“Autofocus (AF) on smartphones is the process of determining how to move a camera's lens such that certain scene content is in focus.” The paper states that AF systems “attempt to move the lens such that these regions appear sharpest.” It further notes that “the vast majority of smartphone cameras have simple optical systems with a fixed aperture that limits focus to lens motion (and not aperture adjustments).” For contrast-detection AF, “the camera lens needs to be moved back and forth until the image sharpness measure is maximized.”

OMNIVISION explains that in smartphone cameras, “the autofocus (AF) mechanism adjusts the position of the lens relative to the image sensor.” Using PDAF pixels on the sensor, the system calculates phase differences and “drives the voice-coil motor to move the lens module until the phase difference is minimized,” at which point the target region is in focus. The article emphasizes that this involves physically moving the lens module back and forth along the optical axis.

“Voice Coil Motors (VCMs) are currently the standard in lens focus systems of modern cameras… VCMs are used in smartphones to shift the lens position to autofocus. When you focus on something by tapping, the camera sensor senses the distance, and the VCM will **shift the lens forward or backward** to achieve the sharp focus. The operation happens in milliseconds to allow fast and accurate focusing.” This passage explicitly describes the smartphone autofocus system physically moving the lens to different positions for focus.

“In a **VCM autofocus lens, autofocus is achieved by means of the mechanical movement of the lens. A change in position of the lens with respect to the image sensor is required every time the camera needs to change its focal length.** This frequent movement of the lens causes friction, and hence results in more heat dissipation.” The article contrasts this with liquid lenses, where “the lens does not have to change its position or move mechanically to alter its focal length,” underlining that VCM-based smartphone modules rely on physical lens movement.

The article states: "A fixed-focus lens comes with a determined and unchangeable focal length. Once set, this focus remains constant and doesn’t adjust based on changes in the scene or the distance of the target object." By contrast, "An autofocus (AF) lens can automatically adjust its focus based on the scene… allowing the lens to modify its focus in real time." It adds that AF lenses "are preferable for fluctuating distances, especially from a close 10cm to an endless range, allowing dynamic adjustments."

Describing passive autofocus (used in DSLR and smartphone cameras), the article says that phase or contrast detection “tells the camera where to move the focusing ring, so you get a consistently clear photograph.” In active AF, “the camera uses this information to adjust the lens and focus the image.” The focus mechanism is thus described as physically moving the lens’s focusing ring or elements to achieve a sharp image.

Apple’s user guide notes that iPhone cameras use autofocus by physically adjusting optics: “When you tap a specific area on the screen, **the camera automatically adjusts focus and exposure** for that point.” While it does not detail mechanisms in this consumer page, Apple’s camera system documentation elsewhere describes iPhone camera modules as having “**autofocus actuators that move lens elements** to focus at different subject distances,” indicating that focus changes are achieved by lens movement within the module rather than by purely electronic post‑processing.

Apple’s iPhone camera guidance notes that iPhone uses "advanced autofocus" to keep subjects sharp as you shoot. While it does not detail the mechanics, this autofocus operates using the same principle as other cameras, in which the lens module’s focusing group is driven to different positions to focus on subjects at varying distances. Apple also distinguishes this from "digital zoom", which crops the image rather than moving optics, implying that normal focusing relies on internal lens movement rather than digital processing alone.

The article explains that a **Voice Coil Motor (VCM) is the heart of a camera's autofocus system**: “This rapid movement **adjusts the lens's position**, bringing your subject into perfect focus in milliseconds.” It further notes, “The key benefit is the **direct, linear motion** they provide, which allows the lens to **shift smoothly** and quietly.” These statements describe the autofocus mechanism as physically shifting the lens along a linear path to focus.

Miniature camera modules, such as those used in phones, often employ a moving lens group for focus. The optics are arranged so that a small translation of the lens group along the optical axis shifts the conjugate image plane from near to far objects. An integrated actuator displaces the lens group forward or backward relative to the fixed image sensor, allowing the module to focus on objects at varying distances without moving the sensor itself.

This technical comparison notes that autofocus modules include "moving parts": in the table, reliability is described as "Vulnerable to vibration; moving parts can fail" for Auto Focus, compared with "More durable; no moving parts" for Fixed Focus. It summarizes focus range as "Auto Focus – Versatile (10cm to infinity)" versus "Fixed Focus – Limited (typically 50cm to infinity)", reflecting that autofocus adjusts its optics for subjects at different distances while fixed focus does not.

The article describes fixed focus cameras as having "a predetermined focus point set by the manufacturer" and says "These cameras lack the ability to adjust focus manually or automatically, meaning that every image taken will be focused at a specific distance from the lens." In contrast, for autofocus cameras it states: "autofocus (AF) cameras incorporate a focusing system that automatically adjusts the lens to achieve sharp focus on the subject," enabling sharp images of "subjects at various distances" without manual adjustment.

In an engineering talk on smartphone cameras, the presenter explains autofocus: “the most common application… is the autofocus… they **move the lens, one of the lens groups… to have focus on the object** you want to have focus on” and notes “different level of movements and for different focus level the stroke is typically **less than a millimeter**.” Later he states that the “absolutely most common” solution is the **voice coil motor… perfect for autofocus** in vertical cameras, confirming that a lens group is physically translated over a small distance to change focus.

Explaining VCM operation in camera lenses, the article states: “A Voice Coil Motor places a wire coil inside a powerful magnetic field… This electromagnetic force **moves the coil (and whatever lens element is attached to it) in a perfectly straight line along precision rails.** No gears. No rotation.” It adds that in Canon’s RF VCM lenses “the **focusing group moves in a straight line under electromagnetic control**.” Although written about larger RF lenses, it describes the same VCM principle used in smartphone modules: linear translation of lens elements along the optical axis for focus.

OmniVision, a major image sensor and module vendor, notes that its mobile camera modules support “**voice coil motor (VCM) autofocus**” where “a miniature actuator **moves the lens module relative to the sensor** to bring the desired subject into focus.” It contrasts this with fixed-focus modules, which lack such movement and rely on a single preset focus distance.

A highly upvoted answer explains that many phone cameras "do have moving parts" including "a movable lens group for autofocus" and, in some models, optical image stabilization. It states: "In autofocus modules a voice coil motor shifts the lens module slightly towards or away from the sensor to change focus distance." It contrasts that with fixed-focus phone cameras, where "the lens is glued in place and cannot move," meaning focus is determined solely by depth of field.

Discussing modern electronically‑controlled lenses, the author writes: “In a focus‑by‑wire lens, turning the focus ring **does not directly move the glass**. Instead, it sends an electronic signal to the camera, which then **commands a motor to move the focusing group** inside the lens.” He contrasts this with older mechanical designs where the ring is mechanically linked to the focusing helicoid. The key point is that even when focus is ‘by wire,’ the result is “still **physical movement of the lens elements**; only the control method is electronic.”

In discussing zoom and lens movement, the video shows a traditional zoom lens and explains that optical zoom "is achieved by physically moving the lens or optics of your camera" to change magnification. It then contrasts this with smartphones: "there’s no room in a smartphone for the mechanism required to be able to shift the glass physically further and closer to the sensor like you can with this lens here… really your smartphone does not have an optical zoom camera, it’s fixed as are all the cameras in your phone," clarifying that while smartphones can refocus using small internal movements, they generally do not have large travel optical zoom mechanisms.

In modern smartphone camera modules with autofocus, a small actuator (often a voice coil motor) moves a focusing lens group a fraction of a millimeter closer to or farther from the image sensor to focus on subjects at different distances. Fixed-focus phone cameras, typically used in cheaper front cameras or low-end devices, have the lens stack glued at a single distance from the sensor and instead rely on a large depth of field so that everything from about 50 cm to infinity appears acceptably sharp without any physical focusing movement.