Position Measuring Device Error Correction via Data Compression

Solution Overview

Problem

High-precision position-measuring devices require extensive correction tables with millions of individual correction values, leading to substantial memory requirements and increased processing time, especially in dynamic applications like lithography machines, where only a few microseconds are available for generating corrected position values.

Innovation Solution

The method involves compressing correction values by selecting and storing them only for a portion of correction points in a partial correction table and using correlation information to correlate these values during measurement, reducing the number and data word width of correction values, and combining them into group correction values for efficient storage and processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If correction tables with millions of individual correction values are used to achieve high measurement precision, then measurement precision is improved, but memory requirements and processing time increase substantially

Engineering Contradiction:

Improveposition measurement precisionVSAvoidmemory space required

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The correction table is divided into multiple segments, each containing correction values for a specific range of measurement positions. Instead of storing all correction values in a single large table, the system segments the measurement range and stores correction values only for currently needed segments, reducing overall memory requirements while maintaining precision.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a hierarchical structure with multiple levels of correction data. Correction values are organized in a multi-dimensional framework where coarse correction data covers the entire measurement range, and fine correction data covers only specific sub-ranges. This dimensional organization allows the system to achieve high precision where needed while minimizing total memory usage.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Measurement precision

If correction tables with millions of individual correction values are used to achieve high measurement precision, then measurement precision is improved, but processing time increases

Engineering Contradiction:

Improveposition measurement precisionVSAvoidprocessing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The correction table is divided into multiple segments, each containing correction values for a specific range of measurement positions. Instead of storing all correction values in a single large table, the system segments the measurement range and stores correction values only for currently needed segments, reducing overall memory requirements while maintaining precision.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system pre-loads correction values for the current measurement segment into fast memory before they are needed for correction calculations. This preliminary action ensures that when correction is required, the data is already available in high-speed memory, minimizing processing time during actual measurement operations.

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If correction tables are transmitted to signal-processing units via standard interfaces, then system complexity is reduced, but transmission time increases

Engineering Contradiction:

Improveinterface complexityVSAvoidtransmission time

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The correction table is divided into multiple segments, each containing correction values for a specific range of measurement positions. Instead of storing all correction values in a single large table, the system segments the measurement range and stores correction values only for currently needed segments, reducing overall memory requirements while maintaining precision.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system pre-loads correction values for the current measurement segment into fast memory before they are needed for correction calculations. This preliminary action ensures that when correction is required, the data is already available in high-speed memory, minimizing processing time during actual measurement operations.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS10060772B2Method for correcting errors in position-measuring devices

Publication Date: 2018.08.28 DR JOHANNES HEIDENHAIN GMBH

AI summary

A method corrects errors in position-measuring devices having material measures which are scanned by at least one scanning unit. Correction values are obtained in a calibration performed prior to a measurement operation. The correction values from the calibration are compressed for the measurement operation. The correction values are kept available for a defined number of correction points on the material measure and used during the measurement operation to correct acquired position values.