the pSLM to transmit light while all other pixels block at least a portion of light,
ii. capturing an image with the image sensor for each successively activated pixel, and
iii. associating each pixel of the pSLM with those pixels of the image sensor that are affected by their activation; and

b. a center alignment step comprising:
i. activating a plurality of pixels encompassing the center of the pSLM
ii. capturing an image with the image sensor for the activated plurality of pixels of step b.i.
iii. comparing the affected area of the image sensor per step b.ii. with the center of the image sensor, and, if the affected area is not centered on the image sensor,
iv. moving the pSLM in a centering direction; and

c. a pixel alignment step comprising:
i. rotating the pSLM so that x and y directions of the pSLM pixels are respectively aligned with x and y directions of the image sensor; and

d. combinations thereof.

13. A method for correcting the intensity of light across the field of view of an image sensor in a microscope apparatus to correct for the vignetting of light from a light source of the microscope apparatus, the microscope apparatus including an image sensor having pixels, and a specimen stage, wherein light from the light source travels along a light path to the specimen stage and then to the image sensor the method comprising the steps of:
interposing a programmable spatial light modulator, pSLM, in the light path between the light source and the image sensor, the pSLM having a plurality of pixels;
modulating the intensity of light passing through one or more pixels of the plurality of pixels of the pSLM to produce an altered illumination landscape at the field of view of the image sensor that reduces the effects of vignetting of light that would otherwise be produced at the image sensor,

wherein, prior to the step of modulating, the method further includes the step of:
assessing a reference illumination landscape of the microscope apparatus, said step of assessing including:
placing a reference specimen in the field of view of the image sensor,
defining a plurality of segments of the pSLM, each segment having one or more pixels,
illuminating the reference specimen with the light source at a power level P 1 , and
separately measuring the intensity of light reaching the image sensor through each segment of the pSLM at power level P 1 , by separately allowing each segment to transmit light while the remaining segments block at least a portion of light, and

wherein said step of modulating the intensity of light passing

Assignees

• Nanotronics Imaging Inc

Inventors

• Putman Matthew C
• Putman John B
• Fashbaugh Dylan
• Horstmeyer Roarke

Classifications

• H04N25/61

  the noise originating only from the lens unit, e.g. flare, shading, vignetting or "cos4" · CPC title

• G02B27/0068

  having means for controlling the degree of correction, e.g. using phase modulators, movable elements (controlling the phase of light using moving or deformable elements G02B26/06) · CPC title

• G02B21/26

  Stages; Adjusting means therefor · CPC title

• G02B21/06

  Means for illuminating specimens · CPC title

• G02B21/361 Primary

  Optical details, e.g. image relay to the camera or image sensor (G02B21/364 takes precedence; illumination details G02B21/06 and subgroups) · CPC title