JPH10339840A - Lens focusing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens focusing device capable of forming a distinct image on an image pickup unit without using a rangefinder. SOLUTION: A CCD 4 fetches the image of an object formed by a lens 1 as image data, and the contour value calculation means of a contour value detector 7 calculates the total sum of the difference of a picture element value concerning a detection unit consisting of one or plural picture elements out of image data between the detection unit and a detection unit around the detection unit, and the contour value totaling means of the detector 7 totals the total sum of the difference of the picture element value calculated concerning the detection unit and further totals it concerning plural detection units. Then, a contour value comparator 8 allows a focusing unit 3 to move the lens 1 along an optical axis to a position where the total sum calculated by the contour value totaling means is larger so as to vary a distance to the object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a lens focusing device that captures an image of an object formed by a lens as image data and controls the position of the lens based on the image data.

[0002]

2. Description of the Related Art Conventionally, in a digital camera, an image of an object is formed by a lens, and the image is captured by an image pickup device as image data. And
When capturing image data, it is necessary to clearly form an image of an object on an image pickup device. Therefore, the position of a lens is moved by focusing control by a lens focusing device.

An example of a digital camera equipped with such a lens focusing device will be described with reference to FIG. In this digital camera, an image of an object is formed on a CCD (charge coupled device) 13 by a lens 11 and an aperture 12, and the formed image is captured by the CCD 13 as analog data, and captured by the CCD 13. The A / D (analog / digital) converter 14 converts the analog data image data into digital data image data, and stores the digital data image data in the frame memory 15. 15 can extract image data.

In this digital camera, a lens focusing device measures a distance to an object by a distance measuring device 17 and inputs information of a lens position corresponding to the distance to a focusing device 16.
By moving the position of the lens 11 in accordance with the information with the focuser 16, the lens 11 is brought into the focused position, that is,
It is moved to a position where a clear image can be formed on the CCD 13.

[0005]

However, the above-mentioned conventional lens focusing apparatus had to be provided with a distance measuring device for measuring the distance to the object. When using the distance measuring device, the distance measuring device and the lens need to capture the same object, so that the direction of the distance measuring device is oriented in the same direction as the direction of the lens. Had to be placed. For this reason, when the conventional lens focusing device is used for a device such as a digital camera or the like, restrictions on the design of the device have become severe, which has been an obstacle in reducing the size of the device.

The present invention has been made in view of the above-described conventional circumstances, and provides a lens focusing apparatus which can form a clear image on an image pickup device without using a distance measuring device. Aim.

[0007]

To achieve the above object, a lens focusing apparatus according to the present invention captures an image of an object formed by a lens as image data, and based on the image data, captures an image of an object. A lens focusing device for controlling a position, a lens moving means for moving a lens along an optical axis to change a distance to an object, and capturing an image of the object formed by the lens as image data. An imaging unit, a contour value calculating unit that calculates, for a detection unit including one or more pixels in the image data, a sum of pixel value differences between the detection unit and detection units around the detection unit, and a detection unit. The sum of the pixel value differences calculated for the plurality of detection units is further summed up, and the lens is positioned at a position where the sum calculated by the contour value summing means is larger. And focusing means for moving the lens by moving means, characterized by comprising a.

Here, the difference in pixel value between the detection unit and the detection unit around the detection unit does not only mean the difference of the pixel value of the detection unit as it is, but, for example, weights each pixel value. After the difference is also included.

In the above-described lens focusing apparatus according to the present invention, the imaging means captures an image of the object formed by the lens as image data, and the contour value calculation means comprises one or a plurality of pixels in the image data. About the detection unit,
The sum of pixel value differences between the detection unit and the detection units around the detection unit is calculated, and the contour value summing means calculates the sum of pixel value differences calculated for the detection unit, and further for a plurality of detection units. Sum up. Next, the focusing unit moves the lens along the optical axis by the lens moving unit to a position where the sum calculated by the contour value summing unit is larger, and changes the distance to the object.

Here, the fact that the sum of the differences between the pixel values of the detection unit and the surrounding detection units and the sum of the plurality of detection units is larger means that the image of the object being picked up has a larger value. This indicates that the image is clearly formed. Therefore, a clear image can be formed on the image pickup device by moving the lens to a position where the total value of the plurality of detection units is larger. It is preferable that the lens is moved to a position where the sum of the plurality of detection units is maximized.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a digital camera provided with a lens focusing device according to one embodiment of the present invention will be described with reference to FIG. This digital camera captures an image of a target object via a lens 1, an aperture 2 for adjusting the amount of light from the lens 1, a focus unit 3 for moving the position of the lens 1, and the lens 1 and the aperture 2. CCD 4, an A / D converter 5 for converting an analog signal into a digital signal, a frame memory 6 for storing image data, a contour value detector 7 for calculating a sum of contour values, A contour value comparator 8 that controls the focusing device 3 based on the summation, and a memory 9 that holds a calculation result by the contour value detector 7 are provided.

The frame memory 6 and the contour detector 7
, The contour value comparator 8 and the focus unit 3 are connected by a data / control bus 10. Here, the lens focusing device includes a CCD 4, an A / D converter 5, a frame memory 6, a contour value detector 7, a contour value comparator 8, and a memory 9
And a configuration using components such as a CCD 4, an A / D converter 5, and a frame memory 6 included in the digital camera.

In accordance with a control signal from the contour value comparator 8, the focuser 3 moves the lens 1 along the optical axis to change the distance between the lens 1 and the object. Means of transportation. The CCD 4 is a lens 1
And image capturing means for capturing an image of the object formed through the aperture 2 as image data of analog data for each frame.
Output to the / D converter 5. The A / D converter 5 is a CCD 4
And converts the analog image data into digital data, and sends the converted digital image data to the frame memory 6. Frame memory 6
Stores the image data of the digital data received from the A / D converter 5 as image data for each frame.

The contour value detector 7 calculates, for a pixel (detection unit) in the image data stored in the frame memory 6, the total sum (contour value) of the difference between the pixel value and the pixel around the pixel. Contour value calculating means to be calculated, and a plurality of pixels (for example, 20 × 20 pixels at the center in image data)
And a contour value summing means for summing the contour values calculated with respect to. The contour value calculating means applies a contour value g (x, x, y) to the pixel (x, y) in the image data stored in the frame memory by applying the following equation (1).
y) is calculated. In this embodiment, the contour value is calculated for each pixel constituting the central 20 × 20 pixels in the image data.

[0015]

(Equation 1)

Here, "i" indicates the relative position in the X-axis direction between the pixel (x, y) for calculating the contour value and the pixel used for calculation, and "j" indicates the Y-axis direction. Represents the relative position of. Also, f (x + i, y + j) is a pixel (x +
i, y + j). H (i, j) is
This is a kernel for detecting an outline, and a pixel (x, y)
Is a numerical value multiplied by the pixel value of the pixel at (i, j). In the present embodiment, as a contour value of a certain pixel, a 3 × 3 pixel including the pixel and eight pixels around the pixel is used.
The contour value is calculated using pixels, and h (i, j) is represented by the equation (2).

According to the above equation (1), the contour value of a certain pixel is calculated as the value obtained by subtracting the pixel values of the upper, lower, left and right pixels from the value obtained by quadrupling the pixel value of a certain pixel. The larger the pixel value change with surrounding pixels, the more
This indicates that the absolute value of the contour value is large. From this, when the lens position with respect to the same object is changed, the closer the lens is to the in-focus position, the larger the pixel value change between a certain pixel and surrounding pixels becomes, so the lens is closer to the in-focus position. It can be said that the absolute value of the contour value is larger as the value is larger.

When a contour value of a pixel is calculated using a 5 × 5 pixel composed of the pixel and 24 pixels surrounding the pixel, h (i, j) is calculated as follows.
For example, the expression (3) can be used. In this case, “i” in the expression (1) is set to a value of −2 to 2, and “j” is set to −. What is necessary is just to take the numerical value of 2-2.

The contour value summing means sums up the absolute values of the contour values of the pixels constituting the central 20 × 20 pixels in the image data calculated by the contour value calculating means, and fetches the image data. Is stored in the memory 9 in association with the lens position.

The contour value comparator 8 detects the largest sum of the contour values corresponding to the lens positions stored in the memory 9 and moves to the lens position at which the sum of the contour values becomes the largest. There is a focusing means for outputting a control signal for moving the lens 1 to the focusing device 3.

Next, the operation of the above digital camera will be described. In this digital camera, a lens 1 and an aperture 2
Forms an image of an object on the CCD 4, captures the image formed by the CCD 4 as image data of analog data, and the A / D converter 5 converts the image data captured by the CCD 4 from analog data to digital data. After conversion, the image data of the digital data is stored in the frame memory 6. Thereby, the user can use the image data stored in the frame memory 6 as necessary,
Processing such as display output on a display device (not shown) or storage in a storage medium such as a floppy disk can be performed.

Here, in order to capture the image of the object as clearer image data in the above-described operation, the lens focusing device moves the position of the lens 1 as described below to form an image on the CCD 4. Focus control for sharpening the image of the target object to be performed is performed. That is, when the lens 1 and the aperture 2 are C
An image of the object is formed on the CD 4, the image formed by the CCD 4 is captured as analog data, and the A / D converter 5 converts the image data captured by the CCD 4 from analog data to digital data. Then, the image data of the digital data is stored in the frame memory 6.

Next, the contour value calculating means of the contour value detector 7 calculates a contour value for a pixel in the image data stored in the frame memory 6, and the contour value summing means calculates the center value of 20 × 20 in the image data. The contour values calculated for the pixels are summed up and stored in the memory 9 in correspondence with the lens position when the image data was fetched. Then, the focusing device 3 sequentially moves the lens position, repeats the same operation as described above, and stores the sum of the contour values corresponding to the plurality of lens positions in the memory 9.

As described above, after the sum of the contour values corresponding to the plurality of lens positions is stored in the memory 9, the contour value comparator 8 determines the largest sum of the contour values stored in the memory 4. Then, the lens position corresponding to the maximum sum of the contour values, that is, the in-focus position is detected. FIG. 2 shows the correspondence between the sum of the contour values and the lens position, and also shows the focusing position of the lens in this case. Next, the contour value comparator 8 outputs a control signal for moving the lens 1 to the detected in-focus position, and the focus unit 3 moves the lens 1 according to the control signal. Therefore, a clear image of the object is formed on the CCD 4, and the object can be captured as clearer image data.

In the above-described embodiment, a detection unit composed of one pixel is used.
A detection unit including a plurality of pixels such as three pixels can be used. In this case, the pixel value of the detection unit is, for example, a sum of pixel values of a plurality of pixels constituting the detection unit or an average of the pixel values. May be used.

The image data is R (red), G (green),
In the case of image data having three components such as B (blue), the above-described invention can be carried out using at least one of these three components. For example, if the image data has components such as Y (luminance), I, and Q in the NTSC system, or if the image data has components such as Y (luminance), U, and V in the PAL system, for example, Y ( The invention described above can be carried out using the (luminance) component.

In the above embodiment, the processor controls the focusing process of the lens focusing device by executing the control program stored in the ROM, the RAM, or the like. Each functional unit that executes the processing may be configured as an independent hardware circuit.

The present invention can be widely applied not only to a digital camera such as a still camera or a video camera, but also to a camera that needs to perform focusing control for imaging an object.

[0029]

As described above, according to the lens focusing apparatus according to the present invention, the detection unit composed of one or a plurality of pixels in the image data of the imaged object is the detection unit and the detection unit. Calculate the sum of the pixel value differences with the surrounding detection units, sum the pixel value differences calculated for the detection units, and further sum for multiple detection units, and place the lens at a position where the sum is greater. By moving along the optical axis to change the distance to the object, it is possible to form a clear image of the object on the image pickup device without having a distance measuring device, and clear image data Can be captured. Further, in a device such as a digital camera, the use of the lens focusing device eliminates the need for providing a distance measuring device, so that costs can be reduced and restrictions on device design can be eased.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a digital camera including a lens focusing device according to the present invention.

FIG. 2 is a diagram showing a correspondence relationship between a sum of contour values and a position of a lens and a focus position.

FIG. 3 is a configuration diagram of a digital camera including a conventional lens focusing device.

[Explanation of symbols]

1. Lens, 2. Aperture, 3. Focuser,
4. CCD, 5 A / D converter, 6 frame memory, 7 contour detector, 8 contour value comparator, 9 memory, 10 data control bus.

Claims (1)

[Claims] 1. A lens focusing device for capturing an image of an object formed by a lens as image data and controlling a position of the lens based on the image data, wherein the lens is moved along an optical axis. Lens moving means for changing the distance to the object by means of an imaging means for capturing an image of the object formed by the lens as image data; and detecting the detection unit comprising one or more pixels in the image data. Contour value calculating means for calculating the sum of the pixel values of the unit and the detection unit around the detection unit; and summing the sum of the pixel values calculated for the detection unit for a plurality of detection units. A contour value summing means; and a focusing means for moving a lens by a lens moving means to a position where the sum calculated by the contour value summing means is larger. Lens focusing device.