Frozen VLM Detector Head for Open-Vocabulary Object Detection

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Solution Overview

Problem

Existing object detection models struggle with open-vocabulary recognition, particularly due to the lack of scalability and the computational intensity of re-training and fine-tuning for open-vocabulary detection, especially when dealing with novel categories.

Innovation Solution

A method that trains only the detector head on a frozen vision and language model (VLM) backbone, combining detection scores with VLM predictions at test time to achieve open-vocabulary detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the entire detector head is trained from scratch or separate pre-training and fine-tuning is performed for open-vocabulary detection, then the model can achieve open-vocabulary recognition capability, but the computational resource requirements and training time increase significantly

Engineering Contradiction:
Improveopen-vocabulary recognition capabilityVSAvoidcomputational resource requirements
Core Design Contradiction:
Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The detector is divided into two independent parts: a frozen pre-trained vision and language model (VLM) backbone and a trainable detector head. The backbone remains frozen while only the detector head is trained for open-vocabulary detection, separating the general vision-language understanding from the specific detection task adaptation.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The VLM backbone is pre-trained in advance on large-scale image-text pairs to acquire general vision-language representation capabilities. This preliminary training allows the backbone to provide rich semantic knowledge and strong representations that can be directly utilized for open-vocabulary detection without re-training.

Inventive Principle:
Principle #10Preliminary action

2Adaptability or versatility

If pre-trained vision and language models are used for open-vocabulary detection, then the model can generalize to novel categories, but the re-training and fine-tuning processes become computationally intensive

Engineering Contradiction:
Improvegeneralization to novel categoriesVSAvoidtraining time
Core Design Contradiction:
Adaptability or versatilityVSLoss of time

Solution Approach 1:

The model architecture is segmented into a frozen pre-trained VLM backbone and a trainable detector head. This segmentation allows the backbone to retain its pre-trained generalization capabilities while the detector head is efficiently trained on specific detection tasks, avoiding the need to re-train the entire model.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The frozen VLM backbone serves as a pre-trained template that provides general vision-language understanding. Instead of copying or re-training the entire backbone, the invention reuses the pre-trained weights and only trains a lightweight detector head, significantly reducing training time and computational resources.

Inventive Principle:
Principle #26Copying

3Measurement precision

If a trained vocabulary is used for object detection, then the detection accuracy is improved, but the model cannot perform open-vocabulary detection for novel categories

Engineering Contradiction:
Improvedetection accuracyVSAvoidopen-vocabulary detection capability
Core Design Contradiction:
Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The pre-trained VLM backbone provides universal vision-language representation that works across multiple vocabularies and categories. By combining this universal backbone with a trainable detector head, the system achieves both accurate detection for known categories and open-vocabulary detection for novel categories without requiring separate models.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The detector head acts as an intermediary between the frozen VLM backbone and the detection task. It translates the general vision-language representations from the backbone into specific detection predictions, enabling the model to adapt to different vocabularies and novel categories while maintaining the benefits of pre-trained accuracy.

Inventive Principle:
Principle #24Intermediary (Mediator)

Data Source

PatentUS20250384650A1Open-Vocabulary Object Detection Based on Frozen Vision and Language Models
Publication Date: 2025.12.18 GOOGLE LLC
  • US20250384650A1 patent drawing
  • US20250384650A1 patent drawing
  • US20250384650A1 patent drawing

AI summary

An example method of training a detector head for object detection of a training object category based on a frozen vision and language model (VLM) is provided. The method includes receiving the frozen VLM pre-trained on a plurality of image-text pairs. The method includes determining, for an image embedding generated by a pre-trained image encoder of the frozen VLM and by the detector head, a detection region embedding indicative of one or more regions of interest in an image. The method includes generating, by a pre-trained text encoder of the frozen VLM, a text embedding of the training object category. The method includes predicting, by the detector head and based on the detection region embedding and the text embedding of the training object category, an object from a target object vocabulary associated with the training object category. The method includes providing the pre-trained frozen VLM and the trained detector head.