projector

Abstract

The present invention realizes a projector that can prevent the degradation of optical performance caused by changes in the shape of the reflective surface due to localized high temperatures of the projector's reflector. It includes an image display unit and an imaging optical system that magnifies and projects the image displayed by the image forming section of the image display unit onto a projection surface. The imaging optical system includes: a lens system (LS) to which image light from the image forming section is incident; a synthetic resin reflector (M) disposed on the magnifying side of its aperture stop (S) and having refractive power; and an image correction control unit (4) that corrects for degradation of the magnified image caused by uneven temperature rise of the reflector (M) due to the intensity distribution of the imaging beam.

Description

Technical Field

[0001] This invention relates to projectors. Background Technology

[0002] In the past, there have been various methods of projectors that display the image formed by the image forming unit of the image display unit as a magnified image on the projection surface.

[0003] As image display units, there are various known units such as LED arrays that arrange tiny light-emitting elements in one-dimensional or two-dimensional arrays and represent two-dimensional images through the "distribution of light-emitting elements", units that modulate the intensity of illumination light from a light source to form images using so-called "light valves" such as DMD (digital mirror device) and liquid crystal panels.

[0004] The "image forming section" is the part of the LED array and light valve that "displays the image to be magnified and projected". Hereinafter, the magnified image projected onto the projection surface (generally the "screen surface") will also be referred to as the "projected image".

[0005] As an optical structure for a projector, it is known that a structure can be achieved by combining a lens system and a "reflector with refractive power" as optical elements to achieve a short projection distance.

[0006] In this optical structure, the image beam from the image forming unit is incident on the lens system, and a mirror is used to reflect the beam through the lens system toward the projection surface. Hereinafter, the image beam that participates in the imaging of the projected image will also be referred to as the "imaging beam".

[0007] In projectors, there is a problem of heat generation in the light source used to generate the imaging beam (such as a self-generating light source like the LED array mentioned above, or an illumination source that illuminates the light valve).

[0008] That is, the magnified image projected onto the projection surface requires "brightness". However, if the amount of light emitted by the light source is increased in order to make the magnified image brighter, there will be a problem that the heat generated by the light source will increase, and the optical components such as lenses and mirrors will be thermally deformed, leading to the deterioration of optical performance.

[0009] Such problems are known in the past. Patent document 1 discloses the following technology: In an imaging optical system having a lens system and an aspherical mirror, in order to cope with the deterioration of optical performance caused by the thermal deformation of the aspherical mirror, the temperature of the aspherical mirror or its vicinity is adjusted by cooling or the like.

[0010] In addition, Patent Document 2 discloses the following technology: In an imaging optical system composed of a lens system, a correction lens disposed in the lens system is shifted in the direction of the optical axis according to the temperature change to correct the astigmatism and other degradation of the projected image caused by the temperature change in the lens barrel of the holding lens system.

[0011] The mirrors used in projectors have refractive power, so most of them are "concave or convex curved surfaces" and are aspherical. From the point of view of ease of forming the surface shape and low cost, they are mostly formed from synthetic resin.

[0012] If the brightness of the magnified image is increased, the light intensity within the cross section orthogonal to the direction of travel of the imaging beam also increases. This light intensity is non-uniform across this cross section, and even on the reflecting surface of the mirror, the light intensity is non-uniform. The non-uniform light intensity distribution on the reflecting surface of the mirror varies depending on the structure of the lens system and the positional relationship between the image forming unit and the lens system. Furthermore, although it also varies depending on the displayed image, the effect of the change in the light intensity distribution of the imaging beam caused by the change in the displayed image is generally small, and the light intensity distribution caused by the structure of the lens system and the positional relationship between the image forming unit and the lens system remains relatively stable.

[0013] In the portion of the imaging beam incident on the reflecting surface of the mirror, where the light intensity is high, a localized high-temperature region is formed on the reflecting surface.

[0014] In a synthetic resin mirror, the low thermal conductivity of the resin itself makes it difficult for heat to dissipate from the areas where the imaging beam has high intensity, causing the temperature to rise easily. Furthermore, the high thermal expansion coefficient of synthetic resin makes it prone to large deformations due to thermal expansion in the areas where the temperature rises.

[0015] Therefore, the temperature rise of the reflector occurs locally (point-like), and the resulting local deformation of the reflector surface causes the focal position of the light reaching the periphery of the projected surface (screen surface) to change, thus degrading the resolution of the periphery of the projected image.

[0016] Since the aforementioned deformation of the synthetic resin mirror is "localized," in methods such as Patent Document 1 that "adjust the temperature of the mirror or its vicinity by cooling or the like," the low thermal conductivity of the synthetic resin makes it difficult to quickly address the issue as it takes time to achieve overall temperature uniformity of the mirror.

[0017] The imaging optical system of Patent Document 2 consists of a lens system and does not include a synthetic resin mirror, so there is no problem of local deformation of the synthetic resin mirror. Summary of the Invention

[0018] The problem that the invention aims to solve

[0019] The objective of this invention is to realize a projector capable of effectively correcting the degradation of the optical performance of the aforementioned imaging optical system, which is caused by localized overheating due to uneven intensity of the imaging beam from the synthetic resin mirror, resulting in deformation of the reflective surface shape.

[0020] Methods for solving problems

[0021] The projector of the present invention projects an image displayed by an image forming unit of an image display unit onto a projection surface as a magnified image. The projector includes: an image display unit; an imaging optical system that projects an image beam from the image display unit onto the projection surface as an imaging beam; and an image correction control unit that corrects the magnified image on the projection surface. The imaging optical system includes: a lens system into which the image beam from the image forming unit is incident and has a zoom function; and a synthetic resin reflector disposed on the magnification side of the aperture stop of the lens system, reflecting the imaging beam and having refractive power. The image correction control unit is a unit that corrects the degradation of the magnified image caused by uneven temperature rise due to the intensity distribution of the imaging beam on the reflector reflecting the imaging beam. It includes: a parameter temperature detection unit that detects the temperature of multiple locations on the back side of the reflector and obtains a parameter temperature from the detected multiple temperatures; and a control unit that controls the zoom function based on the parameter temperature obtained by the parameter temperature detection unit to correct the degradation of the magnified image.

[0022] Invention Effects

[0023] According to the present invention, a projector is made that can effectively correct the deterioration of optical performance caused by localized high temperatures on the reflective surface of a synthetic resin mirror with refractive power. Attached Figure Description

[0024] Figure 1 This is a conceptual diagram of the imaging optical system of a projector.

[0025] Figure 2 This is a diagram illustrating the temperature distribution on the back of the mirror based on the intensity distribution of the imaging beam.

[0026] Figure 3 This is a diagram illustrating the determination of the temperature parameter of a reflector in one embodiment.

[0027] Figure 4 This is a diagram illustrating the control unit for deterioration correction of a magnified image in one embodiment.

[0028] Figure 5This is a diagram illustrating the control of image degradation correction in one embodiment. Detailed Implementation

[0029] Figure 1 This is a conceptual diagram of the imaging optical system of a projector.

[0030] The imaging optical system has a lens system LS and a reflector M made of synthetic resin.

[0031] In the figure, reference numeral O indicates the "image display surface on which the image display section is formed" of the image display unit. Additionally, reference numeral CMX indicates the color synthesis unit, and reference numeral AX indicates the optical axis of the lens system of the imaging optical system.

[0032] The image display unit is the "upper half of the image" of the image display surface O, and is positioned upwards relative to the optical axis AX. The image beam from the image display unit is incident on the lens system LS via the color synthesis unit CMX, and when it exits from the lens system LS, it is incident on the reflector M. When reflected, it becomes the projection beam FLX, which is then projected as a magnified image onto a screen (not shown) located on the left side of the image.

[0033] That is, the image beam incident on the lens system LS is used as the imaging beam and passes through the lens system LS and the reflecting mirror M, and is emitted as the projection beam FLX.

[0034] The image display unit consists of three DMDs (Digital Display Devices) that display images of the three primary colors: R (red), G (green), and B (blue). Figure 1 The image depicts one of these components, where light from LED light sources of corresponding colors is reflected as image light of each color, incident on the color synthesis unit CMX to be synthesized into a colored image beam, and then incident on the lens system LS.

[0035] The lens system LS has an aperture stop S, and a reflecting mirror M is positioned on the magnifying side of the aperture stop S. In this example, the reflecting mirror M, made of synthetic resin, is a concave mirror with "positive refractive power".

[0036] The lens system LS has a "variable focal length function". Figure 1 The reference FL in the attached diagram is a floating mechanism used to perform the zoom function. The focal length changes by moving the movable lens of the floating mechanism in the direction of the optical axis AX through a cam mechanism (not shown).

[0037] In the projector of the present invention, as described above, there is an image correction control unit that corrects the degradation of the magnified image caused by the uneven temperature rise of the reflector due to the intensity distribution of the imaging beam.

[0038] The above corrections are made as follows.

[0039] That is, the temperature of multiple locations on the back side of the reflector M is detected, and parameter temperatures are obtained based on the detected temperatures. Then, the zoom function is controlled based on the obtained parameter temperatures to correct the degradation of the magnified image.

[0040] Therefore, the projector includes a parameter temperature detection unit and an image correction control unit.

[0041] "Parameter temperature" is temperature information used for image correction control. It is calculated by detecting the temperature of multiple parts on the back side of the mirror M and determining the parameter temperature based on the detected temperatures.

[0042] For example, if the temperature detection points are set to n points (n≥2), and the detection temperatures obtained at each point are set to T1, T2, ..., Tn, then the parameter temperature: TP is determined by using these detection temperatures: T1, T2, ..., Tn.

[0043] For example, the arithmetic mean of the detected temperatures T1~Tn: (ΣTi) / n (i=1~n) can be used as the parameter temperature, or the weighted average of each detected temperature assigned a weight m1~mn: Σmi Ti / Σmi (i = 1~n) is used as the parameter temperature. Of course, the parameter temperature is not limited to the arithmetic mean or weighted average of the detected temperatures.

[0044] The determined parameter temperature, TP, is associated with the degradation of the projected image. On a synthetic resin mirror M, if an uneven temperature distribution is generated due to the inhomogeneity of the imaging beam intensity distribution, the parameter temperature, TP, will change accordingly.

[0045] When an uneven temperature distribution is generated in the reflector M, the focal length of the imaging optical system, mainly the distance of the focal point of the light reaching the periphery of the projected surface (screen surface), changes accordingly.

[0046] The change in focal length (denoted as "Y") and the change in parameter temperature TP have a certain correspondence depending on the imaging optical system and the image display unit, and this correspondence can be determined in advance through experiments.

[0047] That is, the relationship between the changing parameters of temperature (TP) and the changes in focal length (Y) caused by changes in focal position (F), i.e.,

[0048] Y = F(TP)

[0049] This can be determined through experiments.

[0050] This change in focal length, Y, can be corrected by adjusting the focal length of the lens system in the imaging optics.

[0051] That is, the focal length change, Y, can be eliminated by the movement of the movable lens of the floating mechanism FL, Z. The relationship between the focal length change, Y, and the movement of the movable lens of the floating mechanism FL, Z, is G, i.e.

[0052] Z = G(Y)

[0053] It can also be determined through experiments.

[0054] Based on this relationship: Z = G(Y), the lens movement amount: Z can be associated with the action amount: D(Z) of the lens moving mechanism used to realize the movement amount: G. As the lens moving mechanism, a cam mechanism from a typical zoom mechanism can be used, in which case the action amount: D(Z) is the "rotation amount of the driving cam" in the cam mechanism.

[0055] Thus, if the parameter temperature: TP is determined, the amount of movement of the movable lens of the floating mechanism FL, which is used to correct the "change in the distance of the focal position of the light reaching the periphery of the projected surface" generated when the parameter temperature: TP is generated, is determined. Therefore, by displacing the movable lens with the amount of action of the lens moving mechanism: D(Z) according to the parameter temperature: TP, the degradation of the projected image, mainly in the periphery, can be effectively corrected.

[0056] Figure 4 The diagram shown is an explanatory diagram of the structure of the image correction control unit.

[0057] The image correction control unit has a temperature detection unit 3, a control calculation unit 4, and an adjustment mechanism 5.

[0058] The control and processing unit 4 is composed of a microcomputer and controls the temperature detection unit 3.

[0059] The temperature detection unit 3 has multiple temperature detectors, such as thermistors. These detectors are controlled by the control and processing unit 4 to detect the temperature of the reflector M at multiple locations on the back side of the synthetic resin reflector M.

[0060] The temperature detected by multiple thermistors is input into the control calculation unit 4, and the parameter temperature: TP is determined by the parameter temperature determination unit 41.

[0061] The correction amount determination unit 42 determines the amount of motion of the lens moving mechanism (the aforementioned amount of motion: D(Z)) based on the parameter temperature: TP, and outputs the determined amount of motion to the adjustment mechanism 5. The adjustment mechanism 5 performs correction by moving the movable lens according to the input amount of motion.

[0062] That is, the temperature detection unit 3 and the parameter temperature determination unit 41 are "parameter temperature detection units", and the correction amount determination unit 42 and the adjustment mechanism 5 are "control units".

[0063] This control process continues while the projector is powered on. For example, the temperature of the reflector M is detected, i.e., the sampling of the detection values ​​of multiple thermistors is performed at predetermined time intervals, such as every 30 seconds or every minute, and the determination of the action quantity D(Z) is also based on these time intervals.

[0064] The process of determining the action quantity D(Z) based on the parameter temperature TP can be carried out as follows: Based on the parameter temperature TP, perform calculations successively based on the above relationships Y=F(TP) and Z=G(Y) determined in advance through experiments, and determine the action quantity D(Z) based on the Z obtained from the calculation results.

[0065] The parameter temperature: TP and the action quantity: D (Z) (hereinafter referred to as "D") are determined in advance through experiments. Therefore, instead of the above successive calculations, the relationship between the parameter temperature: TP and the action quantity: D can be stored as an expression or table in the correction quantity determination unit 42. The action quantity: D corresponding to the determined parameter temperature: TP is determined by calculating the expression or referring to the table.

[0066] The following describes one implementation method.

[0067] Trial production of such Figure 1 The imaging optical system shown.

[0068] The reflector M is made by molding a 5mm thick acrylic synthetic resin into a concave shape, and then depositing an aluminum reflective film on the concave surface.

[0069] Figure 2 M represents the prototype reflector.

[0070] LEDs of R, G, and B colors were used as the light source. The resulting image beam, corresponding to the white image, was reflected by the DMD. The temperature distribution of the reflector M was measured from the back side after one hour of continuous operation at a light source wattage of 300W. The results are as follows: Figure 2 That would be the outcome.

[0071] Mirror M is a concave mirror. Figure 2 Viewed from the back side, the concave mirror has a three-dimensional shape that is "facing..." Figure 2 The attached diagram shows a shape that bulges outwards from the front.

[0072] The temperature distribution shows a maximum temperature of 31.138°C in the regions indicated by reference numerals A1 and A2. In the region indicated by reference numeral A3, the temperature continuously changes from 29.227°C to 27.316°C as one moves away from regions A1 and A2. In region A4, which is further outward, the temperature continuously decreases from 27.316°C towards the outermost edge (the outer periphery of mirror M) at 22.539°C. Furthermore, the temperature variations within the temperature distribution are smooth.

[0073] In addition, the reflector M is designed to have a room temperature of 22 degrees Celsius.

[0074] The reflector M is made of synthetic resin and is 5 mm thick. Considering the low thermal conductivity of synthetic resin, the surface temperature of reflector M is... Figure 2 The temperature on the front is more than 10 degrees higher than that on the back.

[0075] In regions A1 and A2, which are approximately 10 degrees higher than the designed temperature of 22 degrees, the surface of mirror M undergoes uneven thermal expansion, which weakens the positive refractive power, resulting in image plane curvature, chromatic aberration, and resolution degradation.

[0076] As described above Figure 4 The degradation of the projected image was corrected as described.

[0077] The following is an example of a correction.

[0078] Figure 3 Three thermistors S1, S2, and S3 are placed in contact with the back of the reflector M to serve as a parameter temperature detection unit. Figure 4 (Temperature detection unit). The positions of these thermistors S1, S2, and S3 are as follows. Thermistor S1 is the "position on the back side of the reflector" at the intersection of the optical axis AX of the lens system LS and the reflecting surface of the reflector M.

[0079] Thermistor S2 is located at Figure 2 The high-temperature region A1 is shown, and the thermistor S3 is also located in the high-temperature region A2.

[0080] Image correction control unit uses Figure 4 The unit shown in Figure 4.

[0081] That is, the thermistors S1, S2, and S3 are controlled by the control and arithmetic unit 4, which is configured as a microcomputer.

[0082] The following refers to the action flow. Figure 5 Please provide an explanation.

[0083] exist Figure 5In this diagram, (S1) to (S14) represent the step numbers of the control process. Additionally, "Y" indicates yes, and "N" indicates no.

[0084] The control process begins when the projector is powered on (S1).

[0085] The parameters for the number of temperature measurements (i) and the number of correction actions (j) are both 1 (S2). Thermistors S1, S2, and S3 are in working state. The sampling time is set to 1 minute. The detected temperatures of thermistor S1 (T1), thermistor S2 (T2), and thermistor S3 (T3) are taken into the control operation unit 4 (S3).

[0086] Next, the parameter temperature TP (S4) is determined based on the detected temperatures: T1, T2, T3.

[0087] In this example, the parameter temperature TP is calculated based on the temperatures T1 to T3 detected by thermistors S1 to S3, using the formula: TP = (T2 + T3) / 2 - T1 (Formula 1). This formula is determined in advance through experiments and stored in the storage unit of the control calculation unit 4. When the temperatures T1 to T3 are sampled, the calculation unit performs the calculation according to Formula 1.

[0088] As mentioned above, T2 and T3 are the temperatures of the "high-temperature regions A1 and A2" on the back of the reflector. Therefore, temperatures T2 and T3 are higher than temperature T1. According to the above formula, the parameter temperature TP is a "positive value".

[0089] The determined parameter temperature: TP is used as the parameter temperature: TPi identified by the number of temperature measurements: i, and compared with the threshold: TS (S5). The threshold: TS, as "the temperature representing the state of the reflector M that needs to be corrected and controlled", is determined in advance through experiments and stored in the storage section of the control operation unit 4.

[0090] When TPi≤TS, "there is no need to move the lens of the lens system," so the number parameter i is increased to "i+1" (S6), and the thermistor is sampled again. The sampling period is 1 minute, starting 1 minute after the last sampling.

[0091] Repeat steps (S3~S6~S3) until the parameter temperature TP becomes above the threshold TS. When the parameter temperature TP becomes above the threshold TS, use the parameter temperature TPi that has become above the threshold to calculate the motor's rotation angle θ. At this point, correct the number of actions parameter j to 1.

[0092] The motor's rotation angle: θ is the aforementioned action amount: D, which is achieved through the cam mechanism to activate the floating mechanism FL ( Figure 1The rotation angle of the motor moves the lens of the rotating lens.

[0093] As mentioned above, the relationship between the motion quantity: D and the parameter temperature: TP was determined experimentally and can be stored as a table or as a formula. However, in this example, the rotation angle: θ is calculated using a formula with the parameter temperature: TPi, determined as described above, as the variable:

[0094] θ = a(TPi) 2 +b(TPi)+c(Expression 2)

[0095] To perform calculations.

[0096] In formula 2, [a, b, c] are constants determined in advance through experiments. Formula 2 is stored in the storage section of the control calculation unit 4. The calculation unit first determines the parameter temperature "TPi". The calculation is performed according to the above formula 2. The calculated rotation angle: θ becomes the rotation angle: θj identified by the correction action number parameter: j (S7).

[0097] Rotation angle: θj is compared with θj-1 (S8), and the motor action (S9) or motor reverse action (S10) is performed according to its magnitude.

[0098] When the correction action number parameter j is 1, θj-1 is θ0, but θ0 corresponds to the reference position in the rotation of the cam. When the correction action number parameter j is 2 or more, θj-1 is the rotation angle in the previous correction action.

[0099] When j≥2, if the rotation angle θj is larger than the previous rotation angle θj-1, the movement of the moving lens of the floating mechanism FL needs to be increased compared to the previous movement. Therefore, in this case, the motor is moved in the "positive direction" to increase the movement of the moving lens (S9).

[0100] The movement is performed in a loop between steps S11 and S9 until the lens of the rotating lens is in the correct position. When the lens is in the correct position, the motor is stopped (S13).

[0101] Conversely, when j≥2, if the rotation angle θj is less than the previous rotation angle θj-1, the movement of the operating lens of the floating mechanism FL needs to be reduced compared to the previous movement. Therefore, in this case, the motor reverses its action and the operating lens moves in the opposite direction (S10).

[0102] The movement is performed in a loop between steps S10 and S12 until the lens of the rotating lens is in the correct position. When the lens is in the correct position, the motor is stopped (S13).

[0103] The control of steps S9 to S13 is controlled by the control unit of the control calculation unit 4.

[0104] When the motor stops in step S13, the control unit 4 corrects the action count parameter: j is increased to j+1, and returns to step S3 to perform a new sampling of the reflector temperature. The above process is repeated.

[0105] In addition, the amount of rotation of the motor action and reverse action in steps S9 to S12 can be "detected and controlled by a potentiometer", or a stepper motor can be used as the motor for control.

[0106] The preferred embodiments of the invention have been described above, but the invention is not limited to the specific embodiments described above. As long as there are no special limitations in the above description, various modifications and alterations can be made within the scope of the spirit of the invention as described in the scope of the patent claim.

[0107] As described above, the "non-uniform light intensity distribution" on the reflecting surface of the mirror varies depending on the structure of the lens system and the positional relationship between the image forming unit and the lens system; therefore, the temperature distribution of the mirror also varies accordingly. Temperature detection by multiple thermistors allows for the selection of appropriate locations based on the temperature distribution of the mirror.

[0108] In the embodiments described above, the positions of thermistors S2 and S3 among the three thermistors are selected as follows: Figure 2 The local high-temperature regions A1 and A2 are shown.

[0109] The pattern of temperature distribution generated by the imaging beam on the mirror M varies depending on the "light intensity distribution of the imaging beam on the mirror". However, the positional relationship between the image display unit, the lens system, and the mirror is uniquely determined by the design. Therefore, it is possible to optimize the number and arrangement of thermistors based on the temperature distribution pattern determined in this way.

[0110] Furthermore, since the reflector is located on the magnification side of the aperture stop of the lens system, it can also be the optical element closest to the magnification side of the imaging optical system as described above. However, it is also possible to further configure one or more lenses constituting the lens system on the magnification side of the reflector.

[0111] Furthermore, in the above embodiment, a mirror with a concave reflective surface is shown, but depending on the imaging optical system, it may also be a mirror with a convex reflective surface.

[0112] The effects described in the embodiments of the present invention are merely examples of preferred effects produced by the invention, and the effects of the invention are not limited to the effects described in the embodiments.

[0113] Explanation of reference numerals in the attached figures

[0114] The surface in the O image display unit where the image display section is formed;

[0115] LS lens system;

[0116] M-mirror;

[0117] S1, S2, and S3 thermistors;

[0118] FL floating mechanism.

[0119] Existing technical documents

[0120] Patent documents

[0121] Patent Document 1: Japanese Patent Application Publication No. 2008-145623;

[0122] Patent Document 2: Japanese Patent No. 7027736.

Claims

1. A projector that projects an image displayed by an image forming unit of an image display unit as a magnified image onto a projection surface, characterized in that, The projector includes: an image display unit; an imaging optical system that projects an image beam from the image display unit onto the projection surface as an imaging beam; and an image correction control unit that corrects the magnified image on the projection surface. The imaging optical system includes: a lens system into which an image beam from the image forming unit is incident, and has a zoom function; and a synthetic resin mirror disposed on the magnification side of the aperture stop of the lens system, reflecting the imaging beam and having refractive power. The image correction control unit is a unit that corrects the degradation of the magnified image caused by the uneven temperature rise caused by the intensity distribution of the imaging beam on the mirror reflecting the imaging beam. It includes: a parameter temperature detection unit that detects the temperature of multiple parts on the back side of the mirror and obtains a parameter temperature from the detected multiple temperatures. And a control unit that controls the zoom function based on the parameter temperature obtained by the parameter temperature detection unit to correct the degradation of the magnified image.

2. The projector according to claim 1, characterized in that, The parameter temperature is obtained based on the temperature detected by a plurality of thermistors configured to contact the back of the mirror.

3. The projector according to claim 2, characterized in that, The number of thermistors is 3.

4. The projector according to any one of claims 1 to 3, characterized in that, The zoom function includes a floating mechanism that shifts the movable lens in the lens system.

Images