Machine vision camera interfaces compared, from Camera Link to USB3

Four standards carry almost every machine vision image shipped today: Camera Link, CoaXPress, GigE Vision and USB3 Vision. The choice decides cable runs, host hardware, power wiring and trigger behaviour long before sensor specifications enter the picture. This comparison puts the four side by side on the numbers that decide it: payload bandwidth, cable reach, power over the cable and trigger latency. A worked example then runs one 12 MP sensor through two of the interfaces so you can see where the megabytes actually go, and every case ends with a firm pick.

The decision first

Pick by case, not by habit:

• One camera, under 5 m of cable, up to roughly 360 MB/s: USB3 Vision. One cable into any PC port, up to 4.5 W of bus power, no interface card.
• Moderate bandwidth over 10-100 m, or several cameras along one machine: GigE Vision. Budget about 110 MB/s per camera per port, and add PoE where the camera needs it.
• More than about 350 MB/s per camera, a line scan trigger that must be deterministic, or 13 W at the camera: CoaXPress.
• An existing Camera Link estate, or packet-free hardware signalling inside 15 m: Camera Link, at 255 MB/s (Base) up to 850 MB/s (Deca on two cables).

Connector style, GenICam device models and SDK structure now look similar across all four; the pipe, the reach and the power do not.

The four standards at a glance

Two conversions sit behind the table. A 1 Gbit/s line rate is 125 MB/s raw; after protocol overhead, budget about 110 MB/s of image data per port. CoaXPress line rates are 8b/10b coded: 6.25 Gbit/s × 0.8 = 5 Gbit/s = 625 MB/s of payload per link, and six links in one connector reach the standard's 3.6 GB/s aggregate.

Bandwidth: what each pipe really carries

Camera Link steps through four configurations at the 85 MHz chip rate: Base carries 2.04 Gbit/s (255 MB/s) on one cable, Medium 510 MB/s, Full 680 MB/s, and Deca 850 MB/s over two cables. There are no packets in the path; the grabber reconstructs the image from raw taps, so width, height, bit depth and tap layout must match on both ends. The Camera Link compatibility checklist lists exactly what must agree.

CoaXPress aggregates coax inside one connector, and payload scales with link count: two CXP-6 links carry 1.25 GB/s, six reach 3.6 GB/s. USB3 Vision moves frames by direct memory access into host buffers, which is why its over-400 MB/s behaves like a grabber link; when a camera demands more than the port gives, cut pixels or bits before cutting frame rate - the per-camera USB3 budget math shows the levers. GigE Vision sits on Ethernet's 1 Gbit/s, so several cameras divide one budget: the multi-camera GigE bandwidth budget works that division, and the GigE Vision camera selection guide continues into cable grades and software.

Everything downstream is division. Size the pixel count first, then divide by the pipe:

Cable reach

Length buys distance, never bandwidth. GigE Vision reaches 100 m on copper and 5,000 m on fiber while the pipe stays 1 Gbit/s; 10GigE changes the pipe, and the 5GBASE-T interface guide covers its cable grades and reach. USB3 Vision manages 3-5 m on a passive copper cable, 8 m or more with active cable, 100 m on fiber - plan the mount before the camera, as the USB cable length limits for 3D cameras show in practice.

Camera Link runs 7-15 m; the faster the camera clocks, the closer you plan to the 7 m end. CoaXPress trades reach against grade: over 100 m at CXP-1 (1.25 Gbit/s), 85 m at CXP-3 (3.125 Gbit/s), 35 m at CXP-6 (6.25 Gbit/s) on 6 mm coax, and larger-diameter coax stretches those numbers.

Stocked runs that match the three camera-side standards:

The high-flex GigE and USB3 cables suit drag chains and robot dress packs; the SDR-to-SDR Camera Link cable suits a fixed frame.

Power and trigger over the same cable

GigE cameras take PoE from the port or an external supply; a dual-port PoE NIC such as the MV-GE2002P feeds cameras from the host. USB3 Vision carries up to 4.5 W (5 V bus) over the passive cable - enough for compact area scan cameras, not for large boards. Camera Link's PoCL powers the camera through the link from a PoCL grabber, with PoCL-Lite covering Base only. CoaXPress is the strongest: up to 13 W per coax at 24 V, enough for power-hungry sensors without a local supply.

Triggers differ more than power does. CoaXPress sends triggers down its 20.8 Mbit/s uplink with 3.4 µs latency, or about 150 ns with the optional high-speed uplink - tight enough to pace a line scan camera. Camera Link's CC1-CC4 lines are hardware signals on the cable with no packetisation in the path. GigE Vision synchronises capture across cameras with IEEE 1588 PTP. USB3 transfer timing is host-scheduled, so treat it as the option where loose trigger timing is invisible to the inspection.

Worked example: one 12 MP sensor, two interfaces

The LS-CMR-0053 and the LS-CMR-0166 carry the same IMX226 sensor at 12 MP, one on GigE, one on USB3 - and the interface sets each camera's frame rate.

The GigE camera ships the sensor at 9 fps. The pixel array is 4000 × 3000, so an 8-bit frame is 4000 × 3000 px × 1 B = 12 MB. The gigabit budget divides it: 110 MB/s ÷ 12 MB ≈ 9 fps. The camera sits at the port's ceiling, not the sensor's.

The USB3 camera ships the same sensor at 30 fps. The same frame at 30 fps demands 12 MB × 30 = 360 MB/s, inside the over-400 MB/s a USB3 Vision port sustains with about 10% to spare. On CoaXPress, one CXP-6 coax (625 MB/s payload) would carry it at 625 ÷ 12 ≈ 52 fps, and extra links multiply from there.

Same sensor, different pipe: gigabit caps the frame rate, USB3 releases it. If the inspection needs 30 fps at 12 MP, USB3 Vision is the short-cable answer; stretch the run past 5 m and GigE drops you back toward single digits.

Frame grabber or straight into the PC

USB3 Vision and GigE Vision terminate in the PC: a motherboard port or NIC receives them, and most single-camera hosts need no card at all. Add cards when cameras outnumber ports, when a camera needs PoE, or when camera traffic should be isolated from the plant network.

Camera Link and CoaXPress always land in a frame grabber; the card times the acquisition, reads the camera's configuration file and drives the trigger lines. One card per pipe, where a pipe needs one:

The Camera Link card covers the legacy estate, the octo CXP-6 card aggregates eight coax links, the 4-port GigE card isolates four cameras, and the dual 10GigE card carries the high-resolution traffic. Compare the full range in the frame grabbers or the accessories finder. Two integration points decide reliability: the grabber's firmware and your SDK must agree on the camera's mode of operation, which the frame grabber image acquisition guide for Camera Link and CoaXPress walks through, and port-to-camera mapping must survive reboots - the camera-to-port assignment guide covers that.

Match link grades before ordering: camera and grabber negotiate to the lower grade, so a CXP-12-graded camera on CXP-6-only links runs at 6.25 Gbit/s per link, and the aggregate falls with it.

How to choose: the ceilings per frame size

Columns use each pipe's usable payload from the at-a-glance table; the sensor's own readout rate limits first, so treat these as ceilings. Camera Link Base divides the Deca column by 3.3. CoaXPress columns scale with link count: 4 links × 625 MB/s = 2.5 GB/s.

• Conveyor inspection at 12 MP and 30 fps under 5 m: USB3 Vision, as the worked example shows.
• The same data over a 30 m gantry, or eight cameras on one line: GigE Vision, one camera per port; step to 10GigE when one camera exceeds one gigabit.
• 50 MP sensors, line scan, or anything above about 350 MB/s per camera: CoaXPress, links aggregated to taste and triggers paced off the 3.4 µs uplink. USB3's over-400 MB/s leaves under 15% margin there, and no growth room.
• A Camera Link machine that already works: keep it, and shortlist replacements in the camera finder by sensor rather than interface.

Checks before you order

• Run the division. Frame size in MB times frame rate in fps, against the pipe's usable rate, keeping about 20% margin so peak demand never touches the ceiling.
• Measure the cable path. Drag-chain routing turns a 10 m straight line into 15 m of cable; hold the run inside the standard's limit at your grade.
• Budget the power. PoE per port for GigE, 4.5 W for USB3, PoCL pairing for Camera Link, 13 W per coax for CoaXPress.
• Plan the host. A Camera Link or CoaXPress grabber needs a free PCIe slot; laptops rarely have one, so walk the whole chain with the laptop frame grabber compatibility guide.
• Feed the host. On packet-based links an under-tuned host shows up as overflow rather than a dead link; the GigE camera buffer overflow walkthrough covers the host-side checks.
• Set the trigger plan. CC lines, CXP uplink latency, or PTP synchronisation - and one shared pulse source where cameras must align.
• Order one spare cable of each type. Cables fail before cameras do, and a failed specialty cable stops the line.

When the usual answer is wrong

• USB3 is plug and play. Until a hub joins: hubs renegotiate links and drop camera frame rates, as the USB hub frame rate troubleshooting guide shows, and several USB cameras share port power and bandwidth per the multi-camera USB budget guide.
• GigE runs anywhere Ethernet does. A link that falls back below gigabit starts throwing packet size errors; the GigE packet size error fix shows the symptom and the setting.
• Camera Link is finished. Existing lines keep running it well; the integration questions that decide a migration are the same ones behind why adapters fail for an analog camera on a Camera Link frame grabber.
• The rated grade is guaranteed. Only after negotiation: the lower of camera and grabber grade wins, so budget on the lower number.

Start the build at the camera configurator, filter area scan cameras by the interface the arithmetic picked, then match cables to the measured run. If the bandwidth math and the cable path disagree, send both numbers through the contact page and we will size the link with you.