Device and method for shooting clear image in close range through machine vision

Abstract

The invention provides a device and a method for shooting clear images in a close range through machine vision. The device comprises an imaging module, a structured light source for image definition evaluation, a lighting source, a clear image judging and shooting method and a processing circuit, and the imaging module is composed of a plurality of (N, Ngt; 1) the imaging unit is provided with a lens and an image sensor which are fixed at different focusing positions and have the same focal length; the processing circuit controls the structured light source to emit light with a specific structure shape to irradiate the surface of an object, N imaging units with different focusing positions are used for shooting to obtain N frames of image data, the definition of the light structure shape of the structured light source in the N frames of image data is judged, and the number M of the imaging unit with the clearest definition is obtained; then, the structured light source is turned off, the illumination light source is turned on, and the M imaging unit is used for shooting and outputting image data. The method solves the problem that the machine vision has an ultra-large depth-of-field requirement on the camera, and is wide in application prospect.

Description

Technical Field

[0001] The present invention relates to the fields of artificial intelligence, machine vision, and intelligent image detection technology, and in particular to a device and method for capturing clear images at close range using machine vision, which is particularly beneficial for machine vision applications on motion platforms with large position control errors, such as drones and unmanned vehicles. Background Art

[0002] In some dangerous working environments that are not suitable for manual work or where artificial vision cannot meet the requirements, machine vision is often used to replace artificial vision. However, in many practical applications, especially in outdoor visual inspection of non-industrial assembly lines, such as machine vision applications where cameras mounted on drones and unmanned vehicles detect defects in objects, the distance between the camera and the object is difficult to accurately control because the position control of the motion platform itself is difficult to achieve high precision. In this case, how to capture a clear image of the object has become a key factor restricting the accuracy of machine vision inspection.

[0003] For example, when photographing an object surface lacking texture features, the clarity of the image data is difficult to evaluate due to the lack of texture on the object surface, and it is difficult to capture a clear image of the crack. For example, when photographing a crack image on a painted steel plate, the image resolution is often required to be better than 100um or even 10um, but the depth of field of a high-resolution camera is only about 10mm. However, because the surface of the painted steel plate lacks texture information, when the distance control error between the camera and the steel plate is greater than 10mm, even an autofocus camera cannot capture a clear crack image. Summary of the invention

[0004] The purpose of the present invention is to provide a device and method for capturing clear images at close range using machine vision, so as to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides a device and method for shooting clear images at close range by machine vision, comprising an imaging module, a structured light source for image clarity evaluation, an illumination light source, and a method and processing circuit for determining and shooting clear images. The imaging module is composed of a plurality of (N, N>1) imaging units of lenses and image sensors with fixed different focus positions and the same focal length. The processing circuit controls the structured light source to emit light of a specific structural shape to illuminate the surface of an object, and uses N imaging units with fixed different focus positions to shoot and obtain N frames of image data. By determining the clarity of the light structure shape of the structured light source in the N frames of image data, the imaging unit number M of the clearest one is obtained; then, the structured light source is turned off, the illumination light source is turned on, and the M imaging unit is used to shoot and output its image data.

[0007] Preferably, the imaging module is composed of a plurality of (N, N>1) imaging units having lenses and image sensors with fixed different focus positions and the same focal length.

[0008] Preferably, a structured light source is used to illuminate the surface of the object for evaluating the clarity of the image.

[0009] The present invention also provides a method for determining and photographing a clear image, comprising the following steps:

[0010] S1. The processing circuit controls the structured light source to emit light of a specific structure shape onto the surface of the object;

[0011] S2. The processing circuit uses N imaging units with fixed different focus positions and the same focal length to obtain N frames of image data;

[0012] S3. The processing circuit calculates the clarity of the light structure shape of the structured light source irradiating the surface of the object, determines the clarity of the images captured by the N imaging units, and obtains the number M of the clearest imaging unit;

[0013] S4. The processing circuit turns off the structured light source, turns on the illumination light source, uses the M imaging unit to take pictures and outputs its image data.

[0014] Compared with the prior art, the present invention has achieved the following beneficial technical effects: the present invention solves the problem of large depth of field requirement for cameras in many application scenarios of machine vision, and can always capture the clearest image within a certain distance between the camera and the object being photographed, avoiding the image blur problem caused by inaccurate focus; in addition, the present invention adopts a fixed-focus lens, which does not require automatic focusing and has a fast shooting speed and a long service life. It is outstanding in:

[0015] (1) An image acquisition module with N fixed focus positions and fixed focal length lenses is used to shoot objects within a certain distance range. Although the clarity is different due to different focus positions, the resolution of the images shot is equal and the clearest image can always be output, which is convenient for application. The equivalent depth of field range is very large, which is especially beneficial for machine vision applications on motion platforms with large position control errors such as drones and unmanned vehicles.

[0016] (2) A structured light source is used for pre-shooting, and the clarity of the image captured by N imaging units is evaluated by the clarity of the light structure shape irradiated on the surface of the object, which solves the problem of difficulty in evaluating image clarity when shooting objects that lack texture features.

[0017] (3) It has no moving mechanism, works reliably, has good performance consistency, and has a long service life. At the same time, it is small in size and light in weight, making it easy to mount on drones.

[0018] (4) Using N conventional fixed-focus lenses has low cost, simple process, and is easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0020] Figure 1 A schematic diagram of a device and method for capturing clear images at close range using machine vision provided by the present invention.

[0021] Description of Figure Numbers:

[0022] 1- Lenses with different focus positions and the same focal length; 2- Image sensor; 3- Structured light source; 4- Illumination light source; 5- Processing circuit. 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] The purpose of the present invention is to provide a device and method for capturing clear images at close range using machine vision, so as to solve the problems existing in the prior art.

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Embodiment 1:

[0027] This embodiment provides a device and method for capturing clear images at close range using machine vision. Figure 1 As shown, it includes an imaging module, a structured light source 3 for image clarity evaluation, an illumination light source 4, and a method and processing circuit 5 for clear image determination and shooting. The imaging module is composed of an imaging unit having a lens 1 and an image sensor 2 with fixed different focus positions and the same focal length.

[0028] As an implementation mode, the lens 1 of the imaging unit adopts 4 high-definition and ultra-high-definition lenses with a resolution of 4K or above with M12 interfaces, 1 / 1.8 inches, and a focal length of 12 mm. Their focusing positions are respectively set to objects at a distance of 18 cm to 22 cm, 21 cm to 25 cm, 24 cm to 28 cm, and 27 cm to 31 cm from the lens. This ensures that the clearest image can be output when the object changes within the range of 18 cm to 31 cm from the lens.

[0029] As an implementation manner, the image sensor 2 of the imaging unit uses four AR2020 image sensors, 1 / 1.8 inches, an image resolution of 5120 (H) * 3840 (V), 20 million pixels, and the image data is output through the MIPI interface.

[0030] As an implementation manner, the structured light source 3 uses a grid grating light source of a green laser with a grid number of 10*10, and outputs a high-brightness grid structure shape to illuminate the surface of the object.

[0031] As an implementation manner, the lighting source 4 uses 4 LED lighting lamp beads, warm white, and each has a power of 1W.

[0032] As an implementation mode, the processing circuit 5 is implemented by FPGA, accesses the image data of the four imaging units through the MIPI interface, and controls the opening and closing of the structured light source 3 and the illumination light source 4. When the structured light source 3 is controlled to be turned on, an image is captured and the image data of the four imaging units are evaluated for clarity, and the imaging unit number M of the clearest one is obtained. When the illumination light source is turned on, the M-number imaging unit is used to capture, and its image data is output through the HDMI interface.

[0033] The method for determining and photographing a clear image in this embodiment includes the following steps:

[0034] S1. The processing circuit 5 controls the structured light source 3 to emit a high-brightness grid structure shape of light with a grid number of 10*10 to illuminate the surface of the object;

[0035] S2. The processing circuit 5 uses four imaging units with fixed different focus positions and the same focal length to obtain four frames of image data;

[0036] S3. The processing circuit 5 calculates the clarity of the grid structure shape of the structured light source 3 irradiating the surface of the object, determines the clarity of the images captured by the four imaging units, and obtains the number M of the clearest imaging unit;

[0037] S4. The processing circuit 5 turns off the structured light source 3, turns on the illumination light source 4, uses the M-number imaging unit to take pictures and outputs its image data.

[0038] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A device and method for capturing clear images at close range using machine vision, characterized in that: The invention comprises an imaging module, a structured light source for image clarity evaluation, an illumination light source, and a method and processing circuit for determining and shooting a clear image. The imaging module is composed of a plurality of (N, N>1) imaging units of lenses and image sensors with fixed different focus positions and the same focal length. The processing circuit controls the structured light source to emit light of a specific structural shape onto the surface of an object, and uses N imaging units with fixed different focus positions to obtain N frames of image data, and determines the clarity of the light structure shape of the structured light source in the N frames of image data, and obtains the imaging unit number M of the clearest one; Then, the structured light source is turned off, the illumination light source is turned on, and the M imaging unit is used to shoot and output its image data.

2. The device and method for capturing clear images at close range using machine vision according to claim 1, characterized in that: The imaging module is composed of a plurality of (N, N>1) imaging units having lenses and image sensors with fixed different focus positions and the same focal length.

3. The device and method for capturing clear images at close range using machine vision according to claim 1, characterized in that: A structured light source is used to illuminate the surface of the object for image clarity evaluation.

4. A method for determining and photographing a clear image, characterized in that: The following steps are involved: S1. The processing circuit controls the structured light source to emit light of a specific structure shape onto the surface of the object; S2. The processing circuit uses N imaging units with fixed different focus positions and the same focal length to obtain N frames of image data; S3. The processing circuit calculates the clarity of the light structure shape of the structured light source irradiating the surface of the object, determines the clarity of the images captured by the N imaging units, and obtains the number M of the clearest imaging unit; S4. The processing circuit turns off the structured light source, turns on the illumination light source, uses the M imaging unit to take pictures and outputs its image data.

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