Scanning-type projection system

Abstract

The present invention improves the color reproducibility of video generated by a laser beam.　Provided is a scanning-type projection system comprising: a controller and a memory; a light source for emitting a laser beam; an optical deflector for projecting the laser beam onto a projection surface; a first drive circuit for variably setting the output value of the laser beam and driving the light source; and a second drive circuit for driving the optical deflector. The optical deflector has an enhanced reflective film. The memory saves correction data set on the basis of a reflectance that changes in accordance with the angle of incidence with respect to the enhanced reflective film. The controller sets a target output value of the laser beam on the basis of image data inputted from the outside, sets a deflection angle having a different value for each scanning line within the same frame, sets a correction coefficient corresponding to the angle of incidence determined in accordance with the deflection angle by using the correction data read out from the memory, and corrects the target output value using the correction coefficient, thereby establishing the output value of the laser beam.

Description

Scanning Projection System

[0001] The present disclosure relates to scanning projection systems.

[0002] Japanese Patent Laid-Open Publication No. 2021-89400 (Patent Document 1) describes a display device that displays an image generated by laser light, which includes a laser whose optical output changes depending on current, a memory unit that stores a conversion table that corrects the laser's current-optical output characteristics so that they approach a desired shape, a control unit that reads the conversion table from the memory unit and emits the laser based on data converted using the conversion table, and a light scanning unit that scans the laser light. The light scanning unit is configured with a mirror driven by, for example, a piezoelectric element.

[0003] However, when a reflection-enhancing film made of, for example, a dielectric multilayer film is provided to improve the reflectivity of a mirror used for scanning laser light, variations in reflectivity occur depending on the wavelength of the laser light, which can result in a decrease in the color reproducibility of the image or illumination light (hereinafter referred to as "image, etc.") generated by the laser light.

[0004] Japanese Patent Application Laid-Open No. 2021-89400

[0005] One of the objects of a specific aspect of the present disclosure is to improve the color reproducibility of images and the like generated by laser light.

[0006] a first drive circuit that variably sets an output value of the laser light emitted from the light source to drive the light source; a second drive circuit that drives the optical deflector; a controller connected to each of the first drive circuit and the second drive circuit, the controller supplying first control data including the output value of the laser light to the first drive circuit and second control data including a deflection angle of the optical deflector to the second drive circuit; and a memory connected to the controller, wherein the optical deflector has a reflection-enhancing film, and the memory stores correction data that is set based on the reflectivity of the optical deflector, which changes depending on the angle of incidence of the laser light on the reflection-enhancing film of the optical deflector, The controller sets a target output value of the laser light based on a signal input from outside, sets the deflection angle to a different value for each scan line within the same frame, sets a correction coefficient corresponding to the angle of incidence determined according to the deflection angle using the correction data read from the memory, and determines the output value of the laser light by correcting the target output value using the correction coefficient. This is a scanning projection system.

[0007] According to the above configuration, it is possible to improve the color reproducibility of images and the like generated by laser light.

[0008] FIG. 1 is a block diagram showing the configuration of a scanning display system according to an embodiment. FIG. 2 is a block diagram showing a detailed configuration example of a system control unit. FIG. 3A is a side view schematically showing the arrangement of a scanning display system and a screen when there is no trapezoidal distortion. FIG. 3B is a schematic front view of the screen. FIG. 3C is a diagram showing the scanning state of laser light on the screen when there is no trapezoidal distortion. FIG. 4A is a cross-sectional view taken along line A-A in FIG. 3B. FIG. 4B is a cross-sectional view taken along line B-B in FIG. 3B. FIG. 5A is a side view schematically showing the arrangement of a scanning display system and a screen when there is trapezoidal distortion. FIG. 5B is a schematic front view of the screen. FIG. 5C is a diagram showing the scanning state of laser light on the screen when there is trapezoidal distortion. FIG. 5D is a diagram schematically showing how trapezoidal distortion in an irradiation area on the screen is corrected. FIG. 6 is a cross-sectional view taken along line C-C in FIG. 5D. FIG. 7A is a cross-sectional view taken along line D-D in FIG. 5D. FIG. 7B is a cross-sectional view taken along line E-E in FIG. 5D. FIGS. 8A to 8C are cross-sectional views schematically illustrating the configuration of a deflection mirror according to this embodiment. FIG. 9A is a diagram illustrating an example of the relationship between the angle of incidence of light incident on the deflection mirror and the reflectance of reflected light. FIG. 9B is a diagram illustrating an example of a correction coefficient for correcting variations in laser output values ​​caused by the angle of incidence. FIGS. 10A and 10B are diagrams schematically illustrating the relationship between the deflection angle and the angle of incidence of the deflection mirror. FIG. 11 is a diagram illustrating an example of a data table showing the relationship between color gradation and the output of each laser beam. FIGS. 12A to 12C are data tables illustrating examples of reflectance and correction coefficients for deflection angles and angles of incidence. FIG. 13 is a flowchart illustrating the operation procedure of a scanning display system.

[0009] 1 is a block diagram showing the configuration of a scanning display system according to one embodiment. The scanning display system 100 of this embodiment forms an image by scanning a laser beam on a projection surface of a screen (projection target) 40 using a raster scan method, and includes a system control unit 1, a storage unit 2, an operation unit 3, an image processing unit 4, a light source driving unit (first driving circuit) 5, semiconductor light sources 6 and 7, a deflection angle control unit 8, a driving circuit (second driving circuit) 9, a mirror device (optical deflector) 10, a light receiving element 11, and a distance measurement unit 12. In this embodiment, the system control unit 1, the image processing unit 4, and the deflection angle control unit 8 constitute a "controller."

[0010] The system control unit 1 controls the overall operation of the scanning display system 100. For example, the system control unit 1 supplies control data to the light source driving unit 5 and the deflection angle control unit 8 so as to synchronize the operation of the mirror device 10 with the operation of the semiconductor light source 6. This system control unit 1 can be configured, for example, by using a computer system including a processor and a memory and causing the processor to execute a predetermined operating program.

[0011] The storage unit 2 is connected to the system control unit 1, and stores and holds various data used in the system control unit 1. The storage unit 2 is configured using, for example, a nonvolatile memory, and is configured so that the various data stored therein can be rewritten as appropriate.

[0012] The operation unit 3 is connected to the system control unit 1, and is configured so that when a user (or manufacturer, etc.) of the scanning display system 100 wants to make changes to the operation of the system, the user can input the changes. In response to the input changes, the system control unit 1 executes, for example, a process of changing the operating parameters of each block in the system, a process of rewriting data stored in the storage unit 2, etc.

[0013] The image processing unit 4 is connected to the system control unit 1, receives a video signal input from an external device (not shown), and generates image data for controlling the semiconductor light source 6 so that an image based on the video signal can be projected by laser light. The generated image data is output to the system control unit 1. The image processing unit 4 can be configured using, for example, an image processing processor.

[0014] The light source driving unit 5 is connected to the system control unit 1, and generates driving signals for causing each semiconductor light source 6, 7 to emit light (turn on) based on control data (first control data) generated by the system control unit 1 using image data generated by the image processing unit 4, and outputs the driving signals to each semiconductor light source 6, 7.

[0015] Each of the semiconductor light sources 6 and 7 is connected to the light source driver 5 and operates based on a drive signal supplied from the light source driver 5. The semiconductor light source 6 includes three light-emitting elements corresponding to the three primary colors of RGB (red, green, and blue), and emits laser light of visible light wavelengths corresponding to red, green, and blue, respectively, when the light-emitting elements emit light based on the drive signal supplied from the light source driver 5. The semiconductor light source 7 includes a light-emitting element corresponding to infrared light, which is an example of invisible light, and emits laser light of an infrared wavelength when the light-emitting element emits light based on the drive signal supplied from the light source driver 5.

[0016] The deflection angle control unit 8 is connected to the system control unit 1 and generates control data (second control data) for controlling the deflection angle of the mirror device 10. The deflection angle control unit 8 can be configured, for example, by using a computer system including a processor and a memory and causing the processor to execute a predetermined operating program. The deflection angle control unit 8 may be configured integrally with the system control unit 1.

[0017] The drive circuit 9 is connected to the deflection angle control unit 8, and generates a drive signal for operating the mirror device 10 based on the control data output from the deflection angle control unit 8, and outputs the drive signal to the mirror device 10.

[0018] The mirror device 10 is disposed at a position where the laser light emitted from each of the semiconductor light sources 6 and 7 can be incident, and reflects the incident laser light to scan it by raster scanning on the projection surface of the screen 40. An image is displayed on the screen 40 by raster scanning the laser light. The mirror device 10 can be configured using, for example, a MEMS device having a micromirror.

[0019] The light receiving element 11 receives the infrared wavelength laser light that is emitted from the semiconductor light source 7, enters the screen 40, and is reflected by the projection surface of the screen 40, and outputs a signal according to the intensity of the light.

[0020] The distance measurement unit 12 is connected to both the system control unit 1 and the light receiving element 11, and measures the distance between the screen 40 and the scanning display system 100 based on a signal output from the light receiving element 11. This distance can be measured based on the time difference between the emission of light from the semiconductor light source 7 and the reception of light by the light receiving element 11. Distance data indicating the measured distance is output to the system control unit 1. For example, the distance measurement unit 12 measures the distance to each position (e.g., the four corners) on the projection surface of the screen 40. The system control unit 1 determines whether the projection surface of the screen 40 is parallel to or tilted from the scanning display system 100 based on these distances, and if it is tilted, corrects keystone distortion.

[0021] 2 is a block diagram showing a detailed configuration example of the system control unit 1. The system control unit 1 includes an overall control block 20, an operation information processing block 21, a data block 22, and a laser power control block 23.

[0022] The overall control block 20 controls the overall operation of the system control unit 1. For example, the overall control block 20 performs control such as synchronizing the operation of the semiconductor light source 6 based on the driving state of the mirror device 10. The overall control block 20 also calculates a correction amount for adjusting the deflection angle of the mirror device 10 according to the distance data output from the distance measurement unit 12. Control data that reflects this correction amount and is supplied to the deflection angle control unit 8 is generated. The overall control block 20 also executes processes such as changing the operating parameters of each block in the system and rewriting data stored in the memory unit 2 according to the operation data (data indicating the contents of the operation instruction) output from the operation information processing block 21.

[0023] The operation information processing block 21 processes signals input using the operation unit 3 to generate operation data representing the contents of the operation instruction, and outputs the operation data to the overall control block 20 .

[0024] The data block 22 stores various data used for information processing in the overall control block 20. This data is read from the memory unit 2 and stored in the data block 22, for example, when the system is started up. If there is a change in the data content, the data in the memory unit 2 is rewritten. The "R laser output," "G laser output," and "B laser output" stored in the data block 22 are the target output values ​​(target laser output values) of the RGB laser light corresponding to the target colors of the pixels that make up the image. The "incident angle" and "reflectance" stored in the data block 22 are the values ​​of the incident angle and reflectance corresponding to the deflection angle. The "angle correction amount" stored in the data block 22 is a value indicating the correction amount for correcting trapezoidal distortion.

[0025] The laser power control block 23 sets a correction coefficient for the output value of the laser light emitted by each of the RGB light emitting elements in the semiconductor light source 6 (hereinafter referred to as "laser output value") based on the timing signal, angle data, and color information output from the overall control block 20, and supplies the laser output value corrected using this correction coefficient as control data to the light source driver 8. Note that when correction according to reflectance is not performed, the laser power control block 23 supplies the laser output value corresponding to the color information to the light source driver 8 as control data without correcting it.

[0026] Here, we will explain the data and signals related to the system control unit 1. The data and signals input and output to and from the system control unit 1 include "pixel data" and "distance data" input to the overall control block 20, "infrared pulse data," "angle data," and "timing signal" output from the overall control block 20, "operation data" input to the operation information processing block 21, and "laser output data" output from the laser power control block 23.

[0027] "Pixel data" is data for determining the color of a pixel, and changes depending on the image to be projected and the scanning timing.

[0028] The "distance data" is data output from the distance measurement unit 12 and indicates the distance between the scanning display system 100 and the screen 40. In this embodiment, the distance data includes at least the distances at two measurement points, one set at the center in the left-right direction on the upper edge side of the projection surface of the screen 40 and the other set at the center in the left-right direction on the lower edge side, and preferably includes the distances at four points corresponding to the four corners of the projection surface.

[0029] The "infrared pulse data" is data for emitting laser light of an infrared wavelength from the semiconductor light source 7 in order to measure the distance to the projection surface of the screen 40. Specifically, the data includes data indicating the amplitude and pulse width (light emission period) of the laser light.

[0030] The "angle data" is data for instructing the deflection angle of the mirror device 10 to the deflection angle control unit 8 in accordance with the current scanning timing and the angle correction amount for keystone correction.

[0031] The "timing signal" is a signal that indicates the current state of the system based on the operating state of the mirror device 10. It contains at least information on the horizontal and vertical axis counts.

[0032] The "operation data" is data that indicates what operation has been performed by the operation unit 3. For example, it includes the content of updates to the data stored in the data block 22.

[0033] The "laser output data" is control data indicating a laser output value, which is a value specifying the light emission intensity of each light-emitting element of the semiconductor light source 6. A value of zero is specified when each light-emitting element is turned off. When the correction for reflectance is enabled, data indicating the corrected laser output value is output, and when the correction is disabled, data indicating the uncorrected laser output value is output.

[0034] FIG. 3A is a side view schematically illustrating the arrangement of a scanning display system and a screen when there is no trapezoidal distortion. As shown in the figure, when the distances between the light exit point P of the scanning display system 100 and the upper and lower ends of the screen 40 (preferably the four corners of the screen 40) are approximately equal, no trapezoidal distortion occurs in the image formed on the projection surface of the screen 40. FIG. 3B is a schematic front view of the screen 40. In this case, the deflection mirror 10b of the mirror device 10 of the scanning display system 100 is positioned opposite the center position of the irradiation area R on the projection surface of the screen 40, as shown in the figure. Furthermore, the entrance mirror 10a of the mirror device 10 is positioned higher than the deflection mirror 10b. Furthermore, when there is no trapezoidal distortion, the scanning state of the laser light on the projection surface of the screen 40 is uniform in both the vertical scanning interval and the horizontal scanning width of the screen 40, as shown in FIG. 3C.

[0035] FIG. 4A is a cross-sectional view taken along line A-A in FIG. 3B. FIG. 4B is a cross-sectional view taken along line B-B in FIG. 3B. In each figure, the entrance mirror 10a and the deflection mirror 10b are shown without hatching to facilitate visualization of auxiliary lines used to explain the optical path of the laser light (the same applies hereinafter). As shown in FIG. 4A, the entrance mirror 10a is positioned upward in the figure so as not to overlap with the scanning angle range α of the deflection mirror 10b. Laser light emitted from each light-emitting element of the semiconductor light source 6 enters the entrance mirror 10a, is reflected by the entrance mirror 10a, and is incident on the deflection mirror 10b as incident light L0.

[0036] As shown in FIG. 4A , when the deflection angle of the deflection mirror 10b is θ1 relative to the vertical direction shown in the figure, the incident angle of the incident light L0 is φ1. In this case, the incident light L0 is reflected by the deflection mirror 10b and is irradiated as reflected light L1 toward the upper edge of the projection surface of the screen 40. When the deflection angle of the deflection mirror 10b is θ2 relative to the vertical direction shown in the figure, the incident angle of the incident light L0 is φ2. In this case, the incident light L0 is reflected by the deflection mirror 10b and is irradiated as reflected light L2 toward the lower edge of the screen 40. By sequentially changing the deflection angle of the deflection mirror 10b, the laser light can be scanned in the vertical direction between the upper and lower edges of the screen 40.

[0037] As shown in FIG. 4B , when the deflection angle of the deflection mirror 10b is θ3 relative to the left-right direction shown in the figure, the incident angle of the incident light L0 is φ3. In this case, the incident light L0 is reflected by the deflection mirror 10b and is irradiated as reflected light L3 toward the left edge of the projection surface of the screen 40. When the deflection angle of the deflection mirror 10b is θ4 relative to the left-right direction shown in the figure, the incident angle of the incident light L0 is φ4. In this case, the incident light L0 is reflected by the deflection mirror 10b and is irradiated as reflected light L4 toward the right edge of the projection surface of the screen 40. By sequentially changing the deflection angle of the deflection mirror 10b, the laser light can be scanned left and right between the left and right edges of the screen 40.

[0038] 4A and 4B, when the deflection angle of the deflection mirror 10b changes, the angle of incidence of the incident light L0 also changes accordingly. In this embodiment, as shown in FIG. 8A (described later), the deflection mirror 10b is provided with an enhanced reflection coating 52 on its incident surface, and the reflectance of the reflected light changes depending on the angle of incidence of the incident light L0 due to the incident angle dependency of the enhanced reflection coating 52. This results in a decrease in the color reproducibility of the image.

[0039] 5A is a side view schematically showing the arrangement of a scanning display system and a screen when trapezoidal distortion occurs. As shown in the figure, if the distances between the light exit point P of the scanning display system 100 and the upper and lower ends of the screen 40 (preferably the four corners of the screen 40) are not equal, trapezoidal distortion occurs in the image formed on the projection surface of the screen 40. In the example shown in the figure, the distance between the light exit point P and the upper end of the screen 40 is shorter than the distance between the light exit point P and the lower end.

[0040] A schematic front view of the screen 40 is shown in FIG. 5B. Because trapezoidal distortion occurs, the irradiation area R on the projection surface of the screen 40 will be trapezoidal as shown in the figure unless special correction is performed. When trapezoidal distortion occurs, the scanning state of the laser light on the projection surface of the screen 40 will have a trajectory such as that shown by the dotted line in FIG. 5C if no correction is performed. In contrast, if the deflection angle of the deflection mirror 10b is corrected, the trajectory will be that shown by the solid line in FIG. 5C. Specifically, the deflection angle is corrected so that the scanning width in the left-right direction in the figure becomes narrower as one approaches the bottom edge of the screen 40. As a result, the trapezoidal distortion of the irradiation area R on the projection surface of the screen 40 is corrected as shown in FIG. 5D.

[0041] FIG. 6 is a cross-sectional view taken along line CC shown in FIG. 5(D). The symbols (θ1, θ2, φ1, φ2, L0, L1, L2, α) shown in the figure have the same meanings as those in FIG. 4(A). As shown in FIG. 6, trapezoidal distortion occurs, for example, due to a difference between the reflected light L1 irradiated toward the upper edge of the screen 40 and the reflected light L2 irradiated toward the lower edge of the screen 40. Therefore, as described above, the deflection angle of the deflection mirror 10b is corrected so that the scanning width of the reflected light narrows as it approaches the lower edge of the screen 40. This corrects the trapezoidal distortion in the irradiation area R.

[0042] Fig. 7(A) is a cross-sectional view taken along line D-D in Fig. 5(D). Fig. 7(B) is a cross-sectional view taken along line E-E in Fig. 5(D). The symbols (φ3, φ4, L3, L4, α) shown in the figure have the same meanings as those in Fig. 4(B) described above.

[0043] 7A and 7B, when the scanning width of the reflected light is narrowed to correct for keystone distortion, the scanning angle range α becomes narrower the closer to the bottom edge of the screen 40. In other words, the closer the irradiation position of the reflected light is to the bottom edge of the screen 40, the smaller the angles of incidence φ3 and φ4 on the deflection mirror 10b become. For this reason, when considering correction for the incidence angle dependency of the reflection-enhancing film 52 of the deflection mirror 10b, it can be said that it is difficult to improve the color reproducibility of the image unless a correction different from that in the case where there is no keystone distortion is made.

[0044] Therefore, in the scanning display system 100 of this embodiment, the incident angle dependency of the reflectance of the reflection-enhancing film 52 is corrected depending on the presence or absence of trapezoidal distortion on the screen 40 and the degree of the distortion. Specifically, the deflection angle of the deflection mirror 10b is set to a different value for each horizontal scanning line within one frame of the image, and the output value of the laser light from each light-emitting element of the semiconductor light source 6 is dynamically corrected accordingly, thereby improving the color reproducibility of the image. This method will be described in detail below.

[0045] 8A to 8C are cross-sectional views schematically showing the configuration of the deflection mirror of this embodiment. For ease of explanation, hatching has been omitted. As shown in FIG. 8A, the deflection mirror 10b of this embodiment is configured to include a substrate 50, a reflective film 51 provided on one surface of the substrate 50, and an enhanced reflection film 52 provided to cover one surface of the reflective film 51 (the surface not in contact with the substrate 50). The substrate 50 is, for example, a Si substrate. The reflective film 51 is, for example, an aluminum film. The enhanced reflection film 52 is, for example, a dielectric multilayer film.

[0046] 8(B), when the deflection angle of the deflection mirror 10b is 0° and the incident angle of the incident light is incident angle 1, the optical path length of the incident light from passing through the enhanced reflection film 52 to reaching the reflective film 51 is defined as optical path length 1. Also, when the deflection angle of the deflection mirror 10b is deflection angle 2 which is larger than 0° and the incident angle of the incident light is incident angle 2 which is larger than the above-mentioned incident angle 1, as shown in FIG.

[0047] Comparing optical path length 1 and optical path length 2, it can be seen that optical path length 2 is longer. The optical path length that the incident light takes to reflect off the reflective film 51 and exit the enhanced reflection film 52 to the outside is twice the optical path length 1 or 2. This difference in optical path length causes a wavelength shift in the reflectance, increasing or decreasing the reflectance of a specific wavelength. Furthermore, although incident light has wavelengths corresponding to each of the RGB colors, the tendency for the reflectance to change differs for each wavelength of the laser light. Therefore, in this embodiment, in order to suppress the effect of the incident angle dependency of the reflectance of the deflection mirror 10b, the output value of the laser light from each light-emitting element of the semiconductor light source 6 is variably controlled according to the deflection angle of the deflection mirror 10b.

[0048] 9A is a diagram showing an example of the relationship between the angle of incidence of light incident on the deflection mirror and the reflectance of reflected light. This diagram shows the change in reflectance when the angle of incidence is changed between 30° and 60° using red (wavelength 640 nm), green (wavelength 520 nm), and blue (wavelength 450 nm) laser light as incident light on the deflection mirror 10b under certain conditions.

[0049] As described above, the incident angle is determined according to the deflection angle of the deflection mirror 10b, so for example, if the deflection mirror 10b and the incident mirror 10a are directly opposite each other and the minimum deflection angle (0°) coincides with the minimum incident angle (0°), the incident angle increases as the deflection angle increases. The relationship between the deflection mirror 10b and the incident angle in this case is schematically shown in Figures 10(A) and 10(b).

[0050] When the incident mirror 10a is positioned to one side in the deflection direction of the deflection mirror 10b, there exists a range in which the incident angle increases as the deflection angle increases, and a range in which the incident angle decreases as the deflection angle increases. Specifically, with the position where the deflection angle of the deflection mirror 10b is 0 degrees as the origin, there exists a direction in which the incident angle increases as the deflection angle increases, and a direction in which the incident angle decreases as the deflection angle increases.

[0051] As can be seen from Figure 9(A), the reflectance of each of the red, green, and blue laser beams tends to decrease as the angle of incidence increases. If the deflection angle differs for each horizontal scanning line, the reflectance will differ depending on the angle of incidence, which may result in variations in the irradiation intensity of each laser beam on the screen 40. Furthermore, since the target laser output value and the reflectance at the deflection mirror 10b differ for each color of laser beam, correction must be performed for each color of laser beam. Specifically, as illustrated in Figure 9(B), a correction coefficient is calculated in advance to correct for variations in laser output value caused by the angle of incidence, and this is used to perform the correction.

[0052] The correction coefficients are set in accordance with the increase or decrease in reflectance with respect to the angle of incidence. Even in the case where the three primary color laser beams are combined into one and reflected by the deflection mirror 10b as in this embodiment, the correction coefficients are calculated from the reflectance of each color. In the correction coefficients shown as examples, the reflectance of blue laser beam is generally lower than the reflectance of laser beams of other colors, so the correction coefficient for blue laser beam is set to a higher value than the correction coefficients for laser beams of other colors. Furthermore, the reflectance of each of red and green laser beams decreases (gradient) as the angle of incidence increases. Therefore, the correction coefficients for each of red and green laser beams increase (gradient) as the angle of incidence increases.

[0053] Based on the relationship between the incident angle and reflectance shown in Figure 9A, we will examine the difference in laser output value when correcting for trapezoidal distortion. Here, we assume that the largest deflection angle is 60°, and the smallest deflection angle is 30°. Before reflection by the deflection mirror 10b occurs, the laser output values ​​that produce the reference 6500K white color are as follows: Red: 29.159 [mW] Green: 20.019 [mW] Blue: 12.625 [mW]

[0054] For the horizontal scan line with the largest deflection angle, the laser output value after reflection of the laser light emitted at an incident angle of 60° is as follows: Red: 29.159 x 0.9481 = 27.646 [mW] Green: 20.019 x 0.9640 = 19.298 [mW] Blue: 12.625 x 0.9047 = 11.422 [mW]

[0055] For the horizontal scan line with the smallest deflection angle, the laser light emitted at an incident angle of 30° has the following laser output values ​​after reflection: Red: 29.159 x 0.9750 = 28.430 mW Green: 20.019 x 0.9856 = 19.730 mW Blue: 12.625 x 0.9318 = 11.763 mW

[0056] Therefore, the difference between a deflection angle of 30° and a deflection angle of 60° is as follows: Red: 28.430 - 27.646 = 0.784 [mW] Green: 19.730 - 19.298 = 0.432 [mW] Blue: 11.763 - 11.422 = 0.341 [mW]

[0057] 11 is a diagram showing an example of a data table showing the relationship between color gradation and the output power of each laser beam. As shown by the bold line in the diagram, for example, the difference in red laser output power between a color gradation value of 251 based on pixel data and a color gradation value of 255 is 0.3912 [mW]. In other words, the difference in laser output power corresponding to a difference of four color gradations is 0.3912 [mW]. As described above, the difference in red laser output power between a deflection angle of 30° and a deflection angle of 60° is 0.784 [mW], so it can be seen that a difference in deflection angle results in a difference in laser output power of more than four gradations.

[0058] 12(A) to 12(C) are data tables showing examples of reflectance and correction coefficients for deflection angle and incident angle. These data tables are correction data obtained by digitizing the graphs shown in FIGS. 9(A) and 9(B), where FIG. 12(A) corresponds to blue laser light, FIG. 12(B) corresponds to green laser light, and FIG. 12(C) corresponds to red laser light. Note that while the correspondence between deflection angle, incident angle, reflectance, and correction coefficient is shown here for ease of understanding, the data table actually held in the memory unit 2 and temporarily stored in the data block 22 only needs to include at least the deflection angle (or incident angle) and the correction coefficient. By using these data tables, a correction coefficient corresponding to the deflection angle (or incident angle) can be identified, and the laser output value can be corrected using the identified correction coefficient.

[0059] 13 is a flowchart showing the operation procedure of the scanning display system. The order of the processes shown here can be changed as long as no contradictions or inconsistencies occur in the results of the information processing, and other processes not specifically shown here can be added. By repeatedly executing the flow shown in FIG. 13, an image is formed on the projection surface of the screen 40 by the raster scan method.

[0060] The overall control block 20 of the system control unit 1 acquires image data from the image processing unit 4 (step S11). Here, pixel data (pixel position, color information) that is image data for one pixel constituting the image to be projected is acquired.

[0061] Next, the overall control block 20 acquires a target laser output value by reading out the data stored in the data block 22 (see FIG. 11) based on the acquired image data (step S12).

[0062] The overall control block 20 identifies the deflection angles of the deflection mirror 10b corresponding to the horizontal and vertical directions based on the pixel positions included in the image data, and obtains the correction coefficients corresponding to the deflection angles by referring to the data table (step S13). Here, the correction coefficient (first correction coefficient) corresponding to the horizontal direction (left-right direction) is designated X0, and the correction coefficient (second correction coefficient) corresponding to the vertical direction (up-down direction) is designated Y0. The correction coefficient X0 includes correction coefficients Xr0, Xg0, and Xb0 corresponding to the respective RGB colors. The correction coefficient Y0 includes correction coefficients Yr0, Yg0, and Yb0 corresponding to the respective RGB colors.

[0063] The overall control block 20 calculates the tilt of the screen 40 using the distance data obtained from the distance measurement unit 12 (step S14). For example, if the distances to the four corners of the screen 40 are equal based on the distance data, it can be said that there is "no tilt." Here, if the difference in the distances to the four corners is within a predetermined error range, it is determined that there is "no tilt." Furthermore, if the distance to the bottom edge of the screen 40 is longer than the distance to the top edge, or conversely, if the distance to the top edge of the screen 40 is longer than the distance to the bottom edge, it is determined that there is "vertical tilt," and the degree of this tilt is calculated. Furthermore, if the distance to the right edge of the screen 40 is longer than the distance to the left edge, or conversely, if the distance to the left edge of the screen 40 is longer than the distance to the right edge, it is determined that there is "horizontal tilt," and the degree of this tilt is calculated.

[0064] If there is no trapezoidal distortion, i.e., if the screen 40 is "not tilted" (step S15; NO), the overall control block 20 calculates a corrected laser output value using the correction coefficient acquired in step S13 (step S16). Here, the corrected laser output value is calculated by multiplying the target laser output value by (1+X0+Y0). More specifically, it is as follows: Corrected red laser output value = Target red laser output value × (1+Xr0+Yr0) Corrected green laser output value = Target green laser output value × (1+Xg0+Yg0) Corrected blue laser output value = Target blue laser output value × (1+Xb0+Yb0)

[0065] The laser power control block 23 determines the RGB signals based on the corrected laser output values ​​calculated by the overall control block 20, generates corresponding control data, or laser output data, and outputs it to the light source driver 5 (step S17). The light source driver 5 generates drive signals based on this control data, and the semiconductor light source 6 is driven based on these drive signals. As a result, red, green, and blue laser light beams are emitted from the light-emitting elements of the semiconductor light source 6, enter the mirror device 10, and are scanned by the deflection mirror 10b to form one pixel of an image on the screen 40. It is assumed that the mirror device 10 is controlled to a deflection angle corresponding to the pixel position by the drive circuit 9 being controlled by the deflection angle controller 8 using the angle data output from the overall control block 20, and the drive signal is provided from the drive circuit 9 (the same applies hereinafter).

[0066] On the other hand, if there is trapezoidal distortion, i.e., if the screen 40 is "tilted" (step S15; YES), or if there is trapezoidal distortion only in the vertical direction (up and down direction) of the screen 40, i.e., if the screen 40 is "tilted in the vertical direction" (step S18; YES), the overall control block 20 sets the deflection angle according to the amount of distortion of the horizontal line (step S19). In other words, the trapezoidal distortion is corrected (see FIG. 5(B)).

[0067] The overall control block 20 identifies the deflection angles of the deflection mirror 10b corresponding to the horizontal and vertical directions based on the pixel positions included in the image data, and obtains the correction coefficients corresponding to the deflection angles by referring to the data table described above (step S20). Here, the correction coefficient (first correction coefficient) corresponding to the horizontal direction (left-right direction) is designated X1, and the correction coefficient (second correction coefficient) corresponding to the vertical direction (up-down direction) is designated Y0. The correction coefficient X1 includes correction coefficients Xr1, Xg1, and Xb1 corresponding to the RGB colors. The correction coefficients for the vertical direction are the correction coefficients Y0 (Yr0, Yg0, Yb0) described above.

[0068] The overall control block 20 changes the horizontal correction coefficient from X0 to X1 (step S21). Then, the overall control block 20 calculates a corrected laser output value based on the correction coefficients X1 and Y0 (step S22). Here, the corrected laser output value is calculated by multiplying the target laser output value by (1 + X1 + Y0). More specifically, it is as follows: Corrected red laser output value = Target red laser output value × (1 + Xr1 + Yr0) Corrected green laser output value = Target green laser output value × (1 + Xg1 + Yg0) Corrected blue laser output value = Target blue laser output value × (1 + Xb1 + Yb0)

[0069] Thereafter, the process of step S17 described above is executed, whereby red, green, and blue laser beams are emitted from the light emitting elements of the semiconductor light source 6, enter the mirror device 10, and are scanned by the deflection mirror 10b to form one pixel of the image on the screen 40.

[0070] On the other hand, if the trapezoidal distortion of the screen 40 is not only in the vertical direction (step S18; NO), but also in the horizontal direction of the screen 40, i.e., if the screen 40 is "tilted in the horizontal direction" (step S23; YES), the overall control block 20 sets the deflection angle according to the amount of distortion of the vertical line (step S24). In other words, the trapezoidal distortion is corrected.

[0071] The overall control block 20 identifies the deflection angles of the deflection mirror 10b corresponding to the horizontal and vertical directions based on the pixel positions included in the image data, and obtains the correction coefficients corresponding to the deflection angles by referring to the data table described above (step S20). Here, the correction coefficient (first correction coefficient) corresponding to the horizontal direction (left-right direction) is designated X0, and the correction coefficient (second correction coefficient) corresponding to the vertical direction (up-down direction) is designated Y2. The correction coefficient Y2 includes correction coefficients Yr2, Yg2, and Yb2 corresponding to the RGB colors. The correction coefficients for the horizontal direction are the correction coefficients X0 (Xr0, Xg0, Xb0) described above.

[0072] The overall control block 20 changes the vertical correction coefficient from Y0 to Y2 (step S26). Then, the overall control block 20 calculates a corrected laser output value based on the correction coefficients X0 and Y2 (step S27). Here, the corrected laser output value is calculated by multiplying the target laser output value by (1 + X0 + Y2). More specifically, it is as follows: Corrected red laser output value = Target red laser output value × (1 + Xr0 + Yr2) Corrected green laser output value = Target green laser output value × (1 + Xg0 + Yg2) Corrected blue laser output value = Target blue laser output value × (1 + Xb0 + Yb2)

[0073] Thereafter, the process of step S17 described above is executed, whereby red, green, and blue laser beams are emitted from the light emitting elements of the semiconductor light source 6, enter the mirror device 10, and are scanned by the deflection mirror 10b to form one pixel of the image on the screen 40.

[0074] On the other hand, if the trapezoidal distortion of the screen 40 is not only in the horizontal direction (step S23; NO), that is, if the trapezoidal distortion of the screen 40 is in both the horizontal and vertical directions (step S23; NO), the overall control block 20 sets the deflection angle according to the amount of distortion of each of the horizontal and vertical lines (step S28).In other words, the trapezoidal distortion is corrected.

[0075] The overall control block 20 identifies the deflection angles of the deflection mirror 10b corresponding to the horizontal and vertical directions based on the pixel positions included in the image data, and obtains correction coefficients corresponding to the deflection angles by referring to the data table (step S29). Here, the correction coefficient (first correction coefficient) corresponding to the horizontal direction (left-right direction) is designated X3, and the correction coefficient (second correction coefficient) corresponding to the vertical direction (up-down direction) is designated Y3. The correction coefficient X3 includes correction coefficients Xr3, Xg3, and Xb3 corresponding to the respective RGB colors. Furthermore, the correction coefficient Y3 includes correction coefficients Yr3, Yg3, and Yb3 corresponding to the respective RGB colors.

[0076] The overall control block 20 changes the horizontal correction coefficient from X0 to X3 and the vertical correction coefficient from Y0 to Y3 (step S30). Then, the overall control block 20 calculates a corrected laser output value based on the correction coefficients X3 and Y3 (step S31). Here, the corrected laser output value is calculated by multiplying the target laser output value by (1 + X3 + Y3). More specifically, it is as follows: Corrected red laser output value = Target red laser output value × (1 + Xr3 + Yr3) Corrected green laser output value = Target green laser output value × (1 + Xg3 + Yg3) Corrected blue laser output value = Target blue laser output value × (1 + Xb3 + Yb3)

[0077] Thereafter, the process of step S17 described above is executed, whereby red, green, and blue laser beams are emitted from the light emitting elements of the semiconductor light source 6, enter the mirror device 10, and are scanned by the deflection mirror 10b to form one pixel of the image on the screen 40.

[0078] According to the above-described embodiment, it is possible to improve the color reproducibility of an image generated by laser light.

[0079] It should be noted that the present disclosure is not limited to the contents of the above-described embodiment, and various modifications can be made within the scope of the gist of the present disclosure. For example, the above-described embodiment illustrates a scanning display system using a semiconductor light source 6 having three light-emitting elements corresponding to the three primary colors, but the technical concept of the present disclosure can be applied to cases where a semiconductor light source that emits laser light of at least one visible light wavelength is used.

[0080] Specifically, the technical concept of the present disclosure can be applied to, for example, a scanning display system that displays a monochrome image using laser light of one visible light wavelength, or a scanning display system that uses four or more light-emitting elements and combines the laser light from these elements.

[0081] Furthermore, the technical ideas of the present disclosure are not limited to image display applications, but can also be applied to, for example, a scanning illumination system that forms illumination light on a projection surface in a single color or multiple colors, thereby improving the color reproducibility of the illumination light.

[0082] In other words, the technical concept of the present disclosure can be widely applied to scanning projection systems that form images, illumination light, etc. by irradiating a projection surface with laser light while scanning it.

[0083] The present disclosure has the following features: (Supplementary Note 1) A scanning projection system that projects light onto a projection surface by a raster scan method, comprising: a light source that emits laser light of at least one visible light wavelength; an optical deflector that reflects and scans the laser light emitted from the light source and projects it onto the projection surface; a first drive circuit that drives the light source by variably setting an output value of the laser light emitted from the light source; a second drive circuit that drives the optical deflector; a controller connected to each of the first drive circuit and the second drive circuit, and that supplies first control data including the output value of the laser light to the first drive circuit and second control data including a deflection angle of the optical deflector to the second drive circuit; and a memory connected to the controller, wherein the optical deflector has a reflection-enhancing film, and the memory stores correction data that is set based on the reflectance of the optical deflector that changes depending on the angle of incidence of the laser light on the reflection-enhancing film of the optical deflector, 1. A scanning projection system, wherein the controller sets a target output value of the laser beam based on an externally input signal, sets the deflection angle to a different value for each scan line within the same frame, and sets a correction coefficient corresponding to the angle of incidence determined according to the deflection angle using the correction data read from the memory, and calculates the output value of the laser beam by correcting the target output value using the correction coefficient. (Supplementary Note 2) The scanning projection system according to Supplementary Note 1, wherein the correction coefficients include a first correction coefficient corresponding to a left-right direction of the projection surface and a second correction coefficient corresponding to a top-bottom direction of the projection surface. (Supplementary Note 3) The scanning projection system according to Supplementary Note 2, wherein when the projection surface is tilted in the top-bottom direction, the controller corrects keystone distortion on the projection surface by adjusting the deflection angle with respect to the left-right direction of the projection surface, and sets the first correction coefficient corresponding to the angle of incidence determined according to the deflection angle after adjustment for correcting the keystone distortion.(Supplementary Note 4) The scanning projection system according to Supplementary Note 2, wherein, when the projection surface is tilted in the left-right direction, the controller corrects keystone distortion on the projection surface by adjusting the deflection angle of the projection surface with respect to the up-down direction, and sets the second correction coefficient corresponding to the angle of incidence determined in accordance with the deflection angle after adjustment for correcting the keystone distortion. (Supplementary Note 5) The scanning projection system according to Supplementary Note 2, wherein, when the projection surface is tilted in both the up-down direction and the left-right direction, the controller corrects keystone distortion on the projection surface by adjusting the deflection angle of the projection surface with respect to each of the up-down direction and the left-right direction, and sets the first correction coefficient and the second correction coefficient corresponding to the angle of incidence determined in accordance with the deflection angle after adjustment for correcting the keystone distortion. (Appendix 6) A scanning projection system as set forth in any of Appendices 1 to 5, wherein the light source emits three laser beams corresponding to the three primary colors, and wherein the controller sets the correction coefficient individually for each of the three laser beams. (Appendix 7) A scanning projection system as set forth in any of Appendices 1 to 6, wherein the light projected onto the projection surface constitutes an image. (Appendix 8) A scanning projection system as set forth in any of Appendices 1 to 6, wherein the light projected onto the projection surface constitutes illumination light. (Appendix 9) A scanning projection system as set forth in any of Appendices 1 to 8, further including a distance measurement unit that measures distances to a plurality of positions on the projection surface, and wherein the controller determines the tilt of the projection surface based on the distances to the plurality of positions measured by the distance measurement unit.

[0084] 1: System control unit, 2: Memory unit, 3: Operation unit, 4: Image processing unit, 5: Light source driving unit, 6: Semiconductor light source (RGB), 7: Semiconductor light source (infrared), 8: Deflection angle control unit, 9: Drive circuit, 10: Mirror device, 10a: Incident mirror, 10b: Deflection mirror, 11: Light receiving element, 12: Distance measurement unit, 20: Overall control block, 21: Operation information processing block, 22: Data block, 23: Laser power control block, 40: Screen, 50: Substrate, 51: Reflection film, 52: Reflection-enhancing film, 100: Scanning display system

Claims

1. A scanning projection system that projects light onto a projection surface by a raster scan method, comprising: a light source that emits laser light of at least one visible light wavelength; an optical deflector that reflects and scans the laser light emitted from the light source and projects it onto the projection surface; a first drive circuit that drives the light source by variably setting the output value of the laser light emitted from the light source; a second drive circuit that drives the optical deflector; a controller connected to each of the first drive circuit and the second drive circuit, and that supplies first control data including the output value of the laser light to the first drive circuit and second control data including the deflection angle of the optical deflector to the second drive circuit; and a memory connected to the controller, wherein the optical deflector has a reflection-enhancing film, and the memory stores correction data that is set based on the reflectivity of the optical deflector, which changes depending on the angle of incidence of the laser light on the reflection-enhancing film of the optical deflector, the controller sets a target output value of the laser beam based on a signal input from outside, and sets the deflection angle to a different value for each scan line within the same frame, and sets a correction coefficient corresponding to the angle of incidence determined according to the deflection angle using the correction data read from the memory, and determines the output value of the laser beam by correcting the target output value using the correction coefficient.

2. The scanning projection system according to claim 1, wherein the correction coefficients include a first correction coefficient corresponding to the left-right direction of the projection surface and a second correction coefficient corresponding to the up-down direction of the projection surface.

3. The scanning projection system of claim 2, wherein, when the projection surface is tilted in the up-down direction, the controller corrects trapezoidal distortion on the projection surface by adjusting the deflection angle with respect to the left-right direction of the projection surface, and sets the first correction coefficient in accordance with the angle of incidence determined according to the deflection angle after adjustment for correcting the trapezoidal distortion.

4. The scanning projection system of claim 2, wherein, when the projection surface is tilted in the left-right direction, the controller corrects trapezoidal distortion on the projection surface by adjusting the deflection angle with respect to the up-down direction of the projection surface, and sets the second correction coefficient in accordance with the angle of incidence determined according to the deflection angle after adjustment for correcting the trapezoidal distortion.

5. The scanning projection system of claim 2, wherein, when the projection surface is tilted in both the up-down direction and the left-right direction, the controller corrects trapezoidal distortion on the projection surface by adjusting the deflection angle for each of the up-down direction and the left-right direction of the projection surface, and sets the first correction coefficient and the second correction coefficient in accordance with the angle of incidence determined according to the deflection angle after adjustment for correcting the trapezoidal distortion.

6. The scanning projection system according to claim 1, wherein the light source emits three laser beams corresponding to three primary colors, and the controller sets the correction coefficients individually for each of the three laser beams.

7. The scanning projection system according to claim 1, wherein the light projected onto the projection surface constitutes an image.

8. The scanning projection system according to claim 1, wherein the light projected onto the projection surface constitutes illumination light.

9. The scanning projection system according to claim 1, further comprising a distance measurement unit that measures distances to a plurality of positions on the projection surface, and the controller determines the tilt of the projection surface based on the distances to the plurality of positions measured by the distance measurement unit.

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