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Playing Detective with CNNs(Convolutional Neural Networks)

Sanjana Ramprasad

Audience level: Intermediate
Topic area: Modeling

Description

We aim to differentiate between two handwriting samples by modeling and learning between writer variation and within writer variation. In order to achieve this task we use a dataset of handwriting samples which was a true representative of the US population. We went about by training a Convolutional Neural Network(CNN) and tuning it by experimenting with several architectures and techniques.

Abstract:

"With the growing popularity Convolutional Neural Networks(CNNs) in computer vision tasks and the ability of them to model intricate patterns in data, we took to extending the study of verifying handwriting using CNNs. Handwriting has been considered to be unique for each individual, which is why they are still of considerable importance in legal documents. Although handwriting is considered to be unique, there still exists variations within a writer's handwriting. We thus seek to build a model that can successfully differentiate writers while remaining invariant to within writer changes without feature engineering as used by previous models.(Individuality of Handwriting, S. N. Srihari et.al 2002).\newline We use the CEDAR ,word-level ""and"" dataset to train and experiment with several CNN architectures based on differences in filter size, feature maps, activation functions, regularization techniques, cost functions, width and depth of the model, pooling operations, strides and optimization techniques. While experimenting with an architecture, we found the model behaved with certain trends, by modeling several of these trends we get an intuitive understanding of the effect of each of these parameters on the model's performance. We use this understanding in each experiment for developing our final architecture. We further split the final architecture into two CNN architectures with the same parameter tuning along with weight and variable sharing and saw a spike in performance.\newline The primary objective of our experiments was to test how handwriting verification performs without any feature engineering and using Convolutional Neural Networks for feature extraction. However, we also gain several insights into trends in different architecture results with respect to the dataset and develop a final combination of parameters that was found to perform the best. We hope these insights could be used while tuning more complex models. \newline

We test the model's performance by identifying two types of error based on model writers: 1) Samples from a known writer - This includes for testing variation within writer's samples seen before as well as between writers 2) Samples from an unknown writer- This includes for testing the generalizing capability of the model on samples of never before seen writers. By measuring these two kinds of errors, we arrive at an architecture that performs optimally for both."