Liquid crystal display with ambient light sensor

A liquid crystal display includes a main body, a screen positioned on the main body, a backlight module positioned in the main body and supplying light for the screen, a controller for controlling the brightness of the backlight module and an ambient light sensor positioned on the main body. The ambient light sensor includes a barrel, an optical sheet positioned at an end of the barrel and a photosensitive unit positioned at the other end of the barrel. The photosensitive unit creates a signal according to the ambient light received via the optical sheet, and sends the signal to the controller. The controller adjusts the brightness of the backlight module. The optical sheet includes a first surface, a second surface opposite the first surface and a plurality of V-shaped micro structures formed on the first surface.

BACKGROUND

1. Technical Field

The present disclosure relates to liquid crystal displays and, particularly, to a liquid crystal display with ambient light sensor.

2. Description of the Related Art

There may be situations when it is desirable to use an ambient light sensor in a liquid crystal display in an environment where there is a significant amount of ambient light (e.g., the outdoors on a bright, sunny day). In some circumstances, a significant amount of ambient light may negatively affect the accuracy of an optical ambient light sensor. A typical ambient light sensor employed in the liquid crystal display usually includes a transparent sheet for protection. However, the light from an ambient light source at a side of the ambient sensor with an incident angle greater than the critical angle may be totally reflected at the bottom surface of the transparent sheet. That is, most of the ambient light cannot be received by the ambient sensor, thereby decreasing sensitivity of the ambient sensor.

Therefore, there is room for improvement within the art.

DETAILED DESCRIPTION

Referring toFIGS. 1 and 2, an embodiment of a liquid crystal display100includes a main body21, a screen22, a backlight module23, a controller24and an ambient light sensor26. The main body21includes a top panel211, a bottom panel212facing the top panel211, and side walls213(only one shown) connecting the top panel211and the bottom panel212. The top and bottom panels211,212and the side walls213cooperatively define a receiving space214therebetween. The top panel211defines a first window215and a second window216each communicated with the receiving space214.

The screen22is positioned on the main body21and mounted in the first window215, and the backlight module23is positioned on the bottom panel212and located under the screen22in the main body21. The backlight module23supplies light to the screen22.

The ambient light sensor26is mounted to the main body21and includes an optical sheet261, a barrel263and a photosensitive unit265. The barrel263is sandwiched between the top panel211and the bottom panel212to face the second window216. The optical sheet261is positioned in the second window216to connect or contact an end of the barrel263. The photosensitive unit265is positioned on the second panel212and surrounded by the other end of the barrel263. The optical sheet261includes a first surface2611(shown inFIG. 3), a second surface2613opposite to the first surface2611, and a plurality of longitudinally parallel V-shaped micro structures2614formed on the first surface2611to protrude out from the top panel211. The second surface2613is flat. A vertex angle of the V-shaped micro structure2614is preferably in a range from greater than 0° to about 90°. In the illustrated embodiment, the vertex angle of the V-shaped micro structure2614is 45°. The barrel263is substantially a frustum of a cone, including a first end portion2631and a second end portion2633with a diameter less than that of the first end portion2631. The photosensitive unit265is mounted at the second end portion of the barrel263, the optical sheet261is mounted at the first end portion of the barrel263, and the V-shaped micro structure2614faces away from the photosensitive unit265.

The ambient light sensor26is positioned in the main body21adjacent to the screen22, with at least part of the optical sheet261exposed out of the main body21. The photosensitive unit265receives light via the optical sheet261, creates a signal based on brightness of the ambient light, and sends the signal to the controller24. The controller24increases or decreases an electrical current of the backlight module23based on the received signal to adjust the brightness of the backlight module23.

Referring toFIG. 3, each V-shaped micro structure2614includes a first incident surface2615angled relative to the first surface2611and a second incident surface2616adjacent to the first incident surface2615. The vertex angle θ is defined by the first incident surface2615and the second incident surface2616. Light rays α, β and γ are refracted by the V-shaped micro structure2614towards a normal direction of the first surface2611, and the incident angle of the light ray α, β and γ at the second surface2613is decreased, such that the internal reflection at the second surface2613is decreased. More light travels through optical sheet261. The brightness of the backlight module23is adjusted by the controller24simultaneously.

Referring to Table 1, shown below, three test samples are provided, a first test sample of the ambient light sensor is made using a flat transparent sheet positioned on the first end portion2631instead of the optical sheet261. The second test sample with ambient light sensor261with 10° vertex angle of V-shaped micro structure2614. The third test sample with ambient light sensor261with 20° vertex angle of V-shaped micro structure2614. Emitted light of predetermined incident angle travels through the three test samples, with the brightness (lumen) detected by the photosensitive unit265is also provided in each sheet of Table 1.

Table 1 shows that the second and the third test samples with optical sheet261receive more light than the first sample. The photosensitive unit265of the third test sample with optical sheet261having vertex angle θ exceeding that of the second test sample receives more light than the third test sample. That is, as angle θ increases, more light passing through the optical sheet261.

Finally, while particular embodiments have been described, the description is illustrative and is not to be construed as limiting. For example, various modifications can be made to the embodiments by those of ordinary skill in the art without departing from the true spirit and scope of the invention as defined by the appended claims.