Method of and apparatus for analysis of a sample of biological tissue cells
At least first and second digital images of the sample are acquired having different focal heights relative to a platform on which the cells are disposed. A contrast matrix is produced having elements computed in dependence upon the difference between the values of the corresponding pixels in the first and second images. A phase matrix is produced by convolution of the contrast matrix with a predetermined distance matrix. The phase matrix is used to assess characteristics of the sample, such as the presence of cells in the sample or the heights of cells in the sample.
1. A method of analysis of a sample of biological tissue cells disposed on a platform, the sample being a thin phase object and the platform being substantially transparent, the method comprising:
acquiring from light passing through the platform and the sample, using an optical system including a camera, a set of image patches of an array of respective portions of the sample;
stitching the image patches together to form an image of the sample in the form of a phase matrix; and
using the phase matrix to assess characteristics of the sample;
wherein:
at least some of the image patches are acquired while the platform and optical system are moving relative to each other; and
the sample is illuminated by a flashing light source synchronized with movement of the platform and optical system relative to each other.
2. The method of claim 1 , wherein:
the image patches for the image are of overlapping portions of the sample; and
in the step of stitching together the image patches, the image patches are blended together in the areas of overlap.
3. The method of claim 1 , wherein acquiring the image comprises:
illuminating the sample with light of a first color and while doing so acquiring a first monochrome image component of the sample;
subsequently illuminating the sample with light of a second different color and while doing so acquiring a second monochrome image component of the sample; and
combining the first and second image components to produce a color image.
4. The method of claim 3 , and further comprising:
illuminating the sample with light of a third different color and while doing so acquiring a third monochrome image component of the sample; and
combining the third image components with the first and second image components to produce the color image.
5. The method of claim 1 , wherein acquiring the image patches is performed while the platform and the optical system are moving relative to each other.
6. The method of claim 1 , and further comprising:
determining a measure of the height of the platform on which each portion of the sample is disposed; and
adjusting the focal heights of the image patches in dependence upon the respective measures of the height of the platform.
7. The method of claim 6 , wherein the phase matrix comprises a plurality of elements, and wherein each element of the phase matrix is computed so that its value is substantially proportional to a difference in focal heights of the portions of the sample.
8. The method of claim 1 , wherein focal heights of the image patches are adjusted by moving the optical element.
9. The method of claim 1 , and further comprising providing a trigger signal to the camera to commence acquisition of the image.
10. The method of claim 9 , and further comprising:
acquiring, after a delay, in response to the trigger signal, an image patch of the image patches provided the camera is not already acquiring an image patch.
11. The method of claim 10 , wherein the optical system further comprises a light source, and further comprising:
supplying the trigger signal to the light source concurrently with providing the trigger signal to the camera.
12. The method of claim 11 , wherein providing a trigger signal further comprises providing a pair of trigger signals, the first trigger signal of each pair triggering the camera and the light source, and the second trigger signal of each pair triggering the light source while the camera is acquiring an image patch.
13. An apparatus for analysis of a sample of biological tissue cells on a platform, the apparatus comprising:
an optical system including a camera and an objective optical element disposed between the camera and the platform, the optical system configured to:
acquire from light passing through the platform and the sample a set of image patches of an array of respective portions of the sample; and
a computer system configured to:
stitch the image patches together to form an image of the sample in the form of a phase matrix; and
use the phase matrix to assess characteristics of the sample;
wherein the platform and the optical system are movable with respect to each other, and
wherein:
at least some of the image patches are acquired while the platform and optical system are moving relative to each other; and
the sample is illuminated by a flashing light source synchronized with movement of the platform and optical system relative to each other.
14. The apparatus of claim 13 , wherein the image patches for the image are of overlapping portions of the sample, and the computer system is configured to blend the image patches together in the areas of overlap.
15. The apparatus of claim 13 , wherein the optical system is configured to acquire the image by:
illuminating the sample with light of a first color and while doing so acquiring a first monochrome image component of the sample;
subsequently illuminating the sample with light of a second different color and while doing so acquiring a second monochrome image component of the sample; and
combining the first and second image components to produce a color image.
16. The apparatus of claim 15 , wherein the optical system is configured to acquire the image by:
illuminating the sample with light of a third different color and while doing so acquiring a third monochrome image component of the sample; and
combining the third image components with the first and second image components to produce the color image.
17. The apparatus of claim 13 , wherein the phase matrix comprises a plurality of elements, and wherein the computer system is configured to compute each element of the phase matrix so that its value is substantially proportional to a difference in focal heights of the portions of the sample.
18. The apparatus of claim 1 , wherein the optical element is movable, and the optical system and the computer system are configured to adjust focal heights of the image patches by moving the optical element.
19. A non-transitory computer readable medium containing program instructions for a computer in the analysis of a sample of biological tissue cells disposed on a platform, the sample being a thin phase object and the platform being substantially transparent, the program instructions for causing the computer to:
cause an optical system including a camera to acquire from light passing through the platform and the sample a set of image patches of an array of respective portions of the sample;
stitch the image patches together to form an image of the sample in the form of a phase matrix; and
use the phase matrix to assess characteristics of the sample;
wherein:
at least some of the image patches are acquired while the platform and optical system are moving relative to each other; and
the sample is illuminated by a flashing light source synchronized with movement of the platform and optical system relative to each other.
20. The non-transitory computer readable medium of claim 19 , wherein the program instructions further cause the computer to:
cause the optical system to obtain the image patches for the image as overlapping portions of the sample; and
blend the image patches together in the areas of overlap during stitching.