How do you determine the physical distance between the lens and the image sensor?

Have you ever been troubled by these issues?

Is the edge of the image blurring or distorting during a video conference?

Is the image slightly out of focus despite having a high-resolution lens?

After repeated adjustments, the image quality still doesn't reach professional standards?

The root cause of the problem may lie in the tiny distance between the lens and the image sensor!

1. Key Point: Flange Focal Distance

The physical distance between the lens and the image sensor is technically known as the "flange distance." It's not an arbitrary setting; it's a core parameter of precision optical design!

The accuracy of the flange distance directly determines:

Image clarity: Distance deviation will cause the image plane to shift, resulting in blur and reduced sharpness.

Edge quality: Inaccurate distance will exacerbate edge distortion and vignetting.

Focusing performance: The flange distance serves as the reference for adjusting the lens' back focus, affecting autofocus accuracy and speed.

Optical performance: Even the best lens cannot achieve its optimal optical quality without an inaccurate flange distance.

For video conferencing cameras, accurate flange distance is crucial!

Wide-angle and low distortion: Conference scenes require a wide viewing angle, and a precise flange distance ensures that people around the edges remain distorted and text is clearly legible.

Fast and precise focus: When the speaker moves or when multiple people switch, millisecond-level precision focusing relies on a stable flange distance reference.

Guaranteed high-definition image quality: 4K/8K ultra-high-definition conferencing requires micron-level optical system alignment accuracy, with flange focal distance being the foundation.

Product consistency: During mass production, strictly controlled flange focal distance is key to ensuring consistent image quality for each camera.

II. How to Determine and Maintain This "Golden Distance"?

1. Design Source: Optical Simulation First

During the lens optical design phase, the theoretically optimal flange focal distance is accurately calculated using specialized software (such as Zemax and Code V).

The design must fully consider the image sensor characteristics (size, pixel structure) and the lens' field of view and distortion control requirements.

2. Precision Manufacturing: Millimeter-Level Tolerance Control

Lens Mount: The machining accuracy of lens mounts (such as M12, M8, and C/CS) must be extremely high, and their axial dimensional tolerances directly affect the flange focal distance.

Sensor Substrate Positioning: The mounting accuracy of the sensor on the PCB and the PCB's installation and positioning within the device must be strictly controlled.

Structural Rigidity: The structural components supporting the lens and sensor must possess sufficient rigidity and stability to prevent deformation that could cause distance changes.

3. Core Process: Active Alignment and Focusing

Active Alignment: This is a core component of high-end manufacturing.

Using high-precision equipment, the image sensor's position (X/Y/Z translation and rotation) is dynamically adjusted under simulated real-world imaging conditions.

By analyzing image quality in real time (e.g., MTF modulation transfer function, center/edge sharpness, and distortion), the optimal sensor position is determined. The corresponding distance at this point is the actual optimal flange focal distance for that lens.

Back focus adjustment: Some lenses are designed with an adjustable back focus ring, which allows for fine-tuning during assembly to compensate for manufacturing tolerances and ultimately lock in the flange focal distance.

4. Environmental Testing: Stability Verification

Reliability testing, including high-temperature cycling and vibration testing, verifies the stability of the flange focal distance under various environmental stresses, ensuring it maintains stability over long-term use.

ONEKING Technology: Millimeter-Level Precision for a Professional Conferencing Experience

As the source manufacturer of core components for video conferencing cameras, ONEKING Technology understands the critical importance of flange focal distance to the final imaging result.

Precision Design: Our team of optical engineers rigorously simulates and optimizes flange focal distance during the design phase to ensure maximum optical performance.

Strict Craftsmanship: We utilize high-precision active alignment equipment and processes to fine-tune each camera's core imaging module, ensuring the theoretically optimal flange focal distance.

Strict Quality Control: We implement multiple inspection steps, including optical performance testing (sharpness, distortion, color reproduction, etc.) and environmental reliability testing, to ensure stable and reliable flange focal distances for all our products.

In-depth Collaboration: We not only provide high-quality modules, but also offer professional optical path matching and flange focal distance setting recommendations based on our customers' overall device design requirements, helping them create exceptional conferencing terminal products.