Methods and apparatus providing calibration of foreground illumination for sample container characterization
A method of calibrating an imaging device adapted to characterize a feature of a sample container, such as a cap color or cap type. The method includes providing a calibration tube including an imaging surface at an imaging location of a first imaging apparatus; illuminating the imaging surface with light emitted from multiple front light sources; adjusting a drive current to each of the multiple front light sources to establish a substantially uniform intensity of the imaging surface; recording drive current values for the multiple front light sources; replacing the calibration tube with a calibration tool having a calibration surface of a known reflectance; and measuring target intensity values of the calibration tool at the respective drive current values. Calibration tools, imaging apparatus, quality check modules, and health check methods are provided, as are other aspects.
1 . A calibration method, comprising:
providing a calibration tube including an imaging surface at an imaging location of an imaging apparatus;
illuminating the imaging surface with light emitted from multiple front light sources;
adjusting non-zero current values of a drive current to each of the multiple front light sources to establish a substantially uniform intensity of the imaging surface;
recording drive current values for the multiple front light sources that established the substantially uniform intensity of the imaging surface;
replacing the calibration tube with a calibration tool having a calibration surface of a known reflectance; and
measuring target intensity values of the calibration tool at the respective drive current values.
2 . The calibration method of claim 1 , wherein the measuring of the target intensity values of the calibration tool at the drive current values is performed by an imaging device.
3 . The calibration method of claim 1 , wherein the adjusting the non-zero current values of the drive current to each of the multiple front light sources occurs sequentially.
4 . The calibration method of claim 1 , wherein the target intensity values comprise average intensity of a region of interest on the calibration tool.
5 . The calibration method of claim 1 , further comprising:
installing the calibration tool at an imaging location of a separate imaging apparatus; and
adjusting a drive current to a current value for each of the front light sources of the separate imaging apparatus to achieve the same target intensity values measured for the imaging apparatus.
6 . The calibration method of claim 5 , further comprising:
adjusting a drive current to a current value for each of the front light sources so that an intensity value for each of the front light sources of the separate imaging apparatus is the same as the target intensity value of each of the front light sources of the imaging apparatus.
7 . The calibration method of claim 1 , further comprising:
installing a calibration tool at an imaging location of a separate imaging apparatus;
calibrating a first drive current of a first light source of the separate imaging apparatus until an average intensity of a region of interest on the calibration tool reaches a measured target intensity value of a first light source of the imaging apparatus; and
calibrating a second drive current of a second light source of the separate imaging apparatus until an average intensity of the region of interest on the calibration tool reaches a measured target intensity value of a second light source of the imaging apparatus while turning off the first light source.
8 . The calibration method of claim 1 , further comprising:
recording a first target intensity value for a first light source of the multiple front light sources, and
recording a joint target intensity value for the multiple front light sources.
9 . The calibration method of claim 8 , further comprising:
installing a calibration tool at an imaging location of a separate imaging apparatus;
calibrating a first drive current of a first light source of the separate imaging apparatus until an average intensity of a region of interest on the calibration tool reaches the first target intensity value of the first light source of the imaging apparatus; and
calibrating a second drive current of a second light source of the separate imaging apparatus until an average intensity of the region of interest on the calibration tool reaches the joint target intensity for the multiple front light sources, while leaving on the first light source of the separate imaging apparatus.
10 . The calibration method of claim 1 , further comprising:
without the calibration tool at the imaging location,
measuring a first intensity value at a region of interest of a first front light source of the multiple front light sources with a first imaging device directly facing the first front light source, and
measuring a second intensity value at a region of interest of a second front light source of the multiple front light sources with a second imaging device directly facing the second front light source.
11 . The calibration method of claim 10 , further comprising:
at a later time, re-calibrating the imaging apparatus using the first intensity value and the second intensity value.
12 . The calibration method of claim 1 , wherein the illuminating the imaging surface with light emitted from the multiple front light sources is conducted for each spectrum of light used for the illumination.
13 . The calibration method of claim 1 , wherein the multiple front light sources comprise spectrally-switchable lighting sources that are spectrally-switchable between at least two light spectra.
14 . The calibration method of claim 1 , wherein the imaging location is located within an imaging chamber formed by a collection of walls of a housing of the imaging apparatus.
15 . The calibration method of claim 1 , wherein the calibration tube is located at the imaging location and is resident on a carrier.
16 . The calibration method of claim 1 , wherein the substantially uniform intensity of the imaging surface is measured by an imaging device and is uniform within +/−20% of an average intensity within a region of interest when measured on a pixel by pixel basis.
17 . The calibration method of claim 1 , wherein replacing the calibration tube with a calibration tool having a calibration surface of the known reflectance comprises replacing with a calibration tool of a prism shape wherein each planar side is facing an imaging device.
18 . The calibration method of claim 17 , wherein each of the sides of the calibration tool corresponding to each viewpoint of each imaging device has a certified reflectance surface of a known reflectance value.
19 . The calibration method of claim 1 , further comprising:
providing a previously-calibrated imaging apparatus that has been previously calibrated according to the calibration method of claim 1 ;
placing a calibration tool having a calibration surface of a known reflectance at an imaging location of the previously-calibrated imaging apparatus;
illuminating the calibration surface with light emitted from one or more front light sources previously calibrated;
measuring intensity values at a region of interest of the calibration surface; and
verifying that the previously-calibrated imaging apparatus is still performing within specifications based upon measured intensity values of the region of interest.