Image sensor modules including primary high-resolution and secondary imagers

An optoelectronic module includes one or more image sensors including photosensitive regions. The module includes a first imager including a first stack of beam shaping elements disposed over the image sensor(s) to direct incoming light to a first photosensitive region, and a second imager including a second stack of beam shaping elements disposed over the image sensor(s) to direct incoming light to a second photosensitive region. Each particular stack includes a respective high-dispersion beam shaping element, where the high-dispersion beam shaping element of the first stack forms part of an achromatic doublet at an 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.

TECHNICAL FIELD

This disclosure relates to image sensor modules and, in particular, to image sensor modules that include primary high-resolution imagers and secondary imagers.

BACKGROUND

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.

SUMMARY

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.

DETAILED DESCRIPTION

As shown inFIG. 1, an optoelectronic module includes a high-resolution primary imager28A and one or more secondary imagers28B having a combined footprint that is relatively small. For example, in some implementations, the primary and secondary imagers28A,28B may share a common image sensor22. The image sensor22can be implemented, for example, using CCD (charge-coupled device) or CMOS (complementary metal-oxide-semiconductor) technology and can be mounted, for example, on a printed circuit board (PCB) or other substrate20. The image sensor22includes photosensitive regions24. The primary camera28A is operable to collect signals representing a primary two-dimensional (2-D) image; the secondary cameras can be used to provide additional secondary 2-D images that, for example, may be used for stereo matching and thus can provide three-dimensional (3-D) images or other depth information.

Each imager28A,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 ofFIG. 1, each optical channel in the primary imager28A includes a stack of four lenses30A,30B,30C,30D. The lenses30A-30D are stacked one over the other, with the lens30A at the top of the stack (i.e., the object side) and the lens30D at the bottom of the stack (i.e., the sensor side). Each of the second imagers28B also includes a respective stack of three lenses32A,32B,32C. The lenses32A-32C are stacked one over the other, with the lens32A at the top of the stack (i.e., the object side) and the lens32C at the bottom of the stack (i.e., the sensor side). The lens stacks can be disposed over a common transparent substrate26that spans across all of the optical channels.

In the illustrated example ofFIG. 1, each lens stack includes an achromatic doublet composed of the two lenses closest to the object side. These lenses can provide chromatic aberration correction. In some cases, they also may provide additional optical functions (e.g., magnifying power). Thus, the lenses30A and30B in the primary imager28A form an achromatic doublet in which the upper lens30A is composed of a low-dispersion material and is shaped to provide positive refractive power, and the lower lens30B is composed of a high-dispersion material whereas is shaped to provide negative refractive power. Likewise, the lenses32A and32B in each secondary imager28B form an achromatic doublet in which the upper lens32A is composed of a low-dispersion material and is shaped to provide positive refractive power, whereas the lower lens32B is composed of a high-dispersion material and is shaped to provide negative refractive power.

Each lens stack inFIG. 1also includes at least one lens, for example, near the sensor side of the module for field-dependent aberration correction. In particular, the lenses30C and30D in the primary imager28A provide such aberration correction, and the lens32C in each secondary imager provides such aberration correction. In some cases, these lenses30C,30D,32C also may provide additional optical functions.

In the illustrated example ofFIG. 1, the module includes three lateral arrays34A,34B,34C of beam shaping elements. The lateral array34C near the sensor side of the module consists of lens30D in the primary imager28A and lenses32C in the secondary imagers28B. The next adjacent lateral array34B consists of lens30C in the primary imager28A and lenses32B in the secondary imagers28B. The lateral array34A consists of lens30B in the primary imager28A and lenses32A in the secondary imagers28B. The array34A is formed as a laterally non-contiguous array, which allows the lenses in the different stacks to be formed of different materials and to be placed at the same or slightly different vertical positions. For example, as already mentioned, the lens30B in the primary imager28A is composed of a relatively high-dispersion material, whereas the lenses32A in the secondary imagers28B are composed of a relatively low-dispersion material.

The top (object side) lens30A of the primary channel28A and the top (object side) lenses32A of the secondary channels28B have positive refractive power and can be made of the same or different low-dispersion material. Preferably the lenses30A,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 and32B in the secondary channels) have negative refractive power and can be made of the same or different high-dispersion material. Preferably the lenses30B,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 arrays34B,34C can be formed as a laterally contiguous array. For example, each lens array34B,34C can be formed as a monolithic piece that spans across all the imagers28A,28B. Thus, all the lenses in a given one of the lateral arrays34B,34C are composed of the same high-dispersion of low-dispersion material, even though some of the lenses are associated with the primary imager28A, and some of the lenses are associated with the secondary imagers28B. In particular, in the illustrated example, the lenses30D and32C in the lateral array34C are composed of a low-dispersion material, whereas the lenses30C and32B in the lateral array34B 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 lens30C in the primary imager28A), other properties of the various lenses can be designed collectively to account for the use of high-dispersion material of the lens30C in the primary imager28A. Further, as the lens30C is designed for aberration correction and provides relatively low refractive power, the chromatic aberration generated by that lens is not significant. Thus, lenses30C,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 imager28A (FOV1) is about the same as the field-of-view of each secondary imager28B (FOV2). The higher resolution requirements for the primary imager28A necessitate more sensor space than is typically required for the secondary imagers28B, which can provide lower-quality images. The image-size restrictions on the sensor22and the close lateral proximity of the primary and secondary imagers28A,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 imagers28B from being obstructed by the primary imager28A, the effective total track length (TTL) for each optical lens stack of the secondary imagers28B 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 imagers28B 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 imager28B 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 imager28B 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 lens32A to avoid interfering mechanically with the optical channel of the primary imager28A. 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 imager28A will be greater than the number of lenses stacked vertically in each secondary imager28B, the number of lenses in some, or all, of the lens stacks may differ from that shown inFIG. 1. Thus, for example, in some cases, the primary imager can include a stack of more than four lens elements (e.g., five), and each secondary imager can include a stack of more than three lens elements (e.g., four). In other instances, the primary imager can include a stack of five lens elements, and each secondary imager can include a stack of three lens elements. In any event, the upper two lenses in each particular channel can form an achromatic doublet designed for chromatic aberration correction. In the secondary imagers, the top (object side) lens in each particular channel preferably has positive refractive power, and the adjacent lens in the same particular channel preferably has negative refractive power. The remaining lens elements in each stack can be designed to correct for field-dependent aberraation.

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.

TABLE 7Index of refraction data - primary imagerSystem Temperature:20.0000 CelsiusSystem Pressure:1.0000 AtmospheresAbsolute air index:1.000273 at wavelength 0.546100 μmIndex data is relative to air at the system temperature and pressure.wavelengths are measured in air at the system temperature and pressure.SurfGlassTempPres0.4358000.4861000.5461000.5876000.656300020.001.001.000000001.000000001.000000001.000000001.00000000120.001.001.000000001.000000001.000000001.000000001.00000000220.001.001.000000001.000000001.000000001.000000001.000000003<MODEL>20.001.001.557064831.551708901.547239331.544919011.54196599420.001.001.000000001.000000001.000000001.000000001.000000005<MODEL>20.001.001.673960731.657414651.644356531.637900031.63004742620.001.001.000000001.000000001.000000001.000000001.000000007<MODEL>20.001.001.673960731.657414651.644356531.637900031.63004742820.001.001.000000001.000000001.000000001.000000001.000000009<MODEL>20.001.001.546994851.541710021.537301711.535014011.532103441020.001.001.000000001.000000001.000000001.000000001.0000000011<MODEL>20.001.001.526686491.522377861.518722941.516800011.514323901220.001.001.000000001.000000001.000000001.000000001.000000001320.001.001.000000001.000000001.000000001.000000001.00000000

TABLE 15Index of refraction data - secondary imager(s)System Temperature:25.0000 CelsiusSystem Pressure:1.0000 AtmospheresAbsolute air index:1.000268 at wavelength 0.600000 μmIndex data is relative to air at the system temperature and pressure.wavelengths are measured in air at the system temperature and pressure.SurfGlassTempPres0.5650000.5750000.6000000.6800000.720000025.001.001.000000001.000000001.000000001.000000001.00000000125.001.001.000000001.000000001.000000001.000000001.00000000225.001.001.000000001.000000001.000000001.000000001.000000003<MODEL>25.001.001.536198511.535657641.534418361.531284071.53006255425.001.001.000000001.000000001.000000001.000000001.000000005<MODEL>25.001.001.641213421.639692381.636258771.627915381.62480421625.001.001.000000001.000000001.000000001.000000001.000000007<MODEL>25.001.001.536198511.535657641.534418361.531284071.53006255825.001.001.000000001.000000001.000000001.000000001.000000009<MODEL>25.001.001.517798061.517342991.516296071.513620411.512566121025.001.001.000000001.000000001.000000001.000000001.000000001125.001.001.000000001.000000001.000000001.000000001.000000001225.001.001.000000001.000000001.000000001.000000001.00000000

Various modifications can be made within the spirit of the invention. Accordingly, other implementations are within the scope of the claims.