CN106610529A - Fiber type beam distributed phase retarder and speckle removing method thereof - Google Patents

Abstract

The fiber-optic beam distributed phase retarder and its speckle elimination method relate to the light beam control optical fiber speckle elimination technology, which solves the problems of large structure and high production cost of existing devices for suppressing laser speckle. The speckle elimination method of the present invention is as follows: expand the laser beam emitted by the laser light source, pass through bundled optical fiber devices with different fiber lengths, and generate an optical path difference in the optical fiber. When the optical path difference is greater than or equal to the coherence length L _C of the laser, The beam is delayed in time, which destroys the coherence of the laser; according to the needs, set the diameter, spacing and quantity of each fiber in the bundled fiber device, expand the laser beam emitted by the laser source, and pass through the bundled fiber device with different fiber lengths. _A coherent laser beam is divided into multiple incoherent light sources. When the area of a single incoherent illumination source is greater than or equal to the coherent area AC, the coherence of the laser is spatially destroyed and the laser speckle is suppressed. The invention is used for high-power laser projection and laser illumination, and has the advantages of simple device structure, convenient assembly and low cost.

Description

Optical fiber beam distributed phase retarder and its speckle elimination method

technical field

The invention belongs to the technical field of light beam regulation optical fiber speckle elimination, and is especially used for laser projection and laser illumination; in particular, it relates to an optical fiber beam distributed phase retarder and a speckle elimination method thereof.

Background technique

When a coherent laser beam hits the surface of a rough object, light wave interference occurs between the light reflected or transmitted by the rough surface. What is shown is the granular point with uneven light intensity distribution, which is called speckle. In laser displays, the presence of speckle degrades image quality and must be suppressed.

At present, limited by the optical power of laser diodes, fiber-optic coupling is generally used in high-lumen laser displays to integrate multiple collimated red, green, and blue laser diodes through optical fiber bundles to achieve high-power light source illumination. CN10477626A discloses "a device and method for suppressing laser speckle and a laser display projection system". This patent application arranges sub-beams at the output end of the bundled optical fiber according to the diversification of speckle angles, independent speckle, superimposed in space Reduce speckle contrast. Because the patent application adopts the principle of angle diversity dispersing speckle, the laser beams that need to illuminate the screen are incident at different angles, which increases the etendue of the laser display system. Therefore, a large-aperture projection lens is required to collect laser light, which increases the display system. Production costs.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art, provide a fiber-optic beam distributed phase retarder and its speckle elimination method, and solve the technical problems of large structure and high manufacturing cost of existing devices for suppressing laser speckle.

The present invention is achieved through the following technical solutions:

A fiber-type beam distributed phase retarder, wherein: the beam distributed phase retarder is a bundled optical fiber device, and the bending of the optical fiber makes the optical path difference of the bundled optical fiber device greater than or equal to the coherence length L _C , destroying in time Laser coherence; the diameter, spacing and number of optical fibers are set so that a single beam of laser light is divided into multiple incoherent illumination sources. When the area of a single incoherent illumination source is greater than or equal to the coherence area A _C , the laser is spatially destroyed coherence.

Further, the specific structure of the bundled optical fiber device is as follows: the optical fibers are arranged continuously inside the molten glass rod, the glass optical fiber rod is heated and bent, the optical fibers in the glass optical fiber rod are correspondingly bent, and the length of the optical fiber near the inner ring is short, The surface of the glass fiber rod is polished or frosted.

A speckle elimination method of a fiber-optic beam distributed phase retarder, the steps of which are as follows:

Expand the laser beam emitted by the laser light source, and pass through the bundled optical fiber devices with different fiber lengths. The beam generates an optical path difference inside the fiber. When the optical path difference is greater than or equal to the coherence length L _C of the laser, the beam passing through each fiber is There is a certain delay in time, which destroys the coherence of the laser and suppresses the laser speckle; according to the needs, the diameter, spacing and quantity of the optical fibers in the bundled optical fiber device are set, and the laser beam emitted by the laser light source is expanded and passed through the optical fiber For the bundled optical fiber devices with different lengths, a single beam of coherent laser light is divided into multiple incoherent independent light sources. When the area of a single incoherent illumination light source is greater than or equal to the coherence area AC, the coherence of the laser light is spatially destroyed _. Suppresses laser speckle.

Compared with the prior art, the present invention does not require the laser beams to be incident in different directions by generating different phase delays for the spatial distribution of the laser beams, and therefore does not need to use a large-aperture projection lens, which can reduce the production cost of the display system.

The invention is used for high-power laser projection and laser illumination, and has the advantages of simple device structure, convenient assembly, low cost, good light transmittance, and suitable for mass production.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a schematic view of the end face structure of the present invention;

Fig. 3 is a schematic diagram of a rectangular ring bending structure of the present invention.

specific implementation plan

The technical solutions of the present invention will be clearly and completely described below through embodiments in conjunction with the accompanying drawings.

As shown in Figure 1, a fiber-optic beam distributed phase retarder uses a fused glass fiber rod with polished and frosted surfaces. The interior is a coherent arrangement of 2 optical fibers to transmit imaging. The molten glass optical fiber rod 1 becomes soft after being heated, and can change its orientation at will. By heating the molten glass fiber rod 1, the optical fiber 2 inside will be bent accordingly, and the length of the optical fiber 2 close to the inner annular ring will be shorter than that of the optical fiber 2 near the outer annular ring. When the light passes through the bent optical fiber 2, a certain optical path difference will be generated inside the optical fiber 2. When the optical path difference is greater than or equal to the coherence length L _C of the laser light, there will be a certain time difference between the light beams passing through each optical fiber 2. Delay, that is, destroys the coherence of the laser in time; and the setting of the diameter, spacing and quantity of each optical fiber 2 will divide a single laser beam into multiple incoherent illumination sources. When the area of a single incoherent illumination source is greater than or When it is equal to the coherent area _AC , the coherence of the laser is destroyed spatially. As a result, a distributed phase delay is generated to eliminate laser speckle in the time and space of the laser.

As shown in FIG. 2 , optical fibers 2 with a certain diameter, spacing and quantity are arranged in a light guide in a certain way.

As shown in Figure 3, as long as the optical path difference generated by the bent optical fiber 2 in the bundled optical fiber device is greater than or equal to the coherence length L _C , the distributed phase delay can be realized, so it is also possible to make a curved rectangular ring or other shapes .

As shown in Figures 1, 2, and 3, a speckle elimination method using a fiber-optic beam distributed phase retarder, the steps are: expand the laser beam emitted by the laser light source, and pass through the bundled optical fiber with different lengths of the optical fiber 2 When the optical path difference is greater than or equal to the coherence length L _C of the laser, the light beam passing through each optical fiber 2 will have a certain delay in time, which will destroy the coherence of the laser and inhibit the laser Speckle: set the diameter, spacing and quantity of each optical fiber 2 in the bundled optical fiber device as required, expand the laser beam emitted by the laser light source, and pass through the bundled optical fiber device with different lengths of the optical fibers 2, a single beam of coherent laser light is Divided into multiple incoherent independent light sources, when the area of a single incoherent illumination source is greater than or equal to the coherent area _AC , the coherence of the laser is spatially destroyed and the laser speckle is suppressed.

The present invention can be embodied in various forms without departing from the spirit and scope of the invention, and it should be understood that the above-described embodiments are not limited to the foregoing details, but should be construed broadly within the scope defined by the claims. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and changes within the equivalent range can also be made, and these improvements and changes should also be regarded as protection of the present invention. scope.

Claims (3)

1. a kind of optical-fiber type beam distribution formula phase delay device, it is characterised in that：The optical-fiber type beam distribution formula phase delay Device is a kind of bundling optical fiber device, and the bending of optical fiber causes the optical path difference of bundling optical fiber device to be more than or equal to coherence length L_C, The coherence that laser is destroyed on time；The setting of the diameter, spacing and quantity of optical fiber so that single beam laser is divided into multiple incoherent Lighting source, when the area of single incoherent illumination light source is more than or equal to coherent area A_CWhen, spatially destroy laser Coherence.

2. optical-fiber type beam distribution formula phase delay device according to claim 1, it is characterised in that：The bundling optical fiber device The concrete structure of part is：Link up arrangement optical fiber (2), glass optical fiber rod (1) plus thermal flexure inside fused glass rod, glass optical fiber Optical fiber (2) respective curved inside rod (1), the optical fiber (2) near inner ring is shorter than the length of the optical fiber (2) of close outer ring, glass Optical fibre rod (1) surface is burnishing surface or frosting.

3. a kind of speckle removing method of optical-fiber type beam distribution formula phase delay device, it is characterised in that：The speckle elimination side The step of method is：By the laser beam expanding of LASER Light Source outgoing, through the different bundling optical fiber device of fiber lengths, light beam exists Inside of optical fibre produces optical path difference, when optical path difference is more than or equal to coherence length L of laser_CWhen, through each optical fiber light beam when Between it is upper produce certain delay, destroy the coherence of laser, suppress laser speckle；As needed to the bundling optical fiber device The diameter of interior each optical fiber, spacing and quantity are configured, different through fiber lengths by the laser beam expanding of LASER Light Source outgoing The bundling optical fiber device, single beam coherent laser is divided into multiple noncoherent arbitrary sources, when single incoherent illumination light source Area be more than or equal to coherent area A_CWhen, the coherence of laser is spatially destroyed, suppress laser speckle.