LASER POINTER

A laser pointer for continuously drawing arbitrary shapes on a surface comprises a micro-electro-mechanical system (MEMS) mirror configured to deflect an emitted laser beam, wherein the deflection angle of the MEMS mirror can be altered by means of applying a set of drive values to the MEMS mirror; an orientation measurement unit configured to continuously determine a current orientation and to output said current orientation at an output; a memory being configured to store current orientations received from the orientation measurement unit as a set of orientation samples; and a drive circuit configured to generate said set of drive values by subtracting the current orientation from the set of orientation samples and to apply said set of drive values to the MEMS mirror.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to European Patent Application Serial No. 18154213.5, filed on Jan. 30, 2018, which is herein incorporated by reference in its entirety.

FIELD OF INVENTION

The present subject matter relates to a laser pointer for drawing arbitrary shapes on a surface, e.g., a wall, board, or the like.

BACKGROUND OF THE INVENTION

During the last three decades, laser pointers became a necessity for presentations in business meetings, school events, and even public speeches. Laser pointers make it easy to highlight areas on presentation material that is usually hard to reach for the presenter by projecting a light spot in various colors—ranging from blue to green and red. These little light generators help to temporarily mark an area on a slide or poster, for which the presenter only has to move the projected light spot to an area of interest.

However, many presenters often find themselves in a pickle when they want to highlight an entire word because underlining a many characters is only possible by frantically waving your laser pointer, causing distraction to the audience and frustration for the presenter. Furthermore, adding words or drawings to slides or posters is not possible at all, and presenters have to resort to ancient technologies such as markers, highlighters or even adding paper scraps with adhesive tape to the presentation material on the wall.

In other areas, laser pointers have made technological advances. For example, US 2007/0023527 A1 describes a laser pointer that reduces hand tremors of a nervous presenter by counteracting the laser pointer's movement on a low scale. To this end, this laser pointer is equipped with an orientation sensor and a mirror system to invert the movement of the laser pointer, resulting in a more or less static laser spot on the wall. Additionally, this laser pointer can project predetermined shapes such as lines or circles by linearly driving the MEMS (micro-electro-mechanical systems) mirror.

Unfortunately, these predetermined shapes do not allow the presenter to express his or her thoughts or artistic freedom as he or she is restricted to lines and circles. While it would be straightforward to pre-program this laser pointer for additional shapes such as rectangles or even star shapes, the presenter would still be severely restricted to the options of the laser pointer.

SUMMARY

It is therefore an object of the disclosed subject matter to provide an improved laser pointer that overcomes the problems of the state of the art.

To this end, the disclosed subject matter provides a laser pointer of the aforementioned type, comprising:

a laser generation unit configured to emit a laser beam;

a micro-electro-mechanical system (MEMS) mirror configured to deflect the emitted laser beam, wherein the deflection angle of the MEMS mirror can be altered by means of applying a set of drive values to an input of the MEMS mirror;

an orientation measurement unit configured to continuously determine a current orientation of the laser pointer and to output said current orientation at an output;

a memory having an input that is connected to the output of the orientation measurement unit, the memory being configured to store current orientations received from the orientation measurement unit as a set of orientation samples;

a drive circuit having a first input connected to the memory for retrieving said set of orientation samples from the memory and a second input connected to the output of the orientation measurement unit for receiving the current orientation from the orientation measurement unit;

wherein the drive circuit is configured to generate said set of drive values by subtracting the current orientation from the set of orientation samples and to apply said set of drive values to the input of the MEMS mirror; and

wherein the memory is configured to continuously store new orientation samples while the MEMS mirror is driven by the drive circuit, and the drive circuit is configured to update the set of drive values when a new orientation sample is stored in the memory.

Such a laser pointer provides an exhilarating experience for presenters as they now can draw and even write on their presentation material in real-time. By a simple wave of the hand, it is possible to project an arbitrarily curved line of light on a surface, e.g., a wall, board, or the like. This allows presenters to modify slides and write-ups in front of a live audience and also to delete the drawn shapes at will.

By using MEMS mirrors, previously marked areas on the wall, board, or the like can be “re-visited” by the light spot without the need for the presenter to actually move his or her hand. The drawn shape is memorized within the laser pointer and played back with the MEMS mirror, even during the process of drawing. This gives the presenter a completely new and previously unheard-of feeling of using his/her presentation material as he/she can develop the content of the slides on the fly.

To draw shapes that are bright on the wall and do not flicker, the same drive values may be applied multiple times to the MEMS mirror such that the MEMS mirror “re-draws” the same shape multiple times. If this is done in quick succession, the human eye cannot distinguish between the individual cycles of the MEMS mirror and a static shape is experienced. For this purpose, the drive circuit is optionally configured to repeatedly apply the set of drive values to the MEMS mirror.

To ensure that the MEMS mirror is capable of displaying all of the generated drive values, although this may not be necessary if some drive values can be disregarded, in a further embodiment the rate of applying the individual drive values of the set of drive values to the MEMS mirror is at least N times higher than the rate of storing the individual orientation samples in the memory, wherein N corresponds to the number of orientation samples stored in the memory.

A challenge in practically realizing the laser pointer of the aforementioned type may be the usage of power. The longer and larger the drawn shape becomes, the less bright it will be on the wall as the MEMS mirror takes a longer time to reproduce the shape. Thereby, also the amount of MEMS mirror cycles per time unit is reduced, resulting in a dim output of the laser pointer. To overcome this, the disclosed subject matter provides several variants.

Firstly, the memory can be configured to delete an orientation sample from the memory after a predetermined time. By this means, the drawing “vanishes” after some time, making it temporary and freeing up memory space.

Secondly, the memory can be configured to delete the oldest orientation sample if a new orientation sample is stored. In this variant, the memory can have a maximum amount of storage such that also the amount of drive values to be generated is restricted. This is especially favorable if the presenter scribbles on the wall, board, or the like, as the laser pointer cannot suffer from an information overload, which would be near-impossible to reproduce with the MEMS mirror.

To further enhance the consistency of the intensity of the output and thus the quality of the drawn shape, the drive circuit optionally has a further output connected to a control input of the laser generation unit and is further configured to control an intensity of the emitted laser beam via said control input. Thereby, the drive circuit can adjust the intensity of the emitted laser beam to be proportional to the amount of drive values generated, i.e., increase the intensity if the drawn line becomes longer. For this purpose, the intensity of the laser pointer can be reduced in the beginning, e.g., to a value of 5%, 10%, 25%, or 50% of its maximum output capability.

This embodiment can also be used to provide “gaps” in the drawn shape, for example to provide a spacing when letters are written. The drive circuit can then specify that the intensity of the emitted laser beam is zero between specified drive values.

Sometimes it is also necessary for the presenter temporarily pause the drawing mode to focus on other parts of his or her presentation or to simply use the ordinary mode of projecting a single spot. Thus the laser pointer may optionally have an input device via which the storing of current orientations in the memory can be switched on and off.

The orientation sensor allows the laser pointer to record the changes in orientation, i.e., angular position, which are caused by the presenter tilting his or her hand holding the laser pointer. This embodiment is sufficient in most cases, as most of the movement of the laser pointer is caused by tilting the hand.

On the other hand, some presenters enjoy running from side to side with the laser pointer in front of the wall, board or the like. This causes also the written or drawn shape on the presentation material to move along with the presenter. In a further embodiment, the laser pointer may thus compensate its translatory movement. To this end, the orientation measurement unit is further configured to continuously determine a current position of the laser pointer, wherein the memory is further configured to store current positions received from the orientation measurement unit together with the current orientations as a set of orientation samples with position samples, and wherein the drive circuit is configured to generate said set of drive values based on the current orientation, the current position, and the set of orientation samples with position samples.

In most cases, the presenter is located at a constant distance in front of the wall, board, or the like, even if he or she moves from side to side. If the presenter also moves to and from his/her presentation material, this can cause a scaling problem for the projected shape. To overcome this scaling problem, which also affects to a lesser degree the aforementioned compensation of the translatory movement, the laser pointer optionally comprises a distance measurement unit configured to determine a current distance of the laser pointer from the surface, and to output said current distance at an output connected to an input of the memory and to an input of the drive circuit, wherein the memory is further configured to store current distances received from the distance measurement unit together with the current orientations and current positions as a set of orientation samples with position samples and distance samples, and wherein the drive circuit is configured to generate said set of drive values based on the current orientation, the current position, the current distance, and the set of orientation samples with position samples and distance samples.

Optionally, the laser pointer further comprises a sampler interposed between the orientation measurement unit and the memory, wherein the sampler is configured to output orientation samples at a constant rate to the memory for storing. This can be used to store current orientations at regular intervals and/or only when the change of current orientations exceeds a predetermined threshold, effectively reducing required memory size and the computational steps the drive circuit has to perform.

Further optionally, the laser pointer comprises a low-pass filter interposed between the orientation measurement unit and the memory. This serves to remove hand-tremor jitters from the drawn shape such that, e.g., lines can be drawn straighter. Optionally, such a low-pass filter may only be interposed between the orientation measurement unit and the memory and not between the orientation measurement unit and the drive circuit because the drive circuit needs the deviations even of small hand movements to compensate for hand tremors, such that the drawn shape can be hold still on the wall.

Further optionally, the laser pointer has at least two laser generation units, each configured for emitting a laser beam of a different wavelength onto said MEMS mirror. The user can thus chose the color of projecting the light, for example by means of a manual switch.

In this embodiment the drive circuit may optionally be configured to control the intensity of the laser beams emitted by the at least two laser generation units and to use each of the laser generation units for different subsets of the set of orientation samples. By means of this, the drive circuit can assign a certain color to a selected memory subset and a different color to a different—or overlapping, to mix colors—subset. For example, if the laser pointer is used for writing, one letter can be written in red and a different letter can be written in green.

Further optionally, the laser pointer has at least two MEMS mirrors, each configured for deflecting at least a part of said laser beam, wherein the drive circuit is configured to generate said set of drive values for each of the MEMS mirrors. This can be done either by means of arranging two MEMS mirrors in a serial manner or—for example with the use of a beam splitter—in a parallel manner. This can be used to overcome the limits in deflection angle of MEMS mirrors, which is typically max. 60°-120° when optically extending the optical scan angle. If two MEMS mirrors are used in parallel, one mirror could be used to project shapes on the far left and the other to project shapes on the far right; if two MEMS mirrors are used serially, the second one multiplies the deflection angle of the first.

DETAILED DESCRIPTION

FIG. 1ashows a laser pointer1in a first position2emitting a laser beam3onto a wall4. Instead of a wall4, the laser pointer1could also emit the laser beam3onto any kind of surface, such as a board, projection screen, poster, a slide projected by an external projector, or the like.

The laser pointer1is used to draw an arbitrary shape5, in the case ofFIG. 1aa curved line, onto the wall4by tilting the laser pointer1from a first orientation θ0in the first position2to a second orientation θiin a second position6with a tilting movement7, e.g., by tilting the hand holding the laser pointer1. In the second position6, a state-of-the-art laser pointer would naturally only emit one laser beam8to project one spot onto the wall4. The laser pointer1, however, is capable of deflecting the laser beam8along a movement that corresponds to the tilting movement7previously performed by the laser pointer1to “re-draw” the shape5onto the wall in the second position6. This is done by emitting a fan of laser beams8in such a manner that not only the present orientation θibut all previous orientations θi-1, θi-2, . . . , θ0that were assumed by the laser pointer1between the first position2and the second position6are included in the fan of laser beams8.

FIG. 1bshows that the laser pointer1moved even further from the first position2over the second position6to a third exemplary position9with a tilting movement10of the user's hand. Also inFIG. 1b,the laser pointer1emits a fan of laser beams12in such a manner that not only the present orientation θibut all previous orientations θi-1, θi-2, . . . , θ0that were assumed by the laser pointer1between the first position2, the second position6, and the third position9are included in the fan of laser beams12.

It can be seen fromFIG. 1bthat while in the second position6the laser pointer1already re-drew the beginning of the shape5, the complete shape5is now re-drawn in the third position9. This allows the user to draw any arbitrary shape5in real-time, just like with pen on paper usage. It is not necessary for a user to first define the shape5to be projected by the tilting movement10and only then start the composed projection, as this would make drawing more complex shapes such as letters and/or drawing shapes precisely at certain target positions on a wall very hard.

FIG. 2shows the components of the laser pointer1that allow the real-time drawing of shapes5as described above with reference toFIGS. 1aand1b.The laser pointer1comprises a laser generation unit13that emits the laser beam3,8,12. The laser generation unit13can be of any type known in the state of the art, for example a laser diode, a diode-pumped solid-state frequency-doubled laser, a light-emitting diode, or a superluminescent light-emitting diode. The laser beam3,8,12can be of any wavelength to produce any desired color.

The laser beam3,8,12is emitted onto a MEMS (micro-electro-mechanical system) mirror14comprising a motor component15and a mirror component16. The motor component15and the mirror component16are commonly embodied in a single element as known in the state of the art.

The deflection angle Φ of the MEMS mirror14can be electromechanically altered by applying a set of drive values DV to an input17of the MEMS mirror14. By altering the deflection angle γ, the laser beam3,8,12can be dynamically deflected to produce the fan of laser beams8,12shown inFIGS. 1aand1b.Generally, the MEMS mirror can be rotated about two axes to allow a deflection of the laser beam3,8,12on a two-dimensional area, i.e., the deflection angle Φ is an angle in space.

To determine the current orientation θiof the laser pointer1, an orientation measurement unit18is used. The orientation measurement unit18is fixated in a casing11of the laser pointer1which houses the components shown inFIG. 2. The orientation measurement unit18is capable of determining angular movements of the laser pointer1and can for this purpose be an IMU (inertial measurement unit), one or more gyroscopes, one or more magnetometers, a camera viewing and processing the environment of the laser pointer1, or the like.

The orientation measurement unit18can determine the current orientation θiof the laser pointer1in an absolute or relative manner. For an absolute determination of the orientation θiin space, for example a set of two angles α, β around reference axes can be used, seeFIG. 1a.To determine a relative orientation θi, it is only necessary to define a reference orientation, for example the orientation θ0in the first position2(FIG. 1a), and determine all following orientations θiwith respect to this reference orientation θ0.

To record the laser pointer's movement7,10from one position to the next, a sequence of current orientations θiis stored in a memory19. To this end, an output20of the orientation measurement unit18is connected to an input21of the memory19. The memory19can be of any type known in the state of the art, for example embodied as a digital database on a data storage, as a shift register, or as a circular buffer.

The memory19stores the current orientations θioutput by the orientation measurement unit18as a set S of orientation samples22. While the current orientations θican be output in any form, either as discrete values output at regular or irregular times or even as an analog signal, the set S of orientation samples22is a set of discrete values. In the simplest case a sequence of past discrete current orientations θiis the same as the set S of orientation samples22.

In the embodiment ofFIG. 2, an optional sampler23is interposed between the orientation measurement unit18and the memory19to transform the current orientations θiinto the set S of orientation samples22. The sampler23outputs the orientation samples22at a constant rate to the memory19for storing such that the memory19has no further need of processing the current orientations θi.

Depending on the method to generate the set S of orientation samples22, the orientation samples22can either have a fixed span of time between their respective times of recording, e.g., each orientation sample22is recorded 1 ms after the preceding orientation sample22, or the orientation samples22can have a fixed angular difference with respect to each other, e.g., each orientation sample22is recorded 0.01° after the preceding orientation sample22. Other criteria are possible, too.

Furthermore, a low-pass filter24can optionally be interposed between the orientation measurement unit18and the memory19. The low-pass filter24can be used to eliminate jitter from recorded lines such that only straight lines or smooth movements are recorded.

To generate the drive values DV for driving the MEMS mirror14, a drive circuit25is used. The drive circuit25has a first and a second input26,27. Via the first input26, the drive circuit25is capable of retrieving the con-tents of the memory19. Depending on the type of memory19used, the drive circuit25can either read out the whole set S of orientation samples22at once, for example by a data transfer of a digital list, or sequentially retrieve the orientation samples22(θi, θi-1, θi-2, . . . ) until the last orientation sample θ0is reached, whereupon the drive circuit25re-starts the step of retrieving at the first orientation sample θias is indicated by arrow28. Via the second input27the drive circuit15receives, directly from the orientation measurement unit18, the current orientation θi.

For generating the drive values DV, the drive circuit25comprises a subtractor29, which generates a set of drive values DV by subtracting the current orientation θifrom each orientation sample22retrieved from the memory19. It is to be understood that the term “subtractor” is only used for purposes of visualization as the subtractor29can assume a lot of other functions such as converting the result of the subtraction into a corresponding voltage for driving the MEMS mirror, applying scaling functions, or the like. Once the set of drive values DV is generated, it is applied—as a sequence of individual drive values DV each corresponding to one orientation sample22minus the current orientation θi—to the input17of the MEMS mirror14via an output30of the drive circuit25.

It is further to be understood that all the aforementioned steps of determining and storing current orientations θi, emitting the laser beam3,8,12, and driving the MEMS mirror15are performed simultaneously to allow a real-time drawing of the shape5on the wall4as shown inFIGS. 1aand1b.For this reason it is especially provided that the memory19is configured to continuously store new orientation samples22while the MEMS mirror14is driven by the drive circuit25, and the drive circuit25updates the set of drive values DV at least when a new orientation sample22is stored in the memory19.

The drive circuit25can comprise additional functions such as a pattern recognition algorithm that can determine if the user wants to draw a circle or a line. In this case, the drive values DV are manipulated such that instead of a crooked circle or a wiggly line a perfectly round circle or a straight line is output. The same can be utilized for letters, which is especially advantageous as writing with a laser pointer can be challenging for a presenter. To this end, even different typesets could be chosen such that the user's handwriting can be displayed in “Courier” or “Arial” typeset, for example.

Furthermore, the drive circuit25can “re-arrange” the drive values DV within the set of drive values DV to determine the fastest way for the MEMS mirror14to reproduce the contents of the memory19, i.e., the MEMS mirror14does not have to reproduce the movement7,10in a chronological manner but alternatively can do this in a more efficient way. This is especially useful if the movement7,10contains multiple disconnected shapes such as letters.

When the drive circuit25outputs the set of drive values DV to the MEMS mirror14, it does so repeatedly such that the MEMS mirror14projects the fan of laser beams8,12multiple times. For example, the same set of drive values DV can be repeatedly output to the MEMS mirror14as long as the content of the memory19or the current orientation θidoes not change.

Furthermore, the computation of the subtraction by means of the subtractor29can be performed continuously even with changing current orientations θi. For example, from a first part of the set S of orientation samples22a current orientation θiis subtracted and from a second part of the set S of orientation samples22a different current orientation θiis subtracted if a change in current orientation θioccurred in the middle of retrieving the set S.

In most embodiments, the rate of applying the individual drive values DV of the set of drive values DV to the MEMS mirror14is at least N times higher than the rate of storing the individual orientation samples22of the set S in the memory19, wherein N corresponds to the number of orientation samples22stored in the memory19, i.e., the size of the set S.

It can be seen that a cycle of outputting a set of drive values DV by the MEMS mirror14takes longer if there are a lot of drive values DV in the set of drive values DV. As such, the rate of outputting sets of drive values DV decreases if long shapes5are drawn. Thereby, also the intensity of the shape5as displayed on the wall4reduces. As a practical example, while a short shape5can be repeated 1000 times per second, a large shape5with 10 times the length of the short shape5can only be repeated 100 times per second, meaning also the intensity is 10 times lower for the long shape5. Various measures can be taken to solve this issue.

Firstly, the memory19can delete each orientation sample22from the memory19after a predetermined time, for example after 10 seconds. This reduces the amount of orientation samples22in the memory19and thus also the amount of drive values DV in the set of drive values DV.

Secondly, the memory19can delete the oldest orientation sample22from the memory19if a new orientation sample22is stored. The set S of orientation samples22can thus be restricted to a predefined size, for example N=1000 orientation samples22. If the 1001-st orientation sample22is to be stored, the oldest of the 1000 previously stored orientation samples22is deleted. This also limits the amount of orientation samples22in the memory19and thus the amount of drive values DV in the set of drive values DV.

In addition to these two measures, the drive circuit25can have a further output31connected to a control input32of the laser generation unit13and via this connection control the intensity P of the emitted laser beam3,8,12. For example, the drive circuit25can control the intensity P of the emitted laser beam3,8,12such that the intensity P of the emitted laser beam3,8,12is proportional to the number of drive values DV in said set of drive values DV. In this way, the drive circuit25can reduce the intensity P of the laser beams3,8,12emitted by the laser generation unit13when driving the MEMS mirror14for short shapes5and only use the full intensity P for the laser beams3,8,12when driving the MEMS mirror14for long shapes5.

To allow the user to draw a multitude of independent shapes5, the laser pointer1has an input device33via which the storing of current orientations θiin the memory19can be switched on and off. The input device can for this purpose be a simple button or a touchpad.

FIG. 3shows a variant of the laser pointer ofFIG. 2, in which the orientation measurement unit18can additionally continuously determine a translatory shift, i.e., a current position pi. For this purpose, common IMUs, accelerometers, magnetometers, or dead-reckoning systems can be used, or cameras recording and processing the environment. Alternatively or additionally, GPS coordinates could be used for determining the current position. Also, the laser pointer1could be connected with a nearby provider of reference signals, for example a mobile phone, which can act as a beacon and thus be used to determine the relative distance of the laser pointer1to the mobile phone.

Current positions piare received by the memory19from the orientation measurement unit18and stored together with the current orientations θias a set S′ of orientation samples22with position samples34. The aforementioned sampler23and low-pass filter24can be utilized for the current positions pi, too.

To compute the drive values DV, the drive circuit25receives in addition to the current orientation θialso the current position pi. The computation of the drive values DV can in this case not be performed with a subtraction, but is still simple enough to be determined by utilizing the principles of basic geometry.

Furthermore, the laser pointer1can also autonomously determine its distance dito the wall4by measuring the time-of-flight between emitting the beam3,8,12and receiving the reflection35of the laser beam3,8,12from the wall4in a distance measurement unit36of the laser generation unit13. Such systems are commonly known as LIDAR (light detection and ranging) systems.

Depending on the embodiment, the laser generation unit13and the distance measurement unit36can be two distinct but connected components that can interact with each other, e.g., the laser generation unit13can communicate a time of generating the laser beam3,8,12to the distance measurement unit36such that the distance measurement unit36can determine a time of flight of the laser beam3,8,12after receiving the corresponding reflection. The laser generation unit13and the distance measurement unit36could also be embodied as a single unit.

The distance measurement unit36outputs the current distance diat an output37thereof to an input38of the memory19. The memory19then stores the current distances direceived from the distance measurement unit36together with the current orientations θiand current positions pias a set S″ of orientation samples22with position samples34and distance samples39.

The drive circuit25also receives the current distances di at an input40and generates the set of drive values DV based on the current orientation θi, the current position pi, the current distance di, and the set of orientation samples22with position samples34and distance samples39, again by means of applying basic geometry.

The laser pointer1can also comprise extended functions by employing multiple laser generation units13and/or multiple MEMS mirrors14. In one embodiment (not shown), the laser pointer1has at least two laser generation units13, each emitting a laser beam3,8,12of a different wave-length onto said MEMS mirror14. The user can then, for example, manually choose to display the shapes5in green, blue, orange, red, or any other desired color provided by the multiple laser generation units13. A mixing of colors is possible, too.

It is even possible to vary the color within the same shape5(or for different shapes, e.g., different letters). To this end, the drive circuit25can control the intensity P of the laser beams3,8,12emitted by at least two laser generation units13and to use each of the multiple laser generation units13for different subsets of the set of drive values DV.

The field of view of a MEMS mirror is typically 60°-120° when optically extending the optical scan angle. While this is enough for some applications, the MEMS mirror14can generally deflect the laser beam3,8,12over a wider spatial area. To this end, the laser pointer1can have at least two MEMS mirrors14, each deflecting at least a part of said laser beam3,8,12, and the drive circuit25splits the set of drive values DV into partial sets for each of the MEMS mirrors14. For example, a beam splitter can be used to provide a part of the laser beam3,8,12for each MEMS mirror. The MEMS mirrors could alternatively also be cascaded to achieve a different or widespread behavior of deflection.

The disclosed subject matter is not restricted to the specific embodiments described in detail herein, but encompasses all variants, combinations and modifications thereof that fall within the framework of the appended claims.