Method and apparatus for controlling a focus point of a stationary beam focusing on a sample in a rotating cartridge placed in a rotating disc

A method for controlling a position of a target point on a processing result relative to a focus point of a focusing sensor system for determining properties of the processing result, the method comprising the steps of:

• defining a point within a cartridge as an initial focus point of a focusing sensor system, wherein the initial focus point is a point (r, θ), where r is a fraction of the radii of the cartridge and θ is the angle between a first reference point on the cartridge and the initial focus point;
• controlling rotation of the cartridge and a disc such that the focus point of the focusing sensor system corresponds to the initial focus point by determining angular positions φ and Θ to be set for the cartridge and the disc such that the initial focus point of the focusing sensor system corresponds to the point (r, θ) within the cartridge, wherein angle Θ of the cartridge is determined relative to the first reference point on the cartridge and angle q of the disc is determined relative to a second reference point on the disc;
• checking whether the initial focus point of the focusing sensor system corresponds to the target point on the processing result by capturing images of the processing result in the cartridge and the initial focus point within the cartridge, and comparing (x, y) target positions in captured images with the initial focus point of the focusing sensor system, and adjusting rotation of the cartridge and disc such that the focus point of the focusing sensor system corresponds to the target point on the processing result;
• and
• iteratively detecting properties of the processing result by turning the disk and cartridge in equispaced steps from the target point such that an area of the processing result is scanned by the focus point of the focusing sensor system.