Convolutional layers generate feature maps by sliding shared filters over local receptive fields of the input.
Convolutional layers are the core building blocks of convolutional neural networks (CNNs). They take an input tensor (channels with spatial height and width) and apply learnable filters (kernels) across local receptive fields to produce an activation/feature map. Each neuron in a convolutional layer processes only a restricted region of the previous layer (its receptive field), and sliding the same kernel across the input generates spatially arranged responses that feed subsequent layers. A key mechanism in convolutional layers is parameter sharing: the same filter weights and bias are reused at different spatial locations (and across the depth slice), which greatly reduces the number of free parameters compared with fully connected layers. This makes CNNs more efficient, helps training stability (e.g., mitigating vanishing/exploding gradients), and supports translation-equivariant behavior (shifted inputs lead to correspondingly shifted feature maps). Convolutional layers also depend on hyperparameters such as kernel size, stride, and padding, which determine the output feature map size. Convolutional layers can be combined with other components such as pooling (for downsampling and local invariance) and nonlinear activations like ReLU. Variants like depthwise separable convolution (depthwise followed by pointwise 1×1 convolution) can speed computation, and dilated (atrous) convolutions can expand the receptive field without increasing parameter count by interleaving “blind” regions.
Convolutional layers generate feature maps by sliding shared filters over local receptive fields of the input.
Parameter sharing reduces the number of parameters versus fully connected layers and supports translation-equivariant responses.
Output size and behavior are controlled by hyperparameters such as kernel size, stride, and padding; variants like depthwise separable and dilated convolutions adjust efficiency and receptive field size.
A CNN layer that applies learnable filters across the input’s spatial dimensions to produce activation (feature) maps.
A small learnable weight tensor whose values are convolved with the input to detect specific features.
The limited region of the previous layer that a given convolutional neuron uses as input.
The practice of using the same filter weights and bias at multiple spatial locations to reduce parameters and improve generalization.
The output tensor produced by a convolutional layer, representing the filter responses across spatial locations and channels.
The step size with which the convolutional filter moves across the input, affecting the output spatial dimensions and downsampling.
Extra zeros (or other values) added around the input border to control output size and how the filter aligns with edge pixels.
A convolution variant that factorizes computation into a depthwise spatial convolution per channel followed by a pointwise 1×1 convolution.
A convolution that inserts gaps between kernel elements to expand the receptive field without increasing parameter count.
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