CALIBRATION OF IMAGING DEVICE FOR BIOLOGICAL/CHEMICAL SAMPLES

• US 20110134238A1
• Filed: 06/01/2010
• Published: 06/09/2011
• Est. Priority Date: 06/01/2009
• Status: Active Grant

• Current Assignee: Bio-Rad Laboratories Incorporated
• Original Assignee: Bio-Rad Laboratories Incorporated
• Inventors: McDonald, Kevin, Bhatt, Neeraj, Schultz, Christof, Kotchou, Keith
• Granted Patent: US 8,913,127 B2
• Time in Patent Office: Days
• US Class Current: 348/140
• CPC Class Codes: G06T 2207/30024 Cell structures in vitro; Tissue sections in vitro
• CPC Class Codes: G06T 2207/30208 Marker matrix
• CPC Class Codes: G06T 7/80 Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration

Abstract

Methods, apparatuses, and systems for imaging biological/chemical samples are provided. A calibrated imaging system can allow a user to obtain an optimal focus setting (position) for any effective distance (e.g. a zoom setting). The optimal focus can be determined from a functional approximation that defines a relationship between effective distance and focus setting. A user can input a size, and an imaging system can determine the appropriate effective distance and focus. An imaging system can also determine a size based on any effective distance. A flat-field correction can also be determined for any effective distance or size.

Claims

1. A method for calibrating an imaging system for imaging biological or chemical samples, the method comprising:

for each of a plurality of initial effective distances from an optical component of the imaging system to a sample location, identifying an optimal focus setting of the optical component; and

storing means for the imaging system to determine a first functional approximation that is derived from the optimal focus settings at the initial effective distances, the means being stored in at least one computer readable medium that is adapted to be communicably coupled with the imaging system, wherein the first functional approximation is operable for calculating an optimal focus setting for a new effective distance that is not one of the initial effective distances, the new effective distance being from a biological or chemical sample to the optical component.

2. The method of claim 1, further comprising:

the imaging system receiving the new effective distance that is not one of the initial effective distances;

the imaging system determining the first functional approximation using the means stored in the at least one computer readable medium; and

the imaging system calculating an optimal focus setting for the new effective distance using the first functional approximation.

3. The method of claim 1, wherein the means for determining the first functional approximation includes a formula defining the first functional approximation and program code for retrieving the formula.

4. The method of claim 1, wherein the means for determining the first functional approximation includes the optimal focus settings for each initial effective distance and program code for calculating the first functional approximation.

5. The method of claim 1, wherein the effective distance settings are zoom settings for the optical component, and wherein the optical component is a lens.

6. The method of claim 1, wherein the optimal focus settings for the initial effective distances are determined using a calibration target, the calibration target having a higher contrast than the biological or chemical samples.

7. The method of claim 6, wherein identifying an optimal focus setting of the optical component is performed by the imaging system.

8. The method of claim 6, wherein the calibration target includes at least one object of known size, the method further comprising:

for each of a plurality of images acquired at the initial effective distances, using the identified optimal focus setting of the optical component to determine a correlation of the known size to a number of pixels;

based on the correlation of the known size to a number of pixels, determining a size of the image; and

storing means for the imaging system to determine a second functional approximation that is derived from the sizes at the initial effective distances, the means being stored in the at least one computer readable medium that is adapted to be communicably coupled with the imaging system, wherein the second functional approximation is operable for calculating an effective distance that is not one of the initial effective distances from a size

9. The method of claim 8, further comprising:

the imaging system receiving a sample size from a user;

the imaging system determining the second functional approximation using the means stored in the at least one computer readable medium;

determining an effective distance that corresponds to the sample size based on the second functional approximation; and

using the first functional approximation to select a focus setting based on the determined effective distance.

10. The method of claim 8, wherein determining a correlation of the known size to a number of pixels includes:

for each of the plurality of images acquired at the initial effective distances;

determining a distance between two features of the at least one object of known size;

identifying the two features in the image;

identifying a number of pixels between the features; and

correlating a size to a pixel using the known size and the number of pixels.

11. The method of claim 1, further comprising:

using the first functional approximation to determine an offset functional approximation that is to be used when a biological or chemical sample is offset from the sample location; and

storing means for the imaging system to determine the offset functional approximation, the means being stored in the at least one computer readable medium that is adapted to be communicably coupled with the imaging system.

12. The method of claim 11, further comprising:

for the offset of the smallest initial effective distance, identifying an optimal focus setting of the optical component; and

determining the change in the optimal focus setting at the smallest initial effective distance and the offset smallest initial effective distance, and

wherein using the first functional approximation to determine the offset functional approximation includes shifting each optimal focus setting for each initial focus setting by respective amounts proportional to the change.

13. The method of claim 1, further comprising:

determining a flat-field correction for each of the initial effective distances;

storing means for the imaging system to determine a second functional approximation that is derived from the flat-field corrections at the initial effective distances, the means being stored in the at least one computer readable medium that is adapted to be communicably coupled with the imaging system, wherein the second functional approximation is operable for calculating a flat-field correction for an effective distance that is not one of the initial effective distances, the effective distance being from a biological or chemical sample to the optical component.

14. The method of claim 13, further comprising:

the imaging system determining the second functional approximation using the means stored in the at least one computer readable medium; and

the imaging system calculating a flat-field correction for the new effective distance using the second functional approximation; and

using the flat-field correction to create a corrected image of the sample.

15. The method of claim 13, wherein the functional approximation includes a separate function for each pixel.

16. An imaging system for imaging biological or chemical samples, the imaging system comprising:

an optical component having a plurality of focus settings;

a means of changing an effective distance from the optical component to a biological or chemical sample;

a processor configured to map any effective distance to an optimal focus setting; and

a controller configured to set the optical component to have the optimal focus setting that maps to a selected effective distance.

17. The imaging system of claim 16, further comprising:

an interface for receiving the selected effective distance from a user.

18. The imaging system of claim 16, further comprising:

an interface for receiving a sample size from a user, wherein the processor is further configured to map any sample size to an effective distance, the sample size corresponding to the selected effective distance, and

wherein the means of changing the effective distance is adapted to change the effective distance to the selected effective distance based on the mapping of the processor.

19. The imaging system of claim 16, wherein the processor maps an effective distance to an optimal focus setting by determining a functional approximation and inputting the selected effective distance into the functional approximation to obtain the optimal focus setting.

20. The imaging system of claim 19, wherein the processor determines the functional approximation by reading the optimal focus settings for each of a plurality of initial effective distances and calculating the functional approximation.

21. The imaging system of claim 20, wherein the controller is configured to set the optical component to have an optimal focus setting for a new effective distance that is not one of the selected effective distances by interpolating between optimal focus settings corresponding to initial effective distances proximal to the new effective distance.

22. The imaging system of claim 16, the processor is further configured to map any input sample size to an effective distance, and then map the effective distance to an optimal focus setting.

23. A method of determining a size of a biological or chemical sample using an imaging system, the method comprising:

receiving an input effective distance between an optical component of the imaging system and the sample;

the imaging system obtaining a mapping of any effective distance to a corresponding size; and

the imaging system determining the size that corresponds to the input effective distance based on the mapping.

24. The method of claim 23, further comprising;

the imaging system providing the size to a user.

25. The method of claim 23, wherein the mapping of effective distance to size is determined using a calibration target, and wherein the calibration target includes at least one object of known size, the method further comprising:

for each of a plurality of images acquired at a plurality of initial effective distances, using an identified optimal focus setting of the optical component to determine a correlation of the known size to a number of pixels;

based on the correlation of the known size to a number of pixels, determining a size of the image; and

storing means for the imaging system to determine a functional approximation that is derived from the sizes at the initial effective distances, the means being stored in the at least one computer readable medium that is adapted to be communicably coupled with the imaging system, wherein the functional approximation is operable for calculating a size for an effective distance that is not one of the initial effective distances.

26. The method of claim 23, wherein the mapping is obtained by retrieving a plurality of initial effective distances and sizes that correspond to each initial effective distance;

using the initial effective distances and corresponding sizes to determine a function that approximates the dependence of size on effective distance.

27. The method of claim 26, wherein the function is determined using an interpolation between the effective distances proximal to the input effective distance.