Patent Application
20170290170
The subject matter of this disclosure generally relates to cameras. More specifically, and without limitation, the subject matter of this disclosure pertains to making a camera using a method that includes surface mount technology.
Over the last several decades there have been significant changes in camera technology. The proliferation of digital cameras and advances in associated technologies has made it possible to incorporate cameras in a variety of devices. Computers and mobile communication devices, such as smartphones, routinely include cameras. It is also becoming more commonplace to provide one or more cameras on an automotive vehicle to provide enhanced features, such as a parking assist function. It would be useful to be able to provide more advanced driver assist functions that incorporate or use a camera.
One of the challenges associated with developing a camera for use on a vehicle is providing adequate image quality capability while fitting within size and cost constraints. Another challenge is providing a variety of different camera capabilities or features within cost and space constraints.
An illustrative example method of making a camera includes assembling a plurality of lens elements, a sensor, and a housing to establish an assembly with each of the lens elements and the sensor at least partially in the housing. The assembly is then situated adjacent a circuit board substrate. At least the sensor is secured to the circuit board substrate using surface mount technology (SMT) and the assembly is fixed relative to the circuit board substrate.
An illustrative example camera includes a plurality of lens elements, a sensor and a housing. Each of the lens elements is at least partially within the housing. The sensor is at least partially within the housing. The camera also includes a circuit board substrate. A connection between at least the sensor and the circuit board substrate is established using surface mount technology that secures the sensor to the circuit board substrate. The housing, the sensor and the plurality of lens elements are secured in a fixed position relative to the circuit board substrate by the connection between at least the sensor and the circuit board substrate.
Various features and advantages of at least one disclosed example embodiment will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.
In this example, pre-assembling the sensor 34 and the lens elements 28-32 within the housing 30 provides a desired and precise alignment of the sensor 34 with the lens elements 28-32. The entire assembly 22 is then situated on the circuit board substrate 24. In the illustrated example, the sensor 34 includes a plurality of connecting elements 36, which in this example are a ball grid array made of a metal that is suitable for brazing or soldering. Such materials are known. The circuit board substrate 24 includes a soldering paste 38 that may be printed on selected locations where the assembly 22 will be situated.
As schematically shown at 40, a brazing or reflow oven sufficiently heats the connecting elements 36 and the soldering paste 38 where the assembly 22 is soldered and secured in positon on the circuit board substrate 24.
The resulting camera 20 is shown on the right side of
The illustrated camera made using SMT is significantly reduced in size compared to previous automotive vehicle camera arrangements. For example, one embodiment of a camera 20 provides a volumetric reduction of lens space on the order of 78 percent and a total weight reduction on the order of 45 percent compared to previous camera arrangements. In one example, the housing 30 occupies a space of 12 mm×12 mm on the circuit board substrate 24. In some example embodiments, a height of the assembly 22 between the circuit board substrate 24 and the front lens element 28 is less than 10 mm. In some example embodiments, the height is less than 5 mm. In some example embodiments, the camera weight is less than 7 grams, which is significantly less than previous camera arrangements, which would weigh close to 12 grams.
The smaller dimensions of the assembly 22 facilitate a SMT approach, in part, because SMT machines typically require component heights less than 13 mm for reliable pick and place by a standard tool prior to a solder reflow oven process. The ability to use SMT for making the camera 20 provides significant cost savings because it allows for a higher level of automation and process cost savings.
Another feature of the illustrated example is that the pre-alignment of the lens elements 28-32 and the sensor 34 within the assembly 22 increases the reliability and accuracy of the resulting camera. Therefore, there is a lower likelihood that cameras made according to the illustrated technique will fail an inspection or quality testing compared to previous techniques that include mounting a sensor to the circuit board substrate and subsequently mounting the lens assembly and housing to the board with the sensor already in place.
Another reliability enhancement is provided by the disclosed process. Automotive vehicle cameras are potentially subjected to a wide range of temperatures depending on where the vehicle is located. For example, the ambient temperature may range from −40° C. to 105° C. In operation and for high temperature testing, the camera internal temperature is usually 15 to 20 degrees higher than that (e.g. 120° C. to 125° C.). The disclosed technique and camera configuration make it possible to measure the camera image quality at elevated temperatures, such as temperatures up to 125° C. This allows for verification of high temperature performance during the reflow process.
The high temperatures used during the securing within the reflow oven, for example, are also potentially useful for high temperature camera testing. One example embodiment includes using a high temperature harness within the reflow oven to power and access the camera to capture images. According to an example embodiment, an internal camera software program that calculates the image quality metrics is initiated and referenced while the camera is viewing a preselected target when the camera is subjected to a temperature in the range from about 105° C. to about 125° C.
In the example of
One of the features shown in
The objective elements 60 and 62 are configured in this example to create collimated or parallel rays refracting into the interior lens assembly. The result provides an insensitivity in terms of assembly tolerances (e.g., decentering, z-positioning, tilting). If the refracted rays do not focus to the same degree across the plane degrading effects are more pronounced and variable. The objective elements 60, 62 could also allow for additional components such as filters to be inserted into the path of the parallel rays between the objective and the interior lenses without affecting the focus or other aberration corrections because the exiting light is collimated.
Designing the objective elements 60 and 62 to provide the parallel rays at 64 and parallel rays at 66, for example, reduces the sensitivity to such misalignment possibilities. For example, centering tolerances on the order of +/−0.1 mm and tilting tolerances on the order of +/−0.5° are effectively accommodated with an arrangement such as illustrated in
Reducing the entrance pupil to windshield distance and being able to have the sensor of the camera closer to the windshield reduces the distortion introduced by the windshield. Windshield glass has a curvature in horizontal and vertical planes. Those curvatures are typically different than each other. The camera image field is affected by the windshield curvature in a way that increases with increasing distance between the sensor and the windshield.
For example, typical windshield configurations introduce barrel-type distortion. As the distance between the camera sensor and the windshield decreases, the radial distortion is reduced across portions of the field of view. Having a reduced entrance pupil to windshield distance reduces the amount of windshield distortion particularly across the median portion of the field of view of the camera and reduces the total amount of image distortion. The distortion reduction is essentially consistent across the median portion of the field of view regardless of the rake angle of the windshield. This is another way in which the disclosed example camera embodiments provide enhanced performance for automotive vehicle applications, such as advanced driver assist features.
The example of
The assembly process in this example includes aligning the middle assembly 22a with its objective 50 and housing 52a in a desired orientation on the reference surface 130. In the illustrated example, the reference surface 130 includes an opening 132 configured to receive at least a portion of the housing 52a. An adhesive, such as an ultraviolet light-curable adhesive secures the assembly 22a in place. Once the assembly 22a is secured and the adhesive is cured, another one of the assemblies 22b is situated at least partially within an opening 134 in the reference surface 130 with the assembly 22b in a desired orientation and an adhesive secures the assembly 22b in place. The third assembly 22c and its housing 52c is then situated in a desired alignment at least partially within an opening 136 and the assembly 22c is secured in place.
In some examples, the assemblies 22 are arranged on the reference surface 130 to establish stereo vision. In the example of
Cameras made according to an embodiment of this invention provide smaller overall size requirements and cost savings compared to previous camera arrangements. The manufacturing process becomes simpler, subject to a higher amount of automation with increased reliability and improved yield. Example embodiments are adaptable to different optical field of view requirements and are capable of fitting within tight space constraints for realizing multiple field of view devices. The disclosed embodiments also address issues represented by automotive camera installations, such as reducing windshield distortion.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.
