Desk Lamp with Adjustable Light-Emitting Angle via Sliding Prism Sheet

The problem

Modern desk lamps are trending toward thinner, lighter designs. However, achieving uniform brightness in a slim profile is difficult. Traditional solutions place LEDs around the perimeter and use a light guide plate to distribute light inward. This often results in uneven brightness, with hotspots near the edge and dimmer areas in the center, causing glare and visual fatigue. Some designs add a prism sheet at the very front to concentrate light, but this fixes the emission angle. If the angle is too wide, light spills onto adjacent furniture or wakes up sleeping family members. If it is too narrow, the usable workspace is limited. There is a need for a mechanism that allows the light-emitting angle to be adjusted after assembly or during use, without adding significant bulk.

The solution

The patented lamp uses a multi-layer optical stack housed within a slim lamp cap. The core innovation is the placement and movement of the prism sheet. Instead of being fixed at the outermost surface, the prism sheet is positioned between the light guide plate and the diffusion film. It is slidably connected, meaning its distance from the diffusion film can be changed.

The prism sheet itself has a first light-emitting surface with multiple adjacent grooves. These grooves have inclined surrounding side surfaces and bottom surfaces. Crucially, the side surfaces are arc-shaped curved surfaces. The geometry is defined by an initial included angle a (between 135° and 175°), a curvature radius R, and a distance L between the prism and the diffusion film. The relationship follows the formula $R = \pi \cdot L / k$ (where k is a constant). By sliding the prism sheet to change L, the refraction path of the light rays is altered, allowing the final output angle to be tuned.

Who it is for

• Consumer Electronics Brands: Companies launching premium, thin-profile desk lamps that differentiate through superior optical control and reduced glare.
• Amazon Sellers: Private label brands looking for unique selling points like “adjustable beam angle” to compete against standard fixed-angle lamps.
• Office Furniture Manufacturers: Suppliers needing integrated task lighting that can be calibrated for different desk depths and ambient conditions.
• Educational Product Makers: Creators of study lamps for children, where controlling spill light to avoid disturbing siblings or parents is a key feature.

How it works

The main parts

Operating steps

1. Light Generation: The annular LED belt emits light radially inward toward the cylindrical light guide plate.
2. Guidance: The light guide plate captures the light and directs it outward. The reflecting film ensures no light is lost backward.
3. Refraction Adjustment: The prism sheet is positioned at a specific distance L from the diffusion film. As light passes through the arc-shaped grooves of the prism, it is refracted.
4. Angle Control: Changing the position of the prism sheet alters the effective refraction angle. A smaller gap may widen the beam; a larger gap may narrow it (depending on specific tuning).
5. Diffusion: The light exits through the diffusion film, creating a uniform glow with the selected angular spread.

Applications

Nighttime Study Areas

Students studying late at night benefit from a narrower beam angle that illuminates their book without casting bright reflections on walls or waking up a roommate sharing the room.

Shared Workspaces

In open-plan offices or home desks shared by two people, adjustable angles allow one user to focus light strictly on their monitor or documents, minimizing glare for the person sitting next to them.

Reading Nooks

For bedside reading, the lamp can be set to a wider, softer angle that fills the immediate area without harsh shadows, reducing eye strain during long reading sessions.

Product Photography Staging

Small-scale photographers using desk lamps for product shots can adjust the light spread to create specific shadow effects or even illumination on small objects, offering more control than fixed-angle bulbs.

Where it is less suitable

• High-Bay Industrial Lighting: This design is optimized for close-range task lighting; it lacks the intensity and throw required for large warehouse spaces.
• Outdoor Weatherproof Use: The patent describes an indoor desk lamp structure; it does not specify sealing methods for rain or dust resistance typical of outdoor fixtures.
• Fixed-Angle Commercial Installations: In retail displays where light direction never changes, the added mechanical complexity of the sliding prism may increase cost unnecessarily compared to static optics.