JP4620905B2 - Two-dimensional optical scanning device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a two-dimensional optical scanning device that displays a two-dimensional image based on scanning output light obtained by directly modulating a light source based on image information in a first direction and a second direction.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a two-dimensional optical scanning device that displays a two-dimensional image based on scanning light scanned in the first direction also in the second direction has been proposed.
[0003]
FIG. 10 is a schematic diagram showing an example of the structure of a conventional two-dimensional optical scanning device (laser display device). In the case of such an apparatus, the light L emitted from the laser light source 1₀Is modulated in the optical modulator K and then scanned in the horizontal direction x by a first optical deflector (for example, a polygon mirror or a galvanometer mirror) A, and a second optical deflector (for example, a polygon mirror or a galvanometer mirror). Etc.) B is scanned in the vertical direction y.
[0004]
In this laser display device, since a gas laser is used as a light source, direct modulation cannot be performed in order to display a high resolution, and the modulation is performed by the optical modulator K. As the optical modulator K, an electro-optic modulator or an acousto-optic modulator is used. However, both of them are expensive and the apparatus itself becomes large, and both the apparatus and the screen are stationary display apparatuses. It was.
[0005]
[Problems to be solved by the invention]
When a semiconductor light emitting element such as a laser diode or LED is used as the light source of the apparatus as described above, light modulation can be performed directly by the light source itself (see FIG. 11). In the case of such an apparatus, since an optical modulator is not necessary, the size can be reduced and the cost can be reduced.
[0006]
By the way, when a laser diode, which is a semiconductor light emitting element, is used for the light source 1, it is affected by the droop characteristic, and even if the supplied current is constant (due to a temperature change accompanying internal heat generation). There is a problem that the light intensity changes. FIG. 13 is a diagram illustrating an example of droop characteristics appearing in the optical output when the laser diode is modulated with a certain pulse.
[0007]
In order to avoid such unstable output of light intensity, automatic light quantity control (APC control) has been conventionally performed. In other words, the light output of the laser diode is monitored by a light sensor (light detection unit), and the light output is increased when the monitor light amount decreases, and the light output is decreased when the monitor light amount increases.
[0008]
In general, a package of a laser diode with a PD (photodiode) has a structure as shown in FIG. Reference numerals 62 and 63 denote cases, reference numeral 64 denotes a lead wire, and reference numeral 65 denotes glass. In front of the laser diode 60, light for image display (reference symbol L₁The light for monitoring (reference L)_bThe light intensity is detected by the photodiode 61. Since a display device or the like needs to perform modulation with an arbitrary pattern in the display area, the light amount monitor timing is set when the image display light is scanned in the non-display area. However, during this monitoring, the monitoring light L_bIs irradiated not only toward the photodiode 61 but also as light L for image display.₁Is directed toward the screen. This is not a problem in an apparatus that projects onto a photosensitive member such as a laser beam printer, but when used as a laser display, there is a problem that it is a projection pattern that is unnecessary as a display and causes a reduction in the quality of a displayed image. This is not limited to the case of using a laser diode package with a PD, and the same problem occurs even when APC is performed by providing a light amount monitor unit outside.
[0009]
On the other hand, the optical deflector used in the above-described apparatus has a problem that the optical deflection characteristic is likely to change due to a temperature change or the like, and the display image is deteriorated. Therefore, in order to display a high-quality image, it is necessary to monitor and adjust the synchronization between the timing for modulating the image information and the driving timing of the optical deflection unit in real time. For the same reason, it is necessary to detect the drive timing and the cycle of the light deflection unit in real time. Since drive timing and period cannot be detected in the image display area, it is necessary to detect in the non-image area. However, in a scanning image display device, if detection is performed with an arbitrary modulation pattern in a non-image area, it is necessary to reduce the image display time, which causes a decrease in luminance and flickering, resulting in a decrease in display image quality. Bring.
[0010]
Conventionally, a laser beam printer that performs one-dimensional optical scanning modulates with a horizontal synchronizing signal for each scan, reflects the modulated light to a mirror, performs light detection, and determines the modulation start timing. However, since this method is a synchronous detection method specialized for one-dimensional optical scanning with a constant scanning speed, such as a polygon mirror, it is possible to modulate the driving timing when two-dimensional optical scanning is performed with an optical deflector. The modulation timing of a light source cannot be detected and synchronized in real time without affecting the display image.
[0011]
Therefore, the present invention prevents a projection pattern of APC from being projected onto the projection surface, and can easily detect the synchronization between the modulation timing and the light deflection unit drive timing without affecting the display image quality. Is intended to provide.
[0012]
[Means for Solving the Problems]
  The present invention has been made in view of the above circumstances, and includes a light source that directly modulates light based on image information, a first light deflector that scans light emitted from the light source in a first direction, A second optical deflector that scans light in a second direction, and displays a two-dimensional imageThe light source also emits light during a light source forced lighting period different from a period during which the two-dimensional image is displayed, and a first light detection unit is provided for detecting light from the light source during the light source forced lighting period. And controlling the drive current of the light source so that the output of the light detected by the first light detector is constant.In a two-dimensional optical scanning device,Provided between the second light deflector and the projection surface of the two-dimensional image, the light projected during the light source forced lighting period;Scanning areaTheA shielding part for shielding;A second part for detecting light projected on the scanning region, provided on the second light deflector side of the shielding part.A light detection unit;Based on the signal detected by the second light detector, synchronization between the light deflection timing of the first optical deflector and the light deflection timing of the second optical deflector, and the modulation timing of the light source and the second A signal processing circuit for controlling the first optical deflector, the second optical deflector, and the light source so as to be synchronized with the optical deflection timing of the optical deflector;It is provided with.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4.
[0014]
(1) First, the overall configuration of the two-dimensional optical scanning device according to the present invention will be described.
[0015]
The two-dimensional optical scanning device (image display device) according to the present invention displays a two-dimensional image based on scanning light scanned in the first direction x also in the second direction y ( Reference D in FIG.₁reference). In this specification, “scanning light in the first direction x” also means that light is scanned in one direction or reciprocating in the positive and negative directions of the first direction x, and “scanning light in the second direction y”. "Also means that light is scanned one side or back and forth in the positive and negative directions of the second direction y.
[0016]
In addition, the two-dimensional optical scanning device according to the present invention includes a light detection unit 2 so that the amount of light from the light source 1 can be detected.
[0017]
Further, the shielding unit 3 and the neutral density filter 4 may be arranged as will be described later.
[0018]
By the way, the light source 1 can directly modulate the output light. The light scanning in the first direction x may be performed by deflecting the light emitted from the light source 1 by the first optical deflector A, and the light scanning in the second direction y is emitted from the light source 1. The light may be deflected by the second optical deflector B. The first optical deflector A may perform high-speed scanning of light, and the second optical deflector B may perform low-speed scanning of light.
[0019]
(2) Next, the detailed configuration of each component will be described.
[0020]
By the way, the first optical deflector A may be driven by the first optical deflector drive circuit 5, and the second optical deflector B may be driven by the second optical deflector drive circuit 6.
[0021]
  Further, it is preferable that a modulation signal is input to the light source 1 from the light source modulation driving unit 8. Further, the light source 1 is preferably lit by a modulation signal for a certain period for each line scan, and the reference value of the drive current for the next scan is determined by monitoring the amount of light. An automatic light amount control (APC control) may be performed in which the light output is increased when the monitor light amount is decreased and the light output is decreased when the monitor light amount is increased. The monitoring of the amount of light at that time may be performed by a photodiode incorporated in the package of the light source 1. If the light source 1 is a laser diode or the like, the back beam from the chip may be monitored externally..
[0022]
The shielding unit 3 disposed between the light deflector and the projection surface, and the light detection unit 2 may be disposed on the light deflection unit side of the shielding unit 3. FIG. 2 shows a relationship diagram of the scanning light, the light detection unit 2 and the shielding unit 3 in this case. The light projection area projected in FIG. 2 by monitoring the light amount by forcibly lighting the light source 1 (APC control) will be referred to as an APC detection pattern. Since the APC detection pattern is modulated in synchronization with the modulation start signal 12 of the image information, the positional relationship with the image display signal is fixed. That is, for example, when the light source 1, the modulation timing, and the scanning timing of the light deflection unit cannot be synchronized and the displayed image is shifted to the right, the APC detection pattern is also shifted to the right. This detection pattern is a line-segment pattern displayed on the left or right side or both sides of the display image area. Further, the length of the light detection unit 2 in the second direction y is equal to the length of the scanning region G on the surface including the light detection unit in the low-speed scanning direction (that is, the length in the second direction y). Even in the case of the length, the length of the scanning region G on the surface including the light detection unit is made shorter than the length in the slow scanning direction (that is, the length in the second direction y), and the slow scanning direction of the image display region E It may be longer than the length (that is, the length in the second direction y). That is, the length of the APC light detection unit 2 needs to be shorter than the upper and lower scanning areas G and equal to or larger than the upper and lower widths of the image display area E. In addition, the APC light detection unit 2 may be disposed at a position corresponding to the APC detection pattern scanning region between the surfaces including the second light deflector B and the shielding unit 3, and the first light deflector A and the second light. It may be arranged at a position corresponding to the APC detection pattern scanning region between the deflectors B. Furthermore, as shown in FIG. 7, the mirror 30 may be arranged at a position corresponding to the APC detection pattern scanning region F described above, and the APC light detection unit 32 may be arranged at a position where all reflected light can be detected. Furthermore, a light detection unit may be provided in the light source 1. In addition, the APC light detection units 2 and 32 may have a shielding unit having a slit on the optical waveguide, or may have a plurality of light detection units arranged.
[0023]
The high-speed scanning by the first light deflection axis A is performed by sinusoidal driving (drive in which the displacement angle of the optical deflector is displaced sinusoidally with respect to the scanning time), and the light detection unit 2 is operated at high speed in the scanning region F. It is preferable to dispose them at both ends in the scanning direction x (see FIG. 8) and perform automatic light amount control for each one-line one-side scan by high-speed scanning.
[0024]
In the region where the modulated light deflected by the second optical deflector B is scanned, the shielding unit 3 is preferably arranged. The shielding unit 3 shields the scanning region in the light source forced lighting period for automatic light quantity control for controlling the driving current of the light source so that the light output of the light source directly modulated becomes constant. The shielding unit 3 includes the entire APC detection pattern scanning display area on the plane to which it belongs. In other words, the APC control monitors the laser that is forcibly lit (monitored by a PD or the like in the laser package) and determines the current value based on this information. The forced lit light from the APC is reflected on the projection surface. There is a shield 3 to prevent it. The shielding part 3 may be made of a material having a high light reflectance or a material having a low light reflectance (light absorbing material). The shielding unit 3 is preferably provided between the optical deflector and the screen. When an emission correction optical system described later is used (see reference numeral 20 in FIG. 5), the shielding unit 3 is provided on the lens surface of the emission correction optical system. A shielding part may be formed by partially depositing metal or the like. In addition, it is desirable that the shielding unit 3 is disposed in the vicinity of the second optical deflector B. According to this embodiment, if a direct modulation light source and an optical deflector are used, a portable projector can be realized, and a screen such as a wall or a desk can be used anywhere. In the case of such a configuration, the shielding part 3 is preferably provided around the light emitting part (specifically, an opening provided in the apparatus) from the apparatus. Thereby, the monitor light for APC control is shielded before reaching the screen.
[0025]
By the way, as the above-described neutral density filter, a reflective ND filter in which a chromium film is formed on a glass substrate, a cut filter that cuts off transmission of a specific wavelength, a polarizing plate, a polarizing filter, or the like may be used.
[0026]
When directly modulating a laser diode, which is a semiconductor light emitting element, at high speed, the drive current is biased to the vicinity of the threshold current, so that the semiconductor light emitting element emits a minute amount of light even when the modulation signal is turned off. For this reason, a light emitting area exists in a non-image area where nothing is originally projected, resulting in a reduction in quality of a display image as a display. This becomes a serious problem as the light quantity of the light source increases.
[0027]
Therefore, by using the neutral density filter 4, it is possible to improve by reducing minute light emission in the non-image display area to an extent that the observer does not care on an arbitrary projection surface. That is, the two-dimensional optical scanning image display device may have a neutral density filter arranged so as to include all the scanning areas of the non-image display time for performing modulation based on the control information. Further, the neutral density filter 4 may include a part or all of the image display region if the luminance unevenness on the projection surface or the decrease in luminance is a practical problem. This neutral density filter 4 is
-A surface on which a two-dimensional image is displayed by optical scanning (a surface on which a scanning beam as indicated by reference numeral 15 in FIG. 2 is projected), and disposed outside the image display area,
Even if it is arranged between the surface 15 and the optical deflectors A and B,
Even if it is arranged between the first optical deflector A and the second optical deflector B,
good. That is, even if all the neutral density filters 4 are arranged on the surface 15 or all the neutral density filters 4 are arranged between the surface 15 and the optical deflector, all the neutral density filters 4 are arranged in the first plane. Even if it is disposed between the optical deflector A and the second optical deflector B, a part of the neutral density filter 4 is disposed on the surface 15 and the other neutral density filter 4 is disposed on a portion other than the surface (for example, the surface). Between the optical deflector and between the optical deflector and the optical deflector). When an exit correction optical system described later is used (see reference numeral 20 in FIG. 5), it may be arranged on the lens surface of the exit correction optical system.
[0028]
As the light source 1, a type capable of directly modulating light, for example, a semiconductor light emitting element such as a laser diode or LED, an electroluminescence element such as an inorganic EL or organic EL, or the like may be used. When displaying a color image, a plurality of types of light sources having a plurality of wavelengths may be combined. In that case, when only one set of optical deflectors is used, it is necessary to use a means such as an optical system to convert the plurality of output lights into one light beam. When a plurality of light deflectors are used, a plurality of light beams may be incident on a plurality of mirrors. The light may be modulated by an intensity modulation method or a pulse width modulation method.
[0029]
Here, the intensity modulation method refers to a method of expressing the gradation of each dot by changing the light amount of the light source in an analog manner, and the pulse width modulation method does not change the light amount of the light source such as a laser. This is a method of expressing the gradation of each dot by changing the length (pulse width) of the lighting time while keeping it constant.
[0030]
Examples of the optical deflector include a galvanometer mirror and a resonant deflector. A galvano mirror may be used for both the first optical deflector A and the second optical deflector B, or a resonant optical deflector may be used. One optical deflector may be a galvanometer mirror, and the other optical deflector may be a resonant optical deflector. The first optical deflector A and the second optical deflector B may be formed separately or may be integrated. That is, the optical deflecting surface is swingably supported by two axes (orthogonal optical polarization axes), the optical scanning in the horizontal direction is performed by the first optical deflector A, and the vertical direction is performed by the second optical deflector B. It is preferable to perform the optical scanning.
[0031]
As these optical deflectors, those having a micromirror and manufactured using a semiconductor processing technique can be used. Here, the optical deflector will be supplemented. In recent years, an ultra-compact optical deflector (micromirror) having a mirror angle of several millimeters has been realized by silicon processing technology used for semiconductor materials (Japanese Patent Registration No. 0722314). FIG. 12 is a plan view showing an example of the structure of such an optical deflector (galvanomirror). Reference numeral 50 denotes a silicon substrate, reference numeral 51 denotes an upper glass substrate, and reference numeral 52 denotes a lower glass substrate. Reference numeral 53 denotes a movable plate, reference numeral 54 denotes a torsion bar, reference numeral 55 denotes a planar coil, reference numeral 56 denotes a total reflection mirror, reference numeral 57 denotes an electrode terminal, and reference numerals 60 to 63 denote permanent magnets. This optical deflector is of an electromagnetic type that is driven using a Lorentz force with a permanent magnet by passing a driving current through the planar coil 55. In addition, many electrostatic and piezoelectric micromirrors have been proposed, and these optical deflectors can be used.
[0032]
By using this micromirror and a directly modulated light source, a portable ultra-small projector can be realized. By applying the present invention to this projector, it is possible to configure an apparatus in which the shielding unit 3 and the light detection unit 2 are arranged in the scanning light emitting unit.
[0033]
As the first optical deflector A, a high-speed optical deflector capable of optical scanning at several tens of kHz to several tens of kHz is used, and as the second optical deflector B, optical scanning at several tens Hz to several tens of Hz is performed. A horizontal raster scan may be performed using a possible low-speed optical deflector. Conversely, if the first optical deflector A is a low-speed optical deflector and the second optical deflector B is a high-speed optical deflector, raster scanning is performed in the vertical direction, or the scanning frequency is other than the above combinations. Alternatively, a different scanning method such as Lissajous scanning may be used.
[0034]
As the second optical deflector B scans the optical path, the optical path changes between the second optical deflector B and the image display area E, and there is a risk that a focus shift will occur in the image display area E. In some cases, an exit correction optical system may be disposed in the optical path (see reference numeral 20 in FIG. 5) to correct the focus shift. The emission correction optical system in this case includes an f-θ lens that corrects a focus shift on the projection surface due to a change in the optical path between the optical deflector mirror and the scanning light projection surface by scanning, and a sine wave drive type. It is preferable to use a lens having a function such as an arc sine lens that corrects the distortion of the spot shape due to the change in the angular velocity of the optical deflector on the scanning light projection surface. This exit correction optical system can correct most of the scanning region, but cannot correct the peripheral part. Therefore, it is preferable to display the image in an area that can be corrected by the optical system.
[0035]
In the above description, the two-dimensional optical scanning image display device using the direct modulation light source 1 of the present invention has been described as a projection type image display device. However, the projection type image recording device, the scanning type drawing processing device of the configuration other than the above, Any device that directly modulates the light source, such as a scanning light detection device, can be used.
[0036]
(3) Next, a driving method of the two-dimensional optical scanning device will be described.
[0037]
Light L directly modulated by the light source 1 based on image information₁The light L₁Is deflected by the first optical deflector A and scanned in one direction or reciprocating in the first direction x. Since this light is also deflected by the second optical deflector B in the middle thereof, one side or reciprocating scanning is also performed in the second direction y, and as a result, a two-dimensional image is displayed.
[0038]
The amount of light is detected by the light amount monitor, and when the detected amount of light is less than the reference value, the amount of light is controlled to increase, and when the detected amount of light is greater than the reference value, the amount of light is controlled to decrease. It has become. It is to be noted that the detected light quantity is used to determine whether or not there is an abnormality. If it is determined that there is an abnormality, the safety device is activated to stop driving the two-dimensional optical scanning device itself, or an alarm is sounded or an alarm is generated. It is better to display.
[0039]
By the way, the light source 1 is lit or blinked while performing modulation during image scanning (t in FIG. 3).₂~ T₃) And turned off after image scanning (t in FIG.₄~ T₅After that, the light is forcibly turned on again to monitor the amount of light (t in the figure).₅~ T₆). The light amount detection by the light amount monitor unit is performed every one line scan in the first direction x (that is, every time one line scan by the high-speed optical deflector described above is completed). The forced lighting for light detection may be performed by inputting APC detection light emission pattern information to the light source 1 instead of image information.
[0040]
(4) Hereinafter, a method for driving the two-dimensional optical scanning device having the configuration shown in FIG. 1 will be described in detail with reference to FIG.
[0041]
FIG. 3A is a plan view showing a display state of an image, and FIG. 3B shows a case where a modulation start timing signal is output when a light beam is scanned along a line indicated by symbol H in FIG. (C) is a timing chart showing a modulation signal and the like when a light beam is scanned along a line indicated by symbol H in (a).
[0042]
Now, when a drive timing signal is sent from the digital processing signal circuit 7 to the first optical deflector drive circuit 5, the first optical deflector drive circuit 5 sends a drive signal to the first optical deflector A to transmit the light. The deflector A is driven. Thus, the light scanning point is C₀To C₁Move to. However, in this state, the light is not turned on, and one line of image information is transferred to the memory 9 during this period.
[0043]
And time t₁(Ie, the light scanning point is C₁At the time of reaching (1), a modulation start timing signal 12 is sent from the digital processing signal circuit 7 to the light source modulation drive unit 8 (see FIG. 3B). As a result, image information starts to be transferred from the memory 9 to the light source drive modulation unit 8, and a modulation signal based on the image information is sent from the light source drive modulation unit 8 to the light source 1. As a result, light directly modulated based on the image information is emitted from the light source 1, and the light is deflected by the first optical deflector A to be C₂→ C₃It is scanned towards. C₁~ C₄Since this is the image display area, the light source 1 is lit or blinked during this period (in order to display the characters shown in FIG.₂~ C₃Lit or flashing only during₄Thereafter, it is turned off.
[0044]
  Then, with the light turned off, the light scanning point is C₅When t₅Thus, the APC detection pattern information is input to the light source 1 and t₅~ T₆During this period, the light source 1 is forcibly turned on (when the input of the APC detection pattern information is completed, the light source is turned off). The light quantity of this light is detected by a light quantity monitor, and automatic light quantity control (APC) of modulated output light is performed based on the detection result. That is,Light intensity monitorDetection from APCsignalIs fed back to the digital signal processing circuit 7 and when the detected light amount is smaller than the reference value, the level of the current supplied to the light source 1 is increased during the next one-line scan so that the light amount is generally increased. On the other hand, when the detected light amount is larger than the reference value, the level of the current supplied to the light source 1 is lowered during the next one-line scan so that the light amount is generally reduced.
[0045]
Here, since the light scanned by the first optical deflector A is also deflected by the second optical deflector B in the middle thereof, a two-dimensional image is displayed as a result. For driving the second optical deflector B, a drive timing signal is sent from the digital processing signal circuit 7 to the second optical deflector drive circuit 6, and the second optical deflector drive circuit 6 sends the second optical deflector B to the second optical deflector B. This is achieved by sending a drive signal to.
[0046]
As described above, the APC detection pattern is projected as parallel lines at a certain distance from the display image. Here, the APC method and the image information transfer method are not limited to the above, and other methods may be used.
[0047]
(5) Next, the synchronization of the drive timing signal 10 of the first optical deflector and the drive timing signal 11 of the second optical deflector, and the modulation start signal 12 of the image information and the drive timing signal of the first optical deflector 10 will be described.
[0048]
The light deflection timing by the first light deflector, the light deflection timing by the second light deflector, and the modulation timing of the light source may be controlled based on the signal detected by the light detector.
[0049]
For example, in the case of a two-dimensional optical scanning device, when the optical deflectors are not synchronized, the display image is displaced, and when it is severe, the image appears to flow, resulting in a deterioration in the quality of the display image. However, since the driving cycle and driving timing of each optical deflector are not constant and vary depending on conditions such as temperature, it is not necessary to synchronize once. It is necessary to always ensure synchronization (synchronization between the drive timing signal 10 of the first optical deflector and the drive timing signal 11 of the second optical deflector) by monitoring. In addition, it is necessary to display the two-dimensional image in a correctable region of the emission correcting optical system, and from this point, it is necessary to ensure synchronization.
[0050]
In particular, in the case of the present embodiment, by maximizing the amount of light detected by the APC light detector 2, the drive timing signal 10 of the first optical deflector and the drive timing signal 11 of the second optical deflector Can be adjusted. At this time, since the vertical length of the APC detection pattern F and the APC light detection unit 2 is slightly shorter than the scanning region G, the first optical deflector A and the second optical deflector B must be synchronized. Since there are APC detection pattern portions that protrude from the top and bottom of the APC light detection portion 2, the amount of light detected is reduced as compared with the case where synchronization is established (see FIGS. 4A and 4B). Therefore, the relationship between the drive timing signal 10 of the first optical deflector and the drive timing signal 11 of the second optical deflector is adjusted so that the amount of light detected by the APC light detector 2 is maximized. At this time, the APC detection pattern F moves up and down on the display screen. When adjustment is performed so that the detected light amount is maximized, the APC detection pattern F that completely overlaps with the APC light detection unit 2 in the vertical and horizontal directions is obtained. A scanning display is performed (see FIGS. 4C and 4D).
[0051]
On the other hand, when the exit correction optical system is used, the display screen position is adjusted by the signal processing circuit 7 from the drive timing signal 10 of the first optical deflector in order to display the display image in the correction area of the exit correction optical system. It is necessary to generate a modulation start signal 12 for image information and to synchronize the modulation start signal 12 for image information and the drive timing signal 10 for the first optical deflector.
[0052]
In particular, in the case of the present embodiment, if the modulation start signal 12 of the image information and the drive timing signal 10 of the first optical deflector are not synchronized, APC detection that protrudes from the APC light detector 2 to the left and right is detected. Since the pattern portion exists, the detected light amount is reduced as compared with the case where synchronization is established (see FIGS. 4A and 4C). Therefore, the relationship between the modulation start signal 12 of the image information and the drive timing signal 10 of the first optical deflector is adjusted so that the amount of light detected by the APC light detection unit 2 is maximized. At this time, the APC detection pattern F moves to the left and right on the display screen. When adjustment is performed so that the detected light amount is maximized, the APC detection pattern F that completely overlaps the APC light detection unit 2 with respect to the left and right is obtained. A scanning display is performed (see FIGS. 4B and 4D). At this time, the APC detection pattern F may be scanned and displayed on the upper and lower portions of the APC light detection unit 2. However, if the APC light detection unit 2 does not protrude from the left and right, the APC light detection unit 2 is synchronized.
[0053]
The synchronization of these signals (that is, the synchronization of the drive timing signal 10 of the first optical deflector and the drive timing signal 11 of the second optical deflector, and the modulation start signal 12 of the image information and the first optical deflector). (Synchronization with the drive timing signal 10) may be performed based on the signal detected by the light detection unit 2.
[0054]
By always repeating the synchronization of these signals, the synchronization between the optical deflectors and the synchronization between the optical deflector and the display image can be maintained even if the scanning characteristic of the optical deflector is shifted. Further, since the deviation of the scanning characteristic of the optical deflector is mainly caused by a temperature change or the like, the characteristic changes gradually. For this reason, it is possible to cope with a synchronization shift only by adjusting each screen scan of several tens of Hz as in a television.
[0055]
Instead of adjusting the light amount detected by the APC light detection unit 2 to be maximized, the light amount detected by the APC light detection unit 2 in advance is predicted from the positional relationship between the APC light detection unit 2 and the APC detection pattern. Or you may measure and adjust so that it may become the light quantity. Further, the relationship between the drive timing signal 10 of the first optical deflector and the drive timing signal 11 of the second optical deflector, and the relationship between the modulation start signal 12 of the image information and the drive timing signal 10 of the first optical deflector. Measurement may be performed in advance, and scanning may start based on the relationship at the start of scanning.
[0056]
In addition, the relationship between the amount of light for one screen detected by the light amount monitor unit and the amount of light for one screen detected by the light detection unit 2 is measured in advance, and the amount of light detected by the light amount monitor unit is integrated. By calculating the total amount of light for the screen, the maximum amount of light detected by the light detection unit 2 may be converted, and the control amount may be calculated based on that.
[0057]
Next, the effect of this embodiment will be described.
[0058]
According to the present embodiment, the APC pattern is not displayed on the projection surface, and by using the APC pattern that is originally unnecessary, the light amount is detected by the APC light detection unit, so that the driving cycle of the optical deflector The drive timing and the modulation start timing could be easily synchronized. By arranging the APC light detection unit in a place other than the shielding unit, the device can be reduced in size and the degree of freedom in device design is increased. By disposing a plurality of APC light detection units, it is possible to improve the display quality of images by reciprocating scanning.
[0059]
In addition, according to the present embodiment, when using a directly modulated light source, various problems of APC that are necessary can be solved, and synchronization necessary for image display can be easily taken, and high image quality and high definition can be obtained. A display image can be obtained.
[0060]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
[0061]
Example 1
In this embodiment, a projection laser display (two-dimensional optical scanning device) D having the structure shown in FIG.₂And were driven by the method shown in FIG. Note that the same parts as those shown in FIG.
[0062]
In FIG. 5, reference numeral 20 denotes an exit correction optical system, and reference numeral 3 denotes a shielding part having an opening. The shield 3 is disposed between the second light deflector B and the projection plane, and the opening includes the entire image display scanning region on the plane of the shield 3. In the present embodiment, a monochromatic red laser diode was used as the light source 1. A galvano mirror is used for the first optical deflector A and the second optical deflector B, and the first optical deflector A is driven in a sawtooth wave at 10 kHz to perform horizontal scanning of light. Vertical scanning of light was performed by driving B with a sawtooth wave at 60 Hz. These galvanometer mirrors were not used with a temperature adjustment function in order to make the characteristic change remarkable, and were driven by open loop control. In this embodiment, a photodiode integrated with the laser diode and an ACP light detection unit on the shielding unit surface having an opening are used. The former is used for stabilizing the output light amount. The amount of light is monitored for each scan, and the latter is for detecting the scanning timing and cycle.
[0063]
Next, the driving method of the present embodiment will be described.
[0064]
Now, when a drive timing signal is sent from the digital processing signal circuit 7 to the first optical deflector drive circuit 5, the first optical deflector drive circuit 5 sends a drive signal to the first optical deflector A to transmit the light. The deflector A is driven. Thus, the light scanning point is C₀To C₁Move to. However, in this state, the light is not turned on, and one line of image information is transferred to the memory 9 during this period.
[0065]
When the modulation start timing signal 12 is output while the first optical deflector A is being driven (see FIG. 3B), image information starts to be transferred from the memory 9 to the signal processing circuit 7, and signal processing is performed. A modulation signal 21 is sent from the circuit 7 to the light source modulation driver 8, and modulation is started. As a result, light directly modulated based on the image information is emitted from the light source 1, and the light is deflected by the first optical deflector A to be C₂→ C₃Scanned towards C₄Thereafter, it is turned off.
[0066]
  Then, with the light turned off, the light scanning point is C₅When t₅Thus, the APC detection pattern information is input to the light source 1 and t₅~ T₆During this period, the light source 1 is forcibly turned on (when the input of the APC detection pattern information is completed, the light source is turned off). This light is detected by a photodiode integrated with the laser diode, and the amount of light is monitored. And APC light detection from photodiodesignalIs fed back to the digital signal processing circuit 7 and when the detected light amount is smaller than the reference value, the level of the current supplied to the light source 1 is increased during the next one-line scan so that the light amount is generally increased. On the other hand, when the detected light amount is larger than the reference value, the level of the current supplied to the light source 1 is lowered during the next one-line scan so that the light amount is generally reduced. The APC light detection part is on the shielding part surface having the opening, and is arranged so as to correspond to the scanning pattern position by the forced lighting of the APC when the synchronization is completely achieved.
[0067]
The relationship between the drive timing signal 10 of the first optical deflector and the drive timing signal 11 of the second optical deflector and the relationship between the modulation start signal 12 of the image information and the drive timing signal 10 of the first optical deflector are measured in advance. did. Scanning began based on the measured relationship.
[0068]
First, the relationship between the modulation start timing signal 12 of the image information and the drive timing signal 10 of the first optical deflector is adjusted so that the amount of light detected by the APC light detector 2 is maximized. If adjustment can be made so that the amount of light detected by the APC light detector 2 is maximized, the modulation start timing signal 12 of the image information and the drive timing 10 of the first optical deflector are synchronized. Next, the relationship between the drive timing signal 10 of the first optical deflector and the drive timing signal 11 of the second optical deflector is adjusted so that the amount of light detected by the APC light detector 2 is maximized. If the amount of light detected by the APC light detection unit 2 can be adjusted to the maximum, the modulation start timing signal 12 of the image information and the drive timing signal 11 of the second optical deflector can be synchronized. By finely adjusting these two adjustments for each screen scan, it was possible to display a completely synchronized image even if there was a change in the characteristics of the optical deflector.
[0069]
(Example 2)
In this embodiment, as shown in FIG. 6, the neutral density filter 4 is arranged on the surface including the shielding part 3. The neutral density filter 4 is disposed so as to surround the image display area E. Other configurations and driving methods are the same as those in the first embodiment.
[0070]
Using the apparatus having this configuration, synchronous detection using an APC detection pattern was performed in the same manner as in Example 1. As a result, the first and second optical deflectors can be synchronized with the modulation start timings 10, 11, and 12, and a still image can be displayed on a certain projection surface. Further, when a direct modulation light source in a non-image area on a certain projection surface is used, there is no specific minute light emission, and a high-quality image can be obtained.
[0071]
Example 3
In the present embodiment, the reflecting mirror 30 is disposed in the optical path, and the reflected light 31 is detected by the APC light detection unit 32. Other configurations and driving methods are the same as those in the first embodiment.
[0072]
Using the apparatus having this configuration, synchronous detection using an APC detection pattern was performed in the same manner as in Example 1. As a result, the first and second optical deflectors can be synchronized with the modulation start timings 10, 11, and 12, and a still image can be displayed on a certain projection surface. In addition, it is not necessary to install a light detection unit on the shielding unit 3 having an opening, and the degree of freedom of arrangement of the light detection unit is increased, so that the apparatus can be reduced in size.
[0073]
(Example 4)
In this embodiment, as shown in FIG. 8, two APC light detection units 2 and 2 are arranged on the surface including the shielding unit 3. Then, before and after the start of one line scanning, APC forced lighting is performed to detect light. The first optical deflector A is a sine wave driven galvanometer mirror. Further, the image display is drawn by the signal processing circuit using the reciprocal scanning. Other configurations and driving methods are the same as those in the first embodiment.
[0074]
Using the apparatus having this configuration, synchronous detection using an APC detection pattern was performed in the same manner as in Example 1. As a result, the first and second optical deflectors can be synchronized with the modulation start timings 10, 11, and 12, and a still image can be displayed on a certain projection surface. Further, when performing reciprocal scanning, since modulation is performed in both the positive scanning direction and the negative scanning direction, there is a problem in that the characteristics of the laser are likely to change, and there is a problem that the display image quality is deteriorated. Stable laser output light can be obtained, and high-quality and high-definition images can be obtained.
[0075]
(Example 5)
In this embodiment, as shown in FIG. 9, a wireless interface 40 and a video signal decoding device 41 are connected to the memory 9, and a video compressed signal 42 transferred by the wireless interface 40 is decoded by the video signal decoding device 41. The video signal 43 is changed and stored in the memory 9. The first optical deflector A and the second optical deflector B are sine-wave driven resonance micromirrors. Furthermore, the signal processing circuit 7 displays an image using reciprocal scanning. Other configurations and driving methods are the same as those in the first embodiment.
[0076]
Using the apparatus having this configuration, synchronous detection using an APC detection pattern was performed in the same manner as in Example 1. As a result, it was possible to synchronize between the first and second optical deflectors and the modulation start timings 10, 11, and 12, and to display images transferred by the wireless interface 40 with high image quality and high definition. .
[0077]
【The invention's effect】
  As explained above, according to the present invention, on the projection surfaceLight emitted from the light source during the forced light source periodWithout displaying the pattern, andLight emitted from the light source during the forced light source periodUsing patterns,SecondBy detecting the amount of light with the light detector, the driving cycle, driving timing and modulation start timing of the optical deflector could be easily synchronized.SecondBy arranging the light detection unit in a place other than the shielding unit, the device can be reduced in size, and the degree of freedom in device design is increased.SecondBy arranging a plurality of light detection units, it is possible to improve the display quality of an image by reciprocating scanning.
[0078]
In addition, according to the present invention, when a directly modulated light source is used, various problems of APC that are necessary can be solved, and synchronization necessary for image display can be easily taken, and a high-quality and high-definition display image can be obtained. Can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the overall configuration of a two-dimensional optical scanning device according to the present invention.
FIG. 2 is a plan view showing an APC detection unit and the like.
3A is a plan view showing a display state of an image, and FIG. 3B is a modulation start timing signal when a light beam is scanned along a line indicated by symbol H in FIG. FIG. 4C is a timing chart showing timing, and FIG. 4C is a timing chart showing a modulation signal and the like when a light beam is scanned along a line indicated by a symbol H in FIG.
FIG. 4 is a schematic diagram for explaining the coincidence between an APC detection pattern portion and a light detection portion.
FIG. 5 is a block diagram showing an overall configuration of a two-dimensional optical scanning device according to the present invention.
FIG. 6 is a plan view showing the shape of a neutral density filter or the like.
FIG. 7 is a block diagram showing the overall configuration of a two-dimensional optical scanning device according to the present invention.
FIG. 8 is a plan view for explaining an arrangement position of a light detection unit and the like.
FIG. 9 is a block diagram showing the overall configuration of a two-dimensional optical scanning device according to the present invention.
FIG. 10 is a schematic diagram showing an example of a conventional structure of a two-dimensional optical scanning device.
FIG. 11 is a block diagram showing the overall configuration of a two-dimensional optical scanning device according to the present invention.
FIG. 12 is a plan view showing an example of the structure of a conventional optical deflector (galvanomirror).
FIG. 13 is a diagram showing an example of droop characteristics appearing in the optical output when a laser diode is modulated with a certain pulse.
FIG. 14 is a sectional view showing a package structure of a laser diode.
[Explanation of symbols]
A First optical deflector
B Second optical deflector
D₁        Two-dimensional optical scanning device
D₂        Two-dimensional optical scanning device
D₃        Two-dimensional optical scanning device
D₄        Two-dimensional optical scanning device

Claims (17)

A light source that directly modulates light based on image information, a first optical deflector that scans light emitted from the light source in a first direction, a second optical deflector that scans the light in a second direction, The light source emits light during a light source forced lighting period different from the period during which the two-dimensional image is displayed, and the light from the light source is emitted during the light source forced lighting period. In the two-dimensional optical scanning device provided with the first light detection unit for detecting, and controlling the drive current of the light source so that the output of the light detected by the first light detection unit is constant ,
A shielding unit that is provided between the second light deflector and the projection surface of the two-dimensional image and shields a scanning region of light projected during the light source forced lighting period ;
A second light detection unit provided on the second light deflector side of the shielding unit for detecting light projected on the scanning region ;
Based on the signal detected by the second light detector, synchronization between the light deflection timing of the first optical deflector and the light deflection timing of the second optical deflector, and the modulation timing of the light source and the second A signal processing circuit for controlling the first optical deflector, the second optical deflector, and the light source so as to be synchronized with the optical deflection timing of the optical deflector;
A two-dimensional optical scanning device. The first optical deflector performs high-speed scanning of light, the second optical deflector performs low-speed scanning of light, and
2. The two-dimensional optical scanning device according to claim 1 , wherein light detection by the second light detection unit is performed for each one-line reciprocal scanning. The second light sensing unit has a length equal to the length of the slow scan direction of said scanning area, two-dimensional optical scanning apparatus according to claim 2, characterized in that. 3. The two-dimensional optical scanning according to claim 2 , wherein a length of the second light detection unit is shorter than a length of the scanning region in a low-speed scanning direction and is longer than a length of the image display region in a low-speed scanning direction. apparatus. The drive timing signal of the first optical deflector and the modulation start signal of the light source are adjusted so that the amount of light detected by the second light detection unit is maximized. two-dimensional optical scanning apparatus according to any one of 4. Wherein as the amount of light detected by the second light detecting unit becomes the maximum, to adjust a modulation start signal of the driving timing signal of the second optical deflector and the light source, it in claim 5, wherein The two-dimensional optical scanning device described. High-speed scanning by the first optical deflector is performed by sinusoidal driving,
The second light detection units are arranged at both ends in the high-speed scanning direction of the light scanning region,
The light detection by the second light detection unit is performed for each one-line one-side scan by high-speed scanning.
The two-dimensional optical scanning device according to any one of claims 2 to 4 , wherein the two-dimensional optical scanning device is provided. Two-dimensional optical scanning apparatus according to any one of claims 1 to 7 modulation mode of the light source is an intensity modulation method, characterized in that. Two-dimensional optical scanning apparatus according to any one of claims 1 to 7 modulation method of the light source is a pulse width modulation, characterized in that. It said light source is a laser diode, it two-dimensional optical scanning apparatus according to any one of claims 1 to 9, wherein. Wherein the light source is LED, and that the two-dimensional optical scanning apparatus according to any one of claims 1 to 9, wherein. It said light source is an organic EL, it two-dimensional optical scanning apparatus according to any one of claims 1 to 9, wherein. The two-dimensional optical scanning device according to any one of claims 1 to 12 , wherein the first and second optical deflectors are integrally formed. The said 1st and 2nd optical deflector has one optical deflection surface and two optical deflection axes which support this optical deflection surface so that rocking is possible, The Claim 13 characterized by the above-mentioned. Two-dimensional optical scanning device. Said first and second optical deflector has a micromirror formed at the semiconductor processing technology, it two-dimensional optical scanning apparatus according to any one of claims 1 to 14, wherein the. 16. The two-dimensional optical scanning device according to claim 1, wherein a neutral density filter is disposed outside an area where an image is displayed. The start of the safety device when the second based on the result of detection by the light detection unit is determined to be abnormal, it two-dimensional optical scanning apparatus according to any one of claims 1 to 16, wherein the.

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