JP2010175671A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which a scanning area is made as small as possible and the light quantity of a laser diode is controlled. <P>SOLUTION: The image forming apparatus includes a laser diode (LD); a photodiode (PD), which detects the light quantity of emitted laser light; a mirror which scans the laser light reflected on a light reflection part on a projection face; a mirror driving part for turn-driving the mirror; a laser output control part 104, which determines a driving current supplied to the LD by performing APC (automatic power control); and an image processing part 103 which controls the mirror driving part and the laser output control part 104 and displays an image on the basis of image information. The laser output control part 104 performs APC on the basis of the light quantity detected with the PD, the image processing part 103 makes a portion of drawing light replaced which is projected for drawing the image into APC light exclusively used for the APC. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art A projector that performs image drawing by scanning a laser beam using an optical polarizer using a MEMS (Micro Electro Mechanical System) technology is known. A laser diode (LD) used as a light source has a light output amount-current characteristic that fluctuates due to environmental changes such as temperature. Therefore, it is necessary to adjust the LD drive current to keep the light amount constant. For example, in the two-dimensional optical scanning device described in Patent Document 1, an area for projecting APC (Automatic Power Control) control light is provided outside the drawing area on the projection surface, and the amount of light detected there is used. APC control is performed.

JP 2003-5110 A

  However, in the method described in Patent Document 1, since it is necessary to perform optical scanning even outside the drawing area of the projection surface, it is necessary to vibrate the optical deflector beyond the drawing range, resulting in poor utilization efficiency. There's a problem.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of performing a light amount control of an LD with a scanning range as small as possible.

  An image forming apparatus according to the present invention includes a light source that emits a light beam, a light detection unit that detects a light amount of the light beam emitted from the light source, and a light reflection unit that is rotatable about a predetermined axis. A light deflector that scans the projection surface with the light beam reflected by the light source, a drive unit that rotationally drives the light deflector, a light source output controller that determines a drive current to be supplied to the light source, and a video source An image processing unit that controls the drive unit and the light source output control unit to display the image based on information on an image supplied from the image sensor, and the light source output control unit is detected by the light detection unit. Based on the obtained light amount, the drive current supplied to the light source is corrected so that there is no difference between the light amount based on the image information and the light amount of the actually emitted light beam, and the image processing unit Drawing light projected to draw A part of, so as to replace the control light beam is used for the correction of the driving current, thereby controlling the light source output control section.

  According to the present invention, since the control light beam is projected into the drawing area to correct the driving current of the light source, it is not necessary to perform optical scanning beyond the drawing area in order to project the control light beam. . For this reason, it is possible to correct the driving current of the light source by making the scanning range as small as possible. For this reason, the driving energy of the light deflection unit is reduced. Further, since it is not necessary to provide a control light beam projection area outside the drawing area, the drawing area can be widened. Therefore, a large image can be obtained even when the angle of view is wide and the projection distance is short.

The light source is a laser diode, for example.
Since a laser diode has a light output amount-current characteristic that fluctuates due to environmental changes such as temperature, it is necessary to correct the drive current, and the present invention can be applied effectively.

The image processing unit preferably replaces the drawing light beam with the control light beam when the luminance of the drawing light beam and the control light beam is close within a predetermined range at a certain drawing position. .
As a result, the control light beam projection position in the drawing area is replaced with a position having as close brightness as possible in the projected image, so that the control light beam can be made inconspicuous on the projection surface.

The image processing unit may randomly replace the drawing light beam with the control light beam in the entire drawing region.
Thereby, the burden of processing for determining the projection position of the control light beam can be eliminated, and the control light beam can be made inconspicuous on the projection surface.

Further, the image processing unit may replace the drawing light beam with the control light beam in a drawing region at an end portion in a horizontal scanning direction.
As a result, the burden of the process of determining the projection position of the control light beam can be eliminated, and the control light beam can be projected to a position with little influence on the image.

The image processing unit preferably replaces the drawing light beam with the control light beam at a plurality of drawing positions.
Thereby, the light source drive current can be corrected with higher accuracy.

In addition, the light source includes a light source that emits light beams of red, green, and blue colors, and the image processing unit outputs at least one control light beam for the light sources of all colors in one frame image. It is desirable to replace the light beam for drawing.
As a result, it is possible to correct the drive current without bias for the light sources of the respective colors.

The light source output control unit preferably corrects a drive current supplied to the light source based on a light amount of the control light beam projected in the immediately preceding frame image.
As a result, it is possible to perform current correction with higher accuracy in accordance with the current situation.

1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. It is a top view which shows the structure of a horizontal mirror. It is sectional drawing in the II-II line of FIG. It is a top view which shows the structure of a vertical mirror. It is a flowchart which shows the procedure of a drawing process and APC control operation | movement by the Example of this invention. It is a flowchart which shows the procedure which determines the optical projection position only for APC in 1 frame by the Example of this invention. FIG. 7A shows an example of a frame image before replacement of the APC dedicated light, and FIG. 7B shows a frame image after replacement of the APC dedicated light with respect to the image of FIG. It is a figure which shows an example. FIGS. 8A and 8B are diagrams illustrating examples of projection positions of APC dedicated light.

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

  FIG. 1 is a block diagram showing a configuration of an image forming apparatus 10 according to an embodiment of the present invention. As shown in the figure, the optical scanning device 10 includes a horizontal mirror (light deflection unit) 1a, a vertical mirror (light deflection unit) 1b, a horizontal mirror drive unit 101, a vertical mirror drive unit 102, an image processing unit 103, and laser output control. Unit (light source output control unit) 104, laser driver 105, laser diodes (light sources) 106G, 106B, 106R, dichroic mirrors 107G, 107B, 107R, and photodiodes (light detection units) 108G, 108B, 108R.

  The horizontal mirror 1a scans the laser beam sent from the dichroic mirrors 107G, 107B, and 107R in the horizontal direction. The vertical mirror 1b scans the laser beam reflected by the horizontal mirror 1a in the vertical direction. The horizontal mirror 1a is a resonant mirror formed by MEMS. Moreover, the vertical mirror 1b can be comprised by a galvanometer mirror, for example.

FIG. 2 is a plan view showing the configuration of the horizontal mirror 1a. 3 is a cross-sectional view taken along the line II-II in FIG.
The horizontal mirror 1 a includes a movable plate 11, a support frame 12, and a pair of elastic support portions 13 that support the movable plate 11 with respect to the support frame 12 so as to be torsionally rotated. The movable plate 11, the support frame 12, and the elastic support portion 13 are integrally formed, for example, by etching a silicon substrate.

  A reflective film 21 is formed on the movable plate 11. A magnet 22 is joined to the movable plate 11 on the side opposite to the reflective film 21. The magnet 22 is magnetized in a direction orthogonal to the axis A that is the rotation center axis of the movable plate 11 when the movable plate 11 is viewed in plan. That is, the magnet 22 has a pair of magnetic poles that are opposed to each other with the axis A and have different polarities. The support frame 12 is joined to the holder 20, and a coil 23 for driving the movable plate 11 is disposed on the holder 20.

  In the horizontal mirror 1 a, a voltage or current that periodically changes is supplied to the coil 23 by the drive signal generator 24. As a result, the coil 23 alternately generates a magnetic field directed upward (movable plate 11 side) and a magnetic field directed downward. As a result, one of the pair of magnetic poles of the magnet 22 approaches the coil 23 and the other magnetic pole moves away, and the movable plate 11 rotates around the A axis while twisting and deforming the elastic support portion 13. Be moved.

  FIG. 2 shows a drive-type vibrating mirror that uses an electromagnetic force between the magnet 22 and the coil 23. However, the present invention may adopt a method using electrostatic attraction or a method using piezoelectric elements. For example, in the case of a system using electrostatic attraction, the magnet 22 is not necessary, and one or a plurality of electrodes facing the movable plate 11 are installed instead of the coil 23. Then, by applying an alternating voltage that periodically changes between the movable plate 11 and the electrode, an electrostatic attractive force is applied between the movable plate 11 and the electrode, and the elastic support portion 13 is twisted and deformed. Then, the movable plate 11 is rotated around the A axis.

FIG. 4 is a plan view showing the configuration of the vertical mirror 1b. The vertical mirror 1 b includes a movable plate 14, a driving unit 16, and a connecting portion 15 that connects the movable plate 14 and the driving unit 16. A reflective film is formed on the movable plate 14. The connecting portion 15 has a structure for connecting the movable plate 14 and the driving means 16 so that the movable plate 14 can rotate around the B axis.
The driving means 16 can be a step motor, for example. Further, the vertical mirror 1b may be constituted by a galvano scanner. Further, the vertical mirror 1b may have the same configuration as the horizontal mirror 1a.

The horizontal mirror drive unit 101 rotates the horizontal mirror 1a. The vertical mirror driving unit 102 rotates the vertical mirror 1b. The horizontal mirror drive unit 101 includes a magnet 22, a coil 23, and a drive signal generation unit 24. As described above, the horizontal mirror drive unit 101 is configured to vibrate (rotate) the movable plate 11 with respect to the support frame 12 by applying a voltage or a current from the drive signal generation unit 24 to the coil 23. ing.
Further, the vertical mirror drive unit 102 includes a drive unit 16 and a drive signal generation unit 17, and the drive signal generation unit 17 has an appropriate voltage applied to the drive unit 16 so as to rotate the movable plate 14 of the vertical mirror 1b. Or give current.

  Based on image information sent from various video sources 200 such as a personal computer and a mobile phone, the image processing unit 103 displays a horizontal mirror driving unit 101, a vertical mirror driving unit 102, a laser output to display these images. The operation of the control unit 104 is controlled. The image processing circuit 103 converts the image information supplied from the video source 200 into drawing data, and based on position information obtained from position sensors 109a and 109b built in the horizontal mirror 1a and the vertical mirror 1b, respectively. Then, a drawing timing signal is generated.

  Based on the image information supplied from the image processing unit 103, the laser output control unit 104 determines the amount of current that the laser driver 105 supplies to the laser diodes 106G, 106B, and 106R, and corrects the amount of current using APC. . Thereby, the intensity of the laser light emitted from each light source is controlled.

  The amount of current correction by APC is based on the amount of light detected by the photodiodes 108G, 108B, 108R, and the difference between the amount of light based on image information supplied from the image processing unit 103 and the amount of laser light actually emitted. This is done by correcting the amount of current supplied to the laser diodes 106G, 106B, and 106R so as to eliminate the above. As will be described later, in this embodiment, APC is performed using the amount of light projected exclusively for APC.

  The laser diodes 106G, 106B, and 106R are light sources that emit laser beams. The laser diode 106G emits green laser light, the laser diode 106B emits blue laser light, and the laser diode 106R emits red laser light. However, a laser light source of 2 colors or less or 4 colors or more may be used.

  The dichroic mirrors 107G, 107B, and 107R are a dichroic mirror 107R that reflects red laser light from the laser diode 106R, a dichroic mirror 107B that reflects blue laser light and transmits red laser light, and a blue laser that reflects green laser light. A dichroic mirror 107G that transmits light and red laser light. By these three types of dichroic mirrors, the combined light of red laser light, blue laser light, and green laser light is incident on the horizontal mirror 1a.

  The photodiodes 108G, 108B, and 108R detect the amounts of red laser light, green laser light, and blue laser light that are transmitted without being reflected by the dichroic mirrors 107G, 107B, and 107R. The amount of light detected by the photodiodes 108G, 108B, and 108R is used in the APC process in the laser output control unit 104.

  Note that the configuration may be such that the light amounts of the respective colors are detected in a time-sharing manner by using one photodiode without providing the photodiodes 108G, 108B, and 108R for each color.

Next, a drawing process in the image forming apparatus 10 and an APC control method for the laser diodes 106G, 106B, and 106R will be described.
FIG. 5 is a flowchart showing the procedure of the drawing process and the APC control operation.
First, the image processing unit 103 acquires image information for one frame from the video source 200 and converts it into drawing data (step S501). The drawing data includes luminance information about light beams (light beams for drawing) projected from the laser diodes 106G, 106B, and 106R for each drawing position specified by the address. The drawing data is stored in a frame buffer (not shown).

  Next, the image processing unit 103 determines the projection position of the APC-dedicated light (control light beam) projected exclusively for APC in the frame (step S502). As described above, in this embodiment, APC is performed using the amount of APC-dedicated light detected by the photodiodes 108G, 108B, and 108R.

FIG. 6 is a flowchart showing a procedure for determining the APC dedicated light projection position in one frame. The image processing unit 103 determines whether or not each drawing position can be an APC dedicated light projection position by the procedure shown in FIG. 6, and determines the APC dedicated light projection position in the frame.
First, the image processing unit 103 acquires the luminance information of the first drawing position from the frame buffer (step S601).

  Next, the image processing unit 103 compares the acquired luminance information with the APC data (step S602). Here, the APC data is luminance information of light dedicated to APC. Since APC control is performed for each of the laser diodes 106G, 106B, and 106R, the light projected for APC is light projected from any one LD of the laser diodes 106G, 106B, and 106R.

  APC may be performed for all the laser diodes 106G, 106B, and 106R in one frame, or may be performed for one or two LDs. When APC is performed on one of R, G, and B LDs, only the APC-dedicated light emitted from the LD needs to be compared. On the other hand, when APC is performed on a plurality of LDs in one frame, the APC dedicated light emitted from each LD is compared.

  As a result of the comparison processing in step S602, if it is determined that the luminance information of the drawing data and the luminance information of the APC data are close within a predetermined range, the process proceeds to step S603, and the drawing position is set to the APC dedicated light projection. Determine the position. On the other hand, if it is not determined that the luminance information of the drawing data is close to the luminance information of the APC data, the process returns to step S601 to perform determination processing for the next drawing position.

  With respect to the criterion for determining whether or not the luminance information is close, it may be determined that the luminance information is close if it is almost the same, or may be determined to be close if it is within a certain luminance difference range. As will be described later, when the difference in luminance information is smaller, the APC-dedicated light can be made inconspicuous on the projection surface.

  As described above, when APC is performed on a plurality of LDs in one frame, if it is determined that the APC dedicated light of the LD of any color is close to the APC, Determine the dedicated light projection position.

After determining the APC dedicated light projection position in step S603, the image processing unit 103 determines in step S604 whether a predetermined number of APC dedicated light projection positions have been determined.
The APC dedicated light may be projected at only one place (one drawing position) per frame or at a plurality of places. In the case of a plurality of places, for example, the light projected from each of the laser diodes 106G, 106B, and 106R may be included. In addition, light from one LD may be projected to a plurality of locations. When a plurality of APC projections are performed in one frame, the image processing unit 103 determines whether or not the necessary projection positions have been secured.

  If it is determined in step S604 that a predetermined number of APC dedicated light projection positions have been determined, the APC dedicated light projection position determination process for the frame is terminated.

  In step S502 of FIG. 5, when the APC dedicated light projection position determination process for the frame is completed, the image processing unit 103 replaces the drawing data of the APC dedicated light projection position stored in the frame buffer with the APC data ( Step S503).

  The image processing unit 103 supplies the drawing data after the APC data is reflected to the laser output control unit 104 (step S504).

  Next, the laser output control unit 104 controls the amount of current that the laser driver 105 supplies to the laser diodes 106G, 106B, and 106R in order to draw a frame image based on the acquired drawing data (step S505).

  At this time, the laser output control unit 104 performs APC control in the current frame based on the amount of light detected by the photodiodes 108G, 108B, and 108R of the APC dedicated light projected in the previous frame. In the APC control, the laser driver is configured so that the actual light amount matches the light amount of the drawing data based on the difference between the actual light amount detected by the photodiodes 108G, 108B, and 108R in the previous frame and the light amount in the drawing data. The amount of current supplied from 105 to the laser diodes 106G, 106B, 106R is converted.

  The laser output control unit 104 determines the amount of current that the laser driver 105 supplies to the laser diodes 106G, 106B, and 106R based on the image information data reflecting the APC control, and the laser driver 105 performs the laser according to the determined amount of current. A frame image is drawn by driving the diodes 106G, 106B, and 106R (step S506).

  FIG. 7A shows an example of a frame image before replacement of the APC dedicated light, and FIG. 7B shows a frame image after replacement of the APC dedicated light with respect to the image of FIG. It is a figure which shows an example. In this example, APC dedicated light for all LD of R, G, and B is projected in one frame. In the figure, R1, G1, and B1 indicate drawing positions at which the APC dedicated light of the LD of each color of R, G, and B is projected, respectively. As shown in the figure, for the blue LD light, the APC dedicated light B1 is arranged in the sky near the color in the original image, and the red R1 is a tree trunk or ground (soil). The part, green G1, is placed on the leaves and grass parts.

  For example, in the luminance information of the APC dedicated light for the red laser diode 106R, only R has a predetermined luminance, and the luminances of G and B are zero. Therefore, since it is close to the luminance information of the portion (stem, soil, etc.) where the ratio of red is large on the image, this portion is determined as the APC dedicated light projection position of the red LD. In this way, since the APC dedicated light is projected onto an area having a close hue in the original image, the APC dedicated light can be made inconspicuous on the projection plane.

  As described above, according to the present embodiment, the APC dedicated light is projected into the drawing area and the APC control is performed. Therefore, in order to project the APC dedicated light, it is necessary to perform light scanning outside the drawing area. There is no. For this reason, APC control can be performed with the scanning range as small as possible. For this reason, the drive energy of the horizontal mirror 1a is reduced. Further, since it is not necessary to provide a projection area dedicated to APC outside the drawing area, the drawing area can be expanded. Therefore, a large image can be obtained even when the angle of view is wide and the projection distance is short.

  Further, since the APC dedicated light projection position in the drawing area is arranged as close as possible to the color and brightness in the projected image, the APC dedicated light can be made inconspicuous on the projection plane.

  Further, current correction with higher accuracy can be performed by performing APC based on the amount of light projected in the drawing area.

  In this embodiment, the APC-dedicated light is projected at a position close to the luminance information in the original image data. For example, as shown in FIG. It may be arranged. Further, as shown in FIG. 8B, the APC dedicated light may be projected together at the position of the horizontal drawing end.

The configuration of each part of the image forming apparatus 10 of the present embodiment can be replaced with an arbitrary configuration that exhibits the same function, and an arbitrary configuration can be added.
The image forming apparatus 10 according to the present exemplary embodiment includes the horizontal mirror 1a and the vertical mirror 1b. However, the image forming apparatus 10 includes one mirror that can rotate around two axes, and one mirror is perpendicular to the horizontal direction. It may be configured to scan in the direction.

  DESCRIPTION OF SYMBOLS 1a Horizontal mirror, 1b, Vertical mirror, Image forming apparatus 10, 11, 14 Movable plate, 12 Support frame, 13 Elastic support part, 15 Connection part, 16 Driving means, 20 Holder, 21 Reflection film, 22 Magnet, 23 Coil, 17, 24 Drive signal generation unit, 101 Horizontal mirror drive unit, 102 Vertical mirror drive unit, 103 Image processing unit, 104 Laser output control unit, 105 Laser driver, 106G, 106B, 106R Laser diode, 107G, 107B, 107R Dichroic mirror , 108G, 108B, 108R Photodiode, 109a, 109b Position sensor, 200 Video source

Claims (8)

A light source that emits a luminous flux;
A light detection unit for detecting a light amount of the light beam emitted from the light source;
A light deflecting unit configured to be rotatable about a predetermined axis and scanning the light flux reflected by the light reflecting unit on a projection surface;
A drive unit for rotationally driving the light deflection unit;
A light source output control unit for determining a drive current to be supplied to the light source;
An image processing unit that controls the drive unit and the light source output control unit to display the image based on information of an image supplied from a video source;
The light source output control unit is a drive that supplies the light source so that there is no difference between the light amount based on the image information and the light amount of the actually emitted light beam based on the light amount detected by the light detection unit. Correct the current,
The image processing unit controls the light source output control unit so as to replace a part of a drawing light beam projected to draw the image with a control light beam used for correcting the driving current. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the light source is a laser diode.   The image processing unit replaces the drawing light beam with the control light beam when the luminance of the drawing light beam and the control light beam is close within a predetermined range at a certain drawing position. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the image processing unit randomly replaces the drawing light beam with the control light beam in the entire drawing region.   The image forming apparatus according to claim 1, wherein the image processing unit replaces the drawing light beam with the control light beam in a drawing region at an end in a horizontal scanning direction.   6. The image forming apparatus according to claim 1, wherein the image processing unit replaces the drawing light beam with the control light beam at a plurality of drawing positions. The light source includes a light source that emits light beams of red, green, and blue colors,
7. The image processing unit according to claim 1, wherein at least one control light beam is replaced with the drawing light beam for all color light sources in one frame image. Image forming apparatus.   The light source output control unit corrects a drive current supplied to the light source based on a light amount of the control light beam projected in the previous frame image. The image forming apparatus according to any one of the above.

Images