JP5119627B2 - Image projection device - Google Patents

Description

  The present invention relates to an image projection apparatus having a one-dimensional light modulation device having a diffraction grating structure, for example.

  2. Description of the Related Art In image projection apparatuses such as projectors and printers, an apparatus that forms a two-dimensional image by projecting image light having one-dimensional image information onto an image forming unit while scanning with an optical scanning unit is known. As an apparatus for obtaining a one-dimensional image as described above, an optical modulation apparatus using a micro electro mechanical element having an optical function, that is, a so-called MEMS (Micro Electro Mechanical Systems) element has been proposed. Many of optical MEMS are used as an optical switching system in a broad sense that controls the traveling direction of light and turns on / off light. As one type of this optical switching system, there is known a diffraction grating type light modulation device using a so-called one-dimensional type light modulation element made of an optical MEMS element having a diffraction grating function (see, for example, Patent Documents 1 and 2). ).

  FIG. 13 is a schematic plan view of a main part of a diffraction grating type light modulation device 50 configured by arranging a plurality of diffraction grating type light modulation elements 11 in parallel. The light modulation element 11 includes a lower electrode 33 formed on the base 12 and ribbon-shaped first and second electrodes 31 and 32 arranged so as to straddle the lower electrode 33 in a bridge shape. Is done. The first and second electrodes 31 and 32 are arranged alternately, for example, and the first and second electrodes 31 and 32 and the lower electrode 33 are electrically insulated by a space between them. The first and second electrodes 31 and 32 are bent at both ends, for example, to form support portions 31A and 31B, 32A and 32B, and are supported by the base 12 via the support portions 31A and 31B, 32A and 32B. Configured.

  Here, as the base 12, for example, a substrate in which an insulating film is formed on a semiconductor substrate such as silicon (Si) or gallium arsenide (GaAs), an insulating substrate such as a quartz substrate or a glass substrate, or the like is used. The lower electrode 33 is formed of a polycrystalline silicon film doped with impurities, a metal film (polycrystalline W, Cr), or the like. The first and second electrodes 31 and 32 are composed of a base film made of an insulating material such as a silicon nitride film (SiN film) and an upper electrode made of a conductive material formed on the upper surface thereof. The In this case, the upper electrode 38 is made of, for example, Al having a high reflectance, and at least the central portion of the upper surface is configured as a reflection region.

As shown in FIG. 13, the first electrode 31 is connected to a bias electrode that is uniformly connected to a fixed potential, and the second electrode 32 is connected to a different control electrode for each diffraction grating type light modulation element 11. Connected. The bias electrode is common to the plurality of light modulation elements 11, and is grounded via a bias electrode terminal portion (not shown). The lower electrode 33 is also common to the plurality of light modulation elements 11, and is grounded via a lower electrode terminal portion (not shown). In FIG. 13, the extending direction of the electrodes 31 and 32 is indicated by an arrow X, and the width direction in which the electrodes 31 and 32 are arranged in parallel is indicated by an arrow Y. The first electrode 31 is not limited to the ground potential, and may be a predetermined potential, for example.
In this case, one set of the first and second electrodes 31 and 32 is formed of 6 pieces each, and a set of light modulation elements 11 is formed. The light modulation elements 11 are formed on a base (not shown), for example, 1080 sets, The first and second electrodes 31 and 32 are formed so as to be juxtaposed in the width direction indicated by the arrow Y, and a diffraction grating type light modulation device 50 is configured.

  FIG. 14 shows a schematic cross-sectional view of the first electrode 31 along the arrow BB in FIG. 13, and schematic cross-sections in the non-driven state and the driven state of the second electrode 32 along the arrow AA in FIG. 13. The figures are shown in FIGS. 15 and 16, respectively. FIG. 17 shows a partial schematic cross-sectional view of two adjacent light modulation elements 11 taken along the arrow CC in FIG. FIG. 17 shows a case where the left side of the adjacent light modulation element 11 is in the non-driven state and the right side is in the driven state. In the example shown in FIGS. 14-17, the support parts 31A and 31B of each electrode, and 32A and 32B show the example made into the structure which has a column shape and has a space | gap inside, but there are various other shapes of the support parts. The structure may be

When a voltage is applied to the second electrode 32 via the connection terminal portion and the control electrode, and a voltage is applied to the lower electrode 33 (actually, the lower electrode 33 is in the ground state), the second electrode 32 is applied. An electrostatic force (Coulomb force) is generated between the upper electrode 33 and the lower electrode 33. Then, due to the electrostatic force, the second electrode 32 is displaced downward toward the lower electrode 33. Based on the displacement of the second electrode 32, a reflection type diffraction grating is formed by the second electrode 32 and the first electrode 31.
Here, as shown in FIG. 17, the distance between the adjacent first electrodes 31 is d, and the wavelength of light (incident angle: θi) incident on the first and second electrodes 31 and 32 is λ. If the diffraction angle is θm,
d × [sin (θi) −sin (θm)] = m × λ
Can be expressed as Here, m is the order and takes values of 0, ± 1, ± 2,.
When the height difference Δh between the top surfaces of the first and second electrodes 31 and 32 is (λ / 4), the light intensity of the diffracted light becomes the maximum value. That is, by changing the voltage applied to the second electrode 32, the difference in height Δh between the top surfaces of the first and second electrodes 31 and 32 can be changed. As a result, the intensity of the diffracted light is increased. The gradation control can be performed by changing.

  As shown in a schematic cross-sectional configuration diagram in FIG. 18, the light modulation device 50 is configured such that the periphery of the light modulation device 50 is covered with a light transmission member 13 made of glass or the like on a base 12. In FIG. 18, the diffraction grating type light modulation element is not shown. The base 12 and the light transmissive member 13 are joined by a low melting point metal material layer 14.

Patent No. 3401250 Japanese Patent No. 3164824

In an image projection apparatus that projects light by modulating light from a light source in accordance with image information or the like using a diffraction grating type light modulation apparatus as described above, the first and first components constituting the diffraction grating are used. When variations occur in the manufacturing process of the electrode 2 and the like, diffracted light as designed is not generated with respect to the driving power. For this reason, when the one-dimensional image light modulated by the light modulation device is projected on a screen by a scanning mirror or the like, there is a problem that horizontal stripes appear in the image. For example, it is very difficult to manufacture a diffraction grating having, for example, 1080 pairs × 6 electrode structures as described above uniformly and with high productivity.
In particular, when a polygon mirror is used as a scanning unit, a scanned image may move up and down from frame to frame due to surface tilt variation of the mirror surface. When such vertical movement occurs, the vertical resolution deteriorates. In order to display horizontally long images at a high frame rate, it is advantageous to use a polygon mirror as a scanning means. However, it is difficult to manufacture each mirror surface of the polygon mirror with high accuracy at present, and the manufacturing cost is extremely high. There is a problem of increasing it. For this reason, it is required to correct the error of the projection position by such scanning means.

  In view of the above problems, the present invention reduces image streaks caused by manufacturing variations of a one-dimensional type light modulation device and corrects projection position errors caused by scanning means, thereby enabling good image display. It is to do.

In order to solve the above problems, an image projection apparatus according to the present invention includes a modulation optical unit including a one-dimensional light modulation device, a projection optical unit, a scanning optical unit, and a signal processing unit. The scanning optical unit includes a main scanning optical unit that scans in a direction substantially orthogonal to the longitudinal direction of the one-dimensional light modulation device, and a sub-scanning optical unit that scans in the longitudinal direction of the one-dimensional light modulation device . Sub scanning optical unit changes the optical axis angle in the longitudinal direction of the angle of an integral multiple amount corresponding 1-dimensional light modulation apparatus corresponding to one pixel interval in the frame of the image formed by the main scanning optical unit. Further, the signal processing unit, in response to movement of the number of pixels corresponding to the optical axis angle is varied, that to compensate for the image signal to be input to the one-dimensional light modulation apparatus.

As described above, in the image projection apparatus of the present invention, the scanning optical unit is provided with the main scanning optical unit and the sub scanning optical unit that scan light in directions orthogonal to each other. By providing two scanning optical units in this way, a one-dimensional image can be moved up and down in the one-dimensional direction, for example, finely oscillated. Therefore, for example, in a one-dimensional type light modulation device, even if there are variations in dimensions and the like that occur in the manufacturing process in some of the components such as diffraction gratings, bright spots or dark spots caused by the defects are For example, it can be averaged by the vertical movement of the one-dimensional image by the sub-scanning optical unit, and can be suppressed from being visually recognized as a streak, that is, the streak can be reduced.
Further, by compensating the image signal in advance by the signal processing unit in response to such movements such as minute vibrations, the image can be displayed favorably without being disturbed.

  According to the present invention, image streaking caused by manufacturing variations of a one-dimensional light modulation device is reduced, and the vertical resolution deterioration of the image is suppressed by correcting the error of the projection position by the main scanning optical unit. Therefore, it is possible to display a good image.

Examples of the best mode for carrying out the present invention will be described below, but the present invention is not limited to the following examples.
FIG. 1 is a schematic configuration diagram of an example of an image projection apparatus according to an embodiment of the present invention. As shown in FIG. 1, the image projection apparatus includes a modulation optical unit 110, a projection optical unit 120, and a scanning optical unit 130. The modulation optical unit 110 includes a light source, an illumination optical system, a light modulation device, and color synthesis. And at least a light selector. In this case, for example, light sources 100R, 100G, and 100B that emit red, green, and blue laser lights (indicated by arrows LR, LG, and LB) that are the three primary colors of light are provided. Each color light emitted from these light sources 100R, 100G, and 100B passes through the illumination optical systems 101R, 101G, and 101B, and then bends an optical path by a mirror (not shown) to form a one-dimensional light modulator 102R, 102G, and 102B. Is incident on. Based on the signals SR, SG, and SB from the signal processing unit 200, the light modulated by reflection or diffraction in these light modulation devices is similarly bent in the optical path by a mirror (not shown), and a color synthesis unit 104 such as an L-shaped prism. And is combined into one light beam in the color composition unit 104 and emitted as, for example, light of three primary colors LT. A light selector 105, a so-called spatial filter, is disposed on the optical path of the combined light LT, and one-dimensional image light is selected here. A projection lens 106, a sub-scanning optical unit 107 including a rotating mirror, and a main-scanning optical unit 108 including a galvano mirror and a polygon mirror are disposed on the selected optical path of the image light. The unit 130 is configured. Then, the one-dimensional image light is scanned as indicated by arrows L1, L2, L3,... By the rotation indicated by the arrow r of the main scanning optical unit 108, and the arrow on the image generation surface 150S on the surface of the screen 150 or the like. Images are sequentially projected in the direction indicated by S.

Here, as the light modulation devices 102R, 102G, and 102B, the diffraction grating type light modulation device of the conventional configuration described with reference to FIGS. 13 to 18 described above can be used. By using cylindrical lenses in the illumination optical systems 101R, 101G, and 101B that irradiate light to the light modulation device, the light is condensed to a predetermined spot size in the extending direction of each electrode indicated by an arrow X in FIG. The collimated light collimated to a predetermined width in the width direction of the electrode indicated by the orthogonal arrow Y can be efficiently applied to the reflection region of the electrodes constituting the diffraction gratings of the light modulation devices 101R, 101G, and 101B.
In addition, the light selection unit 105 is configured as, for example, an Offner optical system, and one light beam that has passed through, for example, a Schlieren filter 105S as a spatial filter is screened by the projection lens 106 via the sub-scanning optical unit 107 and the main scanning optical unit 108. The image is formed on the top. Note that the schlieren filter 105S is disposed, for example, in the Fourier plane.

In such an image projection apparatus, when the second electrode 32 which is the movable electrode shown in FIGS. 13 to 17 is in the state shown on the left side of FIGS. The light reflected by the top surfaces of the second electrodes 31 and 32 is blocked by the schlieren filter 105S.
On the other hand, when the second electrode 32 is driven in the state shown on the right side of FIGS. 16 and 17, ± first order (m = ±) diffracted by the diffraction grating composed of the first and second 31 and 32. The diffracted light of 1) passes through the schlieren filter 105S.
With such a configuration, on / off of light to be projected onto the screen 150 can be controlled. As described above, the height difference Δh between the top surface of the second electrode 32 and the top surface of the first electrode 31 can be changed by changing the voltage applied to the second electrode 32. As a result, gradation control can be performed by changing the intensity of diffracted light.

In the diffraction grating type light modulation device, the first and second electrodes 31 and 32 have a very small size and a fine degree of modulation with respect to driving power, so that high resolution, high-speed switching operation, and wide bandwidth display are possible. It becomes possible. Furthermore, since it can be operated with a low applied voltage, it is possible to realize an image projection apparatus with a very small size. Such an image projection apparatus scans a one-dimensional image by the main scanning optical unit 108 as compared with a normal two-dimensional image display apparatus, for example, a projection display apparatus using a liquid crystal panel or the like. Smooth and natural image expression is possible. Moreover, the three primary colors of red, green, and blue lasers are used as light sources, and these lights are mixed, so that an extremely wide and natural color reproduction range image can be expressed. Has display performance.
As another one-dimensional light modulation device, for example, a light-emitting element with a light modulation function such as an array liquid crystal element, an array LD (laser diode), or an array LED (light-emitting diode) is used instead of the light source and the light modulation device. It is also possible.

FIG. 2 is a schematic perspective configuration diagram of an image projection apparatus according to an embodiment of the present invention. A two-dimensional image is scanned and projected on a screen 150 using such a diffraction grating type light modulation apparatus. Fig. 6 schematically shows how an image is displayed. In FIG. 2, parts corresponding to those in FIG. In the modulation optical unit 110 in FIG. 2, only one optical path is representative of the optical paths before combining each color such as red, green, and blue.
In this case, light emitted from the light source 100 (corresponding to the light sources 100R, 100G, and 100B of three primary colors of red, green, and blue, not shown) is predetermined by the illumination optical system 101 (corresponding to 101R, 101G, and 101B). The light beam is shaped into a shaped light beam and applied to the light modulation device 102 (corresponding to 102R, 102G, and 102B). Light modulated in accordance with information such as an image by the light modulation device 102 is combined by a color combining unit (not shown) and is incident on the light selection unit 105 and the projection lens 106. A one-dimensional image 46 may be formed at a position before incidence of the projection lens 106, and a light scattering element so-called diffuser may be disposed here.

  The light emitted from the projection lens 106 is first incident on the sub-scanning optical unit 107 in this example. In the illustrated example, a rotating mirror such as a galvanometer mirror is rotated as indicated by an arrow r1, for example, to move in the longitudinal direction of the one-dimensional image, that is, the longitudinal direction of the one-dimensional light modulator. Thereafter, the main scanning optical unit 108 scans light in a direction substantially orthogonal to the scanning direction of the sub-scanning optical unit 107. In the illustrated example, a rotating mirror such as a galvano mirror is rotated as indicated by an arrow r2, for example, to be scanned as indicated by an arrow S on an image generation surface 150S such as a screen 150, that is, by arrows L1, L2, ... Two-dimensional image 47 is generated by scanning and projecting as indicated by Ln−1 and Ln. The image display area on which the two-dimensional image 47 is projected on the image generation surface 150S such as the screen 150 is indicated by hatching, and non-display areas 48a and 48b exist on both sides thereof.

  As a configuration example of the sub-scanning optical unit 107, for example, in addition to a method of using motors such as a galvano motor and a step motor, one side of the mirror 41 is hinged as shown in a schematic configuration example of FIG. The fulcrum 42 is fixed, and for example, one end of the mirror 41 is moved as indicated by an arrow r11 by a vibrating element 43 such as a piezo element or a linear motor, thereby scanning with the light reflection angle adjusted. it can.

In such a configuration, the sub-scanning optical unit 107 is provided, and the one-dimensional image light output from the modulation optical unit 110 is substantially orthogonal to the scanning direction on the screen 150 by the main scanning optical unit 108, that is, the one-dimensional image. Move in the longitudinal direction (up and down direction of the image). In the present invention, the image signals SR, SG, and SB input to the light modulation devices 102R, 102G, and 102B are moved in the scanning direction by the sub-scanning optical unit 107, that is, in the direction opposite to the vertical movement. That is, the signal processor 200 compensates for this vertical movement.
For example, when the optical axis is moved up and down by one pixel by rotating the mirror 41 shown in FIG. 3 or the like, the image projected on the image generation surface 150S also moves by one pixel if it is left as it is. As described above, the image signal input to the light modulation device 102 is shifted by one pixel in the reverse direction and modulated.

Next, the operation mode of the sub-scanning optical unit 107 will be described in detail.
In order to make the streaks in the image less noticeable, it is desirable to average as many pixels as possible. For this purpose, the projection position of the image may be periodically moved by the sub-scanning optical unit 107 as shown in FIG. In FIG. 4, the horizontal axis represents time in units of one frame, and the vertical axis represents positions on the image generation surface 150S in units of one pixel width. In this example, 4 pixels are moved to one side and 4 pixels are moved to the other side, so that the pixels for the original position can be added to average 9 pixels.
As shown in FIG. 4, the sub-scanning optical unit 107 is stopped at a certain position during drawing of an image of one frame, and the time during which the image signal is not input to the light modulation device 102, that is, the non-display area in FIG. If the movement of one pixel of the sub-scanning optical unit 107 is completed during the time when the main scanning optical unit 108 scans 48a and 48b, the image, that is, the two-dimensional image 47 on the screen 150 in FIG. There is no impact.
When the image signal is 120 frames per second, that is, about 8 milliseconds per frame, the time during which the image signal is not input to the light modulator 102 is about 2 milliseconds. During this period, it is desirable to complete the movement of about 17 μm for one pixel. Although this level of movement speed depends on the projection distance, the sub-scanning optical unit 107 can be sufficiently used with a piezo element, a linear motor, or the like, has a low load, and can operate sufficiently.

  The image signals input to the respective light modulation elements of the light modulation device are reversed so that the image on the screen 150 does not move in the vertical direction corresponding to the change width of the movement angle per time in the sub-scanning optical unit 107. Move to. That is, for example, in the time band in which the sub-scanning optical unit 107 moves to an upward angle corresponding to one pixel, the image signals SR, SG, and SB simultaneously input to the one-dimensional light modulator 102 are reversed by one pixel. The signal processing unit 200 performs processing for compensating the signal input to the light modulation device 102 so that the signal is displayed in the direction, that is, moved downward.

As an example, the above-described one-dimensional light modulation device having the diffraction grating structure includes, for example, 1088 one-dimensional light modulation elements, and projects and scans a one-dimensional image of 1080 pixels in the vertical direction. An example of displaying a two-dimensional image will be described. In this case, eight one-dimensional light modulation elements can be used as a margin for movement. FIG. 5 schematically shows how the image signal allocation position is moved to each light modulation element in such a configuration.
As shown in FIG. 5, in this case, for each frame F1, F2, F3,..., The image signal P1 input to each of the light modulation elements M1, M2, M3,... M1085, M1086, M1087, M1088, P2,..., P1079, P1080 are assigned so as to move sequentially by one pixel. In the example of FIG. 5, after moving one pixel at a time up to the eighth frame, the ninth frame is moved backward by eight pixels to return to the original allocation position. By assigning such signals and simultaneously changing the optical axis by an angle corresponding to one pixel up and down by the sub-scanning optical unit 107 shown in FIGS. 1 and 2 on the image generation surface 150S. Is displayed well without shifting the arrangement position of each pixel, that is, without shifting the image up and down. In this case, similarly to the example described in FIG. 4 described above, it is possible to perform averaging for nine pixels including the image signal at the original position.
FIG. 5 shows an example in which the signal allocation position is shifted by one pixel during 8 frames and then returned to the original allocation position in the 9th frame, but in the reverse direction from the 10th frame to the 17th frame. It is also possible to move the assigned position back by one pixel at a time.
Note that the number of light modulation elements provided in the light modulation device and the number of pixels of a one-dimensional image to be displayed are not limited to this example.

  Using the image projection apparatus as described above, the contrast on the pixel generation surface 150S of the screen 150 was measured while changing the average number of pixels from 1 to 9 pixels. The result is shown in FIG. The contrast, which was 1500: 1 at a pixel, improved to about 6000: 1 due to the averaging effect.

  As the sub-scanning optical unit 107, in addition to the configuration example shown in FIG. 3 described above, although not shown, for example, a mechanism that translates the lens in the longitudinal direction of a one-dimensional light modulation device, or an example thereof is shown in FIG. As shown in the schematic configuration diagram of FIG. 1, the transmission parallel plate 44 is composed of a direction parallel to both the longitudinal direction and the optical axis direction of the one-dimensional light modulator (perpendicular to the paper surface of FIG. 7). The direction of the optical axis indicated by the arrow L12 can be changed to the direction indicated by the arrow L12 ′ by performing a rotational movement as indicated by the arrow r12 with the rotation direction as the rotation axis. Further, for example, as shown in the schematic configuration diagram of FIG. 8, the wedge plate 45 is configured, and the wedge plate 45 is translated in the optical axis direction as indicated by an arrow r13, whereby the optical axis direction indicated by the arrow L13 is indicated by the arrow. It can also be set as the structure changed to the optical axis direction shown by L13 '.

In the image projection apparatus of the present invention, there is no essential limitation on the number of times the image is moved per second by the sub-scanning optical unit 107, but in order to prevent the movement of streaks from being detected by human eyes, it is 60 times or more. It is preferable that For example, if it is an image signal of 120 frames / second, it may be moved 120 times per second.
Further, although there is no essential limitation on the movement width of the image per movement, when the vibration element in FIG. 3 described above or the rotational movement mechanism such as the example shown in FIG. In order to reduce the load, it is preferable that the width is one pixel. That is, in order to reduce the load on a driving unit such as a motor that drives the sub-scanning optical unit 107, for example, as shown in FIG. Next, it is desirable to perform averaging that repeats scanning for moving one pixel continuously in the reverse direction.
Furthermore, there is no essential limitation on the number of pixels to be averaged, but the streak reduction effect is greater when averaging as many pixels as possible.
In addition, by increasing the movement width per one time to about several pixels, for example, the sub-scanning optical unit 107 can randomly move the pixels up and down. In this case, since the periodicity is lost, the horizontal movement is eliminated. It is possible to suppress or avoid flickering periodicity due to streaking averaging, to more reliably reduce streaking, and to display a better image.

A polygon mirror can also be used as the main scanning optical unit 108 in the image projection apparatus of the present invention. When a polygon mirror is used, a horizontally long image can be displayed more favorably. On the other hand, there is a risk of increasing the cost to accurately manufacture the verticality of each mirror surface of the polygon mirror. If the cost is reduced to some extent, each mirror surface of the polygon mirror is tilted, that is, the image is translated vertically on the image generation surface for each image frame corresponding to each mirror surface due to this surface tilt accuracy error. There is a fear.
On the other hand, in the image projection apparatus of the present invention, since the sub-scanning optical unit that scans the image up and down is provided, it is preferable to control the sub-scanning optical unit so as to cancel the vertical movement of the image. An image can be displayed on the screen.

FIG. 9 shows a schematic perspective configuration diagram of an example of an image projection apparatus according to an embodiment of the present invention using such a polygon mirror. In this example, the sub-scanning optical unit is driven in accordance with the rotation angle of the polygon mirror so that the deflection of the one-dimensional image due to the surface tilt accuracy error of each mirror surface of the polygon mirror is corrected in advance. 9, parts corresponding to those in FIG. 1 and FIG.
That is, in this case, as shown in FIG. 9, the surface tilt accuracy error by the polygon mirror 108A is measured in advance, the rotation angle of the polygon mirror 108A is detected by the rotation angle detection unit 64, and the angle signal Sa is generated by the sub-scanning optical unit. This is output to the sub-scanning optical unit drive control unit 62 that drives 107. Then, in response to the surface tilt accuracy error of the polygon mirror 108A, a drive signal Sm is output to a drive unit (not shown) of the sub-scanning optical unit 107 so as to deflect the image light.
In this way, the light that has been compensated for the surface tilt accuracy error in advance by the sub-scanning optical unit 107 and is deflected in the vertical direction is reflected by the polygon mirror 108A, and is projected onto the screen 150, for example, as line-shaped image light. The image is displayed by scanning as indicated by S. The polygon mirror 108A is rotated about the rotation axis c as indicated by an arrow r2.
By adopting such a configuration, it is possible to significantly relax the specifications of the surface tilt accuracy of the polygon mirror 108A, and as a result, it is possible to reduce the cost.

As described above, FIG. 10 shows a schematic configuration diagram of an example of an image projection apparatus configured to project onto a cylindrical screen when a polygon mirror is used as the main scanning optical unit. 10, parts corresponding to those in FIG. 1, FIG. 2, and FIG.
Conventionally, when an image is projected onto a cylindrical screen, for example, when a two-dimensional spatial light modulator such as a liquid crystal panel or DMD (Digital Micro-mirror Device) is used, the four corners are distorted. It was difficult to project clear images on all areas of the screen, and the screen could only be projected as a polyhedral configuration. However, by using the image projection apparatus of the present invention, it is possible to display an image having excellent image quality without any breaks even in a horizontally long image and without distortion up to the four corners of the cylindrical screen. By using a cylindrical surface screen, it is possible to easily obtain a wide viewing angle as compared with the case of using a flat screen, and even in the case of a wide viewing angle, without increasing the image projection device, It becomes possible to project with high definition.
In the above-described example, a configuration called a so-called post-projection in which the scanning optical unit 130 is arranged after the projection optical unit is used. However, a region through which light passes is only a so-called core portion of the projection lens 106. Therefore, the deterioration of the four corners of the screen 150 is small. Therefore, by adopting the above-described configuration, it is possible to project an image with clear image quality up to the four corners of the screen 150.

Next, in the image projection apparatus of the present invention, for each frame of the image formed by the main scanning optical unit, scanning is performed by the sub-scanning optical unit with a movement amount corresponding to half of the one-pixel interval of the light modulation device, That is, a description will be given of an embodiment in which the projection image is vertically moved by half a pixel for each frame in the vertical direction.
In this case, for example, the mirror 41 shown in FIG. 3 corresponds to a half of the spacing between the pixels arranged in a line by the light modulation device by the sub-scanning optical unit. Configure to tilt. This inclination angle is selected according to the distance between the pixels of the light modulator and the distance from the light modulator to the image generation surface such as a screen via the projection lens.
In such a configuration, as shown in FIG. 11, the image light LA scanned upward on the screen and the image light LB scanned downward by the sub-scanning optical unit are halfway in the vertical direction of the screen. Displayed with a pixel offset. As a result, interlaced display is possible, and the resolution can be improved almost twice.

  FIG. 12 schematically shows pixels displayed in each scanning direction in this case. Each pixel A1, A2, A3,... Of image light in the upward scanning direction shown in FIG. 11 corresponds to A1 ′, A2 ′, A3 ′,. Changes and is displayed. The image light B1, B2, B3,... In the downward scanning direction in the next frame is displayed shifted downward by half a pixel, which is almost half of the interval between the pixels, in this case the pixels A1 and A2. The

  In the above-described diffraction grating type light modulation element such as the GLV type, it is possible to configure the pixels without gaps. However, when displaying an image using such a sub-scanning optical unit, the luminance between the pixels. Can be interpolated, and conversely, the pixels can be separated from each other. It is also possible to secure an interval between the light modulation elements corresponding to the pixels. In addition, when a light emitting element with a light modulation function such as an array liquid crystal element, an array LD, or an array LED arranged in a one-dimensional type having another configuration is used instead of a light source and a light modulation device, pixels are separated, In other words, there is a dark level region between pixels. Even in the case of using such a light modulation device, such a gap can be interpolated by performing interlaced display by the sub-scanning optical unit having the above-described configuration, and an image can be displayed with better image quality. It becomes possible. As the interval between pixels increases, the effect of improving the image quality by such interpolation can be obtained.

  In the above example, the scanning angle of the sub-scanning optical unit is set to two directions. However, three or more directions are selected and the pixel arrangement direction is set to, for example, 1/3, 1/4,. It is also possible to display the image by shifting and deflecting. That is, an arbitrary number of two or more pixels can be displayed slightly shifted between one pixel of line-shaped image light projected in one scanning direction, that is, the tilt angle of the sub-scanning optical unit Can be selected in n (n is a natural number of 2 or more) directions and the pixels can be deflected by shifting by 1 / n. In this case, it is possible to arbitrarily select the number of pixels to interpolate between the pixels in accordance with the pixel interval of the light modulation device. This makes it possible to maintain good image quality with a simple configuration in which the scanning angle of the sub-scanning optical unit is selected without being limited to the characteristics of the light modulation device, and the degree of freedom in designing the light modulation device. It is possible to increase.

As described above, according to the present invention, streaks in a projection image caused by manufacturing variations of each light modulation element of a one-dimensional light modulation device can be obtained by providing a sub-scanning optical unit. It can be suppressed by averaging by scanning in the longitudinal direction.
In particular, in dark gradations, manufacturing variations of the light modulation elements of the one-dimensional light modulation device appear as streaks in the image as they are, so that the streak reduction effect is particularly great. For example, even if the pixel with the lowest contrast of about 1500: 1 is averaged over 6 pixels, the average is improved to 5000: 1. Therefore, it is desirable to average over 6 pixels. Further, even from the intermediate gradation to the bright gradation, the relationship between the light intensity and the voltage is unique due to the one-dimensional light modulation device, so that the effect of reducing streaks is also obtained.
In addition, when a polygon mirror is used as the main scanning optical unit, the vertical resolution can be obtained by performing angle control that offsets the error by the sub-scanning optical unit even if the surface tilt accuracy error of each mirror surface of the polygon mirror is large. Degradation does not occur, and the mirror manufacturing cost can be greatly reduced.
Furthermore, the resolution can be doubled as an interlaced image by shifting the same sub-scanning optical unit by an angle corresponding to half of one pixel for each frame.
By using a common sub-scanning optical unit, it is possible to simultaneously reduce streaks, reduce the cost of the polygon mirror, and double the interlace resolution.

  In addition, this invention is not limited to the structure demonstrated in each above-mentioned each embodiment, For example, when using a monochromatic light source as a light source, when using a two-color light source, and 3 other than red, green, and blue The present invention can also be applied to a case where a color light source is used or a case where four color light sources are used. In addition, as described above, various one-dimensional type light modulation devices can be applied as the light modulation device, and various modifications and changes can be made without departing from the configuration of the present invention. Nor.

It is a schematic block diagram of an example of the image projection apparatus which concerns on the embodiment of this invention. 1 is a schematic perspective configuration diagram of a main part of an example of an image projection apparatus according to an embodiment of the present invention. It is a schematic block diagram of an example of the sub-scanning optical part of the image projector which concerns on the embodiment of this invention. It is a figure which shows the time change of the moving width | variety of the image from the reference position in an example of the image projector which concerns on the example of embodiment of this invention. It is a figure which shows the allocation position of the image signal for every flame | frame with respect to a light modulation element. It is a figure which shows the relationship between the average pixel number and contrast. It is a schematic block diagram of an example of the sub-scanning optical part of the image projector which concerns on the embodiment of this invention. It is a schematic block diagram of an example of the sub-scanning optical part of the image projector which concerns on the embodiment of this invention. 1 is a schematic perspective configuration diagram of a main part of an example of an image projection apparatus according to an embodiment of the present invention. 1 is a schematic perspective configuration diagram of a main part of an example of an image projection apparatus according to an embodiment of the present invention. It is explanatory drawing of the display mode of the pixel of the image projection apparatus which concerns on the example of embodiment of this invention. It is explanatory drawing of the display mode of the pixel of the image projection apparatus which concerns on the example of embodiment of this invention. It is a schematic plane block diagram of an example of the conventional light modulation apparatus. FIG. 8 is a schematic cross-sectional configuration diagram of a first electrode taken along arrow AA in FIG. 7. FIG. 8 is a schematic cross-sectional configuration diagram of the second electrode in a non-driven state along arrow BB in FIG. 7. FIG. 8 is a schematic cross-sectional configuration diagram of a driving state of a second electrode along arrow BB in FIG. 7. FIG. 8 is a schematic cross-sectional configuration diagram of first and second electrodes along arrow CC in FIG. 7. It is a schematic sectional block diagram of an example of a light modulation apparatus.

Explanation of symbols

11. Light modulation element, 12. Substrate, 13. Light transmissive member, 31. First electrode, 32. Second electrode, 33. Lower electrode, 46.1 dimensional image, 47.2 dimensional image, 100 (100R, 100G, 100B). Light source 101 (101R, 101G, 101B). Illumination optical system, 102 (102R, 102G, 102B). Light modulation device, 104. Color composition unit, 105. Light selector, 105S. Schlieren filter, 106. Projection lens, 107. Sub-scanning optical unit, 108. Main scanning optical unit, 108A. Polygon mirror, 110. Modulation optical unit, 120. Projection optical unit, 130. Scanning optical section, 150. Screen, 150S. Image generation surface

Claims (5)

In an image projection apparatus having a modulation optical unit including a one-dimensional light modulation device, a projection optical unit, a scanning optical unit, and a signal processing unit ,
A main scanning optical unit that scans in the scanning optical unit in a direction substantially orthogonal to the longitudinal direction of the one-dimensional light modulation device, and a sub-scanning optical unit that scans in the longitudinal direction of the one-dimensional light modulation device. equipped with a,
The sub-scanning optical unit changes the optical axis angle in the longitudinal direction of the one-dimensional light modulation device by an integral multiple of an angle corresponding to one pixel interval in an image frame formed by the main scanning optical unit. With
The signal processing unit compensates for an image signal input to the one-dimensional light modulation device corresponding to the movement of the number of pixels corresponding to the changed optical axis angle.
Image projection device. The main scanning optical unit is Ru polygon mirror der
Image projection device as claimed in 請 Motomeko 1. By the sub-scanning optical unit, the optical axis angle in the longitudinal direction of the projection image of the one-dimensional light modulation device so as to cancel the individual mirrors tilt error of the polygon mirror Ru is corrected
The image projection apparatus according to claim 2 . Light projected from the optical scanning unit, Ru is imaged on the image generating surface of the generally cylindrical
Image projection device as claimed in 請 Motomeko 2 or claim 3. For each frame of the image formed by the main scanning optical unit, Ru is scanned by the sub-scanning optical unit with a movement amount corresponding to substantially half a pixel interval of the one-dimensional light modulation device
Image projection apparatus according to any one of 請 Motomeko 1 to 4.

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