JP2005351959A - Image projecting apparatus and focusing method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the accuracy of data which is stored in a storage part (EEPREM) and which is referred to in automatically focusing. <P>SOLUTION: The apparatus is provided with a range finding part 4 for measuring a projection distance Dp, a PROM in an AF control part 6 for pre-storing data showing the corresponding relation between the focal position of an automatic focusing lens 3Ab and the projection distance Dp, and a calibration switch 7A. The focal position at the start of calibration is detected by a CPU in the AF control part 6, and the detected focal position is compared with the focal position obtained by referring the latest projection distance to the data in the PROM. Further, the offset quantity is calculated based on the deviation between two focal positions, and the data in the PROM is shifted as much as the offset quantity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image projection apparatus that enlarges image light that is light-modulated in a projection optical unit by a projection lens and projects the image light onto an external projection surface (for example, a screen surface), and a focus adjustment method thereof.

Many projection-type image display devices such as projectors (hereinafter referred to as image projection devices) have an autofocus (AF) mechanism that automatically corrects the out-of-focus blur of an image projected on a screen.
As a mechanism for AF, in general, a focus lens in the projection optical unit, an AF drive unit (AF motor unit) that moves the focus lens in the direction of the projection optical axis in the projection optical unit, and an AF drive unit are optimally controlled. And an AF control unit for moving the focus lens to a proper position.

In such an image projection apparatus, when the light from the light source is focused on the screen by the light modulation unit, for example, RGB liquid crystal panel, the relative position between the projection lens in the projection optical unit and the screen is determined. It is necessary to measure accurately, and a so-called distance measuring unit is provided as a configuration for that purpose.
As a typical distance measuring unit, light from a built-in infrared LED is applied to a screen, reflected light (reflected light) is received by a position detection sensor such as a PSD (position sensitive detector), and the photoelectric conversion is performed after the photoelectric conversion. Some output electrical signals.

The electric signal output from the PSD is sent to the AF control unit, where focus calculation based on the so-called triangulation method is executed, and the optimum focus lens position is calculated.
At this time, the AF control unit detects the light receiving position by obtaining the peak position of the light intensity distribution of the light receiving pattern from the PSD electrical signal, and calculates the distance to the screen depending on how much the light receiving position deviates from the reference position. Get the underlying data. The projection distance to the screen is determined from the data using a triangulation method, and the optimum focus lens position is calculated using the projection distance.
The AF control unit controls the AF driving unit so that the obtained focus lens position is obtained. This control is often performed by actually projecting an image at the time of initial setting of the projector, and it can be visually confirmed that the focus lens has moved and the image is in focus. This completes a series of AF operations.

  Although the basic AF operation is performed as described above, in practice, even if image projection is performed at the focus lens position calculated by the AF control unit, the focus may not be achieved on the screen. One of the causes is that the distance between the optical axes (baseline length) varies between the infrared LED and PSD that make up the distance measuring unit, the mechanical variation in the lens position of the projection lens and autofocus lens, and the individual differences in lens characteristics. There is.

More specifically, since the projection optical lens unit of the projection optical unit mounted on the projector is an assembly of a large number of, for example, a dozen or so lenses, the dimensional errors of the various lenses themselves and the various lens There may be deviations from design values due to assembly errors. There are also individual differences in the optical characteristics of the lens.
When there is such an error factor, the actual projection optical unit has a characteristic deviated from the ideal curve of the AF characteristic curve indicating the relationship between the projection distance and the focus lens position.

  In order to correct such an error factor, it is known that the AF control unit corrects the calculated focus lens position based on data stored in advance in a built-in EEPROM or the like, and appropriately corrects it. (For example, refer to Patent Document 1).

According to the description in Patent Document 1, adjustment data for correcting errors generated due to variations in distance measurement data and mechanical variations in lens position when the distance measurement data is converted into lens position data, during production, It is stored in this EEPROM.
Japanese Patent Laid-Open No. 08-234079 (refer to page 4, left line, first to fourth lines)

In the manufacture of projectors, parts such as optical lens units are delivered, and those whose characteristics pass the parts standard are used for assembly. At that time, data indicating the relationship between the projection distance and the focus lens position (or the amount of focus movement from the reference position) based on the ideal characteristics (ideal curve) of the optical lens unit for which the component standards are defined is stored in the EPPROM. Write in advance.
However, a slight deviation between each optical lens unit and the ideal curve due to individual differences among the individual optical lens units is not reflected in the data in the EEPROM.

  Further, the data stored in the EEPROM is data reflecting the mechanical variation of the optical lens unit according to the description in Patent Document 1. Therefore, since the distance (flange back) from the projection optical unit to the light modulation element is reflected in the data as a fixed value used when measuring the characteristics of the optical lens unit, variations in flange back are reflected in the data. Not.

  The variation in flange back generally depends on the projection lens performance, the dimensional accuracy of the 4P prism that synthesizes the RGB modulated light, the thickness accuracy of the polarizing plate disposed on the output side of the RGB light modulation means, and the like. . Therefore, as described in Japanese Patent Application Laid-Open No. H10-228707, autofocus with high accuracy cannot be achieved simply by reflecting the mechanical variation of the optical lens unit in the correction data in the EEPROM.

  For the above two reasons, the conventional image projection apparatus has a problem that the focus accuracy of the projected image at the time of autofocus is poor.

  The problem to be solved by the present invention is to provide an image projection apparatus that improves the accuracy of data in a storage unit (EERPEM) that is referred to during autofocus, and as a result, improves the focus accuracy, and a focus adjustment method thereof. It is.

  An image projection apparatus according to the present invention includes a projection optical unit including a projection lens and an autofocus lens, and expands the image light modulated in the projection optical unit by a projection lens and projects the image light onto an external projection surface. A distance measuring unit that measures a projection distance from the projection lens to the projection surface, and a correspondence relationship between a focus position that is a position in an optical axis direction in a projection optical unit of the autofocus lens and the projection distance. A storage unit that preliminarily stores data to indicate, a calibration start instruction unit, the focus position when the calibration start is instructed, and the detected focus position before the calibration start. The latest projection distance measured by the distance measuring unit is compared with the focus position obtained by referring to the data in the storage unit. Calculating an offset amount from the shift amount of two focus positions, it has a calibration execution means for shifting the data of the offset amount only in the storage unit.

  The image projection apparatus of the present invention is preferably an autofocus control that obtains a focus position by referring to the data in the storage unit for the projection distance measured by the distance measuring unit and controls the autofocus lens to the obtained focus position. The calibration start instruction means is operated when the image is projected at the focus position controlled by the autofocus control means and the projection surface is out of focus. Means.

According to the image projection apparatus configured as described above, when a calibration start instruction is issued, the calibration execution unit performs calibration for correcting the data in the storage unit indicating the correspondence between the focus position and the projection distance. Execute.
More specifically, first, the focus position when the start of calibration is instructed is detected. Next, the detected focus position is compared with the focus position obtained by referring to the latest projection distance measured by the distance measuring unit before the start of calibration with the data in the storage unit. Next, an offset amount is calculated from the shift amount between the two focus positions. Then, for example, the data in the storage unit is read, and after the data is shifted by the calculated offset amount, the data is corrected by writing in the storage unit.

  A focus adjustment method for an image projection apparatus according to the present invention includes a projection optical unit including a projection lens and an autofocus lens, and expands image light light-modulated in the projection optical unit by the projection lens to an external projection surface. A focus adjustment method for an image projection apparatus for projecting, wherein a projection distance from the projection lens to the projection surface is measured, and based on the measurement result, the position in the optical axis direction within the projection optical unit of the autofocus lens A focus position is obtained by referring to data indicating a correspondence relationship between the focus position and the projection distance stored in advance, an autofocus step of moving the autofocus lens to the obtained focus position, and after autofocus When the focus position is adjusted manually, the manually adjusted focus position is A calibration step for comparing the detected focus position with the focus position at the time of autofocus, calculating an offset amount from a shift amount between the two focus positions, and shifting data in the storage unit by the offset amount; Have.

In the focus adjustment method of the present invention, preferably, each step of the autofocus and the calibration is started based on an external operation, and an instruction to restart the autofocus is issued during the execution of the calibration. Even if there is an operation, the operation is invalidated.
Preferably, white light in which RGB color lights are mixed at a predetermined ratio is used as light for projecting an image during the autofocus step and the manual adjustment after the autofocus.

According to this focus adjustment method, the autofocus step is first executed.
In this step, first, the projection distance from the projection lens to the projection surface is measured. Next, based on the measurement result, the focus position, which is the position in the optical axis direction within the projection optical unit of the autofocus lens, is obtained with reference to the data indicating the correspondence between the focus position stored in advance and the projection distance. . Then, the autofocus lens is moved to the determined focus position.

Next, when the focus position is manually adjusted after autofocus, a calibration step is executed.
In this step, first, the manually adjusted focus position is detected. Next, the detected focus position is compared with the focus position at the time of autofocus, and the offset amount is calculated from the shift amount between the two focus positions. Then, the data in the storage unit is shifted by the offset amount.

  Even if there is an instruction to start autofocus again during execution of this calibration, if this is invalidated, reliable execution of the calibration is guaranteed. This prevents the user from instructing autofocus again as soon as the focus is out of focus even when the user performs autofocus, and in such a case, accurate data correction is not performed no matter what time. It is to do.

  Further, when white light is used during autofocusing and subsequent manual adjustment, correction is performed in consideration of the flange back balance value that differs for each RGB.

  According to the image projection apparatus of the present invention, not only mechanical variations such as the lens position of the projection lens and focus lens in the projection optical unit, but also data correction caused by variations in optical components on the light incident side of the projection lens. There is an advantage that the accuracy of the data in the storage unit can be improved.

  According to the focus adjustment method of the image projection apparatus of the present invention, there is an advantage that the accuracy of stored data referred to at the time of autofocus can be improved for the same reason as that of the image projection apparatus. Further, by performing calibration for improving the accuracy of the stored data when manual adjustment is performed after autofocus, there is an advantage that, for example, optimum data correction can be performed in a user's use environment.

  Hereinafter, an embodiment of the present invention will be described using a projector capable of projecting a color image as an example.

FIG. 1 is a configuration diagram viewed from the upper surface of a projector (image projection apparatus) according to the present embodiment.
A projector 1 shown in FIG. 1 includes a projection optical unit 3 including an optical lens unit 3A, a distance measuring unit 4, a focus / zoom motor 5, an AF control unit 6, and a projection optical unit 3 and AF in a housing 2 thereof. It has a main body control board 7 for controlling the entire projector including the control unit.

  The projection optical unit 3 includes a light source 30 including a reflector 30B and a lamp 30A disposed on the central axis thereof, a multi-lens array 31 including a filter for removing unnecessary light, dichroic mirrors 32R and 32G, and a relay lens 33A. Relay lens 33B, reflection mirrors 34R, 34B1 and 34B2, condenser lenses 35R, 35G and 35B, a liquid crystal display panel as a light modulation element and an incident side deflection plate and an output side analyzer (or an output side polarizing plate) sandwiching the liquid crystal display panel ) Liquid crystal panel blocks 36R, 36G and 36B, and a so-called 4P prism photosynthesis element 37.

The optical lens unit 3A is an assembly of ten or more lens groups including the projection lens 3Aa and the focus lens 3Ab, and is used for magnification adjustment and focus adjustment of a projected image.
The focus / zoom motor 5 is a motor that adjusts the position (focus position) of the focus lens 3Ab in the optical axis direction, and operates under the control of the AF control unit 6.

The light emitted from the lamp 30A in the projection optical unit 30 is reflected by the reflector 30B, collimated so as to be substantially parallel to the optical axis, and emitted from the opening of the reflector 30B.
The light emitted from the opening of the reflector 30B enters the multi-lens array 31, and after unnecessary light is removed by the filter, the light is adjusted to match the effective opening of the liquid crystal panel block.
Thereafter, the light is split into light of RGB colors by the two dichroic mirrors 32R and 32G. The red light is reflected by the dichroic mirror 32R, the optical path is bent by 90 degrees, further reflected by the reflection mirror 34R, and guided to the condenser lens 35R. The green light and the blue light are transmitted through the dichroic mirror 32R. Among them, the green light is reflected by the next dichroic mirror 32G, the optical path is bent by 90 degrees, and is guided to the condenser lens 35G. On the other hand, the blue light passes through the dichroic mirror 32G, and is guided to the condenser lens 35B through the relay lens 33A, the reflection mirror 34B1, the reversing relay lens 33B, and the reflection mirror 34B2.

  The light of each color that has been spectrally divided and entered into the corresponding condenser lens 35R, 35G, or 35B is incident on the corresponding liquid crystal panel block 36R, 36G, or 36B. In each of the liquid crystal panel blocks 36R to 36B of each color, the polarization direction of light is made constant by a polarizing plate, the intensity of light is modulated by a liquid crystal display panel, and light having a predetermined polarization plane by an analyzer. Only permeated. In the modulation of the light intensity by the liquid crystal display panel, the degree of modulation of each pixel on the liquid crystal display panel is determined corresponding to the input video signal, so that the bundle of light output from the liquid crystal display panel is indicated by the video signal. It has a light intensity distribution corresponding to an image for each color.

Thereafter, light beams (image light) of the respective colors are incident on the optical lens unit 3A in a state of being combined into one light beam (image light) from the light combining element 37.
The optical lens unit 3A converts the image indicated by the light beam incident from the light combining element 37 into a predetermined magnification, adjusts the focus, and projects the image onto the projection surface 130A of the screen 130 provided outside.

FIG. 2 is a block diagram showing details of the AF control unit 6.
The AF control unit 6 includes a microcomputer (μC) 61, a distance measuring IC 62 and a motor driver (circuit or IC) 63 controlled by the microcomputer 61.
Further, the microcomputer 61 includes a CPU 64, an instruction input side input / output unit (I / O) 65 from the main body control board 7, and a control side input / output unit connected to the distance measuring IC 62 and the motor driver 63 ( I / O) 66, and a RAM 67 and a PROM 68 connected to the CPU 64.
The operation of the AF control unit 6 (AF operation) will be described later.

  Next, the configuration of the distance measuring unit 4 and the distance measuring operation will be described.

FIG. 3 shows the configuration of the distance measuring unit 4 and the path of the distance measuring light during the operation together with the screen.
The distance measuring unit 4 includes units of a distance measuring light emitting unit 4A and a distance measuring light receiving unit 4B, and these units are arranged vertically in the housing 2 of the projector 1 in this case. FIG. 3 shows a case where the projector 1 is set up horizontally with respect to the installation surface and the screen 130 is set up perpendicular to the installation surface.

  The ranging light emitting unit 4A includes an infrared LED 41 as a light emitting element, and an infrared projection lens 42 for projecting an image of the projected infrared light Lp from the infrared LED 41 onto the screen 130. The ranging light receiving unit 4B includes a PSD (position sensitive detector) 43 as a light receiving element that receives the reflected infrared light Lr reflected and returned from the screen 130, and a light receiving lens 44. The light receiving lens 44 and the infrared projection lens 42 are arranged on an axis 45 perpendicular to the installation surface.

  The projected infrared light Lp from the infrared LED 41 is projected onto the screen 130 through the infrared projection lens 42 during distance measurement. At this time, the spot image of the projected infrared light Lp projected on the screen surface 130 needs to be a contrasting circular or left-right symmetrical rectangular infrared light pattern with the optical axis of the infrared projection lens 42 as the center. For this purpose, although not shown, a slit is usually provided between the infrared LED 41 and the infrared projection lens 42, and the spot shape of the projected infrared light Lp is defined according to the shape of the slit.

  Light (reflected infrared light) Lr scattered and reflected by the screen surface 130 is collected by the light receiving lens 44, whereby the infrared light pattern on the screen surface 130 is reduced and imaged on the light receiving surface of the PSD 43. . The PSD 43 has a vertically long line-shaped light-receiving surface, and the peak position in the light-receiving surface of the light intensity distribution generated by imaging changes according to the incident angle of the reflected infrared light Lr. The light received by the PSD 43 on the light receiving surface is converted into an electrical signal corresponding to the intensity thereof, and this electrical signal is output to the distance measuring IC 62 shown in FIG. The ranging IC 62 converts the input electrical signal into a digital value, and detects the peak position of the light intensity distribution of the received infrared light pattern from the digital value.

  More specifically, the position P0 where the optical axis 46 parallel to the optical axis of the projected infrared light Lp and passing through the center of the light receiving lens 44 intersects the PSD 43 is used as a reference for detecting the light receiving position. The distance measuring IC 62 detects a distance (hereinafter referred to as a light reception detection distance) D from the reference position P0 to the actual light reception detection position (peak position of the light intensity distribution) P1 based on the electrical signal output by the PSD 43.

Here, the projection distance Dp is defined as the distance between the axis 45 and the projection surface 130 </ b> A of the screen 130. The shaft 45 is designed to pass through the center in the lens width direction of the projection lens 3Aa in the optical lens unit 3A shown in FIG.
When the projection distance Dp is sufficiently longer than the distance (baseline length) D0 between the optical axis of the distance measuring light emitting unit 4A and the optical axis of the distance measuring light receiving unit 4B, the infrared reflected light Lr enters the light receiving lens 44 relatively straight. Therefore, the received light detection distance D detected by the distance measuring IC 62 is relatively small. When the screen surface 130 is gradually approached from this state and the projection distance Dp is shortened, the infrared reflected light Lr is incident on the light receiving lens 44 more obliquely, so that the light receiving detection distance D is gradually increased. growing. Therefore, the distance measuring IC 62 can calculate the projection distance Dp from the projector 1 to the projection surface 130A of the screen 130 by the triangulation method based on the magnitude of the light reception detection distance D.

Note that each unit of the distance measuring light emitting unit 4A and the distance measuring light receiving unit 4B may be placed horizontally.
However, in order to reduce the influence of the ranging error at the time of the oblique projection in the horizontal direction due to the projection from the position shifted laterally from the front of the screen, the ranging light emitting unit 4A and the ranging light receiving unit 4B are placed horizontally, and the PSD 43 It is desirable that the light receiving surface be horizontally long. This is because the spot image of the projected infrared light Lp is shifted in the width direction (lateral direction) of the PSD 43 at the time of oblique oblique projection in the lateral direction and hardly affects the light reception detection distance D.

Next, on the premise of this distance measuring method, the AF operation by the AF control unit 6 shown in FIG. 2 will be described.
First, an instruction to start AF control is input from the main body control board 7 to the CPU 64 via the I / O 65. The CPU 64 solves the I / O 66 and gives a distance measurement instruction to the distance measurement IC, whereby the distance measurement operation by the distance measurement unit 4 is started. That is, the projected infrared light Lp is emitted from the LED 41 of the distance measuring light emitting unit 4A shown in FIG. 3 toward the screen 130 via the infrared projection lens 42, and the reflected light (reflected infrared light) Lr passes through the light receiving lens 44. Through the PSD 43. A signal from the PSD 43 is input to the distance measuring IC 62 in FIG. 2, and the distance measuring IC (or the CPU 64) calculates the projection distance Dp by the method described above based on this signal.

The PROM 68 stores in advance an autofocus control program and data that associates the relationship between the projection distance Dp and the optical axis direction position (focus position) of the focus lens 3Ab (see FIG. 1).
The CPU 64 compares the calculated projection distance Dp with data stored in the PROM 68 to determine a focus movement amount for obtaining an optimum focus position, and uses this as a movement amount signal via the I / O 66 to drive the motor driver 63. Send to.
The motor driver 63 controls the focus / zoom motor 5 based on the input movement amount signal to move the focus lens 3Ab to the optimum focus position.

Thereby, one AF operation is completed.
In the RAM 67, for example, the projection distance Dp and the focus movement amount at the time of the AF operation are rewritable, and the focus amount is displayed or the next AF operation (or at the time of calibration: described later) as necessary. Used for.

  The specific format of the data stored in the PROM 68 is expressed by a function in which the amount of focus movement is a variable of the projection distance, and the design values such as the distance between the light modulation element and the projection lens and the mechanical amount of the lens are functions. It is treated as a fixed parameter.

FIG. 4 shows the positional relationship of the projection lens, the screen surface, and the light modulation element in the direction of the projection optical axis.
Assuming that focus is achieved during distance measurement, the projection distance Dp obtained by distance measurement is the distance from the central axis of the projection lens 3Ab to the screen surface 130A. The variable of the projection distance of the data function stored in the PROM 68 is an ideal projection distance Dp when this focus is achieved.
Further, the flange back Dfb treated as a fixed parameter of this function is a distance from the central axis of the back projection lens 3Ab to the imaging surface of the light modulation element 36 defined at the time of design.

  However, in the actual optical lens unit 3A (FIG. 1), mechanical quantities such as assembly errors of various lenses are different in each optical lens unit, and it is necessary to reflect them in the data in the PROM as function fixed parameters. . Further, the actual flange back Dfb 'also has a value shifted by ΔDfb from the flange back Dfb defined at the time of design.

If the focus is in front of the screen before the AF operation, this corresponds to the current projection distance Dp ′ being shorter than the correct projection distance Dp by ΔDp as shown in FIG. In this case, in the AF operation, the correct projection distance Dp is obtained by distance measurement, and the position of the focus lens 3Ab is shifted in the optical axis direction by an amount corresponding to the difference ΔDp from the current projection distance Dp ′.
At this time, the data in the PROM 68 is referred to. However, as described above, even if the ideal curve for the mechanical amount is reflected in the fixed parameter, the PROM 68 has a slight deviation from the ideal curve. May not be reflected in fixed parameters.
As for the flange back, the flange back Dfb at the time of design is reflected in the fixed parameter. However, since the deviation ΔDfb is not reflected in the fixed parameter, even if the deviation ΔDfb of the flange back performs the AF operation. This is the main factor that is out of focus. The reason for this is that the mechanical amount is strictly controlled by the optical lens unit component standards, and the deviation from the ideal curve is usually slight, but the flange back actually completes the assembly of the projector, and various characteristics are obtained. This is because the product-specific value is unknown only after adjustment.

The variation in flange back generally depends on the projection lens performance, the dimensional accuracy of the 4P prism that synthesizes the RGB modulated light, the thickness accuracy of the polarizing plate disposed on the output side of the RGB light modulation means, and the like. .
Therefore, if the focus movement amount of the data in the PROM 68 is not corrected by an amount corresponding to the variation of the flange back, it will not be focused even if the autofocus is operated, and it will always be at an arbitrary projection distance. The camera is out of focus.

  Therefore, in the present embodiment, correction is performed to give an offset value to the focus movement amount of the data in the PROM 68. This correction is called calibration, and when the AF operation is performed at the time of assembling the projector or when the AF operation is confirmed at the final inspection, it is out of focus, at the initial setting when the user uses the projector, or both Do.

As means for calibration, the present invention includes calibration start instruction means and calibration execution means.
The calibration start instruction means is a means for generating a calibration signal, which is displayed on the calibration switch (SW) 7A provided on the main body control board 7 shown in FIG. Any of the variables on the AF menu program whose state changes when operated with. Further, both the calibration switch (SW) 7A and variables on the AF menu program may be provided.
This calibration start instruction means is determined to be operated after manual adjustment of the focus lens position when there is a focus deviation due to AF operation in the procedure of assembly process or inspection process or manual for user etc. It has been.

The calibration execution means detects the focus position by manual adjustment when the calibration start is instructed, and refers to the detected focus position by referring to the projection distance Dp ′ at the time of the immediately preceding AF operation in the data in the PROM 68. Compare with the resulting focus position. At this time, if the projection distance Dp ′ at the time of the immediately preceding AF operation is temporarily stored in the RAM 67, that value may be used.
Then, the offset amount is calculated from the shift amount between the two focus positions, and the calibration is executed by shifting the data in the PROM 68 by the offset amount.

  For this purpose, the calibration execution means may be provided with a special control circuit. However, since the execution contents are numerical operations such as data comparison and data shift, the CPU 64 shown in FIG. Combined use. In this case, the calibration execution procedure is described on the program in the PROM 68.

Hereinafter, a specific procedure for calibration will be described with reference to FIGS. 5 and 6, mainly performed at the time of assembling or final inspection of the projector.
Here, FIG. 5 is a flowchart showing a calibration procedure. FIG. 6 shows control signals passed between the main body control board 7 shown in FIGS. 1 and 2 and the AF control unit 6 (strictly, the CPU 64).

In step ST1, first, the projector 1 is accurately set to the fixed projection position. Although the fixed projection position is arbitrary, the projector 1 is set in front of the screen, and the projection distance between the two is accurately set to a recommended distance or the like. Although the recommended distance varies depending on the product, for example, a distance of 2.7 m is used as a recommended distance for obtaining a 60-inch screen.
When the setting of the fixed projection position is completed, the projector 1 is activated in that state, and a predetermined AF image is projected. As the AF image, an image having a pattern in which a focus shift is easily visible is used.

  In this state, whether the zoom position is set to the TELE end or the WIDE end is set (step ST2). As shown in FIG. 6, a zoom direction identification signal S <b> 1 indicating whether the zoom movement (focus lens movement) is in the plus direction or the minus direction is sent from the main body control board 7 to the AF control unit 6 in accordance with this setting.

Subsequently, the AF operation is turned on (step ST3). At this time, as shown in FIG. 6, the autofocus drive signal S2 given from the main body control board 7 to the AF control unit 6 is switched from OFF to ON, and the AF operation is started.
The AF operation is executed by moving the focus lens 3Ab by the focus movement amount after obtaining the above-mentioned distance measurement operation, calculating the projection distance based on the result, and obtaining the focus movement amount referring to the data in the PROM 68.

The operator confirms the image after AF on the screen (step ST4), and if it is in focus, gives an OK instruction to the main body control board 7 and ends the process without calibration.
If out of focus, the operator manually operates the focus ring provided in the lens unit of the projector 1 in step ST5. At this time, the operator appropriately turns the focus ring in the direction of the focus FAR or the direction of the focus NEAR, and searches for an in-focus position while viewing the image.
As a result, as shown in FIG. 6, the focus movement direction (FAR or NEAR) and the movement amount ΔF of the focus movement amount signal S3 sent from the main body control board 7 to the AF control unit 6 are changed, and the manual focusing is finished. Along with it settles to a certain value.

If the operator determines that the subject is in focus, the operator then operates the calibration SW 7A provided on the main body control board 7 or the like to instruct the start of calibration (step ST6). In response to this, a calibration signal S4 is sent from the main body control board 7 to the AF control unit 6, and the calibration shown in step ST7 is executed.
Simultaneously with the start of the calibration, a signal S5 indicating that the calibration operation is being performed is sent from the AF control unit 6 to the substrate control board 7. While the signal S5 is valid, the substrate control board 7 invalidates this operation even if the operator gives another AF operation instruction.

The calibration operation will be described in detail. Upon receiving the calibration signal S4, the CPU 64 in the AF control unit 6 detects the focus movement direction (FAR or NEAR) and the movement amount ΔF during the manual adjustment received earlier. Hereinafter, the direction of focus movement (FAR or NEAR) and the movement amount ΔF are referred to as detection data.
Next, a focus position (hereinafter referred to as storage data) stored in advance corresponding to the detection data is read from the PROM 68. The stored data is focus position data (a focus direction and a movement amount from the reference position) at the current projection distance.
Next, the stored data is compared with the detected data.
As a result of the comparison, for example, the difference in the focus position of the detected data with reference to the stored data is obtained as an offset amount. The offset amount has a positive or negative polarity, and the polarity represents the direction of the focus position deviation.
The offset correction is performed by adding the offset amount to all the correspondence data between the projection distance and the focus correction amount in the PROM 68. As a matter of course, when the offset amount is a difference in the focus position of the stored data with reference to the detected data, the offset amount is subtracted from the corresponding data.

When the offset-corrected data is written back to the PROM 68, the process returns to step ST4 and prompts the operator to visually check whether the focus is correct.
At this time, if the focus is correct, the process ends. If the focus is not correct, steps ST5 to ST7 and ST3 and ST4 may be repeated again. The number of repetitions is arbitrary, but it does not make sense to do so many times. For example, if the focus is not achieved even if it is repeated once more, the process may be repeated from the fixed projection position setting in step ST1. .

  Although the calibration performed at the time of assembling the projector or at the final inspection has been described above, the basic procedure is the same as above even at the time of initial setting by the user. However, the AF operation and calibration are operations on a setting menu using a remote controller or the like. Also, what is characteristic in this case is that it is impossible to expect the user to set the correct position of the projector, and the setting menu is set at the position desired by the user.

In this case, the contents of the EPROM 68 are rewritten at the initial setting every time, but at that time, the optimum data setting can be made. In other words, during oblique projection, a distance measurement error due to oblique projection may occur depending on the positional relationship between the projector and the screen. However, if AF operation and calibration are performed while maintaining the set state, the distance measurement error will occur. The contents of the EPROM 68 are rewritten taking into account the above, and the optimum data is obtained in the setting state. Therefore, the focus adjustment at this time has an advantage that the accuracy becomes very high.
In that sense, it is preferable to employ a sequence that rewrites the contents of the EPROM 68 at each initial setting. Even in such a case, it is effective to increase the accuracy of the data in the EPROM 68 to some extent by calibration performed at the time of assembling or final inspection of the projector.

As described above, the method of shifting all data by one offset amount calculated from the AF operation performed at a fixed recommended distance and the manual adjustment requires a short calibration time. However, it is also possible to perform calibration using, for example, three offset amounts calculated by changing the distance.
However, considering the fact that the shape of the characteristic curve stored in the PROM 68 is almost determined by the characteristics of the optical lens unit, and the offset amount varies due to flange back or the like, several points can be obtained even if a single offset amount is used for calibration. Even if the offset amount is used, the effect is not often changed.
Therefore, in order to balance the calibration time and the effect, calibration using one offset amount is desirable.

  In addition, it is desirable to use white light that is a mixture of RGB three primary colors in a ratio that is normally used for an image projected during the AF operation and the calibration operation. The reason for this is to enable calibration at the balance point of the flange back to the projection lens and the three light modulation elements of RGB at the time of calibration using one offset amount.

  According to the embodiment of the present invention, in a projector having a triangulation autofocus function using infrared rays or the like, by adjusting the offset amount of the lens focus position according to the distance between the projection lens and the panel. Even if the distance (back focus) between the projection lens and the panel varies, there is an advantage that focusing can be performed with higher accuracy.

It is the block diagram which looked at the projector which concerns on embodiment of this invention from the upper surface. It is a block diagram which shows the detail of AF control part. It is a figure which shows the structure of a ranging part, and the path | route of the ranging light at the time of the operation | movement with a screen. It is a figure which shows the positional relationship of the projection optical axis direction of a projection lens, a screen surface, and a light modulation element. It is a flowchart which shows the procedure of the calibration method concerning embodiment of this invention. It is a figure which shows the control signal passed between a main body control board and AF control part at the time of calibration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Projector, 2 ... Housing | casing, 3 ... Projection optical part, 3A ... Engineering lens unit, 3Aa ... Projection lens, 3Ab ... Focus lens, 4 ... Distance measurement part, 4A ... Distance measurement light emission part, 4B ... Distance measurement light-receiving part , 6 ... AF control unit, 7 ... Main body control board, 7A ... Calibration switch, 130A ... Screen surface, Dp ... Projection distance, Dfb ... Flange back

Claims (5)

An image projection apparatus that has a projection optical unit including a projection lens and an autofocus lens, expands image light that is light-modulated in the projection optical unit, and projects the image light on an external projection surface.
A distance measuring unit for measuring a projection distance from the projection lens to the projection surface;
A storage unit that stores in advance data indicating a correspondence relationship between a projection position and a focus position that is an optical axis direction position in the projection optical unit of the autofocus lens;
An instruction means for starting calibration;
The focus position when the calibration start is instructed is detected, and the detected focus position is referred to the data in the storage unit with the latest projection distance measured by the distance measuring unit up to the start of calibration. A calibration execution means for calculating an offset amount from a shift amount between two focus positions and shifting data in the storage unit by the offset amount,
An image projection apparatus. An autofocus control means for obtaining a focus position by referring to data stored in the storage unit for the projection distance measured by the distance measuring unit, and controlling the autofocus lens at the determined focus position;
2. The calibration start instruction means is an operation means that is operated when focus is shifted on the projection surface when the image is projected at a focus position controlled by an autofocus control means. The image projection apparatus described in 1. A projection optical unit including a projection lens and an autofocus lens, and a focus adjustment method for an image projection apparatus that enlarges the image light that is light-modulated in the projection optical unit and projects the image light on an external projection surface,
A projection distance from the projection lens to the projection surface is measured, and based on the measurement result, a focus position that is a position in the optical axis direction within the projection optical unit of the autofocus lens is stored in advance as the focus position. A step of auto-focusing obtained by referring to data indicating a correspondence relationship with the projection distance, and moving the auto-focus lens to the obtained focus position;
When the focus position is manually adjusted after autofocus, the manually adjusted focus position is detected, the detected focus position is compared with the focus position at the time of autofocus, and the amount of deviation between the two focus positions Calculating an offset amount from the calibration step, and shifting the data in the storage unit by the offset amount;
Adjusting method of image projection apparatus having Each step of the autofocus and the calibration is started based on an external operation, and the operation is invalidated even if there is an operation to start the autofocus again during the calibration. The focus adjustment method of the image projection apparatus according to claim 3. The focus adjustment of the image projection apparatus according to claim 3, wherein white light in which RGB color lights are mixed at a predetermined ratio is used as light for projecting an image during the auto-focusing step and the manual adjustment after the auto-focusing. Method.

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