Line Interleave
Line Interleave is a CMOS image sensor readout technique where two separate image streams are captured by alternating lines in the sensor, effectively doubling the output frame rate compared to capturing each image separately.
How It Works
- Alternating Lines
- The sensor designates even-numbered lines (0, 2, 4, …) for Image A and odd-numbered lines (1, 3, 5, …) for Image B.
- Interleaved Readout
- During readout, the sensor outputs the lines in alternating order (A-line, B-line, A-line, B-line) in a single scan.
- Frame Reconstruction
- Each full image is reconstructed by combining only the even or odd lines into its respective frame.
- Because both sets are acquired during the same total frame time, you get two complete images per frame time.
Why It Doubles Frame Rate
- In a normal sequential capture:
- You’d capture Frame 1 (all lines for Image A) → Frame 2 (all lines for Image B).
- This takes 2× the time.
- In line interleave mode:
- You capture both images simultaneously in a single frame period.
- This yields 2× the frame rate for each image stream.
Advantages
- Higher Temporal Resolution – Great for high-speed experiments where timing between two image streams must be minimal.
- Synchronized Capture – Both images are acquired at the same instant, minimizing motion artifacts between them.
- Ideal for Dual-Mode Imaging – Examples:
- HDR (short exposure vs. long exposure)
- Multi-wavelength (different filters for each stream)
- Stereo or dual-view setups
Trade-Offs
- Vertical Resolution Reduction – Each image has half the number of lines, so vertical resolution is reduced unless interpolation is applied.
- Post-Processing Required – Must separate even and odd lines and reconstruct full frames.
- Optical Setup Considerations – If used with different optics or filters, precise alignment is critical.