Abstract: An optical module is disclosed, including a projection light source, a first optical waveguide, and a second optical waveguide. The projection light source is configured to provide a target image. The first optical waveguide has a plurality of first gratings. The plurality of first gratings are arranged at a distance of a first period. The second optical waveguide has a plurality of second gratings. The plurality of second gratings are arranged at a distance of a second period. An absolute value of a difference between the first period and the second period is greater than 0 and less than or equal to one tenth of a wavelength of the target image.

Abstract: A light-transmitting device includes a waveguide and first, second, and third grating regions. The first grating region is located on a first or a second surface of waveguide and has a first grating structure. The first grating structure allows a light to enter the waveguide. The second grating region is located on the first surface and has a second grating structure. The second grating structure is receives the light from the first grating region and to redirect the light. The third grating region is located on the first surface and has a third grating structure. The third grating structure receives the light from the second grating region and allows the light to leave the waveguide. A height of the second grating structure and a height of the third grating structure are less than the one-tenth of a height of the first grating structure.

Abstract: A waveguide element includes a substrate and a grating structure. The grating structure is located on the substrate to form a light in-coupling area, a light out-coupling area and a light pupil expanding area, in which the light pupil expanding area optically couples the light in-coupling area and the light out-coupling area. The light pupil expanding area has at least two partitions, and an included angle ? is between a border of the partitions of the light pupil expanding area and a horizontal line. The included angle ? satisfies ? = tan - 1 ( ? 1 ? 1 ) , in which ?1=(?? sin ?+?d)/nd, ?1=(? cos ?+?d)/nd, ?=sin(?)×cos ?, ?=sin(?)×sin ?, ? is a wavelength of an incident light, ? is a field of view, n is a refractive index of the substrate, ? is a grating vector direction of the light in-coupling area, and d is a grating periodic distance of the light in-coupling area.

Abstract: An explosion-proof filter cartridge, that includes: a filter bottle, a filter nozzle, a filter cartridge, and a plurality of elastic balloons. The filter nozzle is disposed on an upper end of the filter bottle, the filter cartridge is disposed in the filter bottle. The plurality of elastic balloons are disposed on an inner wall of the filter bottle. The distance between the two elastic balloons is less than a diameter of the elastic balloon. The plurality of elastic balloons are disposed and distributed evenly on the inner wall of the filter bottle, to prevent explosion of the filter bottle when water in the filter bottle is frozen to ice.

Abstract: a pre-filter device capable of preventing water leakage, that includes: a connector, a water inlet channel, a plug, and a spring. The connector is connected to a water inlet tube, and is connected to the pre-filter device. The water inlet channel is disposed in the connector, and is connected to the pre-filter device. The plug is disposed in the water inlet channel, to open or close the water inlet channel. The spring is disposed between one end of the plug and the connector, the other end of the plug is connected to and acts in cooperation with the pre-filter device. When a pre-filter device capable of preventing water leakage is burst to leak out water, it is able to close the water inlet channel automatically, to avoid the problem deteriorating into flooding the entire household, to achieve timely self protection.