Light projection device and optical module

Abstract

The utility model relates to the technical field of light detection, in particular to a light projection device and an optical module, and the light projection device comprises an illumination optical system, a light modulation element and a projection optical system. The illumination optical system is configured to enable emitted light to travel along a first preset light path; the light modulation element is configured to receive light emitted by the illumination optical system, modulate the light and generate modulated light, and the modulated light travels along a second preset light path; the projection optical system guides the modulated light to advance along a second preset light path; the projection optical system comprises a front lens group, a diaphragm and a rear lens group, and the rear lens group, the diaphragm and the front lens group are sequentially arranged along the advancing direction of the modulated light; and the focal length ratio of the front lens group to the rear lens group meets the condition that 0.2 < = fb / fd < = 0.4. According to the projection optical system of the light projection device, the aberration of the modulated light projected into the preset depth-of-field range is adjusted, so that the definition of the structured light pattern projected into the depth-of-field range is consistent under the condition that the expected light spot brightness is maintained.

Description

Technical Field

[0001] The present application relates to the technical field of optical detection, and particularly relates to a light projection device and an optical module. Background Art

[0002] With the continuous development of industry, the degree of industrial automation production is getting higher and higher, and the requirements for the quantity and quality of parts are also getting higher and higher. Therefore, the problems of precise and rapid measurement of the microscopic structure on the surface of parts need to be solved urgently. Traditional manual visual inspection has the disadvantages of low detection efficiency, high labor intensity, and the detection accuracy being affected by subjective factors of personnel. It is not suitable for large-scale automated production lines. As a currently highly accurate detection method, optics has been active in the field of automated detection.

[0003] Currently, for the detection of parts, not only two-dimensional texture information needs to be detected, but also height information is required. Therefore, three-dimensional detection technology is being more and more widely used. One three-dimensional detection technology is a three-dimensional reconstruction technology based on structured light 3D cameras with the principle of triangulation as the core. Such 3D sensors usually use one or two projectors combined with a camera. The projectors project structured light onto the object to be measured at an angle with the optical axis of the camera. The camera captures the structured light image of the object, uses moiré fringes to analyze the microscopic surface information, and then performs three-dimensional reconstruction to obtain the height image of the object, so as to reconstruct the surface topography of the object.

[0004] In order to obtain an accurate height image, it is required that the light spots projected onto the object to be measured meet certain clarity and uniformity within the required height range. Therefore, the object plane where the platform carrying the object to be measured is located, the principal plane of the optical system, and the projection image plane where the structured light modulation element is located should theoretically conform to the Scheimpflug theorem. Currently, in order to meet the corresponding depth of field, according to the common sense that the larger the depth of field, the smaller the aperture, the optical modules of light projection devices generally use small apertures. However, using small apertures will result in low brightness of the structured light projected onto each measured plane of the object to be measured, leading to weak adaptability of the device to the detection material. Moreover, under this technical route, the clarity of the structured light (such as stripes) projected within the depth of field plane will decrease to varying degrees compared with that under the standard working plane. The larger the deviation from the standard working plane, the more the clarity decreases, that is, the clarity consistency of the structured light pattern within the depth of field is poor. Summary of the Utility Model

[0005] The present application provides a light projection device and an optical module, which can solve the problem of poor clarity consistency of the structured light pattern within the depth of field.

[0006] To solve the above technical problems, the present application provides a light projection device, which includes an illumination optical system, a light modulation element, and a projection optical system. The illumination optical system is configured to emit light having at least one wavelength and make the emitted light travel along a first preset optical path;

[0007] The light modulation element is configured to receive the light emitted by the illumination optical system, modulate the light to generate modulated light, and the modulated light travels along a second preset optical path after exiting the light modulation element. The modulated light includes uniform light and / or structured light having at least one wavelength;

[0008] The projection optical system is configured to receive the modulated light, guide the modulated light to travel along the second preset optical path, and project the modulated light onto the object to be measured in a direction forming a first preset angle α with the object plane carrying the object to be measured. The projection object plane where the platform carrying the object to be measured is located, the principal plane of the projection optical system, and the projection image plane where the light modulation element is located conform to the Scheimpflug theorem; the projection optical system includes a front lens group, a diaphragm, and a rear lens group. The rear lens group, the diaphragm, and the front lens group are arranged on the second preset optical path in sequence along the traveling direction of the modulated light; the front lens group includes at least one lens, and the combined focal length of the front lens group is configured to be a focal length f b and the rear lens group includes at least one lens, and the combined focal length of the rear lens group is configured to be a focal length f d and the ratio of the focal lengths of the front lens group and the rear lens group satisfies: 0.2 ≤ f b / f d ≤ 0.4.

[0009] In one embodiment, the aperture of the diaphragm is 7.5 mm ± 0.5 mm.

[0010] In one embodiment, the surfaces of the lenses of the front lens group and the rear lens group closest to the diaphragm facing the diaphragm are concave surfaces.

[0011] In one embodiment, the focal length of the lens of the front lens group closest to the diaphragm is greater than or equal to -80, the focal length of the lens of the rear lens group closest to the diaphragm is less than or equal to -30, and the absolute value of the ratio of the focal length of the lens of the front lens group closest to the diaphragm to the focal length of the lens of the rear lens group closest to the diaphragm is greater than or equal to 0.375 and less than or equal to 2.6.

[0012] In one embodiment, the rear lens group includes a first positive lens, a second positive lens, a third positive lens, and a first negative lens arranged in sequence along the traveling direction of the modulated light; the front lens group includes a second negative lens, a fourth positive lens, and a third negative lens arranged in sequence along the traveling direction of the modulated light.

[0013] In one embodiment, the first negative lens and the third positive lens are formed into a first cemented lens through a cementing process; the air gap between the front lens group and the rear lens group is 15 mm, the air gap between the third negative lens and the fourth positive lens is 0.1 mm, the air gap between the fourth positive lens and the second negative lens is 0.1 mm, the air gap between the first cemented lens and the second positive lens is 0.1 mm, and the air gap between the second positive lens and the first positive lens is 0.1 mm.

[0014] In one embodiment, the focal length of the second negative lens is f5, and the focal length of the first cemented lens is f 34 , f5 and f 34 Satisfy:

[0015] (-80 ≤ f5) and (f 34 ≤ -30) and (0.375 ≤ |f5 / f 34 | ≤ 2.6),

[0016] wherein, f5 is the focal length of the second negative lens, and f 34 is the focal length of the first cemented lens.

[0017] In one embodiment, the rear lens group includes a fifth positive lens, a sixth positive lens, a seventh positive lens, and a fourth negative lens arranged in sequence along the traveling direction of the modulated light; the fourth negative lens and the seventh positive lens are formed into a second cemented lens through a cementing process; the front lens group includes a fifth negative lens, an eighth positive lens, a ninth positive lens, and a sixth negative lens arranged in sequence along the traveling direction of the modulated light;

[0018] wherein, the eighth positive lens and the fifth negative lens are formed into a third cemented lens through a cementing process, or the sixth negative lens and the ninth positive lens are formed into a fourth cemented lens through a cementing process.

[0019] In one embodiment, at least one of the lenses constituting the front lens group and the rear lens group is a positive lens, and the relative refractive index temperature coefficient of the positive lens satisfies:

[0020] -10.0×10 -6 ≤ dn / dt ≤ -3.0×10 -6 ,

[0021] wherein, dn / dt is the relative refractive index temperature coefficient of the positive lens.

[0022] In one embodiment, the plane where the optical modulation element is located and the optical axis of the projection optical system have a second preset angle β, and the value of the first preset angle α satisfies: 60° ≤ α ≤ 70°,

[0023] The value of the second preset angle β satisfies: 2.8° ≤ 90° - β ≤ 5.0°.

[0024] To solve the above technical problems, the present application provides an optical module, which includes a rear lens group, a front lens group, a diaphragm, and a first encapsulation structure. The rear lens group is used to receive the incident light; the front lens group is arranged downstream of the rear lens group along the optical path and is independently arranged relative to the rear lens group, and projects the light onto the object to be measured in a direction forming a first preset angle α with the object plane carrying the object to be measured; the combined focal length f b of the front lens group and the combined focal length f d of the rear lens group has a ratio of: 0.2 ≤ f b / f d ≤ 0.4; the diaphragm is arranged between the front lens group and the rear lens group; the first encapsulation structure encapsulates the front lens group, the diaphragm, and the rear lens group therein, so that the relative positions of the front lens group and the rear lens group can be fixed and maintained.

[0025] In the embodiment of the present application, through the design of the projection optical system, the focal lengths of the front lens group and the rear lens group cooperate to adjust the aberration of the modulated light projected within a preset depth of field centered on the standard working plane, so that the clarity of the structured light pattern (such as stripes) projected within the depth of field is consistent while maintaining the desired spot brightness. Thus, while the light projection device adopts a large aperture and high brightness, it can also ensure that the clarity of the structured light pattern projected onto the plane to be measured and within a certain range thereof is consistent. And because the spot brightness is relatively high, to a certain extent, the material adaptability problem is broadened. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic structural diagram of an optical detection sensor in an embodiment of the present application;

[0027] Figure 2 is Figure 1 a schematic structural diagram of the light projection device and the image acquisition device in;

[0028] Figure 3 is Figure 2 a schematic structural diagram of the RTIR prism (compound prism) and the light modulation element in;

[0029] Figure 4 is a schematic diagram of an optical system conforming to the Scheimpflug theorem;

[0030] Figure 5 is Figure 2 a schematic diagram of the optical system of the object plane, the RTIR prism, and the light modulation element in;

[0031] Figure 6 is an optical system diagram of the working object plane, the front depth of field plane, and the rear depth of field plane in the object space, and the front focal depth plane, the image plane, and the rear focal depth plane in the image space;

[0032] Figure 7Optical system diagram of the optical modulation element, projection optical system, and object plane provided by an embodiment of the present application;

[0033] Figure 8 , 9 , 10 are respectively the Ray Fan curves on the optical axis at positions 1′, 2′, and 3′ in the image space of the projection optical system when the aberration of the projection optical system is not adjusted;

[0034] Figure 11 , 12 , 13 are respectively the Ray Fan curves on the optical axis at positions 1′, 2′, and 3′ in the image space of the projection optical system when the aberration of the projection optical system is adjusted;

[0035] Figure 14 , 15 , 16 are respectively the MTF curves of the projection optical system at positions 1′, 2′, and 3′ in the image space when the aberration of the projection optical system is not adjusted;

[0036] Figure 17 , 18 , 19 are respectively the MTF curves of the projection optical system at positions 1′, 2′, and 3′ in the image space when the aberration of the projection optical system is adjusted;

[0037] Figure 20 , 21 , 22 are respectively the encircled energy curves of the projection optical system at positions 1′, 2′, and 3′ in the image space when the aberration of the projection optical system is not adjusted;

[0038] Figure 23 , 24 , 25 are respectively the encircled energy curves of the projection optical system at positions 1′, 2′, and 3′ in the image space when the aberration of the projection optical system is adjusted;

[0039] Figure 26 is the distortion curve of the projection optical system when the aberration of the projection optical system is adjusted;

[0040] Figure 27 is the relative illumination curve of the projection optical system when the aberration of the projection optical system is adjusted. Detailed implementation manner

[0041] The present application will be further described in detail below with reference to the specific embodiments in conjunction with the accompanying drawings. Similar elements in different embodiments are denoted by related similar element numbers. In the following embodiments, many details are described to enable a better understanding of the present application. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, or methods. In some cases, some operations related to the present application are not shown or described in the specification, in order to avoid the core part of the present application being overwhelmed by excessive description. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0042] In addition, the features, operations, or characteristics described in the specification can be combined in any appropriate manner to form various embodiments, and the operation steps involved in each embodiment can also be reordered or adjusted in a manner obvious to those skilled in the art. Therefore, the specification and the drawings are only for clearly describing a certain embodiment, and do not mean that they are essential components and / or sequences.

[0043] The serial numbers assigned to the components in this document, such as "first", "second", etc., are only used to distinguish the described objects, and do not have any sequential or technical meaning. The "connection" and "coupling" mentioned in the present application, unless otherwise specified, both include direct and indirect connection (coupling).

[0044] As Figure 1 shown, the optical detection sensor 100 includes at least one light projection device 11, an image acquisition device 12, an arithmetic processing device 13, and a controller 14. In some embodiments, the optical detection sensor 100 further includes one or more of a memory 15, a communication unit 16, and an input / output device 17, which will be described separately below.

[0045] The light projection device 11 is used to project modulated light onto the object to be measured (such as the object to be detected S1 shown in the figure). The modulated light can be, for example, uniform light of a single wavelength (such as red light), or uniform light mixed with multiple wavelengths (such as white light), or structured light with a preset pattern. The structured light can be, for example, a stripe image in digital form, and the stripe image can be preset by the user and transmitted to the light projection device 11 through the controller 14 for projection. Here, the stripe image includes a phase-shifted image and / or a Gray code image. The light projection device 11 can have one or two, for example. In one embodiment, the light projection device 11 projects the modulated light onto the object to be detected S1 in an inclined manner, such that there is a preset acute angle α between the optical axis and the object plane OP (i.e., the platform for carrying the object to be measured in the actual application scenario).

[0046] The image acquisition device 12 is used to collect the diffuse reflection modulated light formed after the modulated light projected by the light projection device 11 is diffusely reflected by the object to be detected S1. In one embodiment, the image acquisition device 12 includes a light receiving system and an imaging system. The light receiving system can be at least one set of lenses. The optical axis of the light receiving system is perpendicular to the object plane OP for carrying the object to be measured. After being irradiated by the modulated light, the object to be detected S1 generates diffuse reflection with a spatial angular distribution. The light receiving system receives the diffuse reflection modulated light within at least a partial angle range and guides the diffuse reflection modulated light to the imaging system. The imaging system includes other imaging elements such as a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) image sensor. The imaging system generates a measurement image based on the diffuse reflection modulated light within a partial angle in the spatial angle. The measurement image can be height image data reflecting the height information of the object to be measured and / or texture image data reflecting the texture information of the object to be measured. In the measurement space, there is a certain angle between the incident light rays of the image acquisition device 12 and the outgoing light rays of the light projection device 11, so that the image acquisition device 12 can capture the deformation pattern of the fringe image on the surface of the object to be detected S1.

[0047] The operation processing device 13 is connected to the image acquisition device 12, and is used to obtain the measurement image and process the measurement image by using a preset algorithm to obtain the height information and / or texture information of the object to be detected S1. The algorithm for the operation processing device 13 to process the measurement image can adopt existing technical means or technical means that will appear in the future, as long as the height information and / or texture information of the object to be detected S1 can be obtained.

[0048] The controller 14 is respectively connected to the light projection device 11 and the image acquisition device 12, and is used to control the actions of both. The controller 14 controls the light projection device 11 to emit light and generate modulated light according to the parameters preset by the user and / or the structured light pattern, etc., and projects the modulated light onto the object plane OP to irradiate the object to be detected S1. When there are two sets of light projection devices 11 and the modulated light emitted by the two sets of light projection devices 11 has a certain time sequence, the controller 14 also controls the actions of the two sets of light projection devices 11 according to a certain time sequence relationship. The controller 14 also controls the image acquisition device 12 to capture the image of the object to be detected S1 after being irradiated by the modulated light according to the imaging parameters preset by the user. When there is a certain time sequence between the shooting action of the image acquisition device 12 and the light projection device 11, for example, the light projection device 11 first emits uniform light, the image acquisition device 12 captures the image of the object to be detected S1 after being irradiated by the uniform light, and then the light projection device 11 emits structured light, and the image acquisition device 12 captures the image of the object to be detected S1 after being irradiated by the structured light, then the controller 14 also controls the actions of the light projection device 11 and the image acquisition device 12 according to the preset shooting time sequence by the user.

[0049] In some embodiments, the controller 14 is also connected to the arithmetic processing unit 13 to control the arithmetic processing unit 13 to perform arithmetic operations and processing on the measurement images generated by the image acquisition device 12, or to control the arithmetic processing unit 13 to perform arithmetic operations and processing on the measurement images generated by the image acquisition device 12 according to user settings. In some embodiments, the arithmetic processing unit 13 can automatically perform arithmetic operations and processing after the measurement images are generated by the image acquisition device 12. In some embodiments, the controlled arithmetic processing unit 13 can store the measurement image data generated by the image acquisition device 12 in the memory 15, and the controller 14 can control the arithmetic processing unit 13 to read data from the memory 15 for arithmetic operations and processing according to user input or settings.

[0050] The memory 15 is respectively connected to the arithmetic processing unit 13 and the controller 14, and is used for storing the measurement image data so that the controller 14 can read the measurement image data (such as texture image data and / or height image data) at any time. The memory 15 is also connected to the communication unit 16, and is used for saving the information received by the communication unit 16, or sending the saved information through the communication unit 16.

[0051] The communication unit 16 is connected to the controller 14 and the memory 15. In a specific embodiment, the communication unit 16 adopts a communication protocol such as RS232, USB, Bluetooth, or WIFI, and can send the measurement image data processed by the arithmetic processing unit 13 and the data or information saved in the memory 15 to the host computer according to the protocol format, and can also receive the setting instructions and information sent by the host computer according to the protocol format and transmit them to the controller 14 and / or the memory 15.

[0052] In some embodiments, the optical detection sensor 100 further includes an input / output device 17. The input / output device 17 is connected to the controller 14 and is used for setting and / or displaying measurement parameters, measurement processes, and measurement results. The input / output device 17 can implement the input function of instructions, parameters, settings, and / or information through means such as a keyboard, buttons, keys, soft keys, voice, and gestures, and can implement the display function through any type of display. Preferably, a display with a touch function can be used to facilitate human-computer interaction between the user and the controller 14.

[0053] As Figure 2 shown, in the embodiments of the present application, as Figure 2 shown, a light projection device 11 is provided. The light projection device 11 includes an illumination optical system 11a, a light modulation element 115, and a projection optical system 11b.

[0054] The illumination optical system 11a is configured to emit light having at least one wavelength and cause the emitted light to travel along a first preset optical path. In one embodiment, the illumination optical system 11a includes a light source 111, a shaping lens group 112, a mirror 113, and a prism 114. One or more light sources 111 may be provided, and each light source 111 emits light of one wavelength. When only one light source 111 is controlled to emit light, the light emitted by the illumination optical system 11a is monochromatic light. When multiple light sources 111 emit light of multiple wavelengths, the light emitted by the illumination optical system 11a is mixed light. The shaping lens group 112 is configured to be disposed on the optical path for collecting the light emitted by the light source 111, converging and shaping the diverging light, and emitting a converging light beam or a parallel light beam. The mirror 113 is disposed downstream of the shaping lens group 112 along the optical path and reflects the light emitted by the shaping lens group 112 to the prism 114. In some embodiments, as Figure 2 and Figure 3 shown, the mirror 113 may not be provided, but the light emitted by the shaping lens group 112 is directly projected onto the first side surface m1 of the prism 114. Alternatively, a lens with other functions may be used to replace the shaping lens group 112, or other lenses with other functions may be provided upstream (closer to the light source 111) or downstream (farther from the light source 111) of the shaping lens group 112 along the optical path. As Figure 3 shown, the prism 114 may be an RTIR (reflection total internal refraction) prism, that is, the RTIR prism includes a first side surface m1, an intermediate interface m2, and a second side surface m3. The interface m2 transmits the light incident from the first side surface m1 and totally reflects the light incident from the second side surface m3. After the light beam is incident on the RTIR prism, it is transmitted and refracted by the RTIR prism and projected onto the light modulation element 115. The optical path from the light source 111 to the prism 114 is called the first preset optical path, and the first preset optical path may be a straight line type or may become a bent optical path after passing through the mirror 113 and / or the prism 114.

[0055] The light modulation element 115 can be a digital micromirror device (DMD) or a liquid crystal on silicon (LCOS) element, which is configured to receive the light transmitted through the prism 114, that is, configured to receive the light emitted by the illumination optical system 11a, modulate the light emitted by the illumination optical system 11a, and generate modulated light. The modulated light includes uniform light and / or structured light of at least one wavelength. The uniform light can be monochromatic light or mixed light, and the structured light can be a preset digital bar code image. After the modulated light exits from the light modulation element 115, it travels along a second preset optical path, enters the projection optical system 11b, and is guided by the projection optical system 11b to be projected onto the platform carrying the object to be measured. In one embodiment, the modulated light emitted by the light modulation element 115 first enters the second side surface m3 of the prism 114 along the second preset optical path. After the modulated light is reflected by the interface m2 of the prism 114, it continues to travel along the preset second preset optical path and enters the projection optical system 11b. In this case, the second preset optical path forms a bent optical path after being reflected by the prism 114. The propagation route of light in the RTIR prism is as Figure 3 shown. In some embodiments, the positions of the light modulation element 115 and the RTIR prism are set, in cooperation with the mirror 113, such that the direction of the structured light reflected by the RTIR prism is opposite to the direction of the light emitted by the shaping lens group 112, so that the overall optical path of the light projection device 11 is in a folded-back form, making the structure of the light projection device 11 more compact, and thus the miniaturization of the sensor can be achieved. Of course, those skilled in the art can understand that in an embodiment without using the prism 114, the modulated light emitted by the light modulation element 115 directly enters the projection optical system 11b along the second preset optical path. In this case, the second preset optical path is a straight line. The bent second preset optical path can make the light projection device 11 have a smaller volume compared to the straight-line second preset optical path, achieving miniaturization and portability.

[0056] The projection optical system 11b is configured to receive the modulated light, guide the modulated light to travel along the second preset optical path, and project the modulated light onto the object to be measured in a direction forming a first preset angle α with the object plane carrying the object to be measured, that is, the modulated light irradiates the object plane in an inclined manner.

[0057] When implementing the folded-back optical path, in order to meet the requirement that all parts of the light spot projected by the projection optical system 11b onto the object plane OP carrying the object to be measured have consistent clarity, the object plane OP, the main plane of the optical system, and the image plane theoretically need to conform to the Scheimpflug theorem. As Figure 4 shown, that is, it is required that the projection optical system 11b satisfies the following relationship:

[0058] tan[π / 2 - α] / tan[π / 2 - β`]=M,

[0059] Wherein, α is the angle between the object plane OP and the optical axis of the projection optical system 11b (hereinafter referred to as the angle α), β` is the angle between the projection image plane where the mirror light modulation element 115` is located and the optical axis of the projection optical system 11b (hereinafter referred to as the angle β`), π / 2 - β` is called the Scheimpflug angle or the tilt angle of the light modulation element, M is the magnification on the optical axis of the projection optical system 11b, and in this application, M is the magnification from the side of the object to be measured to the side of the light modulation element. For the light projection device 11 with an RTIR prism in this application, as Figure 5 shown, the object plane OP is the projection object plane where the platform for carrying the object to be measured is located. The modulated light projected by the light modulation element 115 is reflected by the RTIR prism. According to the law of reflection of light, the projection image plane where the light modulation element 115 is located is equivalent to the projection image plane where the mirror light modulation element 115` symmetric about the interface m2 is located, that is Figure 5 the projection image plane where the mirror light modulation element 115` shown by the thick dashed line in

[0060] is the projection image plane of the light modulation element 115. Thus, the angle between the platform carrying the object to be measured and the optical axis of the projection optical system 11b is α, and the angle between the light modulation element 115 and the optical axis of the projection optical system 11b is β, and the angle β is equal to the angle β`. Therefore, the extension lines of the projection object plane where the platform carrying the object to be measured is located, the principal plane of the projection optical system 11b, and the projection image plane where the light modulation element 115 is located intersect at a line and satisfy the Scheimpflug theorem. For the light projection device 11 without an RTIR prism and where the modulated light is not reflected by the RTIR prism, the second preset optical path is linear, and the image plane is directly the projection image plane where the light modulation element 115 is located. Figure 2 shown, OP is the standard working plane. In the traditional way, the spot of the structured light irradiated on the standard working plane OP after passing through the projection optical system 11b is the clearest. In order to meet the brightness requirement of the spot, the aperture of the projection optical system 11b is designed to be relatively large. In the case of a large aperture, the depth of field in the object space is relatively small, resulting in a decrease in the clarity of the spots on other detection planes far from the standard working plane OP. However, when the light projection device 11 and the image acquisition device 12 are used in combination to measure the three-dimensional information of the object to be measured, it is expected that the spots on each height plane of the object to be measured with a certain height can form structured light with the same contrast and clarity. Assume that the planes OP’ and OP″ are two working planes within a certain range above and below the standard working plane OP (which can cover the height range of the object to be measured), that is, it is expected that the entire spots on each measurement plane within the range of the planes OP’ and OP″ can form structured light with the same contrast and clarity. Because only when structured light with the same contrast is formed on each surface of the object to be measured within the depth of field can the imaging optical path capture clear modulated light.

[0061] In addition, in order to meet the measurement depth of field range of the entire optical detection sensor 100, it is also required that the projection optical system 11b has a depth of field greater than that of the whole machine optical system, that is, it is required that the projection optical system 11b has a relatively large depth of field.

[0062] However, according to the traditional optical design concept, to obtain a large depth of field, it is necessary to reduce the aperture of the projection optical system 11b, resulting in that the light energy cannot be fully projected onto the object plane, thereby causing the measured brightness on the measurement plane in the object space to become lower.

[0063] It can be seen that the large depth of field and high brightness indexes of the above projection optical system 11b are contradictory to each other.

[0064] To solve this contradiction, the inventors of the present application have conducted in-depth research. To illustrate the research process, four concepts of circle of confusion diameter, depth of focus, depth of field, and circle of enclosing energy are introduced.

[0065] The circle of confusion diameter describes that on the object plane or the image plane, after an ideal point is imaged by an optical system, due to the diffraction limit of the optical system, it becomes a circle of confusion, and the size of this circle of confusion is called the circle of confusion diameter. Each optical system always cannot form an ideal optical system due to its actual light passing aperture, and an ideal point will always be restricted by this and form a circle of confusion. The allowable size of the circle of confusion depends on the resolution ability of the sensor system. For an optical system including a digital camera, the circle of confusion diameter is usually related to the size of a single pixel of the sensor. To ensure that the circle of confusion diameter does not affect the clarity of the optical system, generally it is required that the circle of confusion diameter does not exceed the size of 2 pixels, that is, the circle of confusion diameter satisfies the following formula:

[0066] c = 2×p,

[0067] where c is the allowable circle of confusion diameter and p is the size of a single pixel.

[0068] And the limit of the circle of confusion diameter that the optical system itself can reach is the Airy disk diameter, and the formula for calculating the Airy disk diameter is:

[0069] δ = 1.22×λ / (NA),

[0070] where δ is the Airy disk diameter, λ is the wavelength of light, and NA is the numerical aperture.

[0071] The depth of focus describes the axial distance in the image plane space to maintain clear imaging on the image plane. The depth of field describes the axial distance in the object plane space to maintain clear imaging on the object plane.

[0072] The encircled energy is defined as the ratio of the light energy contained within the diameter of the circle of confusion in the image plane after passing through an optical system to the total energy emitted from a point in the object plane. Therefore, to ensure that an optical system can form a clear image, it is first necessary to ensure that the encircled energy within the allowable diameter of the circle of confusion of the system is high enough, so as to prevent the light energy emitted from a point in the object plane from being dispersed outside the allowable diameter of the circle of confusion after passing through the optical system.

[0073] According to the traditional optical system design concept, an optical system is usually made as close as possible to an ideal optical system. That is, during the optical system design stage, most of the light energy emitted from a point in the object plane is made to pass through the optical system and the light energy is concentrated within the diameter of the Airy disk in the image plane.

[0074] If analyzed using an ideal optical system, as Figure 6 described, the plane where position 1 is located is the front depth of field plane, the plane where position 3 is located is the rear depth of field plane, and the plane where position 2 is located is the working object plane. Similarly, positions 1′, 2′, and 3′ represent the front focal depth plane, the image plane, and the rear focal depth plane respectively. When the aperture of the optical system is larger, the distance from position 1′ to position 3′ will become shorter, the focal depth will become shallower, and by inverse calculation based on the magnification of the optical system, the depth of field will also become shallower.

[0075] Therefore, to obtain a large depth of field, a large focal depth must first be obtained. The focal depth is proportional to the allowable diameter of the circle of confusion of the system. The allowable diameter of the circle of confusion depends on the resolution ability of the optical system. The higher the resolution ability requirement, the smaller the allowable diameter of the circle of confusion. Conversely, the lower the resolution ability requirement, the larger the allowable diameter of the circle of confusion.

[0076] Through the above analysis, the inventor realized that if the resolution ability requirement of an optical system is not that high, it means that the allowable diameter of the circle of confusion of the system will not be too small. Then, during the optical system design stage, it is not necessary to design most of the light energy emitted from a point in the object plane to be concentrated within the diameter of the Airy disk. Instead, it only needs to be close to the allowable diameter of the circle of confusion, so that most of the light energy emitted from a point in the object plane is concentrated within this circle of confusion, and a relatively high encircled energy can be achieved. According to this analysis, the problem is transformed into how to diffusely distribute the light energy at position 2′ within the allowable diameter of the circle of confusion, and at the same time, concentrate the light energy at positions 1′ and 3′ within the allowable diameter of the circle of confusion, so that the light energy distributions at the planes where positions 1′, 2′, and 3′ are located are close to being consistent, and the sharpness is also close to being consistent. Similarly, as Figure 2 shown, the objective of this application is to concentrate the light energy in the OP’ and OP″ planes within the allowable diameter of the circle of confusion, and diffusely distribute the light energy in the OP plane within the allowable diameter of the circle of confusion. When the aperture of the optical system is large, it will not affect the reduction of the focal depth, thus achieving the objective of increasing the focal depth and ultimately achieving the goal of increasing the depth of field.

[0077] The optical system involved in this application belongs to the projection optical system 11b, which is used to project the pattern of the light modulation element 115 (DMD) onto the surface of the object to be measured. The size of a single micromirror unit of the commonly used DMD is 7.6μm×7.6μm, and the allowable diameter of the circle of confusion is 15.2μm. Converted to the required Nyquist frequency, it is 66 cycles / mm. In order to project all the light energy reflected by the DMD onto the object surface, the F number of the projection optical system 11b is set to 2.4, and the diameter of its Airy disk is about 3μm, which is much smaller than the allowable diameter of the circle of confusion of the optical system of this application. Therefore, the above idea can be used to improve the depth of field.

[0078] Therefore, the concept of this application is to adopt a large aperture to increase the brightness of the projected modulated light spot, and based on this, through the design of the projection optical system, adjust the aberration of the modulated light projected within the preset depth of field centered on the standard working plane, so that the aberration on the standard working plane and the planes near it becomes larger, and the aberration of the working plane at a certain distance from the standard working plane becomes smaller. Thus, the light energy on the standard working plane and the planes near it is diffusely distributed within the allowable diameter of the circle of confusion, and at the same time, the light energy of the working plane at a certain distance from the standard working plane is concentrated and distributed within the allowable diameter of the circle of confusion. As a result, the light energy distribution within all the detection planes within the expected range can be made close to uniform, and the clarity can also be made close to uniform, which is equivalent to increasing the depth of field.

[0079] In one embodiment, as Figure 7 shown, the projection optical system 11b includes a front lens group 21, a rear lens group 22, and a diaphragm 23. The rear lens group 22, the diaphragm 23, and the front lens group 21 are arranged on the second preset optical path in sequence along the traveling direction of the modulated light. The rear lens group 22 receives the incident modulated light, for example, the modulated light emitted by the light modulation element 115 and reflected by the prism 114. The front lens group 21 is arranged on the second preset optical path and is located downstream of the rear lens group 22 to receive the modulated light emitted by the rear lens group 22. The front lens group 21 is used to project the modulated light onto the object to be measured in a direction forming a first preset angle α with the object plane carrying the object to be measured.

[0080] Among them, the front lens group 21 includes at least one lens, and the combined focal length of the front lens group 21 is configured as a focal length f b , the rear lens group 22 includes at least one lens, and the combined focal length of the rear lens group 22 is configured as f d , and the focal length ratio of the front lens group 21 and the rear lens group 22 satisfies: 0.2≤f b / f d ≤0.4. By adjusting the aberration of the front lens group 21 and the rear lens group 22, the focal length ratio of the two is adjusted, so that the clarity of the structured light pattern projected within the depth of field is consistent.

[0081] In the embodiments of the present application, through the design of the projection optical system 11b, the focal lengths of the front lens group 21 and the rear lens group 22 cooperate to adjust the aberration of the modulated light projected within a preset depth of field centered on the standard working plane, so that the clarity of the structured light pattern (such as stripes) projected within the depth of field is consistent while maintaining the desired spot brightness. Thus, while the light projection device 11 adopts a large aperture and high brightness, it can also ensure that the clarity of the structured light pattern projected onto the plane to be measured and within a certain range thereof is consistent. Moreover, due to the relatively high spot brightness, the material adaptability problem is broadened to a certain extent.

[0082] In one embodiment, in order to maintain the desired spot brightness, the aperture of the diaphragm 23 is 7.5 mm ± 0.5 mm, so that the light projection device 11 of the present application realizes a large aperture and high brightness. While the present application adopts a large aperture and high brightness, it is necessary to ensure that the clarity of the structured light pattern projected onto the plane to be measured and within ±5 mm is consistent.

[0083] In one embodiment, the surfaces of the lenses of the front lens group 21 and the rear lens group 22 closest to the diaphragm 23 facing the diaphragm 23 are both concave surfaces for correcting off-axis aberration. For example Figure 7 as shown Figure 7 in the embodiment of, the lens of the front lens group 21 closest to the diaphragm 23 is the second negative lens 211, and the lens of the rear lens group 22 closest to the diaphragm 23 is the first cemented lens composed of the first negative lens 225 and the third positive lens 224. The surfaces of the second negative lens 211 and the first cemented lens facing the diaphragm 23 are both concave surfaces.

[0084] In one embodiment, the focal length of the lens of the front lens group 21 closest to the diaphragm 23 is greater than or equal to -80, the focal length of the lens of the rear lens group 22 closest to the diaphragm 23 is less than or equal to -30, and the absolute value of the ratio of the focal length of the lens of the front lens group 21 closest to the diaphragm 23 to the focal length of the lens of the rear lens group 22 closest to the diaphragm 23 is greater than or equal to 0.375 and less than or equal to 2.6. For example, specifically, in Figure 7 the embodiment of, the lens of the front lens group 21 closest to the diaphragm 23 is the second negative lens 211, and the lens of the rear lens group 22 closest to the diaphragm 23 is the first cemented lens composed of the first negative lens 225 and the third positive lens 224. Among them, the focal length of the second negative lens 211 is f5, and the focal length of the first cemented lens is f 34 , f5 and f 34 satisfy:

[0085] (-80 ≤ f5) and (f 34 ≤ -30) and (0.375 ≤ |f5 / f 34 | ≤ 2.6),

[0086] wherein, f5 is the focal length of the second negative lens 211, f34 is the focal length of the first cemented lens.

[0087] There are many forms of the optical architecture that can implement the concept of the present application. One specific embodiment is listed herein.

[0088] In this embodiment, the technical indicators of the optical system are as follows:

[0089] Magnification: 7.3X;

[0090] Projection ratio (orthographic projection): 1.64;

[0091] F#: 2.4;

[0092] Depth of field: ±5 mm;

[0093] Distortion: 0.2%;

[0094] Total optical length: 74.5 mm.

[0095] In one embodiment, as Figure 7 shown, the rear lens group 22 includes a first positive lens 222, a second positive lens 223, a third positive lens 224, and a first negative lens 225 arranged in sequence along the direction of modulated light travel. The front lens group 21 includes a second negative lens 211, a fourth positive lens 212, and a third negative lens 213 arranged in sequence along the direction of modulated light travel.

[0096] Specifically, the first positive lens 222 is a biconvex singlet lens with a thickness of 3.1 mm; the second positive lens 223 is a positive meniscus singlet lens with a thickness of 3.36 mm; the third positive lens 224 is a biconvex lens, and the first negative lens 225 is a biconcave lens; the third positive lens 224 and the first negative lens 225 form a first cemented lens through a cementing process. The thickness of the first cemented lens is 4.75 mm. The cemented lens can be centered at one time and complete the assembly of multiple lenses simultaneously, thereby reducing the number of centering times and assembly times of the lenses; the second negative lens 211 is a negative meniscus singlet lens with a thickness of 5.90 mm; the fourth positive lens 212 is a biconvex singlet lens with a thickness of 2.91 mm; the third negative lens 213 is a negative meniscus singlet lens with a thickness of 1.53 mm.

[0097] Among them, the air gap between the front lens group 21 and the rear lens group 22 is 15 mm, the air gap between the third negative lens 213 and the fourth positive lens 212 is 0.1 mm, the air gap between the fourth positive lens 212 and the second negative lens 211 is 0.1 mm, the air gap between the first cemented lens and the second positive lens 223 is 0.1 mm, and the air gap between the second positive lens 223 and the first positive lens 222 is 0.1 mm.

[0098] In this embodiment, along the light propagation direction of the second preset optical path, the absolute value of the curvature radius of the first surface of the first positive lens 222 is 75.27 mm, and the absolute value of the curvature radius of the second surface is 31.47 mm; in this embodiment, along the light propagation direction of the second preset optical path, the absolute value of the curvature radius of the first surface of the second positive lens 223 is 16.98 mm, and the absolute value of the curvature radius of the second surface is 112.89 mm; in this embodiment, along the light propagation direction of the second preset optical path, the absolute value of the curvature radius of the first surface of the first cemented lens group is 14.6 mm, the absolute value of the curvature radius of the second surface is 79.3 mm, and the absolute value of the curvature radius of the third surface is 15.98 mm; in this embodiment, along the light propagation direction of the second preset optical path, the absolute value of the curvature radius of the first surface of the second negative lens 211 is 5.89 mm, and the absolute value of the curvature radius of the second surface is 9.62 mm; in this embodiment, along the light propagation direction of the second preset optical path, the absolute value of the curvature radius of the first surface of the fourth positive lens 212 is 30.03 mm, and the absolute value of the curvature radius of the second surface is 47.7 mm; in this embodiment, along the light propagation direction of the second preset optical path, the absolute value of the curvature radius of the first surface of the third negative lens 213 is 13.18 mm, and the absolute value of the curvature radius of the second surface is 41.56 mm.

[0099] In other embodiments, the rear lens group 22 may include a fifth positive lens, a sixth positive lens, a seventh positive lens, and a fourth negative lens sequentially arranged along the traveling direction of the modulated light; the fourth negative lens and the seventh positive lens are formed into a second cemented lens through a cementing process; the front lens group 21 includes a fifth negative lens, an eighth positive lens, a ninth positive lens, and a sixth negative lens sequentially arranged along the traveling direction of the modulated light;

[0100] The eighth positive lens and the fifth negative lens are formed into a third cemented lens through a cementing process, or the sixth negative lens and the ninth positive lens are formed into a fourth cemented lens through a cementing process. This application does not impose special restrictions on the number and combination of lens groups in the projection optical system 11b.

[0101] In addition, the rear lens group 22 may further include a composite equivalent prism 221. The composite equivalent prism 221 is disposed on the second preset optical path and upstream of the first positive lens 222. The thickness T of the composite equivalent prism 221 is the equivalent thickness of the prism 114, which represents the total optical path of the light beam passing through the composite prism after being reflected by the light modulation element 115. Among them, T satisfies: 16 mm ≤ T ≤ 28 mm.

[0102] In one embodiment, at least one of the component lenses of the projection optical system 11b is made of a special material, so as to ensure that the clarity of the structured light projected by the projection optical system 11b remains unchanged at different operating temperatures, that is, at least one of the lenses forming the front lens group 21 and the rear lens group 22 is a positive lens, and the relative refractive index temperature coefficient of the positive lens satisfies:

[0103] -10.0×10 -6 ≤dn / dt≤ -3.0×10 -6 ,

[0104] Wherein, dn / dt is the temperature coefficient of the relative refractive index of the positive lens.

[0105] In one embodiment, the plane where the light modulation element 115 is located and the optical axis have a second preset angle β, and the value of the first preset angle α satisfies: 60° ≤ α ≤ 70°, and the value of the second preset angle β satisfies: 2.8° ≤ 90° - β ≤ 5.0°.

[0106] In the above embodiments, all lenses are rotationally symmetric about the principal optical axis. The projection optical system 11b does not use optical glass with a high refractive index to avoid the strong absorption of the optical material in the blue light band and ensure the overall projection efficiency of the projection optical system 11b.

[0107] Please refer to Figure 6 、 Figures 8 - 13 wherein, Figure 8 、 Figure 9 and Figure 10 are respectively the ray fan diagrams (Ray Fan curves) of the optical system on the optical axes in the image spaces 1′, 2′, and 3′ when the aberration of the projection optical system is not adjusted; Figure 11 、 Figure 12 and Figure 13 are respectively the Ray Fan curves on the optical axes in the image spaces 1′, 2′, and 3′ when the projection optical system 11b of the above embodiment is adopted. Wherein, the Ray Fan curve is usually used to analyze the aberration distribution of light rays in the optical system. In Figures 8 - 13 , the abscissa is the normalized pupil coordinate, usually labeled as Px or Py, representing the position of the light ray on the entrance pupil, and the ordinate is the lateral aberration, usually labeled as ex or ey, representing the deviation between the actual landing point of the light ray on the image plane and the ideal image point (Gaussian image point). Among them, the different color curves of the RanFan curve represent different wavelengths.

[0108] As Figures 14 - 19 shown, Figure 14 、 Figure 15 and Figure 16 are respectively the MTF curves of the optical system without aberration adjustment of the projection optical system in the image spaces 1′, 2′, and 3′, Figure 17 、 Figure 18 、 Figure 19They are respectively the MTF curves of the image space 1', 2', and 3' when the projection optical system 11b of the above embodiment is used, wherein the MTF curve is the modulation transfer function, and the vertical coordinate OTF modulus OTF is the optical transfer function. The vertical lines of different colors of the MTF curve represent different field points, the dotted line represents the meridian under a certain field point, and the solid line represents the sagittal line under a certain field point.

[0109] like Figures 20 - 25 As shown, Figure 20 , Figure 21 and Figure 22 are the enclosing circle energy curves of the optical system in the image space 1′, 2′, and 3′ when the projection optical system is not adjusted for aberration, Figure 23 , Figure 24 and Figure 25 They are respectively the enclosing circle energy curves in the image space 1', 2', 3' when the projection optical system 11b of the above embodiment is adopted, wherein the vertical lines of different colors in the enclosing circle energy curve represent different viewing points.

[0110] from Figure 8 , Figure 10 It can be seen from the Ray Fan curve that when the projection optical system is not adjusted for aberration, the primary aberration at position 1′ and position 3′ is too large, such as Figure 14 and Figure 16 As shown in FIG. 1 , the primary aberration is too large so that the MTF curves of position 1′ and position 3′ are directly cut off at 66 cycles / mm, while Figure 9 As shown in FIG. 1 , when the projection optical system is not adjusted for aberration, the aberration at position 2′ is relatively ideal, as shown in FIG. Figure 15 As shown, under ideal aberration conditions, the contrast of the MTF curve at position 2′ at 66 cycles / mm is better than 0.7.

[0111] It can be seen from the enclosing circle energy curve when the projection optical system is never adjusted for aberration that Figure 21 As shown in Figure 2, the optical energy concentration at position 2′ within the 15.2 μm diffusion circle diameter is close to 100%, while Figure 20 and Figure 22 As shown, the optical energy concentration within the same diameter of the confusion circle at positions 1′ and 3′ is less than 50%. In summary, therefore, when the projection optical system is not adjusted for aberration, positions 1′ and 3′ are not sufficient to project a single micromirror clearly, and the spatial frequency required at position 2′ is much higher than the spatial frequency required for a single micromirror to form a clear image.

[0112] In the solution of the projection optical system 11b of the above embodiment, certain aberrations are introduced at position 2', while the primary aberrations at positions 1' and 3' are reduced. As can be seen from the Ray Fan curve of the projection optical system 11b of the above embodiment, as Figure 12 shown, the aberrations at position 2' increase, as Figure 11 and Figure 13 shown, the primary aberrations at positions 1' and 3' are effectively controlled. Refer to Figures 17 - 19 . Controlling the primary aberrations makes the contrast of the MTF curves at positions 1', 2', and 3' close to 0.3 at 66 cycles / mm. As can be seen from the encircled energy curve of the projection optical system 11b of the above embodiment, as Figures 23 - 25 shown, the optical energy concentration within a 15.2 μm circle of confusion diameter at positions 1', 2', and 3' all reaches more than 90%. Therefore, it can be proved that the projection optical system 11b of the above embodiment can clearly project a single micromirror at positions 1', 2', and 3'. Therefore, after using the projection optical system 11b of the present application, the depth of focus of the optical system is significantly improved, so that the final depth of field is also greatly improved, meeting the usage requirements.

[0113] In addition, the close focusing distance of the projection optical system 11b of the present application is 118 mm, and the positive projection ratio is 1.64. Therefore, while realizing the basic functions, the projection optical system of this embodiment has a smaller spatial size.

[0114] Since the projection optical system 11b is applied to industrial inspection scenarios, the distortion needs to be strictly controlled. As Figure 26 shown, the distortion of the projection optical system 11b satisfies within an absolute value of 0.1%, which can ensure that the structured light projected by the projection optical system 11b will not be deformed within the measurement plane, ensuring the accuracy of the measurement data. Among them, the different color curves of the distortion curve represent different wavelengths.

[0115] As Figure 27 shown, the relative illuminance of the on-axis field of view and the off-axis field of view of the projected spot of the projection optical system 11b is basically the same, making the projected spot have better brightness uniformity and avoiding measurement system errors caused by uneven brightness.

[0116] In some embodiments, the solution of adjusting the aberration in the projection optical system 11b to make the clarity of the structured light pattern projected within the depth of field consistent is applicable not only to the field of the optical detection sensor 100, but also to other optical devices such as cameras and projectors. The optical module in these optical devices includes a front lens group, a rear lens group, a diaphragm, and a first encapsulation structure. The rear lens group is used to receive the incident light. The front lens group is arranged downstream of the rear lens group along the optical path and is independently arranged relative to the rear lens group, and projects the light onto the object to be measured in a direction forming a first preset angle α with the object plane carrying the object to be measured. The combined focal length f b of the front lens group and the combined focal length f d of the rear lens group has a ratio of: 0.2 ≤ f b / f d ≤ 0.4; the diaphragm is arranged between the front lens group and the rear lens group; the first encapsulation structure encapsulates the front lens group, the diaphragm, and the rear lens group therein to fix and maintain the relative positions of the front lens group and the rear lens group.

[0117] The above uses specific examples to elaborate on the present application, which is only used to help understand the present application and is not intended to limit the present application. For those skilled in the technical field to which the present application pertains, according to the idea of the present application, several simple deductions, deformations, or replacements can also be made.

Claims

1. A light projection device, characterized in that, Comprising: A lighting optical system configured to emit light having at least one wavelength and cause the emitted light to travel along a first preset optical path; A light modulation element configured to receive the light emitted by the lighting optical system, modulate the light to generate modulated light, and the modulated light travels along a second preset optical path after exiting the light modulation element, and the modulated light includes uniform light and / or structured light of at least one wavelength; A projection optical system, which is configured to receive the modulated light, guide the modulated light to travel along the second preset optical path, and project the modulated light onto the object to be measured in a direction forming a first preset angle α with the object plane carrying the object to be measured. The projection object plane where the platform carrying the object to be measured is located, the principal plane of the projection optical system, and the projection image plane where the optical modulation element is located conform to the Scheimpflug theorem; the projection optical system includes a front lens group, a diaphragm, and a rear lens group. The rear lens group, the diaphragm, and the front lens group are arranged on the second preset optical path and are arranged in sequence along the traveling direction of the modulated light; the front lens group includes at least one lens, and the combined focal length of the front lens group is configured to be a focal length f b , the rear lens group includes at least one lens, and the combined focal length of the rear lens group is configured to be a focal length f d , and the focal length ratio of the front lens group and the rear lens group satisfies: 0.2 ≤ f b / f d ≤ 0.

4.

2. The light projection device according to claim 1, characterized in that, The aperture of the diaphragm is 7.5 mm ± 0.5 mm.

3. The light projection device according to claim 1, wherein The surfaces of the lenses of the front lens group and the rear lens group closest to the diaphragm facing the diaphragm are concave.

4. The optical projection device according to claim 3, wherein, The focal length of the lens of the front lens group closest to the diaphragm is greater than or equal to -80, the focal length of the lens of the rear lens group closest to the diaphragm is less than or equal to -30, and the absolute value of the ratio of the focal length of the lens of the front lens group closest to the diaphragm to the focal length of the lens of the rear lens group closest to the diaphragm is greater than or equal to 0.375 and less than or equal to 2.

6.

5. The light projection device according to any one of claims 1-4, characterized in that, The rear lens group includes a first positive lens, a second positive lens, a third positive lens, and a first negative lens arranged in sequence along the traveling direction of the modulated light; the front lens group includes a second negative lens, a fourth positive lens, and a third negative lens arranged in sequence along the traveling direction of the modulated light.

6. The optical projection device according to claim 5, characterized in that, The first negative lens and the third positive lens are formed into a first cemented lens by a cementing process; the air gap between the front lens group and the rear lens group is 15 mm, the air gap between the third negative lens and the fourth positive lens is 0.1 mm, the air gap between the fourth positive lens and the second negative lens is 0.1 mm, the air gap between the first cemented lens and the second positive lens is 0.1 mm, and the air gap between the second positive lens and the first positive lens is 0.1 mm.

7. The light projection device according to claim 6, characterized in that, The focal length of the second negative lens is f5, and the focal length of the first cemented lens is f 34 , and f5 and f 34 satisfy: (-80 ≤ f5) and (f 34 ≤ -30) and (0.375 ≤ |f5 / f 34 | ≤ 2.6), Among them, f5 is the focal length of the second negative lens, and f 34 is the focal length of the first cemented lens.

8. The light projection device according to any one of claims 1-4, characterized in that, The rear lens group includes a fifth positive lens, a sixth positive lens, a seventh positive lens, and a fourth negative lens arranged in sequence along the traveling direction of the modulated light; the fourth negative lens and the seventh positive lens are formed into a second cemented lens by a cementing process; the front lens group includes a fifth negative lens, an eighth positive lens, a ninth positive lens, and a sixth negative lens arranged in sequence along the traveling direction of the modulated light; Wherein, the eighth positive lens and the fifth negative lens are formed into a third cemented lens by a cementing process, or the sixth negative lens and the ninth positive lens are formed into a fourth cemented lens by a cementing process.

9. The light projection device according to any one of claims 1-4, characterized in that, At least one of the lenses constituting the front lens group and the rear lens group is a positive lens, and the relative refractive index temperature coefficient of the positive lens satisfies: -10.0×10 -6 ≤dn / dt≤-3.0×10 -6 , Wherein, dn / dt is the relative refractive index temperature coefficient of the positive lens.

10. The light projection device according to any one of claims 1-4, characterized in that, The plane where the light modulation element is located and the optical axis of the projection optical system have a second preset angle β, and the value of the first preset angle α satisfies: 60° ≤ α ≤ 70°, The value of the second preset angle β satisfies: 2.8° ≤ 90° - β ≤ 5.0°.

11. An optical module, characterized in that, Comprising: A rear lens group for receiving the incidence of light; The front lens group is arranged downstream of the rear lens group along the optical path and is independently arranged relative to the rear lens group, and projects the light onto the object to be measured in a direction forming a first preset angle α with the object plane carrying the object to be measured; the combined focal length f of the front lens group b and the combined focal length f of the rear lens group d The ratio is: 0.2 ≤ f b / f d ≤ 0.4; A diaphragm, and the diaphragm is arranged between the front lens group and the rear lens group; The first encapsulation structure encapsulates the front lens group, the diaphragm, and the rear lens group therein, so that the relative positions of the front lens group and the rear lens group can be fixed and maintained.

Images