JP2011182164A - Shading correction method, and projector with shading correction function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To acquire image data suitable for creating shading correction data and perform shading correction. <P>SOLUTION: A shading correction method has an imaging means which includes a light that illuminates an object and an optical system that generates images of the object, and a projection display device which projects images generated by the imaging means onto a screen. The shading correction method creates shading correction data based on the maximum value Lmax of image data Lj that are acquired when the imaging means generates images of a white reference plate, and then corrects shading caused by nonuniformity of lighting of a projector. A gain G of the imaging means is changed, and the difference between the maximum value Lmax and a prespecified reference value Lref is calculated for every changing of the gain G. It is determined whether the difference is within a prespecified range Dalw, and if it is within the range, the maximum value Lmax is used as the reference value. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a projector, and in particular, automatically generates video data having a luminance suitable for creating shading correction data used to correct shading caused by uneven illumination when an opaque document is imaged by an imaging unit. It relates to the technology to obtain.

  2. Description of the Related Art Conventionally, a projector including a projection display device that enlarges and projects an image from an optical imaging means (hereinafter simply referred to as a document camera) composed of a personal computer, a CCD camera, a CMOS sensor, or the like has been used.

  In particular, projectors that can handle video from document cameras are easy to use because there is no need to bother copying opaque manuscripts onto transparent OHP sheets, and can also save resources and reduce waste, enabling presentations that conserve resources. It is useful from. Visualization by a document camera is performed by placing a document face down on a glass for placing a document, and illuminating the document surface of the document with an illumination device such as a fluorescent lamp, and then imaging with a CCD camera, CMOS sensor, or the like. Realized.

As described above, in order to capture an opaque document with a document camera, it is necessary to illuminate the opaque document using an illumination device such as a fluorescent lamp to ensure a certain brightness. However, since the amount of light hitting this illumination is uneven, the level of the video signal output from the document camera becomes uneven (hereinafter referred to as shading), and the clarity of the projected document differs within the document. there were.
In order to solve this problem, a method of correcting shading has been proposed (for example, Patent Document 1).

JP 2000-299882 A (prior art)

As described in Patent Document 1, the basic principle of the shading correction technique is described in the section of the prior art, and is as follows.
First, a maximum value (maximum luminance) Lmax in digital video data obtained by reading a blank sheet with a camera is obtained.

Subsequently, the shading data SHD (x, y) is calculated as follows.
SHD (x, y) = Lmax / L (x, y) (1)
In Expression (1), L (x, y) is a value (luminance value) of an arbitrary pixel in the video data. The calculation of Expression (1) is performed for all pixels of the video data, and shading data (same as the above-mentioned shading correction data) SHD (x, y) is stored.

As described above, in the technique described in Patent Document 1, an image suitable for obtaining shading data is disclosed only by using the highest luminance data of a digital image obtained under illumination with a certain luminance as a reference. The data acquisition method is not specified.
In other words, it is desirable that the video data serving as the reference data in creating the shading data has the highest brightness within a range where the video data obtained by the document camera does not saturate, so that such video data can be obtained. It is a premise.

However, such video data can be obtained for the first time by adjusting the gain and offset of the document camera, particularly the gain, without changing the brightness of the lighting device from the viewpoint of effectively utilizing the dynamic range of the document camera. .
In this adjustment, digital video data, which is the video from the document camera before shading correction, is observed with a waveform observation device such as an oscilloscope via a D / A converter and a connector, and this video data reaches the maximum value that does not saturate. Although manual adjustment methods are conceivable, there are problems in that the adjustment itself takes time and individual differences occur, leading to an increase in manufacturing costs and a decrease in reliability. In addition, there is a problem that the addition of parts resulting only from such manufacturing requirements is contrary to the size and weight reduction of the device, which is a market requirement.

  The present invention has been made to solve such problems, and automatically changes the gain for amplifying the video obtained by the document camera while reading the video data obtained from the document camera at each time point. By selecting and setting the gain that automatically amplifies the video obtained by the document camera by matching the maximum value of this video data and the set reference value, the brightness suitable for creating shading correction data is set. A first object is to provide a shading correction method for obtaining video data, and a second object is to provide a projector having a shading correction function for obtaining such video data and performing shading correction.

  The shading correction method according to claim 1, wherein illumination for illuminating an object, imaging means including an optical system for imaging the object, and a projection display apparatus for projecting an image obtained by the imaging means onto a screen A shading correction data is generated and corrected based on the maximum value Lmax in the video data Lj obtained when the white reference plate is imaged by the imaging means. In this shading correction method, the gain G of the imaging means is changed, and the difference between the maximum value Lmax and a predetermined reference value Lref is obtained each time the change is made, and this difference is within a predetermined range. It is determined whether or not it falls within the Dalw, and the maximum value Lmax when falling within the range is used as a reference.

  The shading correction method according to claim 2 is characterized in that the change direction of the gain is changed from a larger one of the video data Lj to a smaller one.

  The shading correction method according to claim 3, wherein the video data Lj is obtained by dividing each video data in one frame obtained by the imaging unit or a video of one frame into a plurality of predetermined regions. It is an average value of individual video data in the area.

  The shading correction method according to claim 4 is characterized in that the difference is a difference or a ratio between the maximum values Lmax and Lref.

  According to a fifth aspect of the present invention, there is provided a projector comprising: an illumination that illuminates an object; an imaging unit that includes an optical system that images the object; and a projection display device that projects an image obtained by the imaging unit onto a screen. Shading for generating shading correction data based on the maximum value Lmax in the video data Lj obtained when the white reference plate is imaged by the imaging means with shading caused by uneven illumination. A projector including a correction unit, wherein the gain G of the imaging means, Lref that is a reference value of the maximum value Lmax, and Dalw that is an allowable value of a difference between the Lref and Lmax are set; The difference between the maximum value Lmax of the video obtained for each set gain G and the reference value Lref is the allowable value Da. Control whether w is within the range; when it is determined that the range is out of the range, the gain G is changed in a direction to reduce the difference and finally within the range is performed. A control unit is provided.

  The projector according to claim 6 is characterized in that the change of the gain is changed from the larger one of the video data Lj to the smaller one.

  The projector according to claim 7, wherein the video data Lj is individual video data in one frame obtained by the imaging means, or each area when a video of one frame is divided into a plurality of predetermined areas. The average value of the individual video data.

  The projector according to an eighth aspect is characterized in that the difference is a difference or a ratio between the maximum values Lmax and Lref.

  As described above, according to the first to fourth aspects of the present invention, the white reference plate is selected as the object, the gain of the imaging means is automatically changed, and the image obtained from the imaging means each time. The difference between the maximum value in the data and the reference value is obtained, and a gain is selected so that the difference falls within the allowable value range. In other words, since the video data obtained when the finally selected gain is set becomes the video data having a luminance suitable for creating the shading correction data required, the gain can be easily selected and set. Since there is no individual difference, it is possible to provide a shading correction method that contributes to reduction in manufacturing cost and improvement in reliability.

  In particular, according to the second aspect of the present invention, the luminance of the video data obtained from the imaging means is changed from a higher level to a lower level. Therefore, an effect that an appropriate gain can be found at an early stage can be obtained.

  According to the fifth to eighth aspects of the present invention, since the means for automatically determining the gain according to the first to fourth aspects is provided, a shading correction function that contributes to a reduction in manufacturing cost and an improvement in reliability is provided. Projectors can be provided.

It is a schematic block diagram of the projector provided with the shading correction function according to the present invention. It is a flowchart figure which shows the acquisition method of video data suitable for the shading correction data preparation used for the shading correction method which becomes this invention.

Next, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic block diagram of a projector having a shading correction function according to the present invention, and FIG. 2 is a flowchart showing a video data acquisition method suitable for creating shading correction data used in the shading correction method according to the present invention. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are indispensable as means for solving the present invention. Not always.

  A projector having a shading correction function in FIG. 1 includes a camera module 1, a shading correction module 2, a memory control module 3, a frame memory 4, a DMD control unit 5, and a CPU 6.

  The camera module 1 visualizes an object, and includes a CMOS sensor 11 that is an image sensor including an optical system (not shown) as a main component. The CMOS sensor 11 performs photoelectric conversion and amplifies electric charges by external gain setting. The shading correction module 2 eliminates shading caused by uneven illumination of the video obtained by the camera module 1, and a fine gain adjustment unit 21 that finely adjusts the luminance of video data from the camera module 1 by changing the gain. The shading correction data storage unit 22 that stores the completed shading correction data, and the data between the shading correction data storage unit 22 and the video data from the camera module 1 via the gain fine adjustment unit 21 correspond to corresponding pixels or regions. The main component is the shading correction unit 23 that executes an operation that eliminates shading.

  The memory control unit 3 develops the video data from the shading correction module 2 in the frame memory 4, converts the resolution of the video data in frame units from the frame memory 4, and performs video processing such as image quality correction. The frame memory 4 stores the developed video data and the like in units of frames.

  The DMD control unit 5 receives the video data subjected to the video processing from the memory control unit 3 and controls the light source, color wheel, etc. (not shown) to enlarge and project via the DMD and the projection lens.

  The CPU 6 controls the execution of shading correction, and a gain table 61a (for example, from 256 combinations of gains) that stores gains used in the CMOS sensor 11 of the camera module 1 and the gain fine adjustment unit 21 of the shading correction module 2 is used. And selecting and setting a set of gains from this table (selection and setting of gain will be described later). Gain selection / setting unit 61, video suitable for shading correction data creation When data is obtained, shading correction data is created using this video data, and a shading correction data calculation unit 62 that stores the created shading correction data in the shading correction data storage unit 63 is a main component. In addition, the shading correction data calculation unit 62 transfers the shading correction data stored in the shading correction data storage unit 63 to the shading correction data storage unit 22 of the shading correction module 2 as necessary (for example, when the power is turned on). .

  Next, a video data acquisition method suitable for creating shading correction data used in the shading correction method according to the present invention will be described mainly with reference to FIG.

  Since shading correction data is created, a white reference plate (or equivalent article) is placed on the document table (not shown) as the object to be imaged, and the projector is turned on by operating the power switch of the projector (not shown). To do.

  At this time, an initialization process is first executed, and the gain selection / setting unit 61 of the CPU 6 reads a predetermined combination of initial gains from the gain table 61a, and performs a fine gain adjustment of the CMOS sensor 11 and the shading module 2 of the camera module 1. The adjustment unit 21 is set (S201 in FIG. 2). Here, the combination of the initial gains should be selected so that the luminance of the video data is as high as possible (for example, the 200th gain combination). This is because the desired video data should have higher luminance. Here, the shutter speed of the CMOS sensor 11 is fixed to the maximum.

  By setting the gain, the video data of the white reference plate imaged by the camera module 1 is input to the gain selection / setting unit 61 of the CPU 6 through the gain fine adjustment unit 21 of the shading correction module 2 (see FIG. 2 S202).

  Based on the image data of the white reference plate input in this way, the average luminance level Lave, n (n is a division) for each divided area (for example, divided into 32 × 64 areas) determined in advance by the gain selection / setting unit 61. Number) is calculated (S203 in FIG. 2). Thereafter, the maximum value Lmax is determined from the average value Lave, n (S204 in FIG. 2).

  Next, a difference between the maximum value Lmax and a reference value Lref that is the luminance of video data suitable for creating predetermined shading correction data is calculated (S205 in FIG. 2). Then, it is determined whether or not the difference is within a predetermined allowable range Dalw (S206 in FIG. 2).

  If the result of this determination does not fall within the allowable range Dalw (No in S206 of FIG. 2), the gain is reset according to the positive or negative of the difference (S207 of FIG. 2). Specifically, if the difference is positive, the luminance is too high and a gain combination that reduces the luminance is selected from the gain table 61a, and the gain fine adjustment of the CMOS sensor 11 of the camera module 1 and the shading correction module 2 is performed. Set in part 21. On the other hand, if the difference is negative, the brightness is too low, so a gain combination that increases the brightness is selected and set.

  In this way, when the newly selected gain is set in the CMOS sensor 11 of the camera module 1 and the gain fine adjustment unit 21 of the shading correction module 2, the luminance of the video data of the white reference plate is set according to the set gain. Change.

  Subsequently, the procedure from “video data input of the white reference plate from the CMOS sensor” to “whether the difference falls within the allowable range” shown in S202 to S206 of FIG. 2 is repeated.

This reselection of gain and resetting of gain after reselection are repeated until “the difference falls within the allowable range”.
Thus, the video data of the white reference plate obtained by the gain setting when “the difference is within the allowable range” becomes video data suitable for creating shading correction data.

  Although the present embodiment has been described in detail as described above, it should be readily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention.

  For example, “ratio” is obtained instead of “difference”, and it is determined whether or not this ratio falls within an allowable range. When the ratio does not fall within the allowable range, the gain is reselected depending on whether the ratio exceeds 1 or not, and is reset.

  In this embodiment, the shutter speed of the CMOS sensor 11 is fixed to the maximum. However, the shutter speed can be fixed in accordance with the CMOS sensor to be used, and the shutter speed is difficult to control as necessary. Can be made variable.

  The shading correction data can be calculated using the above-described equation (1), and the calculated shading correction data is stored in the shading correction data storage unit 63, and the shading correction data storage of the shading correction module 2 is stored as necessary. The data is transferred to the unit 22, and shading correction is executed.

1 camera module, 2 shading correction module, 3 memory control unit,
4 frame memory, 5 DMD controller, 6 CPU, 11 CMOS sensor,
21 gain fine adjustment unit, 22 shading correction data storage unit,
23 Shading correction unit, 61 Gain selection / setting unit,
61a gain table, 62 shading correction data calculation unit,
63 Shading correction data storage unit

Claims (8)

Due to uneven illumination of a projector having illumination that illuminates an object, imaging means including an optical system that images the object, and a projection display device that projects an image obtained by the imaging means on a screen A shading correction method for creating and correcting shading correction data based on a maximum value Lmax in video data Lj obtained when a white reference plate is visualized by the imaging means.
The gain G of the imaging means is changed, and a difference between the maximum value Lmax and a predetermined reference value Lref is obtained each time the change is made, and it is determined whether or not the difference falls within a predetermined range Dalw. The shading correction method is characterized in that the maximum value Lmax when it falls within the range is used as a reference. 2. The shading correction method according to claim 1, wherein the change of the gain is changed from the larger one of the video data Lj to the smaller one. The video data Lj is the individual video data in one frame obtained by the imaging means, or the average value of the individual video data in each region when one frame of video is divided into a plurality of predetermined regions. The shading correction method according to claim 1, wherein:   The shading correction method according to claim 1, wherein the difference is a difference or a ratio between the maximum values Lmax and Lref. Shading caused by uneven illumination, comprising illumination for illuminating an object, imaging means including an optical system for imaging the object, and a projection display device that projects an image obtained by the imaging means onto a screen A shading correction unit that generates shading correction data and performs shading correction based on the maximum value Lmax in the video data Lj obtained when the white reference plate is visualized by the imaging means. There,
Setting gain G of the imaging means, Lref which is a reference value of the maximum value Lmax, and Dalw which is an allowable value of a difference between the Lref and Lmax; an image obtained for each set gain G Determining whether or not the difference between the maximum value Lmax and the reference value Lref is within the range of the allowable value Dalw; if it is determined that the difference is out of the range, the gain G is changed in a direction to reduce the difference A projector comprising a control unit that performs each control of finally being within a range. 6. The projector according to claim 5, wherein the change of the gain is changed from the larger one of the video data Lj to the smaller one. The video data Lj is the individual video data in one frame obtained by the imaging means, or the average value of the individual video data in each region when one frame of video is divided into a plurality of predetermined regions. The projector according to claim 5, wherein:   6. The projector according to claim 5, wherein the difference is a difference or a ratio between the maximum values Lmax and Lref.

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