The present invention claims priority from British Patent Application No. 0908899.8 filed May 26, 2009 and British Patent Application No. 0913000.6 filed Jul. 27, 2009, the disclosures of which are hereby incorporated by reference.
1. Technical Field
The present invention relates to improvements in or relating to optical navigation devices, particularly but not exclusively in respect to miniature devices for use in a variety of different applications.
2. Description of Related Art
Current mobile or computer devices use a variety of different navigation mechanisms. Touch screen panels are navigated by means of direct contact with screen. Other devices make use of trackball devices where a mechanical signal is translated into position data to enable the navigation to occur. A further navigation device makes use of a multi-click joystick to enable the necessary navigation. There are problems associated with each of the currently available navigation mechanisms. The touch screen panel has been shown to be somewhat unreliable while the trackball and joystick may also be unreliable as well as relatively expensive to implement.
For larger scale computer devices optical mice have been used for some time for navigation purposes. These devices are generally too large and impractical for mobile applications due to ergonomic and economic issues. In addition, miniaturization of typical optical mice has not proved successful to date.
There is a need to overcome at least some of the problems associated with the prior art.
There is further a need to apply optical mouse technology to the mobile computer domain.
According to one aspect there is provided an optical navigation device for a computer application, comprising: a radiation source capable of producing a beam of radiation; a sensor for receiving an image; an optical element for identifying movement of a feature to thereby enable a control action to be carried out; wherein the optical element is formed from a single piece construction and includes at least one frustrated total internal reflection (F-TIR) surface capable of causing frustrated total internal reflection of the beam of radiation in the presence of the feature to thereby generate the image which is capable of being translated into said control action.
In a further aspect there is provided computer device, or a mobile telephone comprising the optical navigation device herein described, wherein the term “computer device” is to be construed as including at least: mobile telephones, mobile media players, such as MP3 players, TV/DVD remote control, SatNav systems, digital cameras etc.
Reference will now be made, by way of example, to the accompanying drawings, in which:
a is an example of
b is a more detailed example of the
An optical navigation device module is presented for use in a device. The device may be of any appropriate type and may include mobile phones, PDAs, Laptop computers, TV remotes, games controls and other such devices herein referred to as a computer application.
Referring to
The optical element 106 may be molded from a single piece of plastic and provides a so called mousing surface 112. An example of the type of plastic material is a monolithic optical block made of a plastics material such as poly (methyl methacrylate) also known as PMMA; although it will be appreciated other materials (such as Polycarbonate, Cyclcyclophane copolymer) may alternatively be used.
The optical navigation device module 100 is essentially split into three main functions or components: an optical interface to the mousing surface 112; the adaptation of the optical elements to provide additional advantages in terms of mechanical construction; and the interface of the mouse or optical navigation device with the user. The specific optical design maximizes the accuracy of the navigation process in a low profile package. The optics also enable the mechanical advantages that are described in the United Kingdom Patent Application No. 0908900.4 of 26 May 2009.
Referring now to
The F-TIR device 200 includes an LED 202 which emits a source of radiation directed by optical element 204 to the internal surface 210 of the mousing surface 112. A further optical element 208 then directs any reflected radiation from surface 210 on to sensor 206.
The LED 202 may be of any appropriate type and may be mounted on a substrate. In a particular example the LED emits in the near infrared range for example between about 700 to 900 nm. It should be noted that the radiation emitted by the LED may be any appropriate wavelength. If the radiation is in the UV, optical or IR ranges the radiation may be referred to as illumination.
The optical element 204 directs the LED illumination into the monolithic optical block which forms the optical element 106. The optical element 204 may be shaped as appropriate to form for example a single convex surface; a series of lenslets configured as a “fly eye” structure; or any other suitable structure capable of providing near collimated or near focused illumination at the internal surface 210. The optical element 204 may be capable of being tilted in order to control the illumination pattern and direction of the beam at the mousing surface. Since optical element 204 is part of an illumination system the use of a single tilted surface can be extended to a multiple lenslet system (also known as a “fly-eye lens”), where the individual lenslets can be tilted to improve control of the illumination pattern at the mousing surface 112. A fly-eye lens is shown in
The mousing surface 112 includes an internal surface 210 and an external surface 212. At the mousing surface any object with a refractive index which is placed in contact with the external surface 212 will frustrate the total internal reflection of the beams 214 at the internal surface 210. A suitable object may include a finger, pointer, hand or other object or feature. A so-called frustrated reflection will thus be generated and the resulting pattern is focused by optical element 208 onto the sensor 206.
The internal surface 210 is relatively smooth when compared to the features which give rise to the F-TIR. Illumination reflected from the internal surface 210 when there is no object close to the mousing surface is virtually 100% reflected. However, when the reflection is frustrated only about 10% or less of the illumination is reflected, thus resulting in contrast ratio of about 1:10 in the present example. Note that at 850 nm most of returned signal is from scattering at the object in contact with the optical element 106 (e.g. the skin of the user's finger).
The optical element 208 may be of any appropriate form, for example a single convex surface; and includes a stop (not shown) so that an image of F-TIR surface is produced at the sensor.
Ideally the optical stop on 208 is such that its numerical aperture matches that of the rest of the system. The numerical aperture of the system can be dictated by several means. Firstly it can be generated by surface texture on the mousing surface 112 being such that it scatters the incident collimated radiation into a given angular profile. In this case the optical element 208 focuses the radiation from mousing surface 112 onto the sensor 206. Also the stop can be generated by having a similar texture to any of the other surfaces intervening between the LED source 202 and lens 208, including the LED transparent package surface. In these cases, the lens 208 focuses the light from the mousing surface 112 onto the sensor 206 and the F-TIR pattern is seen as a occlusion to the true image. The LED 202 may be replaced by an extended light source, such as an organic light emitter, which on viewing from the sensor 206 subtends the sensor area. In this case the surface of the light source is imaged at the sensor 206 by way of the lens 208. Alternatively the aperture end of the collimating lens 204 may be extended to allow all imaged points of the mousing surface 112 to be subject to radiation at all angles presented to the collimating lens 204 by the extended source. This allows the lens 208 to image the mousing surface 112 onto the sensor 206.
The sensor 206 may be any appropriate type and is designed to be of maximum size within the constraints of the package. In one embodiment the sensor is made up of an array of (20×20) 30 μm pixels. Other sizes and resolutions of sensor or pixels may be used instead.
The frustrated reflection directed on to the sensor is detected in order to identify the point or points of contact of the object in contact with the external surface 212. Subsequent measurements of the point or points of contact will provide information corresponding to the movement of object on the external surface 212. The action or movement of the object can then be translated into actions to operate a mobile personal computer.
The system works at a frame rate of 1 to 10 kHz in order to detect relative movement or movements of one or more features at the F-TIR. The features detected at the F-TIR are features between about 0.5 mm and 30 μm in size and correspond, for example, to finger print features of a user. The smaller features provide a greater ability to detect motion than the larger ones. To detect features of about 30 μm, an increased resolution of the sensor and an increased quality of the optics used in the F-TIR device 200 can be advantageous. The sensor operates to determine motion vectors of one or more features from one frame to the next in accordance with the frame rate. Correlation from one frame to the next identifies the motion vectors and rate of movement which can then be translated into an appropriate control action for the mobile computer.
The frame rate is set by the refresh rate of the sensor. The exposure may be achieved by a pulsating illumination source (LED) or by sampling the sensor output at the required rate.
It may be possible to calibrate the sensor by determining the sensor illumination when there is no radiation source for F-TIR and comparing this with the sensor, when detecting F-TIR. This calibration may occur at the start of each use of the optical navigation device or on a frame to frame basis.
The relative positions and angles between the TIR surfaces and the F-TIR mousing surface are shown in
As previously indicated, the angles and positions of the folding TIR and F-TIR surfaces can be adjusted. One such adjustment is to replace TIR fold surface 300 with a biconic surface and adjust the angle of incidence to optimize the irradiance at the F-TIR surface. This can serve to reduce the overall size of the package containing the optical navigation device.
The system magnification for the optical navigation device is in the region of −1 to −0.1; although a preferred value is in the range −0.8 to −0.3.
It should be noted that ensuring that the main beam from the LED arrives at the “pupil” is not necessarily optimal. The lens apex of optical devices 204 can be off-set from the centre of the stop and the sensor off-set from the center of the lens to ameliorate the effects of the variation in object distance (e.g. tombstone distortion). The centre of the image does not necessarily need to coincide with the main beam from the LED.
A further embodiment (not shown) may be implemented using a double bounce orientation. The double bounce is used to bring the mousing surface closer to being parallel to the imaging surface thus improving the resolution and reducing the distortion of the image on which mousing is preformed. To control the illumination intensity and directional distribution at the mousing surface (as can be seen in
Referring now to
The undulating surface also lends itself to the use of a visibly clear plastic where the light scattered away from the objective lens aperture can be reflected off the lower surface of the optics to output a visible signal, which may be used to indicate status of a mobile or computer device.
Referring now to
The optical navigation device is suitable for use in any device which makes use of a navigation device. For example, the optical navigation device may be used on a mobile computer, phone, a remote controller or any other appropriate device.
On the mousing surface 112 of the optical navigation device module 100, a rectangular imaged area 802 is shown. The imaged area 802 demonstrates an area stretched in one particular direction in which movements of a feature are detected. The direction in which the imaged area 802 is stretched corresponds with the direction of a longitudinal axis 804 of the imaged area 802. The longitudinal axis 804 of the imaged area 802 is parallel to an axis 806 connecting the radiation source 202 and the sensor 206 and the imaged area 802 is located at the centre of the F-TIR mousing surface 112. The imaged area 802 is stretched in one direction because the F-TIR surface is at an angle to the plane of the sensor 206. This can be explained for example with the reflection of radiation which is sent through a prism formed like a trapezoid. This radiation is reflected from the longer basis side of the prism at a larger area along this basis side than in a direction perpendicular to the basis side in the plane of the basis side. An image on the sensor 206 resulting from movements of a feature on the mousing surface 112 is compressed along the longitudinal axis 804 of the imaged area 802 because the image is focused on the sensor 206, which is for example square shaped. This leads to a lower resolution along the direction in which the imaged area 802 is stretched because a lower number of pixels are detected per imaged period. So the sensitivity of the imaged area 802 is increased along the direction in which it is stretched.
Because of the angle in which the radiation is reflected from the F-TIR surface, astigmatism occurs, i.e. radiation from the sagittal plane does not focus at the same point than radiation from the tangential plane. This leads to the effect that an image is sharp along a first direction but blurred along a second direction when the best focus point is set for a spatial frequency in the first direction, or blurred along the first direction and sharp along the second direction when the best focus point is set for a spatial frequency in the second direction. The effects of the astigmatism can be reduced by focusing the radiation reflected from the mousing surface 112 at the circle of least confusion, i.e. at an intermediate focal length where diagonal spatial frequencies appear clear. As the image on the sensor 206 is compressed along the longitudinal axis 804 (second direction), a better contrast for the corresponding spatial frequencies in the first direction can equilibrate the sensitivity between movement along the first and second direction. This can be obtained by focusing the radiation from the mousing surface 112 between the circle of least confusion and the position where spatial frequencies in the first direction appear sharper.
The longitudinal axis 804 of the imaged area 802 is perpendicular to a longitudinal axis 808 of the device 800 and parallel to an axis 810 perpendicular to the longitudinal axis 808 on the F-TIR mousing surface 112. When the device 800 is operated by a user directly in front of the device 800 and the optical navigation device module 100 is used with a user's finger 812 or a pointer not shown in
An angle included by the longitudinal axis 804 of the imaged area 802 and the longitudinal axis 808 of the device 800 does not have to be exactly 90° as shown in
It will be appreciated that this invention may be varied in many different ways and still remain within the intended scope and spirit of the invention.
Number | Date | Country | Kind |
---|---|---|---|
GB0908899.8 | May 2009 | GB | national |
GB0913000.6 | Jul 2009 | GB | national |