JPH063577A - Focusing device and its method - Google Patents

Abstract

PURPOSE:To realize a focusing device and its method by which focusing is accurately performed without being influenced by the level of brightness in an area where focusing is performed and also focusing is performed even for an area or a direction optionally selected. CONSTITUTION:A projector 2 projecting an image based on an input signal on a display screen, a camera 3 picking up the image projected on a screen 1, a computing element 6 calculating the sum of the positive power of the absolute value of a difference between data adjacent to each other in an image signal based on image pickup, and a projector controller 7 performing the focusing of the projected image by the projector 2 so that the sum total may be maximum are provided to accurately perform focusing without being influenced by the level of brightness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for adjusting the focus of a lens or CRT (Cathode Ray Tube) surface of a display device such as a projector.

[0002]

2. Description of the Related Art As a conventional focus adjusting device, for example, a video signal is obtained from a signal received by a CCD (Charge Coupled Device) image pickup device and photoelectrically converted, and this video signal is taken out from a specific line in a predetermined area. The signal is separated as a luminance signal, the luminance signal is converted from an analog signal to a digital signal by an analog / digital (A / D) converter, and the sum of the differences between adjacent data of the digital luminance signal is obtained. A system is known in which the focus adjustment system is driven so that the total sum becomes maximum (for example, Japanese Patent Laid-Open No. 61-262382).
reference).

This is shown in FIG.
This is because the sharpness of the image becomes higher as shown by the solid line curve. Focus adjustment by this method generates a signal for focus adjustment by detecting high frequency components in the video signal. As compared with the so-called frequency detection method, there is an advantage that the focus adjustment can be surely performed without malfunction.

[0004]

However, in the above-mentioned conventional focus adjusting device, as shown in FIG. 5A, when the focus indicated by the solid line is in focus, the focus indicated by the broken line is better. There is no problem when the brightness is higher than when there is no brightness, but as shown in (b) of FIG. 5, when the brightness is the same when the focus shown by the solid line and the case where the focus is not shown by the broken line are equal. Has the drawback that the sum of the differences between adjacent data becomes equal and accurate focus adjustment cannot be performed.

Further, in the above-mentioned device or a focus adjusting device having a special infrared sensor or a precise optical device, a desired arbitrary region is focused, or only the horizontal and vertical directions are focused. That was impossible.

The present invention has been made in view of the above circumstances, and an object of the present invention is to perform accurate adjustment without being influenced by the brightness of the area where focus adjustment is performed and to select an arbitrarily selected area. It is to provide a focus adjusting device and a method therefor capable of adjusting the direction and the direction.

[0007]

In order to achieve the above object, in the focus adjusting apparatus of the present invention, a means for projecting an image based on an input signal on a display screen, and an image projected on the display screen are picked up. Means, means for calculating a sum of positive powers of absolute values of differences between mutually adjacent data in an image signal based on imaging, and means for performing focus adjustment of a projected image by the projection means so that the sum becomes maximum. And have.

In the focus adjusting apparatus of the present invention, means for projecting an image based on an input signal on a display screen, means for extracting a luminance signal from an image signal based on imaging, and converting the analog signal into a digital signal, A means for calculating the sum of the positive powers of the absolute values of the differences between the digital brightness data adjacent to each other, and a means for adjusting the focus of the projected image by the projection means so that the sum is maximized are provided.

In the focus adjusting method of the present invention, the image projected on the display screen is picked up, the sum of the positive powers of the absolute values of the differences between the adjacent data in the image signal based on the picked-up image is calculated, and this sum is calculated. Adjust the focus of the projected image so that it becomes maximum.

In the focus adjusting apparatus of the present invention, the image projected on the display screen is picked up, the luminance signal is extracted from the image signal based on the picked-up image and converted from the analog signal to the digital signal, and the digital luminance data adjacent to each other is extracted. The sum of the positive powers of the absolute value of the difference is calculated, and the focus of the projected image is adjusted so that the sum becomes maximum.

[0011]

According to the focus adjusting apparatus of the present invention, the image based on the input signal is projected on the display screen by the projection means. The image projected on the display screen is captured by the image capturing means. The sum of the positive powers of the absolute values of the differences between the adjacent data in the image signals obtained by the image pickup is calculated, and the focus of the projection image is adjusted by the projection unit so that the sum becomes maximum.

According to the focus adjusting device of the present invention, the image based on the input signal is projected on the display screen by the projection means. The image projected on the display screen is captured by the image capturing means. A luminance signal is extracted from the image signal obtained by imaging, and this analog signal is converted into a digital signal. The sum of the positive powers of the absolute values of the differences between the digital brightness data adjacent to each other of this digital signal is calculated, and the focus adjustment of the projection image by the projection means is performed so that this sum becomes maximum.

According to the focus adjusting method of the present invention, the image projected on the display screen is picked up, and the sum of the positive powers of the absolute values of the differences between the adjacent data in the image signals obtained by the picking up is calculated. , The focus of the projected image is adjusted so that the total sum becomes maximum.

According to the focus adjusting method of the present invention, the image projected on the display screen is imaged, the luminance signal is extracted from the image signal obtained by the image pickup, and the analog signal is converted into a digital signal. The sum of the positive powers of the absolute values of the differences between the digital brightness data adjacent to each other of this digital signal is calculated, and the focus of the projected image is adjusted so that this sum becomes maximum.

[0015]

1 is a block diagram showing an embodiment of a focus adjusting device according to the present invention. In FIG. 1, 1 is a screen, 2 is a projector, 3 is a CCD camera (hereinafter,
4 is analog / digital (A /
D) Converter, 5 is a frame memory, 6 is a computing unit, and 7 is a projector controller.

The projector 2 projects an image on the screen 1 by performing a predetermined process such as synchronous separation from the input video signal. Further, although not shown, a color shift adjustment system, a focus adjustment system for the projected image, and the like are provided. As the focus adjustment system, a lens focus adjustment system that moves the optical lens group for image projection in the forward and reverse directions on the optical axis,
A cathode ray tube focus adjustment system for adjusting the focus coil of the cathode ray tube.

The camera 3 is arranged so as to be able to capture an image projected on the screen 1. The A / D converter 4 is
The video signal from the camera 3 is quantized and converted from an analog signal to a digital signal. The frame memory 5 is A / D
One screen portion of the digital data by the converter 4 is stored.

The arithmetic unit 6 calculates the amount of luminance inclination of the area for focus adjustment from the data stored in the frame memory 5. Specifically, the sum of squares of the differences between the digital luminance data adjacent to each other is calculated.

Now, the calculation of the amount of brightness inclination will be described in more detail with reference to FIG. FIG. 2 shows a luminance cross-sectional view of a region in which an image changes from black to white. Generally, the more in focus, as shown by the solid line A in FIG.
The edge rises sharply. Now, the brightness of the focused image at the positions of x _1, x ₂ ... Sampling is F _1, F ₂ ... (Solid line A), and the brightness of the unfocused image is U _1, U ₂ ... ( The broken line B). In this case, looking at the contrast amount, since the black level and the white level have the same luminance, the sum of the differences between adjacent data | F ₁ −F ₂ | + | F ₂ −F ₃ | + ... + | F ₇ -F ₈ | _{a, | U 1 -U 2 | +} | U 2 -U 3 | + ... + | U 7 -U 8 | and both the _{(F 8 -F 1), (} U 8 -U 1) becomes Will be equal. Therefore, in order to give a weight to the difference between adjacent data and make the value larger when this is larger, the difference is set to 2 as shown in equations (1) and (2) below.
It is configured to take the sum and take the sum. F _X = Σ (F _n-1 −F _n ) ² = (F ₁ −F ₂ ) ² + (F ₂ −F ₃ ) ² +… + (F ₇ −F ₈ ) ² … (1) U _X = Σ (U _n-1 −U _n ) ² = (U ₁ −U ₂ ) ² + (U ₂ −U ₃ ) ² +… + (U ₇ −U ₈ ) ² … (2) When comparing with this value, F _X having a larger difference value has a larger value. That is, by using this calculation, it is possible to obtain a larger value for an image with a larger luminance gradient.

The projector controller 7 includes a computing unit 6
Drive control of the focus adjustment system of the projector 2 is performed so that the total sum of squares of the differences between the adjacent data is maximized based on the calculation result of.

Next, the focus adjusting operation with the above configuration will be described with reference to FIGS. 3 and 4. A test signal is input to the projector 2 (S1), a range for focus adjustment is set (S2), and an image based on the input signal is projected on the screen 1. This projected image is
The image signal captured by the camera 3 and obtained by a predetermined process such as photoelectric conversion is converted from an analog signal to a digital signal by the A / D converter 4, and one screen of digital image data is stored in the frame memory 4. Done (S
3).

The digital image data stored in the frame memory 5 is taken out by the arithmetic unit 6 and is processed as described above.
Based on equation (1), the sum of the squares of the differences between the adjacent image data in the area designated as the focus adjustment range, that is, the amount of luminance inclination is calculated, and the calculated value is stored in a memory (not shown) as reference data. (S4).

Next, the focus data is changed to slightly shift the focus (S5). The projected image on the screen 1 at this time is the same as the case described above.
The image signal captured by
The analog signal is converted into a digital signal by the / D converter 4, and digital image data for one screen is stored in the frame memory 5 (S6).

The digital image data stored in the frame memory 5 is taken out by the arithmetic unit 6 and, as in the case described above, the sum of the squares of the differences between the adjacent image data in the area designated as the focus adjustment range. That is, the brightness inclination amount is calculated (S7). Then, in comparison with the reference data, the projector controller 7 determines whether or not the calculated value is the maximum (S8), the correction value of the focus position is calculated, and the focus adjustment system is set so that the brightness tilt amount becomes the maximum. Drive control is performed. That is, so-called auto focus adjustment is performed, and the focused image is projected on the screen 1.

FIG. 4 shows a frame memory 5 in which an image input from the camera 3 is taken in when the above-mentioned focus adjustment is actually performed, an arbitrary area 51 in the frame memory 5 to be subjected to focus adjustment, and each pixel of the area 51. 7 shows an example of the luminance data. Here, the brightness data DT of each pixel in the area 51 is set to D _{11 to} D _mn as shown in FIG. If you want to focus horizontally,
The brightness gradient amount S _{H in the} horizontal direction is calculated by the calculator 6 as shown in (3) below.
It is calculated based on the formula. _{S H = (D 11 -D 12} ) 2 + (D 12 -D 13) 2 + ... + (D 1n-1 -D 1n) 2 + (D 21 -D 22) 2 + (D 22 -D 23) ² + ... + (D _2n-1 -D _2n ) ² + (D _m1 -D _m2 ) ² + (D _m2 -D _m3 ) ² + ... + (D _mn-1 -D _mn ) ² ... (3) Projector In the controller 7, the focus adjustment system of the projector 2 is drive-controlled so that the horizontal luminance inclination amount _SH becomes maximum.

When it is desired to focus in the vertical direction, the calculator 6 calculates the vertical luminance inclination amount S _V as follows.
It is calculated based on equation (4). _{S V = (D 11 -D 21} ) 2 + (D 21 -D 31) 2 + ... + (D m + 1 -D m1) 2 + (D 12 -D 22) 2 + (D 22 -D 32) _{^{2 + ... + (D m +}} 2 -D m2) 2 + (D 1n -D 2n) 2 + (D 2n -D 3n) 2 + ... + (D m-1n -D mn) 2 ... (4) projector In the controller 7, the focus adjustment system of the projector 2 is drive-controlled so that the vertical direction brightness inclination amount S _V becomes maximum.

When it is desired to focus the entire area 51, the total brightness gradient amount S _T = S _H + S _V ,
The focus adjustment system of the projector 2 is drive-controlled so that S _T becomes maximum.

As described above, according to this embodiment,
The image signal captured by the camera 3 is quantized, and the sum of the squares of the differences between the adjacent brightness data is obtained to obtain the amount of inclination of brightness, and focus adjustment is performed so that this amount of inclination of brightness is maximized. Since the configuration is such that the sum of the squares of the differences between adjacent luminance data does not become equal even if the luminance is the same when the focus is in focus and when the focus is out of focus, accurate focus adjustment is required. Thus, it is possible to realize a highly reliable focus adjustment device that can accurately adjust the focus adjustment of the display so that the contrast does not change even when the focus is out of focus.

Further, it is possible to adjust the arbitrarily selected area and direction. Therefore, if the focus is adjusted for each area by autofocusing the lens of a display that uses a lens such as a projector, OHP, or projector, or the CRT surface beam focus of a display that uses a CRT, especially by using the electromagnetic focus method Focus can be adjusted for each.
In adjusting the focus coil that determines the shape of the CRT surface beam, the adjustment can be performed while checking both the horizontal and vertical beam diameters so that the beam is close to a perfect circle.

Further, since the image output from the camera is processed, it can be performed by a commercially available camera. Since the projector installation adjustment is performed while looking at the image on the screen, it is not affected by the projector installation state.

In this embodiment, the amount of inclination of the brightness is obtained by calculating the sum of squares of the differences between the adjacent brightness data, but the present invention is not limited to the sum of squares. By obtaining the sum of the positive powers of the absolute value of the difference between the adjacent data, the same effect as the above-mentioned effect can be obtained.

[0032]

As described above, according to the present invention,
Even if the brightness is the same when the focus is in and out of focus, the total sum of the positive powers of the absolute values of the differences between the adjacent brightness data is not the same, so accurate focus adjustment can be performed, For example, it is possible to realize a highly reliable focus adjustment device capable of accurately adjusting the focus adjustment of the display so that the contrast does not change even when the focus is out of focus. In addition, it is possible to adjust the area and direction that are arbitrarily selected, which is effective for electromagnetic focus adjustment and focus coil adjustment of a CRT, for example.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a focus adjustment device according to the present invention.

FIG. 2 is a diagram showing a luminance cross section of a region in which an image changes from black to white.

FIG. 3 is a flowchart for explaining a focus adjustment operation according to the present invention.

FIG. 4 is a diagram showing a frame memory in which an image input from a camera is captured, an arbitrary region in the frame memory in which focus adjustment is desired, and an example of luminance data of each pixel in the region.

FIG. 5 is a diagram for explaining a conventional problem.

[Explanation of symbols]

 1 ... Screen 2 ... Projector 3 ... CCD Camera 4 ... Analog / Digital (A / D) Converter 5 ... Frame Memory 6 ... Arithmetic Unit 7 ... Projector Controller

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04N 5/74 A 9068-5C

Claims (4)

[Claims] 1. A means for projecting an image based on an input signal on a display screen, a means for capturing an image projected on the display screen, and an absolute value of a difference between adjacent data in the image signal based on the imaging. A focus adjustment apparatus comprising: a unit that calculates the sum of positive powers; and a unit that adjusts the focus of a projected image by the projection unit so that the total sum becomes maximum. 2. A means for projecting an image based on an input signal onto a display screen, a means for capturing an image projected on the display screen, a luminance signal extracted from the image signal based on the capturing, and an analog signal from the analog signal. Means for converting into a digital signal, means for calculating a sum of positive powers of absolute values of differences between digital luminance data adjacent to each other, and focus adjustment of a projection image by the projection means so that the sum becomes maximum. A focus adjusting device comprising: 3. An image projected on a display screen is picked up, a sum of positive powers of absolute values of differences between adjacent data in an image signal based on the picked-up image is calculated, and projection is performed so that this sum becomes maximum. A focus adjustment method characterized by performing focus adjustment of an image. 4. An image projected on a display screen is picked up, a luminance signal is extracted from an image signal based on the picked-up image and converted from an analog signal to a digital signal, and the absolute value of the difference between adjacent digital luminance data is positive. A focus adjustment method characterized by calculating the total sum of powers of and adjusting the focus of the projected image so that the total sum becomes maximum.