The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2015-090584 filed in Japan on Apr. 27, 2015 and Japanese Patent Application No. 2016-044855 filed in Japan on Mar. 8, 2016.
1. Field of the Invention
The present invention relates to methods for manufacturing laminated glass, and methods for calibrating a stereo camera.
2. Description of the Related Art
Recent vehicles are internally equipped with various optical devices such as a headup display and an on-vehicle camera. These optical devices are often used through a windshield. Such a windshield has therefore been needed to have the performance of an optical component. It has been known that, in a manufacturing process of a windshield, temperature and take time, for example, are managed to approximate the shape of a windshield to design data and eliminate optical distortion.
For example, Japanese Patent Application Laid-open No. 2004-132870 discloses a regulator for a stereo camera for the purpose of regulation regarding optical distortion and a positional shift of a stereo camera by image processing. Japanese Patent Application Laid-open No. H7-010569 discloses detailed conditions for a manufacturing process of sheet glass by the float process for the purpose of reducing a fine corrugation profile formed in the manufacturing process. Japanese Patent Application Laid-open No. 2007-290549 discloses a windshield in which distortions generated in the windshield is made different in direction to reduce distortion when seeing through the windshield, and a manufacturing method of the windshield.
Typical manufacturing techniques known to the inventor, however, have a problem in that under the influence of formation of small waviness profiles formed randomly on the front and the back surfaces of a windshield in a manufacturing process of sheet glass used for the windshield, optical distortion occurs, resulting in small distortion in an image captured by, for example, a camera through the windshield.
Japanese Patent Application Laid-open No. 2004-132870 is similar in that optical distortion and a positional shift of a stereo camera mounted in a vehicle are measured to perform correction so as to mitigate the effect of distortion generated by a windshield. However, because correction regarding the distortion generated by the windshield depending on the positional relation between the camera and the windshield at the time of measurement is performed by image processing, change in the positional relation due to an impact or vibration causes the effect of the distortion generated by the windshield to recur.
Japanese Patent Application Laid-open No. H7-010569 decreases the size of a fine corrugation profile formed on sheet glass to reduce the effect of optical distortion. However, corrugations formed on a surface of sheet glass cannot be completely eliminated, and therefore a windshield manufactured using such sheet glass has small corrugations formed randomly on the front and back surfaces, resulting in optical distortion.
With the disclosure of Japanese Patent Application Laid-open No. 2007-290549, the effect of corrugations formed on sheet glass cannot be sufficiently reduced, and therefore a windshield manufactured using such sheet glass has small corrugations formed randomly on the front and back surfaces. These corrugations result in optical distortion.
It is an object of the present invention to at least partially solve the problems in the conventional technology.
According to one aspect of the present invention, a method is for manufacturing laminated glass. The method includes cutting a first glass and a second glass, and bonding the first glass and the second glass. At the cutting, the first glass and the second glass are cut out of one sheet of glass having a corrugation formed in a predetermined direction, in such a manner that corresponding sides of the first glass and the second glass are cut in a same cutting direction. At the bonding, the first glass and the second glass are bonded together in such a manner that the corrugation of the first glass and the corrugation of the second glass are aligned with each other.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.
The accompanying drawings are intended to depict exemplary embodiments of the present invention and should not be interpreted to limit the scope thereof. Identical or similar reference numerals designate identical or similar components throughout the various drawings.
The following describes in detail an embodiment of a method for manufacturing laminated glass and a method for calibrating a stereo camera according to the present invention. An object of the embodiment is to reduce an effect of optical distortion resulting from a small waviness profile formed in a manufacturing process of sheet glass.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention.
As used herein, the singular forms “a”, an and the are intended to include the plural forms as well, unless the context clearly indicates otherwise.
In describing preferred embodiments illustrated in the drawings, specific terminology may be employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that have the same function, operate in a similar manner, and achieve a similar result.
Overview of Windshield
The following describes an overview of a windshield and processing before and after alignment (bonding adjustment) to be described later.
A windshield 10 has a three-layer structure including two sheets of glass and an anti-shattering film sandwiched between the sheets of glass. The two sheets of glass are manufactured by a method called the float process, during which a profile that look like waves rolling in one direction at a small pitch is formed in the sheets of glass.
The float process mentioned above is a process of floating thin molten glass on molten metal to manufacture sheet-shaped glass. Due to this process, a fine corrugation (wave form) tends to be formed on a surface of the sheet-shaped glass in the flow direction of the glass material.
The manufactured sheets of glass are subjected to heat and formed into a desired shape, and then bonded together with the film sandwiched between the sheets. On the front and back surfaces of a windshield produced through such a manufacturing process of sheet glass, small corrugations due to the float process are scattered randomly.
Sections of the windshield 10 manufactured as described above are illustrated as follows: an area A section in
However, as illustrated in
The two sheets of glass for the front surface and the back surface of the windshield 10 are aligned and bonded in such a manner that the fine corrugation profiles formed on the sheets of glass are aligned (refer to
In view of the above, in the embodiment, a manufacturing method of a windshield includes aligning and bonding two sheets of glass for the front surface and the back surface of the windshield in such a manner that the fine corrugation profiles formed on the sheets of glass are aligned. This alignment causes an incident light beam and an exiting light beam of a light beam passing through the windshield to be parallel to each other. Thus, no small distortion is generated in an image acquired by a camera or other devices through the windshield. The following describes specific manufacturing examples and the like in detail with reference to the drawings.
The embodiment describes an example of a windshield 100 that is manufactured as laminated glass with a first glass 100a and a second glass 100b being bonded together.
Next, the sheet glass manufactured as described above is cut into a shape of the windshield 100 (step S12). When the first glass 100a and the second glass 100b to be used as a front surface and a back surface are cut out of the sheet glass, the upper surfaces and the lower surfaces of the first glass 100a and the second glass 100b are made parallel to the direction W in which the fine corrugation is formed. In addition, the first glass 100a and the second glass 100b to be used as the front surface and the back surface are cut on the same line (refer to
The cutting process at step S12 enables bonding at a subsequent bonding process with hardly any misalignment between the corrugations on the first glass 100a and the second glass 100b when subjected to alignment. Specifically, adjusting alignment between the fine corrugation on the first glass 100a and the fine corrugation on the second glass 100b eliminates most of misalignment of the corrugations on the first glass 100a and the second glass 100b.
Subsequently, the first glass 100a and the second glass 100b that have been cut out as described above are subjected to black ceramic screen printing as illustrated in
A pitch p in the alignment mark depends on the pattern of the formed fine corrugation profile. For example, a pitch of approximately 10 mm is sufficient for a corrugation profile formed at a period of 100 mm.
Subsequently, the first glass 100a and the second glass 100b that have been printed with the black ceramic are subjected to a bending process (refer to
When bonding the first glass 100a and the second glass 100b to be used as the font surface and the back surface, the alignment marks of black ceramic described above with reference to
By manufacturing the windshield 100 with the manufacturing processes described above, the fine corrugation profiles formed on the front surface and the back surface are aligned and bonding is performed.
The following describes a windshield manufacturing example 2 that is different from the windshield manufacturing example 1 described above. The windshield manufacturing example 2 uses basically the same processes as illustrated in the drawing, but uses a different cutting process at step S12. Specifically, the sheet glass manufacturing illustrated in
That is, in the cutting process, the upper surfaces and the lower surfaces of the first glass 100a and the second glass 100b are aligned in a direction orthogonal to the direction W in which the fine corrugation is formed, and the first glass 100a and the second glass 100b to be used as the front surface and the back surface are cut on the same line (refer to
In the windshield manufacturing example 2, the fine corrugation profiles formed on the front and the back surfaces are aligned and bonding is performed similarly to the windshield manufacturing example 1.
Calibration System Example
The following describes an exemplary calibration system used when the windshield 100 manufactured by the above-described manufacturing method is installed to a vehicle.
The windshield 100 is installed at the front of the vehicle 150, and the stereo camera 110 is mounted in the vehicle 150. A calibration chart 120 is disposed in front of the vehicle 150. The calibration chart 120 is disposed within the capture range of the stereo camera 110. The stereo camera 110 is coupled to an information processing device (calibration device) 130 to be described later.
The stereo camera 110 includes, as illustrated in
The CPU 140 performs a predetermined control using the RAM 142 as a working memory in accordance with a control program stored in the ROM 141. The storage 143 is a hard disk drive (HDD) or a memory card, for example. The communication device 144 communicates with other devices through the external IF 145 by a wireless method, for example. The external IF 145 is an interface for transmitting and receiving data to and from other devices by a wireless method, for example.
The first image correcting unit 131 acquires an image of the calibration chart 120 captured by the first camera 111, and corrects the image using a correction parameter recorded in the correction parameter recording unit 133. The second image correcting unit 132 acquires an image of the calibration chart 120 captured by the second camera 112, and corrects the image using a correction parameter recorded in the correction parameter recording unit 133. The correction parameter recording unit 133 is a non-volatile memory for recording a correction parameter for image correction processing. For example, the above-described storage 143 is used as the correction parameter recording unit 133.
The parallax calculating unit 134 calculates parallax from respective two images corrected by the first image correcting unit 131 and the second image correcting unit 132, and outputs a parallax image 136. Specifically, the parallax calculating unit 134 calculates position shift regarding the calibration chart 120 from the two captured images of the object. The image processing unit 135 restores a modulation transfer function (MTF) property that has been lowered, and outputs a brightness image 137.
With the configuration above, the images captured by the first camera 111 and the second camera 112 are geometrically corrected by the image correcting units 131 and 132, respectively, in accordance with a parameter recorded in the correction parameter recording unit 133. The first image correcting unit 131 and the second image correcting unit 132 correct the images to obtain pseudo images that would have been captured by the first camera 111 and the second camera 112 that are the same in base line direction and horizontal direction. Then, parallax in the horizontal direction is calculated so that precise parallax image 136 can be output. In addition, the image processing unit 135 restores the lowered MTF property to enable output of the brightness image 137 with improved resolution.
Part or all of the function blocks of the information processing device 130 may be implemented by hardware such as an integrated circuit (IC) instead of software.
A computer program executed by the information processing device 130 is preinstalled in the ROM 141 or other media and provided. The computer program described above may be recorded in a computer-readable recording medium such as a compact disc read only memory (CD-ROM), a flexible disk (FD), a compact disc recordable (CD-R), and a digital versatile disc (DVD), as an installable or executable file, and provided.
The computer program executed in the embodiment may be stored in a computer coupled to a network such as the Internet, and downloaded over the network and provided. Furthermore, the computer program executed in the embodiment may be provided or distributed over a network such as the Internet.
The computer program executed in the embodiment has a modular configuration including the above-described units. In actual hardware, the CPU (processor) 140 reads the computer program from the ROM 141 and executes the computer program, so that the units are loaded into and generated on a main memory.
The computer program of the information processing device 130 may be preinstalled and provided in the ROM 141 or other media.
Calibration (Calibration Example)
The windshield 100 of the embodiment manufactured by the above-described manufacturing method has no local optical distortion with fine corrugations. The windshield 100 is thus particularly effective when used for a module, such as the stereo camera 110, the precision of sensing of which is affected by optical distortion.
However, when mounting the stereo camera 110 relative to the windshield 100, calibration may be disturbed due to an effect of, for example, positional relation between the stereo camera 110 and the windshield 100. Thus, calibration is needed when the stereo camera 110 is mounted in the vehicle 150. The following describes an example in which the position of an object image can be set to an approximately ideal position.
In the system illustrated in
The calibration chart 120 is not limited to the checker pattern illustrated in
The following describes an example operation in the configuration of the calibration system described above and illustrated in
Subsequently, reliability of the captured images is determined (step S23). For example, white brightness of the pattern on the calibration chart 120 is extracted to check for occurrence of significant unevenness in the entire image region. Unevenness of brightness occurring on the calibration chart 120 affects precision of the search for the corresponding points.
If a result such as the one described above is output at step S23 and the data is determined not to be reliable (determination: No), readjustment of an environment regarding calibration with captured images of the calibration chart 120, for example, is performed (step S24). Thereafter, the procedure returns to step S21 and the capture of the calibration chart 120 and the following processes are performed again.
By contrast, if the images captured at step S23 are determined to be reliable (determination: Yes), the parallax calculating unit 134 calculates a correction parameter that corrects the difference dy between corresponding positions to be minimum, and corrects dx to be a parallax value corresponding to a mounting distance (step S25). Subsequently, the correction parameter obtained as described above is written in the correction parameter recording unit 133 (step S26) and the operation ends.
The above-described procedure enables calibration of the stereo camera 110 using the windshield 100 of the embodiment. Specifically, the calibration can correct, with higher precision, distortion that cannot be completely eliminated from the laminated glass 100 manufacture by the above-described manufacturing method. In this manner, according to the embodiment described above, an image (and distance information) with less distortion can be acquired through the windshield 100 in which an effect of distortion due to fine corrugations formed in the manufacturing of sheet glass is reduced.
Effects of the windshield 100 to the precision of the stereo camera 110 can be classified into effects of large distortion due to a glass material and the shape of the whole windshield 100, and effects of small distortion due to a small waviness profile formed on the glass described in the embodiment. Two sheets of glass are aligned and bonded in such a manner that fine corrugation profiles formed on the two sheets of glass for the front surface and the back surface are aligned, which can suppress generation of small distortion.
However, in actual processes, such strict bonding of glass cannot be performed in some cases to reduce take time and cost. In such a case, directions of cutting glass may be changed so that sheets of glass are bonded together with the directions of small waviness profiles being displaced to each other. In other words, the two sheets of glass for the front surface and the back surface are bonded together in such a manner that the directions of waviness on the front and the back surfaces intersect each other. This bonding can distribute effects of distortions of the two surfaces of the front surface and the back surface of the glass.
Specifically, for example, the sheets of glass for the front surface and the back surface are cut in consideration of waviness formed on a surface of a glass material, and are bonded together using an alignment mark (refer to
That is, as illustrated in
The first glass 100a and the second glass 100b that have been cut as described above are subjected to the screen printing (refer to
Specifically, as described above, the sheets of glass that have been cut out are subjected to the black screen printing in the screen printing process. A black ceramic is generally used for improving adhesion and durability of an adhesive used to assembling the glass to a vehicle body, and for improving appearance of the peripheral edge of the glass. At this time, a pattern for alignment as illustrated in
By manufacturing the windshield 100 with the manufacturing processes described above, the fine corrugation profiles formed on the front surface and the back surface are aligned to be orthogonal to each other and the front and the back surfaces are bonded together.
Consequently, the directions of small waviness profiles on the two sheets of glass are displaced to each other, enabling distribution of the effects of distortions of the two surfaces of the front surface and the back surface of the glass.
Subsequently, as described with reference to
As described above, the windshield (laminated glass 100) in which effects of distortion are distributed to reduce the effect of small distortion, and through which images of a chart are captured to calculate a correction parameter from corresponding points of left and right cameras, is used, thus reducing the effect of large distortion. This configuration can provide the stereo camera 110 with high precision as a whole, with the effect of the windshield 100 being considered.
For a calibration method using a chart, a publicly known method such as that described in Japanese Patent No. 4109077 may be used. The method for correcting the effect of large distortion is not limited to a method using a chart. For example, calculation may be performed based on a preliminary measured result as described in Japanese Patent Application Laid-open No. 2015-169583, or may be performed using simulation software as described in Japanese Patent Application Laid-open No. 2015-163866.
The embodiment describes examples of the windshield 100 installed in the vehicle 150. The present invention, however, is not limited to the embodiment. The present invention is applicable to, for example, other devices such as a device that uses the windshield 100 and performs calibration using the stereo camera 110 and the information processing device (calibration device) 130.
An embodiment provides an advantageous effect that an effect of optical distortion resulting from a small waviness profile formed in a manufacturing process of sheet glass is reduced.
The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, at least one element of different illustrative and exemplary embodiments herein may be combined with each other or substituted for each other within the scope of this disclosure and appended claims. Further, features of components of the embodiments, such as the number, the position, and the shape are not limited the embodiments and thus may be preferably set. It is therefore to be understood that within the scope of the appended claims, the disclosure of the present invention may be practiced otherwise than as specifically described herein.
The method steps, processes, or operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance or clearly identified through the context. It is also to be understood that additional or alternative steps may be employed.
Number | Date | Country | Kind |
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2015-090584 | Apr 2015 | JP | national |
2016-044855 | Mar 2016 | JP | national |