# US 10,371,929 B2 · Autofocus imaging

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- Number: US 10,371,929 B2
- Document ID: US10371929B2
- Status: Granted
- Kind: B2
- Application number: 15/922,003
- Filed: 2018-03-15
- Published: 2018-07-26
- Granted: 2019-08-06
- Earliest claimed: 2010-05-18
- Assignees: Koninklijke Philips N.V.
- Applicants: Koninklijke Philips N.V.
- Inventors: Bas Hulsken; Sjoerd Stallinga
- Web page: https://patentgrep.com/patent/US10371929B2

## CPC

- G02B 21/245: {using auxiliary sources, detectors}
- G02B 21/36: arranged for photographic purposes or projection purposes (G02B21/18 takes precedence){or digital imaging or video purposes including associated control and data processing arrangements (image data processing per se G06T)}
- H04N 23/45: for generating image signals from two or more image sensors being of different type or operating in different modes, e.g. with a CMOS sensor for moving images in combination with a charge-coupled device [CCD] for still images
- H04N 23/673: {based on contrast or high frequency components of image signals, e.g. hill climbing method}
- H04N 25/701: Line sensors
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

The present invention relates to the field of digital pathology and in particular to whole slide scanners. Autofocus imaging can be performed by sampling a first number of pixels of a primary image sensor which is a time delay integration (TDI) sensor, and sampling a second number of pixels of an autofocus image sensor, wherein the second number is between one quarter and three quarters of the first number. Thus, continuous autofocus for rapid light scanning may be provided based on an additional image sensor that is tilted with respect to the optical axis.

## Claims

### Claim 1

An autofocus imaging system for a microscope, the autofocus imaging system comprising:
a primary image sensor arrangement comprising a primary image sensor for acquiring primary image data of an object of interest,
an autofocus image sensor for acquiring autofocus image data of an oblique section of the object of interest;
wherein the primary image sensor is configured for sampling a first number of pixels per distance in object space;
wherein the autofocus image sensor is configured for sampling a second number of pixels per distance in object space;
wherein the second number is between one quarter and three quarters of the first number; and
wherein the primary image sensor is a time delay integration (TIM) sensor.

### Claim 2 (depends on 1)

The autofocus imaging system of claim 1, wherein the second number is half of the first number.

### Claim 3 (depends on 1)

The autofocus imaging system of claim 1,
wherein a resolution of the primary image sensor is wavelength (λ)/(2*numerical aperture (NA)); and
wherein a resolution of the autofocus image sensor is λ/(NA).

### Claim 4 (depends on 1)

The autofocus imaging system of claim 1,
wherein the autofocus image sensor is tilted with respect to an optical axis of the primary image sensor.

### Claim 5 (depends on 1)

The autofocus imaging system of claim 1,
wherein the autofocus image sensor is tilted in a scan direction of the autofocus imaging system.

### Claim 6 (depends on 1)

The autofocus imaging system of claim 1, further comprising:
a beam splitter for splitting a beam from the object into a first beam towards the primary image sensor and a second beam towards the autofocus image sensor;
wherein a bean splitter fraction η between an intensity of the second beam and an intensity of the first beam is adapted to maintain an autofocus signal greater than an image sensor signal.

### Claim 7 (depends on 6)

The autofocus imaging system of claim 6, wherein the beam splitter fraction η is greater than (1−L0/Lmax), wherein L0 is a number of stages needed to focus with no autofocus sensor and Lmax is a maximum number of Time Delay Integration stages of the primary image sensor.

### Claim 8 (depends on 1)

The autofocus imaging system of claim 1,
wherein the autofocus image sensor is configured for acquiring the autofocus image data at a light frequency outside of the visible spectrum.

### Claim 9 (depends on 1)

The autofocus imaging system of claim 1,
wherein the autofocus imaging system is configured for dark field illumination of the autofocus image sensor.

### Claim 10 (depends on 1)

The autofocus imaging system of claim 1,
wherein the primary image sensor arrangement further comprises a second primary image sensor and a third primary image sensor;
wherein each of the primary image sensors of the primary image sensor arrangement is configured for detecting light of a different wavelength.

### Claim 11 (depends on 1)

The autofocus imaging system of claim 1,
wherein the primary image sensor is a line sensor; and
wherein the autofocus image sensor is a two-dimensional sensor.

### Claim 12 (depends on 1)

The autofocus imaging system of claim 1, wherein the primal), image sensor and the autofocus image sensor share a same sensing area.

### Claim 13 (depends on 1)

A microscope comprising an autofocus imaging system of claim 1.

### Claim 14

A method for autofocus imaging of a microscope, the method comprising the following steps:
acquiring primary image data of an object of interest by a primary image sensor of a primary image sensor arrangement, the primary image sensor being a time delay integration (TDI) line sensor;
acquiring autofocus image data of an oblique section of the object of interest by an autofocus image sensor;
sampling a first number of pixels per distance in object space, the first number of pixels being pixels of the TDI line sensor;
sampling a second number of pixels per distance in object space, the second number of pixels being pixels of the autofocus image sensor;
wherein the second number is between one quarter and three quarters of the first number.

### Claim 15

A non-transitory computer-readable storage medium, in which a computer program for autofocus imaging of a microscope is stored which, when executed by a processor of the microscope, causes the processor to carryout the steps of:
acquiring primary image data of an object of interest from a primary image sensor of a primary image sensor arrangement, the primary image sensor being a time delay integration (TDI) line sensor;
acquiring autofocus image data of an oblique section of the object of interest from an autofocus image sensor;
sampling a first number of pixels per distance in object space, the first number of pixels being pixels of the primary image sensor;
sampling a second number of pixels per distance in object space, the second number of pixels being pixels of the autofocus image sensor;
wherein the second number is between one quarter and three quarters of the first number.

### Claim 16

A non-transitory computer readable program medium having encoded thereon a program element for autofocus imaging of a microscope, which, when being executed by a processor of the microscope, causes the processor to carryout the steps of:
acquiring primary image data of a n object of interest from a primary image sensor, which is a time delay integration (TDI) line sensor, of a primary image sensor arrangement;
acquiring autofocus image data of an oblique section of the object of interest from an autofocus image sensor;
sampling a first number of pixels per distance in object space, the first number of pixels being pixels of the primary image sensor;
sampling a second number of pixels per distance in object space, the second number of pixels being pixels of the autofocus image sensor;
wherein the second number is between one quarter and three quarters of the first number.