Bar code optical imaging system based on rolling shutter technology

Abstract

The invention discloses a bar code optical imaging system based on a rolling shutter technology, and belongs to the field of optical communication. The system can generate a light source control signal according to any bar code pattern, a light source driving circuit is utilized to control a light source to perform high-speed switching invisible to human eyes, so that light spots with controlled and changed brightness are formed on a wall surface, a ground or other monochromatic surfaces, and the camera with a roller shutter is utilized to photograph the light spots to obtain alternately dark and bright stripes. And finally, the information contained in the bar code can be read through a ready-made bar code identification program. According to the invention, the bar code information can be embedded into the illumination light on the premise that a user does not perceive the bar code information, and the bar code information can be conveniently obtained by using mature sensors such as a mobile phone camera and a widely popularized bar code reading program.

Description

Technical Field

[0001] The invention relates to the field of optical communication technology, and in particular to a bar code optical imaging system based on rolling shutter technology. Background Art

[0002] A barcode consists of a series of parallel lines and spaces of varying widths, arranged according to specific encoding rules to represent numbers, letters, and symbols. Each barcode has specific start and end marks, as well as a data encoding area in the middle. Different barcode standards (such as UPC, EAN, Code 128, etc.) define different encoding rules that specify how to encode characters into patterns of bars and spaces. The reading of a barcode depends on the width ratio and relative position of the bars and spaces. A barcode scanner identifies a barcode by detecting the difference in reflectivity of these bars and spaces, and the decoder software converts the received signal back into raw data, decoding it into a human-readable or machine-processable data format.

[0003] Rolling shutter is a shutter mechanism widely used in modern digital cameras and mobile phone cameras. Mechanical shutter achieves the effect of rolling shutter through physical structure, while electronic shutter achieves progressive exposure through electronic control. In rolling shutter, the pixels on the photosensitive element are not exposed at the same time, but are exposed row by row. After the exposure is completed, the charge is read from the photosensitive element row by row. Since the exposure and reading are performed row by row, the exposure and reading time of pixels in different rows are different during the entire operation of rolling shutter. This time difference may cause the "jelly effect" when shooting fast-moving objects, or the "stroboscopic" phenomenon when shooting high-frequency lights.

[0004] The persistence of vision effect refers to the fact that when the human eye observes a rapidly changing image, the image impression on the retina does not disappear immediately, but is retained for a short time due to the limited reaction speed of the visual system. When the flickering frequency of an LED light with AC power is higher than the critical frequency at which the human eye can perceive flickering, the human eye sees the high-frequency flickering LED light as a constant on state, and cannot directly observe its flickering. Summary of the invention

[0005] The present invention provides a barcode optical imaging system based on rolling shutter technology, which can embed barcode information into illumination light without user perception, and use a camera to realize convenient acquisition of the barcode information.

[0006] The embodiment of the present invention provides a barcode optical imaging system based on rolling shutter technology, comprising:

[0007] light source;

[0008] A barcode information encoding module, used to generate a light source control signal according to the barcode features;

[0009] A light source driving circuit, used for controlling the flashing mode of the light source according to the light source control signal;

[0010] A camera with a rolling shutter is used to capture the light spot of a light source and obtain barcode feature information corresponding to the light spot.

[0011] Optionally, in one embodiment of the present invention, the barcode information encoding module is further used to generate a light source control signal consisting of high and low pulse signals with different durations according to the order and thickness of the white and black stripes in the barcode.

[0012] Optionally, in one embodiment of the present invention, the flashing mode of the light source includes when to turn on / off the light source, and how long the lighting / off duration lasts, the lighting / off time of the light source depends on the position of the switching of the white / black stripes in the barcode, and the lighting / off duration of the light source is proportional to the width of the white / black stripes in the barcode.

[0013] Optionally, in one embodiment of the present invention, the flicker frequency of the light source is higher than a critical frequency at which the human eye can perceive flicker, and is lower than an upper limit of shutter perception of a camera with a rolling shutter.

[0014] Optionally, in an embodiment of the present invention, the light source is a plurality of light source units, and each light source unit flashes according to the same flashing pattern.

[0015] Optionally, in one embodiment of the present invention, the light source includes an LED or a fluorescent lamp.

[0016] Optionally, in one embodiment of the present invention, the light source is an infrared light source or an ultraviolet light source.

[0017] Optionally, in one embodiment of the present invention, the light source includes light sources of multiple wavelengths, which are respectively controlled by different barcodes, and the camera uses different channels to independently obtain barcodes corresponding to different wavelengths during acquisition.

[0018] Optionally, in one embodiment of the present invention, a period for sending a complete barcode is shorter than an imaging period of a camera.

[0019] Optionally, in one embodiment of the present invention, a plurality of barcodes are included in one imaging cycle of the camera, and a non-changing protection interval is added between different barcode signals.

[0020] In the barcode optical imaging system based on rolling shutter technology of the embodiment of the present invention, the barcode information encoding module generates a corresponding light source control signal according to any barcode pattern, and the light source driving circuit controls the light source to perform high-speed switching that is invisible to the human eye, thereby forming a light spot with controlled brightness change on the wall, the ground or other monochrome surfaces, and the camera with rolling shutter uses the rolling shutter effect of the camera to take a picture of the modulated light spot to obtain light and dark stripes, which are consistent with the barcode, and finally the information contained in the barcode can be read through the ready-made barcode recognition program. The present invention can embed the barcode information into the illumination light without the user's perception, and use mature sensors such as mobile phone cameras and widely popular barcode reading programs to realize the convenient acquisition of barcode information. Compared with the traditional visible light communication method, this invention not only avoids the use of additional high-speed photoelectric conversion hardware modules, but also does not require users to aim the camera at the light source, and also saves the tedious steps of users installing special codec programs, and the threshold for popularization is low; compared with the traditional barcode, this invention does not require the camera to be aimed at the barcode during sampling, does not require printing consumables, the barcode content can be dynamically changed, does not affect the landscape, and has a strong sense of technology. This invention can be applied in the fields of product introduction, indoor positioning, sightseeing guides, etc., to achieve efficient, imperceptible, and convenient information interaction.

[0021] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0023] Figure 1 A schematic diagram of a barcode optical imaging system based on rolling shutter technology provided according to an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of an application scenario of an embodiment of the present invention;

[0025] Figure 3 Schematic diagram of the correspondence between the original barcode and the LED modulation waveform and the camera sampling effect according to an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of a barcode photographed by a typical camera with a rolling shutter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0028] Figure 1 The figure is a schematic diagram of a barcode optical imaging system based on rolling shutter technology according to an embodiment of the present invention.

[0029] like Figure 1 As shown, the barcode optical imaging system based on rolling shutter technology includes:

[0030] light source;

[0031] A barcode information encoding module, used to generate a light source control signal according to the barcode features;

[0032] A light source driving circuit, used for controlling the flashing mode of the light source according to the light source control signal;

[0033] A camera with a rolling shutter is used to capture the light spot of a light source and obtain barcode feature information corresponding to the light spot.

[0034] In one embodiment of the present invention, the barcode information encoding module is further used to generate a light source control signal consisting of high and low pulse signals with different durations according to the order and thickness of the white and black stripes in the barcode.

[0035] In one embodiment of the present invention, the flashing mode of the light source includes when to turn on / off the light source, and the duration of the lighting / off state. The lighting / off time of the light source depends on the position of the switching of the white / black stripes in the barcode, and the duration of the lighting / off state of the light source is proportional to the width of the white / black stripes in the barcode.

[0036] It is understandable that, taking LED as an example of the light source, the modulation function of the barcode information encoding module is used to control the flashing mode of the LED, that is, when to turn on / off the LED, and how long it lasts. The moment when the LED is turned on / off depends on the position of the white / black stripes switching in the barcode, and the duration of the LED being turned on / off is proportional to the width of the white / black stripes in the barcode. In order to ensure that the flicker is not observed by the human eye but can be captured by the shutter, the LED flickering frequency is higher than the critical frequency at which the human eye can perceive the flicker, but it cannot be higher than the upper limit of the shutter's perception. The camera does not need to capture the LED, but instead captures the wall, ground or other monochrome surfaces illuminated by the LED to form a light spot with controlled brightness changes. The human eye sees that the monochrome surface is illuminated and visually in a constant light state, and the picture captured by the camera with a rolling shutter can record the barcode information emitted in the high-frequency flickering LED light signal. Cameras with rolling shutters can be installed on mobile phones, tablets, computers and other devices. They use their progressive scanning characteristics to record the brightness changes of LEDs at different time points and present barcode light spots in the final image. The photo of the LED light spot will contain alternating light and dark stripes. The position and width of the light and dark stripes are consistent with the position and width of the white and black stripes in the barcode. Therefore, the original barcode information can be obtained by processing the photo of the light spot through a barcode reading program.

[0037] In one embodiment of the present invention, the light source is a plurality of light source units, and each light source unit flashes according to the same flashing pattern.

[0038] Specifically, when the LED light area is large enough, the camera can also be aimed directly at the LED to obtain a clearer barcode image. When the light intensity of one LED is insufficient, multiple LEDs can also be flashed in the same pattern, so that the camera can capture a clear barcode image.

[0039] In a specific embodiment of the present invention, low contrast or blurred edges of the barcode may cause the scanner to misinterpret the barcode, thereby causing data errors. Therefore, if the brightness of the lighting LED is insufficient or the waveform in the LED driving circuit has a slow rise and fall phenomenon, it may cause difficulty in barcode recognition. In view of the differences in performance and sensitivity of different scanning devices, improving the contrast between the bars and spaces in the barcode and the clarity of the edges between the bars and spaces can improve its compatibility with a variety of scanning devices, enhance long-distance recognizability and operational flexibility. In order to solve the problem of insufficient lighting brightness of a single LED, the overall light intensity can be enhanced by flashing multiple LEDs in the same pattern. At the same time, the choice of monochrome surface color may further affect the bar-space contrast of the barcode. In addition, to ensure the clarity of the bar-space edges of the barcode, high and low pulse signals of different heights should be used to drive the LED to emit light. These measures work together to optimize the recognition effect of the barcode, reduce the error rate, and ensure the efficiency and accuracy of data reading.

[0040] In one embodiment of the present invention, in addition to the high-speed switching LED, the light source may also be other low-speed light sources that are blocked quickly and continuously, such as fluorescent lamps.

[0041] In one embodiment of the present invention, the light source may use an infrared or ultraviolet light source without providing an illumination function.

[0042] In one embodiment of the present invention, the number of light sources may be greater than 1 and the light source may use a narrow beam, thereby presenting multiple barcodes on one photo sample.

[0043] In one embodiment of the present invention, the choice of light source is not limited to LEDs with lighting functions. Instead, infrared or ultraviolet light sources can be used, which, although not providing visible lighting, can also emit modulated bar code signals. For this purpose, a camera with corresponding special photosensitivity characteristics is required to capture the modulated light signals emitted by these specific wavelengths of light sources. This approach expands the application range of light sources and allows effective bar code encoding and decoding under non-lighting conditions.

[0044] In one embodiment of the present invention, the light source may use a time division multiplexing method to continuously output multiple barcode information within a period of time to improve the encoding capacity.

[0045] Optionally, in one embodiment of the present invention, the light source includes light sources of multiple wavelengths, which are respectively controlled by different barcodes. When the camera collects data, different channels are used to independently obtain barcodes corresponding to different wavelengths, thereby realizing the simultaneous transmission of multiple barcode information.

[0046] Optionally, in one embodiment of the present invention, a period for sending a complete barcode is shorter than an imaging period of a camera.

[0047] Optionally, in one embodiment of the present invention, a plurality of barcodes are included in one imaging cycle of the camera, and a non-changing protection interval is added between different barcode signals.

[0048] In a specific embodiment, Figure 2As shown in FIG. 1 , a typical application scenario of the technology is shown. First, the light source control signal generated by the barcode encoding module is used to drive the LED to emit light. The barcode information encoding module in the figure mainly has modulation function and encoding function. The LED modulation frequency must be higher than the critical frequency at which the human eye can perceive flickering, ensuring that the human eye can transmit barcode information without perception, and at the same time cannot be higher than the upper limit of the shutter perception, ensuring that the stripes can be recorded by the camera with a rolling shutter, and at least one barcode cycle can be completely recorded. The encoding module in the figure needs to control the LED flashing mode so that the duration of the LED on / off is proportional to the width of the white / black stripes in the barcode. This process completes the embedding of barcode information in the illumination light. Since the rapid flashing of the LED exceeds the range that can be perceived by the visual persistence effect of the human eye, that is, it is higher than the sensitive threshold of the human eye to light flickering, the LED light source presents a continuous and soft lighting effect to the observer, thus achieving an effect that is invisible to the human eye but can be captured by a camera with a rolling shutter.

[0049] like Figure 2 As shown in the figure, the ground is a monochrome surface, and a camera with a rolling shutter is installed on the mobile phone. The camera takes a photo of the ground with LED light shining on it, and the photo shows light and dark stripes. The relative position and width of these stripes are consistent with the layout of the black and white stripes in the barcode to be displayed. Finally, this information can be recognized and decoded by the barcode reading program.

[0050] In one embodiment of the present invention, when the LED lamp has a sufficient size, the LED lamp itself can directly act as a monochrome surface. In this case, a clearer barcode image can be captured by directly aiming the camera at the LED lamp. This configuration simplifies system settings while improving the efficiency and quality of image acquisition.

[0051] In a specific embodiment of the present invention, multiple light sources can be used and the light sources can use narrow beams. By loading the same or different barcode information onto each light source, multiple light spots can be formed on the same monochromatic surface. Such a configuration enables multiple barcodes to be presented simultaneously in the same photo sample, effectively increasing the amount of information that can be obtained in a photo and improving the efficiency of information transmission.

[0052] Figure 3 The corresponding relationship between the original barcode and LED modulation waveform and the camera sampling effect.

[0053] like Figure 3As shown, there is a direct correspondence between the original barcode and the LED modulation waveform. In order for the LED to transmit the barcode information, the LED must flash alternately in light and dark over time according to the sequence of black and white stripes in the barcode and their width information. In this process, the black stripes in the barcode correspond to the "off" state of the LED, while the white stripes correspond to the "on" state of the LED. In addition, the width of the black and white stripes should maintain a certain proportional relationship with the duration of the LED in the "on" and "off" states. Therefore, Figure 3 The LED signal waveform shown in the figure is consistent with the original barcode pattern. This precise timing control ensures the accurate transmission of barcode information and subsequent effective reading.

[0054] In a specific embodiment of the present invention, the LED uses a fast flashing light signal to transmit barcode information in a continuous periodic manner. The continuous barcode information transmission mechanism allows repeated transmission of the same barcode, or cyclic transmission of different barcodes. That is, the light source can output multiple barcode information within a certain time interval through time division multiplexing technology, thereby enhancing the encoding capacity. This method not only improves the efficiency of information transmission, but also optimizes the encoding capacity.

[0055] In order to enhance the readability of the barcode and prevent the connection between barcodes from causing confusion in identification, a guard interval can be set between every two barcode signals. Figure 3 As shown in the figure, the camera sampling effect photo contains three complete barcode cycles and two protection intervals. These protection intervals are reflected in that after each complete barcode information is sent, the LED remains "on" during the protection interval time, thus ensuring clear separation between adjacent barcodes.

[0056] In a specific embodiment of the present invention, during an imaging cycle of the camera, the protection interval may also be set to other optical signals with non-jumping waveforms.

[0057] Figure 4 The figure shows a typical barcode image taken by a camera with a rolling shutter, showing a complete barcode cycle and a clear guard interval. The rolling shutter technology is used in smartphone cameras. When the phone is aimed at a modulated LED light source to take a photo, the photo can clearly record the time-varying light signal emitted by the LED. The information contained in the barcode can be read using an existing barcode recognition program. This phenomenon confirms the effectiveness of the rolling shutter mechanism in recording high-frequency flickering LED light sources, and can accurately capture and present the stripe information in the light signal.

[0058] In the traditional barcode recognition process, occlusion will affect normal recognition. Occlusion will block the scanner from reading part or all of the barcode information, resulting in failure to correctly decode or recognize the barcode content. Figure 4 The barcode is displayed in the photo with interference from objects, and the barcode content can still be recognized normally. This proves that this method has a certain degree of anti-interference. Since the spot area is large enough, as long as the main part of the barcode (including the start / end symbol and data area) is not blocked and the contrast is sufficient, small-area blocking will basically not affect recognition.

[0059] In a specific embodiment of the present invention, the rolling curtain progressive scanning takes the long side of the image as a line, and the CMOS reads the long side of the image line by line, and displays the image in a vertical screen device such as a mobile phone. Figure 4 Middle vertical stripes.

[0060] In a specific embodiment of the present invention, when performing experimental settings for LED light source illumination and camera shooting, the recommended best practice is to project the LED light source vertically onto a monochromatic surface, while ensuring that the camera is parallel to the surface for shooting. This experimental setting can minimize the deformation of the barcode information and maintain its geometric integrity in the image, thereby ensuring that the barcode is captured by the camera in a clear and uniform manner.

[0061] In a specific embodiment of the present invention, the light source may be composed of LEDs of multiple wavelengths, and each wavelength of LED corresponds to the transmission of different barcode content. When the camera collects images, by installing a specific filter in front of the camera, light signals of different wavelengths can be screened and allowed to enter the camera separately. This method uses independent channels to capture barcodes corresponding to different wavelengths, respectively, and realizes the simultaneous transmission of multiple barcode information. In this way, the system can effectively separate and identify multiple barcodes, thereby improving the efficiency and capacity of information transmission.

[0062] In a specific embodiment of the present invention, attention should be paid to the relationship between the camera exposure time and the LED flashing frequency, and coordination between the two must be ensured to achieve effective image acquisition, otherwise the camera may not be able to accurately capture the barcode information in the LED flashing. Specifically, a relatively long exposure time or a too fast LED flashing may cause the shutter to be unable to capture the LED flashing. A relatively short exposure time may cause the camera to complete image acquisition before the transmission of a cycle of barcode information is completed, thereby failing to capture a complete barcode cycle. In addition, a too slow LED flashing frequency will allow the human eye to perceive the flashing of the light. Therefore, the ideal state is that the LED can transmit at least one complete cycle of barcode content within a single shutter exposure time, while ensuring that such flashing is imperceptible to the human eye. This is crucial to achieving efficient and accurate barcode reading.

[0063] According to the barcode optical imaging system based on rolling shutter technology proposed in the embodiment of the present invention, the light source is modulated by the light source driving circuit so that it flashes regularly according to the barcode encoding information, and the characteristics of the camera rolling shutter are used to present the barcode information in the captured picture. The system can realize the presentation of barcode information without printing the barcode object. The present invention can embed the barcode information into the illumination light without the user's perception, and use mature sensors such as mobile phone cameras and widely popular barcode reading programs to realize the convenient acquisition of barcode information. Compared with the traditional visible light communication method, the present invention not only avoids the use of additional high-speed photoelectric conversion hardware modules, but also does not require the user to aim the camera at the light source, and also saves the cumbersome steps of the user installing a special encoding and decoding program, and the threshold for popularization is low; compared with the traditional barcode, the present invention does not require the camera to aim at the barcode during sampling, does not require printing consumables, the barcode content can change dynamically, does not affect the landscape, and has a strong sense of technology. The present invention can be applied in the fields of product introduction, indoor positioning, sightseeing guide, etc., to achieve efficient, imperceptible and convenient information interaction.

[0064] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0065] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "N" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

Claims

1. A barcode optical imaging system based on rolling shutter technology, characterized in that: include: light source; A barcode information encoding module, used to generate a light source control signal according to the barcode features; A light source driving circuit, used for controlling the flashing mode of the light source according to the light source control signal; A camera with a rolling shutter is used to capture the light spot of a light source and obtain barcode feature information corresponding to the light spot.

2. The system according to claim 1, characterized in that The barcode information encoding module is further used to generate a light source control signal composed of high and low pulse signals with different durations according to the order and thickness of the white and black stripes in the barcode.

3. The system according to claim 1, characterized in that The flashing mode of the light source includes when to turn on / off the light source and how long it lasts. The time when the light source is turned on / off depends on the position of the switching of the white / black stripes in the barcode, and the duration of the light source being turned on / off is proportional to the width of the white / black stripes in the barcode.

4. The system according to claim 1, characterized in that The flicker frequency of the light source is higher than the critical frequency at which the human eye can perceive flicker, and is lower than the shutter perception upper limit of a camera with a rolling shutter.

5. The system according to claim 1, characterized in that The light source is a plurality of light source units, and each light source unit flashes according to the same flashing mode.

6. The system according to claim 1, characterized in that The light source includes an LED or a fluorescent lamp.

7. The system according to claim 1, characterized in that The light source is an infrared light source or an ultraviolet light source.

8. The system according to claim 1, characterized in that The light source includes light sources of multiple wavelengths, which are respectively controlled by different barcodes. When the camera collects data, different channels are used to independently obtain barcodes corresponding to different wavelengths.

9. The system according to claim 1, characterized in that The cycle of sending a complete barcode is shorter than the imaging cycle of the camera.

10. The system according to claim 9, characterized in that In one imaging cycle of the camera, multiple barcodes are included, and a non-changing protection interval is added between different barcode signals.

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