US 11,889,979 B2Granted

System and method for camera calibration

AssigneeBarco N.V.

InventorsTom Kimpe, Frederik Toune, Bart Diricx, Elie De Brauwer, Albert Xthona, Johanna Rousson, Peter Nollet

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Abstract

A dermatoscope or endoscope inspection device which can be calibrated at high accuracy to be able to focus at a certain depth, e.g. below the top surface of the skin. A calibration pattern is provided or can be located at a reference viewing surface of an inspection device such as a dermatoscope or endoscope. It is important for a dermatoscope to know with the best accuracy available at what absolute depth below the top of the skin the device is focused. The dermatoscope or endoscope inspection device includes focusing means and by knowing a relationship between a digital driving level which shifts the focus position of the focusing means and the corresponding absolute change in focus depth, it is possible to know how deep the device is focused in absolute terms below the top of the skin.

Claims21

Dependent claims

A calibrated inspection unit for direct application to a skin surface of a patient, wherein a skin includes layers below the skin surface, said calibrated inspection unit comprising:

an optical array of elements in an optical path, said optical path comprising:
at least one light source,
an image capturing device configured to capture images and having a field of view,
a reference viewing surface through which the image capturing device is able to capture images,
an imaging lens having a radius of curvature and a focal length, wherein the imaging lens is configured to define a position of a focus point of the image capturing device that extends beyond the reference viewing surface along the optical path,
a fixed first calibration pattern located in a fixed position with respect to the reference viewing surface and located external to the reference viewing surface for contacting the skin surface, the fixed first calibration pattern being located at the fixed position that is at a depth that corresponds to at least one layer of the layers of the skin below the skin surface,
wherein the image capturing device is configured to capture an image of the fixed first calibration pattern, as a first image, and the image capturing device is configured to capture an image of the skin below the skin surface, as a second image, and
a focusing means for changing the focus position along the optical path as a function of adjustment values,
the calibrated inspection unit further comprising:
a calibration defining a relationship between the adjustment values of the focusing means and the positions of focus points below the skin surface, the adjustment values including a first adjustment value for the position of the focus point of the image capturing device at the fixed position of the fixed first calibration pattern,
wherein the focusing means are provided by the imaging lens which is a liquid lens, and wherein the calibrated inspection unit is configured in a way such that the fixed first calibration pattern is configured to be used for focus calibration.

8 more elements

A method for calibrating an inspection unit for direct application to a skin surface of a patient, wherein a skin includes layers below the skin surface, said inspection unit comprising an optical array of elements comprising at least one light source having a first spectral bandwidth centred on a first wavelength, an image capturing device configured to capture images and having a field of view, a reference viewing surface through which the image capturing device is able to capture images, an imaging lens having a radius of curvature and a focal length, wherein the imaging lens is configured to define a position of a focus point of the image capturing device that extends beyond the reference viewing surface along an optical axis at said first wavelength, and a reference viewing surface, a focusing means for changing the focus position along the optical axis as a function of driving values, wherein the method comprises the steps of:

providing a fixed first calibration pattern located at a fixed position with respect to said reference viewing surface and located external to the reference viewing surface for contacting the skin surface and in the field of view of the image capturing device, the fixed first calibration pattern being located at the fixed position that is at a depth that corresponds to at least one layer of the layers of the skin below the skin surface,
capturing by the image capturing device an image of the fixed first calibration pattern, as a first image, and capturing by the image capturing device an image of the skin below the skin surface, as a second image,
establishing a relationship between adjustments of the focusing means and the positions of the focus points below the skin surface, the adjustments including a first adjustment value for the position of the focus point of the image capturing device at the fixed position of the fixed first calibration pattern,
wherein the focusing means are provided by the imaging lens which is a liquid lens, and
wherein the fixed first calibration pattern is configured to be used for focus calibration.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 16/474,634Filed 30 Dec 2016
Published: US 2019/0387958 A126 Dec 2019
Granted: 6 Feb 2024
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

A61B 1/00057
Operational features of endoscopes: provided with means for testing or calibration
A61B 1/00188
Optical arrangements: with focusing or zooming features
A61B 5/0077
Using light, e.g. diagnosis by transillumination, diascopy, fluorescence: devices for viewing the surface of the body, e.g. camera, magnifying lens
A61B 5/444
Skin evaluation, e.g. for skin disorder diagnosis: evaluating skin marks, e.g. mole, nevi, tumour, scar