머신 비전의 자동 초점: 고정 초점, 전동식 M12 마운트 및 수동 초점 메커니즘
고정 초점과 자동 초점의 결정 기준, M12 렌즈의 구동을 담당하는 보이스 코일 및 피에조 하드웨어, 그리고 이 두 방식의 초점 작동 원리.
Autofocus in machine vision means an actuator moves the lens focus position during operation to keep the target sharp as working distance changes. The lens is a standard fixed-focal-length optic. The mechanism lives in a motorized mount or voice-coil actuator and in the host control loop.
작업 대상의 기하학적 구조가 안정적일 때는 ‘설정 및 고정(set-and-lock)’ 방식의 수동 초점이 더 나은 기본 설정입니다. 이는 통합이 더 간단하고 보정 상태를 유지하기 때문입니다. 자동 초점은 작업 중에 카메라와 대상 간의 거리가 사용 가능한 피사계 심도보다 더 많이 변하고, 광학 시스템만으로는 그 차이를 메울 수 없는 경우에만 지정해야 합니다.
머신 비전에서 자동 초점이란 무엇인가요?
Autofocus in machine vision means the system adjusts the lens focus position during operation to keep a target sharp as the camera-to-target distance changes. A motorized mount or voice-coil actuator moves a standard fixed-focal-length M12 lens along the optical axis, so the mechanism lives in the mount and its control electronics, not in the glass.
A consumer camera integrates sensing, actuator, and search in one body. A machine vision camera splits those apart, keeping the lens passive while the host decides when and where to move it. Autofocus here is a system-design decision, not a lens purchase. Focus changes where the lens is sharpest, not its focal length, so reframing between products needs a different focal length, not an actuator.
Systems land on one of three architectures: set-and-lock manual focus (the default for stable geometry), motorized refocus at changeover, and continuous autofocus per part or per frame. Each step up adds hardware and failure modes, so the framework below starts from the simplest. Commonlands supplies all three: focus lock rings, and the CLA321 and CLA322 M12 mounts. The hands-on bench procedure is in the guide on how to focus a camera.
고정 초점 대 자동 초점: 머신 비전 시스템에는 어떤 것이 필요할까요?
Fixed focus, set once at installation and locked, is the correct default for stable working geometry. Specify autofocus only when the working distance changes during operation by more than the available depth of field, and when a shorter focal length or a smaller aperture cannot cover the variation.
The comparison reads as fixed focus lens vs autofocus lens, but in machine vision it is two architectures built around the same passive optic: a locked M12 lens and one in a motorized mount can be the identical part number, differing only in whether anything moves it after bring-up.
Fixed focus is not fixed focal length. Fixed focal length describes the optics: one focal length, one angle of view, no zoom. Fixed focus describes the strategy: the lens is set to one distance and locked. Most M12 machine vision lenses are fixed focal length with adjustable focus, so the same lens ships locked or motorized.
잠긴 렌즈가 보정 상태를 유지하는 이유
A locked lens fixes the lens-to-sensor distance, which sets the intrinsic parameters (focal length in pixels and principal point) that pixel-to-world calibration depends on. Dimension gauging, position detection, and code reading assume those stay put, and an autofocus move changes them. A system that must measure across a focus range has to recalibrate after each move, qualify a tolerance window, or command only positions calibrated at bring-up, which is why calibration-critical systems default to set-and-lock.
하드웨어를 구매하기 전에 피사계 심도를 확인하세요
Depth of field is the no-moving-parts alternative. On a C-mount lens with an adjustable iris, stopping down trades light for a wider sharp zone. Commonlands M12 lenses have fixed apertures, so their depth of field is set by F-number, focal length, and working distance. That is why autofocus questions come up more often on M12 systems. Run the range through the depth of field calculator before specifying an actuator. If it covers the variation, lock the lens. The depth of field guide covers the underlying math.
Depth of field shrinks as focal length grows, so telephoto systems reach the threshold sooner. A 35mm telephoto such as the CIL350 holds a much thinner sharp zone than a 12mm lens like the CIL122 at the same distance, because depth of field scales roughly with the square of the focal length ratio. A shorter lens and a revised standoff often remove the need for an actuator entirely. The working distance guide and the depth of field calculator quantify each case.
초점 허용 오차 범위의 양 끝단에 위치한 M12 렌즈
임베디드 비전 분야에서 콘트라스트 검출 방식과 위상 검출 방식의 자동 초점 기능은 어떻게 작동하나요?
Contrast-detect autofocus steps the lens while maximizing an image sharpness metric. It works with any sensor but needs several frames to find the peak. Phase-detect autofocus samples opposite sides of the aperture on dedicated pixels and reads defocus direction and magnitude in one frame, but only on sensors that include those pixels.
A contrast-detect loop computes a focus score, typically gradient energy or Laplacian variance, moves the actuator one step, and compares. It cannot tell it passed the peak until the score falls, so the search overshoots and returns. Budget five to twenty frames per refocus. Machine vision is friendlier than consumer photography, since controlled illumination, high-contrast targets, and a bounded distance range shorten the search. This is the sensing approach behind most embedded systems that drive mounts like the CLA321 and CLA322.
Phase-detect pixels split light from opposite sides of the exit pupil. The disparity gives the distance and direction to best focus, so the controller commands one directed move. The catch is sensor support: mobile-derived rolling-shutter sensors often include these pixels, while many industrial global-shutter sensors do not, so verify support in the image sensor datasheet. A third path skips image feedback: when the target distance is known from an encoder or a time-of-flight sensor, the host commands a position from a bring-up lookup table.
두 Commonlands 자동 초점 마운트 모두 초점 탐색 컨트롤러를 내장하고 있지 않습니다. 호스트가 루프를 제어합니다. 호스트는 선명도를 평가하거나 거리를 측정한 후, USB-C(CLA322) 또는 구동 전류(CLA321)를 통해 액추에이터에 명령을 내립니다. 사이클 시간을 계획할 때는 탐색을 위한 호스트 처리 및 프레임 획득에 소요되는 시간을 고려하십시오.
M12 자동 초점 기능은 어떻게 작동하나요? 보이스 코일 대 피에조 마운트
M12 autofocus adds an actuator that moves a standard M12x0.5 threaded lens along the optical axis. The lens is unchanged. The CLA321 voice-coil mount positions the lens with drive current and needs continuous power to hold, dropping to rest on power loss, carrying lenses up to 7g on 23.5mm hole spacing. The CLA322 piezoelectric ultrasonic mount walks a friction-coupled, non-back-drivable stage in sub-micron steps, holds position unpowered, and reaches a 6.5mm stroke. A fixed-focus lens locked with a ring is the third option and the default whenever geometry is stable.
Liquid lenses: refocus with no stroke at all
A liquid lens changes optical power instead of position. Corning Varioptic drives an electrowetting cell whose water-oil interface reshapes with applied voltage. Optotune deflects a polymer membrane over a fluid reservoir. Neither translates a lens group, so refocus takes milliseconds with no sliding surfaces to wear, which is why fixed-mount barcode readers that see many package heights favor them. Commonlands sells neither. Both are the usual answer when a mechanical mount cannot keep up.
| 속성 | CLA321-VCM | CLA322-AFM |
|---|---|---|
| 구동 | 보이스 코일 모터, 스프링 복원력에 대항하는 전류 | 압전 초음파 선형 액추에이터, 마찰 결합형 스테이지 |
| 정격 스트로크 | 5g 렌즈 사용 시 100mA에서 ≥0.6mm | 6.5mm |
| 전원이 꺼진 상태에서도 위치를 유지합니다 | 아니요; 연속 전류가 필요합니다. | 네, 마찰 결합은 역구동이 불가능합니다. |
| 정전 시 | 봄철 휴식 위치로 돌아갑니다 | 마지막으로 지정된 위치를 유지합니다 |
| 제어 인터페이스 | 표준 VCM 전류 구동기 | 분리형 어댑터 보드를 통한 USB-C |
| 렌즈 호환성 | 최대 7g의 M12x0.5 렌즈 | 최대 5g의 M12x0.5 렌즈 |
| 가격 | $29.00 | $199.00 |
마운트를 선택하기 전에 획의 크기를 조정하세요
Required travel grows with the square of the focal length and falls roughly as 1/WD, so short lenses need microns and long lenses at close range need millimeters. It follows from first-order Gaussian optics: for a unit-focusing lens, one that moves as a rigid assembly, the travel from infinity focus to a working distance WD is approximately:
A 12mm lens focused from infinity to 200mm needs 12² / (200 − 12) = 0.77mm of travel, which exceeds the CLA321's 0.6mm rated stroke. Few systems refocus from infinity, though: the same lens moving between 300mm and 700mm needs only about 0.29mm, inside the CLA321 stroke. Run the between-distances form across the real working range before selecting the mount. The stroke budget, not the control interface, is usually the binding constraint. The table below extends the calculation and shows which mount covers each case.
| Focal length f | 여행, WD 200mm까지 무한대 | 이동 범위, WD 1000mm까지 무한대 | 무한대에서부터 그것을 덮는 산 |
|---|---|---|---|
| 6mm | 0.19mm | 0.04mm | CLA321 또는 CLA322 |
| 12mm | 0.77mm | 0.15mm | CLA322: 200mm; CLA321: 1000mm |
| 25mm | 3.57mm | 0.64mm | CLA322 |
| 35mm | 7.42mm | 1.27mm | CLA322, 1000mm; 200mm에서 무한대 모두 아님 |
M12 자동 초점 마운트
Commonlands stocks M12 lens variants in the US, and standard M12x0.5 lenses thread into either mount within its rated payload (7g for the CLA321, 5g for the CLA322). Inside that limit, lens selection and focus architecture are decided independently. Browse the M12 lens collection for the optics and the lens autofocus motors for both mounts.
수동 초점 렌즈란 무엇인가요?
A manual focus lens is one whose focus position a person sets at installation, by threading an M12 lens in its holder or turning a C-mount focus ring, then locks. After locking it behaves as a fixed-focus optic, but the engineer chose the distance to match the installed geometry, and the lock can be released and reset if that geometry changes.
M12 초점 작동 원리: 나사산이 초점 조절 장치 역할을 합니다
A standard M12 lens is a rigid optical assembly. Nothing moves inside it. Focus comes from the M12x0.5 mount thread: one full turn moves the whole lens 0.5mm along the axis, so a quarter turn gives 0.125mm, fine enough for bring-up by hand. Threading toward the sensor pushes best focus farther away. Backing it out pulls focus closer. The M12 lens guide covers holder heights and thread engagement.
A C-mount lens is different: an internal cam translates lens groups to rebalance aberrations across the focus range (Kingslake, Lens Design Fundamentals, 2nd ed., §18.3), so it moves glass inside a stationary barrel rather than as one rigid body. Factory fixed-focus modules are a third case, set at manufacture and not user-adjustable, suited to high-volume products with one known geometry. The C-mount guide covers the mount standard and iris options.
Locking is not optional. Vibration and thermal cycling can loosen an unlocked lens, letting it rotate and drift out of focus. A Commonlands AL6061 lock nut ring tightened against the holder face holds the position, and a low out-gassing thread adhesive adds margin in high-vibration installations.
자주 묻는 질문
머신 비전에서 고정 초점과 자동 초점의 차이점은 무엇인가요?
Fixed focus means the lens is set to one working distance at installation and locked. It does not change during operation. Autofocus means an actuator adjusts the lens focus position during operation as working distance changes. Fixed focus has fewer failure modes and holds calibration. Autofocus earns its complexity only when distance variation exceeds the depth of field.
M12 자동 초점이란 무엇인가요?
M12 autofocus is a system, not a lens category. An actuator, either a voice-coil mount like the CLA321 or a piezoelectric ultrasonic mount like the CLA322, moves a standard M12x0.5 threaded lens along the optical axis. The autofocus mechanism lives in the mount and its control electronics. The lens itself is a passive fixed-focal-length optic.
수동 초점 렌즈란 무엇인가요?
A manual focus lens is a lens whose focus position is set by a person during setup rather than by an actuator during operation. In machine vision, the engineer threads an M12 lens in its holder or turns a C-mount focus ring until the image is sharpest at the working distance. Then the engineer locks the position.
머신 비전에서 자동 초점 기능은 언제 사용하는 것이 좋을까요?
작동 중 작업 거리가 허용되는 피사계 심도보다 더 많이 변동하거나, 더 짧은 초점 거리나 조리개를 조이는 것만으로는 해당 범위를 커버할 수 없는 경우에는 자동 초점을 사용하는 것이 좋습니다. 대표적인 사례로는 높이가 다양한 컨베이어 부품, 팔에 장착된 로봇 카메라, 그리고 다양한 규격의 제품이 생산되는 라인 등이 있습니다.
자동 초점 기능이 피사계 심도 문제를 해결해 주나요?
No. Autofocus moves the focus plane to track the target. It does not increase depth of field. Evaluate optics first: a C-mount lens stopped down from F/2 to F/8 gains roughly four times the depth of field. Specify autofocus when aperture and focal length choices alone cannot cover the working distance range.
보이스 코일과 피에조 자동 초점 마운트의 차이점은 무엇인가요?
The Commonlands CLA321 voice-coil mount positions the lens with drive current against a spring return and needs continuous power to hold position. Rated stroke is 0.6mm or more at 100mA with a 5g lens. A piezoelectric ultrasonic mount like the CLA322 steps a friction-coupled stage across 6.5mm and holds position with power removed.
머신 비전도 일반 소비자용 카메라처럼 위상차 자동 초점 방식을 사용하나요?
일반 소비자용 제품에서는 거의 찾아보기 어렵습니다. 위상차 자동 초점 기능은 조리개의 양쪽을 샘플링하는 센서 픽셀이 필요하지만, 많은 산업용 글로벌 셔터 센서에서는 이러한 픽셀을 생략하고 있습니다. 임베디드 시스템의 경우, 호스트에서 콘트라스트 감지 방식의 선명도 검색을 수행하거나, 알려진 거리나 측정된 목표 거리를 기준으로 오픈 루프 방식으로 초점을 조정하는 경우가 더 많습니다.
적합한 아키텍처를 선택하는 데 도움이 필요하신가요?
Send your working distance range, sensor, cycle time, and format count to the engineering team, or request CLA321 and CLA322 samples to prototype the focus loop. Commonlands orders placed before 12 PM PST typically ship same day from San Diego.