Slit Lamp Spatial Light Modulation With Low-Pass Filtered Illumination

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Solution Overview

Problem

Existing slit lamp microscopes with spatial light modulators suffer from non-homogeneous illumination due to the projection of periodic light patterns, which can cause perceptible modulation in bright areas and reduce image quality, especially in specular reflections and narrow-slit examinations.

Innovation Solution

Incorporating a low-pass filter in the illumination system to attenuate specific spatial frequencies, such as beam splitters, actuators, or Fourier filters, to reduce the modulation transfer function and create a more homogeneous illumination pattern by generating spatially offset images or diffusing the light.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a spatial light modulator is used to generate structured illumination, then adaptability of illumination patterns is improved, but illumination homogeneity deteriorates due to periodic modulation artifacts

Engineering Contradiction:

Improveadaptability of illumination patternsVSAvoidillumination homogeneity

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

A low-pass filter is introduced as an intermediary component between the spatial light modulator and the object plane. This filter attenuates the periodic spatial frequency components generated by the pixel array, thereby removing the modulation artifacts while preserving the overall illumination pattern. The filter acts as a mediator that eliminates the harmful periodic structure without compromising the adaptability of the illumination shapes.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If high spatial frequency components are transmitted, then resolution is improved, but modulation artifacts become more visible

Engineering Contradiction:

ImproveresolutionVSAvoidmodulation artifacts

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The low-pass filter applies selective attenuation to different spatial frequency components. It specifically targets and attenuates the periodic spatial frequencies corresponding to the pixel modulator array (fx and fy) while preserving lower spatial frequencies that contribute to overall illumination uniformity. This local quality approach allows differential treatment of frequency components to eliminate artifacts while maintaining necessary resolution.

Inventive Principle:

Principle #3Local quality

3Shape

If the pixel modulator array structure is projected, then structured illumination is achieved, but periodic modulation in bright areas occurs

Engineering Contradiction:

Improvestructured illuminationVSAvoiduniformity in bright areas

Core Design Contradiction:

ShapeVSIllumination intensity

Solution Approach 1:

The periodic structure generated by the pixel modulator array, which initially causes harmful modulation artifacts, is transformed into a beneficial effect. By intentionally introducing a low-pass filter that attenuates these periodic components, the same structured illumination pattern becomes homogeneous in the bright areas. The periodic structure is converted from a source of artifacts into a controlled pattern that achieves both structuring and uniformity.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The low-pass filter significantly reduces the visibility of illumination inhomogeneities, enhancing image quality and reducing artifacts, particularly in high-magnification views and camera recordings, without compromising resolution.

Implementation Method 1

the imaging optics comprises a low-pass filter that attenuates at least one of the spatial frequencies fx and fy in the object plane

Methodology Applied

Scientific EffectLow-pass filtering: Filter (optical)

Implementation Method 2

the low-pass filter attenuates the modulation transfer function T between the spatial light modulator and the object plane at the spatial frequency fx much more strongly than at the spatial frequency fx/10

Methodology Applied

Scientific EffectModulation transfer function attenuation: Filter (optical)

Implementation Method 3

An electronically controlled spatial light modulator: This modulator is adapted to spatially modulate the light from the light source

Methodology Applied

Scientific EffectSpatial light modulation:

Implementation Method 4

It has an array of pixel modulators, such as an array of mirrors or liquid crystal light valves

Methodology Applied

Scientific EffectPixel modulation:

Implementation Method 5

Illumination imaging optics: These optics project the array of pixel modulators towards the object plane, thereby generating a structured light field in the object plane

Methodology Applied

Scientific EffectOptical projection: Lens

Data Source

PatentUS20260026686A1Slit lamp microscope spatial light modulator and low-pass filtering

Publication Date: 2026.01.29 HAAG STREIT AG

AI summary

The slit lamp microscope includes a microscope device projecting an object plane into an eyepiece or a camera as well as an illumination device with a spatial light modulator. The illumination device includes a beam splitter acting as a low-pass filter in order to suppress the spatial frequency of the pixels of the light modulator and to generate a more homogeneous illumination. In other embodiments, an actuator may be used to deflect at least part of the illumination imaging optics for generating a low-pass filtered image of the spatial light modulator.