Image projection device

Abstract

To provide an image projection device that enhances the visibility of projected content without wasting a light amount of the image projection device.SOLUTION: An image projection device 1 that projects image light onto a projection surface S comprises a light source 11 that emits light, a spatial phase modulator 13 that modulates incident light from the light source 11 to form image light, a control unit 15 that controls the spatial phase modulator 13 to form the image light on the basis of a phase-type computer-generated hologram, and a camera 14 that captures the projection surface S or a projected image. The control unit 15 includes correction means that corrects the image light on the basis of a captured image of the camera 14. The correction means changes the light amount distribution of the image light by means of the phase-type computer-generated hologram.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an image projection device. [Background technology]

[0002] Image projection devices that project image light onto a projection surface are known (see, for example, Patent Documents 1 and 2). In recent years, road projectors that are mounted on vehicles and project image light onto the road surface have also been proposed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-212917 [Patent Document 2] Patent No. 5119607 Summary of the Invention [Problem to be solved by the invention]

[0004] When a road projector projects content such as an arrow onto the road surface, if the content crosses over white lines on the road, differences in reflectivity will cause uneven brightness (see Figure 3(a)), reducing the visibility of the content.

[0005] Therefore, Patent Documents 1 and 2 propose a method of using a camera to capture the projection surface or the projected image, and correcting the image light based on the captured image so that the brightness of the projected content is uniform. However, this conventional method reduces the amount of light emitted from the high-brightness side to match the low-brightness side, which means that the amount of light available in the image projection device cannot be fully utilized, resulting in the overall projected content being dark.

[0006] Therefore, an object of the present disclosure is to provide an image projection device that can improve the visibility of projected content without wasting the amount of light that the image projection device has. [Means for solving the problem]

[0007] In one aspect, the following solution is provided. An image projection device that projects image light onto a projection surface, comprising: A light source that emits light; a spatial phase modulator that modulates incident light from the light source to form the image light; a control unit that controls the spatial phase modulator to form the image light based on a phase-type computer-generated hologram; a camera that captures the projection surface or the projected image, the control unit includes a correction unit that corrects the image light based on the image captured by the camera, The correcting means changes the light intensity distribution of the image light by the phase-type computer-generated hologram. [Effects of the Invention]

[0008] According to the present disclosure, the visibility of projected content can be improved without wasting the amount of light available in the image projection device. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic side view of a vehicle equipped with an image projection device according to an embodiment of the present invention; [Figure 2] FIG. 1 is a schematic diagram illustrating a configuration of an image projection device. [Figure 3] 10A and 10B are diagrams showing content projected onto the road surface, in which (a) is a diagram showing the content before correction, (b) is a diagram showing the content after correction by the conventional technology, and (c) is a diagram showing the content after correction by the first embodiment. [Figure 4] 5 is a flowchart showing the processing procedure of brightness correction processing according to the first embodiment. [Figure 5] FIG. 10 is a diagram showing content projected onto a road surface after correction according to a second embodiment. [Figure 6] 10 is a flowchart showing a processing procedure for brightness correction processing according to a second embodiment. [Figure 7] 10A and 10B are diagrams showing content projected onto a road surface, in which FIG. 10A shows the content after correction according to the third embodiment, and FIG. 10B shows the content after correction according to a modified example of the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Each embodiment will be described in detail below with reference to the accompanying drawings. Note that in the drawings, for ease of viewing, only some of the reference symbols may be used for multiple components with the same attribute.

[0011] [Image projection device] FIG. 1 is a schematic side view of a vehicle V equipped with an image projection device 1 according to this embodiment. As shown in FIG. 1, the image projection device 1 of this embodiment is mounted on the front end (bumper, etc.) of a vehicle V, and functions as a road projector that projects image light onto the road surface (projection surface S) in front of the vehicle V by emitting image light from the front end of the vehicle V onto the road surface in front of the vehicle V.

[0012] In this embodiment, arrows Y1 to Y4 (see Figures 3, 5, and 7) are shown as examples of content of a predetermined shape projected onto the projection surface S using image light, but the content may also be symbols other than arrows, or letters, etc.

[0013] FIG. 2 is a schematic diagram showing the configuration of the image projection device 1. As shown in FIG. As shown in FIG. 2, the image projection device 1 includes a light source 11, a collimator lens 12, a spatial phase modulator 13, a camera 14, and a control unit 15.

[0014] The light source 11 outputs light of a predetermined wavelength. For example, the light source 11 includes an LD (laser diode) that emits laser light.

[0015] The collimator lens 12 converts the output light of the light source 11 into parallel light and makes it incident on the spatial phase modulator 13 .

[0016] The spatial phase modulator 13 modulates incident light (incident light) to form image light. The spatial phase modulator 13 operates under the control of the above-mentioned control unit 15. For example, an LCOS-SLM (Liquid Crystal on Silicon-Spatial Light Modulator) is used as the spatial phase modulator 13.

[0017] The light emitted from the spatial phase modulator 13 is projected onto the projection surface S as content in the form of image light.

[0018] The camera 14 captures the projection surface S or the image projected onto the projection surface S.

[0019] The control unit 15 controls the spatial phase modulator 13 to form image light based on a computer-generated hologram (CGH). Computer-generated holograms are classified into phase and amplitude types, and a phase-type computer-generated hologram is applied to the image projection device 1 of the present invention. The phase-type computer-generated hologram makes it possible to change the light intensity distribution of the image light without wasting the light intensity held by the image projection device 1.

[0020] Furthermore, the control unit 15 executes a light amount correction process (correction means) that corrects image light based on the image captured by the camera 14. The light amount correction process performed by the control unit 15 will be described below.

[0021] [First Example] Figure 3 shows content projected onto the road surface (projection surface S), where (a) shows the content before correction, (b) shows the content after correction using conventional technology, and (c) shows the content after correction using the first embodiment. As shown in (a) of Figure 3, when content such as an arrow Y1 is projected onto a road surface, which is the projection surface S, if the content is projected across a white line L on the road surface, uneven brightness occurs due to differences in reflectivity. In other words, the brightness of the content projected onto the road surface will be low on asphalt A, which has low reflectivity, and high on white line L, which has high reflectivity.

[0022] To address this issue, a method has been proposed in which the projection surface S or the projected image is photographed by a camera 14, and the image light is corrected based on the photographed image by the camera 14 so that the brightness of the projected content is uniform. However, with this method, as shown in Figure 3(b), the amount of light emitted from the high-brightness side is reduced to match the low-brightness side (asphalt A side), which means that the amount of light available in the image projection device 1 cannot be fully utilized, and the entire projected content becomes dark.

[0023] Therefore, when correcting the image light based on the image captured by camera 14, control unit 15 of the present invention changes the light intensity distribution of the image light using a phase-based computer-generated hologram. In other words, a phase-based computer-generated hologram can change the light intensity distribution of the image light within the content rendering area without wasting the light intensity of image projection device 1, thereby preventing the entire projected content from becoming dark due to the correction. For example, in FIG. 3(a), the light intensity of the high-luminance portion of arrow Y1 (the portion on white line L) is distributed to the low-luminance portion (the portion on asphalt A). This light intensity correction process using a phase-based computer-generated hologram makes it possible to project an arrow Y1 with uniform brightness onto the road surface, as shown in FIG. 3(c), while preventing the entire projected arrow Y1 from becoming dark due to the correction.

[0024] Next, a specific processing procedure of the control unit 15 that realizes the above-described light quantity correction processing will be described with reference to Fig. 4. Fig. 4 shows an example of a processing procedure when analyzing a road surface image (camera image) before projecting content and correcting the light quantity distribution of image light according to the analysis result.

[0025] As shown in FIG. 4, when projecting content onto a road surface, the control unit 15 first acquires a camera image of the road surface that will become the projection surface S before projecting the content, and analyzes the color and characteristics of the projection surface S from the camera image (S11).

[0026] The control unit 15 determines whether there is uniformity in the color and characteristics of the entire projection surface S (S12), and if the result of this determination is YES, it projects the content without correcting the light intensity distribution of the image light (S13).

[0027] If the determination result in step S12 is NO, the control unit 15 distributes the amount of light within the drawing area so that the content has uniform brightness when projected onto the road surface (increasing the amount of light for the part of the content on the asphalt A and decreasing the amount of light for the part on the white line L; for example, changing the amount of light from A:L=50:50 to A:L=75:25) (S14), and then projects the content (S13).

[0028] [Second Example] Next, a second embodiment of the present invention will be described with reference to Figures 5 and 6. However, for parts common to the first embodiment, the same reference numerals as in the first embodiment will be used, and the description of the first embodiment may be used.

[0029] FIG. 5 is a diagram showing content projected onto the road surface after correction according to the second embodiment. In a second embodiment of the present invention, when projecting content onto the projection surface S, if there is a possibility that the brightness of the content projected onto the projection surface S will fall below a predetermined brightness, the light intensity distribution of the image light is changed so that the drawing area of ​​the content becomes narrower. For example, as shown in FIG. 5, the drawing size of the content is reduced (arrow Y1 is changed to arrow Y2, which is smaller).

[0030] According to the second embodiment, by utilizing the characteristic of phase-type computer-generated holograms that the brightness of content increases when the drawing size of the content is reduced, it is possible to ensure the brightness required for the content and improve the visibility of the content.

[0031] Furthermore, in the second embodiment, the image light is corrected so that the content moves in a predetermined direction (for example, the direction indicated by the arrow Y2) within the drawing range, which can further improve the visibility of the content.

[0032] Next, a specific processing procedure of the control unit 15 in the second embodiment will be described with reference to Fig. 6. Fig. 6 shows an example of the processing procedure when analyzing a road surface image (camera image) after projecting content and correcting the light intensity distribution of image light according to the analysis result.

[0033] As shown in FIG. 6, after projecting content onto the road surface (S21), control unit 15 acquires a camera image of the road surface onto which the content is projected, and analyzes the luminance distribution of the projected content from the camera image (S22).

[0034] The control unit 15 determines whether or not there is uniformity in the brightness of the entire content (S23), and if the result of this determination is NO, changes the light quantity distribution of the image light so that the brightness on the low-brightness side becomes higher (S24), and returns to step S22.

[0035] If the determination result in step S23 is YES, the control unit 15 determines whether the brightness of the content is lower than the lower limit of the visibility reference value (S25), and if the determination result is YES, reduces the drawing size of the projected content (S26). The visibility reference value is a set value that defines the brightness range in which the projected content is easy to see. However, the visibility of the content may be determined not only based on the brightness of the projected content but also on the surrounding environment, such as the brightness of the surrounding area.

[0036] If the determination result in step S25 is NO, the control unit 15 determines whether the brightness of the content is higher than the upper limit of the visibility reference value (S27), and if the determination result is YES, reduces the output of the light source 11 (S28).

[0037] [Third Example] Next, a third embodiment of the present invention and its modified example will be described with reference to Fig. 7. However, for parts common to the first embodiment, the same reference numerals as in the first embodiment will be used, and the description of the first embodiment may be used.

[0038] FIG. 7 shows content projected onto the road surface, where (a) shows the content after correction according to the third embodiment, and (b) shows the content after correction according to a modified example of the third embodiment. In a third embodiment of the present invention, when projecting content onto a projection surface S, if there is a possibility that the brightness of the content projected onto the projection surface S will fall below a predetermined brightness, the light intensity distribution of the image light is changed to narrow the drawing area of ​​the content. This is similar to the second embodiment, but in the third embodiment, as shown in FIG. 7, hollow portions Y3a and Y4a are provided in the content without changing the drawing size of the content. For example, in the third embodiment shown in FIG. 7(a), the arrow Y1 is changed to an arrow Y3 drawn with only a border. Furthermore, in a modified version of the third embodiment shown in FIG. 7(b), the arrow Y1 is changed to an arrow Y4 drawn with a border and hatching.

[0039] According to the third embodiment and its variants, by utilizing the characteristic of phase-type computer-generated holograms that the brightness of the content increases when the ratio of the irradiation area to the drawable range of the content is reduced, it is possible to ensure the brightness required for the content and improve the visibility of the content.

[0040] Although the embodiments have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the claims. Furthermore, it is also possible to combine all or a plurality of components of the above-described embodiments. [Explanation of symbols]

[0041] 1. Image projection device 11 Light source 12 Collimating lens 13 Spatial Phase Modulator 14 Camera 15 Control Unit

Claims

1. An image projection device that projects image light onto a projection surface, comprising: A light source that emits light; a spatial phase modulator that modulates incident light from the light source to form the image light; a control unit that controls the spatial phase modulator to form the image light based on a phase-type computer-generated hologram; a camera that captures the projection surface or the projected image, the control unit includes a correction unit that corrects the image light based on the image captured by the camera, The correction means changes the light intensity distribution of the image light by the phase-type computer-generated hologram.

2. 2. The image projection device of claim 1, wherein the correction means changes the light intensity distribution of the image light within the drawing area of ​​the content so that the content projected on the projection surface has uniform brightness when projecting content of a predetermined shape onto the projection surface using the image light.

3. 3. The image projection device according to claim 2, wherein said correction means distributes the amount of light from a portion with high brightness within a drawing area of ​​said content to a portion with low brightness.

4. The image projection device of claim 1, wherein when projecting content of a predetermined shape onto the projection surface using the image light, if there is a possibility that the brightness of the content projected onto the projection surface will fall below a predetermined brightness, the correction means changes the light intensity distribution of the image light so that the drawing area of ​​the content becomes narrower.

5. 5. The image projection device according to claim 4, wherein the correction means reduces the drawing size of the content.

6. 5. The image projection device according to claim 4, wherein the correction means provides a hollow portion in the content without changing the drawing size of the content.

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