Patent Grant
9405096
This disclosure relates to image sensor modules and, in particular, to image sensor modules that include primary high-resolution imagers and secondary imagers.
Image sensors are used in cameras and other imaging devices to capture images. For example, light entering through an aperture at one end of the imaging device is directed to an image sensor by a beam shaping system (e.g., one or more passive optical elements such as lenses). The image sensors include pixels that generate signals in response to sensing received light. Commonly used image sensors include CCD (charge-coupled device) image sensors and CMOS (complementary metal-oxide-semiconductor) sensors.
Some image sensors include high-resolution primary imagers, as well as secondary imagers that can be used to provide depth information. Various advantages can be obtained by providing the primary and secondary cameras with a small foot print (e.g., both may be positioned on the same semiconductor chip (i.e., on the same sensor)). On the other hand, fabricating such modules with an overall small footprint while at the same time providing the desired optical characteristics can present a range of technical challenges.
This disclosure describes image sensor modules that include two or more imagers. Each of the imagers includes an optical channel having a respective stack of beam shaping elements (e.g., lenses). To achieve desired characteristics for the module, some of the beam shaping elements are formed as a laterally contiguous array, whereas other beam shaping elements are formed as a laterally non-contiguous array.
For example, in one aspect, an optoelectronic module that includes one or more image sensors. The module includes a first imager including a first stack of beam shaping elements disposed over the one or more image sensors to direct incoming light to a first photosensitive region of the one or more image sensors, and a second imager including a second stack of beam shaping elements disposed over the one or more image sensors to direct incoming light to a second photosensitive region of the one or more image sensors. Each particular stack includes a respective high-dispersion beam shaping element. The high-dispersion beam shaping element of the first stack forms part of an achromatic doublet at the object side of the first stack. The high-dispersion beam shaping element in the second stack is part of a laterally contiguous array of beam shaping elements that does not include the high-dispersion beam shaping element that forms part of the achromatic doublet at the object side of the first stack.
Some implementations include one or more of the following features. For example, the high-dispersion beam shaping element in the second stack can be part of a laterally contiguous array of beam shaping elements that includes a field-dependent aberration correction beam shaping element in the first stack. The field-dependent aberration correction beam shaping element in the first stack can be composed of the same material as the high-dispersion beam shaping element in the second stack.
In general, the first stack can include a greater number of beam shaping elements than the second stack. Each of the first and second stacks can include respective beam shaping elements that form an achromatic doublet for chromatic aberration correction and at least one additional beam shaping element for field-dependent aberration correction.
In some cases, the high-dispersion beam shaping element in the second stack also can be part of an achromatic doublet for chromatic aberration correction. Each achromatic doublet further can include a low-dispersion beam shaping element. The module may include a laterally non-contiguous array including the low-dispersion beam shaping element of the second stack and the high-dispersion beam shaping element of the first stack. However, the beam shaping elements that form the achromatic doublet of the first stack preferably are not part of a laterally contiguous array of beam shaping elements.
In some instances, the second stack includes, at its object side, a respective achromatic doublet including a low-dispersion beam shaping element having a positive refractive power and a high-dispersion beam shaping element having a negative refractive power.
Some implementations include one or more of the following advantages. For example, a compact imager can incorporate a high-quality primary imager and one or more secondary imagers for depth information. Preferably, all the imagers capture the same field-of-view. The primary and secondary imagers can be positioned in close proximity so as to reduce the overall footprint of the imager, while at the same time providing the desired optical properties for each channel. In some cases, the primary and secondary imagers may share a common sensor.
Other aspects, features and advantages will be readily apparent from the following detailed description, the accompanying drawings, and the claims.
As shown in
Each imager 28A, 28B includes a respective an optical assembly (i.e., a vertical stack of beam shaping elements (e.g., lenses)) that direct incoming light toward the respective photosensitive region of the corresponding imager. For example, in the illustrated example of
In the illustrated example of
Each lens stack in
In the illustrated example of
The top (object side) lens 30A of the primary channel 28A and the top (object side) lenses 32A of the secondary channels 28B have positive refractive power and can be made of the same or different low-dispersion material. Preferably the lenses 30A, 32A have an Abbe number greater than 55, and a refractive index in the range of 1.51-1.54. Other values may be appropriate for some implementations. The second lens in each channel (i.e., 30B in the primary channel and 32B in the secondary channels) have negative refractive power and can be made of the same or different high-dispersion material. Preferably the lenses 30B, 32B have an Abbe number less than 35, and a refractive index greater than 1.56. Other values may be appropriate for some implementations.
On the other hand, each of the lower two lens arrays 34B, 34C can be formed as a laterally contiguous array. For example, each lens array 34B, 34C can be formed as a monolithic piece that spans across all the imagers 28A, 28B. Thus, all the lenses in a given one of the lateral arrays 34B, 34C are composed of the same high-dispersion of low-dispersion material, even though some of the lenses are associated with the primary imager 28A, and some of the lenses are associated with the secondary imagers 28B. In particular, in the illustrated example, the lenses 30D and 32C in the lateral array 34C are composed of a low-dispersion material, whereas the lenses 30C and 32B in the lateral array 34B are composed of a high-dispersion material. The use of laterally contiguous arrays for the lower lens arrays can help reduce the overall footprint of the module. Although the foregoing feature introduces constraints into the module's design (e.g., the high-dispersion material of the aberration correction lens 30C in the primary imager 28A), other properties of the various lenses can be designed collectively to account for the use of high-dispersion material of the lens 30C in the primary imager 28A. Further, as the lens 30C is designed for aberration correction and provides relatively low refractive power, the chromatic aberration generated by that lens is not significant. Thus, lenses 30C, 32B for different optical channels can be formed as part of a laterally contiguous lens array, where the lens for at least one of the optical channels (e.g., the channel for the secondary imager) is composed of a high-dispersion material and forms part of an achromatic doublet, whereas the lens(es) for another one of the optical channels (i.e., a channel for the primary imager) is designed primarily for field-dependent aberration correction.
The respective field-of-view of the primary and secondary imagers preferably are substantially the same. Thus, the field-of-view of the primary imager 28A (FOV1) is about the same as the field-of-view of each secondary imager 28B (FOV2). The higher resolution requirements for the primary imager 28A necessitate more sensor space than is typically required for the secondary imagers 28B, which can provide lower-quality images. The image-size restrictions on the sensor 22 and the close lateral proximity of the primary and secondary imagers 28A, 28B to one another can result in the secondary imagers having a relatively small focal length or track length (TTL).
In some implementations, in order to prevent the field-of-view of the secondary imagers 28B from being obstructed by the primary imager 28A, the effective total track length (TTL) for each optical lens stack of the secondary imagers 28B can be elongated. This can be accomplished, for example, by replacing some or all of the air gaps between adjacent lenses in a particular lens stack for the secondary imagers 28B with lens material. By replacing the air with a material having a refractive index greater than 1 (e.g., plastic or glass), the track length of the material is made thicker to accommodate the optical material. In effect, the thickness of some or all of the lenses in each secondary imager 28B can be increased to provide a correspondingly higher total track length. Although the precise extent of the increase in thickness of a particular lens will depend on the particular implementation, a general guideline is that the ultimate thickness of the lens material should be about equal to the product of the refractive index of the lens material and the thickness of the air gap that would otherwise be present.
The optical channel for each secondary imager 28B includes an aperture stop that preferably is placed in front of the first lens element. Thus, the aperture stop defines the base of the cone of light entering the secondary imager. Preferably, the aperture stop is placed far in front of the top lens 32A to avoid interfering mechanically with the optical channel of the primary imager 28A. The position of the aperture stop also should be selected to avoid generating optical aberrations (e.g., coma).
In general, the number of lenses stacked vertically for the primary imager 28A will be greater than the number of lenses stacked vertically in each secondary imager 28B, the number of lenses in some, or all, of the lens stacks may differ from that shown in
Some implementations may include more than two secondary imagers each of which can include a stack of beam shaping elements having substantially the same number and properties as the stack of beam shaping elements of the secondary imagers as described above.
The following tables are intended to provide further details relating to one or more implementations of the modules. Tables 1-8 relate to the primary imager; tables 9-16 relate to the secondary imager(s). The details set forth in the tables below may differ in some or all respects for other implementations.
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Various modifications can be made within the spirit of the invention. Accordingly, other implementations are within the scope of the claims.
This application claims the benefit of U.S. Provisional Application No. 62/043,585, filed Aug. 29, 2014, the contents of which are incorporated herein by reference in their entirety.
| Number | Name | Date | Kind |
|---|---|---|---|
| 8662765 | Reshidko et al. | Mar 2014 | B2 |
| 8791489 | Rudmann | Jul 2014 | B2 |
| 9000377 | Rossi | Apr 2015 | B2 |
| 9291504 | Goldring | Mar 2016 | B2 |
| 20160006913 | Kettunen | Jan 2016 | A1 |
| Number | Date | Country |
|---|---|---|
| WO 2015119571 | Aug 2015 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20160062082 A1 | Mar 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62043585 | Aug 2014 | US |
