Introduction
The lens is often the most overlooked part of a camera module. People focus on megapixels and sensor sensitivity, but a great sensor with a poor lens will still produce bad images. Selecting the right lens is critical whether you are building an embedded endoscope camera, an automotive inspection camera module, or a micro camera module for a medical device. At Sincere, we have manufactured cmos module camera solutions for over 30 years, and lens selection is a core part of our design process. This article walks you through the key parameters to consider when choosing a lens for any camera module sensor.
Step 1: Define Your Application
Before looking at lens specs, answer these questions:
Working distance: How far is the camera from the subject?
Field of view (FOV): How wide an area must the camera see?
Resolution needed: Will you use a high‑resolution sensor?
Lighting: Bright shop floor, dark pipe interior, or body cavity?
Size constraints: A micro camera module for a 2mm endoscope is very different from a security camera.
Step 2: Understand Key Lens Parameters
- Focal Length – Determines FOV. Short focal length (e.g., 2.8mm) = wide view; long focal length (e.g., 8mm) = narrow view. For an endoscope camera module that needs to see a large cavity, a short focal length is best.
- Field of View (FOV) – The angular extent the lens captures. For an embedded endoscope camera exploring unknown spaces, a wide FOV (90°–120°) is ideal. For precise measurement, a narrower FOV (50°–70°) with low distortion is better.
- Aperture (f‑number) – Controls light entry. Lower f‑number (e.g., f/2.0) lets in more light, good for low light, but reduces depth of field. For an automotive inspection camera module used in dark engine compartments, choose a larger aperture (f/2.0 or f/1.8).
- Depth of Field (DOF) – The range of distances that appear sharp. Endoscope cameras often need large DOF because working distance varies. Fixed‑focus lenses with small aperture (high f‑number) and short focal length provide large DOF.
- Optical Resolution – The lens must resolve enough detail for your sensor. A cmos module camera with a 5MP sensor needs a lens that can resolve 5MP. Pairing a high‑resolution sensor with a cheap, low‑resolution lens wastes the sensor's potential.
- Distortion – Bends straight lines. For measurement, choose low‑distortion lenses. For wide‑view endoscopy, some barrel distortion is acceptable.
- Lens Mount / Form Factor – Board lenses (fixed focus) are tiny and glued directly onto the sensor – common in micro camera module designs. M12 lenses are threaded, interchangeable, larger but flexible.
Step 3: Match Lens to Sensor Size
A lens designed for a 1/3" sensor has a smaller image circle than one for a 1/1.8" sensor. Using a 1/3" lens on a larger sensor causes dark corners. Always match the lens's image circle to your camera module sensor size or larger.
Step 4: Consider Environment
- Temperature: For outdoor or automotive use, glass lenses with metal housings handle temperature swings better than plastic.
- Moisture/dust: For an automotive inspection camera module used in a garage, a sealed lens prevents fogging.
- Vibration: For a micro camera module in a drone or robotic endoscope, secure lens mounting (thread lock or adhesive) is essential.
Step 5: Test with a Sample
No datasheet beats real‑world testing. Order sample lenses (or complete modules) and test them under your actual lighting and working distances. Check sharpness at center and edges, distortion, and focus consistency.
Example Lens Selections by Application
| Application | Recommended Lens Specs |
|---|---|
| Embedded endoscope camera (medical, 2mm diameter) | Fixed focus, glass or hybrid, 90° FOV, f/2.8, custom ultra‑mini |
| Automotive inspection camera module (engine bay) | M12 or board lens, 80°–100° FOV, f/2.0, glass, vibration‑resistant |
| Micro camera module (wearable or drone) | Board lens, fixed focus, 70°–90° FOV, f/2.4, plastic (lightweight) |
| General endoscope camera module (USB borescope) | Board lens, 90°–110° FOV, f/2.8, plastic or hybrid, fixed focus |
Sincere's Lens Selection Services
At Sincere, we help clients select or custom‑design lenses for their cmos module camera projects. We offer:
- Lens matching: Pairing the right lens to your camera module sensor for optimal sharpness.
- Custom lens design: For unique FOV, working distance, or size constraints (e.g., micro camera module for 1.5mm endoscope).
- Active Alignment (AA): Precisely positioning the lens relative to the sensor for consistent focus and minimal distortion.
- Testing: Validating image quality, distortion, and focus across temperature.
Summary
Selecting the right lens involves balancing focal length (FOV), aperture, depth of field, optical resolution, distortion, and physical size. Start by defining your application: working distance, target area, lighting, and environment. Then match these to a lens that fits your sensor size and mount. For specialized uses like an embedded endoscope camera, an automotive inspection camera module, or a micro camera module, always test with real samples before finalizing.
At Sincere, we have decades of experience designing endoscope camera module optics and other cmos module camera solutions. Contact us to discuss your lens requirements.
