KR20070026614A - Optical positioning device having shaped illumination - Google Patents

Abstract

One embodiment relates to an optical displacement sensor for sensing relative movement between a data input device and a surface (304) by determining displacement of optical features in a succession of frames. The sensor includes an illuminator and a detector. The illuminator has a light source and illumination optics (506) to illuminate a portion of the surface (510) with a planar phase-front. The detector has a plurality of photosensitive elements (502) and imaging optics (512). The illuminator and the detector are configured such that the illuminated portion of the surface (510) is less than fifty percent larger than a field of view of the photosensitive elements (502) of the detector. Other embodiments are also described. ® KIPO & WIPO 2007

Description

Optical Positioning Device with Shaped Illumination {OPTICAL POSITIONING DEVICE HAVING SHAPED ILLUMINATION}

Related Applications

This application, filed on May 21, 2004, finds inventor Clinton B. Clinton B. Carlisle, Zaha I. Jahja I. Trisnadi, Charles B. Charles B. Roxlo, and David A. Claims priority of US provisional application 60 / 573,394, entitled "Optical position sensing device having shaped illumination," by David A. LeHoty. The US provisional patent application referred to above is hereby incorporated by reference in its entirety.

The present application is also filed on May 21, 2004, the inventor David A. David A. LeHoty. Douglas A. Douglas A. Webb, Charles B. Charles B. Roxlo, Clinton B. Clinton B. Carlisle, and Zaha. Of "Optical position sensing device having a detector array using different combinations of shared interlaced photosensitive elements" by Jahja I. Trisnadi. Claims priority of U.S. Provisional Patent Application 60 / 573,075. The US provisional patent application referred to above is hereby incorporated by reference in its entirety.

<Technology field>

The present invention relates generally to an optical positioning device (OPD) and a method for sensing movement using the same.

Pointing devices, such as computer mice and trackballs, are used to enter and interface data to personal computers and workstations. Such devices allow for quick repositioning of the cursor on the monitor and are useful in many text, database, and graphic programs. The user controls the cursor, for example, by moving the mouse on the surface and moving the cursor by a distance proportional to the mouse movement in one direction. In other cases, hand movements on a stationary device may be used for the same purpose.

Computer mice come in both optical and mechanical versions. Typically, a mechanical mouse uses a rotating ball to detect movement and a pair of shaft encoders in contact with the ball to move the cursor by generating a digital signal used by a computer. One problem with mechanical mice is that they are inaccurate and prone to breakdown after continued use due to dust accumulation and the like. In addition, the movement of the mechanical elements, in particular the shaft encoder, and the resulting wear limit the useful life of the device.

One solution to the above-mentioned problems with mechanical mice has been the development of optical mice. Optical mice have become very widespread because they may provide more robust and better pointing accuracy.

The dominant prior art used in optical mice is a light emitting diode (LED) that illuminates the surface with grazing incidence, and a two-dimensional complementary metal-oxide-semiconductor (CMOS) that captures the resulting image. It depends on the detector and the software that correlates the successive images to determine the direction, distance, and speed the mouse is moving. The technique typically provides good accuracy but at low optical efficiency and relatively high image processing requirements.

Another approach uses a one-dimensional array of photo-detectors or detectors, such as photodiodes. Successive surface images are captured by imaging optics, converted to photodiodes, and compared to detect mouse movement. Photodiodes can be wired directly into groups to facilitate motion detection. This reduces photodiode requirements and allows for rapid analog processing. One example of such a mouse is disclosed in US Pat. No. 5,907,152 to Danliker et. Al.

By Dandlicker et al. The mouse disclosed in US Pat. No. 5,907,152 differs from standard technology in that it uses a coherent light source such as a laser. Light from the coherent light source scattered at the rough surface produces a random intensity distribution of light known as speckle. The use of speckle-based patterns has several advantages, including efficient laser-based light generation and high contrast images, even under normal illumination of incidence. This makes the system more efficient and saves current consumption, which is advantageous in wireless applications to extend battery life.

While significant advances have been made in conventional LED-based optical mice, these speckle-based devices have not made fully satisfactory advances for a variety of reasons. In particular, mice using laser speckles generally did not exhibit the accuracy typically required in today's modern mice where it is desirable to have path errors of less than or about 0.5%.

The present disclosure discusses and provides solutions to certain problems with conventional optical mice and other similar optical pointing devices.

<Overview of invention>

One embodiment relates to an optical displacement detector that determines displacements of optical features in successive frames to detect relative movement between the data input device and the surface. The detector includes at least one illuminator and a detector. Illuminators have illumination sources and illumination optics that illuminate portions of the surface. The detector has a plurality of photosensitive elements and imaging optics. The illuminator and detector are configured such that the illuminated portion of the surface is 50% or less larger than the field of view (FOV) of the detector's photosensitive elements.

Another embodiment is directed to a method of detecting relative movement between a data input device and a surface by determining displacement of optical properties in successive frames. Illumination is generated from the light source, which is mapped by the illumination optics to a part of the surface. Illumination is reflected from the illuminated portion of the surface, and by the imaging optics, the reflected illumination is mapped into an array of photosensitive elements of the detector. The illuminated portion of the surface is 50% or less larger than the FOV of the photosensitive elements.

Another embodiment relates to an optical displacement detector that determines the displacement of optical features in successive frames to sense relative movement between the data input device and the surface. The detector includes at least a light source, illumination optics, an array of photosensitive elements, and imaging optics. The illumination optics is adapted to illuminate a portion of the surface in a first form, and the arrangement of photosensitive elements comprises a second form similar to the first form. Imaging optics are adapted to map the light reflected from the illuminated portion of the surface such that the reflected light covers the array of photosensitive elements.

Other embodiments are also disclosed.

These and various other features and advantages of the present invention will be more fully understood from the following detailed description of the accompanying drawings, but are not intended to limit the scope of the appended claims to the specific embodiments shown, but are for illustration and understanding only. It should be understood as.

1A and 1B show speckles of a diffraction pattern of light reflected from a flat surface and an interference pattern of light reflected from a rough surface, respectively.

2 is a functional block diagram of a speckle-based mouse in accordance with one embodiment of the present invention.

3 is a block diagram of a photodiode array according to an embodiment of the present invention.

4 is a functional block diagram of light collection optics in accordance with an embodiment of the present invention.

5 is an optical diagram illustrating structured illumination in accordance with an embodiment of the present invention.

6 is a functional block diagram illustrating two axes of detector elements, each having a plurality of rows, in accordance with one embodiment of the present invention.

7 illustrates various arrangements of detector elements in accordance with one embodiment of the present invention.

One problem with conventional speckle-based optical positioning devices is the possibility of misalignment of reflected illumination with the detector to cover the entire photodiode array of the detector. In order to reliably cover the entire detector array, conventional OPDs are typically configured to illuminate a wider portion of the image plane than the FOV of the detector, so that the entire photodiode array is prevented by reflected illumination in spite of potential misplacement problems. Make sure it is covered.

However, having a large illumination area reduces the energy intensity of the reflected light that the photodiode detects. Therefore, attempts to solve or avoid the misplacement problems of conventional OPDs frequently result from the loss of reflected light available to the photodiode array, or have placed higher requirements on the illumination energy.

As discussed in detail below, one aspect of the present invention discloses a solution to the problems of illumination misplacement and inefficiency discussed above.

Disclosed herein OPD Examples

The present disclosure generally relates to a sensor for an OPD and a method for sensing relative motion between a sensor and a surface based on displacement of a random intensity distribution pattern of light, known as speckle, reflected off the surface. will be. The OPD includes, but is not limited to, an optical mouse or trackball for entering data into a personal computer.

In the context of the present invention, reference to "one embodiment" or "embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. . The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

In general, a detector for an OPD combines an illuminator with a light source and illumination optics to illuminate a portion of the surface, a detector with multiple photosensitive elements and imaging optics, and a signal from each photosensitive element to output an output signal from the detector. Signal processing or mixed-signal electronics for generating the electronic device.

In one embodiment, detectors and mixed-signal electronics are fabricated using standard CMOS processes and equipment. The detectors and methods of the present invention use a combination of analog and digital electronics to structure structured phase-front and telecentric speckle-images as well as simplified signal processing configurations. It is desirable to provide an optically efficient detection architecture by the use of illumination. This architecture reduces the amount of power provided to displacement-estimates in signal processing and detectors. It is found that a detector using a properly configured speckle-detection technique in accordance with the present invention may meet or exceed all performance criteria typically expected for OPD, including maximum displacement velocity, accuracy, and% path error rate. It became.

Speckle Introduction to -based displacement detectors

This section discusses the principle of operation of a speckle-based displacement detector as understood and believed by the applicant. These principles of operation are useful for understanding, but it is not intended that embodiments of the present disclosure be limited by these principles.

Referring to FIG. 1A, the laser light of the indicated wavelength is shown on the surface as a first incident wave 102 and a second incident wave 104, each of which forms an incident angle θ with respect to the surface normal. Diffraction pattern 106 results in a period of λ / 2sinθ.

In contrast, referring to FIG. 1B, any common surface with morphological irregularities of dimensions greater than the wavelength of light (ie, greater than about 1 μm) scatters light 114 in a complete hemisphere in a approximately Lambertian fashion. Let's go. Using a coherent light source such as a laser, the spatially coherent scattered light produces a complex interference pattern 116 upon detection by a square law detector with finite aperture. The complex interference pattern 116 in the bright and dark areas is referred to as speckle. The exact nature and contrast of speckle pattern 116 depends on the surface roughness, the wavelength of light and its spatial coherence, and the light-integrated or imaging optics. Although often very complex, speckle pattern 116 is an obvious feature of any rough surface section imaged by the optics, thereby identifying a location on the surface as it is displaced across the laser and optics-detector assembly. It can be used to

The speckle is expected to be of any magnitude reaching the spatial frequency set by the effective aperture of the optical system, generally defined by its numerical aperture NA = sinθ as shown in FIG. 1B. According to the next Goodman [J. W. J. W. Goodman is the author and Jay. See you. "Statistical Properties of Laser Speckle Patterns" in "Laser Speckle and Related Phenomena", edited by JC Dainty, Topics in Applied Physics volume 9, Springer-Verlag (1984) —see, in particular, pages 39-40]. The size statistic distribution is expressed in intensity auto-correlation. The "average" speckle diameter may be defined as

Is the wavelength of the coherent light.

By Wiener-Khintchine theory, it is interesting to note that the spatial frequency spectral density of speckle intensity is simply a Fourier transform of intensity auto-correlation. The finest possible speckle, a _min = lambda / 2NA, is that the main contribution comes from the extreme light ray 118 of FIG. 1B (i.e., the light at ± θ) and the contribution from most of the internal light rays It is set by an almost impossible case of destructive interference. Thus, the cut-off spatial frequency is fco = 1 / (λ / 2NA) or 2NA / λ.

Note that the aperture ratio may be different for spatial frequencies in the image along the first axis (eg, "x") rather than along the orthogonal axis "y". This may occur, for example, by light apertures with a longer first axis than other axes (eg elliptical instead of circular), or by anamorphic lenses. In these cases, the speckle pattern 116 is also anisotropic, with the average speckle size being different on the two axes.

One advantage of laser speckle-based displacement sensing is that it can operate with illumination light reaching a near normal angle of incidence. In addition, sensors employing incoherent light and imaging optics that reach the grazing incidence angle on rough surfaces may be employed for transverse displacement sensing. However, the grazing incidence angle of the illumination can be used to create a reasonably large bright-dark shadow of the surface topography in the image, so that when a significant portion of the light does not contribute to the image formed by reflecting in a specular manner from the detector, the system Is inherently low in light efficiency. In contrast, speckle-based displacement detectors can efficiently utilize larger portions of the illumination light from the laser source, thus allowing the development of light efficient displacement detectors.

Speckle Disclosed Design for a Based-Based Displacement Detector

DETAILED DESCRIPTION OF THE EMBODIMENTS Hereinafter, a detailed description is given of a laser speckle using a CMOS photodiode with a low power light source, an appropriate amount of digital signal processing circuit and an analog signal combination circuit, such as, for example, a 850 nm Vertical Cavity Surface Emitting Laser (VCSEL). Describe the architecture for a -based displacement detector. While the following detailed description describes specific implementation details, those skilled in the art will appreciate that other light sources, detectors or photosensitive elements, and / or other circuits for combining signals without departing from the spirit and scope of the invention. It will be appreciated that it may be used.

Hereinafter, a speckle-based mouse according to an embodiment of the present invention will be described with reference to FIGS. 2 and 3.

2 is a functional diagram of a speckle-based system 200 according to one embodiment of the invention. System 200 includes a laser source 202, illumination optics 204, imaging optics 208, at least two sets of a plurality of CMOS photodiode arrays 210, front-end electronics 212, A signal processing circuit 214, and an interface circuit 216. Photodiode array 210 may be configured to provide displacement measurements along two orthogonal axes, x and y. Photodiode groups in each array may be combined using passive electronic components in front end electronics 212 to generate a group signal. The group signals can then be combined algebraically sequentially by the signal processing circuit 214 to generate a (x, y) signal that provides information about the magnitude and direction of the displacement of the OPD in the x and y directions. . The (x, y) signal may be converted by the interface circuit 218 into x, y data 220 that may be output by the OPD. Detectors using this detection technique may have an array of interlaced linear photodiode groups known as “differential comb arrays”.

3 shows a typical (along one axis) configuration of such a photodiode array 302, the surface 304 being illuminated by an incoherent light source such as illumination optics 308 and VCSEL 306, and the array The combination of interlaced group at 302 functions as a periodic filter on the spatial frequency of the light-dark signal generated by the speckle images.

The speckle produced by the rough surface 304 is mapped to the detector plane with the imaging optics 310. Imaging optics 310 are telecentric for optimal performance.

In one embodiment, comb array detection is performed with two independent orthogonal arrays to obtain displacement estimates of x and y. 3, a small version of one such array 302 is shown.

Each array in the detector consists of N sets of photodiodes, each set having M photodiodes PD arranged to form an MN linear array. In the embodiment shown in FIG. 3, each set consists of four photodiodes 4 PD, referred to as 1,2,3,4. The PD1s from all sets are electrically connected (wired sum) to form groups such as PD2, PD3 and PD4 to provide four signal lines from the array. The corresponding currents or signals are I ₁ , I ₂ , I ₃ and I ₄ . These signals I ₁ , I ₂ , I ₃ and I ₄ may be referred to as group signals. Background suppression (and signal emphasis) includes a differential analog circuit 312 that generates an in-phase differential current signal (314; I ₁₃ = I ₁ -I ₃ ), and a quadrature differential current signal. signal; 318; I ₂₄ = I ₂ -I ₄ ). These in-phase and quadrature signals may be referred to as line signals. Phase comparison of I ₁₃ and I ₂₄ allows the direction of movement to be detected.

In order to suppress the introduction of phase error, which can be converted directly into displacement error, the detector of the present invention preferably uses a plurality of comb arrays. Moreover, although the embodiments described herein use a "4N" scheme for individual arrays, the system design principle is for other array configurations or schemes, such as 3N, 5N, 6N, 7N, 8N, and the like. Applicable (with appropriate modification). The term " 4N " is such that each fourth detector is wired together, and the resulting four photocurrent signals are subtracted from each other as described in Dandliker et al. (US Pat. No. 5,907,152). However, many other groups are possible with an appropriate scheme of combining the signals.

In general, an example of an image or light integrated optical system 402 is shown in FIG. 4. Light is scattered into the area A _S of the surface 404 and imaged by the detector 406 of the area A _det . For Lambertian surfaces, the detector integration efficiency is expressed as:

Where η _optics is the efficiency of the optical components (absorption, Fresnel reflection, etc.), r is the effective surface reflectance, Ω _S is the solid angle to the surface, and Ω _det is the solid angle to the detector.

Shaped lighting

Applicants assume that the illumination light is planar or has a constant phase-front, one way to maintain good optical efficiency is to custom design the illumination footprint to closely match the detector footprint in size and shape. I believe you have found it. It is more desirable that the lighting footprint is sufficiently full to provide the desired margin for minor misplacements resulting from operation and manufacturing.

One embodiment of such structured illumination is shown in FIG. 5. One characteristic shown in FIG. 5 is that only these locations on the optical surface in the FOV of the imaging optics are illuminated. Ideally, the illumination optics 504 is optimal optical efficiency if the photodetector array or the geometry of the arrays is unusual or asymmetrical, such as the "L" shape with respect to the detector arrangement 502 shown in FIG. 5. For this purpose, only the area should be illuminated on the rough surface. Light dimmed on rough surfaces outside this FOV area is wasted and reduces the net efficiency of the optical positioning system.

In one implementation, the asymmetric (eg non-circular) shape of the illuminated portion will not be a direct image of the illumination source, but rather will be formed by the configuration of the illumination optics 504. The shape of the illuminated area may not be convex. As shown in the example of FIG. 5, the use of a standard refractive or reflective optical surface 506 in combination with the diffractive structure 508 requires the creation of a specific illumination spatial profile 510 having a planar phase-front from the imaging optics. Try to match the FOV optimally. Imaging optics 512 is configured to map the specific illumination profile 510 to the detector arrangement 502 in such a way that the light sensing elements are efficiently covered without covering excessively large areas outside the sensing areas. In other words, the optical system 500 of FIG. 5 is configured to properly match the reflected light in the form of the detector arrangement 502 so that the light dimmed outside the FOV of the detector is minimized. Advantageously, this uses the energy from the light source more efficiently.

The optics are preferably configured such that the illuminated portion of the surface is 50% or less larger than the FOV of the photosensitive elements of the detector. In other words, the reflected illumination is preferred to cover the area of the detector which is 150% or less of the minimum area to cover all the photosensitive elements of the detector. More preferably, the optics are configured such that the illuminated portions of substantially all (eg 85% or more) surfaces fall within the FOV of the photosensitive elements of the detector.

The particular example shown in FIG. 5 is shown that the illumination profile 510 may be a mirror image of reflected illumination covering the photodetector arrangement 502 in form. This depends on the configuration of the imaging optics 512.

According to a particular embodiment of the present invention, as shown in FIG. 6, the detector configuration may be used with a plurality of interlaced "pixels" (detector elements) arranged in parallel rows along two axes. have. More specifically, FIG. 6 shows three interlaced arrays 602 arranged in parallel rows along the x-axis, and three interlaced arrays 604 arranged in parallel rows along the y-axis. .

As described above with respect to FIG. 3, each “4N” array consists of four groups of N detector elements that are electrically connected (wired sum), so that four signals S _1. S ₂ S ₃ Generate S ₄ . Background suppression (and signal enhancement) is achieved using the differential signals S ₁₃ = S ₁ -S ₃ and S ₂₄ = S ₂ -S ₄ . The amount and direction of translation can be derived from orthogonal pairs, S ₁₃ and S ₂₄ .

In this particular embodiment, three " 4N " arrays 602, 604 are used for each axis x and y to suppress the accumulated phase error in displacement. In this particular embodiment, 24 lines (two axes, three arrays / axis, four signals / s) provided to the front-end electronics 606 that process the signals and provide inputs to the digital signal processor 608. Array). For example, the DSP 608 may have a USB universal serial bus interface (610).

Other embodiments may use interlaced detector arrays with M values different from four (ie, number of device groups). Other embodiments may also use other numbers than three, per axis. The number of rows need not be the same on the x and y axes.

Other embodiments may be configured with a detector array arrangement that is not in an "L" arrangement 702. Examples of other possible arrangements, such as the T arrangement 704, the rectangular arrangement 706, and the “+” or “X” arrangement 708 are shown in FIG. 7. Other embodiments may be configured in an arrangement with the axes (rows) at an angle other than vertical, such as, for example, an arrangement of the form "V" or "Δ".

The foregoing description of specific embodiments and examples of the present invention has been presented for purposes of illustration and description, and although the present invention has been described and described in the foregoing examples, it should not be construed as so limited. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and numerous modifications, improvements, and variations are possible within the scope of the invention through the foregoing description. The scope of the invention is intended to cover the general scope as disclosed herein by the claims appended hereto and their equivalents.

Claims (20)

An optical displacement sensor that determines the displacement of optical properties in successive frames to detect relative movement between the data input device and the surface, An illuminator having a light source and illumination optics for illuminating a portion of the surface by illumination light having a substantially planar phase-front; And A detector having a plurality of photosensitive elements and imaging optics, The illuminator and the detector are configured such that the illuminated portion of the surface is greater than or equal to 50% or less than a field of view (FOV) of the photosensitive elements of the detector. The optical displacement detector of claim 1, wherein the illumination optics include diffraction and refractive optics to minimize light that falls outside of the FOV of the detector. 10. The device of claim 1, wherein the plurality of photosensitive elements comprises a first plurality of photosensitive elements arranged substantially straight along a first axis, and a second plurality of photosensitive elements arranged substantially straight along a second axis. And wherein the second axis is non-parallel with the first axis. The optical displacement sensor of claim 3, wherein the second axis is at an angle of about 90 degrees with respect to the first axis. The method of claim 3, wherein the first and second plurality of photosensitive elements are arranged along the first axis and the second axis such that 'L', 'T', '+', 'X', 'V', ' Δ ', or optical displacement detector forming an array of square shapes. 6. The illuminator of claim 5, wherein the illuminator is further configured such that an illuminated portion of the surface defines a corresponding 'L', 'T', '+', 'X', 'Δ', or square shape on the surface. Constituting optical displacement detector. The optical displacement detector of claim 1, wherein the illuminator is further configured such that an illuminated portion of the surface corresponds in shape and area to the FOV of the photosensitive elements of the detector. The apparatus of claim 1, wherein the illuminator is further configured to provide a predetermined margin for errors in manufacturing and operation of optical displacement detector components such that the illuminated portion of the surface is sufficiently larger than the FOV of the detector. Wherein the illuminated portion of the surface is less than 50% greater than the FOV of the detector. The optical displacement sensor of claim 1, wherein the photosensitive elements comprise photodiodes and the light source comprises a laser. The optical displacement sensor of claim 1, wherein the optical displacement sensor is a speckle-based displacement detector adapted to identify a location on the surface based on a complex interference pattern generated by light reflected from the surface. And the laser comprises a vertical cavity surface emitting laser (VCSEL). The optical displacement detector of claim 1, wherein the illuminator and the detector are configured such that substantially all illuminated portions on the surface fall within the FOV of the photosensitive elements. A method of detecting relative movement between a data input device and a surface by determining displacement of optical features in successive frames, Generating illumination from a light source; Mapping the illumination to a portion of the surface by illumination optics such that the illumination light has a substantially planar phase-front; Reflecting illumination from the illuminated portion of the surface; And Mapping the reflected illumination to an array of photosensitive elements of the detector by imaging optics, The illuminated portion of the surface is greater than 50% less than the FOV of the photosensitive elements. 13. The method of claim 12, wherein mapping the illumination by the illumination optics includes refracting and diffracting the illumination such that an illuminated portion of the surface corresponds in shape to the FOV of photosensitive elements of the detector. . The method of claim 13, wherein the first plurality of photosensitive elements are arranged substantially straight along a first axis, and the second plurality of the photosensitive elements are arranged substantially linearly along a second axis, wherein the second axis is the first axis. Non-parallel to one axis. The photosensitive device of claim 14, wherein the photosensitive elements have a shape from a group of shapes consisting of 'L', 'T', '+', 'X', 'V', 'Δ', and a square shape. Arranged to form, wherein the illuminated portion of the surface forms a corresponding shape. 15. The method of claim 14, wherein mapping the illumination comprises: defining an 'L', 'T', '+', 'X', 'V', 'Δ', and rectangular shape on the surface. Illuminating a portion of the illuminated portion overlapping and corresponding in shape to the FOV of the detector. An optical displacement detector that determines the displacement of optical features in successive frames and detects relative movement between the data input device and the surface, Light source; Illumination optics adapted to illuminate a portion of the surface in a first form; An array of photosensitive elements comprising a second form similar to the first form; Imaging optics adapted to map illumination reflected from an illuminated portion of the surface such that the reflected illumination covers an array of photosensitive elements Optical displacement detector comprising a. 18. The optical displacement sensor of claim 17, wherein the first shape is non-circular and is not a direct image of the light source. 18. The optical displacement sensor of claim 17, wherein the first form is not convex. 18. The optical displacement sensor of claim 17, wherein the illuminated portion of the surface is greater than 50% greater than the FOV of the photosensitive elements.

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