(19)
(11)EP 2 336 860 A1

(12)EUROPEAN PATENT APPLICATION

(43)Date of publication:
22.06.2011 Bulletin 2011/25

(21)Application number: 10194281.1

(22)Date of filing:  09.12.2010
(51)International Patent Classification (IPC): 
G06F 3/042(2006.01)
G06F 3/03(2006.01)
(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
Designated Extension States:
BA ME

(30)Priority: 10.12.2009 GB 0921644

(71)Applicant: STMicroelectronics (Research & Development) Limited
Marlow, Buckinghamshire SL7 1YL (GB)

(72)Inventor:
  • Raynor, Jeffrey
    Edinburgh, Lothian EH12 5HZ (GB)

(74)Representative: Hayden, Nicholas Mark 
Murgitroyd & Company Scotland House 165-169 Scotland Street
Glasgow G5 8PL
Glasgow G5 8PL (GB)

  


(54)Improvements in or relating to optical navigation devices


(57) Disclosed is an optical navigation device, a method of controlling the illumination of an optical navigation device. The optical navigation device comprises: a navigation radiation source capable of producing a beam of radiation; an optical element for identifying movement of an object to thereby enable a control action to be carried out; a sensor for receiving an image based upon reflected radiation from the navigation radiation source; and one or more illumination radiation sources for illuminating the optical navigation device. The device is operable in recurrent cycles of at least reset, expose and readout phases and to activate the illumination radiation source only during the reset phase, the reset phase having the longest duration of all the phases. Also disclosed is a mobile computing device, mobile telecommunications device and/or remote control device, comprising such an optical navigation device.




Description


[0001] 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.

[0002] Current mobile or computer devices use a variety of different navigation mechanisms. Some of these present a mousing surface for direct manipulation by a finger (or other part of the body), and work by producing images of the finger as it moves on the mousing surface, translating this finger movement to movement of a cursor (for example) on a screen. In this respect a navigation device of this type works in a similar fashion to an optical mouse, and is referred to as an optical navigation device.

[0003] It is often desirable to have an optical navigation device backlit. However, this can lead to performance degradation should the backlight remain on constantly. This means that the backlight illuminates the mousing surface and degrades the contrast of a fingerprint, thereby reducing the signal-noise ratio of the acquired image.

[0004] It is an object of the invention to address the above issue.

[0005] In a first aspect of the invention there is provided an optical navigation device comprising
  • a navigation radiation source capable of producing a beam of radiation;
  • an optical element for identifying movement of an object to thereby enable a control action to be carried out
  • a sensor for receiving an image based upon reflected radiation from said navigation radiation source; and
  • at least one illumination radiation source for illuminating said optical navigation device;
wherein said device is operable in recurrent cycles of at least reset, expose and readout phases and to activate said at least one illumination radiation source only during said reset phase, said reset phase having the longest duration of all the phases.

[0006] Said device preferably also operates in a calibration phase. Said device may operate in cycles of said reset, calibration, expose and readout phases, said reset phase being operable to reset the sensor to a predetermined level, said calibration phase being operable to determine the appropriate sensor output level in the absence of light, said expose phase for obtaining said image and said readout phase for outputting said image.

[0007] Said reset phase may have a duration comprising 50% or more of the total duration of each cycle of phases.

[0008] Said device may be operable to switch off said illumination radiation source shortly before the end of said reset period.

[0009] Said device may be operable not to activate said illumination radiation source during cycles in which said sensor receives images indicative of movement of said object and/or images with detectable features.

[0010] Said device may be operable such that the duration that said illumination radiation source is activated during each reset cycle is variable so as to control illumination intensity. Preferably said device is further operable such that said duration that said illumination radiation source is activated does not alter the duration of said reset phase.

[0011] Said device may be operable such that said illumination radiation source is controllable by said navigation device and/or a host device in which said navigation device is comprised. Said illumination radiation source may be activated dependent upon a status of said navigation device and/or said host device.

[0012] Said device may be operable such that the duration of each of said cycles of phases may be variable, such that the device may operate in a number of modes.

[0013] Said device may comprise a plurality of illumination radiation sources.

[0014] Each one of said plurality of illumination radiation sources may be arranged to illuminate different portions of said navigation device.

[0015] Said plurality of illumination radiation sources may output visible light, each with a different colour. In a main embodiment, there may be three such illumination radiation sources, each outputting an additive primary colour.

[0016] Said device may be operable to only turn one of said plurality of illumination radiation sources on at one time. Said device may be further operable to allow two or more of said plurality of illumination radiation sources to be turned on during a single reset period, such that the ratio of durations that each illumination radiation source is turned on determines the perceived illumination colour. Said ratio may be controllable by said navigation device and/or a host device in which said navigation device is comprised. Said ratio may be dependent upon a status of said navigation device and/or said host device. Said device may be operable to set said ratio proportionally, with a further parameter to set illumination intensity.

[0017] Said device may be operable such that each one of said illumination radiation sources is able to be turned on for substantially the full reset phase duration. Alternatively, the device may be operable such that each one of said illumination radiation sources is able to be turned on for only a proportion of the reset phase duration, said proportion being substantially the reciprocal of the number of illumination radiation sources.

[0018] Said optical element may be formed from a single piece construction and may include at least one frustrated total internal reflection (F-TIR) surface capable of causing frustrated total internal reflection of the beam of radiation when said object contacts said first surface to thereby generate the image which is capable of being translated into said control action. The optical element may comprise at least one further surface for directing radiation from the radiation source to at least one F-TIR surface. The optical element may comprise at least one additional surface for directing radiation from the F-TIR surface to the sensor.

BRIEF DESCRIPTION OF THE DRAWINGS



[0019] Embodiments of the invention will now be described, by way of example only, by reference to the accompanying drawings, in which:

Figure 1 is a cross-sectional diagram of an optical navigation device, suitable for application of the present invention, given by way of example,

Figure 2 is an optical diagram of the figure 1 device, given by way of example,

Figure 3 is a timing diagram for a prior art optical navigation device with illumination;

Figure 4 is a timing diagram for an optical navigation device with illumination according to a first embodiment of the invention;

Figure 5 is a schematic drawing of an optical navigation device according to said first embodiment of the invention;

Figure 6 is a timing diagram for an optical navigation device with illumination according to a second embodiment of the invention;

Figure 7 is a timing diagram for an optical navigation device with illumination according to a third embodiment of the invention;

Figure 8 is a schematic drawing of an optical navigation device according to said second and third embodiments of the invention; and

Figure 9 is a schematic drawing of an optical navigation device according to a further embodiment of the invention.


DETAILED DESCRIPTION OF THE EMBODIMENTS



[0020] The present invention relates to an optical navigation device module 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.

[0021] Figures 1 and 2 show a particular type of optical navigation device module suitable for the application of the present invention. This optical navigation device module is described in detail in co-pending application number GB0908899.8. It should be noted that this optical navigation device is described by way of example only, and any suitable optical navigation device using reflection off a mousing surface can be used.

[0022] The optical navigation device module 100 includes a base plate 102, an optical element 106 which incorporates a clip 104 (the optical element will be described in greater detail below), an illumination source 108, such as an LED, and a sensor 110. The overall construction of the optical navigation device module 100 is of a low profile construction making it suitable for mobile devices. The actual size of the overall package containing the optical navigation device sits under a cap of about 7mm in diameter and the module itself has a maximum dimension of about 5.8 mm.

[0023] 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.

[0024] As can be seen in Figure 2, this particular type of optical navigation device uses the optical layout for a frustrated total internal reflection (F-TIR) device 200, although direct imaging systems and other systems are equally applicable to be used in place of the F-TIR device 200.

[0025] 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.

[0026] 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.

[0027] 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 in any 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 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.

[0028] 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.

[0029] 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).

[0030] 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.

[0031] The optical navigation device may have a backlight provided by an LED separate to the LED 202, which provides the radiation source for the sensor 206. However, should the backlight remain on constantly, performance degradation can result. This is because the backlight illuminates the mousing surface and degrades the contrast of a fingerprint, thereby reducing the signal-noise ratio of the acquired image.

[0032] For good contrast of the fingerprint, the illumination optics ideally produces a collimated beam of light at an oblique angle (i.e. as close as possible to the plane of the surface) as possible. In comparison, the backlighting optics produces a smooth distribution of light over the surface and is as homogenous as possible. Hence the photons from the backlighting system do not provide good contrast of surface texture.

[0033] The backlight naturally uses wavelengths in the visible band while it is common for the navigation LED to be infra-red (IR). The longer wavelength IR photons penetrate the silicon deeper before generating electron-hole pairs. A significant portion of the photo generated charge from the IR / navigation source will be generated in the bulk of the substrate which is usually highly doped. As a result the electron-hole pairs will recombine quickly and not be collected, and the device will have a reduced quantum efficiency. Hence, if the photon flux for the visible (backlighting) LED is the same as the IR (navigation) LED, the detector will receive a greater amount of (unwanted) signal from the visible (backlit) LED compared to the signal from the IR (navigation) LED and the image contrast will be further degraded.

[0034] Figure 3 shows a typical timing diagram of prior art sensor operation. It shows a sensor operating in repeated cycles of four phases, during which the levels of the sensor photodiode voltage VPD, the reset line RST, the navigation LED NAVLED and the Backlight LED, BACKLED are shown. The four phases are: a reset phase where the sensor's pixels are all reset to a predetermined voltage level, a black calibration phase whereby the sensor is calibrated so as to determine the appropriate output level in the absence of light, an expose phase where the sensor obtains an image and a readout phase, where the obtained image is read out for comparison to previous images to determine motion. This basic cycle of phases is well known for any imaging sensor.

[0035] The timing arrangement of Figure 3 attempts to solve the above signal degradation problem by turning the backlighting LED off during part of the frame so it does not interfere with the navigation operation. While it is possible to turn the backlighting LED on during dark calibration, this is disadvantageous as it would produce an offset into the pixel and reduce the dynamic range. Turning the backlight LED on during either exposure (Texpose) or readout (Treadout) will cause the degradation problems described above. Hence only if the backlight is turned on during the reset phase (Treset1) will the backlighting not degrade the imaging / navigation system.

[0036] Normally this reset period (Treset1) is a short period (10µs) compared to the total frame period (100µs). Consequently, if this period is used to provide backlighting, the resulting duty cycle of the backlight is low (10% typical). This would produce a dim back light unless the peak current through the backlighting LED was increased accordingly. It is common for LEDs to be operated in this mode and their maximum current is typically dependent on the duty cycle of operation (thermal dissipation limits, so 1A at duty cycle of 10% equals 100mA constant).

[0037] However, this operation is undesirable in a mobile device as the large maximum current presents additional demands on the device's power management circuitry and the effect of voltage drops becomes more significant.

[0038] A mouse/navigation device sensor operation is different to that of a still camera / video camera / webcam in that the mouse/navigation device sensor can control the lighting. A significant further difference is that of frame-rate. For good performance (especially to avoid temporal aliasing - c.f. spokes on a wheel appearing to rotate backwards on TV/film) the mouse sensor operates at 1kHz-10kHz frame rate compared to 10-50Hz of a DSC/webcam. To achieve high frame rates, not only should the pixel be very sensitive to light (US6969879, incorporated herein by reference describes such a sensitive pixel) but the mode of operation should be such that for most of the frame time it is sensitive to light, and the time of the non-imaging periods should be reduced.

[0039] For example, Figure 3 shows equal time for the black calibration phase Tblackcal and readout phase Treadout, however black calibration phase Tblackcal is typically shorter than readout phase Treadout, using the technique described in US7502061 (hereby incorporated by reference).

[0040] Figure 4 is a timing diagram illustrating the operation of a navigation device with backlighting system according to an embodiment of the invention. The lines shown and phases (other than duration) are the same as that illustrated in Figure 3. However, the reset phase (Treset2) has now been lengthened and is now the longest phase in the system. It is preferable that the period for which the backlight LED is on, TbLED2 is shorter than the reset phase Treset2, so that (a) the navigation device photo sensor does not detect any photons from the backlighting system, and (b) the backlighting LED is turned off in advance of the reset pulse so that the disturbance on the supply rails caused by turning off the current through the LED has disappeared before the pixel comes out of reset.

[0041] It will be appreciated that the above operational embodiment will result in a significant reduction of the frame rate. However, the inventor has determined that the higher frame rates required for a conventional optical desktop mouse are not necessarily required for smaller optical navigation devices such as illustrated in Figures 1 and 2 (although a frame rate much higher than cameras etc. is still required). This is because finger motor skills used when operating a finger operated device tend to be slower then arm motor skills used when operating a desktop mouse.

[0042] The width of the backlight LED (TbLED2) pulse can be varied to change the average intensity of the backlighting. Preferably, although not necessarily, the reset (Treset2) pulse stays the same length and does not vary as the backlight LED (TbLED2) pulse varies. This keeps the frame length (Tframe2) constant which simplifies the calculation of speed of the mouse. If necessary (e.g. in power saving modes), there may be provided a set of frame (Tframe2) periods so that the frame rate of the mouse can be adapted to the mode of operation (e.g. high speed motion, medium speed motion, low speed motion, no motion & short sleep, no motion and medium sleep and no motion and long sleep period).

[0043] Instead of having just one output from the navigation device sensor, it is possible to have several outputs to control several LEDs. These may be of the same colour and designed to co-operate with the illumination optics to each illuminate only part of the surface (e.g. brighter centre and darker periphery or vice-versa), or else they may be of different colours for aesthetic or technical reasons.

[0044] Figure 5 shows an optical navigation device according to said first embodiment of the invention. It comprises optical sensor 10, a navigation Light Emitting Diode (LED) 20 and a white or tricolour backlighting LED 30.

[0045] Figure 6 illustrates such an arrangement where there are 3 separate illumination LED outputs, BACKLEDR, BACKLEDG, and BACKLEDB, each with different pulse widths. Although this represents a possible solution, it is not optimal as it results in either 0, 1, 2 or 3 backlighting LEDs illuminating at any one time, hence there is a large variation in the total supply current. This may pose problems for the system's power management block.

[0046] Figure 7 illustrates an alternative arrangement to that illustrated in Figure 6. In this embodiment the pulses for the backlighting LED channels BACKLEDR, BACKLEDG, BACKLEDB are non-overlapping. They are set such that as one turns off another is turned on. Not only does this reduce the maximum current required for backlighting to 1/3 of the system shown in Figure 6 (assuming same current through each LED colour), but it keeps the current drain roughly constant during the reset period. In both cases this helps to minimise the inrush current into the mouse module.

[0047] Figure 8 shows an optical navigation device according to said first embodiment of the invention. It comprises optical sensor 10, a navigation Light Emitting Diode (LED) 20 and three backlighting LEDs, red 30r, green 30g and blue 30b.

[0048] In the illustrated example, the LEDs are red, green and blue, these being additive primary colours that allow an illumination output in the other visible colours of the spectrum. In the specific example shown, the blue LED signal (BACKLEDB) is on for about the same period as the green LED signal (BACKLEDG) but only half the time of the red LED signal (BACKLEDR), i.e. duration of signal TbbLED4 equals duration of signal TbgLED4 equals 2 x duration of signal TbrLED4. The ratio of the periods sets the colour of the backlight. For optimal navigational performance the total duration of signals TbbLED4, TbgLED4 and TbrLED4 is less than the duration of Treset4. The actual width / duty cycle of the backlighting pulse can be set in variety of manners.

[0049] Figure 9 shows a variation on the optical navigation device according to Figure 8. In this, only two illumination LEDs are provided, a red and green bi-colour LED 30rg and a blue LED 30b.

Host controlled Backlighting



[0050] The navigation device has, in some embodiments, a memory (e.g. 12C or SPI register) which the host controller of the host device (for example, phone, MP3 player or similar portable media player (PMP), Digital Still camera, satellite navigation system, remote control) can access to program the brightness / colour / width of the backlighting LED pulse. This can be useful for a variety of applications / enhancements of the device, for example

Phone:



[0051] 
  • · Backlight illuminates on incoming phone call or SMS message.
  • Backlight changes colour depending on if there is phone call or SMS message (e.g. white for incoming call and red for incoming text message).
  • ·Backlight illuminates with colour depending on caller ID of incoming phone call / SMS message (e.g. white for most calls, red for certain persons or group of persons, green for others etc.).
  • · Backlight colour indicates battery power level - e.g. if battery levels are below a threshold then the navigation device backlight is commanded to illuminate red.
  • · Backlight illuminates when the phone is being charged. It could be commanded to change colour to indicate either the level of charge or time remaining to fully charge the unit.
  • · Backlight colour indicates RF signal strength - e.g. if received signal strength is above a certain threshold then the backlight could be commanded to show green light, similar to the number of "bars" on a conventional display.
  • · Backlight could be commanded to illuminate or change colour when keys are depressed- The colour of the backlight could be commanded to change if the keys are depressed while the keylock is engaged.

MP3 player / PMP:



[0052] 
  • · Backlight colour indicates battery power level - e.g. if battery levels are below a threshold then the navigation device backlight is commanded to illuminate red.
  • · Backlight illuminates or changes colour when the player is charging.
  • · Backlight illuminates or changes colour when data is uploaded to the media player (e.g. red).
  • · Backlight illuminates or changes colour when data is downloaded from the media player (e.g. green).
  • · Backlight illuminates to indicate an "illegal operation" e.g. trying to reduce the volume control to below zero or above the maximum level.
  • · Backlight illuminates or changes colour to warn the user - e.g. the volume is commanded to exceed a preset level.
  • · The intensity or colour of the backlight is used to indicate the volume level.
  • · The intensity and/or colour of the backlight can change in harmony with the sound being played, e.g. high average sound level produces a brighter backlight and the spectral content of the audio is mapped onto the colour of the illumination (e.g. predominantly low-frequency audio tones control the red LED, mid-tones to green LED and high frequency tones the blue LED).
  • · Backlight colour / intensity indicates that the player has successfully connected to a host computer.

Camera (digital still)



[0053] 
  • · Backlight illuminates or changes colour when the camera is acquiring an image.
  • · Backlight illuminates or changes colour when the camera is processing an image.
  • · Backlight illuminates, flashes or changes colour when the camera is in "self timer" mode, waiting to acquire an image (e.g. 8 x green backlighting pulses at 1 second intervals followed by 2 x red backlighting flashes just before the image is captured).
  • · Backlight illuminates, flashes or changes colour to indicate an error condition - e.g. under exposure, over exposure, long exposure (longer than can be comfortably handheld), camera's memory store (SD/CF/xD/MS/SM) is full.
  • · Backlight illuminates, flashes or changes colour to indicate that the camera is in a nonstandard or unusual mode of operation (e.g. manual focus, manual white balance, manual exposure).
  • · Backlight colour indicates battery power level - e.g. if battery levels are below a threshold then the navigation device backlight is commanded to illuminate red.
  • · Backlight colour / intensity indicates the camera has successfully connected to a host computer

Satellite Navigation System:



[0054] 
  • · Backlight illuminates, flashes or changes colour to indicate that the user is approaching their destination
  • · Backlight illuminates, flashes or changes colour to warn the driver of an approaching manoeuvre
  • · Backlight illuminates, flashes or changes colour to warn the driver of an approaching road traffic restriction (e.g. change in speed limit).
  • · Backlight colour indicates battery power level - e.g. if battery levels are below a threshold then the navigation device/fingermouse backlight is commanded to illuminate red
  • · Backlight colour / intensity indicates the SatNav device has successfully connected to a host computer

Remote Control



[0055] 
  • · Backlight colour indicates battery power level - e.g. if battery levels are below a threshold then the navigation device backlight is commanded to illuminate red.
  • · Backlight colour / intensity indicates which controlling mode the remote control is operating in (e.g. red for DVD, blue for BlueRay, white for TV, green for radio etc.)

Navigation Device Controlled Backlighting



[0056] The backlighting can also be controlled by the navigation device itself, as illustrated by the following examples.

Motion



[0057] When the device detects that there is motion over the surface of the sensor, the backlighting can be inhibited to reduce energy consumption (as the user's finger is probably obscuring the surface, it is not sensible to use energy to illuminate the user's finger as the lighting cannot be observed).

Features



[0058] It is common for navigation device engine to detect the presence or absence of features on the surface. This signal can also be used to control (e.g. enable / disable) the backlighting.

Co-operative Controlled Backlighting



[0059] As well as independent control by either the host or the navigation sensor, it is desirable to have co-operative control. In this mode the host would command the sensor to illuminate one / several / all LEDs, but this be gated with information from the sensor. For example,



[0060] In the example shown above, the host would request that the RED LED was turned on (for example to indicate a. low battery warning), but only at the appropriate time, that is in the absence of motion over the surface of the sensor (i.e. finger not moving on the surface). This gating can be easily controlled by setting / clearing appropriate control bits via 12C or SPI register command.

Absolute Period lengths Vs percentage



[0061] The pulse widths of the LED may be set via a dedicated 12C memory location (e.g. 0x01 = 2µs, 0x02 = 4µs etc.) or else there may be proportional or percentage values stored, along with a global fader value, for example
Register Address,Register Name,Register Function
N, REDPERCENT, 0=LED off, 255 (FF)=LED maximum
N+1, GREENPERCENT, 0=LED off, 255 (FF)=LED maximum
N+2, BLUEPERCENT, 0=LED off, 255 (FF)=LED maximum
N+3, FADER, 0=All LEDs ofif,255(FF)=LED setting


[0062] The host could then program in a particular colour, e.g. pink
N ← 0xFF # Red value
N+1 ← 0xC0 # Green value
N+2 ← 0xCB # Blue value

[0063] This could be turned on with
N+3 ← 0xFF
and the navigation device LED control would calculate the periods for TbrLED4 TbgLED4 & TbbLED4 such that the total of these periods is less than the period of Treset4.

[0064] If the period Treset4 changes (e.g. due to change from navigation engine), the device would automatically adjust the periods of TbrLED4 TbgLED4 & TbbLED4 to maintain the correct ratio. Further, if the host wished to dim the backlight and keep the same colour, only a single register write is required.

On-Chip Ambient Light Sensor



[0065] Should the navigation device sensor integrate an ambient light detector (for an example, see applicant's co-pending application- attorney ref P113944.GB.01) not only should the navigation LED be disabled when device is measuring ambient light, but also the background illumination should be disabled when the device is measuring ambient light. The sensor for detecting ambient light may, in an embodiment, be the same sensor as the navigation device sensor.

[0066] The above embodiments are for illustration only and other embodiments and variations are possible and envisaged without departing from the spirit and scope of the invention. For example the actual type of optical navigation device is not relevant so long as it is of a type that uses a radiation device and sensor to determine movement and at least a further radiation device for illumination. Also, the above non-exhaustive list of possible examples are purely illustrative of the utility of the invention disclosed herein.


Claims

1. An optical navigation device comprising

- a navigation radiation source capable of producing a beam of radiation;

- an optical element for identifying movement of an object to thereby enable a control action to be carried out

- a sensor for receiving an image based upon reflected radiation from said navigation radiation source; and

- at least one illumination radiation source for illuminating said optical navigation device;
wherein said device is operable in recurrent cycles of at least reset, expose and readout phases and to activate said at least one illumination radiation source only during said reset phase, said reset phase having the longest duration of all the phases.


 
2. An optical navigation device as claimed in claim 1 operable in cycles of reset, calibration, expose and readout phases, said reset phase being operable to reset the sensor to a predetermined level, said calibration phase being operable to determine the appropriate sensor output level in the absence of light, said expose phase for obtaining said image and said readout phase for outputting said image.
 
3. An optical navigation device as claimed in claim 1 or 2 wherein said reset phase has a duration comprising 50% or more of the total duration of each cycle of phases.
 
4. An optical navigation device as claimed in any preceding claim being operable not to activate said illumination radiation source during cycles in which said sensor receives images indicative of movement of said object and/or images with detectable features.
 
5. An optical navigation device as claimed in any preceding claim being operable such that the duration that said illumination radiation source is activated during each reset cycle is variable so as to control illumination intensity, the variation in said duration that the illumination radiation source is activated not altering the duration of said reset phase.
 
6. An optical navigation device as claimed in any preceding claim being operable such that said illumination radiation source is activated dependent upon a status of said navigation device and/or said host device.
 
7. An optical navigation device as claimed in any preceding claim being operable such that the duration of each of said cycles of phases is variable, such that the device may operate in a number of modes.
 
8. An optical navigation device as claimed in any preceding claim comprising a plurality of illumination radiation sources, wherein each one of said plurality of illumination radiation sources is arranged to illuminate different portions of said navigation device.
 
9. An optical navigation device as claimed in any preceding claim comprising a plurality of illumination radiation sources, operable such that said plurality of illumination radiation sources outputs visible light, each with a different colour.
 
10. An optical navigation device as claimed in claim 9 wherein there are three such illumination radiation sources, each outputting an additive primary colour, said device being further operable to allow two or more of said illumination radiation sources to be turned on during a single reset period, such that the ratio of durations that each illumination radiation source is turned on determines the perceived illumination colour.
 
11. An optical navigation device as claimed in claim 10 being operable to set said ratio proportionally, with a further parameter to set illumination intensity.
 
12. An optical navigation device as claimed in claim 10 or 11 being operable to achieve a perceived constant illumination intensity for different colours by adjusting the actual illumination intensity to allow for the human eye's relative sensitivities to different colours.
 
13. An optical navigation device as claimed in claim 12 being operable to further adjust for different efficiencies in different colour radiation sources to achieve said perceived constant illumination intensity.
 
14. An optical navigation device as claimed in any preceding claim comprising an ambient light detector wherein said device is operable to turn off said illumination radiation source when said ambient light detector is activated.
 
15. A method of controlling the illumination of an optical navigation device comprising
producing a beam of radiation, and sensing a resultant received image based upon reflected radiation from said beam, said image being dependent on movement of an object, so as to identify said movement of said object to thereby enable a control action to be carried out,
wherein said device operates in recurrent cycles of at least reset, expose and readout phases and said device is illuminated only during said reset phase, said reset phase having the longest duration of all the phases.
 
16. A mobile computing device, mobile telecommunications device and/or remote control device, comprising the optical navigation device of any of claims 1 to 14.
 




Drawing






















Search report










Cited references

REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description