JP2007271760A - Projector and its autofocus control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve continuous autofocus in a projector. <P>SOLUTION: When a power source is turned on, a predetermined pattern is projected to a screen, and range-finding is performed by a range-finding unit. Distance data is calculated from a pair of output sensor data, and a focus motor is driven to perform focusing based on the data. Next, an image for viewing is projected to the screen. When the contrast of the image for viewing is very low, it is judged as a range-finding error, and focusing by the predetermined pattern is maintained as it is, then range-finding by the image for viewing is performed after three seconds elapse. When the distance data is normally obtained, it is compared with the distance data used in the previous focusing. When change exceeding a first threshold is found, a projection lens is focused based on the distance data obtained by use of the image for viewing. When the change is not found, range-finding by the image for viewing is performed at the intervals of three seconds until the power source is turned off. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a projector including an autofocus device and an autofocus control method thereof.

  Projectors that project and display images are known to have an autofocus function that automatically adjusts the focus of a projected image in order to facilitate focus adjustment of the projected image (for example, Patent Document 1). As a distance measuring apparatus that provides this autofocus function, a passive distance measuring system is adopted.

  In the passive ranging method, a correlation calculation is performed based on output signals of a pair of light receiving sensors on which a pair of subject images formed by external light from the subject is formed, and the maximum correlation value obtained by the correlation calculation is obtained. In this method, the distance to the subject is calculated based on the minimum minimum value (peak value) indicating the degree of correlation.

The passive ranging method is effective when the subject image has a certain level of brightness and / or contrast, but auxiliary light is required otherwise. Since the projector is used indoors, auxiliary light is required to perform autofocus by the passive distance measuring method. Furthermore, since the screen has a uniform white surface, it is necessary to project an image of a predetermined pattern, not just auxiliary light. Since the projection of the predetermined pattern cannot naturally be performed simultaneously with the original projection image, it is performed before the projection of the projection image is started, or as described in Patent Document 1, only for a very short time that cannot be perceived by humans. The projection is performed instead of the projection image, and the distance measuring operation is performed in synchronization with the projection.
JP 2004-233115 A

  By the way, in order to perform continuous autofocus with the projector described in Patent Document 1, the original projection image and the image of the predetermined pattern are frequently switched and projected. For this reason, although it is said that a predetermined pattern is projected for a time that cannot be perceived by humans, frequent switching between the projected image and the predetermined pattern image will cause adverse effects such as flickering of the projected image and complicated control. There is a problem of becoming.

  It is an object of the present invention to provide a projector and an autofocus control method thereof that can perform continuous autofocus without causing a projected image to flicker.

  In order to achieve the above object, the projector according to the present invention is a passive method that obtains distance measurement data corresponding to the distance to the projection surface by receiving light from the projection surface on which an image for viewing is projected from the projection lens. And a projection unit for projecting the appreciation image and a storage unit for storing image data of a predetermined pattern projected for distance measurement in a projector that focuses the projection lens based on the distance measurement data. Before the image data of the predetermined pattern is read from the storage unit and the predetermined pattern is projected, the first distance measurement data corresponding to the distance to the projection surface is obtained, and the projection lens of the projection lens is obtained based on the first distance measurement data After focusing, the second distance measurement data corresponding to the distance to the projection surface is obtained by stopping the projection of the predetermined pattern and projecting an image for viewing. If a change exceeding the predetermined first threshold value occurs between the distance measurement data used for the previous focusing and the second distance measurement data, the second measurement is continued. A control unit is provided that performs focusing of the projection lens based on the distance data and maintains the previous focus position of the projection lens when the change does not occur.

  The control unit may maintain the previous focus position of the projection lens as it is when a distance measurement error occurs in the second distance measurement data. Further, the control unit causes a change exceeding the first threshold value between the distance measurement data used for the previous focusing and the second distance measurement data, and the second distance measurement data varies, and the variation. If the degree of is larger than a predetermined second threshold, the previous focus position of the projection lens is maintained as it is, and if the degree of variation is smaller than the second threshold, the second distance measurement data is used. And focusing the projection lens.

  The projector autofocus control method according to the present invention is a passive distance measurement method that obtains distance measurement data corresponding to the distance to the projection surface by receiving light from the projection surface on which an image for viewing is projected from the projection lens. In a projector autofocus control method for focusing a projection lens based on the distance measurement data, by projecting a predetermined pattern created for distance measurement before projecting the appreciation image. A first step of obtaining first distance measurement data corresponding to the distance to the projection surface, a second step of focusing the projection lens based on the first distance measurement data, and stopping the projection of the predetermined pattern for viewing A third step of continuously obtaining second distance measurement data corresponding to the distance to the projection surface at predetermined time intervals by projecting an image for use; A fourth step of detecting whether or not a change exceeding a predetermined first threshold value occurs between the distance measurement data used for the previous focusing and the second distance measurement data; and when the change occurs, The fifth step of focusing the projection lens based on the second distance measurement data and the sixth step of maintaining the previous focus position of the projection lens when the change does not occur are provided. And

  Further, when a distance measurement error occurs in the second distance measurement data, the previous focus position of the projection lens is maintained as it is. Further, a change exceeding the first threshold value occurs between the distance measurement data used for the previous focusing and the second distance measurement data, and there is a variation in the second distance measurement data, and the degree of the variation is a predetermined value. When it is larger than the second threshold, the previous focus position of the projection lens is maintained as it is, and when the degree of variation is smaller than the second threshold, the focus of the projection lens is based on the second distance measurement data. It is characterized by combining.

  According to the present invention, the first distance measurement data corresponding to the distance to the projection surface is obtained by projecting the predetermined pattern created for distance measurement before projecting the image for viewing, and the first distance measurement data. After focusing on the projection lens based on the above, the second distance measurement data corresponding to the distance to the projection surface is continuously obtained at predetermined time intervals by stopping the projection of the predetermined pattern and projecting the image for viewing. At the same time, when a change exceeding the predetermined first threshold value occurs between the distance measurement data used for the previous focusing and the second distance measurement data, the projection lens is changed based on the second distance measurement data. When focusing is performed and the change does not occur, the focus position of the previous projection lens is maintained as it is, so that the image for viewing projected on the screen does not flicker, and continuous autofocus can be achieved. That.

  In addition, when a distance measurement error occurs in the second distance measurement data, the previous focus position of the projection lens is maintained as it is, so that a stable focus can be obtained without the projection lens focus position fluctuating. In addition, a change exceeding the first threshold value occurs between the distance measurement data used for the previous focusing and the second distance measurement data, and the degree of variation of the second distance measurement data is greater than the predetermined second threshold value. If it is larger, the previous focus position of the projection lens is maintained as it is, so that erroneous focus adjustment can be prevented, for example, when a person who has moved in front of the projector is measured. Further, when the degree of variation of the second distance measurement data is smaller than the second threshold value, the projection lens is focused based on the second distance measurement data. For example, after the projector has been moved to a new location. Focusing can be performed automatically.

  In FIG. 1 showing the appearance of a liquid crystal projector with an autofocus device according to an embodiment of the present invention, the projection lens 12 is opened from the opening formed on the front surface of the housing by opening the lens cover when the liquid crystal projector 10 is used. Exposed. A zoom dial 13 and a focusing dial 14 are provided on the casing, and the projection lens 12 can be zoomed and focused by manually operating these. The focus adjustment dial 14 is provided with a mark for automatic focus adjustment, and when this is adjusted to an index attached to the housing, the projection lens 12 is automatically focused.

  An autofocus device is incorporated in the housing so that the projection lens 12 can be automatically focused. The autofocus device 15 includes a passive distance measuring unit 16 to be described later and a lens driving unit 17 that moves the focus lens of the projection lens 12 based on distance data obtained from the distance measuring unit ( (See FIG. 2). In addition, a pair of light receiving lenses 18 and 19 of the distance measuring unit 16 are arranged in the horizontal direction above the projection lens 12.

  In FIG. 2 showing the electrical configuration of the liquid crystal projector, the distance measuring unit 16 includes a microcomputer 20, an EEPROM 22, and a line sensor unit 26. The lens driving unit 17 includes a focus lens driving circuit 25, a focus motor 32, and a rotary encoder 36.

  A transmissive liquid crystal display (LCD) 38 is provided behind the projection lens 12. The LCD 38 is driven by an LCD driving unit 39 controlled by the microcomputer 20 and displays an image for projection. A projection lamp 40 is provided behind the LCD 38, and a display image on the LCD 38 is projected onto the screen 42 via the projection lens 12 by illumination light from the lamp 40.

  The microcomputer 20 reads image data of a predetermined pattern created for distance measurement in addition to initial setting data and adjustment data written in the EEPROM 22, and sends appropriate commands to the signal processing circuit 24 and the focus lens driving circuit 25. , And the autofocus process consisting of the distance measuring process of the distance measuring unit 16 and the focusing process of the lens driving unit 17 is totally controlled. The predetermined pattern is, for example, a high-contrast image pattern composed of black and white vertical stripes.

  The signal processing circuit 24 controls the line sensor 30 in accordance with a command from the microcomputer 20 and performs signal processing such as receiving and integrating a detection signal described later from the line sensor 30.

  The line sensor unit 26 includes a pair of light receiving lenses 18 and 19, a line sensor 30 including a pair of R sensors 30 a and L sensors 30 b disposed to face each other, and a signal processing circuit 24. The line sensor 30 is composed of, for example, a photodiode divided into 224 pieces.

  Images projected on the screen 42 are formed on the light receiving surfaces of the R sensor 30a and the L sensor 30b by the light receiving lenses 18 and 19, respectively. The R sensor 30a and the L sensor 30b output detection signals indicating images formed on the respective light receiving surfaces, and the line sensor 30 outputs detection signals indicating a pair of images.

  When the microcomputer 20 instructs the signal processing circuit 24 to start integration of the detection signal output from the line sensor 30, the signal processing circuit 24 starts integration of the detection signal, and when the accumulation level reaches a predetermined value, the microcomputer 20 An integration end signal is output to the computer 20.

  In response to an output instruction from the microcomputer 20 to the signal processing circuit 24, a pair of accumulated signals (sensor data) are output from the signal processing circuit 24 to the microcomputer 20, respectively. A pair of sensor data input to the microcomputer 20 is converted into digital data by an A / D converter 20a provided therein, and similarly stored in a RAM provided therein.

  The microcomputer 20 performs a predetermined calculation (a well-known passive calculation for calculating the distance to the subject based on the correlation calculation and the minimum minimum correlation value obtained thereby) on the pair of sensor data. The distance data is calculated, and the distance data is input to the focus lens driving circuit 25. The focus lens driving circuit 25 drives the focus motor 32 according to the input distance data, and moves the focus lens 34 that is a part of the projection lens 12 from the home position.

  The drive of the focus motor 32 is monitored by the rotary encoder 36, and the focus lens drive circuit 25 stops the motor 32 when the motor 32 reaches the rotation amount corresponding to the distance data from the microcomputer 20 while receiving the feedback signal. Let As a result, the focus lens 34 stops at a position corresponding to the distance data on a one-to-one basis, and focusing is completed. Of course, it is also possible to control the drive and stop of the focus motor 32 while monitoring the movement amount of the focus lens 34.

  When the focus dial 14 is manually operated, the focus motor 32 is driven according to the operation amount, and the movement of the focus lens 34 can be manually adjusted while observing the focus of the image projected on the projection surface 20. it can. When the zoom dial 13 is manually operated, the zoom motor 39 is driven according to the operation amount, and the zoom lens which is a part of the projection lens 12 is moved to perform zooming.

  When the zooming is performed, the moving amount of the focus lens 34 for focusing also changes. However, the position information of the variable power lens is input to the microcomputer 20, and the microcomputer 20 takes the position information of the variable power lens into consideration. Since the obtained distance data is input to the focus lens driving circuit 25, the projection lens 12 is similarly focused.

  The autofocus process of the liquid crystal projector 10 configured as described above will be described with reference to the flowchart shown in FIG. A personal computer (not shown) for displaying an image for viewing on the LCD 38 is connected to the liquid crystal projector 10 in advance.

  First, when the power of the liquid crystal projector 10 is turned on (st1), the microcomputer 20 reads image data of a predetermined pattern for distance measurement from the EEPROM 22, inputs it to the LCD drive unit 39, and displays an image of the predetermined pattern on the LCD 38. And the lamp 40 is turned on. Thereby, a predetermined pattern is projected on the screen 42 (st2).

  An image of a predetermined pattern projected on the screen 42 is formed on the light receiving surfaces of the R sensor 30 a and the L sensor 30 b via the light receiving lenses 18 and 19. As a result, a detection signal indicating a pair of images is input from the line sensor 30 to the signal processing circuit 24 and integrated. The pair of sensor data is input from the signal processing circuit 24 to the microcomputer 20, converted into digital data by the A / D converter 20a, and stored in the RAM (st3).

  The microcomputer 20 stops displaying the image of the predetermined pattern on the LCD 38 (st4), and then performs a predetermined calculation on the pair of sensor data stored in the RAM to calculate distance data (st5). The distance data is input to the focus lens driving circuit 25. The focus lens drive circuit 25 drives the focus motor 32 according to the distance data to move the focus lens 34 from the home position, and stops the motor 32 when the rotation amount corresponding to the distance data is reached. Focusing is completed (st6).

  Thereafter, when the user operates the personal computer to send the image data of the viewing image to be projected to the liquid crystal projector 10, the microcomputer 20 displays the viewing image on the LCD 38 via the LCD drive unit 39. Thereby, an image for viewing is projected on the screen 42 through the projection lens 12, and the image for viewing is formed on the light receiving surfaces of the R sensor 30a and the L sensor 30b through the light receiving lenses 18 and 19, A pair of sensor data is input from the signal processing circuit 24 to the microcomputer 20, converted into digital data by the A / D converter 20a, and stored in the RAM (st7).

  The microcomputer 20 tries to calculate distance data by performing a predetermined calculation on the pair of sensor data stored in the RAM. If the contrast of the viewing image is very low, the microcomputer 20 calculates the distance data. Cannot be performed, resulting in a ranging error (st8). When this distance measurement error occurs, the focus is maintained based on the distance data obtained by distance measurement using the predetermined pattern. For example, after 3 seconds (st9), the same as above A distance measurement process using an image for viewing is performed (st7).

  When the distance data is normally obtained without causing the distance measurement error (st10), the microcomputer 20 is used for the previous focusing with the distance data obtained by the distance measurement by the viewing image. It is verified whether there is a change exceeding a predetermined first threshold between the distance data (st11). The first threshold value is distance data corresponding to an allowable range of the distance in the direction of the light projecting optical axis 18a that is determined to be in focus when the image projected on the projection surface 20 is viewed from the user. The distance data corresponds to 30 mm.

  The distance data used for the previous focusing is distance data obtained by distance measurement by the predetermined pattern at the beginning of distance measurement by the viewing image, and is obtained by distance measurement by the viewing image. After focusing is performed based on the distance data, the distance data obtained by the distance measurement using the viewing image is obtained.

  When there is the change (st11), it is considered that the liquid crystal projector 10 has been moved to a new place or position, and therefore the microcomputer 20 projects based on the distance data obtained by the distance measurement using the viewing image. The lens 12 is focused (st12). If there is no change (st11), the microcomputer 20 continues to perform distance measurement using an image for viewing, for example, every 3 seconds (st9) unless the power of the liquid crystal projector 10 is turned off (st13). (St7).

  In this way, immediately after the power is turned on, the distance measurement and focusing is performed once according to the predetermined pattern, and thereafter the distance measurement based on the viewing image is continued without performing the distance measurement according to the predetermined pattern. As a result, the liquid crystal projector 10 can be continuously focused automatically without flickering the image for viewing projected on the screen.

  Next, another embodiment will be described with reference to FIG. In addition, the same step number is attached | subjected to the step of the same content shown in FIG. 3 of the said embodiment, and description is abbreviate | omitted. In step 11 (st11), if there is a change exceeding the first threshold value between the distance data obtained by distance measurement using the viewing image and the distance data used for the previous focusing, the distance data Are stored and stored in the RAM of the microcomputer 20 (st21). When the distance data reaches N (for example, N = 3) (st22), these variations are calculated (st23).

  When the variation is larger than the predetermined second threshold (st24), the previous focus position of the projection lens 12 is maintained as it is unless the power is turned off (st13). For example, after 3 seconds (st9), A distance measurement process using the same image for viewing is performed (st7). The case where the variation is larger than the second threshold includes, for example, a case where a person who has moved in front of the liquid crystal projector 10 is measured, and an erroneous focusing operation in such a case is prevented.

  If the variation is smaller than the second threshold value (st24), the projection lens 12 is focused based on the average value of N distance data obtained by distance measurement using the viewing image (st12). . In addition, as a case where the variation is smaller than a predetermined second threshold value, for example, a scene in which the liquid crystal projector 10 has been moved to a new location or position is assumed, and new focusing is automatically performed.

  In the embodiment described above, the distance measurement using the predetermined pattern is performed immediately after the power is turned on. However, the distance measurement using the predetermined pattern is automatically performed at the start of the first projection after the power is turned on. May be. In the above-described embodiment, the distance measurement process using the viewing image is performed at intervals of 3 seconds. Of course, the interval time is not limited to 3 seconds.

  In the above embodiment, the distance measurement is continuously performed from the time the power is turned on until the power is turned off. You may make it stop. In this case, when starting the distance measurement again, it is preferable to perform an operation such as manually operating the focusing dial.

  In the above embodiment, the predetermined pattern is a black and white vertical stripe pattern, but the present invention is not limited to this, and any image pattern may be used as long as it is a high contrast image pattern. Moreover, in the said embodiment, although the arrangement direction (baseline length direction) of a pair of light receiving lenses was made into the horizontal arrangement | sequence, it is good also as a vertical arrangement.

  The first threshold value is distance data corresponding to 30 mm. However, the present invention is not limited to this. For example, the first threshold value corresponds to 10 mm or 50 mm as long as it is within an allowable range. It may be distance data. Further, although the number N of distance data stored and accumulated in the RAM is “3”, the present invention is not limited to this, and may be “5”, for example.

1 is an external view of a liquid crystal projector using the present invention. It is a block diagram which shows the electrical structure of a ranging unit and a lens drive unit. It is a flowchart which shows the main sequences of the autofocus process concerning this invention. It is a flowchart which shows the main sequences of the autofocus process in another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal projector 12 Projection lens 15 Autofocus apparatus 16 Distance measuring unit 17 Lens drive unit 20 Microcomputer 22 EEPROM
24 signal processing circuit 26 line sensor unit 30 line sensor 34 focus lens 38 LCD
42 screens

Claims (6)

A passive distance measuring device is provided that obtains distance measurement data corresponding to the distance to the projection surface by receiving light from the projection surface on which an image for viewing is projected from the projection lens, and based on the distance measurement data In a projector that focuses the projection lens,
A storage unit for storing image data of a predetermined pattern projected for distance measurement;
Before projecting the image for viewing, the image data of a predetermined pattern is read from the storage unit and the predetermined pattern is projected to obtain first distance measurement data corresponding to the distance to the projection surface. After focusing the projection lens based on the data, the second distance measurement data corresponding to the distance to the projection plane is obtained at predetermined time intervals by stopping the projection of the predetermined pattern and projecting an image for viewing. If a change exceeding the predetermined first threshold value occurs between the distance measurement data used for the previous focusing and the second distance measurement data, the continuous distance measurement is performed based on the second distance measurement data. And a control unit that focuses the projection lens and maintains the previous focus position of the projection lens when the change does not occur.   The projector according to claim 1, wherein the control unit maintains the previous focus position of the projection lens as it is when a distance measurement error occurs in the second distance measurement data.   The control unit causes a change exceeding the first threshold between the distance measurement data used for the previous focusing and the second distance measurement data, and there is a variation in the second distance measurement data, and the degree of the variation. Is larger than the predetermined second threshold value, the previous focus position of the projection lens is maintained as it is, and when the degree of variation is smaller than the second threshold value, projection is performed based on the second distance measurement data. 3. The projector according to claim 1, wherein the lens is focused. Based on the distance measurement data, a passive distance measurement method is used to obtain distance measurement data corresponding to the distance to the projection surface by receiving light from the projection surface on which an image for viewing is projected from the projection lens. In the autofocus control method of the projector that focuses the projection lens,
A first step of obtaining first distance measurement data corresponding to the distance to the projection surface by projecting a predetermined pattern created for distance measurement before projecting the image for viewing;
A second step of focusing the projection lens based on the first distance measurement data;
A third step of continuously obtaining second distance measurement data corresponding to the distance to the projection surface by stopping the projection of the predetermined pattern and projecting an image for viewing at predetermined time intervals;
A fourth step of detecting whether or not a change exceeding a predetermined first threshold value occurs between the distance measurement data used for the previous focusing and the second distance measurement data;
A fifth step of focusing the projection lens based on the second distance measurement data when the change occurs;
And a sixth step of maintaining the previous focus position of the projection lens as it is when the change does not occur.   5. The projector autofocus control method according to claim 4, wherein when a distance measurement error occurs in the second distance measurement data, the previous focus position of the projection lens is maintained as it is.   A change exceeding the first threshold value occurs between the distance measurement data used for the previous focusing and the second distance measurement data, and there is a variation in the second distance measurement data, and the degree of the variation is a predetermined second value. When it is larger than the threshold value, the previous focus position of the projection lens is maintained as it is, and when the degree of variation is smaller than the second threshold value, the projection lens is focused based on the second distance measurement data. 6. The autofocus control method for a projector according to claim 4, wherein the autofocus control method is performed.

Images