ABOUT NOCTVISION
Recording, in numbers, where optics, lighting, and hardware get entangled
NOCTVISION is a technical record site covering machine vision and edge AI. This site organizes the problems encountered when building vision systems in industrial settings — the points where optics, lighting, and hardware are entangled in ways that algorithms alone can’t resolve.
Three principles
- Optics Is PhysicsThe first step in system design is the lens and the lighting. This site covers physical quantities and formulas that can be verified — focal length, aperture value, depth of field.
- Only Verified MaterialCode that hasn’t been confirmed to work isn’t posted. Code includes comments on the core logic and the related physical formulas so a reader can reproduce it.
- Edge Environments Are the BaselineThe standard is what actually runs on an edge board, not the ample resources of a PC. Results are presented as numbers — processing speed, inspection resolution, accuracy.
Browse by topic
OPTICS41 posts
Optics
This section covers the values that are settled by calculation first: the size of one pixel on the object, working distance (WD) and depth of field. How many pixels a defect occupies on screen is decided by these numbers before any algorithm runs.Start with theseHow to Calculate Machine-Vision Lens Focal Length — the basic formula from FOV, WD and sensor sizeMachine Vision Lens Calculator — where the shortcut formula breaks at higher magnification, plus depth of field and diffractionVision Types Split First by Wavelength and Pixel Size — several vision methods compared in one tableIn SWIR, One Stop Down Erases a 3.4 µm Pixel — how diffraction covers a pixel as wavelength growsUnfamiliar terms are explained in the Glossary, and a reading order across topics is in the Start Here guide.
LIGHTING29 posts
Lighting Design
With the same camera, a defect can appear or vanish depending on the angle and wavelength of the light. This section collects articles on choosing among coaxial, dome, dark-field and backlight methods, and on handling reflection, wavelength and brightness drift.Start with theseSix Machine-Vision Lighting Methods and How to Choose — how each method works and the order for choosingFor Scratches on Highly Reflective Metal, Choose the Lighting First — a lighting map by surface typeWhy a Black Spot Remains in the Center of a Dome Light — the viewing-hole dark spot and fill lightWhen the Light Dims by 5 %, How Many Good Pixels Turn Into Defects? — how brightness change affects decisionsUnfamiliar terms are explained in the Glossary, and a reading order across topics is in the Start Here guide.
Start hereSix Machine-Vision Lighting Methods and How to Choose
ALGORITHM39 posts
Vision Algorithm
This section covers the rules and models that pick defects out of an image, and the cost when a decision is wrong: how rule-based and deep-learning methods share the work, anomaly detection, and filter order. It is the stage that turns the image made by lighting and optics into a pass/fail decision.Start with theseDeep Learning vs. Rule-Based Algorithms, When to Use Which — the conditions that favor eachOverdetection or Missed Detection, Which One Costs More? — setting the decision line by costBuilding a Vision Inspection App with PySide6 and OpenCV — full code for a minimal UI that tunes parameters on screenMust Every Normal Patch Be Remembered? — coreset design for memory-bank anomaly detectionUnfamiliar terms are explained in the Glossary, and a reading order across topics is in the Start Here guide.
Start hereDeep Learning vs. Rule-Based Algorithms, When to Use Which
EDGE AI22 posts
Edge AI
This section covers what goes wrong when an inspection model runs on a small board next to the machine instead of a server: accuracy lost to quantization, latency added by heat, and throughput set by the camera interface. These are items to confirm with numbers on site.Start with theseFour Snags in Initial Jetson Orin Nano Setup — a check order for first power-onIt Worked on the Server, So Why Does Accuracy Drop on the Edge? — the order for finding accuracy lossIs It Safe When the Average Latency Fits? — splitting the latency budget by p99Why Edge AI Vision Fails on the Factory Floor — a troubleshooting map from symptom to causeUnfamiliar terms are explained in the Glossary, and a reading order across topics is in the Start Here guide.
Start hereIt Worked on the Server, So Why Does Accuracy Drop on the Edge?
Latest posts
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A Light Field Camera Trades Pixels for Depth
A light field camera bundles the pixels behind each microlens into one point. At 2x on a 25 μm gold wire, no bundle size keeps both the wire and the loop.
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Raising the Camera Leaves the Glint of Its Built-in Light in Place
A camera's built-in light puts a hotspot on a glossy cover at half the LED offset, and raising the camera won't move it. A 12 mm lens must tilt 10.8° to clear it.
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How Much Closer Does a CIS Sit Than a Line Scan Camera?
For the same 300 mm field, area scan needs a 555.7 mm WD and line scan 416.2 mm, but a CIS reads from 10 to 20 mm. One 900 dpi line then passes…
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A Board at 0.5 m/s Leans 15 mm Under a Rolling Shutter
On the same 100 mm board, a rolling shutter shifts the top and bottom rows 15 mm, and a global shutter at a 100 μs exposure still smears 50 μm. In color, a…
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Vision Types Split First by Wavelength and Pixel Size
On the same 100 mm PCB, only area and line scan give a 50 μm defect two pixels or more. LWIR blurs it at 48.8 μm, and 3D heights split into 4.9 μm…
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When the Light Dims by 5 %, How Many Good Pixels Turn Into Defects?
With the decision line fixed, a 5 % drop in lamp output turns 19 % of good pixels into defects. This traces how anomaly detection scores slip under lighting change and what a…
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In SWIR, One Stop Down Erases a 3.4 μm Pixel
At 1800 nm a fully open f/2.8 leaves only 15% contrast on a 3.4 μm pixel, and one stop down takes it to zero. Work out the cost of stopping down from wavelength,…
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A Depth Camera’s Error Grows with the Square of Distance
A 50 mm baseline stereo depth camera wobbles by 0.6 mm at 40 cm. Seeing a 0.5 mm lift on a board needs it within 21 cm, and it cannot measure closer than…
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Why Do Shiny Parts Look Cold to a Thermal Camera?
A 70 °C aluminum capacitor reads 30.6 °C on a thermal camera and a 90 °C chip reads 75 °C. One reflects the room; the other shares a pixel with the board.
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A Machine Vision Lens Calculator That Catches the FOV Error a Shortcut Formula Misses
At magnification 0.141 the shortcut reports a 4,096 px setup's FOV 14% too wide. A 25 mm lens reaches 100 mm only at 202 mm, and the 3.15 mm depth opened at F8…