---
license: cc-by-4.0
tags:
  - microscopy
  - electron-microscopy
  - HAADF-STEM
  - contrastive-learning
  - CLIP
  - materials-science
  - image-retrieval
  - metadata-embedding
  - resnet
library_name: pytorch
pipeline_tag: image-feature-extraction
---

# 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).

| Metric | Value |
|---|---|
| Top-1 | **0.8438** |
| Top-5 | **0.9688** |
| Top-10 | 0.9844 |
| Best epoch | 842 / 1000 |

### Context among CMMP variants

| Variant | Top-1 | Top-5 | Top-10 |
|---|---|---|---|
| **This model** (ResNet-18, crop 256) | 0.844 | 0.969 | 0.984 |
| [ResNet-18, crop 512, batch 512](https://huggingface.co/Stemson-AI/cmmp-resnet18-512) | **0.859** | **1.000** | **1.000** |
| [ViT-pretrained, crop 256](https://huggingface.co/Stemson-AI/cmmp-vit-pretrained-256) | 0.828 | 0.969 | 1.000 |

## 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 $r$:

| Dimension | $R^2$ | SMAPE | Pearson $r$ |
|---|---|---|---|
| pixel_size | 0.720 | 41.8% | 0.849 |
| dwell_time | 0.782 | 28.4% | 0.885 |
| convergence_angle | 0.537 | 13.0% | 0.733 |
| beam_current | 0.655 | 34.7% | 0.811 |
| gain | **0.841** | **5.3%** | **0.917** |
| offset | 0.802 | 9.2% | 0.898 |
| inner_coll_angle | 0.499 | 9.5% | 0.708 |
| **Mean** | **0.691** | **20.3%** | **0.829** |

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

| Parameter | Value |
|---|---|
| Dataset | CMMP HAADF-STEM (7,330 images, 6,597/733 train/val) |
| Image encoder | ResNet-18 (trained from scratch, 1-channel input) |
| Metadata encoder | 3-layer MLP, hidden dim 256 |
| Crop size | 256x256 (on-the-fly from full-resolution images) |
| Loss function | CLIP (symmetric cross-entropy) with learnable logit bias |
| Optimizer | AdamW (lr=1e-4, weight_decay=0.01) |
| Scheduler | Cosine annealing (LR floor ~1e-10 by epoch 1000) |
| Batch size | 64 per GPU x 8 GPUs = 512 effective |
| Epochs | 1000 (best checkpoint at epoch 842) |
| Hardware | 8x H100 GPUs |

## Usage

```python
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](https://huggingface.co/Stemson-AI/cmmp-resnet18-512) - ResNet-18 variant trained at crop 512 (higher Top-1)
- [Stemson-AI/cmmp-vit-pretrained-256](https://huggingface.co/Stemson-AI/cmmp-vit-pretrained-256) - ViT-B/16 variant
- [Stemson-AI/cimp-style-transfer-512](https://huggingface.co/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},
}
```