cmmp-resnet18-256

CIMP: Contrastive Image-Metadata Pre-training (ResNet-18, crop 256)

A contrastive encoder that aligns HAADF-STEM microscopy images with their acquisition metadata in a shared 128-d embedding space. This variant uses a ResNet-18 image encoder trained from scratch on 256x256 patches at effective batch size 512, with a 3-layer MLP metadata encoder of width 256.

Model Details

• Architecture: ResNet-18 image encoder (trained from scratch, single-channel input) + 3-layer MLP metadata encoder (hidden dim 256)
• Embedding dimension: 128
• Image input: Single-channel grayscale, 256x256 pixels
• Metadata input: 7-d z-scored vector (pixel_size, dwell_time, convergence_angle, beam_current, gain, offset, inner_collection_angle)
• Loss: Symmetric cross-entropy (CLIP-style) with learnable temperature and bias
• Parameters: ~11M (ResNet-18 backbone)

Retrieval Performance

Evaluated on the held-out validation split (733 images from the CMMP dataset).

Context among CMMP variants

Linear-Probe Metadata Recovery

A Ridge regression ($\alpha = 1.0$) trained on the frozen visual embedding recovers all seven acquisition parameters. Coefficient of determination ($R^2$), SMAPE (in physical units), and Pearson $r$:

The higher SMAPE on pixel_size, dwell_time, and beam_current is expected: those dimensions are stored log10-transformed because they span several orders of magnitude in physical units, so small residuals in log-space amplify when exponentiated back.

Training Configuration

Usage

import torch
from models import CMMP

# Load model
model = CMMP(
    meta_input_dim=7,
    embed_dim=128,
    image_encoder="resnet18",
    image_size=256,
    meta_hidden_dim=256,
    meta_num_layers=3,
)
model.load_state_dict(torch.load("model.pth", map_location="cpu"))
model.eval()

# Embed an image and its metadata
image = torch.randn(1, 1, 256, 256)   # single-channel grayscale [0, 1]
metadata = torch.randn(1, 7)           # z-scored metadata vector

with torch.no_grad():
    img_emb, meta_emb, temp, bias = model(image, metadata)
    # img_emb:  (1, 128) L2-normalized image embedding
    # meta_emb: (1, 128) L2-normalized metadata embedding

Files

• model.pth - Best checkpoint (epoch 842, highest Top-1 on val)
• config.json - Full training configuration (args.json from the run)
• training_log.csv - Per-epoch training metrics
• linear_probe_metadata.json - Ridge-probe metadata recovery metrics

Related Models

• Stemson-AI/cmmp-resnet18-512 - ResNet-18 variant trained at crop 512 (higher Top-1)
• Stemson-AI/cmmp-vit-pretrained-256 - ViT-B/16 variant
• Stemson-AI/cimp-style-transfer-512 - downstream metadata-conditioned style-transfer GAN

Citation

@misc{cimp2026,
  title={Contrastive Image-Metadata Pre-training for Materials Transmission Electron Microscopy},
  author={Channing, Georgia and Keller, Debora and Rossell, Marta D. and Torr, Philip and Erni, Rolf and Helveg, Stig and Eliasson, Henrik},
  year={2026},
}