Method for determining a height position of an object

Patent metadata

Field	Value
Publication number	US-11287629-B2
Application number	US-202117236803-A
Country	US
Kind code	B2
Filing date	Apr 21, 2021
Priority date	Mar 2, 2016
Publication date	Mar 29, 2022
Grant date	Mar 29, 2022

Abstract

A method for determining a height position of an object at of using a microscope which images using a point-spread function along a z-direction (height direction), comprising the steps of imaging the object in the far field and determining a far-field intensity, calculating a maximum intensity expected by multiplying the far-field intensity by a scaling factor, partially confocally imaging the object with the focus in the z-direction within the depth-of-field range, and determining a partially-confocal intensity of the imaging, calculating the intensity of the point-spread function (at the first location) by forming a difference between the partially-confocal intensity and a product of the far-field intensity and a predefined combination factor, calculating the z-coordinate of the focus at a point-spread function maximum, using a previously-known form of the point spread function, its calculated intensity, and the calculated expected maximum intensity, and using the z-coordinate as the height position of the object.

First claim

The invention claimed is:

1. A method for determining an elevation of an object at a lateral first location of the object and at least one laterally different second location of the object, using a microscope, which images the object with a point spread function in a z-direction that coincides with the elevation, comprising the following steps:
imaging the object with the microscope at the lateral first location in wide field and determining a wide field intensity,
calculating a maximum intensity expected at the first or second location by multiplying the wide field intensity with a specified scaling factor,
partially confocally imaging the object at the first location with the focus at a measurement position in the z-direction and partially confocally imaging the object at the second location with the focus at the same or a different measurement position in the z-direction, wherein for the partially confocal recording a pinhole device having an opening which is greater than a diffraction limit is used, and wherein the partially confocal imaging establishes a depth of field range and the focus is situated in the depth of field range, and determining a first partially confocal intensity of the partially confocal image at the first location and a second partially confocal intensity of the partially confocal image at the second location,
calculating a first intensity corresponding to the point spread function at the first location by way of subtraction between the first partially confocal intensity and the product of the wide field intensity and a specified linking factor and calculating a second intensity corresponding to the point spread function at the second location by way of subtraction between the second partially confocal intensity and the product of the wide field intensity and the specified linking factor,
calculating a z-coordinate of the focus at which the point spread function is maximum using a previously known form of the point spread function, the calculated first and second intensities corresponding to the point spread function and the calculated expected maximum intensity, and
using the z-coordinate as the elevation of the object at the first location.

2. The method according to claim 1 , wherein the scaling factor is determined by the following steps:
producing a z-stack by repeated partially confocally imaging a lateral first calibration location of a first calibration object or of the object with different foci which are shifted in the z-direction, and determining the partially confocal intensities for each of the partially confocal images,
calculating an intensity profile in the z-direction at the first calibration location, and determining a maximum calibration intensity of the intensity profile at the first calibration location,
imaging the first calibration location with the microscope in wide field, and determining a first calibration wide field intensity at the first calibration location, and
calculating the scaling factor as a ratio between the maximum calibration intensity and the first calibration wide field intensity.

3. The method according to claim 1 , wherein the linking factor is determined by the following steps:
partially confocal imaging a lateral further calibration location of a second calibration object or of the object with the focus at a calibration measurement position in the z-direction which is situated in the depth of field range, and determining a calibration intensity of the partially confocal image at the further calibration location,
confocally imaging the further calibration location with the focus at the calibration measurement position, and determining a confocal calibration intensity of the confocal image at the further calibration location,
imaging the further calibration location with the microscope in wide field, and determining a further calibration wide field intensity at the further calibration location, and
calculating the linking factor as a ratio between the difference between the partially confocal calibration intensity and the confocal calibration intensity to the further calibration wide field intensity.

4. The method according to claim 1 , wherein the first location is imaged with the microscope in wide field and in that a current wide field intensity is determined at the first location.

5. The method according to claim 1 , further comprising the following steps:
partially confocally imaging the first location with the focus at least at two measurement positions which are spaced apart in the z-direction and are situated in each case in the depth of field range, and determining partially confocal intensities for each partially confocal image at the first location,
calculating the intensities corresponding to the point spread function at the first location by way of a respective subtraction between the respective partially confocal intensity and a product of wide field intensity and the specified linking factor,
calculating the z-coordinate using the form of the point spread function, the calculated intensities corresponding to the point spread function and the calculated expected maximum intensity.

6. The method according to claim 1 , wherein for producing a live determination of an elevation of the object at the laterally second location of the object, which differs from the first one, the second location is imaged in partially confocal fashion and wherein, for calculating a z-coordinate at the second location, the z-coordinate of the focus at the first location is taken into consideration.

7. The method according to claim 1 , further comprising the following steps:
partially confocally imaging the first location with at least two different pinholes and with the focus at a measurement position in the z-direction which is situated in the depth of field range, and determining a further partially confocal intensity for the partially confocal image with the further pinhole,
calculating the z-coordinate using the form of the point spread function, the calculated intensity corresponding to the point spread function, the further partially confocal intensity and the calculated expected maximum intensity.

8. The method according to claim 1 , wherein a laser scanning microscope is used as the microscope, wherein the size of the pinhole is changed for partially confocal imaging and imaging in wide field.

9. The method according to claim 1 , wherein a laser scanning microscope is used as the microscope, wherein, for partially confocal imaging and imaging in wide field, two detectors are provided behind a pinhole of different size or wherein a wide field camera is used for imaging in wide field.

10. The method according to claim 1 , wherein a confocal topography microscope is used as the microscope, in which a grating is used as a pinhole, wherein a first camera with the grating is used for partially confocal imaging and a second camera is used for imaging in wide field.

11. The method according to claim 1 , wherein a confocal Airy microscope is used as the microscope, in which the object is imaged onto a detector device which comprises a plurality of pixels and resolves a diffraction structure of the partially confocal image, wherein the wide field intensity and the partially confocal intensity are determined from one recording or wherein a wide field camera is used for imaging in wide field.

12. A microscope for producing a partially confocal image of an object and an image of the object in wide field, comprising:
a detector device,
a pinhole device for partially confocal imaging and recording in wide field,
a focusing device, which is embodied for setting a z-position of a focus of the partially confocal ima

Assignees

• Zeiss Carl Microscopy Gmbh

Inventors

• Langholz Nils
• Drescher Viktor

Classifications

• H04N23/698

  for achieving an enlarged field of view, e.g. panoramic image capture · CPC title

• G01B11/0608

  Height gauges · CPC title

• G02B21/008 Primary

  Details of detection or image processing, including general computer control · CPC title

• G02B21/0032

  Optical details of illumination, e.g. light-sources, pinholes, beam splitters, slits, fibers (G02B21/0036 - G02B21/008; means for illumination of specimens in general G02B21/06) · CPC title

• G02B21/0072

  details concerning resolution or correction, including general design of CSOM objectives · CPC title