EP3740806A1

EP3740806A1 - Device and method for projecting an image

Info

Publication number: EP3740806A1
Application number: EP18807032.0A
Authority: EP
Inventors: Peter Ostertag; Gael Pilard
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-01-17
Filing date: 2018-11-15
Publication date: 2020-11-25
Also published as: CN111615658A; DE102018200696A1; US20200366875A1; US11330233B2; WO2019141403A1

Abstract

The invention relates to a device (1a, 1b, 1c) for projecting an image, comprising: a laser device (2) which is designed to emit a laser beam (L), said laser device (2) having a modulating device (21) which is designed to modulate image data onto the laser beam (L); and a micromirror device (3) which is designed to deflect the laser beam (L) in a cell-shaped manner; wherein the modulating device (21) is designed to modulate the laser beam (L) such that a specified optical warning signal is emitted in a region around the reversal points of the cell-shaped deflection.

Description

description

title

Apparatus and method for projecting an image

The present invention relates to an image projection apparatus and a method of projecting an image. In particular, the invention relates to a laser scanner projector, such as a portable device.

State of the art

For the projection of images laser scanners with micromirrors can be used, with the micromirrors deflecting the emitted laser beam. To one

To generate a two-dimensional image, for example, a micromirror can be used, which is pivotable about two mutually orthogonal axes. For this purpose, the micromirror is usually resonantly oscillated at a fast frequency about a first axis, while the micromirror is quasistatically deflected about the second axis at a slow frequency. As a result, two mutually perpendicular sinusoids with different frequencies are superimposed. Thus, there is a substantially cellular motion of the laser beam, with one line being scanned during the half period of the fast displacement, and with one frame being scanned with a plurality of lines during a half cycle of slow displacement.

An exemplary micromirror device with a two-dimensionally deflectable micromirror is known from DE 10 2008 054784 A1.

Instead of a single micromirror, it is also possible to provide two micromirrors which are each pivotable about a pivot axis, wherein the

Swivel axes are orthogonal to each other. The frequencies of the deflections of the micromirrors differ, so that again a cell-shaped scanning is possible. When using such projectors due to the laser used, the eye safety must be considered. The lasers are classified according to DIN EN 60825-1 into different classes, which differ with regard to the danger to the human eye. For example, the maximum power delivered by a Class 3R laser is greater by a factor of 5 than that of a Class 2 laser. For classification of lasers, the maximum permissible exposure (MPE) may be considered, which is the highest power or energy density which is still considered safe for the human eye.

In order to determine the maximum permissible energy or power of a laser of a scanning unit, different scanning configurations of the scanning unit must be taken into account.

In a first criterion, the energy output is calculated while the pupil is once swept by the laser beam. According to a second criterion, the laser beam scans twice or more times over the eye. A third criterion takes into account the energy delivered to the pupil during an entire frame. In a fourth criterion, that is in a period up to the maximum

Exposure time energy taken into account. For example, the maximum exposure time for laser class 2 may be 0.25 seconds.

Corresponding calculations are made for different distances of the pupil from the scanning unit, which begin at about 100 millimeters. The biggest limitations arise when the eye is aligned with the scan unit.

The different criteria are for different angular positions of the micromirrors, i. H. for different solid angles of the scanned area, of different meaning.

Disclosure of the invention

The invention provides an apparatus for projecting an image having the features of claim 1 and a method for projecting an image with the

Features of claim 10 ready. According to a first aspect, the invention accordingly relates to a device for

Projecting an image with a laser device and a micromirror device. The laser device emits a laser beam and has a further

Modulation device which aufimoduliert image data on the laser beam. The micromirror device deflects the laser beam in a cell shape. The

Modulation device is further adapted to modulate the laser beam such that in a range around reversal points of the cellular deflection

predetermined optical warning signal is sent out.

According to a second aspect, the invention accordingly relates to a method for

Projecting an image. A laser beam is emitted by means of a laser device, image data being simulated onto the laser beam. The laser beam is deflected in a cell shape by means of a micromirror device. The laser beam is modulated such that in a range around reversal points of the cellular deflection

predetermined optical warning signal is sent out.

Preferred embodiments are the subject of the respective subclaims.

Advantages of the invention

An underlying realization of the invention is that the edge regions of the scanned solid angle range are particularly dangerous for the human eye. The border areas are those areas where the

Laser beam changes direction and a new line is scanned.

However, by emitting an optical warning signal in this outer area, a person who runs into the scanned area becomes ill

Eyelid reflex already close the eyes due to the warning signal. As a result, the person's eye is not exposed to dangerous radiation. The

Eye safety can be increased.

According to a preferred development of the device, the modulation device is designed to carry out the modulation of the laser beam for emitting the optical warning signal as a function of the modulated image data.

For example, the emitted image may be particularly dangerous to the eye, such as in large white areas of high intensity. In this case, the warning signal is preferably transmitted continuously. In particular, the warning signal on

Reversal point of each line to be sent out. Also the area around the

Reversal point during which the warning signal is emitted may depend on the intensity of the image data, and preferably be greater, the stronger the intensity of the image data. Furthermore, the warning signal can only be transmitted if an intensity calculated on the basis of the image data exceeds a predefined threshold value. For example, the total intensity during a frame may be calculated and compared to the predetermined threshold.

According to a preferred development, the device has a computing device which calculates the energy of the laser beam during the deflection along at least one line. The modulation device is designed to perform the modulation of the laser beam for emitting the optical warning signal as a function of the calculated energy. For example, the energy of the laser beam may be calculated during a predetermined number of the next scanned lines. In particular, the next two scanned lines can be taken into account. If the determined energy exceeds a predetermined threshold value, a warning signal is output by modulation of the laser beam at the end of the next scanned line. Otherwise, no warning signal is output. The

Threshold can be set, for example, based on an allowable energy limit (AEL). In particular, the threshold may be equal to a predetermined percentage of the allowable energy limit, about 90 percent. The modulation device thus emits the optical warning signal at the end of the line if the energy of the laser beam during the deflection along this line and / or along adjacent lines exceeds a predetermined threshold.

According to a preferred embodiment of the device, the image data are modulated onto the laser beam by the modulation device in such a way that edge regions of the lines are masked out except for the warning signal. By hiding the border areas, distortions can be corrected. In addition, there is a gap between the area of the displayed image and the area in which the warning signal is displayed. Since the warning signal already triggers the eyelid reflex, a person who moves into the scanned area already has before reaching the eyelid actual image content the eye closed or turned away. As a result, eye damage can be avoided.

According to a preferred development of the device, the modulation device is designed to modulate the laser beam to emit the optical

Warning signal depending on a size of the hidden edge area

perform. The stronger the distortion, the larger the hidden edge area. Since the danger of the laser beam for the eyes decreases from the edge in the direction of the center, the laser thus represents a lower risk. Accordingly, the warning signal can only be displayed if the size of the hidden edge region falls below a predetermined threshold value.

According to a preferred development, the device has a sensor device which outputs a detection signal if a person moves toward a solid angle range scanned by means of the micromirror device. The

Modulation device performs the modulating of the laser beam for emitting the optical warning signal in response to the detection signal. Thus, the visual warning signal can only be displayed if it is detected that a person is moving towards the scanned solid angle range. This avoids unnecessarily displaying warning signals and lessens the viewer.

The warning signal may in one embodiment consist of individual pulses or pixels directly at the reversal points or in the vicinity of the reversal points. The laser device may, for example, have a green, a blue and a red laser. The warning signal can only be emitted by the red laser.

The observer thereby sees a line-shaped red area at the edge of the scanned solid angle area.

According to one development of the device, the modulation device is designed to modulate the laser beam in such a way that a band-shaped region of a predetermined color and / or a predetermined intensity is transmitted continuously along the points of reversal of the cellular deflection as an optical warning signal. The band-shaped region can in turn preferably be generated by the red laser. Preferably, the modulation device modulates the laser beam in such a way that the optical warning signal is harmless to the human eye.

Brief description of the drawings

Show it:

Figure 1 shows a schematic course of the permissible energy limit in

Dependence on the scan angle;

Figure 2 is a schematic diagram for explaining the determination of the permissible

Energy limit;

Figure 3 is a schematic block diagram of an apparatus for projecting an image according to a first embodiment of the invention;

Figure 4 is a schematic block diagram of an apparatus for projecting an image according to a second embodiment of the invention;

Figure 5 is a schematic block diagram of an apparatus for projecting an image according to a third embodiment of the invention;

FIG. 6 shows a scanned solid angle area with a hidden area

Area;

FIG. 7 shows a band-shaped warning signal; and

Figure 8 is a flowchart of a method of projecting an image according to an embodiment of the invention. In all figures the same or the same function elements and devices are provided with the same reference numerals.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS In the following it will first be explained why the edge region of a

Solid angle range, which is scanned by means of deflected by a micromirror laser light, represents a particular danger to the human eye. In FIG. 1, for this purpose, the permissible energy limit (AEL) is mapped as a function of a scan angle Q of the micromirror around the fast axis, both variables being one normalized. The permissible energy limit is set for the selected laser class based on the maximum permissible exposure (MPE).

As can be seen for a first curve X, for small scan angles Q, d. H. near the center of the scanned solid angle region, a substantially sinusoidal curve XI of the permissible energy limit. The limitation of the permissible

The energy limit here derives essentially from the first criterion described above, d. H. the simple catching of the eye. For larger scan angles Q, d. H. closer to the turning point, the time interval between two successive scans of the eye becomes smaller. This results in the strongest constraint by the second criterion described above, i. H. Twice the catching of the eye. This results in a substantially linear region X2.

Due to the oscillating movement of the micromirror, the brightness distribution is generally not uniform. For example, if the displayed first curve X is used to determine the power of the laser, the displayed image may appear darker in lateral areas than in the center. To improve a sine correction can be performed. Here, however, it must be ensured that the power does not exceed the permissible energy limit, resulting in a second curve Y results.

The allowable energy limit is defined as the power of the light that passes through the pupil at a given scan angle. The laser beam follows a sinusoidal movement. The average power P_m of the light at

Passage through the pupil is given by the following formula:

Here, t1 and t2 denote the times at which the beam reaches or leaves the pupil. Further, w = 2pί is the fast angular frequency of the laser scanner and f is the resonant frequency of the fast axis. P O is the instantaneous power in the center of the picture.

The sinusoidal resonant motion of the micromirror can be described by the following equation for the scan angle Q: 0 (t) = 0 _hjnax * cos (w + f)

If the phase angle f = p / 2 is selected at the time t = 0, the result is: q = 9 _{h max} si n (mt) t = - - sin ^{- 1} (^ -) ^ [sin (

w - ^a h_max · '

Here, 0_h_max denotes the maximum mechanical angle of the amplitude of the resonant axis.

The time taken by the beam to scan the pupil R is given as Tp = t2-tl. The angular difference q_r = 0 (t2) - 0 (tl) corresponds to the angular extent of the pupil R.

The relationships mentioned are illustrated in FIG.

It is possible to calculate the corresponding instantaneous power in the center of the image for each value of the allowable energy limit along the scan motion by integrating the average power P_m:

The time taken for the laser to scan the pupil is greater than at the center due to the movement of the laser at the edge of the image. At the same time, however, the average power Pm is smaller, so that in general the calculated value of the instantaneous power PO is smaller when the pupil is in the edge area of the image. The smallest value of the instantaneous power PO defines the maximum permissible power of the light in the center of the image, if the intensity is corrected homogeneously. If the instantaneous power PO were to be increased, the instantaneous edge power would exceed the allowable power limit and the device would not meet the criteria of the laser class. Using the permissible energy limit to assess the danger results in the marginal area of the image being more dangerous than the central area of the image. However, this area is particularly relevant, since a person will usually move from the side to the scanned area.

FIG. 3 illustrates a block diagram of an apparatus 1a for projecting an image according to an embodiment of the invention.

The device 1 comprises a laser device 2 with one or more lasers 22 which emit a laser beam L. Specifically, a red, a green and a blue laser can be provided which emit respective single beams, the laser beam L being generated by combining the individual beams ,

The lasers 22 are controlled by a modulation device 21, which modulates the power of the laser 22 in such a way that corresponding image data are modulated onto the laser beam L. The image data can be transmitted to the modulation device 21, for example, via an interface from external devices.

The device la further comprises a micromirror device 3, which the

Laser beam L is deflected like a cell.

The modulation device 21 modulates the laser beam L such that a predetermined optical warning signal is transmitted in a region around the reversal points of the cell-shaped deflection. An optical warning signal can be understood to mean pulsed light signals which are punctiform or linear

Reversal point of the line to be sent out. If such light signals are emitted in a plurality of successive lines, a line-shaped or band-shaped optical signal results for the viewer, which is generated directly at or in the vicinity of the reversal points.

Optionally, a computing device 4 is further provided, which calculates the energy of the laser beam L during the deflection along at least one line. If the energy exceeds a predetermined threshold which is determined as a function of the permissible energy limit, the modulation device 21 transmits the optical warning signal at the end of the at least one line. Optionally, a sensor device 5 is furthermore provided which can recognize persons who are moving toward the solid angle range scanned by means of the micromirror device 3. The sensor device 5 may for example comprise a light barrier or a camera system which detects the movement of persons. If it is detected that a person or generally an object on the scanned

Solid angle range, the modulation device 21 generates the optical warning signal.

FIG. 4 illustrates a schematic view of an apparatus 1b for projecting an image according to a second embodiment of the invention. The device 1b essentially corresponds to the device 1a, so that only the differences are explained in more detail below. The micromirror device 3 has a first micromirror 31 and a second micromirror 32, which are pivotable about mutually perpendicular axes A1 and A2. The first micromirror 31 is deflected at a high frequency up to a maximum first scan angle. These

Deflection produces a horizontal line-shaped scan. The second

Micromirror 32 is deflected at a lower frequency up to a maximum second scan angle, resulting in a horizontal deflection of the laser beam L.

Overall, the illustrated cellular scan results in a scan area B to reduce distortion and a more uneven light distribution

Edge regions Bl and B2 by modulation of the laser power through the

Modulation device 21 hidden, apart from the optical warning signals.

The optical warning signals P1 to P4 are emitted at the reversal point of a cell-shaped deflection of the laser beam L. For example, a red signal can be sent out.

The visual warning signals P1 to P4 may preferably be sent out at each of the reversal points. However, it is also possible to send the warning signals P1 to P4 only for a predetermined number of reversal points.

FIG. 5 illustrates a block diagram of a device 1c of a device for projecting an image according to a third embodiment. In contrast to

Device 1b, the micromirror device 3 has a single micromirror 33, which can be pivoted about two orthogonal axes A1, A2. The micromirror 33 Performs a fast resonant oscillation about a vertical axis Al and a quasi-static slow oscillation about a horizontal axis A2.

FIG. 6 illustrates an exemplary scanning region B. To prevent

Distortions, for example due to a projection onto an odd or twisted relative to the micromirror device 3 substrate become edge regions B3

hidden. The laser beam L can be emitted in the form of a pixel or pulse. The corresponding pixels U1 to U6 yield a corresponding image as a function of the image data. Furthermore, at the reversal point, optical warning signals P are emitted, which are located in the blanked-out area B3 and thus have a distance from the image area or scan area B.

The modulation device 21 may be designed to transmit the optical warning signals P only if the size of the blanked region B3 falls below a predetermined threshold value.

According to further embodiments, the modulation device 21 may be designed to transmit the warning signal as a function of the image data.

FIG. 7 illustrates a further exemplary scan region B, which corresponds to the emitted image. In a recessed area B4 becomes a

continuous optical warning signal Q issued. In the case of the plurality of lines, a band-shaped area F of the optical warning signal results for the viewer.

The band-shaped region F is preferably located directly at the reversal points of the lines, d. H. at the outermost area of the area which can be scanned by means of the micromirror device 3. However, the band-shaped region F can also have a distance to the reversal points illustrated in FIG.

FIG. 8 illustrates a flowchart of a method for projecting an image according to an embodiment of the invention. For this purpose, in a method step St, a laser beam L is emitted by means of a laser device, with image data being modulated onto the laser beam L. In a method step S2, the laser beam L is deflected in a cell shape by means of a micromirror device 3. The laser beam L is modulated in such a way that a predetermined optical warning signal is emitted in a region around the reversal points of the cell-shaped deflection.

Claims

claims

A device (1a, 1b, 1c) for projecting an image, comprising: a laser device (2) which is designed to emit a laser beam (L), the laser device (2) having a modulation device (21) which adjusts thereto is adapted to aufzumodulieren image data on the laser beam (L); and a micro-mirror device (3) which is designed to deflect the laser beam (L) in a line-shaped manner; characterized in that the modulation means (21) is adapted to modulate the laser beam (L) such that in an area around

Reversal of the cellular deflection is emitted a predetermined optical warning signal.

2. Device (la, lb, lc) according to claim 1, wherein the modulation means (21) is adapted to modulating the laser beam (L) for emitting the optical warning signal in response to the modulated image data

perform.

3. Device (la, lb, lc) according to claim 1 or 2, further comprising a

Computing device (4), which is designed to calculate an energy of the laser beam (L) during the deflection along at least one line, wherein the modulation device (21) is adapted to modulating the laser beam (L) for emitting the optical warning signal in Depend on the calculated energy.

4. Apparatus (1a, 1b, lc) according to claim 3, wherein the modulation means (21) emits the optical warning signal at the end of a line if the energy of the laser beam (L) during the deflection along that line and / or adjacent lines a predetermined Threshold exceeds.

5. Device (1a, 1b, 1c) according to one of the preceding claims, wherein the modulation device (21) modulates the image data onto the laser beam (L) in such a way that edge regions of the lines are blanked out except for the optical warning signal.

6. Device (1a, 1b, lc) according to claim 5, wherein the modulation means (21) is adapted to modulating the laser beam (L) for emitting the optical warning signal in dependence of a size of the suppressed

Edge area.

7. Device (la, lb, lc) according to one of the preceding claims, further comprising a sensor device (5) which is adapted to output a detection signal, if a person moves to a scanned by means of the micromirror device (3) solid angle range, wherein the

Modulation device (21) is adapted to modulating the laser beam (L) for emitting the optical warning signal as a function of

Perform detection signal.

8. Device (1a, 1b, lc) according to one of the preceding claims, wherein the modulation device (21) is adapted to modulate the laser beam (L) such that continuously a band-shaped area of a predetermined color and / or intensity along the turning points the cellular deflection is emitted as an optical warning signal.

9. Device (la, lb, lc) according to any one of the preceding claims, wherein the modulation means (21) is adapted to modulate the laser beam (L) such that the optical warning signal is harmless to the human eye.

10. A method of projecting an image, comprising the steps of:

Emitting a laser beam (L) by means of a laser device (2), image data being modulated onto the laser beam (L); and cell-shaped deflection of the laser beam (L) by means of a Micromirror device (3); wherein the laser beam (L) is modulated such that in a range around reversal points of the cell-shaped deflection, a predetermined optical warning signal is emitted.