TWI909823B - Projector and sensing system used therefor - Google Patents

Abstract

A projector includes a light source and a diffractive optical element. The light source has a first light emitting area and a second light emitting area. The diffractive optical element is disposed on the light source. The diffraction optical element has a first diffraction structure and a second diffraction structure, respectively overlapping the first light emitting area and the second light emitting area, and the first diffraction structure is different from the second diffraction structure. A sensing system is also provided.

Description

Light projector and sensing system used with the light projector

This invention relates to an electronic device, and more particularly to a light projector and a sensing system used in conjunction with the light projector.

With technological advancements, the positioning capabilities of electronic products for environmental objects or users are becoming increasingly important (e.g., augmented reality (AR), virtual reality (VR), and mixed reality (MR) tracking of user hand positions, smart home appliances, or autonomous vehicles sensing 3D information of objects in their environment). However, as the market expands the application of electronic products, it is becoming increasingly difficult to further reduce the weight, size, and cost of existing sensing systems for use in various electronic products (such as head-mounted displays or handheld mobile devices). Solving these problems remains a challenge for manufacturers.

This invention provides a light projector that reduces costs, device size and weight, and has good versatility.

This invention provides a sensing system that reduces the number of light projectors required, further reducing costs, device size, and weight. In addition to improving sensing performance, it also enhances the versatility of the sensing system and reduces its computational burden.

An embodiment of the present invention includes a light projector comprising a light source and a diffractive optical element. The light source has a first light-emitting region and a second light-emitting region, and the diffractive optical element is disposed on the light source. The diffractive optical element has a first diffraction structure and a second diffraction structure, which overlap the first light-emitting region and the second light-emitting region, respectively. The first diffraction structure is different from the second diffraction structure.

An embodiment of the sensing system of the present invention includes a light source, a diffractive optical element, and a camera. The light source has a first emitting region and a second emitting region, and the diffractive optical element is disposed on the light source. The diffractive optical element has a first diffraction structure and a second diffraction structure, which overlap the first emitting region and the second emitting region, respectively, and the first diffraction structure is different from the second diffraction structure. The camera is used to receive the light beam reflected by the object to be measured.

Based on the above, in the light projector and sensing system of this invention, the diffractive optical element (DOE) includes optical diffraction structures with different patterns. When a light beam emitted from the same light source passes through optical diffraction structures with different patterns, different diffraction patterns can be generated. Different diffraction patterns can be applied to sensing different distances. Therefore, this invention can generate multiple diffraction patterns with a single light projector. Compared to the structure of generating multiple diffraction patterns with multiple light projectors, this can effectively save costs and device space. Furthermore, it can tailor the required optical diffraction structure for different sensing distances (e.g., the object being measured is the user's face or finger, the object being measured is the user's surrounding environment, the object being measured is the space where the user is located, etc.), which can greatly improve the modeling accuracy of the sensing system.

Furthermore, when light projectors or sensing systems are used in near-eye display devices (such as augmented reality (AR), virtual reality (VR), and mixed reality (MR)) for triangulation and depth calculation, the center of the device is where the coverage of the two cameras is highest, and therefore usually also where the most optical elements are covered. If the light projector is split into multiple units, it will affect the coverage of the camera depth calculation and significantly increase the computational load required by the solid-state processing unit (CPU) in the sensing system. Conversely, the light projector or sensing system of this invention can generate various diffraction patterns with a single light projector, thereby being applicable to various sensing spaces and achieving optimal spatial coverage. This improves the performance of near-eye display devices, facilitates weight reduction, and significantly enhances product competitiveness.

To make the above features and advantages of this invention more apparent and understandable, specific examples are given below, and detailed explanations are provided in conjunction with the accompanying drawings.

As used herein, “about,” “approximately,” “essentially,” or “substantially” includes the value and the average of the values within an acceptable range of deviation from a particular value as determined by a person of ordinary skill in the art, taking into account the measurement under discussion and a particular number of errors associated with the measurement (i.e., limitations of the measurement system). For example, “about” may mean within one or more standard deviations of the value, or, for example, within ±30%, ±20%, ±15%, ±10%, ±5%. Furthermore, as used herein, “about,” “approximately,” “essentially,” or “substantially” may be used to select a more acceptable range of deviations or standard deviations depending on the nature of the measurement, the cutting nature, or other properties, and may not require a single standard deviation to apply to all properties.

In the accompanying figures, the thicknesses of layers, films, panels, areas, etc., are enlarged for clarity. It should be understood that when a component such as a layer, film, area, or substrate is referred to as being "on" or "connected to" another component, it may be directly on or connected to the other component, or an intermediate component may also be present. Conversely, when a component is referred to as being "directly on" or "directly connected to" another component, no intermediate component exists. As used herein, "connection" can refer to physical and/or electrical connection. Furthermore, "electrical connection" may mean the presence of other components between two components.

Reference will now be made to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same element symbols are used in the drawings and description to denote the same or similar parts.

Figure 1 is a schematic diagram of the structure of a light projector according to an embodiment of the present invention, and a diagram of the diffraction pattern generated by the light projector. Referring to Figure 1, the light projector 10 includes a light source 100, a diffractive optical element 110, a light blocking layer 120, a lens array 130, and a frame 140. The light source 100 may include a first emitting region 101, a second emitting region 102, and a third emitting region 103. However, the present invention is not limited thereto. In other embodiments, the light source 100 may include at least two emitting regions, such as a first emitting region 101 and a second emitting region 102. The light source 100 is used to provide a light beam; for example, the first emitting region 101, the second emitting region 102, and the third emitting region 103 may respectively emit a first light beam L1, a second light beam L2, and a third light beam L3 within the same wavelength range or different wavelength ranges. The wavelength range of the first beam L1, the second beam L2, and the third beam L3 may include the visible light band (e.g., wavelengths between 380 nm and 750 nm) or the infrared light band (e.g., wavelengths above 750 nm or near-infrared light bands above 1054 nm), but the invention is not limited thereto.

The light source 100 can be a light-emitting diode (LED), a laser-emitting diode (LD), or a vertical-cavity surface-emitting laser (VCSEL), etc. Furthermore, the light source 100 can include at least one of a point-shaped VCSEL, a linear VCSEL, an edge-emitting laser, and a random-point VCSEL; however, this invention is not limited to these. For example, in this embodiment, the light source 100 can be a VCSEL, and the structures of the first emitting region 101, the second emitting region 102, and the third emitting region 103 can be fabricated by epitaxially layering different blocks of VCSELs during semiconductor manufacturing; this invention is also not limited to these.

A diffusing optical element 110 is disposed on the light source 100. More specifically, the diffusing optical element 110 is disposed in the light-emitting direction of the light source 100. The diffusing optical element 110 (DOE) is an optical element obtained by fabricating a microstructure on its surface using semiconductor processes, which allows light beams to diffract. When the first light beam L1, the second light beam L2, and the third light beam L3 irradiate the diffusing optical element 110, the desired diffraction pattern or structured light can be generated at a specific location or space due to the diffraction effect of the microstructure. This diffraction pattern can be a one-dimensional line, a one-dimensional dotted light spot, a two-dimensional randomly distributed light spot, or a two-dimensional regularly arranged light spot; the invention is not limited to these.

It is worth mentioning that, in this embodiment, the diffractive optical element 110 also has a first diffraction structure 111, a second diffraction structure 112 and a third diffraction structure 113, which overlap the first light-emitting region 101, the second light-emitting region 102 and the third light-emitting region 103 respectively, wherein the first diffraction structure 111 is different from the second diffraction structure 112.

Since the first diffraction structure 111 and the second diffraction structure 112 can have different surface microstructures, the first beam L1 and the second beam L2 can produce different diffraction patterns when they pass through the first diffraction structure 111 and the second diffraction structure 112, respectively. For example, the first beam L1 emitted from the first emitting region 101 can generate a first diffraction pattern DP1 after passing through the first diffraction structure 111, and the second beam L2 emitted from the second emitting region 102 can generate a second diffraction pattern DP2 after passing through the second diffraction structure 112. Furthermore, the first diffraction pattern DP1 can include multiple high-density dot-shaped light spots, and the second diffraction pattern DP2 can include multiple striped light spots (as shown in Figure 1) or multiple low-density dot-shaped light spots (not shown).

In the field of sensing, to sense three-dimensional information of objects at different distances, structured light technology can be used. A light projector emits beams with specific diffraction patterns to objects at different distances. A stereo depth camera then receives the diffraction patterns on the object's surface and compares them with the original projected light spots, or compares the images from two cameras. Using triangulation principles, the object's three-dimensional coordinates or surface contours can be calculated. For example, the first diffraction pattern DP1 can be multiple high-density point-like light spots with a small field of view (FOV), suitable for sensing three-dimensional spatial information (such as surface contours, depth, or three-dimensional coordinates) of a first object OB1 at close range, such as the user's finger position, hand movement, or eye tracking. The second diffraction pattern DP2 can be multiple striped light spots with a wide field of view (FOV), suitable for sensing the three-dimensional spatial information (such as surface contours or three-dimensional coordinates) of a second object OB2 at a medium distance, such as furniture or obstacles around the user. Therefore, a single light projector 10 can tailor the required diffraction pattern for the sensing distance of a specific object, greatly improving the versatility and modeling accuracy of the light projector 10 when sensing different objects and objects at different distances. Compared to the implementation of providing different diffraction patterns with different light projectors, the light projector 10 also further simplifies the device architecture and achieves device lightweighting, which can effectively enhance the competitiveness of the product when applied to wearable devices.

Furthermore, the diffractive optical element 110 also includes a third diffraction structure 113 overlapping the third light-emitting region 103, wherein the first diffraction structure 111, the second diffraction structure 112, and the third diffraction structure 113 may all be different from each other. For example, the third diffraction pattern DP3 formed by the third beam L3 after passing through the third diffraction structure 113 may be different from the first diffraction pattern DP1 and the second diffraction pattern DP2. For example, the third diffraction pattern DP3 includes multiple point-like light spots, and the density of the multiple point-like light spots in the third diffraction pattern DP3 may be less than the density of the multiple point-like light spots in the first diffraction pattern DP1. In this embodiment, the multiple point-like spots of the third diffraction pattern DP3 can be arranged in a matrix, while the point-like spots of the first diffraction pattern DP1 can be arranged randomly. This invention is not limited to this.

When the third diffraction pattern DP3 consists of multiple low-density point-like light spots with a small field of view (FOV), it is suitable for low-resolution sensing spaces, reducing the computational load required for three-dimensional spatial modeling. For example, it can be used to sense three-dimensional spatial information of a third object OB3 located at a greater distance from the user, such as the size of the room or modeling the furniture arrangement. Therefore, the light projector 10 can be applied in a wider range of fields. It is worth noting that in embodiments not shown, the light projector may consist only of a first emitting area 101 and a second emitting area 102, and correspondingly, the diffractive optical element 110 may consist only of a first diffraction structure 111 and a second diffraction structure 112 overlapping the first emitting area 101 and the second emitting area 102, respectively. In other embodiments, the light projector may also include more light-emitting zones and correspondingly more different diffraction structures, but the invention is not limited thereto.

On the other hand, the photoblocking layer 120 is disposed between the first diffraction structure 111 and the second diffraction structure 112, and between the second diffraction structure 112 and the third diffraction structure 113. The photoblocking layer 120 may include, but is not limited to, a dark-colored light-blocking material (such as black), a light-blocking material with high optical density (e.g., optical density OD value > 0.5), a light-blocking material with low transmittance (e.g., transmittance less than or equal to 30%) to the first beam L1, the second beam L2, and the third beam L3, or a light-blocking material with high absorption to the first beam L1, the second beam L2, and the third beam L3. By using the photoblocking layer 120, the proportion of the first beam L1 illuminating the adjacent second diffraction structure 112 can be reduced, the proportion of the second beam L2 illuminating the adjacent first diffraction structure 111 and third diffraction structure 113 can be reduced, and the proportion of the third beam L3 illuminating the adjacent second diffraction structure 112 can also be reduced. In other words, the photoblocking layer 120 can reduce the crosstalk between the first diffraction pattern DP1, the second diffraction pattern DP2, and the third diffraction pattern DP3 and reduce the generation of stray light. When used in sensing applications, this can further improve the clarity of structured light and the sensitivity of sensing.

Furthermore, the lens array 130 is disposed between the light source 100 and the diffractive optical element 110 to further focus the light beam emitted by the light source 100, thereby improving the light energy utilization rate of the light source 100 and the brightness of the generated diffraction pattern. More specifically, the lens array 130 includes a first lens 131, a second lens 132, and a third lens 133, all of which can be focusing lenses. In this embodiment, a first lens 131 is disposed between a first light-emitting area 101 and a first diffraction structure 111, a second lens 132 is disposed between a second light-emitting area 102 and a second diffraction structure 112, and a third lens 133 is disposed between a third light-emitting area 103 and a third diffraction structure 113. Furthermore, the refractive power of the first lens 131 may be less than that of the second lens 132, and the refractive power of the second lens 132 may be greater than that of the third lens 133.

By using lenses with different focusing capabilities in the lens array 130, the light beams emitted from the first light-emitting area 101, the second light-emitting area 102, and the third light-emitting area 103 can be focused separately, allowing the light energy from different areas to be focused at the desired distance. For example, the refractive power of the third lens 133 can be minimized, which can effectively improve the sharpness and clarity of the third diffraction pattern DP3 illuminating the third object OB3 when applied to long-distance sensing. In other embodiments, if the parallelism of the light beam emitted by the light source 100 is high, the lens array 130 can be omitted to further reduce the size, weight, and cost of the light projector; however, the invention is not limited to this.

On the other hand, the frame 140 may have accommodating space, allowing the light source 100, diffractive optical element 110, photoresist barrier layer 120, and lens array 130 to be disposed within the frame 140. The frame 140 may be made of a material with high absorption rate for the first beam L1, the second beam L2, and the third beam L3, to further reduce the light leakage ratio of the beam emitted by the light source 100 and improve the light energy utilization rate. In some embodiments, the frame 140 may have an opening (not shown) to allow the circuit pins of the light source 100 to extend outside the frame 140 to provide the control signals or power signals required by the light source 100; however, the invention is not limited to this.

Figures 2A to 2C are schematic diagrams of a diffractive optical element and the corresponding diffraction pattern generated according to an embodiment of the present invention. Referring to Figure 2A, the first diffraction structure 111 of the diffractive optical element 110 may include a plurality of high-density arranged first microstructures MS1, thereby generating a corresponding first diffraction pattern DP1 (e.g., a plurality of randomly distributed dot-shaped light spots) when the first beam L1 passes through the first diffraction structure 111. Alternatively, as shown in Figure 2B, the third diffraction structure 113 of the diffractive optical element 110 may include a plurality of low-density arranged third microstructures MS3, thereby generating a corresponding third diffraction pattern DP3 (e.g., a plurality of dot-shaped light spots arranged in a matrix) when the third beam L3 passes through the third diffraction structure 113. Similarly, as shown in Figure 2C, the second diffraction structure 112 of the diffraction optical element 110 may include a plurality of low-density arranged second microstructures MS2, thereby generating a corresponding second diffraction pattern DP2 (e.g., a regular plurality of striped light spots) when the second beam L2 passes through the second diffraction structure 112. Accordingly, different diffraction structures can be used for different sensing applications to generate different diffraction patterns, thereby improving the versatility of the light projector 10.

Figures 3A to 3H are schematic diagrams illustrating the manufacturing process of a diffractive optical element and a photoresist blocking layer according to an embodiment of the present invention. Referring first to Figures 3A and 3B, the method for manufacturing the diffractive optical element 110 is, for example, a photolithography process. For example, a substrate GS (e.g., a glass substrate, but not limited thereto) is first provided, and a first photoresist PR1 is coated on the substrate GS. The method for coating the first photoresist PR1 is, for example, a spin coating method, but the present invention is not limited thereto.

Referring to Figures 3C to 3D, the first photoresist PR1 is first exposed to generate the desired pattern P on the substrate GS. Then, using a developing process and an etching process, the corresponding pattern P is fabricated into microstructures MSA, MSB, and MSC. The microstructures MSA, MSB, and MSC can, for example, correspond to the first diffraction structure 111, the second diffraction structure 112, and the third diffraction structure 113 of the aforementioned embodiments, respectively; however, the invention is not limited thereto.

Next, referring to Figures 3E to 3F, a second photoresist PR2 is coated onto the microstructures MSA, MSB, and MSC. The method of coating the second photoresist PR2 can be the same as or different from the method of coating the first photoresist PR1, and the invention is not limited thereto. Then, as shown in Figure 3F, a developing process and an etching process are performed on the second photoresist PR2 to form the grooves G between each pair of microstructures MSA, MSB, and MSC. At this point, the fabrication of the diffractive optical element 110 is initially completed, and the first diffraction structure 111, the second diffraction structure 112, and the third diffraction structure 113 are defined.

Continuing with Figures 3G to 3H, the third photoresist PR3 can then be applied to the groove G, and an exposure and development process can be performed on the third photoresist PR3. Finally, the third photoresist PR3 is used to form the photoresist block layer 120, thereby completing the setup of the photoresist block layer 120.

Figure 4 is a schematic diagram of the structure of a sensing system and a schematic diagram of the generated diffraction pattern according to an embodiment of the present invention. Referring to Figure 4, the sensing system 1 can be used to sense three-dimensional information (e.g., depth, surface contour, or three-dimensional coordinates) of the object to be measured. The sensing system 1 may include the aforementioned light projector 10, a first camera 20A, and a second camera 20B. When the structured light emitted by the light projector 10 (such as the second diffraction pattern DP2 shown in Figure 4) illuminates the object to be measured (e.g., the second object to be measured OB2 shown in Figure 4), the reflected light beam can be sensed by the first camera 20A and the second camera 20B. The optical sensors (not shown) in the first camera 20A and the second camera 20B can convert the received light signal into an electrical signal. The sensing system 1 may also include a solid-state processor (not shown) that can receive this electrical signal to determine the three-dimensional information of the second test object OB2. The solid-state processor may include, for example, a microcontroller unit (MCU), a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a programmable controller, a programmable logic device (PLD), or other similar devices or combinations thereof, and the invention is not limiting. Furthermore, in one embodiment, the functions of the solid-state processor may be implemented as multiple code snippets. These code snippets are stored in memory and executed by the solid-state processor. Alternatively, in some embodiments, the functions of the solid-state processor may be implemented as one or more circuits. This invention does not limit the implementation of solid-state processor functions in terms of software or hardware.

As mentioned above, since the light projector 10 has multiple light-emitting areas to emit different diffraction patterns (such as the first diffraction pattern DP1, the second diffraction pattern DP2, and the third diffraction pattern DP3 shown in Figure 1), the solid-state processor can also control the light projector 10 to generate different diffraction patterns according to different sensing distances or application scenarios, greatly improving the versatility of the sensing system 1. In addition, when the sensing system 1 is applied to near-eye display devices (such as augmented reality (AR), virtual reality (VR), and mixed reality (MR)) for triangulation and depth calculation, the center position of the near-eye display device is the area with the highest coverage of the first camera 20A and the second camera 20B, and therefore usually has the most optical elements covered. If the light projector is split into multiple units, it will affect the coverage of the camera depth calculation and increase the computational burden on the solid-state processor. In contrast, the sensing system 1 of this invention can generate different diffraction patterns with a single light projector 10. Therefore, it can be placed at the center of the near-eye display device and achieve the best spatial coverage, thereby improving the performance of the near-eye display device and effectively reducing the product weight, size and cost.

In summary, in the light projector and sensing system of this invention, the diffractive optical element (DOE) includes optical diffraction structures with different patterns. When a light beam emitted from the same light source passes through optical diffraction structures with different patterns, different diffraction patterns can be produced. Different diffraction patterns can be applied to sensing different distances. Therefore, this invention can generate multiple diffraction patterns with a single light projector. Compared with the structure of generating multiple diffraction patterns with multiple light projectors, it can effectively save costs and device space. Furthermore, it can tailor the required optical diffraction structure for different sensing distances (such as the object being measured being the user's face or fingers, the object being measured being the user's surrounding environment, the object being measured being the space where the user is located, etc.), which can greatly improve the modeling accuracy of the sensing system.

Furthermore, when light projectors or sensing systems are used in near-eye display devices (such as augmented reality (AR), virtual reality (VR), and mixed reality (MR)) for triangulation and depth calculation, the center of the device is where the coverage of the two cameras is highest, and therefore usually also where the most optical elements are covered. If the light projector is split into multiple units, it will affect the coverage of the camera depth calculation and significantly increase the computational load required by the solid-state processing unit (CPU) in the sensing system. Conversely, the light projector or sensing system of this invention can generate various diffraction patterns with a single light projector, thereby being applicable to various sensing spaces and achieving optimal spatial coverage. This improves the performance of near-eye display devices, facilitates weight reduction, and significantly enhances product competitiveness.

Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Anyone with ordinary skill in the art may make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended patent application.

1: Sensing System 10: Light Projector 20A: First Camera 20B: Second Camera 100: Light Source 101: First Light-Emitting Area 102: Second Light-Emitting Area 103: Third Light-Emitting Area 110: Diffraction Optical Element 111: First Diffraction Structure 112: Second Diffraction Structure 113: Third Diffraction Structure 120: Optical Blocking Layer 130: Lens Array 131: First Lens 132: Second Lens 133: Third Lens 140: Frame L1: First Beam L2: Second Beam L3: Third Beam DP1: First Diffraction Pattern DP2: Second Diffraction Pattern DP3: Third Diffraction Pattern G: Groove GS: Substrate MS1: First Microstructure MS2: Second Microstructure MS3: Third Microstructure MSA, MSB, MSC: Microstructures OB1: First Analyte OB2: Second Analyte OB3: Third Analyte P: Pattern PR1: First Photoresist PR2: Second Photoresist PR3: Third Photoresist

Figure 1 is a schematic diagram of the structure of a light projector according to an embodiment of the present invention, and a schematic diagram of the diffraction pattern generated by the light projector. Figures 2A to 2C are schematic diagrams of a diffractive optical element according to an embodiment of the present invention and the corresponding diffraction pattern generated therefrom. Figures 3A to 3H are schematic diagrams of the manufacturing process of the diffractive optical element and the photoblocking layer according to an embodiment of the present invention. Figure 4 is a schematic diagram of the structure of a sensing system according to an embodiment of the present invention and a schematic diagram of the diffraction pattern generated therefrom.

10: Light Projector

100: Light source

101: First Lighting Zone

102: Second Illumination Zone

103: Third Illumination Zone

110: Diffractive optical components

111: First Diffraction Structure

112: Second Diffraction Structure

113: Third Diffraction Structure

120: Photoresist barrier layer

130: Lens Array

131: First Lens

132: Second Lens

133: Third Lens

140: Frame

L1: First beam

L2: Second beam

L3: Third Beam

DP1: First Diffraction Pattern

DP2: Second Diffraction Pattern

DP3: Third Diffraction Pattern

OB1: First Analyte

OB2: Second analyte

OB3: Third analyte

Claims (16)

A light projector includes: a light source having a first emitting region and a second emitting region; a diffractive optical element disposed on the light source, wherein the diffractive optical element has a first diffraction structure and a second diffraction structure overlapping the first emitting region and the second emitting region, respectively, wherein the first diffraction structure is different from the second diffraction structure; and a lens array disposed between the light source and the diffractive optical element, the lens array including a first lens and a second lens, both the first lens and the second lens being condensing lenses, wherein the first lens is disposed between the first emitting region and the first diffraction structure, and the second lens is disposed between the second emitting region and the second diffraction structure, wherein the refractive power of the first lens is greater than the refractive power of the second lens. The light projector as claimed in claim 1 further includes a light blocking layer disposed between the first diffraction structure and the second diffraction structure. The light projector as claimed in claim 1 further includes a housing in which the light source and the diffracting optical element are disposed. The light projector as claimed in claim 1, wherein the wavelength range of the light beam emitted by the light source includes at least one of the visible light band and the infrared light band. The light projector as claimed in claim 1, wherein the light beam emitted by the light source forms a first diffraction pattern after passing through the first diffraction structure, and forms a second diffraction pattern after passing through the second diffraction structure, wherein the first diffraction pattern includes multiple dot-shaped light spots, and the second diffraction pattern includes multiple striped light spots. The light projector as claimed in claim 5, wherein the light source further includes a third emitting region, and the diffractive optical element further includes a third diffraction structure overlapping the third emitting region, wherein the first diffraction structure, the second diffraction structure, and the third diffraction structure are all different. The light projector as claimed in claim 6, wherein the light beam emitted by the light source forms a third diffraction pattern after passing through the third diffraction structure, the third diffraction pattern comprising a plurality of dot-shaped light spots, wherein the density of the plurality of dot-shaped light spots in the third diffraction pattern is less than the density of the plurality of dot-shaped light spots in the first diffraction pattern. The light projector as claimed in claim 1, wherein the light source comprises at least one of a point-type vertical cavity surface-emitting laser, a linear vertical cavity surface-emitting laser, an edge-emitting laser, and a random-point vertical cavity surface-emitting laser. A sensing system for sensing three-dimensional information of an object under test, the sensing system comprising: a light projector, the light projector comprising: a light source having a first emitting region and a second emitting region for emitting a light beam to illuminate the object under test; a diffractive optical element disposed on the light source, wherein the diffractive optical element has a first diffraction structure and a second diffraction structure, respectively overlapping the first emitting region and the second emitting region, wherein the first diffraction structure is different from the second diffraction structure; and A lens array, disposed between the light source and the diffractive optical element, the lens array including a first lens and a second lens, both the first lens and the second lens being condensing lenses, wherein the first lens is disposed between the first light-emitting area and the first diffraction structure, and the second lens is disposed between the second light-emitting area and the second diffraction structure, the refractive power of the first lens being greater than the refractive power of the second lens; and a camera for receiving the light beam reflected by the object under test. The sensing system as described in claim 9 further includes a photoresist layer disposed between the first diffraction structure and the second diffraction structure. The sensing system as described in claim 9 further includes a housing in which the light source and the diffracting optical element are disposed. The sensing system as claimed in claim 9, wherein the wavelength range of the light beam emitted by the light source includes at least one of the visible light band and the infrared light band. The sensing system of claim 9, wherein the light beam forms a first diffraction pattern after passing through the first diffraction structure, and forms a second diffraction pattern after passing through the second diffraction structure, wherein the first diffraction pattern includes multiple dot-shaped light spots, and the second diffraction pattern includes multiple striped light spots. The sensing system as described in claim 13, wherein the light source further includes a third emitting region, and the diffractive optical element further includes a third diffraction structure overlapping the third emitting region, wherein the first diffraction structure, the second diffraction structure, and the third diffraction structure are all different. The sensing system of claim 14, wherein the light beam forms a third diffraction pattern after passing through the third diffraction structure, the third diffraction pattern comprising a plurality of dot-shaped light spots, wherein the density of the plurality of dot-shaped light spots in the third diffraction pattern is less than the density of the plurality of dot-shaped light spots in the first diffraction pattern. The sensing system as described in claim 9, wherein the light source comprises at least one of a point-type vertical cavity surface-emitting laser, a linear vertical cavity surface-emitting laser, an edge-emitting laser, and a random-point vertical cavity surface-emitting laser.