Description:DETAILED DESCRIPTION OF THE INVENTION:

In conventional Whole Slide Imaging (WSI) systems, the initial generation of a 3D depth map for autofocusing is critical for ensuring sharp and accurate digital slide images. A common method involves selecting a set of 9 or more initial focus points arranged in a regular rectangular grid pattern across the scanning area. While simple, this method can lead to aliasing artifacts in the interpolated depth surface due to the symmetric and repetitive structure of the sampling grid, particularly when the slide contains non-planar regions or subtle topological undulations.

Spiral-Based Sampling Innovation
We propose an enhanced sampling scheme based on a spiral pattern with equidistant spacing along the spiral path rather than fixed Cartesian grid points. This non-linear, quasi-random sampling technique offers superior spatial distribution and reduces interpolation bias and aliasing effects when generating the initial 3D surface model.

Technical Description of Spiral-Based Sampling
1. Spiral Geometry
The proposed sampling follows an Archimedean spiral or a Fermat spiral layout, defined by the polar equation:
r(θ) = a + bθ (Archimedean) or rₙ = c√n, θₙ = n·φ (Fermat)
where φ is the golden angle (~137.5°), ensuring even angular separation.
2. Equidistant Point Placement

Spiral placement distributes points more uniformly across the slide area, especially in circular or elliptical regions common in WSI scan windows. This ensures better topological coverage and reduces interpolation distortion.
3. Algorithmic Advantage

The spiral placement algorithm is efficient and allows dynamic adjustment of point numbers based on scan area. It complements adaptive sampling phases and minimizes the need for post-correction.

Benefits over Grid Sampling

Feature
Rectangular Grid
Spiral Equidistant
Aliasing Resistance Low High
Surface Fit Accuracy Moderate High
Topological Adaptability Poor Good
Visual Uniformity Rigid Natural
Application in Autofocusing

In our proposed WSI system, the initial spiral-based samples are used to create a first-pass 3D depth map. During scanning, focus inference is run at each spiral point. If the focus score is acceptable, it is accepted; otherwise, a precise focus step is triggered. The depth map is refined but initialized robustly using spiral-sampled data.
, Claims:1. A method for initial focus point selection in WSI systems using spiral-based equidistant sampling rather than a conventional grid.
2. The use of Archimedean or Fermat spiral geometries to place focus points with uniform angular separation and equidistant radial spacing.
3. An autofocusing mechanism that utilizes spiral distributed points for first pass depth map generation, followed by conditional refinement.
4. A sampling algorithm that dynamically adjusts the number of spiral points based on the scanning area.
5. An imaging system incorporating the above method to enhance auto focusing accuracy, minimize aliasing, and improve interpolation in 3D depth modeling.