JP2007198979A - Speckle capturing device, optical mouse, and speckle capturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for controlling and measuring a speckle image in displacement monitoring use. <P>SOLUTION: The present invention relates to the device and a method for capturing a speckle. A surface is irradiated with a high-coherent light emitted from a light source, to generate scattered lights. The scattered lights are transmitted through a light limiting element, diffracted lights generated by the light limiting element interfere each other to generate a speckle pattern. Then, an image sensor is used to pick up the speckle pattern and to form the speckle image. Resultingly, effects of the diffraction and the interference, and the light limiting element, are used in order to magnifying a speckle size under moving of an image formation device and to reduce fluctuation of the speckle pattern, and the speckle pattern is thereby identified clearly in the image. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an application of relative movement detection using a coherent light source, and an improvement in speckle pattern image formation configuration and technology.

  A laser is a light source having high coherence. When two high coherence lights are close to each other and the optical path difference (OPD) is less than the coherent length, these lights interfere with each other. There is constructive interference and destructive interference, where the former interference produces a bright fringe, while the latter interference produces a dark fringe. Thus, interference between two coherent light beams often produces a pattern of alternating light and dark fringes. Furthermore, this interference is related to the wavelength of the light. When the two beams overlap, destructive interference occurs when the phase difference is half the wavelength, but constructive interference occurs when the phase difference is an integral multiple of the wavelength. As a result, the detection accuracy is half the wavelength. Since the wavelength of the laser light is extremely short (for example, the wavelength of visible light is in the range of 0.3 to 0.7 μm), the half-wavelength accuracy is very sensitive. Thus, the interference effect has many uses.

  When highly coherent light is projected onto a rough surface, the light is strongly scattered in all directions. When two high coherence lights are close to each other and the OPD is less than the coherent length, interference occurs and many bright and dark spot patterns are formed. This is the cause of laser speckle.

  Speckle that is not related to the displacement of the light source is considered noise, which reduces the image quality. However, it has been discovered that speckle that correlates with the displacement of the light source can be used as a measurement means. Recently, speckle properties that correlate with the displacement of the light source have been used to detect relative movement of the navigator. For example, US 20050024623 (herein referred to as Patent 623) discloses an optical displacement method and device. The embodiment of Patent 623 uses a coherent light source to launch a coherent beam toward the surface, which is then reflected off the surface and leaves it. The sensor is placed in a specularly reflected light path, and the reflected beam received by the sensor includes a speckle pattern having a number of speckles within the speckle pattern. Correlation of successive narrow bandwidth scattering pattern images is typically used to determine relative movement displacement.

  Another related technology is the patent of PCT Patent No. WO2004075040 (herein referred to as Patent 040). This patent discloses an optical signal processing method and device for an optical mouse having a digital data processing function. The relative displacement vector between the mouse laser beam signal and the surface of the object generating the speckle is calculated by collecting the speckle moving signal. Devices used to implement this idea include in the mouse an opto-electric signal amplification rectification module, a direction determination count module, and a computer interface. The device further includes a laser source and an opto-electrical sensor, where the sensor is used to receive a speckle signal of the laser light reflected from the object surface. The optical-electrical sensor transmits the received optical-electrical signal to the amplification rectification module.

  The signal reading means described above calculates the moving direction and distance of the mouse based on the fluctuation of speckle brightness of the image captured by the sensor. The 040 patent has a simple structure. However, if the reflective surface is very smooth, the size of the speckle produced will be very small. Therefore, it is difficult to detect speckle brightness fluctuations. In that case, the resolution is greatly reduced, resulting in lower sensitivity.

  The 623 patent mainly uses a sensor to receive a reflected beam equal to specular reflection. Thus, the signal received by the sensor can be divided into a direct current (DC) portion and an alternating current (AC) portion. The DC portion indicates a uniform distribution of reflected light. Speckle brightness fluctuations belong to the AC section. If the speckle size is too small, the AC portion is difficult to extract and analyze.

  In summary, sensitivity is determined by speckle size. Small size speckles cannot be identified effectively. Therefore, a method for controlling the speckle size during movement of the displacement sensor and reducing the fluctuation of the speckle pattern is a key for improving the sensitivity.

  The present invention relates to an application of relative movement detection using a coherent light source, and an improvement in speckle pattern image formation configuration and technology. It is an object of the present invention to provide a device and method for controlling and measuring speckle images in displacement monitoring applications. When scattered light moving around the surface illuminated by the beam of the coherent light source is passed through a small light constraining aperture, a diffraction phenomenon occurs. Diffracted optical waves from adjacent lights that have passed through the aperture produce speckles that are larger than those that interfere with each other and do not pass through the small aperture. This size enlargement effect allows the detector array to more reliably record each speckle spot and more accurately determine pattern movement. The relative movement between the surface and the beam source-detector assembly can be calculated by comparing the speckle pattern position change from successive picture frames taken by the detector unit.

  In accordance with the present invention, it is important that the light scattered in the detector array is limited to a sufficiently small area from the illumination surface. A lens and one aperture, or a combination of apertures, serves its purpose by limiting the angle of incidence of the scattered light. Limiting the coherent light source beam passing through a suitable beam shaping unit to achieve a small illumination spot can further help achieve the same objective.

  To achieve the above object, the speckle imaging device disclosed by the present invention has a light source that emits highly coherent light onto a surface to generate scattered light. The scattered light passes through a small aperture light limiting element and is then diffracted by this aperture. The diffracted light interferes with each other to generate a speckle pattern. Finally, the sensor picks up the speckle pattern and forms a speckle image.

  Furthermore, the light contraction unit can be used to reduce the diameter of highly coherent light emitted by the light source. Alternatively, the light focusing means can be used to minimize the diameter of the beam incident on the object surface so as to increase the dynamic range that can be analyzed from the moving speckle pattern.

  Another embodiment of the speckle imaging method of the present invention emits highly coherent light onto the surface to generate scattered light. The scattered light passes through a small aperture light limiting element and then generates a diffractive effect. The diffracted light interferes with each other to generate a speckle pattern. Finally, the speckle pattern is recorded to form an image.

  After recording the speckle pattern currently generated to form the image, there is a step of comparing this image with the previous image already obtained during the movement of the image sensor, thereby allowing the sensor assembly to be Movement can be determined.

  After the step of emitting highly coherent light, the method further includes reducing the diameter of the highly coherent light.

  Alternatively, after the step of generating scattered light by projecting highly coherent light onto the surface, the method further comprises passing the scattered light through the aperture to limit the incident angle of the scattered light.

  Thus, good sensitivity requires that the speckle pattern image be clear and stable in order to detect movement of the sensor assembly relative to the object surface. Furthermore, the speckle itself needs to be sufficiently large in size and have a high contrast to the background in order to be easily identified. Furthermore, the speckle pattern variation during movement of the sensor assembly relative to the reference surface must be small enough for identification purposes. The present invention uses diffraction and interference effects to increase the speckle size and limit the incident angle of scattered light to reduce speckle image variation. Thus, the speckle image is clear and has little variation during movement of the sensor assembly relative to the reference surface for a certain distance. Thus, the devices and methods for capturing speckle patterns disclosed herein are stable and sensitive.

  That is, the first invention of the present application is a speckle image forming apparatus that restricts an incident angle of a scattered light and a light source that emits a high-coherent light beam so as to be projected on a surface and generate a plurality of scattered lights. A light limiting element that generates a plurality of diffracted lights such that a plurality of diffracted lights interfere with each other to generate a plurality of speckles, and an image sensor that receives the speckles and generates a first speckle image. A second speckle image is generated after the light limiting element and the image sensor are moved with respect to the surface, the direction and distance of this movement comparing the first speckle image with the second speckle image This is a speckle image forming apparatus determined by the operation.

  In the second invention of the present application, the light limiting element is a microlens formed in front of the image sensor so that a speckle image is formed by the image sensor and the scattered light generates diffracted light. A speckle image forming apparatus according to the first invention.

  The third invention of the present application is the speckle image forming apparatus according to the first invention of the present application, further comprising a light blocking plate around the microlens to block unnecessary scattered light.

  According to a fourth aspect of the present invention, the light limiting element includes an aperture and a lens, the lens is disposed in front of the aperture, and the incident angle of the scattered light is limited due to a spatial filter performed by the aperture, and When the scattered light passes through the aperture and is diffracted by the aperture, the diffracted light interferes with each other to generate speckle that forms an image on the image sensor. is there.

  In the fifth invention of the present application, the light limiting element includes an aperture and a lens. The aperture is disposed in front of the lens, and when the scattered light passes through the aperture and is diffracted by the aperture, the diffracted light interferes with each other. Then, the speckle image forming apparatus according to the first invention of the present application, which generates speckles for forming an image on the image sensor.

  The sixth invention of the present application further includes a second aperture arranged on the side of the aperture facing the surface, and the second aperture and the aperture limit the field of view of the image sensor. The speckle image forming apparatus described in 1.

  The seventh invention of the present application further includes a beam reduction unit that is a converging lens disposed in front of the light source for converging highly coherent light into a convergent beam. Speckle image formation according to the first invention of the present application Device.

  The eighth invention of the present application is the speckle image forming apparatus according to the first invention of the present application, further comprising a lens system disposed in front of the light source for converting highly coherent light into a parallel beam.

  The ninth invention of the present application is the speckle image forming apparatus according to the eighth invention of the present application, further comprising a beam reduction unit for reducing the diameter of the beam of highly coherent light emitted from the light source.

  The tenth invention of the present application is the ninth invention of the present application, wherein the beam reduction unit includes a first converging lens and a second converging lens that are in focus to reduce the beam diameter of the highly coherent light. Speckle image forming apparatus.

  According to an eleventh aspect of the present invention, the beam reduction unit includes a first lens and a third lens that are in focus, and the third lens is a diverging lens, whereby a beam of highly coherent light is obtained. The speckle image forming apparatus according to the ninth aspect of the present invention, wherein the diameter is reduced.

  The twelfth invention of the present application is an optical mouse, which generates a plurality of diffracted lights from a light source that emits a beam of highly coherent light that is projected on a surface and generates a plurality of scattered lights. A light limiting element that causes the diffracted light to interfere with each other to generate a plurality of speckles, and an image sensor that receives the diffracted light, wherein a first speckle image is generated before the movement of the image sensor, And an image sensor that generates a second speckle image after movement of the image sensor with respect to the surface, and receives the first speckle image and the second speckle image, compares them, and compares the light limiting element and the image An optical mouse comprising a processing unit for determining the direction and distance of displacement of a sensor.

  In the thirteenth invention of the present application, the light limiting element includes an aperture and a lens, and the lens is disposed in front of the aperture, whereby the incident angle of the scattered light is limited by the aperture, and the diffracted light is limited by the scattered light. The optical mouse according to the twelfth aspect of the present invention, wherein the diffracted light interferes with each other to generate a speckle image on the image sensor.

  The fourteenth invention of the present application is the optical mouse according to the twelfth invention of the present application, further comprising a beam reduction unit for reducing the diameter of the beam of highly coherent light emitted by the light source.

  The fifteenth aspect of the present invention is a speckle capturing method, the step of emitting a beam of highly coherent light, the step of projecting the highly coherent light onto the surface to generate a plurality of scattered light, and the scattered light. A speckle capturing method comprising: passing a light limiting element to generate a plurality of diffracted lights; and generating a plurality of speckles by causing the diffracted lights to interfere with each other and recording a speckle image. is there.

  In the sixteenth aspect of the present invention, the step of recording the speckle image is followed by the step of determining the speckle movement by comparing successive pattern images generated during the relative movement of the image sensor and the surface. The speckle capturing method according to the fifteenth aspect of the present invention.

  The seventeenth aspect of the present invention is the speckle capturing method according to the fifteenth aspect of the present invention, wherein the step of emitting a beam of highly coherent light is followed by a step of reducing the diameter of the highly coherent light.

  The eighteenth aspect of the present invention is the speckle capturing method according to the fifteenth aspect of the present invention, in which the step of emitting a beam of highly coherent light is followed by the step of reducing the incident angle of the scattered light and making the image incident. is there.

  According to a nineteenth aspect of the present invention, in the step of projecting highly coherent light onto the surface to generate a plurality of scattered light, the scattered light is passed through the second aperture, whereby the second aperture and the light limiting element. The speckle capturing method according to the fifteenth aspect of the present invention, wherein the combination is followed by a step of limiting the field of view of the image sensor.

  Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are provided for purposes of illustration only. This is because various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from this detailed description.

  The present invention will be more fully understood from the detailed description given below by way of example only, and thus is not intended to limit the invention.

  The system structure of the present invention is shown in FIG. 1A. When light is emitted to the surface 100, the properties of the reflected light are determined by the roughness of the surface 100. The smoother the surface 100, the more specular the surface 100 will be. In that case, the incident light 110 is almost totally reflected, and the reflected energy is substantially equal to the incident energy. The rougher the surface 100, the more dull the surface 100 becomes. After projecting onto the rough surface 100, the light is scattered in almost all directions. This is because the surface 100 is rough so that light propagates in any direction due to scattered light.

  After the incident light 110 is projected onto the surface 100, the lens 140 and the image sensor 150 are used to receive the scattered light 120. A light limiting element is placed in front of the image sensor 150 to enlarge the speckle. The light limiting element is a combination of the aperture 130 and the lens 140. The aperture 130 controls the size of the speckle and can be placed in front of the lens 140, as shown in FIG. 1A, or between the lens 140 and the image sensor 150, as shown in FIG. 1B. Can be placed. Furthermore, the position and diameter of the aperture 130 in FIG. 1B not only controls the size of the speckle, but also limits the incident angle of the scattered light 120. In this embodiment, the sensor is a two-dimensional array, such as a charge coupled device (CCD), complementary metal oxide semiconductor (CMOS), for capturing images.

  Alternatively, the aperture may be replaced by a microlens 131, which is arranged around the microlens 131 so that the light blocking plate 132 acts as a light limiting element, as shown in FIG. 1C. (Because the diameter of the microlens 131 is small, this lens provides the effect of the aperture 130). Scattered light passes through the microlens 131 and is diffracted by the microlens 131 that controls the size of the speckle. The microlens 131 functions as the lens 140 and forms an image on the image sensor 150. In the following paragraphs, we describe how the light limiting element enlarges the speckle size.

  FIG. 2 shows the diffraction pattern of the scattered light passing through the light limiting element. When highly coherent light 160, such as laser light, passes through a small diameter aperture 170, diffraction occurs. Thus, the light forms several concentric rings on the screen 190 due to diffraction. The central one represents the maximum and forms a bright spot 180 with a lateral width 2δ. The half width δ of the bright spot 180, the wavelength λ of the light wave, the diameter d of the aperture 170, and the distance Z between the aperture 170 and the screen 190 satisfy the following relationship.

  FIG. 3 shows that scattered light 120 was generated from different adjacent scattering centers on the illuminated surface. Each ray of scattered light 120 passes through a light limiting element. The light limiting element is implemented using a small diameter aperture 130, resulting in a diffractive effect of incident light. Accordingly, the different bright spots 180 interfere with each other, resulting in an interlaced distribution of bright and dark spots that form a speckle pattern. Diffraction theory predicts that larger speckle sizes will be created with smaller apertures. Therefore, it becomes easier to extract the movement of the speckle pattern using the image sensor.

  In the disclosed system structure, the scattered light passes through the light limiting element and is diffracted by the aperture, thereby making the speckle size larger than the minimum resolution element size of the image sensor array. Therefore, the sensor can accurately display the shape of the speckle and can determine the movement of the speckle pattern during the movement of the sensor relative to the object surface.

  Since the position of the speckle pattern of the image sensor 150 changes when the surface 100 moves, the speckle pattern is approximately before and after the surface 100 moves to tell the direction and amount of the position change of each speckle spot. Must be the same. However, the speckle pattern is formed by interference of scattered light 120 reflected from the non-uniform surface 100. Thus, the speckle pattern changes during relative movement of the image sensor 150 relative to the surface 100. However, the speckle pattern variation is continuous rather than discrete. If the speckle pattern variation is reduced during movement relative to the surface of the image sensor, when the speckle image sensor 150 moves relative to the surface 100, the speckle pattern has a strong correlation within a predetermined range of movement. Have Therefore, it is possible to determine the movement of the speckle pattern by comparing the speckle images of the sequential picture frames, and therefore the direction and distance of the displacement of the speckle capturing device can be determined.

  The light source emits highly coherent light. The most commonly seen highly coherent light is a laser. Thus, the light source can be a vertical cavity surface emitting laser (VECSEL), an edge emitting laser (EEL), or a light emitting diode (LED) capable of emitting highly coherent light with a narrow band filter.

FIG. 4 shows how the speckle moves in accordance with the present invention. When the aperture 130 is not moving, the scattered light 120 from the points A and B forms an image at the points A ′ and B ′ on the image sensor 150 via the point O of the aperture 130, respectively. As the aperture 130 moves a distance dl, the illuminated area also moves a distance dl, and then the scattered light 120 from points A and B passes through a point O ′ of the aperture 130 on the image sensor 150. Images are formed on A ″ and B ″. When the aperture 130 moves the distance dl, the region of the surface 100 irradiated by the light beam also moves the distance dl in the same direction. The point of the new irradiation area equivalent to the point A of the original irradiation area is called point A _eq . A point in the new irradiation area equivalent to the point B in the original irradiation area is called a point Beq. Point light scattered from A _eq and point B _eq forms respectively image points of each A _eq on the image sensor 150 "and point B _eq" via point O 'of the aperture 130. Since the image sensor 150 and the aperture 130 move together, the paths A to A ′ and Aeq to A _eq ″ are therefore geometrically equivalent to the image sensor 150. The points A and A _eq are the image The image should be formed at the same position on the sensor 150. In other words, for the image sensor 150, the points A ′ and A _eq ”enter the same pixel and the points B ′ and B _eq ″ are the same pixel. When the speckle image is observed from the image sensor 150 after the image sensor is moved, the feature image of the point A is moved from the original point A _eq ″ to the point A ″. Similarly, the feature image of B is also point B Moving from _eq "to point B". Therefore, by comparing speckle patterns, between point A _eq "and point A" and between point B _eq "and point B" The displacement relationship between them, thereby determining the direction and distance of displacement of the image sensor 150 relative to the surface 100. By moving from point _Aeq "to point A" and from point _Beq "to point B". The induced change represents a change in the position of the image in geometric optics. However, the change in the intensity of the laser speckle measured at point A "or B" is related to the optical path difference (OPD) caused by the variation in the reflected optical path. 5A and 5B, the optical path of point A after moving the image sensor (the optical path between A and A ″) and the equivalent optical path of point A before moving the image sensor (the optical path between Aeq and A ″ eq) ) and comparing, calculating the OPD _a is OPD between a-a "and Aeq-a _eq". moving distance dl of the aperture 130, OPD _a,及Incident angle [Phi _A defined owes angle between the scattered light 120 and the normal of the aperture from the point A satisfies the following relationship.

Accordingly, the incident angle Φ _B defined by the moving distance dl of the aperture 130, OPD _B , and the angle between the scattered light 120 from the point B and the normal of the aperture satisfies the following relationship.

If Φ _A is equal to Φ _B , OPD _A is equal to OPD _B. This means that the phase distribution of the speckle pattern before and after movement relative to the surface of the sensor assembly is unchanged, which means that the intensity distribution of the speckle pattern does not change before and after movement relative to the surface of the sensor assembly. is doing. If Φ _A and Φ _B are not equal to each other, OPD _A is not equal to OPD _B. When the difference between the two exceeds a critical value, the speckle pattern after movement largely deforms so as to be greatly different from the speckle pattern before movement. In that case, the speckle pattern obtained after the movement of the sensor cannot be recognized. Depending on the roughness of the surface 100, as speckles not much deformed, substantial differences between the OPD _A and OPD _B are acceptable. Experimental results show that the maximum allowable OPD for aluminum and copper plates is significantly greater than the maximum allowable OPD for plastic plates and smooth photographic paper. When different surfaces and coherent light sources are used, the maximum allowable OPD is different, but the maximum allowable OPD for the same surface 100 with the same coherent light source 200 is constant.

  Therefore, the change in OPD is related to the incident angle Φ of the scattered light 120 and the displacement of the aperture 130 combined with the image sensor 150. The incident angle Φ is related to the radius r of the illuminated region and the distance Z ′ between the aperture 130 and the surface 100.

  If the incident angle Φ is very small,

  It becomes. Furthermore, if the maximum allowable OPD is constant and the distance Z ′ between the aperture 130 and the surface 100 is held constant, the need to reduce the incident angle Φ is that r must be reduced. means. This indicates that the illuminated area must be reduced. In this case, within a certain range of movement, the shape of the speckle pattern can be maintained and remains recognizable. That is, when the speckle imaging device is moved within a predetermined limited range relative to the surface, the speckle shape does not change or only slightly changes, and the shape remains recognizable. Since the speckle image forming device is displaced, a new speckle pattern image is thus formed at another position of the image sensor after the sensor assembly is moved. Thus, the direction and distance of movement of the speckle imaging device can be determined by recording successive images of the speckle pattern during movement and subsequently comparing these images continuously. .

  In order to achieve such a situation, the diameter of the incident beam must be reduced. Referring to FIGS. 6A, 6B, and 6C, an embodiment of the present invention places a beam reduction unit 210 near the light source and reduces the diameter of the incident beam as it is projected onto the surface 100. To work. In one embodiment, as shown in FIG. 6A, a converging lens 211 is disposed in front of the light source 200, and when the light emitted from the light source 200 passes through the converging lens 211, the light is converged. . Therefore, when the surface 100 is close to the focal point of this convergent beam, the illuminated area is small. Alternatively, if the converging lens 211 is placed in front of the light source 200 to convert highly coherent light into a parallel beam, the first converging lens 212 combined with the second converging lens 213 is placed in focus. I can do it. The focal lengths of the first lens 212 and the second lens 213 are f1 and f2, respectively. As shown in FIG. 6B, when f <f1, the diameter of the incident beam is

  Only reduced. Yet another solution uses a first lens 212 and a third lens 214 to form a beam reduction unit 210 having a third lens 214 that is a diverging lens. When the focal points of the first lens 212 and the third lens 214 coincide, when the incident beam passes through the two-lens system constituted by the lenses 212 and 214, the beam contracts. In this scheme, the distance between the first lens 212 and the third lens 214 is smaller. This helps to reduce the overall size of the system, as shown in FIG. 6C.

  Referring to FIG. 7A, in addition to manipulating the beam near the light source 200, manipulating the scattered light 120 can be performed. More specifically, the second aperture 215 is positioned before the scattered light 120 enters the lens 140 and the aperture 130. This second aperture 215 initially blocks a portion of the scattered light 120 and allows only a predetermined portion of the scattered light 120 to pass. In this way, the field of view of the image sensor is reduced by the second aperture 215.

  Referring to FIG. 7B, two object points E and F on the surface 100 are selected as reference points. Scattered light from points E and F should pass through aperture 130 and lens 140 and eventually focus on points E 'and F' on image sensor 150, respectively. By using ray tracing, it is recognized that the scattered light from points E and F is focused on the image sensor 150 when the aperture 130 is in position G. When the aperture 130 is at the position H, only the scattered light from the point F is focused on the image sensor 150. Thus, by appropriately adjusting the diameter and position of the aperture 130, the speckle size can be enlarged and the incident angle of the scattered light 120 can be limited.

  The disclosed device and method for capturing speckle can be applied to an optical mouse 300 as shown in FIG. Both the light source 200 and the image sensor 150 are disposed in the case 310 of the optical mouse 300. The beam emitted from the light source 200 is converged by the converging lens 211 and projected onto the surface 100, from which the scattered light 120 passes through the lens 140 and the subsequent small aperture 130 and is finally imaged on the image sensor 150. Formed and then transmitted to the processing unit 320. The first speckle image is recorded by the image sensor 150 before the case 310 moves, and then the second speckle image is recorded by the processing unit 320 after the case 310 moves relative to the surface 100. Is done. The processing unit 320 determines the correlation between the first and second speckle images and the magnitude and direction of displacement relative to the surface 100 of the case 310 with respect to the movement of the computer cursor.

  Referring to FIG. 9A, the speckle pattern image forming method starts by emitting a beam of highly coherent light (step 500). After the diameter of this highly coherent light is reduced (step 510), the light is projected onto the surface to produce scattered light (step 520).

  The scattered light passes through the light limiting element to generate diffracted light (step 530). As a result, the diffracted light interferes to generate a speckle pattern (step 540). An image of a speckle pattern is recorded (step 550). Next, movement of the sensor relative to the surface is determined by comparing the images of the speckle pattern (step 560).

  Referring to FIG. 9B, another embodiment begins with emitting a beam of highly coherent light (step 500). Next, highly coherent light is projected onto the surface to generate scattered light (step 511). The scattered light passes through the second aperture (step 521). Furthermore, the scattered light passes through the second aperture, the viewing angle of the image sensor is limited by this second aperture, and this second aperture also acts as a light limiting element. As the scattered light passes through the light limiting element, diffracted light is generated (step 530). The diffracted lights interfere with each other to generate a speckle pattern (step 540). An image of the speckle pattern is recorded during continuous movement of the sensor housing relative to the object surface (step 550). This relative movement is then determined by comparing successive images of the speckle pattern (step 560).

  Referring to FIG. 9C, the speckle imaging method begins by emitting a beam of highly coherent light (step 500). Highly coherent light is projected onto the surface to generate scattered light (step 511). The light limiting element includes an aperture and a lens, the lens is placed in front of the aperture, and the light limiting element is used to limit the incident angle of the scattered light (step 522). A large number of diffracted light waves are generated by passing the scattered light through the light limiting element (step 531). The diffracted lights interfere with each other to generate a speckle pattern (step 540). An image of the speckle pattern is recorded during continuous movement of the sensor housing relative to the object surface (step 550). The movement relative to the surface is then determined by comparing successive images of the speckle pattern (step 560).

  In summary, the present invention provides a method and device for capturing speckle. By placing the light limiting element in front of the image sensor, the speckle is magnified and the speckle pattern variation is reduced for the convenience of measuring the relative movement of the speckle pattern. Therefore, it is very easy to determine the relative movement of the speckle pattern. The present invention is applied to an optical mouse, and the movement of the mouse can be detected with high accuracy and high sensitivity. Furthermore, the disclosed methods and devices for capturing speckle can be applied to many types of surfaces.

  Although the present invention has been described in connection with specific embodiments, it will be apparent to those skilled in the art that many alternatives, modifications, and variations will be apparent in light of the foregoing. Accordingly, the present invention is intended to embrace all other such alternatives, modifications and variations that fall within the spirit and scope of the appended claims.

1 shows a system structure of the present invention. 1 shows a system structure of the present invention. 1 shows a system structure of the present invention. FIG. 3 is a schematic view of a diffraction phenomenon generated by the light limiting element of the present invention. 1 is a schematic view of speckle formed by the present invention. Fig. 4 shows speckle movement according to the present invention. It is the schematic which shows an optical path difference (OPD) in this invention. It is the schematic which shows an optical path difference (OPD) in this invention. It is the schematic of the light reduction unit in other embodiment of this invention. It is the schematic of the light reduction unit in other embodiment of this invention. It is the schematic of the light reduction unit in other embodiment of this invention. FIG. 6 is a schematic view of adding a second aperture to the present invention. It is the schematic which shows that the incident angle of the scattered light which injects into a sensor is restrict | limited by the restraint aperture of this invention. It is the schematic which shows the use of this invention. It is a flowchart of the speckle capture method. It is a flowchart of the speckle capture method. It is a flowchart of the speckle capture method.

Claims (19)

A speckle image forming apparatus,
A light source that emits a beam of highly coherent light that is projected onto the surface and generates a plurality of scattered light;
A light limiting element that limits the incident angle of the scattered light and generates a plurality of diffracted lights such that the plurality of diffracted lights interfere with each other to generate a plurality of speckles;
An image sensor that receives the speckle and generates a first speckle image,
After the light limiting element and the image sensor are moved with respect to the surface, a second speckle image is generated and the direction and distance of this movement is to compare the first speckle image with the second speckle image. Speckle image forming apparatus determined by   The speckle image forming apparatus according to claim 1, wherein the light limiting element is a microlens arranged in front of the image sensor so that an image of the speckle is formed by the image sensor and the scattered light generates diffracted light. .   The speckle image forming apparatus according to claim 1, further comprising a light blocking plate around the microlens to block unnecessary scattered light.   The light limiting element includes an aperture and a lens, and the lens is disposed in front of the aperture, and due to a spatial filter performed by the aperture, the incident angle of the scattered light is limited, and the scattered light passes through the aperture and the aperture. The speckle image forming apparatus according to claim 1, wherein when diffracted by the diffracted light, the diffracted light interferes with each other to generate a speckle that forms an image on the image sensor.   The light limiting element includes an aperture and a lens that is placed in front of the lens, and when scattered light passes through the aperture and is diffracted by the aperture, the diffracted light interferes with each other to form an image on the image sensor. The speckle image forming apparatus according to claim 1, wherein the speckle image forming apparatus generates a speckle to be processed.   The speckle image forming apparatus according to claim 5, further comprising a second aperture disposed on a side of the aperture facing the surface, wherein the second aperture and the aperture limit a field of view of the image sensor.   The speckle image forming apparatus according to claim 1, further comprising a beam reduction unit that is a converging lens disposed in front of the light source for converging highly coherent light into a converging beam.   The speckle image forming apparatus according to claim 1, further comprising a lens system disposed in front of the light source for converting the highly coherent light into a parallel beam.   The speckle image forming apparatus according to claim 8, further comprising a beam reduction unit for reducing the diameter of the beam of highly coherent light emitted by the light source.   The speckle image forming apparatus according to claim 9, wherein the beam reducing unit includes a first converging lens and a second converging lens that are in focus to reduce the beam diameter of the highly coherent light.   The beam reduction unit includes a first lens and a third lens that are in focus, wherein the third lens is a diverging lens, whereby the beam of highly coherent light is reduced in diameter. Item 12. The speckle image forming apparatus according to Item 9. An optical mouse,
A light source that emits a beam of highly coherent light that is projected onto the surface and generates a plurality of scattered light;
A light limiting element that generates a plurality of diffracted light from the scattered light, whereby the diffracted light interferes with each other to generate a plurality of speckles;
An image sensor for receiving diffracted light, wherein the image sensor generates a first speckle image before movement of the image sensor and generates a second speckle image after movement of the image sensor with respect to the surface; ,
An optical mouse comprising: a processing unit that receives a first speckle image and a second speckle image and compares them to determine the direction and distance of the light limiting element and the displacement of the image sensor.   The light limiting element includes an aperture and a lens, the lens is placed in front of the aperture, whereby the incident angle of the scattered light is limited by the aperture, diffracted light is generated by the scattered light, and the diffracted light interferes with each other The optical mouse according to claim 12, wherein a speckle image is generated on the image sensor.   The optical mouse of claim 12, further comprising a beam reduction unit to reduce the diameter of the beam of highly coherent light emitted by the light source. Speckle capture method,
Firing a beam of highly coherent light;
Projecting highly coherent light onto the surface to generate a plurality of scattered light;
Passing scattered light through a light limiting element to generate a plurality of diffracted lights;
A step of generating a plurality of speckles by causing the diffracted light to interfere with each other and recording an image of the speckles.   16. The speckle of claim 15, wherein the step of recording an image of the speckle is followed by a step of determining the movement of the speckle by comparing successive pattern images generated during the relative movement of the image sensor and the surface. Capture method.   16. The speckle capture method according to claim 15, wherein the step of emitting a beam of highly coherent light is followed by a step of reducing the diameter of the highly coherent light.   The speckle capturing method according to claim 15, wherein the step of emitting a beam of highly coherent light is followed by the step of reducing the incident angle of the scattered light and entering the image. The step of projecting highly coherent light onto the surface to generate a plurality of scattered light is to pass the scattered light through a second aperture, whereby the combination of the second aperture and the light limiting element limits the field of view of the image sensor. The speckle capturing method according to claim 15, further comprising:

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