Views: 0 Author: Site Editor Publish Time: 2026-05-30 Origin: Site
Ultra‑miniature camera modules are the hidden eyes inside medical endoscopes, industrial borescopes, wearable devices, and even micro‑drones. Designing a camera that fits into a 2 mm diameter tube while delivering sharp, colour‑accurate images is a serious engineering challenge. In this article, we explain the key steps and trade‑offs involved in designing ultra‑miniature camera modules, from selecting the module camera sensor to assembling the final product.
A camera module is considered “ultra‑miniature” when its outer diameter is less than 4 mm, and often as small as 1 mm to 2 mm. Such modules are typically used in endoscope camera module applications, where the tip must navigate narrow blood vessels, tear ducts, or tiny engine components. Despite the size, they may need to output 720p, 1080p, or even 4K video.
Key characteristics of an ultra‑miniature design:
Extremely small lens barrel (often custom‑made glass or plastic).
Bare‑die sensor assembled with Chip‑on‑Board (COB) technology.
Flexible printed circuit (FPC) instead of a rigid PCB.
Integrated LED illumination around the lens.
Waterproof sealing (IP67/IP68) for medical or industrial use.
The sensor is the heart of any camera. For ultra‑miniature designs, you cannot use a standard packaged sensor. Instead, you need a bare die that can be wire‑bonded directly to the flex circuit. Common choices include:
OmniVision OV6948 – a 0.65 mm × 0.65 mm sensor with integrated lens, used in disposable endoscopes.
Sony IMX290 (bare die version) – 1/2.8″ sensor, much larger, but still possible in a 4‑5 mm tip.
For higher resolution, a 4k endoscope camera module may use a Sony IMX415 bare die, but this increases the tip diameter to about 4 mm.
For a basic 720p camera module, sensors like the OV9732 (1/9″) are popular. The module camera sensor determines the minimum possible diameter, so choose the smallest die that meets your resolution and low‑light requirements.
Instead of a rigid PCB, ultra‑miniature modules use a flexible printed circuit (FPC). The FPC is designed to wrap around the sensor and lens holder, saving space. The sensor bare die is attached to the FPC using Chip‑on‑Board (COB) technology:
The die is glued onto the FPC with epoxy.
Gold wires are bonded from the sensor pads to the FPC traces.
A glob top (epoxy) protects the wires.
COB eliminates the sensor package, reducing height by up to 1 mm – critical when total thickness is only 2 mm.
The lens must be as small as the sensor. For ultra‑miniature modules, there are two options:
Wafer‑level optics (WLO) – Lenses are etched onto a glass wafer and then diced. These can be as small as 0.6 mm in diameter.
Precision glass ball lenses – Tiny spherical lenses that are glued into a metal or plastic holder.
For a 720p camera module, a single plastic aspherical lens may be enough. For a 4k endoscope camera module, you need a multi‑element glass lens to resolve the high detail – this increases the tip diameter.
The lens must be placed directly over the sensor. The focal length and working distance are fixed; autofocus is almost impossible at this scale.
Even a 10‑micron shift between the lens and sensor will ruin the image. Therefore, during assembly, the lens is positioned actively – while the sensor is live, the lens is moved in X, Y, Z, tilt, and rotation while software analyses sharpness. Once the optimal position is found, the lens is glued in place with UV‑curing adhesive. This active alignment step is mandatory for any endoscope camera module that aims for consistent quality.
Most endoscope camera modules include one or more tiny LEDs around the lens. The LEDs are also bare dies (chips) mounted directly on the FPC. They are connected in series or parallel and often covered with a transparent epoxy. The LEDs must be placed as close to the lens as possible to avoid shadows.
The FPC extends from the camera head to a connector. For a USB Camera Module, the FPC may end in a USB plug or a miniature ZIF connector. For an embedded system, the cable could carry MIPI CSI‑2 signals. The cable length is limited by signal integrity; for MIPI, keep it under 30 cm; for USB, up to 3 m is possible.
The cable entry point must be sealed with epoxy or an overmoulded boot to prevent fluid ingress (IP67/IP68).
For medical or industrial use, the camera head must be waterproof. The entire assembly (sensor, wires, lens holder) is potted with medical‑grade epoxy or silicone. The lens window remains exposed. The sealing is tested by submersion or pressure decay.
Each ultra‑miniature camera module undergoes:
Optical tests – Resolution (MTF), field of view, distortion, and depth of field.
Defective pixel detection – Mapping and correcting dead pixels.
White balance calibration – To ensure consistent colour across modules.
Waterproof test – If specified.
For a 4k endoscope camera module, the test equipment must have sufficient resolution to verify 4K sharpness.
Often, a standard module does not fit a specific product. An OEM camera module manufacturer like Sincere can customise:
Diameter – From 1.5 mm to 8 mm.
Cable length – From 10 cm to 3 m.
Lens parameters – Field of view (60° to 140°), working distance (macro to infinity).
Interface – USB (UVC), MIPI, or analog.
An OEM camera module for a medical endoscope will also require biocompatible materials and sterilisation tolerance.
Suppose you need a low‑cost, ultra‑miniature USB Camera Module for automotive inspection. The design choices:
Sensor: OV9732 (720p, 1/9″, bare die) – affordable and small.
Lens: Single plastic aspherical, 90° FOV, fixed focus at 30 mm.
Assembly: COB on FPC, active alignment.
Cable: 1.5 m long USB 2.0 with overmoulded strain relief.
Housing: Stainless steel tube, IP67 rated.
Output: UVC compliant, plug‑and‑play.
This module would have a tip diameter of approximately 4 mm.
A high‑end medical endoscope camera module requires:
Sensor: Sony IMX415 bare die (8 MP, 1/2.8″).
Lens: 5‑element glass lens, 110° FOV, fixed focus.
Assembly: COB on rigid‑flex PCB, active alignment.
Cable: MIPI CSI‑2 over shielded coaxial bundle (short, <30 cm) to a separate DSP board.
Housing: Titanium tube, biocompatible, IP68.
Sterilisation: Autoclave compatible.
Diameter will be around 5‑6 mm – larger than the 720p version, but capable of 4K resolution.
Image quality vs. size – Smaller sensors have smaller pixels, which capture less light. A 720p camera module with 1.4 µm pixels will be noisier than a 1080p module with 2.0 µm pixels, but the latter requires a larger tip.
Heat dissipation – A 4k endoscope camera module generates more heat. In a tightly sealed 4 mm tube, heat can degrade the image or damage the sensor. Pulse the LEDs and reduce the frame rate to manage heat.
Yield – Ultra‑miniature COB assembly has a higher rejection rate than standard SMT. Expect a learning curve.
Designing ultra‑miniature camera modules requires a deep understanding of sensor packaging (bare die, COB), micro‑optics, active alignment, and waterproof sealing. The module camera sensor determines the minimum achievable diameter, while the lens complexity dictates the image quality. For a basic 720p camera module, a single plastic aspherical lens and a small sensor like the OV9732 suffice. For a 4k endoscope camera module, a multi‑element glass lens and a larger sensor (e.g., IMX415) are necessary, increasing the tip diameter. An OEM camera module approach allows you to customise every aspect – diameter, cable length, field of view, and interface – to fit your specific application, whether it is a disposable medical scope or an industrial borescope. If you need a USB Camera Module with ultra‑miniature dimensions, the same principles apply, but the interface is simplified to UVC over USB.
At Sincere, we design and manufacture ultra‑miniature camera modules for medical, industrial, and consumer applications. Contact us to discuss your endoscope camera module project.
