1. Field of the Invention
Aspects of the invention relate to an image motion sensor using a microlens array, and more particularly, to an optical navigation module using a flat type microlens array.
2. Description of the Related Art
Conventionally, optical navigation modules (i.e., computer mice) come in a wide variety of shapes having different features and sizes and prices. Computer mice are divided up according to how the motion is sensed. Specifically, optical mice use optical motion sensing. In contrast, mechanical mice use mechanical motion sensing. While the mechanical mice were the earlier of the two types of computer mice, the optical mice have begun to gain increased acceptance.
Early versions of optical mice relied upon fine lines on a specific grid in order to perform tracking operations. However, with the advent of an optical position sensor by Agilent Technologies in 1999, optical mice are now able to work on a wide variety of surfaces without requiring the fine line grids. The optical position sensor works by taking a picture of the surface on which the mouse is navigating, and comparing images taken sequentially to detect the speed and direction of the movement of the surface relative to the mouse. In this manner, the optical mouse is able to navigate across a wide variety of surfaces without requiring such a grid.
In contrast to early optical mice and mechanical mice which used a ball to perform the tracking operation, an optical mouse typically does not use a ball. Specifically, the mouse includes a clear lens underneath. Light from a light source (generally an LED emitting a red wavelength light) reflects off the surface and is received through a window at the lens. The lens focuses the received light on a sensor, which detects the image. As such, as the mouse is moved, the sensor takes continuous images of the surface and compares the images to determine the distance and direction traveled utilizing digital signal processing. The results are then sent to the computer or other computational device in order to move the cursor on the screen.
Such transmission to the computer can be either directly through a cord, which often supplies energy for use in powering the mouse, or using a cordless mouse, which uses RF technology or Bluetooth in order to transmit the navigational data to the computer. Where a cordless optical mouse is used, an onboard power source such as a battery is used in order to power a light source and a sensor of the mouse.
However, the conventional lens used in an optical mouse is a single lens. The single lens requires an increased focal length and has a thickness which increases the thickness/form factor of the resulting mouse. Moreover, the single lens is fabricated by injection molding and is then joined together with separate components, such as the sensor, which increases the fabrication costs.
Other lenses or lens arrays have been used and described in the past in the context of imaging for human consumption, such as for cameras and/or large screen displays. For example, WO 00/64146 describes a lens array used for conventional imaging for human consumption. However, due to problems with optical cross talk and ghosting caused when light from one lenslet is focused on an incorrect sensor pixel, such lens arrays need to perform trade offs between image quality and light sensitivity in order to have high quality images with respect to color, sharpness, and contrast. Additionally, in order to prevent image distortion, there needs to be a highly accurate alignment between the pixels and the corresponding lens as well as complex blocking structures to prevent ghost images and other effects of optical cross talk between pixels. Thus, the thrust of investigation into microlens arrays has been to resolve these problems in order to make microlens arrays useful for cameras. There has been no suggestion of the use of such arrays in other contexts, such as in the context of optical navigation modules.
Aspects of the invention relate to a motion sensing apparatus utilizing a microlens lens array to performing imaging, and more particularly, to utilizing a microlens array.
Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
According to an aspect of the invention, an optical motion sensing module includes a microlens array comprising a plurality of lenslets, each lenslet forming a corresponding image of a surface; a light sensor comprising a plurality of pixels corresponding to the plurality of lenslets to detect the formed images of the surface; and a controller to use the detected images to determine a motion of the surface relative to the optical navigation module.
According to an aspect of the invention, the optical motion sensing module further includes a light source to direct light at the surface, wherein the microlens array forms the images of the surface using the light reflected from the surface.
According to an aspect of the invention, the microlens array is disposed less than 10 mm from the surface.
According to an aspect of the invention, the microlens array is bonded to the light sensor.
According to an aspect of the invention, the microlens array further comprises an aperture for each lenslet to prevent optical cross talk at the pixels between adjacent images formed by adjacent lenslets.
According to an aspect of the invention, the microlens array has a rectangular shape such that the lenslets extend in parallel.
According to an aspect of the invention, the microlens array has a curved shape such that the lenslets extend in circumferentially around at least one center.
According to an aspect of the invention, the microlens array has a circular shape such that the lenslets extend circumferentially around the center of the circular shape.
According to an aspect of the invention, the microlens array has an elliptical shape such that the lenslets extend circumferentially around the centers of the elliptical shape.
According to an aspect of the invention, the optical motion sensing module includes a light source to emit light used by the microlens array to form the images, wherein the light sensor is disposed on a surface with the light source.
According to an aspect of the invention, the light source further comprises a light guide surrounding at least one of the pixels of the light sensor, and a light emitter to emit light into the light guide such that the light guide guides the light to reach the surface.
According to an aspect of the invention, the optical motion sensing module includes a light source to emit light used by the microlens array to form the images, wherein the light sensor includes a layer of light emitting material.
According to an aspect of the invention, each lenslet forms the corresponding image of the surface on the corresponding pixel at a corresponding offset from a centerline of the lenslet, and an amount of the offset varies as a function of distance from an edge of the light sensor.
According to an aspect of the invention, the offset increases as a function of distance from a center of the light sensor toward an edge of the light sensor.
According to an aspect of the invention, the microlens array further comprises an aperture system which prevents multiple images from non-corresponding lenslets from being formed on a same pixel.
According to an aspect of the invention, each lenslet has a diameter in a range at or between 5 to 200 microns, and a height of the microlens array is in a range at or between 5 to 500 microns.
According to an aspect of the invention, each lenslet corresponding to one of the pixels, and a number of pixels of the light sensor is in a range at or between 50 to 2,000 pixels.
According to an aspect of the invention, a computer mouse for use in navigation on a surface includes a base having a window through which light reflected from the surface passes; a body on top of the base plate forming an interior cavity with respect to the base; a microlens array disposed in the cavity and having a plurality of lenslets which receive the light from the window and form a corresponding number of images at varying offsets on a focal plane; a sensor disposed in the cavity and having a plurality of pixels disposed at the focal plane and which detect the formed images; and a controller disposed in the cavity and which detects motion of the mouse relative to the surface according to the detected images of the sensor and transmits the detected motion to an associated device.
According to an aspect of the invention, the sensor is a CMOS sensor.
According to an aspect of the invention, the computer mouse further comprising includes a light source within the cavity which produces the light to be reflected off the surface and received at the microlens array after passing through the window, wherein the light source is disposed relative to the microlens array such that an illumination field of the light on the surface corresponds to a field of view of the microlens array to reduce optical cross talk.
According to an aspect of the invention, the body allows ambient light to reflect off the surface and received at the microlens array after passing through the window.
According to an aspect of the invention, the microlens array further comprises an aperture system which prevents multiple images from non-corresponding lenslets from being formed on a same pixel.
According to an aspect of the invention, each lenslet corresponds to one of the pixels, and the number of pixels is in a range at or between 50 to 2,000 pixels.
These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.
Extending from the body 12 is a cord 14. The cord 14 transfers power and/or detected direction signals with respect to a computer or other device (not shown) to which the optical navigation module is connected. However, it is understood that the cord 14 may be replaced by a transmitter for a wireless mouse 10, and/or that power may be internally supplied instead of being transferred from a computational device.
On top of the body 12 is a button or button array 16. The button array 16 is used by a user to input signals, such as by clicking. However, it is understood that a button 16 is not required in all aspects of the invention, and it is possible to input signals through other mechanisms, as in the case of game controllers, or to integrate the button into the connection between the body 12 and the base 18 to input signals by pressing the body 12.
The mouse 10 includes an internal kit used to detect motion due to relative motion of reflected light as detected by comparing images. As shown in
A light source 26 outputs a light beam which is reflected through a lens pipe 20 to be reflected off of the surface 5 through an opening in the base plate 18. The reflected light passes through a window 28 in the base plate and is received at a microlens lens array 30 according to an aspect of the invention. Specifically, the light is focused by the microlens array 30 onto a sensor 22 to produce multiple images of the surface 5. The sensor 22 can be a conventional CMOS image sensor or a CCD sensor according to aspects of the invention.
The image detected at the sensor 22 is detected by a chip 24. The chip 24 performs a comparative analysis over time of successive images in order to determine a direction and speed of the movement of the mouse 10. Specifically, the chip 24 includes firmware which compares present images detected by the pixels 61-67 of the sensor 22 with images taken at a previous time, and the difference reveals the relative motion of the mouse 10 to the surface 5. The resulting output is output through the cord 14 using a PCB 27. However, it is understood that various elements of the shown mouse 10 need not be used in all aspects of the invention. For example, the use of the light pipe 20 need not be used and/or the use of an LED as the light source 26 can be replaced by other light sources.
While existing optical mice use a similar construction for many of the parts, the conventional optical mouse includes a single objective lens focusing an image onto a sensor as a single image. In contrast, as shown in
The use of the aperture 58 is used to prevent ghost images to provide an increased contrast and sharpness of the image of the surface 5. Ghost images occur when light from one lenslet reaches an adjacent pixel, thereby creating a false image at that adjacent pixel. By controlling the illumination field 40 through placement of the light source 26 and using the aperture 58, the ghosting and cross talk can be reduced. Moreover, since the existence of ghost images is not fatal in the context of optical motion sensing, the aperture 58 need not be used even where the light source 26 is not used to control the illumination field 40 (such as when using ambient light). However, the use of the aperture 58 and/or the light source 26, along or in combination, is preferred in order to provide a higher contrast image and improve the image motion detection.
However, it is understood that, while shown in
An example of such an embodiment is shown in
According to an aspect of the invention, where no offset is used, in order to prevent overlap and ghost images, the field of view of each lenslet is reduced in relation to a distance between the surface 5 and the microlens array 30 since, the greater the distance, the greater likelihood of overlap. Thus, the field of view of each lenslet is directed at a small angle so that the field of view of one lens does not overlap substantially with a field of view of an adjacent lenslet. While shown as focusing light along the centerline, it is understood that each lenslet could focus light at a same angle according to another aspect of the invention.
Where ghosting of the images is of lesser importance, such as where the light source 26 is focused at a preset angle onto the surface 5, the aperture 58 need not be used as shown in
While many different shapes of the microlens array 30 are possible,
While use in existing optical navigation modules is possible since the illuminated surface 5 are a few tens of centimeters from the microlens array 30, the microlens array 30 allows for smaller distances between the surface 5 and the microlens array 30. Such smaller distances are on the order of a few millimeters, making for a small form factor. Preferably, for a small form factor, the distance from the microlens array 30 to the surface 5 is less than three millimeters. As such, the microlens array could be used in travel applications, such as for providing optical navigation for smaller portable electronic devices like cell phones and personal digital assistants.
Moreover, whereas existing uses of lens arrays, such as that shown in PCT Publication WO 00/64146 in
Additionally, while the microlens array 30 can be separately attached and/or have a layer between the array 30 and the sensor 22, the microlens array 30 may be bonded directly to the sensor 22 according to an aspect of the invention. Such direct bonding would allow for reduced fabrication cost, greater ease in pixel-lenslet alignment, and a lower form factor as compared to conventional lenses. The microlens array 30 can be fabricated using any optical material normally used for lenses. By way of example, glass, plastic or a plastic photoresist may be used according to an aspect of the invention. Specifically, the photoresist can be used at a wafer level scale by forming the lenses 51-57 through a resist reflow process.
In the resist reflow process, the resist is placed on a wafer, the resist is lithographically patterned to correspond to the pixel layout, and then heat is generated in order to reflow the resist to form the individual lenses 51 through 57 through surface tension. Alternately, an optical material can be formed into the microlens array 30 through processes such as injection molding, preferably at wafer level.
While seven lenslets 51 through 57 are shown in
According to an aspect of the invention, the light source 26 can be an LED or other like light emitting device. According to an aspect of the invention, the light source 26 is a laser which produces interference patterns due to features of the surface. The interference patterns are imaged by the microlens array 30 to detect motion.
Additionally, while shown in
Alternately, as shown in
While shown in
While described in the context of optical navigation modules, it is understood that aspects of the present invention can be used in general motion sensing where image quality is not of paramount importance. As such, the microlens array of the present invention can be used in the context of thin optical security motion sensors by detecting relative image motions. Similarly, the microlens array can be used in proximity sensors, and/or scanners. Also the microlens lens array can also be implemented in the context of an image stabilization system, such as is used in a camcorder or other like camera.
Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.