TWI730243B - Structured-light projector - Google Patents

Abstract

A structured-light projector includes a diffractive optical element (DOE) that receives a collimated light and generates a plurality of light tiles. The DOE includes a plurality of optical components disposed on a substrate, wherein the light tiles are randomly arranged.

Description

Structured light projector

The present invention relates to a projector, in particular to a structured-light projector.

Small or micro optical projectors can be applied to various applications, such as projecting structured light patterns on objects for three-dimensional or depth mapping. In the three-dimensional mapping system, an image capturing device (such as a camera) is used to capture the image pattern projected on the object. After the captured image is processed, a three-dimensional image of the object can be constructed.

Traditional projectors have poor performance due to low decode rate. In addition, even if the advancement of optical manufacturing reduces the cost of miniaturization of the optical system, there is still considerable room for improvement in volume and/and cost of conventional projectors.

In view of the poor performance, bulkiness, or high price of traditional projectors, there is an urgent need to provide a novel structured light projector that can effectively improve performance or/and reduce volume or cost.

In view of the foregoing, one of the objectives of the embodiments of the present invention is to provide a structured light projector with improved performance or/and reduced volume or cost.

According to an embodiment of the present invention, a structured light projector includes a light source, a beam limiting device, and a diffractive optical element. The light source generates emitted light with a predetermined pattern. The beam limiting device receives the emitted light and generates collimated light. The diffractive optical element receives the collimated light and generates a plurality of light bricks. The diffractive optical element includes a plurality of optical components, and the light bricks are arranged randomly.

According to another embodiment of the present invention, a structured light projector includes a point light source, a beam limiting device, a patterning device, and a diffractive optical element. Point light sources produce emitted light. The beam limiting device receives the emitted light and generates collimated light. The patterning device receives the collimated light and generates patterned light. The diffractive optical element receives the pattern light and generates a plurality of light tiles. The diffractive optical element includes a plurality of optical components, and the light tiles are randomly arranged. According to another embodiment of the present invention, the diffractive optical element is located before the patterning device.

According to another embodiment of the present invention, a structured light projector includes a light source and a diffractive optical element. The light source generates emitted light with a predetermined pattern. The diffractive optical element receives the emitted light and generates a plurality of light bricks, which are arranged randomly or regularly.

FIG. 1A shows a block diagram of the structured light projector 100 of the first embodiment of the present invention, and FIG. 1B illustrates a schematic diagram of the structured light projector 100 of FIG. 1A. The structured light projector 100 is preferably a small optical projector, which is suitable for projecting a structured light pattern on an object for three-dimensional mapping.

In this embodiment, the structured light projector 100 may include a light source 11 that generates emitted light with a predetermined pattern. The emitted light may be visible light or/and invisible light (for example, infrared light). The light source 11 of this embodiment may include an array of semiconductor diodes arranged according to a preset pattern. In a preferred embodiment, the light source 11 may include a vertical-cavity surface-emitting laser (VCSEL) diode array, arranged on a substrate (not shown), and arranged according to a preset pattern . In this way, a vertical cavity surface-emitting laser (VCSEL) diode is used as the light source 11 to perform light emission and patterning at the same time. Vertical cavity surface emitting laser (VCSEL) diodes can be used to manufacture small and high-density light sources.

In one embodiment, the semiconductor diodes of the light source 11 can be sequentially lit, so that the power consumption is reduced, the decoding rate is increased, and/or the performance is improved in the near area. The second diagram A shows that part of the semiconductor diodes of the light source 11 are divided into two adjacent groups and sequentially lit. The second figure B shows that part of the semiconductor diodes of the light source 11 are divided into two intersecting groups and sequentially lit. The shape and size of the semiconductor diode of the light source 11 may be different from each other. The second figure C shows that part of the semiconductor diodes of the light source 11 are divided into two crossed groups according to their shapes and light up in sequence.

The structured light projector 100 of this embodiment may include a beam limiting device 12, which receives the emitted light (from the light source 11) and limits the cross section of the emitted light, thereby forming collimated light. In a preferred embodiment, the beam limiting device 12 may include a collimating lens, which may include a transparent material (such as plastic or glass), and may be manufactured using wafer level optics (WLO) technology. As illustrated in the first figure B (but not limited to this), the collimator lens (ie, the beam limiting device 12) is flat on one side (for example, the left side) facing the light source 11, and is on the other side (for example, the right side) Convex. Although the beam limiting device 12 illustrated in FIG. 1B includes a single lens, a plurality of lenses or multiple groups of lenses can also be used to construct the beam limiting device 12.

The structured light projector 100 of this embodiment may include a diffractive optical element (DOE) 13, which receives the collimated light (from the beam limiting device 12) and generates a plurality of light tiles. The light bricks are spaced from each other in a two-dimensional manner. As illustrated in FIG. 1B, the diffractive optical element 13 of this embodiment may include a plurality of optical components (for example, diffractive optical components) 131, which are disposed on the substrate 132. The optical component 131 may be provided on the side opposite to the beam limiting device 12 (for example, the right side). The diffractive optical element 13 may include a transparent material, such as plastic or glass.

According to one of the features of this embodiment, the generated light tiles are randomly arranged. In this specification, the term "random" means that the light tiles are aperiodic or uncorrelated in at least one direction (for example, the horizontal direction). In other words, the light tiles do not have or repeat any pattern along a specific direction (for example, the horizontal direction or the X direction). In this way, adjacent light tiles generated by the diffractive optical element (DOE) 13 can partially overlap.

The third diagram A illustrates that the centers of the light tiles are periodically arranged, and each column has the same spacing and is vertically aligned with each other. The third figure B illustrates that the centers of the light tiles are periodically arranged, and each column has the same spacing but is vertically interlaced with each other. The third diagram C illustrates the centers of the light bricks generated by the diffractive optical element (DOE) 13 of the first diagram B in the embodiment of the present invention, which are arranged randomly or non-periodically. Generally speaking, the light tiles move slightly and randomly along at least one direction from the periodically arranged position. In one embodiment, the moving range of the light brick needs to be smaller than the preset range, so that the light spot density of the projected image of the object in the far area can be maintained higher than the preset threshold. The third diagram D shows that each light tile moves randomly among the corresponding borders 130, wherein the center of each border 130 is located at a periodically arranged non-moving position. It is worth noting that the boundaries 130 do not overlap with each other. In other words, there needs to be a gap with a preset value between adjacent borders 130.

The performance (especially the decoding rate) of the projector with periodically arranged light tiles is very poor, mainly because it has a highly repetitive pattern, which increases the difficulty of pattern matching. On the contrary, in this embodiment, the light bricks of the structured light projector 100 are randomly arranged, thus overcoming the lack of projectors with periodically arranged light bricks, thereby greatly improving the decoding rate and performance.

Furthermore, according to optical theory, if the focal length f of the collimating lens (that is, the beam limiting device 12) illustrated in the first figure B is reduced, the preset pattern of the light source 11 projected on the far-area object will increase its magnification. . It is worth noting that the increase in the magnification rate does not affect the decoding rate performance of this embodiment. Therefore, the overall volume of the structured light projector 100 can be reduced, so that the projector can be miniaturized. Furthermore, due to the random arrangement of the light tiles, the number of vertical cavity surface emitting laser (VCSEL) diodes of the light source 11 can be reduced without affecting the light spot density of the projected image of the object in the far area. Therefore, the overall cost of the structured light projector 100 can be reduced, making the price of the projector cheaper.

In one embodiment, the density of the light tiles at the edges is higher than in other areas. Therefore, the light spot density at the edge of the projected image of the object in the far area can be roughly the same as that in other areas, and will not be affected by non-paraxial distortion, thereby enhancing the three-dimensional mapping. The third diagram E illustrates that more light tiles are arranged on the edge.

In another embodiment, the alignment of the light tiles is corrected to compensate for the optical distortion generated at the edge of the projected image of the object in the far area. The third F diagram illustrates correction for the arrangement of light tiles.

The fourth figure illustrates a cross-sectional view of the structured light projector 100 according to an embodiment of the present invention. In this embodiment, the structured light projector 100 may include a chip 31 (as the light source 11), which includes a vertical cavity surface-emitting laser (VCSEL) diode. The wafer 31 is disposed on the substrate 32. The structured light projector 100 may include a collimator lens 33 (as the beam limiting device 12), which is isolated from the chip 31 and the substrate 32 by a first spacer 34. The structured light projector 100 may include a diffractive optical element 13 which is separated from the collimating lens 33 by a second spacer 35. Thereby, the collimating lens 33 is located between the wafer 31 and the diffractive optical element 13.

Fig. 5A shows a block diagram of the structured light projector 200 of the second embodiment of the present invention, and Fig. 5B illustrates a schematic diagram of the structured light projector 200 of Fig. 5A. The same technical details as the previous embodiment are given. Omitted.

In this embodiment, the structured light projector 200 may include a light source 11, especially a point light source, to generate emitted light. The light source 11 of this embodiment may include a single semiconductor diode. In a preferred embodiment, the light source 11 may include an edge-emitting laser diode.

The structured light projector 200 of this embodiment may include a beam limiting device 12, which receives the emitted light (from the light source 11) and limits the cross section of the emitted light, thereby forming collimated light. In a preferred embodiment, the beam limiting device 12 may include a collimating lens, which may include a transparent material (such as plastic or glass), and may be manufactured using wafer level optics (WLO) technology.

The structured light projector 200 of this embodiment may include a patterning device 14 that receives the collimated light (from the beam limiting device 12) and generates patterned light. In one embodiment, the patterning device 14 may include a diffractive optical element, or other suitable optical elements for generating patterned light with a predetermined pattern.

The structured light projector 200 of this embodiment may include a diffractive optical element (DOE) 13, which receives patterned light (from the patterning device 14) and generates a plurality of light tiles. The light bricks are spaced from each other in a two-dimensional manner. As illustrated in FIG. 5B, the diffractive optical element 13 of this embodiment may include a plurality of optical component elements (for example, diffractive optical component elements) 131, which are disposed on the substrate 132. Similar to the previous embodiment, the light tiles are arranged randomly.

The sixth figure shows a block diagram of a modified structured light projector 300 according to the second embodiment of the present invention. This embodiment is similar to the embodiment of FIG. 5A, except that the diffractive optical element 13 of this embodiment is located in front of the patterning device 14. Therefore, the diffractive optical element 13 receives the collimated light (from the beam limiting device 12) and generates a plurality of (unpatterned) light tiles. Next, the patterning device 14 receives the light tiles (from the diffractive optical element 13) and generates patterned light tiles.

FIG. 7A shows a block diagram of the structured light projector 400 of the third embodiment of the present invention, and FIG. 7B illustrates a schematic diagram of the structured light projector 400 of FIG. 7A.

In this embodiment, the structured light projector 400 may include a light source 11 that generates emitted light with a predetermined pattern. The emitted light may be visible light or/and invisible light (for example, infrared light). The light source 11 of this embodiment may include an array of semiconductor diodes arranged according to a preset pattern. In a preferred embodiment, the light source 11 may include a vertical-cavity surface-emitting laser (VCSEL) diode array, arranged on a substrate (not shown), and arranged according to a preset pattern . In this way, a vertical cavity surface-emitting laser (VCSEL) diode is used as the light source 11 to perform light emission and patterning at the same time.

The structured light projector 400 of this embodiment may include a diffractive optical element (DOE) 13, which receives the emitted light (from the light source 11) and generates a plurality of light tiles. The light bricks are spaced from each other in a two-dimensional manner. As illustrated in FIG. 7B, the diffractive optical element 13 of this embodiment may include a plurality of optical components (for example, diffractive optical components) 131, which are disposed on the substrate 132. The optical component 131 may be provided on the side opposite to the light source 11 (for example, the right side). The diffractive optical element 13 may include a transparent material, such as plastic or glass. Compared with the embodiment shown in Fig. 1A, since this embodiment does not include the beam limiting device 12 between the light source 11 and the diffractive optical element 13, the structured light projector 400 of this embodiment can be compared with the first The structured light projector 100 shown in Figure A is more compact.

Fig. 8A illustrates that the centers of the light bricks generated by the diffractive optical element 13 in Fig. 7A are arranged randomly (or non-periodically). The eighth image B shows the randomly arranged light tiles of the eighth image A, which partially overlap.

Fig. 9A illustrates the regular (or periodic) arrangement of the centers of the light bricks generated by the diffractive optical element 13 in Fig. 7A. The ninth picture B shows that the ninth picture A has regular (or fan-out) arrangement of light tiles, which partially overlap. It is worth noting that the light spot density of the overlapping light bricks in the ninth image B is uniform compared to the light spot density of the overlapping light bricks in the eighth image B, and has a higher contrast ratio. However, the overlapping light tiles of the eighth image B have higher efficiency because there are more light spots located in the region of interest (ROI).

The above descriptions are only the preferred embodiments of the present invention, and are not intended to limit the scope of patent application of the present invention; all other equivalent changes or modifications made without departing from the spirit of the invention should be included in the following Within the scope of the patent application.

100‧‧‧Structured light projector 200‧‧‧Structured light projector 300‧‧‧Structured light projector 400‧‧‧Structured light projector 11‧‧‧Light source 12‧‧‧Beam limiting device 13‧‧‧Diffraction Optical component 131‧‧‧Optical component 132‧‧‧Substrate 14‧‧‧Pattern device 31‧‧‧Chip 32‧‧‧Substrate 33‧‧‧Collimating lens 34‧‧‧First spacer 35‧‧‧ Second spacer DOE‧‧‧Diffraction optical element f‧‧‧Focal length

Fig. 1A shows a block diagram of the structured light projector according to the first embodiment of the present invention. Fig. 1B illustrates a schematic diagram of the structured light projector of Fig. 1A. The second diagram A shows that part of the semiconductor diodes of the light source are divided into two adjacent groups and sequentially lit. The second figure B shows that part of the semiconductor diodes of the light source are divided into two intersecting groups and sequentially lit. The second figure C shows that part of the semiconductor diodes of the light source are divided into two crossed groups according to their shapes and are sequentially lit. The third diagrams A and B illustrate that the centers of the light bricks are periodically arranged. The third diagram C and the third diagram D illustrate the centers of the light bricks generated by the diffractive optical element of the first diagram B in the embodiment of the present invention, which are arranged randomly or non-periodically. The third diagram E illustrates that more light tiles are arranged on the edge. The third F diagram illustrates correction for the arrangement of light tiles. The fourth figure illustrates a cross-sectional view of the structured light projector according to the embodiment of the present invention. Fig. 5A shows a block diagram of the structured light projector according to the second embodiment of the present invention. Fig. 5B illustrates a schematic diagram of the structured light projector of Fig. 5A. The sixth figure shows a block diagram of a modified structured light projector of the second embodiment of the present invention. Figure 7A shows a block diagram of a structured light projector according to a third embodiment of the present invention. Figure 7B illustrates a schematic diagram of the structured light projector of Figure 7A. Fig. 8A illustrates that the centers of the light bricks generated by the diffractive optical element of Fig. 7A are arranged randomly (or non-periodically). The eighth image B shows the randomly arranged light tiles of the eighth image A, which partially overlap. Fig. 9A illustrates the regular arrangement of the centers of the light bricks generated by the diffractive optical element in Fig. 7A. The ninth picture B shows the ninth picture A with regularly arranged light tiles, which partially overlap.

100‧‧‧Structured light projector

11‧‧‧Light source

12‧‧‧Beam limiting device

13‧‧‧Diffraction optics

DOE‧‧‧Diffraction optical element

Claims (13)

A structured light projector, comprising: a light source, which generates emitted light with a preset pattern; a beam limiting device, which receives the emitted light and generates collimated light; and a diffractive optical element, which receives the collimated light and generates a complex number The light bricks are randomly arranged; the arrangement of the light bricks is corrected to compensate for the optical distortion generated at the edge of the projected image of the object in the remote area; wherein the diffractive optical element is adjusted by the optical component of the edge, The density of the generated light tiles at the edges is higher than that of other areas, so that the light spot density at the edges of the projected image of the objects in the far area is the same as that of other areas, and will not be affected by non-paraxial distortion. Such as the structured light projector of claim 1, wherein the light source includes a semiconductor diode array arranged according to the preset pattern. Such as the structured light projector of claim 2, wherein the semiconductor diodes are divided into plural groups and light up in sequence. Such as the structured light projector of claim 3, wherein different groups of semiconductor diodes have different shapes or sizes. Such as the structured light projector of claim 1, wherein adjacent light tiles generated by the diffractive optical element partially overlap. A structured light projector, comprising: a point light source to generate emitted light; a beam limiting device to receive the emitted light and generate collimated light; A patterning device that receives the collimated light and generates patterned light; and a diffractive optical element that receives the patterned light and generates a plurality of light tiles, which are arranged randomly; wherein the alignment of the light tiles is corrected to compensate The optical distortion caused by the projected image of the object in the far area at the edge; wherein the diffractive optical element adjusts the optical components of the edge so that the density of the generated light bricks at the edge is higher than that in other areas, thereby far The light spot density at the edge of the projected image of the regional object is the same as that of other regions, and will not be affected by non-paraxial distortion. Such as the structured light projector of claim 6, wherein the point light source includes a side-fired laser diode. Such as the structured light projector of claim 6, wherein adjacent light tiles generated by the diffractive optical element partially overlap. A structured light projector, comprising: a point light source to generate emitted light; a beam limiting device to receive the emitted light and generate collimated light; a diffractive optical element to receive the collimated light and generate a plurality of light bricks, which are arranged randomly ; And a patterning device that receives the light tiles and generates a plurality of patterned light tiles; wherein the alignment of the light tiles is corrected to compensate for the optical distortion generated at the edge of the projected image of the object in the remote area; wherein the winding The optical component adjusts the edge optical component so that the density of the generated light bricks at the edge is higher than that of other areas, so that the light spot density of the edge of the projected image of the object in the far area is the same as that of other areas. Will be affected by non-paraxial distortion. Such as the structured light projector of claim 9, wherein the generated adjacent patterned light tiles partially overlap. A structured light projector, comprising: a light source, which generates emitted light with a preset pattern; and a diffractive optical element, which receives the emitted light and generates a plurality of light bricks, which are arranged randomly; wherein the arrangement of the light bricks is performed Correction is used to compensate for the optical distortion produced at the edge of the projected image of the object in the far area; wherein the diffractive optical element adjusts the optical component of the edge so that the density of the generated light tiles at the edge is higher than other Area, whereby the light spot density at the edge of the projected image of the object in the far area is the same as in other areas, and will not be affected by non-paraxial distortion. Such as the structured light projector of claim 11, wherein the light source includes a semiconductor diode array arranged according to the preset pattern. Such as the structured light projector of claim 11, wherein adjacent light tiles generated by the diffractive optical element partially overlap.

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