Scanning type projection system

Abstract

To improve color reproducibility of a video generated by a laser beam.SOLUTION: A scanning type projection system includes: a controller and a memory; a light source which emits a laser beam; a light deflector which projects the laser beam on a projection plane; a first drive circuit which variably sets an output value of the laser beam and drives the light source; and a second drive circuit which drives the light deflector. The light deflector includes a reflection enhancing film, and the memory stores data for correction which are set on the basis of a reflection factor which changes in response to an angle of incidence to the reflection enhancing 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 of a value which is different for each scanning line within the same frame, sets a correction coefficient corresponding to the incidence angle, which is determined in accordance with the deflection angle, using the data for correction read out of the memory and corrects the target output value using the correction coefficient, such that the output value of the laser beam is calculated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[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 an optical scanning unit that scans the laser light. The optical scanning unit is configured with a mirror driven by, for example, a piezoelectric element.

[0003] However, when a reflective coating 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-89400 Summary of the Invention [Problem to be solved by the invention]

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

[0006] In one aspect of the present disclosure, a scanning table projection system includes: A scanning projection system that projects light onto a projection surface by a raster scan method, a light source that emits laser light of at least one visible 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 variably sets an output value of the laser light emitted from the light source and drives the light source; a second driving 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 an output value of the laser light to the first drive circuit, and supplying second control data including a deflection angle of the optical deflector to the second drive circuit; a memory coupled to the controller; Including, the optical deflector has a reflection-enhancing film, 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; 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 scanning line within the same frame, and sets a correction coefficient corresponding to the incident angle determined according to the deflection angle using the correction data read from the memory, and obtains the output value of the laser beam by correcting the target output value using the correction coefficient; It 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. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing the configuration of a scanning display system according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing a detailed configuration example of the system control unit. [Figure 3] Fig. 3(A) is a side view showing a schematic arrangement of a scanning display system and a screen when there is no trapezoidal distortion, Fig. 3(B) is a schematic front view of the screen, and Fig. 3(C) is a diagram showing the scanning state of laser light on the screen when there is no trapezoidal distortion. [Figure 4] Fig. 4(A) is a cross-sectional view taken along line AA in Fig. 3(B), and Fig. 4(B) is a cross-sectional view taken along line BB in Fig. 3(B). [Figure 5] Fig. 5(A) is a side view showing a schematic arrangement of a scanning display system and a screen when trapezoidal distortion is present. Fig. 5(B) is a schematic front view of the screen. Fig. 5(C) is a diagram showing the scanning state of laser light on the screen when trapezoidal distortion is present. Fig. 5(D) is a diagram showing a state in which trapezoidal distortion in an irradiation area on the screen is corrected. [Figure 6] FIG. 6 is a cross-sectional view taken along line CC shown in FIG. 5(D). [Figure 7] Fig. 7(A) is a cross-sectional view taken along line DD in Fig. 5(D), and Fig. 7(B) is a cross-sectional view taken along line EE in Fig. 5(D). [Figure 8] 8(A) to 8(C) are cross-sectional views that schematically show the configuration of the deflection mirror of this embodiment. [Figure 9] 9A is a diagram showing an example of the relationship between the angle of incidence of light incident on a deflection mirror and the reflectance of reflected light, and FIG. 9B is a diagram showing an example of a correction coefficient for correcting variations in laser output value caused by the angle of incidence. [Figure 10] 10A and 10B are diagrams showing the relationship between the deflection angle of the deflection mirror and the angle of incidence. [Figure 11] FIG. 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. [Figure 12]12(A) to 12(C) are data tables showing examples of reflectances and correction coefficients with respect to deflection angles and incident angles. [Figure 13] FIG. 13 is a flowchart showing the operation procedure of the scanning display system. DETAILED DESCRIPTION OF THE INVENTION

[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 form 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, and the like.

[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 has 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 has a light-emitting element corresponding to infrared light, which is an example of invisible light, and emits laser light of infrared wavelengths when the light-emitting elements emit 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 driving circuit 9 is connected to the deflection angle control unit 8, and generates a driving signal for operating the mirror device 10 based on the control data output from the deflection angle control unit 8, and outputs the driving signal to the mirror device 10.

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

[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. Based on these distances, 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, 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 .

[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 respective values ​​of the incident angle and reflectance according 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 (hereinafter referred to as "laser output value") emitted by each of the RGB light emitting elements in the semiconductor light source 6, 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 data includes distances at least 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 distances at four points corresponding to the four corners of the projection surface.

[0029] The "infrared pulse data" is data for emitting infrared wavelength laser light from semiconductor light source 7 in order to measure the distance to the projection surface of screen 40. Specifically, it 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 update content of the data stored in the data block 22.

[0033] "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 correction for reflectance is enabled, data indicating the corrected laser output value is output, and when 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 emission 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. 4(A) is a cross-sectional view taken along line AA in FIG. 3(B). FIG. 4(B) is a cross-sectional view taken along line BB in FIG. 3(B). In each drawing, the incident mirror 10a and the deflection mirror 10b are shown without hatching to make it easier to see the auxiliary lines used to explain the optical path of the laser light, etc. (The same applies hereinafter). As shown in FIG. 4(A), the incident mirror 10a is positioned upward in the drawing so as not to overlap with the scanning angle range α of the deflection mirror 10b. The laser light emitted from each light-emitting element of the semiconductor light source 6 enters the incident mirror 10a, is reflected by the incident 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 deflection mirror 10b is θ1 relative to the vertical direction shown in the figure, the incident angle of incident light L0 is φ1. In this case, incident light L0 is reflected by deflection mirror 10b and is irradiated as reflected light L1 toward the upper edge of the projection surface of screen 40. When the deflection angle of deflection mirror 10b is θ2 relative to the vertical direction shown in the figure, the incident angle of incident light L0 is φ2. In this case, incident light L0 is reflected by deflection mirror 10b and is irradiated as reflected light L2 toward the lower edge of screen 40. By sequentially changing the deflection angle of deflection mirror 10b, it is possible to scan the laser light in the vertical direction between the upper and lower edges of screen 40.

[0037] As shown in FIG. 4(B), 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] 5(A) is a side view that schematically shows the arrangement of a scanning display system and a screen when trapezoidal distortion occurs. As shown in the figure, when the distances between the light output point P of the scanning display system 100 and the upper and lower edges 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 output point P and the upper edge of the screen 40 is shorter than the distance between the light output point P and the lower edge.

[0040] A schematic front view of the screen 40 is shown in FIG. 5(B). 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 be, for example, the trajectory shown by the dotted line in FIG. 5(C) if no correction is performed. In contrast, if the deflection angle of the deflection mirror 10b is corrected, the trajectory will be the trajectory shown by the solid line in FIG. 5(C). In detail, 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. 5(D).

[0041] FIG. 6 is a cross-sectional view taken along line CC in FIG. 5(D). The symbols (θ1, θ2, φ1, φ2, L0, L1, L2, α) in the figure have the same meanings as those in FIG. 4(A). As shown in FIG. 6, trapezoidal distortion occurs due to a difference between the reflected light L1 irradiated to the upper edge of the screen 40 and the reflected light L2 irradiated to the lower edge of the screen 40, for example. For this reason, 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 DD in Fig. 5(D). Fig. 7(B) is a cross-sectional view taken along line EE in Fig. 5(D). The symbols (θ1, θ2, φ1, φ2, L0, L1, L2, α) in the figure have the same meanings as those in Fig. 4(A) above.

[0043] 7(A) and 7(B), 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 scan line within one frame of an 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] 8(A) to 8(C) are cross-sectional views schematically showing the configuration of a deflection mirror of this embodiment. For ease of explanation, hatching has been omitted. As shown in FIG. 8(A), the deflection mirror 10b of this embodiment includes a substrate 50, a reflective film 51 provided on one surface of the substrate 50, and a reflection-enhancing 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 reflection-enhancing 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 from when the incident light passes through the enhanced reflection film 52 to when it reaches 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 greater than 0° and the incident angle of the incident light is incident angle 2 which is greater 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 undergoes after being reflected by reflective film 51 and before exiting reflection-enhancing film 52 is twice the optical path length of optical path lengths 1 and 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 R, G, and B colors, the tendency for the reflectance to change varies depending on the wavelength of the laser light. Therefore, in this embodiment, in order to suppress the effect of the incident angle dependency of the reflectance of deflection mirror 10b, the output value of the laser light from each light-emitting element of semiconductor light source 6 is variably controlled according to the deflection angle of deflection mirror 10b.

[0048] 9(A) is a diagram showing an example of the relationship between the angle of incidence of light incident on a 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 a 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. 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 of 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 red, green, and blue laser light 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 can cause variations in the irradiation intensity of each laser light on the screen 40. Furthermore, since the target laser output value and reflectance at the deflection mirror 10b differ for each color of laser light, correction must be performed for each color of laser light. Specifically, as shown 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 at a greater rate (slope) as the angle of incidence increases. Therefore, the correction coefficients for each of red and green laser beams increase at a greater rate (slope) as the angle of incidence increases.

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

[0054] For the horizontal scanning line with the largest deflection angle, the laser output value after reflection of the laser light emitted at the 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: 12.625×0.9047=11.422[mW]

[0055] For the horizontal scanning line with the smallest deflection angle, the laser output value after reflection of the laser light emitted at an incident angle of 30° is as follows: Red: 29.159 x 0.9750 = 28.430 [mW] Green: 20.019 x 0.9856 = 19.730 [mW] Blue: 12.625×0.9318=11.763[mW]

[0056] Therefore, the difference between the deflection angle of 30° and the 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 mentioned 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 angles and incident angles. These data tables are correction data obtained by digitizing the graphs shown in FIGS. 9(A) and 9(B). 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 for ease of understanding, the correspondence between deflection angle, incident angle, reflectance, and correction coefficient is shown here. However, 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 this data table, 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] Figure 13 is a flowchart showing the operation procedure of the scanning display system. Note that 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 explicitly shown here can also be added. By repeatedly executing the flow shown in Figure 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 data (see FIG. 11) stored in the data block 22 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 acquires the correction coefficients corresponding to the deflection angles by referring to the data table described above (step S13). Here, the correction coefficient (first correction coefficient) corresponding to the horizontal direction (left-right direction) is designated as X0, and the correction coefficient (second correction coefficient) corresponding to the vertical direction (up-down direction) is designated as 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, that is, 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, this is as follows. Corrected red laser output value = Target red laser output value × (1 + Xr0 + Yr0) Green correction laser output value = Green target 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 an RGB signal based on the corrected laser output value calculated by the overall control block 20, generates laser output data as control data corresponding to the RGB signal, and outputs the generated data to the light source driver 5 (step S17). The light source driver 5 generates a drive signal based on the control data, and the semiconductor light source 6 is driven based on the drive signal. As a result, red, green, and blue laser light 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. Note 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 acquires 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 defined as X1, and the correction coefficient (second correction coefficient) corresponding to the vertical direction (up-down direction) is defined as Y0. The correction coefficient X1 includes correction coefficients Xr1, Xg1, and Xb1 corresponding to each of the RGB colors. Note that 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). The details are as follows. Corrected red laser output value = Target red laser output value × (1 + Xr1 + Yr0) Green correction laser output value = Green target 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, when 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., when 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 acquires 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 defined as X0, and the correction coefficient (second correction coefficient) corresponding to the vertical direction (up-down direction) is defined as Y2. The correction coefficient Y2 includes correction coefficients Yr2, Yg2, and Yb2 corresponding to each of the RGB colors. Note that the correction coefficients X0 (Xr0, Xg0, Xb0) described above are used as the horizontal correction coefficients.

[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, this is done as follows: Corrected red laser output value = Target red laser output value × (1 + Xr0 + Yr2) Green correction laser output value = Green target 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 is present in both the horizontal and vertical directions of the screen 40 (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 acquires the correction coefficients corresponding to the deflection angles by referring to the data table described above (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 changes 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 S27). Here, the corrected laser output value is calculated by multiplying the target laser output value by (1 + X3 + Y3). More specifically, this is as follows: Corrected red laser output value = Target red laser output value × (1 + Xr3 + Yr3) Green correction laser output value = Green target 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. (Appendix 1) A scanning projection system that projects light onto a projection surface by a raster scan method, a light source that emits laser light of at least one visible 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 variably sets an output value of the laser light emitted from the light source and drives the light source; a second driving 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 an output value of the laser light to the first drive circuit, and supplying second control data including a deflection angle of the optical deflector to the second drive circuit; a memory coupled to the controller; Including, the optical deflector has a reflection-enhancing film, 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; 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 scanning line within the same frame, and sets a correction coefficient corresponding to the incident angle determined according to the deflection angle using the correction data read from the memory, and obtains the output value of the laser beam by correcting the target output value using the correction coefficient; Scanning projection system. (Appendix 2) 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. 2. The scanning projection system of claim 1. (Appendix 3) When the projection surface is tilted in the vertical direction, The controller correcting keystone distortion on the projection surface by adjusting the deflection angle with respect to the left-right direction of the projection surface, and setting the first correction coefficient in accordance with the angle of incidence determined in accordance with the deflection angle after adjustment for correcting the keystone distortion; 3. The scanning projection system of claim 2. (Appendix 4) When the projection surface is tilted in the left-right direction, The controller correcting keystone distortion on the projection surface by adjusting the deflection angle with respect to the up-down direction of the projection surface, and setting the second correction coefficient in accordance with the incident angle determined in accordance with the deflection angle after adjustment for correcting the keystone distortion; 3. The scanning projection system of claim 2. (Appendix 5) When the projection surface is tilted in both the vertical direction and the horizontal direction, The controller correcting keystone distortion on the projection surface by adjusting the deflection angle with respect to each of the up-down direction and the left-right direction of the projection surface, and setting the first correction coefficient and the second correction coefficient in accordance with the incident angle determined according to the deflection angle after adjustment for correcting the keystone distortion; 3. The scanning projection system of claim 2. (Appendix 6) the light source emits three laser beams corresponding to three primary colors; the controller sets the correction coefficients individually for each of the three laser beams. A scanning projection system according to any one of appendices 1 to 5. (Appendix 7) The light projected onto the projection surface constitutes an image. A scanning projection system according to any one of appendices 1 to 6. (Appendix 8) The light projected onto the projection surface constitutes illumination light. A scanning projection system according to any one of appendices 1 to 6. (Appendix 9) a distance measurement unit that measures distances to a plurality of positions on the projection surface; the controller determines the tilt of the projection plane based on the distances to the plurality of positions measured by the distance measurement unit; 9. A scanning projection system according to any one of appendices 1 to 8. [Explanation of symbols]

[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: High reflection film, 100: Scanning display system

Claims

1. A scanning projection system that projects light onto a projection surface by a raster scan method, a light source that emits laser light of at least one visible 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 variably sets an output value of the laser light emitted from the light source and drives the light source; a second driving 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 an output value of the laser light to the first drive circuit, and supplying second control data including a deflection angle of the optical deflector to the second drive circuit; a memory coupled to the controller; Including, the optical deflector has a reflection-enhancing film, 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; 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 scanning line within the same frame, and sets a correction coefficient corresponding to the incident angle determined according to the deflection angle using the correction data read from the memory, and obtains the output value of the laser beam by correcting the target output value using the correction coefficient; Scanning projection system.

2. 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.

10. The scanning projection system of claim 1.

3. When the projection surface is tilted in the vertical direction, The controller correcting keystone distortion on the projection surface by adjusting the deflection angle with respect to the left-right direction of the projection surface, and setting the first correction coefficient in accordance with the angle of incidence determined in accordance with the deflection angle after adjustment for correcting the keystone distortion; 3. The scanning projection system of claim 2.

4. When the projection surface is tilted in the left-right direction, The controller correcting keystone distortion on the projection surface by adjusting the deflection angle with respect to the up-down direction of the projection surface, and setting the second correction coefficient in accordance with the incident angle determined in accordance with the deflection angle after adjustment for correcting the keystone distortion; 3. The scanning projection system of claim 2.

5. When the projection surface is tilted in both the vertical direction and the horizontal direction, The controller correcting keystone distortion on the projection surface by adjusting the deflection angle with respect to each of the up-down direction and the left-right direction of the projection surface, and setting the first correction coefficient and the second correction coefficient in accordance with the incident angle determined in accordance with the deflection angle after adjustment for correcting the keystone distortion; 3. The scanning projection system of claim 2.

6. the light source emits three laser beams corresponding to three primary colors; the controller sets the correction coefficients individually for each of the three laser beams.

2. The scanning projection system of claim 1

7. The light projected onto the projection surface constitutes an image.

2. The scanning projection system of claim 1

8. The light projected onto the projection surface constitutes illumination light.

2. The scanning projection system of claim 1

9. a distance measurement unit that measures distances to a plurality of positions on the projection surface; the controller determines the tilt of the projection plane based on the distances to the plurality of positions measured by the distance measurement unit; 10. The scanning projection system of claim 1.

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