JP2013105108A - Image projection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress strain of a projected image.SOLUTION: An image projection apparatus includes: a projection part for projecting an image obliquely to the emission direction of projection light 12; a frame memory 30 that retains image data of the image and outputs the image data synchronously with a read signal for every pixel data; a laser emission part 25 that emits laser light according to the output pixel data; an MEM mirror 20 that scans the laser light and emits it as projection light; and a control part 32 that changes an interval of the read signal of a horizontal scanline distant from the projection part shorter than that of a horizontal scanline close to the projection part.

Description

  The present invention relates to an image projection apparatus, for example, an image projection apparatus using a MEMS mirror.

  In recent years, portable image projection apparatuses have been used. For example, a mobile phone terminal having a projector function is used. In such an image projection apparatus, an image is projected as projection light by scanning with laser light. There is also an image projection apparatus that projects an image obliquely with respect to the direction in which the projection light is emitted. For example, Patent Document 1 discloses an image projection apparatus that projects an image on a plane on which the image projection apparatus is installed.

JP 2011-70135 A

  In an image projection apparatus that projects an image obliquely with respect to the direction in which the projection light is emitted, it is considered that the laser light is scanned using a MEMS (Micro Electro Mechanical Systems) mirror to obtain the projection light. In this case, the swing range of the MEMS mirror cannot be changed in a short time. For this reason, the projected image is distorted.

  The present invention has been made in view of the above problems, and an object thereof is to suppress distortion of a projected image.

  The present invention provides a projection unit that projects an image obliquely with respect to the emission direction of projection light, a frame memory that holds image data of the image, and outputs the image data in synchronization with a read signal for each pixel data; A laser emitting unit that emits a laser beam according to the output pixel data, a MEMS mirror that scans the laser beam and emits it as projection light, and a horizontal scanning line that is far from the projection unit with a distance between the read signals close to a horizontal line And a control unit that makes the scanning line shorter than the scanning line. According to the present invention, distortion of a projected image can be suppressed.

  In the above configuration, the control unit outputs a horizontal scanning line far from the projection unit during a period in which the read signal is not output near the turn and the read signal is not output, among the horizontal swings of the MEMS mirror. It can be configured to be longer than the near horizontal scanning line.

  In the above configuration, the control unit may be configured such that the interval between the read signals is longer than the end of the same horizontal scanning line.

  In the above-described configuration, the control unit may be configured such that, in the same horizontal scanning line, the difference in the interval between the lead signals between the center and the end is made smaller in the horizontal scanning line far from the projection unit than in the near horizontal scanning line. .

  The said structure WHEREIN: The said control part can be set as the structure which produces | generates the said read signal based on the horizontal synchronizing signal of the said MEMS mirror.

  In the above configuration, the control unit may include a VCO and generate the read signal using the VCO.

  In the above configuration, the control unit synchronizes with a horizontal synchronization signal of the MEMS mirror and a storage unit that stores data of the control signal and the waveform of the EN signal, and performs the control based on the data of the waveform of the control signal and the EN signal. A waveform generating unit that generates a signal and the EN signal, a VCO that changes a frequency of an oscillation signal that is output based on the control signal, and when the EN signal is active, the oscillation signal is output as a read signal, When the EN signal indicates inactivity, a mixer that does not output the oscillation signal may be included.

  In the above configuration, the frame memory may be configured to output in a direction alternate with respect to the direction in which data corresponding to the horizontal scanning line is written.

  In the above configuration, the frame memory may be configured to output data corresponding to the horizontal scanning line in a direction orthogonal to the direction in which the data is written.

  The said structure WHEREIN: The said image projection apparatus can be set as the structure which installs on the plane and projects the said image on the said plane.

  According to the present invention, distortion of a projected image can be suppressed.

FIG. 1A is a side view of the image projection apparatus according to the first embodiment, and FIG. 1B is a top view. FIG. 2 is a functional block diagram of the image projection apparatus according to the first embodiment. FIG. 3 is a schematic diagram illustrating scanning lines for projecting an image in the first embodiment. FIG. 4 is a schematic diagram showing scanning lines with respect to angles within the range 50. FIG. 5 is a schematic diagram showing the scanning angular velocity with respect to the angle within the range 50. FIG. 6 is a conceptual diagram showing pixel data to be read with respect to time. FIG. 7 is a schematic diagram showing a read signal with respect to time. FIG. 8 is a schematic diagram of a read signal generation circuit. FIG. 9A and FIG. 9B are diagrams showing a control signal and an EN signal with respect to time, respectively. FIGS. 10A to 10D are schematic diagrams illustrating writing and reading of image data in the frame memory according to the first embodiment. FIG. 11A to FIG. 11D are schematic diagrams illustrating writing and reading of image data in the frame memory according to the second embodiment. 12A to 12D are schematic diagrams illustrating writing and reading of image data in the frame memory according to the third embodiment. FIG. 13 is a diagram illustrating a control signal with respect to time according to the third embodiment. FIG. 14 is a plan view of the image projection apparatus according to the fourth embodiment. FIGS. 15A to 15D are schematic diagrams illustrating writing and reading of image data in the frame memory according to the fourth embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1A is a side view of the image projection apparatus according to the first embodiment, and FIG. 1B is a top view. As shown in FIGS. 1A and 1B, the image projector 10 is placed on a plane 16. The image projection device 10 may be, for example, a mobile phone terminal, a camera, a portable navigation device, a personal computer, a game machine, or a single image projection device. A projection unit 18 is provided on the front surface of the image projection apparatus 10. Projection light 12 is emitted from the projection unit 18. The projection light 12 is irradiated onto the plane 16 and the image 14 is projected. It is used as a screen for projecting the image 14 onto the plane 16 on which the image projection device 10 is placed. As described above, the projection unit 18 projects the image 14 obliquely with respect to the emission direction of the projection light 12. For example, the plane 16 may be a wall, and the image projector 10 may be installed on the wall. Further, the plane 16 may be a white board or the like. Furthermore, the image projection device 10 can be placed on the wrist and an image can be projected onto the palm.

  FIG. 2 is a functional block diagram of the image projection apparatus according to the first embodiment. As shown in FIG. 2, the image projection apparatus 10 mainly includes a projection unit 18, a MEMS mirror 20, a MEMS drive unit 22, a laser emission unit 25, a frame memory 30, a control unit 32, and an image processing unit 36. .

  The image processing unit 36 performs image processing on the input image data. The image data may be, for example, moving image data or still image data. The image processing unit 36 may perform white balance, color space conversion, γ conversion unit, color correction, and the like. Further, the image processing unit 36 may decode the compressed image data. The image processing unit 36 holds the image data in the frame memory 30 for each pixel data in synchronization with the clock signal. When the image data is a moving image, the image processing unit 36 causes the frame memory 30 to hold the image data for each frame. The frame memory 30 is, for example, a DRAM (Dynamic Random Access Memory), and temporarily holds image data. The frame memory 30 synchronizes the image data with the read signal for each pixel data and outputs the image data to the LD driving unit 28 of the laser emitting unit 25.

  The laser emitting unit 25 includes an optical system 24, laser diodes (LD) 26 a to 26 c, and an LD driving unit 28, and emits laser light according to pixel data input from the frame memory 30. The LD driving unit 28 DA converts the image data into RGB analog signals for each pixel data. The LD drive unit 28 outputs the RGB analog signals to the corresponding LDs 26a to 26c. The LDs 26a to 26c respectively emit red laser light, green laser light, and blue laser light based on the RGB analog signals. The red laser light, the green laser light, and the blue laser light are irradiated to the MEMS mirror 20 through the optical system 24 as laser light with the optical axes aligned. The LD driving unit 28 causes the LDs 26a to 26c to emit laser beams having the same intensity until the next pixel data is input. The RGB analog modulation signals output from the LD driving unit 28 to the LDs 26a to 26c may be intensity modulation or PWM (Power Width Modulation). Moreover, these combinations may be sufficient.

  The MEMS drive unit 22 swings the MEMS mirror 20 horizontally using the oscillation signal of the oscillator 23 as a horizontal synchronization signal. Thereby, the MEMS mirror 20 scans the laser beam and emits it as the projection light 12. The oscillator 23 of the MEMS mirror 20 is, for example, a crystal oscillator or a PLL (Phase Locked Loop). The MEMS mirror 20 oscillates in the vertical direction with a longer period than the oscillation in the horizontal direction. The control unit 32 includes a VCO (Voltage Controlled Oscillator) 34, generates a read signal based on the horizontal synchronization signal Hs, and outputs the read signal to the frame memory 30. When one frame of image data is output from the frame memory 30, the control unit 32 outputs a reset signal to the MEMS drive unit 22. When the MEMS driving unit 22 receives the reset signal, the MEMS driving unit 22 turns back the vertical swing.

  As described above, ½ of the horizontal oscillation period of the MEMS mirror 20 is a period corresponding to one MEMS scanning line. A half of the vertical oscillation period of the MEMS mirror 20 is a period corresponding to one frame. Note that the horizontal swing of the MEMS mirror 20 is a swing corresponding to the horizontal scanning line of the image 14 and does not have to be physically a horizontal swing. Similarly, the vertical swing is a swing corresponding to the vertical direction of the image and may not be physically vertical.

  The image processing unit 36, the frame memory 30, the control unit 32, and the like can be realized using FGPA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), or the like.

  FIG. 3 is a schematic diagram illustrating scanning lines for projecting an image in the first embodiment. FIG. 3 corresponds to a view seen from above. With reference to FIG. 3, a range 50 indicates a range of the projection light 12 emitted from the projection unit 18 of the image projection device 10. Since the swing range of the MEMS mirror 20 cannot be changed at high speed, the angle of the range 50 is constant. A range 50 is a range of an angle θ from the center line to the left and right. In addition, since the oscillation cycle of the MEMS mirror 20 cannot be changed at high speed, the oscillation cycle is constant. A scanning line scanned by the MEMS mirror 20 is a MEMS scanning line. The MEMS scanning line includes a horizontal scanning line 52 and a temporary scanning line 51. A horizontal scanning line 52 indicates a MEMS scanning line in the image 14. Laser light constituting the projection light 12 is scanned by the MEMS mirror 20 like a horizontal scanning line 52. On the other hand, the MEMS mirror 20 also swings outside the image 14. Outside the image 14, the laser light is not emitted from the projection unit 18. For example, the laser emitting unit 25 does not emit laser light. The provisional scanning line 51 indicates that the MEMS mirror 20 is oscillating although the laser beam is not scanned.

  A description will be given assuming that scanning starts from the upper left in the range 50. First, in the MEMS scanning line in the uppermost scanning region H 1 of the image 14, the laser beam is not emitted from the projection unit 18 outside the image 14, and the MEMS mirror 20 is scanned like the temporary scanning line 51. In the image 14, laser light is emitted from the projection unit 18, and the horizontal scanning line 52 is scanned. Outside the image 14, the temporary scanning line 51 is scanned. The line 50 is folded back at the right end of the range 50, falls vertically down one line, and the temporary scanning line 51 is scanned outside the image 14. In this manner, the temporary scanning line 51 and the horizontal scanning line 52 are scanned.

  FIG. 4 is a schematic diagram showing scanning lines with respect to angles within the range 50. 4 shows a scanning region H1 above the image 14 (farthest from the projection unit 18), an intermediate scanning region Hm, and a scanning region Hn below the image 14 (closest to the projection unit 18). A solid line indicates the horizontal scanning line 52 in the image 14, and a broken line indicates the temporary scanning line 51 outside the image 14. As shown in FIG. 4, the ratio of the range of the horizontal scanning lines 52 in the range 50 is small in the scanning region H1. In the scanning region Hn, the ratio of the horizontal scanning lines 52 within the range 50 is large (100% in the example of FIG. 4). The oscillation period of the MEMS mirror 20 is constant, and the number of pixels per horizontal scanning line 52 is constant in the scanning regions H1 to Hn. For this reason, in the scanning region H1 far from the projection unit 18, the time interval for reading out pixel data from the frame memory 30 is shortened as compared with the near scanning region Hn.

  FIG. 5 is a schematic diagram showing the scanning angular velocity with respect to the angle within the range 50. As shown in FIG. 5, the MEMS mirror 20 has a lower scanning angular velocity at the turn-back position than the center of the range 50. The fact that the oscillation cycle of the MEMS mirror 20 is constant and that the angular velocity is slow at the turn-back position are due to structural restrictions that the MEMS mirror 20 mechanically oscillates the mirror.

  FIG. 6 is a conceptual diagram showing pixel data to be read with respect to time. The horizontal axis indicates time. At the oscillation period T of the MEMS mirror 20, the period of one MEMS scanning line corresponds to 1/2 × T. A period 54 of one section in the horizontal scanning line 52 corresponds to one pixel data. In FIG. 6, the number of pixel data per horizontal scanning line 52 is simplified to 10 pixel data. If scanning of the MEMS mirror 20 is started from the left end of the range 50 in FIG. 3 at time 0, the MEMS scan line passes through the center of the range 50 at time 1/4 × T, and time 1/2 × At T, the right end of range 50 is reached. Pixel data is read from the frame memory 30 between time T1 and time T2.

  On the other hand, in the scanning region Hn, pixel data is read from the frame memory 30 between time 0 and time 1/2 × T. In the scanning region Hn, the reading time interval per pixel data becomes longer than the scanning region H1. For example, the time interval Tnc near the center of the Hn horizontal scanning line 52 is longer than the time interval T1c near the center of the H1 horizontal scanning line 52. Similarly, the time interval Tne near the end of the Hn horizontal scanning line 52 is longer than the time interval T1e near the end of the H1 horizontal scanning line 52. Furthermore, as described in FIG. 5, due to the modulation of the angular velocity of the MEMS mirror 20, the readout time interval per pixel data near the end is longer than that near the center of the horizontal scanning line 52. For example, the time interval T1e near the end is longer than the time interval T1c near the center of the horizontal scanning line 52 of H1. The time interval Tne near the end is longer than the time interval Tnc near the center of the horizontal scanning line 52 of Hn.

  FIG. 7 is a schematic diagram showing a read signal with respect to time. FIG. 7 shows a read signal that gives the frame memory 30 the timing for reading pixel data from the frame memory 30 at time intervals as shown in FIG. 6 in the scanning regions H1 and Hn. For example, the frame memory 30 starts outputting pixel data at the peak of the read signal. In the scanning region H1, the read signal does not vibrate and does not have a peak during a period in which pixel data is not read (before T1 and after T2). During this period, the laser emitting unit 25 does not emit laser light. The read signal has a longer period of Hn than H1. For example, the time intervals Tnc and Tne are longer than the time intervals T1c and T1e, respectively. The read signal has a longer period in the time corresponding to the vicinity of the end than the time corresponding to the vicinity of the center of the horizontal scanning line 52. For example, the time intervals T1e and Tne are longer than the time intervals T1c and Tnc, respectively.

  FIG. 8 is a schematic diagram of a read signal generation circuit. The read signal generation circuit 60 is included in the control unit 32. As shown in FIG. 8, the read signal generation circuit 60 includes a VCO 34, a mixer 62, a memory 64 (storage unit), and a waveform generation unit 66. The memory 64 is, for example, a non-volatile memory, and stores waveform data of the control signal and the EN signal. The waveform generation unit 66 generates the control signal Vc and the EN signal in synchronization with the horizontal synchronization signal based on the control signal and the EN signal waveform data stored in the memory 64, respectively. A control signal Vc is input to the VCO 34. The VCO 34 changes the frequency of the oscillation signal output based on the control signal Vc. The oscillation signal and the EN signal are mixed by the mixer 62. The mixer 62 outputs an oscillation signal as a read signal when the EN signal is active (eg, high level), and does not output an oscillation signal when the EN signal is inactive (eg, low level). For example, the mixer 62 outputs a constant signal as a read signal.

  FIG. 9A and FIG. 9B are diagrams showing a control signal and an EN signal with respect to time, respectively. A period 58 from time 0 to time ½ × nT corresponds to a period in which one frame of image data is read from the frame memory 30. Each of the periods 56a to 56n corresponds to a period for reading data of one MEMS scanning line from the frame memory 30. The period 56a is a period for reading data in the scanning region H1, and the period 56n is a period for reading data in the scanning region Hn. Note that the periods 56a to 56n are determined in synchronization with the reset signal output from the MEMS drive unit 22. That is, the periods 56a to 56n are synchronized with ½ of the period in which the MEMS mirror 20 swings.

  As shown in FIG. 9A, the control signal Vc decreases from time 0 to time 1/2 × nT. As a result, the oscillation signal output from the VCO 34 has a lower oscillation frequency (that is, a longer period) from the scanning region H1 to Hn. Further, the control signal Vc is high at the center of each of the periods 56a to 56n and is low at both ends. As a result, the oscillation signal output from the VCO 34 has an oscillation frequency that is high near the respective centers in the scanning regions H1 to Hn and is low near both ends (that is, the period is shortened and the period is lengthened near the center).

  As shown in FIG. 9 (b), the EN signal is at a low level from time 0 to time T1 and from time T1 to 1/2 × T in the period 56a (the time T1 and T2 are shown in FIG. 7). See). From time T1 to time T2, the EN signal is at a high level. The high-level period TH of the EN signal gradually increases with time, and in the period 56n, the entire period is high. The control signal and the EN signal are signals obtained by inverting the period from time 0 to 1/2 × nT in the period from time 1/2 × nT to nT.

  By inputting the control signal Vc of FIG. 9A and the EN signal of FIG. 9B to the read signal generation circuit 33 of FIG. 8, a read signal as shown in FIG. 7 is generated. The waveforms of the control signal Vc and the EN signal differ depending on the angle between the projection light 12 and the projected plane. Therefore, the memory 64 stores waveforms of the control signal Vc and the EN signal corresponding to various angles.

  FIGS. 10A to 10D are schematic diagrams illustrating writing and reading of image data in the frame memory according to the first embodiment. 10A and 10C show a case where image data is written to the frame memory 30, and FIGS. 10B and 10D show a case where image data is read from the frame memory 30. FIG. The numbers shown on the left of the frame memory 30 indicate the order in which horizontal data (data corresponding to the horizontal scanning lines) in the image data is written or read. Arrows indicate the direction of writing or reading horizontal data.

  As shown in FIG. 10A, when the image processing unit 36 writes the image data to the frame memory 30, the horizontal data is written in the same direction from the left to the right from the top. As shown in FIG. 10B, when the control unit 32 reads the image data from the frame memory 30, the horizontal data is alternately read in order from the top. When the MEMS mirror 20 moves from the left to the right in the first horizontal scanning line of one frame of the image data, the control unit 32 displays the image data from the left to the right as in the top horizontal data in FIG. One horizontal scanning line is read out. In the next horizontal scan line, the MEMS mirror 20 moves from right to left. At this time, like the second horizontal data, the control unit 32 reads the image data for one horizontal scanning line from right to left. As described above, the control unit 32 can read image data from the frame memory 30 in response to the horizontal swing of the MEMS mirror 20.

  Referring to FIG. 10C, when the reading of one frame of image data from the frame memory 30 is completed, the image processing unit 36 writes the image data into the frame memory 30 as in FIG. Since the MEMS mirror 20 also swings in the vertical direction, as shown in FIG. 10D, when the control unit 32 reads image data in the next frame, the horizontal scanning line is shifted from the bottom to the top. Read data alternately.

  When the MEMS mirror 20 is used to emit laser light as the projection light 12 and the projection unit 18 projects the image 14 obliquely with respect to the emission direction of the projection light 12, the MEMS mirror 20 is swung as shown in FIG. Since the range 50 is constant, the image 14 is distorted. According to the first embodiment, as illustrated in FIG. 7, the control unit 32 shortens the interval between the read signals from the horizontal scanning line H1 far from the projection unit 18 to the horizontal scanning line Hn. Thereby, the image 14 can be projected into a rectangle as shown in FIG. It is preferable that the interval between the read signals is gradually shortened from the H1 horizontal scanning line to the Hn horizontal scanning line.

  Further, as shown in FIG. 7, the control unit 32 does not output a read signal in the vicinity of the turn of the horizontal swing of the MEMS mirror 20 and does not output a read signal in the horizontal direction H1 far from the projection unit 18. The scanning line is made longer than the horizontal scanning line of near Hn. Thereby, as shown in FIG. 3, the image is not projected outside the range of the image 14. It is preferable that the period during which the read signal is not output is gradually increased as it goes from H1 to Hn.

  Furthermore, as shown in FIG. 7, the control unit 32 makes the interval between the read signals longer than the end of the center of the same horizontal scanning line. Thereby, even when the MEMS mirror 20 has a lower angular velocity at the end than the center of the swing range 50 as shown in FIG. It is preferable that the interval between the read signals is gradually increased from the center to the end of the same horizontal scanning line.

  Further, as shown in FIG. 6, since the horizontal scanning line H1 is a part of the swing range 50 of the MEMS mirror 20, the difference in angular velocity between the center and the end of the horizontal scanning line H1 is Hn horizontal scanning line. Smaller than. Therefore, as shown in FIG. 7, the control unit 32 makes the difference in the interval between the read signals at the center and the end of the same horizontal scanning line smaller than the horizontal scanning line of Hn that is closer to the horizontal scanning line of H1 far from the projection unit 18. It is preferable to do. For example, T1e-T1c is made smaller than Tne-Tnc. Alternatively, (T1e−T1c) / (T1e + T1c) is made smaller than (Tne−Tnc) / (Tne + Tnc). Also, it is preferable that the difference in the interval between the read signals between the center and the end of the same horizontal scanning line is gradually reduced as it goes from H1 to Hn.

  As shown in FIG. 8, the control unit 32 generates a read signal based on the horizontal synchronization signal Hs of the MEMS mirror 20. Thereby, reading of the pixel data from the MEMS mirror 20 and the frame memory 30 can be synchronized. Note that if the read signal is synchronized with the horizontal synchronization signal Hs of the MEMS mirror 20, the reading and writing of the image data to the frame memory 30 may not be synchronized. For example, in the first embodiment, image data is written into the frame memory 30 using a clock signal independent of the horizontal synchronization signal Hs. When the timing of reading and writing image data to the frame memory 30 is shifted, the timing of reading and writing is corrected by skipping one frame of image data or using one frame of image data twice. be able to.

  Further, as shown in FIG. 8, the control unit 32 includes a VCO 34 and generates a read signal using the VCO 34. If an attempt is made to store the waveform of the read signal directly in the memory, the amount of data becomes enormous. In addition, waveform generation is performed at high speed. On the other hand, the waveform of the control signal Vc is stored in the memory 64 and a read signal is generated by applying the control signal Vc to the VCO 34 as a control voltage. Thereby, a read signal can be easily generated.

  Further, as shown in FIG. 8, the control unit 32 generates a read signal using the memory 64, the waveform generation unit 66, the VCO 34, and the mixer 62. Thereby, it is possible to easily generate a read signal.

  As shown in FIG. 1A, when the image projection apparatus 10 is installed on the plane 16 and projects the image 14 onto the plane 16, the image 14 is particularly easily distorted. Therefore, in this case, it is preferable that the control unit 32 generates the read signal described above.

  Even if the light intensity of the laser light emitted from the laser emitting unit 25 is the same, the luminance of the pixels in the image 14 changes if the period for projecting one pixel data changes. Therefore, when the interval between the read signals is long, the laser emission unit 25 can reduce the intensity of the laser beam, and when the interval between the read signals is short, the laser emission unit 25 can increase the intensity of the laser beam. For example, the laser emission unit 25 can increase the intensity of the laser light in the horizontal scanning line H1 far from the projection unit 18 than in the horizontal scanning line Hn. The intensity of the laser light in each horizontal scanning line can be set in advance in a storage unit such as a lookup table in the image processing unit 36, for example.

  The second embodiment is an example in which the method for writing / reading image data to / from the frame memory 30 is different. FIG. 11A to FIG. 11D are schematic diagrams illustrating writing and reading of image data in the frame memory according to the second embodiment. FIGS. 11A and 11C show a case where image data is written to the frame memory, and FIGS. 11B and 11D show a case where image data is read from the frame memory. The numbers and arrows on the left of the frame memory 30 have the same meanings as in FIGS. 10 (a) to 10 (d) and will not be described. The configuration of the image projection apparatus is the same as that of the first embodiment, and a description thereof is omitted.

  As shown in FIG. 11A, when the image processing unit 36 writes the image data into the frame memory 30, the horizontal data is alternately written in order from the top. As shown in FIG. 11B, when the control unit 32 reads image data from the frame memory 30, the horizontal data is read in the same direction from left to right in order from the top. As shown in FIG. 11C, when the image processing unit 36 writes the image data in the frame memory 30 in the next frame, the image data is written as in FIG. 11A. As shown in FIG. 11D, when the control unit 32 reads the image data of the next frame from the frame memory 30, the horizontal data is read in the same direction from left to right in order from the bottom. As described above, when the image processing unit 36 writes the image data in the frame memory 30, the data is alternately written for each horizontal scanning line. When the control unit 32 reads image data from the frame memory 30, the data is read in the same direction for each horizontal scanning line. Also by the above, an image can be projected like the image projector of Example 1.

  As shown in FIGS. 10A to 10D of the first embodiment and FIGS. 11A to 11D of the second embodiment, the frame memory 30 is written with data corresponding to the horizontal scanning lines. It is possible to output in alternate directions with respect to the direction. Thus, the frame memory 30 can output horizontal data in response to the horizontal swing of the MEMS mirror 20.

  The third embodiment is an example in which the method for writing / reading image data to / from the frame memory 30 is different. 12A to 12D are schematic diagrams illustrating writing and reading of image data in the frame memory according to the third embodiment. 12A and 12C show a case where image data is written into the frame memory, and FIGS. 12B and 12D show a case where image data is read out from the frame memory. The numbers and arrows on the left of the frame memory 30 have the same meanings as in FIGS. 10 (a) to 10 (d) and will not be described. The configuration of the image projection apparatus is the same as that of the first embodiment, and a description thereof is omitted.

  The processing from FIG. 12A to FIG. 12C is the same as FIG. 10A to FIG. 10C of the first embodiment, and a description thereof will be omitted. As shown in FIG. 12D, when the control unit 32 reads the next frame, the image data is alternately read downward from the top horizontal data.

  FIG. 13 is a diagram illustrating a control signal with respect to time according to the third embodiment. As shown in FIG. 13, after the processing of one frame is completed, the MEMS mirror 20 is moved to the uppermost horizontal scanning line position. Thereafter, the same control signal as in the previous frame is used. As in the third embodiment, the MEMS mirror 20 can be moved to the uppermost horizontal scanning line position after the end of one frame without swinging up and down. As a result, as shown in FIG. 12D, the image data of the next frame can be read out as in FIG.

  The fourth embodiment is an example in which the image projection apparatus is placed vertically. FIG. 14 is a plan view of the image projection apparatus according to the fourth embodiment. As shown in FIG. 14, the image projector 10 may be used in an upright manner. In this case, the operation of the MEMS mirror 20 is the same as in the first embodiment, and in order to project the same image 14 as in FIG. 1B, the horizontal and vertical of the image data are switched.

  FIGS. 15A to 15D are schematic diagrams illustrating writing and reading of image data in the frame memory according to the fourth embodiment. 15A and 15C show a case where image data is written into the frame memory 30, and FIGS. 15B and 15D show a case where image data is read out from the frame memory 30. FIG. In FIG. 15A and FIG. 15C, the numbers shown on the left of the frame memory 30 indicate the order of writing the data in the image data. In FIG. 15B and FIG. 15D, the numbers shown below the frame memory 30 indicate the order in which the data of the horizontal scanning lines in the image data is read out. Arrows indicate the direction in which data is written or read. The configuration of the image projection apparatus is the same as that of the first embodiment, and a description thereof is omitted.

  As shown in FIGS. 15A and 15C, the image processing unit 36 writes the image data in the same manner as in FIGS. 10A and 10C of the first embodiment. Omitted. As shown in FIG. 15B, when the control unit 32 reads the image data, the horizontal data is alternately read from the left to the right in the vertical direction. As shown in FIG. 15D, when the control unit 32 reads the image data of the next frame, the horizontal data is alternately read from right to left in the vertical direction.

  As described above, the frame memory 30 can output the data corresponding to the horizontal scanning line in a direction orthogonal to the direction in which the data is written. As a result, as shown in FIG. 14, the image 14 can be projected with the image projection device 10 standing up. Similarly, even when the image projection apparatus 10 is arranged obliquely, the image 14 can be projected by outputting the data in the oblique direction in the frame memory 30 as data corresponding to the horizontal scanning line.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 10 Image projector 12 Projection light 14 Image 20 MEMS mirror 25 Laser emission part 30 Frame memory 32 Control part 34 VCO
60 read signal generation circuit 62 mixer 64 memory 66 waveform generation unit

Claims (10)

A projection unit that projects an image obliquely with respect to the projection light emission direction;
A frame memory that holds image data of the image and outputs the image data in synchronization with a read signal for each pixel data;
A laser emitting unit that emits laser light according to the output pixel data;
A MEMS mirror that scans the laser beam and emits it as projection light;
A control unit configured to make a horizontal scanning line far from the projection unit shorter than a near horizontal scanning line with an interval between the read signals;
An image projection apparatus comprising:   The control unit does not output the read signal in the vicinity of the turn of the swing of the MEMS mirror in the horizontal direction and does not output the read signal. The image projection apparatus according to claim 1, wherein the image projection apparatus is longer.   3. The image projection apparatus according to claim 1, wherein the control unit makes the interval between the read signals longer than the end of the same horizontal scanning line.   4. The control unit according to claim 1, wherein, in the same horizontal scanning line, the difference in the interval between the read signals between the center and the end is made smaller in the horizontal scanning line far from the projection unit than in the near horizontal scanning line. The image projection apparatus according to claim 1.   5. The image projection apparatus according to claim 1, wherein the control unit generates the read signal based on a horizontal synchronization signal of the MEMS mirror. 6.   6. The image projection apparatus according to claim 1, wherein the control unit includes a VCO, and generates the read signal using the VCO. 7. The controller is
A storage unit for storing waveform data of the control signal and the EN signal;
A waveform generation unit that generates the control signal and the EN signal based on waveform data of the control signal and the EN signal in synchronization with a horizontal synchronization signal of the MEMS mirror;
A VCO that changes a frequency of an oscillation signal to be output based on the control signal;
When the EN signal indicates activity, the oscillation signal is output as a read signal, and when the EN signal indicates inactivity, a mixer that does not output the oscillation signal;
The image projection apparatus according to claim 1, further comprising:   The image projection apparatus according to claim 1, wherein the frame memory outputs data in a direction alternate with respect to a direction in which data corresponding to the horizontal scanning line is written.   The image projection apparatus according to claim 1, wherein the frame memory outputs data corresponding to the horizontal scanning line in a direction orthogonal to a direction in which the data is written.   The image projection apparatus according to claim 1, wherein the image projection apparatus is installed on a plane and projects the image onto the plane.

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