Laser stripe projection device

Abstract

The present invention relates to the field of laser projection, and specifically to a laser stripe projection device. The miniaturized laser stripe projection device can generate four-step phase-shifted laser interference stripe projection, and is applied to the three-dimensional shape measurement of objects in a microcavity. The device uses four laser diodes to collimate after spot expansion and then generate interference stripes by front and rear mirror reflection of a double-sided reflector. The four laser diodes correspond to four laser interference patterns with different phases. The shape measurement of a three-dimensional object can be performed using the principle of the four-step phase shift method. The device does not contain any moving parts and has good mechanical stability.

Description

Technical Field

[0001] The invention relates to the field of laser projection, in particular to a laser stripe projection device. Background Art

[0002] Laser 3D reconstruction is becoming more and more important in modern technology and real life. Through 3D reconstruction, spatial information can be quickly digitized, and it has important applications in 3D maps, 3D printing, virtual reality, visual medicine, and motion analysis. 3D reconstruction technology refers to the restoration and reconstruction of the 3D spatial geometry of 3D objects by measuring the depth data image of the 3D object. The general 3D reconstruction method is to obtain spatial encoding through structured light and obtain depth information through geometric relationships. Among them, the laser stripe method has great advantages in application due to its advantages such as simple structure, high resolution, and dynamic measurement. The measurement method used is called phase measuring profilometry (PMP).

[0003] The key to three-dimensional reconstruction using phase measurement profilometry is to achieve large-angle fringe projection and algorithm operation. Phase measurement profilometry requires projecting a sinusoidal grating pattern with different phases onto the surface of an object. The traditional method uses two laser beams to generate a sinusoidal grating image based on the interference principle, and the phase shift is achieved using a piezoelectric crystal. The speckle noise generated by laser interference will affect the light intensity distribution of the grating image. In addition, due to the nonlinear properties of piezoelectric crystals, phase shift is prone to errors. Some phase shifts are also achieved through stepper motor displacement platforms, and the accuracy of the system is inevitably affected by mechanical vibration.

[0004] The former often requires more complicated operations such as laser focusing and beam expansion, which often makes the front-end projection device larger, and the projection angle is usually no greater than 45 degrees. This is fully competent at long working distances, such as human motion tracking, where the working distance is in the order of meters and the object size is also in the order of meters. However, there are many difficulties in extremely narrow spaces (such as the oral cavity), and the working distance allowed under medical conditions is only in the order of centimeters.

[0005] The projection of the fringe pattern can also be controlled by a projector. However, due to the limitation of the projector, this projection method is difficult to achieve miniaturization and cannot meet the requirements of 3D reconstruction under medical conditions. These methods do not work in short-distance situations (such as intraoral projection).

[0006] Patent CN102261896A discloses a method for generating a high-precision numerical phase-shift grating image by computer programming and measuring the three-dimensional morphology of an object using the phase fringe method. The device used is a DLP projector. The required phase-shift grating image needs to be generated by computer programming and projected onto the surface of the object to be measured by the DLP projector. Limited by its structure and principle, the resulting projection space angle is not large and cannot be achieved at close range. Moreover, the DLP projector itself is expensive and bulky, and is not suitable for handheld devices. Summary of the invention

[0007] The technical problem solved by the present invention is to overcome the defects of the prior art and provide a laser stripe projection device. The device has the characteristics of simple structure, no moving parts, small size, etc., and can be used for laser three-dimensional projection modeling of objects in a narrow space.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A laser stripe projection device comprises a laser diode array, a collimating lens, a reflector, a micro camera and an object to be measured, wherein the collimating lens is fixedly mounted on one side of the laser diode array, the reflector is arranged on a side of the collimating lens away from the laser diode array, the laser diode array, the collimating lens and the reflector are all located at the same horizontal position, the micro camera is arranged at a position above the collimating lens and the reflector, and the object to be measured is arranged on a side between the collimating lens and the reflector opposite to the micro camera.

[0010] Preferably, the laser diode array includes laser diode 1, laser diode 2, laser diode 3 and laser diode 4, and laser diode 1, laser diode 2, laser diode 3 and laser diode 4 are linearly arranged in sequence from top to bottom.

[0011] Preferably, the diameters of the laser heads of the laser diode 1, the laser diode 2, the laser diode 3 and the laser diode 4 are all 6 mm.

[0012] Preferably, the focal length of the collimating lens is 7.5 cm.

[0013] Preferably, the reflector comprises a front end face and a rear end face, wherein the front end face and the rear end face are integrally formed.

[0014] Preferably, the reflectivity of the front end surface of the reflector is 38%, and the reflectivity of the rear end surface of the reflector is 100%.

[0015] Preferably, the divergence angle of the laser diode array is greater than 60 degrees, and the laser wavelength is 650 nm.

[0016] Preferably, the response band of the micro camera is consistent with the band of the laser diode array.

[0017] Preferably, the laser diode array and the micro camera are electrically connected to the clock controller via wires, and the laser diode array, the micro camera and the clock controller are electrically connected to an external or internal power supply via wires.

[0018] Preferably, the laser diode 1, laser diode 2, laser diode 3 and laser diode 4 are electrically connected to the clock controller and the built-in or external power supply through wires.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: the miniaturized laser stripe projection device can generate four-step phase-shifted laser interference stripe projection and be applied to the three-dimensional shape measurement of objects in microcavities. The present invention uses four laser diodes to collimate after spot expansion and then generate interference stripes by front and rear mirror reflection of a double-sided reflector. The four laser diodes correspond to four laser interference patterns with different phases. The shape measurement of three-dimensional objects can be performed using the principle of the four-step phase shift method. The device does not contain moving parts and has good mechanical stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the projection principle flow of the present invention;

[0021] Figure 2 It is a system block diagram of the present invention.

[0022] In the figure: 1 laser diode array, 1-1 laser diode one, 1-2 laser diode two, 1-3 laser diode three, 1-4 laser diode four, 2 collimating lens, 3 reflecting mirror, 3-1 front end surface, 3-2 rear end surface, 4 micro camera, 5 object to be measured. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] See also Figure 1-2 , the present invention provides a technical solution:

[0025] A laser stripe projection device comprises a laser diode array 1, a collimating lens 2, a reflector 3, a micro camera 4 and an object to be measured 5, wherein the collimating lens 2 is fixedly mounted on one side of the laser diode array 1, the reflector 3 is arranged on a side of the collimating lens 2 away from the laser diode array 1, the laser diode array 1, the collimating lens 2 and the reflector 3 are all located at the same horizontal position, the micro camera 4 is arranged between the collimating lens 2 and the reflector 3 and above the two, and the object to be measured 5 is arranged between the collimating lens 2 and the reflector 3 and on a side opposite to the micro camera 4.

[0026] As a technical optimization solution of the present invention, the laser diode array 1 includes laser diode 1-1, laser diode 2-1-2, laser diode 3-1-3 and laser diode 4-1-4, and laser diode 1-1, laser diode 2-1-2, laser diode 3-1-3 and laser diode 4-1-4 are arranged linearly from top to bottom.

[0027] As a technical optimization solution of the present invention, the laser heads of the laser diode 1-1, the laser diode 2 1-2, the laser diode 3 1-3 and the laser diode 4 1-4 all have a diameter of 6 mm.

[0028] As a technical optimization solution of the present invention, the focal length of the collimating lens 2 is 7.5 cm.

[0029] As a technical optimization solution of the present invention, the reflector 3 includes a front end face 3-1 and a rear end face 3-2, wherein the front end face 3-1 and the rear end face 3-2 are integrally formed.

[0030] As a technical optimization solution of the present invention, the reflectivity of the front end face 3 - 1 of the reflector 3 is 38%, and the reflectivity of the rear end face 3 - 2 of the reflector 3 is 100%.

[0031] As a technical optimization solution of the present invention, the divergence angle of the laser diode array 1 is greater than 60 degrees, and its laser wavelength is 650nm.

[0032] As a technical optimization solution of the present invention, the response band of the micro camera 4 is consistent with the band of the laser diode array 1.

[0033] As a technical optimization solution of the present invention, the laser diode array 1 and the micro camera 4 are electrically connected to the clock controller via wires, and the laser diode array 1, the micro camera 4 and the clock controller are electrically connected to an external or internal power supply via wires.

[0034] As a technical optimization solution of the present invention, the laser diode 1-1, laser diode 2 1-2, laser diode 3 1-3 and laser diode 4 1-4 are electrically connected to the clock controller and the built-in or external power supply through wires.

[0035] The present invention first uses a large divergence angle laser diode array 1, the divergence angle is greater than 60 degrees, and then uses a short focal length collimating lens 2 to collimate the laser to form a large beam laser beam, and then generates interference fringes through the front and rear mirror reflections of a double-sided reflector 3, and projects them onto the surface of the object to be measured 5. The required four-step phase shift is obtained by four laser diode arrays 1 arranged side by side.

[0036] The device consists of a laser diode array 1, a collimating lens 2 and a double-sided reflector 3, wherein: the laser diode array 1 has the characteristic of a large divergence angle, the front end face 3-1 of the double-sided reflector 3 is partially reflective and the rear end face 3-2 is fully reflective.

[0037] The operating wavelength of the laser diode array 1 is generally visible light, which matches the CCD response of the micro camera 4. Generally, a 520nm green light or 650nm red light single-mode laser diode can be used. The parameters of the four required laser diodes are consistent, the diameter of the laser head is 6mm, and they are closely arranged side by side to form a column. Through the control of the driving circuit, only one laser diode is lit at the same time. In the four-step fringe phase shift measurement process, the laser diodes are lit in turn in cooperation with the camera to capture laser stripes under different phase shift amounts.

[0038] The focal length of the collimating lens 2 is 7.5 cm. The function of the collimating lens 2 is to collimate the laser diode with a large angle diffusion.

[0039] The double-sided reflector 3 has the following characteristics: the front face 3-1 of the double-sided reflector 3 is partially reflective (reflectivity is about 38%), and the rear face 3-2 is fully reflective (reflectivity is about 100%). The collimated laser beam is reflected by the front and rear faces respectively, overlapping in space to produce interference fringes.

[0040] The micro camera 4 shoots the patterns of laser interference fringe projections under different phase shifts, and the computer uses spatial calibration and algorithms to invert the depth information of the three-dimensional surface contour of the object.

[0041] When people use the device, first, the divergent laser emitted by the laser diode 1 (taking 1-2 as an example) is collimated by the collimating lens 2. The relative positions of the laser diode array 1 and the collimating lens 2 are fixed to ensure that the projected laser spot remains unchanged. After passing through the collimating lens, the laser beam basically maintains parallel output. The collimated laser beam is reflected once by the front end face 3-1 of the double-sided reflector 3, partially reflected, partially transmitted and reflected again by its rear end face 3-2. The part transmitted through the front end face 3-1 overlaps with the laser of the first partial reflection part in space, thereby generating spatial interference fringes. The interference fringes here are full-space, so at different distances, the image of the fringes is also clear and stable, and is not limited by the depth of field. The period of the interference fringes (affecting the spatial resolution of three-dimensional measurement) can be adjusted by fine-tuning the spacing between the laser diode array 1 and the collimating lens 2.

[0042] The interference fringes are directly projected onto the surface of the object to be measured 5, forming a deformed fringe pattern, which is photographed by the micro camera 4. The hardware is synchronized by clocks so that when a laser diode is turned on, the micro camera 4 is just in the exposure response. The circuit controls the four diodes in the laser array 1 to turn on in turn, and takes four fringe projection pictures. The three-dimensional morphology of the object can be obtained by inversion of the computer algorithm, which is the principle of the four-step phase shift method.

[0043] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A laser stripe projection device, comprising a plurality of laser diode arrays (1), a collimating lens (2), a reflector (3), a micro camera (4) and an object to be measured (5), characterized in that: The collimating lens (2) is fixedly mounted on one side of the laser diode array (1); the reflecting mirror (3) is arranged on a side of the collimating lens (2) away from the laser diode array (1); the laser diode array (1), the collimating lens (2) and the reflecting mirror (3) are all located at the same horizontal position; the micro camera (4) is arranged between the collimating lens (2) and the reflecting mirror (3) and at a position above the collimating lens (2) and the reflecting mirror (3); and the object to be measured (5) is arranged between the collimating lens (2) and the reflecting mirror (3) and on a side opposite to the micro camera (4); The laser diode array (1) comprises a laser diode 1 (1-1), a laser diode 2 (1-2), a laser diode 3 (1-3) and a laser diode 4 (1-4), and the laser diode 1 (1-1), the laser diode 2 (1-2), the laser diode 3 (1-3) and the laser diode 4 (1-4) are linearly arranged in sequence from top to bottom; The laser heads of the laser diode 1 (1-1), the laser diode 2 (1-2), the laser diode 3 (1-3) and the laser diode 4 (1-4) all have a diameter of 6 mm; The divergence angle of the laser diode array (1) is greater than 60 degrees, and its laser wavelength is 650nm.

2. A laser stripe projection device according to claim 1, characterized in that: The focal length of the collimating lens (2) is 7.5 cm.

3. A laser stripe projection device according to claim 1, characterized in that: The reflector (3) comprises a front end face (3-1) and a rear end face (3-2), wherein the front end face (3-1) and the rear end face (3-2) are integrally formed.

4. A laser stripe projection device according to claim 3, characterized in that: The reflectivity of the front end face (3-1) of the reflector (3) is 38%, and the reflectivity of the rear end face (3-2) of the reflector (3) is 100%.

5. The laser stripe projection device according to claim 1, characterized in that: The response band of the micro camera (4) is consistent with the band of the laser diode array (1).

6. The laser stripe projection device according to claim 1, characterized in that: The laser diode array (1) and the micro camera (4) are both electrically connected to a clock controller via wires, and the laser diode array (1), the micro camera (4) and the clock controller are both electrically connected to an external or internal power supply via wires.

7. A laser stripe projection device according to claim 6, characterized in that: The laser diode one (1-1), laser diode two (1-2), laser diode three (1-3) and laser diode four (1-4) are electrically connected to the clock controller and the internal or external power supply through wires.

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