Optical device and prism module thereof

A prism module, comprising:

• a first prism comprising a first surface, a second surface and a third surface wherein the first surface adjoins the second surface, and the third surface is disposed opposite to an included angle between the first surface and the second surface;
• a second prism comprising a fourth surface, a fifth surface and a sixth surface wherein the fourth surface adjoins both of the fifth surface and the sixth surface and is disposed towards the second surface of the first prism;
• a third prism comprising a seventh surface, an eighth surface and a ninth surface, wherein the seventh surface is disposed towards the sixth surface of the second prism, and the ninth surface adjoins both of the seventh surface and the eighth surface;
• a first film adjoins the fifth surface;
• wherein invisible light enters the third prism through the ninth surface, is reflected on the eighth surface, passes through the seventh surface, enters the second prism through the sixth surface, is reflected on the fifth surface, exits from the fourth surface of the second prism, enters the first prism through the second surface, is sequentially reflected on the first surface, the third surface and the second surface of the first prism, and exits from the first surface of the first prism;
• wherein the first film reflects the invisible light.

A prism module, comprising:

• a first prism comprising a first surface, a second surface and a third surface wherein the first surface adjoins the second surface, and the third surface is disposed opposite to an included angle between the first surface and the second surface;
• a second prism comprising a fourth surface, a fifth surface and a sixth surface wherein the fourth surface adjoins both of the fifth surface and the sixth surface and is disposed towards the second surface of the first prism;
• a third prism comprising a seventh surface, an eighth surface and a ninth surface, wherein the seventh surface is disposed towards the sixth surface of the second prism, and the ninth surface adjoins both of the seventh surface and the eighth surface;
• a first film adjoins the fifth surface;
• wherein invisible light is reflected to the prism module by a target object, enters the first prism through the first surface, is sequentially reflected on the second surface, the third surface and the first surface, exits from the first prism through the second surface, enters the second prism through the fourth surface, is reflected on the fifth surface, sequentially passes through the sixth surface and the second film, enters the third prism through the seventh surface, is reflected on the eighth surface, and exits from the third prism through the ninth surface;
• wherein the first film reflects the invisible light.