Views: 0 Author: Site Editor Publish Time: 2026-06-05 Origin: Site
An endoscope camera module relies on built‑in LEDs to illuminate dark, narrow cavities inside the human body or industrial machinery. Unlike a studio light or a camera flash, endoscope LEDs must fit into a tiny tip (often 3‑8 mm in diameter), produce enough light for a cmos camera module to capture a clear image, and avoid overheating tissue or components. Designing effective LED lighting for endoscopes is a careful balance of optical, thermal, and electrical engineering.
The environment inside an endoscope is completely dark. Without illumination, even the most sensitive cmos camera module would see nothing. LEDs are the preferred light source because they are:
Small – Bare LED dies can be as tiny as 0.5 mm × 0.5 mm.
Efficient – They convert most energy into light, not heat.
Long‑lasting – No filament to burn out.
Easily controlled – Brightness can be adjusted via pulse‑width modulation (PWM).
A typical endoscope camera module contains two to eight white LEDs arranged around the lens. For specialised applications, UV or infrared LEDs may be used for fluorescence or night vision.
Space constraints – The LED ring must fit around the lens within a few millimetres.
Heat dissipation – LEDs generate heat, and inside a sealed endoscope tip, there is no airflow. Excessive heat can damage the cmos camera module or cause patient discomfort.
Uniform illumination – The light must be evenly distributed across the field of view, without a dark spot in the centre or bright reflections at the edges.
Power consumption – For battery‑operated USB Camera Module endoscopes, LED power must be minimised to prolong battery life.
Biocompatibility – For medical use, all materials (LED encapsulants, wiring, adhesives) must be biocompatible and sterilisation‑tolerant.
LEDs for endoscopes are typically chosen based on:
Size – Bare‑die LEDs (no plastic package) are the smallest. Packaged LEDs (e.g., 0402 or 0603 SMD) are slightly larger but easier to handle.
Colour temperature – 5000‑6500 K (cool white) is common for industrial borescopes. For medical use, neutral white (4000‑5000 K) provides better tissue colour differentiation.
Luminous intensity – Measured in millicandelas (mcd) or lumens. A typical endoscope needs 10‑50 lm total.
Beam angle – Wide‑angle LEDs (120‑150°) are preferred to illuminate the whole scene without a central hot spot.
For a HD camera module (1080p), LEDs with a colour rendering index (CRI) above 80 are recommended to show true tissue colours.
The most common arrangement is a circular ring of LEDs surrounding the lens. The number of LEDs depends on the tip diameter and required brightness:
2‑3 LEDs – For a mini endoscope with a tip under 3 mm. The gaps between LEDs can cause shadows; therefore, a diffuser or reflective coating may be added.
4‑6 LEDs – For a typical 5‑6 mm industrial borescope. The LEDs are evenly spaced for uniform light.
8+ LEDs – For large‑diameter (>8 mm) medical scopes with fibre‑optic backup.
The LEDs should be placed as close to the lens as possible, but not so close that the lens barrel casts a shadow. Often, the PCB or flexible circuit is designed with cut‑outs that allow the LEDs to sit flush with the lens holder.
Even if LEDs are physically symmetric, the light distribution may still be uneven due to:
Shadow from the lens barrel – The lens protrudes slightly; its edge can block part of the LED’s light. A chamfered lens holder or a reflective ring can reduce this effect.
Hot spot in the centre – If the LEDs are too directional, the centre may appear brighter. Adding a diffuser (a thin frosted glass or plastic window) spreads the light evenly.
Glare and reflections – When inspecting shiny metal or wet tissue, direct reflections (specular glare) can blind the camera. Tilting the LEDs slightly outward or using cross‑polarisation can minimise this.
For an OEM camera module, the optical engineer can simulate the illumination pattern using ray‑tracing software (e.g., Zemax, LightTools) before building a prototype.
Heat is the silent enemy of both LEDs and CMOS sensors. In a sealed endoscope tip, the temperature can rise quickly if the LEDs are driven at full power. Strategies to manage heat include:
Use high‑efficiency LEDs – More light per watt means less waste heat.
Drive LEDs with pulsed current (PWM) – Instead of constant current, pulse the LEDs at a high frequency (1‑10 kHz). The eye perceives this as continuous light, but the average current – and heat – is lower.
Reduce LED current – Often, 50‑70% of rated current is sufficient for good image quality.
Thermal interface – The LED’s thermal pad should be soldered to a copper area on the PCB, which in turn is connected to a metal housing (e.g., stainless steel tube) that acts as a heat sink.
For a USB Camera Module that is used intermittently (e.g., a DIY borescope), heat is less critical. For a medical UVC camera module that may run for 30 minutes continuously, thermal design is essential.
LEDs are typically connected in parallel (each with its own current‑limiting resistor) or in series (with a constant‑current driver). For endoscopes:
Parallel with resistors – Simple and cheap, but the brightness may vary slightly between LEDs. Suitable for low‑cost OEM camera module designs where uniformity is not critical.
Series with constant‑current driver – All LEDs share the same current, ensuring identical brightness. A small IC (e.g., CAT4104, PAM2804) can drive up to 4 LEDs from a 3.3 V or 5 V supply. This is preferred for medical and high‑end industrial modules.
The LED current is usually adjustable via a potentiometer, a voltage input, or a PWM signal from the camera’s processor. The user can then dim the light to avoid glare or save power.
The LED ring is often assembled together with the lens and the cmos camera module into a single tip. The manufacturing process typically follows these steps:
The flexible PCB (or rigid‑flex board) is populated with LEDs and passive components.
The sensor (bare die or packaged) is attached and wire‑bonded (COB process).
The lens is actively aligned and glued.
The LED ring is tested for brightness and colour uniformity.
The entire tip is potted with transparent or opaque epoxy, leaving only the lens and LED windows exposed.
For a UVC camera module (USB endoscope), the same assembly is used, and the cable is overmoulded for strain relief and waterproofing.
Suppose you are building a USB Camera Module for automotive inspection. The tip diameter is 5.5 mm, and you have a 1080p HD camera module with a 2 mm lens. You decide to use four white 0402 packaged LEDs, each rated at 2 lm.
Place the LEDs at 90° intervals around the lens.
Use a constant‑current driver (e.g., PAM2804) set to 20 mA per LED.
Add a thin diffuser film between the LEDs and the lens window.
Drive the LEDs via PWM (2 kHz) to allow dimming from the host software.
The result is a bright, even illumination with minimal heat, sufficient for seeing engine cylinder walls up to 100 mm away.
Designing LED lighting for endoscopes requires balancing small size, uniform illumination, heat management, and power efficiency. The LEDs must be carefully selected, placed symmetrically around the lens, and driven by a suitable circuit. For medical applications, thermal control and biocompatibility are paramount. For consumer USB Camera Module endoscopes, cost and ease of assembly are more important.
Whether you need a simple UVC camera module for a DIY borescope or a fully custom OEM camera module for a medical endoscope, the principles remain the same: use high‑efficiency LEDs, manage heat, and ensure even light distribution. A well‑lit endoscope allows the cmos camera module to capture clear, diagnostic‑quality images – even in the darkest cavities.
If you require a custom endoscope camera module with optimised LED lighting, contact Sincere. We design and manufacture HD camera module, USB Camera Module, and OEM camera module solutions for medical, industrial, and consumer applications.
