A method of measuring the field of view of a projection screen

Abstract

The application discloses a kind of field of view angle measurement methods of projection screen, by placing test box on the set position on projection screen;Test box includes light shielding shell, at least a part of the side of light shielding shell exists gap with projection screen, diffusion sheet is arranged in light shielding shell, two-dimensional brightness meter is installed in the end of light shielding shell away from projection screen;Control projection equipment and form tiny light spot on projection screen by test light ray that test box and projection screen gap emit to projection screen;Control two-dimensional brightness meter to measure the brightness distribution of light spot that tiny light spot projects on diffusion sheet;According to the brightness distribution of measurement, determine the field of view angle of projection screen in set position.Thus only need to place the test box of simple structure in the measured position of projection screen, can determine the field of view angle of this position by measuring the brightness distribution of light spot projected on the diffusion sheet in test box.

Description

Technical Field

[0001] This invention relates to the field of projection technology, and in particular to a method for measuring the field of view of a projection screen. Background Technology

[0002] As display products continue to trend towards larger sizes, considering factors such as power consumption, weight, and size, the market for projection displays as large-screen alternatives to LCD and OLED (Electroluminescent, EL) televisions is rapidly expanding. Current front-projection systems typically work in conjunction with a projection screen. The projector emits projection light, which strikes the screen, is reflected, and then reaches the viewer's eyes to produce the projected image. Therefore, evaluating the luminous intensity distribution and field of view within the projection screen's radiation angle is crucial for designing the screen to achieve the desired effect.

[0003] Current methods for measuring the field of view of a projection screen involve placing a detection device on a circle at a certain distance from a light-emitting point on the screen and measuring the brightness of that point from various directions to determine the field of view. This method requires moving the detection device while measuring, and detailed measurements in the angular direction are time-consuming. Furthermore, the reproducibility of the measurements can sometimes be problematic due to the movement of the device. Additionally, measuring the field of view in the vertical direction typically requires moving a large, heavy detection device significantly in the vertical direction, which presents considerable difficulties. Summary of the Invention

[0004] In some embodiments of the present invention, the method for measuring the field of view of a projection screen includes:

[0005] A test box is placed at a predetermined position on the projection screen; the test box includes a light-shielding shell, at least a portion of the side of the light-shielding shell is separated from the projection screen, a diffuser is provided in the light-shielding shell, and a two-dimensional luminance meter is installed at the end of the light-shielding shell away from the projection screen.

[0006] The control projection device emits test light through the gap between the test box and the projection screen, forming tiny light spots on the projection screen;

[0007] The two-dimensional luminance meter is controlled to measure the luminance distribution of the light spot generated by the tiny light spot projected onto the diffuser sheet;

[0008] The field of view of the projection screen at the set position is determined based on the measured brightness distribution.

[0009] In some embodiments of the present invention, the size of the tiny light spot satisfies the following relationship:

[0010] a <d×tan(10°);

[0011] Where a represents the size of the tiny light spot, and d represents the distance between the diffuser and the projection screen.

[0012] In some embodiments of the present invention, the diffuser sheet is disposed parallel to the projection screen, and the distance between the diffuser sheet and the projection screen satisfies the following relationship:

[0013]

[0014] Where d represents the distance between the diffuser and the projection screen, θ' represents the effective field of view of the tiny light spot in the set direction, and b represents the size of the diffuser in the set direction; the effective field of view is the field of view corresponding to the half-peak and half-width of the brightness of the light spot generated on the diffuser in the set direction.

[0015] In some embodiments of the present invention, the distance between the two-dimensional luminance meter and the diffuser is 100mm to 200mm.

[0016] In some embodiments of the present invention, determining the field of view of the projection screen at the set position based on the measured brightness distribution includes:

[0017] The half-peak and half-width of the light spot on the diffuser in the horizontal and vertical directions are determined based on the measured brightness distribution.

[0018] The effective field of view of the projection screen at the set position is determined based on the half-peak and half-width of the brightness of the light spot on the diffuser in the horizontal and vertical directions, and the distance between the diffuser and the projection screen.

[0019] In some embodiments of the present invention, before determining the half-peak and half-width of the brightness of the light spot on the diffuser in the horizontal and vertical directions based on the measured brightness distribution, the method further includes:

[0020] Remove the diffuser from the test box and control the two-dimensional luminance meter to directly measure the position of the tiny light spot on the projection screen;

[0021] The position of the center of the light spot on the diffuser is corrected according to the position of the tiny light spot;

[0022] The step of determining the half-peak and half-width of the brightness of the light spot on the diffuser in the horizontal and vertical directions based on the measured brightness distribution includes:

[0023] Based on the corrected center position of the light spot and the measured brightness distribution, the half-peak and half-width of the brightness of the light spot on the diffuser in the horizontal and vertical directions are determined respectively.

[0024] In some embodiments of the present invention, the diffuser is a permeable Lambertian diffuser; the measurement method further includes:

[0025] The luminous intensity distribution of the tiny light spot on the projection screen at different radiation angles is determined based on the measured brightness distribution;

[0026] The radiation angle and luminous intensity from the tiny light spot satisfy the following relationship:

[0027]

[0028]

[0029]

[0030] in, This indicates that the tiny light spot is in spherical coordinates. The luminous intensity in the direction, B(X,Y) represents the brightness at position (X,Y) on the diffuser, d represents the distance between the diffuser and the projection screen, and Gain represents the gain of the diffuser.

[0031] In some embodiments of the present invention, the projection screen includes a Fresnel structure, which is used to receive the projection light emitted from the projection device and reflect it in a predetermined direction; the measurement method further includes:

[0032] The radiation angle corresponding to the peak luminous intensity is determined based on the luminous intensity distribution of the tiny light spot at different radiation angles;

[0033] The Fresnel structure of the projection screen is evaluated based on the determined radiation angle.

[0034] In some embodiments of the present invention, the test box is mounted on a bracket, the bracket comprising: a first track and a second track; the first track is fixed to the top of the projection screen, one end of the second track is slidably connected to the first track, and the test box is slidably connected to the second track;

[0035] Placing the test box at a predetermined position on the projection screen includes:

[0036] Slide the test box and the second track to move the test box to the set position on the projection screen.

[0037] In some embodiments of the present invention, there are multiple designated positions on the projection screen. The projection screen is divided into three equal parts along the horizontal and vertical directions to form nine regions, and the designated positions are the center positions of the nine regions. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the projection system provided in an embodiment of the present invention;

[0040] Figure 2 This is one of the schematic diagrams of the test principle provided in the embodiments of the present invention;

[0041] Figure 3 One of the flowcharts for measuring the field of view of a projection screen according to an embodiment of the present invention;

[0042] Figure 4 This is a schematic diagram of the planar structure of the diffuser sheet provided in an embodiment of the present invention;

[0043] Figure 5 A schematic diagram of the measurement spot of the two-dimensional luminance meter provided in this embodiment of the invention;

[0044] Figure 6 The brightness curve obtained based on the brightness distribution is provided in the embodiment of the present invention;

[0045] Figure 7 A second flowchart of a method for measuring the field of view of a projection screen provided in an embodiment of the present invention;

[0046] Figure 8 This is the second schematic diagram of the test principle provided in the embodiment of the present invention;

[0047] Figure 9 The third schematic diagram of the test principle provided in the embodiment of the present invention;

[0048] Figure 10 The fourth schematic diagram of the test principle provided in the embodiments of the present invention;

[0049] Figure 11 This is a schematic diagram of the Fresnel structure provided in an embodiment of the present invention;

[0050] Figure 12 Fifth schematic diagram of the test principle provided in the embodiments of the present invention;

[0051] Figure 13 This is a schematic diagram of the test location provided in an embodiment of the present invention. Detailed Implementation

[0052] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. However, the exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to make the present invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the figures denote the same or similar structures, and therefore repeated descriptions of them will be omitted. Terms describing position and direction in the present invention are illustrative based on the accompanying drawings, but changes can be made as needed, and all such changes are included within the scope of protection of the present invention. The accompanying drawings of the present invention are for illustrative purposes only and do not represent actual proportions.

[0053] With the increasing popularity of laser display products, the market for laser TVs, as a large-screen alternative to LCD and OLED TVs, is rapidly expanding. To achieve better brightness and display effects, projection devices are generally used in conjunction with projection screens.

[0054] Figure 1 This is a schematic diagram of the projection system provided in an embodiment of the present invention.

[0055] like Figure 1 As shown, the projection system includes: a projection device 2 and a projection screen 1.

[0056] The projection screen 1 is located on the light-emitting side of the projection device 2. The audience faces the projection screen 1. The projection device 2 emits projection light, which enters the projection screen 1 and is reflected forward through the projection screen 1, so that the audience can see the projected image.

[0057] Ultra-short-throw projection devices have the characteristics of short projection distance and large projection screen, making them very suitable for home use. The projection system provided in this embodiment of the invention can use an ultra-short-throw projection device.

[0058] In this embodiment of the invention, the projection screen is a reflective screen. The projection light emitted from the projection device 2 is incident on the projection screen 1 and reflected by the screen, so that viewers facing the screen can see the projected image. When designing the projection screen 1, the field of view needs to be considered. The field of view determines the viewer's visible range, i.e., the position from which the viewer can see the displayed image. The intensity distribution of reflected light within the field of view determines the brightness of the image seen by the viewer within that range, thus affecting the image quality of the projected image.

[0059] Current methods for measuring the field of view of a projection screen involve placing a detection device on a circle at a certain distance from a light-emitting point on the screen and measuring the brightness of that point from various directions to determine the field of view. This method requires moving the detection device while measuring, and detailed measurements in the angular direction are time-consuming. Furthermore, the reproducibility of the measurements can sometimes be problematic due to the movement of the device. Additionally, measuring the field of view in the vertical direction typically requires moving a large, heavy detection device significantly in the vertical direction, which presents considerable difficulties.

[0060] In view of this, embodiments of the present invention provide a method for measuring the field of view of a projection screen. It only requires placing a simple test box at the test position on the projection screen, and the field of view at that position can be determined by measuring the brightness distribution of the light spot projected onto the diffuser in the test box.

[0061] Figure 2 This is one of the schematic diagrams of the test principle provided in the embodiments of the present invention.

[0062] like Figure 2 As shown, when measuring the field of view of the projection screen, the test box 3 can be placed at the location where the measurement is needed. The test box 3 is an integrated structure, including a light-shielding housing 31, a diffuser 32, and a two-dimensional luminance meter 33.

[0063] like Figure 2 As shown, at least a portion of the side of the light-shielding housing 31 has a gap with the projection screen. The projection device 2 typically emits projection light from below the projection screen 1. In this embodiment of the invention, the light-shielding housing 31 can be designed as a cuboid, and at least a portion of its lower side has a gap with the projection screen 1. This gap is used to allow the projection device 2 to project projection light onto the projection screen 1 through the gap.

[0064] The light-shielding housing 31 is also equipped with a diffuser 32, which is positioned at a certain distance from the projection screen 1. After receiving the projected light, the projection screen 1 reflects the light back onto the diffuser 32, thus creating a light spot on the diffuser 32. The function of the diffuser 32 is to convert the light intensity information of the reflected light from the projection screen 1 at different radiation angles into the brightness information of the light spot generated on the diffuser 32. Thus, by measuring the brightness distribution on the diffuser 32, the radiation angle information of the tiny light spot can be obtained. A two-dimensional luminance meter 33 is installed at the end of the light-shielding housing 31 furthest from the projection screen 1. The two-dimensional luminance meter 33 can measure the two-dimensional brightness distribution of the light spot generated on the diffuser 32.

[0065] like Figure 2As shown, if the light emitted from the projection device 2 onto the projection screen 1 produces a tiny light spot B1 on the projection screen 1, the projection screen 1 will reflect the light emitted from the projection device 2 towards the diffuser 32. Therefore, this can be considered as the tiny light spot B1 emitting light towards one side of the diffuser 32, thus producing a light spot B2 on the diffuser 32. The radiation angle range of the emitted light from the tiny light spot B1 is then the field of view angle of the projection screen 1 at the position of the tiny light spot B1. Figure 2 As shown, if the radiation angle of the emitted light from the tiny light spot B1 is ±θ, then the radius of the light spot B2 generated on the diffuser 32 is r. When the diffuser 32 and the projection screen 1 are set parallel to each other and the distance between the diffuser 32 and the projection screen 1 is d, the following conditions are met:

[0066]

[0067] Therefore, by measuring the size of the light spot r generated on the diffuser 32, the field of view θ = tanθ of the projection screen at the set position can be calculated based on the above relationship. -1 (r / d).

[0068] Based on the above principles, embodiments of the present invention provide a method for measuring the field of view of a projection screen. Figure 3 This is one of the flowcharts for a method of measuring the field of view of a projection screen provided in an embodiment of the present invention.

[0069] like Figure 3 As shown, the method for measuring the field of view of the projection screen includes:

[0070] S10. Place the test box at the designated position on the projection screen;

[0071] S20. Control the projection device to emit test light through the gap between the test box and the projection screen to form a tiny light spot on the projection screen;

[0072] S30. Control the two-dimensional luminance meter to measure the luminance distribution of the light spot generated by the projection of a tiny light spot onto the diffuser sheet;

[0073] S40. Determine the field of view of the projection screen at the set position based on the measured brightness distribution.

[0074] Reference Figure 2 The test box 3 set on the projection screen 1 is an integrated structure. In order to improve the accuracy of the measurement results, the size of each component in the test box 3 and the distance between each component need to be reasonably designed.

[0075] First, the diffuser 32 in test box 3 needs to be at a certain distance d from the projection screen 1. This is because the light reflected by the projection screen 1 diffuses within a range corresponding to its radiation angle ±θ according to a certain radiation law, producing a light spot with a set pattern on the diffuser 32. As the distance d between the diffuser 32 and the projection screen 1 decreases, the radius r = d × tanθ of the light spot on the diffuser 32 also decreases. Finally, when d = 0, the light spot on the diffuser 32 becomes a tiny light spot B1 of the same size as the one on the projection screen, and it is impossible to obtain information about the emission angle of this tiny light spot B1. At this time, the two-dimensional luminance meter 33 can only capture a bright spot and cannot obtain information about the distribution of the emission angle.

[0076] When designing the test box 3, the distance d between the diffuser 32 and the projection screen 1 is determined by the relationship between the radius r of the light spot generated on the diffuser 32 and the size of the diffuser 32 that the two-dimensional luminance meter 33 needs to measure. The smaller the distance d between the diffuser 32 and the projection screen 1, the larger the radiation angle range of the tiny light spot B1 that can be measured will be, but the sensitivity of the test will be reduced, and it will be difficult to test tiny changes in angle.

[0077] It should be noted that, compared to the entire field of view of the projection screen, more attention is often paid to the field of view range where the brightness of the projection screen is more concentrated in certain directions. In this embodiment of the invention, the field of view angle corresponding to the half-peak and half-width of the brightness of the spot B2 generated by the projection of the tiny spot B1 on the projection screen onto the diffuser 32 is defined as the effective field of view angle of the projection screen at the location of the tiny spot. The light reflected by the projection screen is more concentrated within the effective field of view angle, allowing viewers to see a bright and clear image within this range. When the effective field of view angle is exceeded, the brightness of the projected image decreases significantly, and the viewing experience deteriorates.

[0078] When the diffuser 32 is set parallel to the projection screen 1, the distance d between the diffuser 32 and the projection screen 1 satisfies the following relationship:

[0079]

[0080] Where d represents the distance between the diffuser 32 and the projection screen 1, θ' represents the effective field of view of the tiny light spot B1 in the set direction, and b represents the size of the diffuser 32 in the set direction.

[0081] For example, assuming the effective field of view of the projection screen 1 under test is ±30° and the size of the diffuser 32 is 100mm×100mm, then d<87mm can be calculated based on 100 / 2>d×tan30°. In practical applications, the distance d between the diffuser 32 and the projection screen 1 can be designed to be about 30% to 100% of the diffuser size, and is not limited here.

[0082] Furthermore, the field-of-view measurement method provided in this embodiment of the invention requires light to be emitted from the projection device 2 onto the projection screen 1, thereby generating a tiny light spot B1 on the projection screen 1. The size of this tiny light spot B1 affects the clarity of the brightness distribution on the diffuser. The smaller the size of the tiny light spot B1, the less light is reflected, resulting in a darker light spot pattern on the diffuser 32. This increases the measurement time required by the two-dimensional luminance meter 33, increases noise, and makes accurate measurement difficult. However, the larger the size of the tiny light spot B1, the lower the resolution of the light spot pattern obtained on the diffuser 32.

[0083] In this embodiment of the invention, the size of the tiny light spot B1 satisfies the following relationship, and the brightness is as bright as possible:

[0084] a <d×tan(10°);

[0085] Where a represents the size of the tiny light spot B1, and d represents the distance between the diffuser 32 and the projection screen 1.

[0086] For example, if the distance d between the diffuser 32 and the projection screen 1 is 70 mm, then while maintaining a blur within 1°, the size of the tiny light spot B1 formed on the projection screen 1 should be less than 70 × tan1° = 1.2 mm. Alternatively, while maintaining a blur within 10°, the size of the tiny light spot B1 should be less than 70 × tan10° = 12 mm.

[0087] Figure 4 This is a schematic diagram of the planar structure of the diffuser sheet provided in an embodiment of the present invention.

[0088] like Figure 4 As shown, the diffuser 32 is disposed inside the light-shielding housing 31. The diffuser 32 can typically be square or rectangular, and correspondingly, the cross-section of the light-shielding housing 31 is also square or rectangular. The light-shielding housing 31 may have a strip-shaped opening on its side, so that the diffuser 32 can be inserted into or removed from the light-shielding housing 31 through the strip-shaped opening.

[0089] A mark m can be set at the center of the diffuser 32, which is the intersection of the optical axis of the two-dimensional luminance meter 33 and the diffuser 32. When the tiny light spot B1 is projected onto the projection screen 1 at the intersection of the optical axis of the two-dimensional luminance meter 33, if the reflected light passes through the mark m, the incident angle of the reflected light onto the diffuser 32 is 0°.

[0090] like Figure 2As shown, both the two-dimensional luminance meter 33 and the diffuser 32 are fixed on the light-shielding housing 31, and the two-dimensional luminance meter 33 and the diffuser 32 are separated by a certain distance L, so that the two-dimensional luminance meter 33 can measure the entire light spot pattern on the diffuser 32. When designing the test box, the distance L between the two-dimensional luminance meter 33 and the diffuser 32 can be 100mm to 200mm, which is not limited here.

[0091] After designing the test box 3 with the above structure and installing the test box 3 at the set position to be measured on the projection screen, the projection device 2 can be controlled to emit projection light to the set position on the projection screen 1 to generate a small light spot B1 at the set position. At the same time, the two-dimensional brightness meter 33 is controlled to measure the light spot B2 generated on the diffuser 32, thereby obtaining the brightness distribution of the light spot B2 on the diffuser 32.

[0092] Figure 5 This is a schematic diagram of the measurement spot of a two-dimensional luminance meter provided in an embodiment of the present invention. Figure 6 The brightness curve obtained based on the brightness distribution is provided in the embodiment of the present invention.

[0093] The two-dimensional luminance meter 33 can measure the luminance distribution of the light spot generated on the diffuser 32, and the measurement results are as follows: Figure 5 As shown. Based on this brightness distribution, the brightness value of each point on the diffuser 32 can be determined, and the following can also be obtained: Figure 6 The brightness curve shown. From Figure 5 and Figure 6 The measurement results can yield the location of the peak brightness, and the half-peak half-width HWHM, which is the distance on the diffuser at the location where the brightness value is half of the maximum brightness. In this embodiment of the invention, the half-peak half-width HWHM, which is the distance on the diffuser, is substituted into the formula θ = tan -1 The r of (r / d) can be used to determine the effective field of view of the projection screen at the set position.

[0094] In practice, the brightness distribution of the light spot on the diffuser 32 can be measured to determine the half-peak and half-width of the brightness of the light spot in the horizontal and vertical directions, thereby determining the effective field of view of the projection screen in the horizontal and vertical directions.

[0095] Before obtaining the half-peak and half-width of the brightness of the light spot on the diffuser in the horizontal and vertical directions, it is necessary to determine whether the center of the light spot measured by the two-dimensional luminance meter 33 deviates from the central optical axis of the two-dimensional luminance meter 33. When the center of the light spot on the diffuser 32 does not deviate from the central optical axis of the two-dimensional luminance meter 33, the effective field of view in the horizontal and vertical directions can be determined directly using the above method. When the center of the light spot on the diffuser 32 deviates from the central optical axis of the two-dimensional luminance meter 33, the position of the center of the light spot needs to be corrected first, and then the half-peak and half-width of the brightness of the light spot on the diffuser in the horizontal and vertical directions is determined by the corrected position of the center of the light spot, thereby determining the effective field of view in the horizontal and vertical directions.

[0096] Figure 7 The second flowchart illustrates the method for measuring the field of view of a projection screen as provided in an embodiment of the present invention.

[0097] like Figure 7 As shown, in step S40, determining the field of view of the projection screen at the set position based on the measured brightness distribution specifically includes:

[0098] S401. Remove the diffuser in the test box and control the two-dimensional luminance meter to directly measure the position of the tiny light spot on the projection screen;

[0099] S402. Correct the center position of the light spot on the diffuser sheet according to the position of the tiny light spot;

[0100] S403. Determine the half-peak and half-width of the brightness of the light spot on the diffuser in the horizontal and vertical directions, respectively, based on the corrected center position of the light spot and the measured brightness distribution.

[0101] S404. Determine the effective field of view of the projection screen in the horizontal and vertical directions at the set position based on the half-peak and half-width of the brightness of the light spot on the diffuser in the horizontal and vertical directions and the distance between the diffuser and the projection screen.

[0102] When the center of the light spot is not deviated from the central optical axis of the two-dimensional luminance meter and the peak value of the light spot is not deviated from the central optical axis of the two-dimensional luminance meter, the light spot pattern measured by the two-dimensional luminance meter can be referenced. Figure 5 At this time, the center of the light spot measured by the two-dimensional luminance meter is... Figure 4 The mark m in the diagram coincides with the center of the light spot pattern on the diffuser 32. The peak brightness of the light spot on the diffuser 32 is located exactly at mark m, coinciding with the central optical axis of the two-dimensional luminance meter 33. Therefore, a luminance curve can be obtained, and the half-peak and half-width of the luminance of the light spot on the diffuser in the horizontal and vertical directions can be determined based on the luminance curve. Substituting the half-peak and half-width of the luminance of the light spot in the horizontal direction into the formula θ = tan -1In (r / d), r is used to determine the effective field of view in the horizontal direction; similarly, the half-peak and half-width of the brightness of the light spot on the diffuser in the vertical direction are substituted into the formula θ=tan -1 The r in (r / d) allows us to determine the effective field of view in the vertical direction.

[0103] Figure 8 This is the second schematic diagram of the test principle provided in the embodiment of the present invention; Figure 9 The third schematic diagram of the test principle provided in the embodiment of the present invention; Figure 10 The fourth schematic diagram of the test principle provided in the embodiment of the present invention.

[0104] like Figure 8 As shown, when the center of the light spot deviates from the central optical axis of the two-dimensional luminance meter, the tiny light spot projected onto the projection screen 1 is no longer located at the intersection of the central optical axis of the two-dimensional luminance meter 33 and the projection screen, and the center of the light spot measured by the two-dimensional luminance meter 33 deviates from the central optical axis. Figure 4 The mark m is used in the diagram. At this time, the light spot pattern on the diffuser 32 is no longer symmetrical about the mark m. Therefore, in this embodiment of the invention, the position of the center of the light spot needs to be corrected before determining the half-peak and half-width of the brightness of the light spot on the diffuser.

[0105] Specifically, such as Figure 9 As shown, when calibrating the position of the light spot center, the diffuser 32 is first removed from the light-shielding housing 31, and the two-dimensional luminance meter 33 is controlled to directly measure the tiny light spot on the projection screen. Since the two-dimensional luminance meter 33 is set to measure the brightness of different positions on the diffuser 32, the result obtained when directly measuring the tiny light spot is the position Pe(xPe,yPe) where the tiny light spot should be projected on the diffuser 32.

[0106] When the intersection of the central optical axis of the two-dimensional luminance meter 33 and the diffuser 32 is the origin, the position Ps(xPs,yPs) of the tiny light spot on the projection screen 1 can be calculated according to the principle of similar triangles: xPs=xPe×(L+d) / L,yPs=yPe×(L+d) / L。

[0107] like Figure 10 As shown, if the position of the tiny light spot projected on the diffuser 32 is (xm, ym), and the position of the corrected center of the light spot is Pd(x, y), then the position of the center of the light spot can be corrected by x = xm - xPs and y = ym - yPs.

[0108] After correcting the position of the light spot center, the half-peak and half-width of the brightness of the light spot on the diffuser in the horizontal and vertical directions are determined based on the corrected position of the light spot center. Then, the effective field of view in the horizontal and vertical directions is determined based on the half-peak and half-width of the brightness of the light spot on the diffuser in the two directions and the distance between the diffuser and the projection screen.

[0109] It is worth noting that the above calculation process assumes that the diffuser 32 is a transmissive Lambertian diffuser, meaning that the light projected onto the diffuser 32 is completely diffused by the diffuser 32, and the measured brightness of the diffuser 32 does not change with the direction of the incident angle when illuminated by the same illuminance. This simplifies the measurement and calculation process. However, in practice, other transmissive diffusers with diffusion functions can also be used, as long as the correspondence between light intensity and incident angle is considered during the calculation.

[0110] The measurement method provided in this embodiment of the invention uses the half-peak and half-width of the brightness of the light spot on the diffuser in a set direction as the standard for determining the effective field of view in that set direction. Alternatively, the full width at half-peak of the brightness of the light spot on the diffuser in the set direction can also be used to determine the effective field of view; in this case, the effective field of view is the field of view range in both the positive and negative directions of the set direction. When using the same standard to calculate the field of view at different positions on the same projection screen, or to test the field of view at the same position on different projection screens, the properties of the projection screen can be quantitatively described.

[0111] In this embodiment of the invention, the luminous intensity distribution of the tiny light spot B1 incident on the projection screen 1 at different radiation angles can also be accurately calculated based on the measurement data.

[0112] The two-dimensional luminance distribution measured by the two-dimensional luminance meter 33 corresponds to the luminance B at position (X,Y) on the diffuser 32, i.e., the luminance distribution B(X,Y). However, what ultimately needs to be determined is the radiation angular distribution of the intensity of the reflected light from the tiny light spot B1 on the projection screen 1. The spherical coordinates represent the radiation angle from the tiny light spot, and (X,Y) represent the two-dimensional coordinates on the diffuser.

[0113] When the center point of the tiny light spot generated on the projection screen coincides with the origin of the diffuser, the distance from the origin of the diffuser to the point on the diffuser is... therefore:

[0114]

[0115] d represents the distance between the diffuser and the projection screen.

[0116] Another angle in spherical coordinates It can be defined as follows:

[0117]

[0118] If a tiny spot of light on the projection screen illuminates the diffuser, the light travels from the tiny spot towards... The area on the diffuser corresponding to a unit solid angle in the direction is:

[0119]

[0120] Therefore, illuminance, which is the light intensity illuminating each unit area of ​​the diffuser, is:

[0121]

[0122] So, if the gain of this diffuser is Gain(θ,Θ), where Θ is the exit angle to the 2D luminance meter, which is a function of the incident and exit angles to the diffuser, then the luminance measured by the 2D luminance meter is:

[0123]

[0124] If a Lambertian diffuser is used, then Gain is no longer a function, but a constant, resulting in:

[0125]

[0126] Therefore, we can conclude that:

[0127]

[0128] Based on the above function, when the brightness B(X,Y) at a set position on the diffuser is measured, the luminous intensity of the tiny light spot projected onto the projection screen at the corresponding radiation angle can be determined. This allows us to determine the intensity distribution of the luminescence of the tiny light spot at different radiation angles.

[0129] Figure 11 This is a schematic diagram of the Fresnel structure provided in an embodiment of the present invention.

[0130] like Figure 11 As shown, a Fresnel structure layer is typically provided in the projection screen, which includes multiple Fresnel structures F arranged according to a set rule. Depending on the application and manufacturing process, each Fresnel structure F can form a concentric circle structure that expands radially; or, each Fresnel structure F can be a linear structure that extends along the horizontal direction of the projection screen and is arranged perpendicular to the horizontal direction, which is not limited here.

[0131] The Fresnel structure F includes an inclined reflective surface, the tilt angle of which is set according to the incident angle of the projected light, used to reflect the light emitted from the projection device towards the viewer. The reflection angle of the Fresnel structure determines the direction or range from which the projected image can be viewed.

[0132] This invention allows for the evaluation of the reflection direction of light by a Fresnel structure based on measurement results. Specifically, the luminous intensity distribution of a tiny light spot at different radiation angles can be determined according to the aforementioned functional relationship. This allows for the determination of the radiation angle corresponding to the peak luminous intensity. This radiation angle is the angle at which light is reflected by the reflective surface of the Fresnel structure after incident on it. Therefore, based on this radiation angle, it can be determined whether the current Fresnel structure design meets the requirements, and the tilt angle of the reflective surface of the Fresnel structure can be adjusted accordingly.

[0133] The measurement method provided in this embodiment of the invention relies on a specially designed test box, which can be placed at any position on the projection screen where the measurement is required.

[0134] Figure 12 The fifth schematic diagram of the test principle provided in the embodiment of the present invention.

[0135] like Figure 12 As shown, the test box 3 can be mounted on a bracket. In this embodiment of the invention, the bracket includes a first track 41 and a second track 42. The first track 41 is fixed to the top of the projection screen 1, one end of the second track 42 is slidably connected to the first track 41, and the test box 3 is slidably connected to the second track 42. The direction of the first track 41 can be horizontal, and the direction of the second track 42 can be vertical. Therefore, the test box 3 can slide vertically along the second track 42, while the second track 42 can slide horizontally along the first track 41. Thus, by sliding the test box 3 and the second track 42, the test box 3 can be moved to any set position on the projection screen.

[0136] Figure 13 This is a schematic diagram of the test location provided in an embodiment of the present invention.

[0137] In some embodiments, such as Figure 13 As shown, the projection screen can be divided into three equal parts along both the horizontal and vertical directions, forming nine regions. The center positions S1 to S9 of these nine regions can serve as multiple preset positions on the projection screen to be measured. By measuring the field of view angles at these nine positions, the field of view at different positions on the projection screen can be evaluated. When measuring the field of view angle at any position, the test box 3 can be moved to the corresponding position, and then light can be projected onto the corresponding position on the projection screen, following the procedure described above.

[0138] Of course, the embodiments of the present invention are only for illustrative purposes. In actual implementation, the test box can be moved to any position that needs to be measured other than S1 to S9 mentioned above. According to the above measurement method, information such as the field of view at that position and the distribution of luminous intensity at different radiation angles can be obtained.

[0139] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0140] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for measuring the field of view of a projection screen, characterized in that, include: Place the test box at the designated position on the projection screen; The test box includes a light-shielding shell, at least a portion of the side of the light-shielding shell having a gap with the projection screen, a diffuser being disposed in the light-shielding shell, and a two-dimensional luminance meter being installed at the end of the light-shielding shell away from the projection screen; The control projection device emits test light through the gap between the test box and the projection screen, forming tiny light spots on the projection screen; The two-dimensional luminance meter is controlled to measure the luminance distribution of the light spot generated by the tiny light spot projected onto the diffuser sheet; The field of view of the projection screen at the set position is determined based on the measured brightness distribution.

2. The measurement method as described in claim 1, characterized in that, The size of the tiny light spot satisfies the following relationship: a <d×tan(10°); Where a represents the size of the tiny light spot, and d represents the distance between the diffuser and the projection screen.

3. The measurement method as described in claim 2, characterized in that, The diffuser sheet is arranged parallel to the projection screen, and the distance between the diffuser sheet and the projection screen satisfies the following relationship: Where d represents the distance between the diffuser and the projection screen, θ' represents the effective field of view of the tiny light spot in the set direction, and b represents the size of the diffuser in the set direction; the effective field of view is the field of view corresponding to the half-peak and half-width of the brightness of the light spot generated on the diffuser in the set direction.

4. The measurement method as described in claim 1, characterized in that, The distance between the two-dimensional luminance meter and the diffuser is 100mm to 200mm.

5. The measurement method according to any one of claims 1 to 4, characterized in that, Determining the field of view of the projection screen at the set position based on the measured brightness distribution includes: The half-peak and half-width of the light spot on the diffuser in the horizontal and vertical directions are determined based on the measured brightness distribution. The effective field of view of the projection screen at the set position is determined based on the half-peak and half-width of the brightness of the light spot on the diffuser in the horizontal and vertical directions, and the distance between the diffuser and the projection screen.

6. The measurement method as described in claim 5, characterized in that, Before determining the half-peak and half-width of the brightness of the light spot on the diffuser in the horizontal and vertical directions based on the measured brightness distribution, the method further includes: Remove the diffuser from the test box and control the two-dimensional luminance meter to directly measure the position of the tiny light spot on the projection screen; The position of the center of the light spot on the diffuser is corrected according to the position of the tiny light spot; The step of determining the half-peak and half-width of the brightness of the light spot on the diffuser in the horizontal and vertical directions based on the measured brightness distribution includes: Based on the corrected center position of the light spot and the measured brightness distribution, the half-peak and half-width of the brightness of the light spot on the diffuser in the horizontal and vertical directions are determined respectively.

7. The measurement method as described in claim 6, characterized in that, The diffuser is a permeable Lambertian diffuser; the measurement method further includes: The luminous intensity distribution of the tiny light spot on the projection screen at different radiation angles is determined based on the measured brightness distribution; The radiation angle and luminous intensity from the tiny light spot satisfy the following relationship: in, This indicates that the tiny light spot is in spherical coordinates. The luminous intensity in the direction, B(X,Y) represents the brightness at position (X,Y) on the diffuser, d represents the distance between the diffuser and the projection screen, and Gain represents the gain of the diffuser.

8. The measurement method as described in claim 7, characterized in that, The projection screen includes a Fresnel structure, which is used to receive the projection light emitted from the projection device and reflect it in a predetermined direction; the measurement method further includes: The radiation angle corresponding to the peak luminous intensity is determined based on the luminous intensity distribution of the tiny light spot at different radiation angles; The Fresnel structure of the projection screen is evaluated based on the determined radiation angle.

9. The measurement method according to any one of claims 1 to 4, characterized in that, The test box is mounted on a bracket, which includes a first track and a second track; the first track is fixed to the top of the projection screen, one end of the second track is slidably connected to the first track, and the test box is slidably connected to the second track; Placing the test box at a predetermined position on the projection screen includes: Slide the test box and the second track to move the test box to the set position on the projection screen.

10. The measurement method as described in claim 9, characterized in that, The projection screen has multiple designated positions. The projection screen is divided into three equal parts along the horizontal and vertical directions, forming nine regions. The designated positions are the center positions of the nine regions.

Images