JP2013061560A - Distance measuring device, and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distance measuring device and an imaging device that suppress a decrease in measurement accuracy of an object, suppress an increase in power consumption, and reduces the size of the devices.SOLUTION: A distance measuring device 3 includes in a housing 20 a pair of measuring lenses 51a and 51b having a focal distance fa, a pair of measuring lenses 52a and 52b having a focal distance fb, a pair of measuring lenses 53a and 53b having a focal distance fc, and a pair of measuring lenses 54a and 54b having a focal distance fd. Each of a pair of measuring imaging elements 22a and 22b is divided into four imaging areas: 22a into 221a, 222a, 223a, and 224a; and 22b into 221b, 222b, 223b, and 224b.

Description

  The present invention relates to a distance measuring device and an imaging device.

  As an autofocus (AF) method for a digital still camera (hereinafter referred to as “digital camera”) as an image pickup device, a contrast AF method using an image pickup device for shooting or an external distance measurement separately without using an image pickup device for shooting. There is an external AF method using a stereo camera as an apparatus (for example, Patent Document 1).

  In the contrast AF method, the main lens that forms an image on the image sensor for photographing is driven little by little, and the contrast of the image is checked each time to find the image with the highest contrast. The position of the main lens when the contrast of the image is the highest is regarded as being in focus (focused). For this reason, a digital camera equipped with a zoom lens with a high magnification (about 10 times or more) has the disadvantage that the amount of driving the main lens increases during telephoto shooting, which increases the drive time and slows down the AF speed. Yes. If the AF speed is low, a photo opportunity will be missed.

  On the other hand, in the external AF method using a stereo camera, a pair of distance measuring lenses arranged at a predetermined interval apart from an image sensor for photographing, and a subject image obtained through each distance measuring lens is formed. And a pair of planar distance measuring image sensors. The distance to the subject (object to be measured) is obtained by detecting the parallax between the images picked up by the distance measuring image sensors. Therefore, in the external AF method using a stereo camera, the main lens can be moved all at once based on the distance to the subject detected by the stereo camera, instead of moving the main lens little by little. Therefore, a camera equipped with a high-magnification zoom lens has an advantage that the AF speed does not become slow.

  Conventionally, in a digital still camera having an AF function using a stereo camera, a fixed focus lens has been adopted as a distance measuring lens of the stereo camera. On the other hand, a photographing lens that forms an image on a photographing image sensor is a high-power zoom lens and a variable focus lens. In general, when a digital camera uses a high-power zoom lens of 28 mm to 300 mm in terms of 35 mm as a photographing lens, the distance measuring lens of a stereo camera as a distance measuring device is fixed at about 100 mm between 28 mm and 300 mm. A focal lens is used.

However, in this configuration, since the distance measurement range is fixed at an angle of view equivalent to 100 mm, the following problems occur.
FIG. 8 is a diagram showing the angle of view captured by the imaging element for imaging when the focal length of the imaging lens is 28 mm and 300 mm, and the angle of view captured by the imaging element for distance measurement. A in the figure is an angle of view when the focal length of the lens is 28 mm, B in the figure is an angle of view when the focal length of the lens is 300 mm, and C in the figure is an angle of view when the focal length of the lens is 100 mm. An angle, that is, an angle of view captured by the distance measuring image sensor. Reference numeral 100 a denotes a pixel of the distance measuring image sensor 100.

  When the subject is imaged at a focal length of 28 mm of the photographing lens, the angle of view (the photographing range of the photographing image sensor) captured by the photographing image sensor is A in the figure, whereas the distance measuring image sensor. The angle of view captured at 100 is C in the figure. Therefore, at the time of wide-angle shooting of 28 mm, the distance measuring image sensor 100 can only image the center portion of the subject and can measure the distance only near the center of the screen. Therefore, there is a possibility that the subject is in focus only near the center.

  On the other hand, at the time of telephoto shooting where the focal length of the photographic lens is 300 mm, the angle of view captured by the image sensor for shooting is B in the figure, and in this case, all of the subject can be imaged by the image sensor for distance measurement. Can measure the entire screen. However, at the time of telephoto shooting at 300 mm, the pixels used for distance measurement of the captured image by the distance measuring image sensor 100 are only near the center. Thus, since the number of pixels used for distance measurement is greatly reduced, the distance measurement accuracy is lowered, and there is a possibility that the subject is erroneously adjusted with respect to the subject.

  Patent Document 2 describes a distance measuring device including a stereo camera having a wide-angle lens and a stereo camera having a telephoto lens. Thereby, at the time of wide-angle shooting, it is possible to focus on the entire screen by measuring the distance using a stereo camera having a wide-angle lens. In addition, at the time of telephoto shooting, by using a stereo camera having a telephoto lens, the subject can be imaged with the entire distance measuring image sensor, and the pixels used for distance measurement do not decrease. Focus adjustment can be performed correctly on the subject.

  However, in the distance measuring device described in Patent Document 2, a wide-angle stereo camera including a pair of wide-angle lenses and a pair of distance-measuring image sensors for capturing an image transmitted through the wide-angle lens, and Separately, a telephoto stereo camera comprising a pair of telephoto lenses and a pair of distance measuring image sensors for capturing an image transmitted through the telephoto lens is used. Therefore, the size of the distance measuring device becomes large, and when mounted on a digital camera, there is a problem that it is difficult to make the camera compact. In addition, since power is supplied to each of the distance measuring image sensors of each stereo camera, power consumption increases. As a result, when mounted on a digital camera, the battery will be consumed, resulting in a problem that the number of images that can be taken decreases.

  The present invention has been made in view of the above background, and an object of the present invention is to provide a distance measuring device that can suppress an increase in power consumption and reduce the size of the device while suppressing a decrease in distance measuring accuracy of a subject. And providing an imaging device.

  In order to achieve the above object, a first aspect of the present invention provides a pair of a two-dimensional image sensor for distance measurement which is arranged with a predetermined interval and has a plurality of pixels, and an image of a distance measurement object. One distance measuring lens that forms an image on a two-dimensional image sensor for distance, the other lens for distance measurement that forms an image of the object to be measured on the other two-dimensional image sensor for distance measurement, and the distance measuring device A distance measuring device comprising distance calculating means for calculating a distance from the device to a distance measuring object based on an output signal of each distance measuring two-dimensional image sensor when the object is imaged. The two-dimensional imaging device is divided into a plurality of imaging regions, and a plurality of one-side ranging lenses are provided so as to correspond to the divided imaging regions of the one ranging two-dimensional imaging device, and the other side The distance measuring lens corresponds to each of the divided imaging regions of the other distance measuring two-dimensional image sensor. The focal distances of the one distance measuring lenses are made different from each other, the focal distances of the other distance measuring lenses are made different from each other, and the focal distances of the other distance measuring lenses are made plural. The focal length of any one of the one-side distance measuring lenses is the same.

According to the present invention, each two-dimensional imaging device for ranging is divided into a plurality of imaging regions, and side ranging lenses having different focal lengths are divided into each divided imaging region of the two-dimensional imaging device for ranging. It was provided to correspond. Thereby, each two-dimensional image sensor for distance measurement can capture an image formed by the distance measurement lenses having different focal lengths. In addition, since the focal length of each of the other distance measuring lenses is the same as the focal length of any one of the plurality of one side distance measuring lenses, the other distance measuring two-dimensional imaging element and one of the distance measuring lenses are A distance can be measured by parallax calculation by using an image captured in an imaging region formed by a distance measuring lens having the same focal length with a distance two-dimensional image sensor. Thereby, it is possible to perform distance measurement using a pair of image pickup elements and images captured by distance measuring lenses having different focal lengths. As a result, as compared with a distance measuring device described in Patent Document 2, one distance measuring lens pair having the same focal length is provided with one pair of distance measuring two-dimensional imaging elements. The number of distance image sensors can be reduced. If the two-dimensional image sensor for distance measurement having the same size as that of Patent Document 2 is used, the arrangement space for the image sensor for distance measurement can be reduced as compared with the distance measuring device described in Patent Document 2. Compactness can be achieved. In addition, since power may be supplied to a pair of two-dimensional imaging elements for distance measurement, power consumption can be suppressed compared to Patent Document 2 if a two-dimensional imaging element for distance measurement having the same size as Patent Document 2 is used. Can do. As a result, even if the distance measuring device of the present invention is mounted on a digital camera, the digital camera can be reduced in size, battery consumption can be suppressed, and reduction in the number of images that can be taken can be suppressed.
In the present invention, since the image sensor is divided and used, when the two-dimensional image sensor for distance measurement having the same size as Patent Document 2 is used, the number of pixels used for distance measurement is reduced compared to Patent Document 2. The ranging accuracy is lower than that of Patent Document 2. However, the number of pixels that can be used for distance measurement during telephoto shooting can be increased compared with the case where distance measurement is performed from a wide angle to telephoto with a single distance measuring lens pair. Distance can be measured to near the edge. Therefore, it is possible to perform distance measurement with sufficiently high accuracy from wide-angle imaging to telephoto imaging as compared with the case where distance measurement is performed from wide-angle to telephoto with a single distance measuring lens pair.

1 is a front view showing a digital camera according to an embodiment. The block diagram which shows the outline | summary of the system configuration | structure of the digital camera. (A) is a schematic longitudinal cross-sectional view which shows a distance measuring device. (B) is a top view which shows a pair of image sensor for ranging of a ranging apparatus. FIG. 6C is a diagram showing that each distance measuring image sensor of the distance measuring device is divided into four image capturing areas. FIG. 6D is a plan view showing four pairs of distance measuring lenses corresponding to four image pickup areas of the distance measuring image pickup device of the distance measuring apparatus. Schematic for demonstrating the ranging principle by a ranging apparatus. The top view which shows the some image pick-up element formed on the semiconductor wafer. The schematic longitudinal cross-sectional view which shows the conventional ranging apparatus. The operation | movement flowchart when taking a picture with a digital camera. The figure which showed the angle of view imaged with the imaging element for imaging | photography at the focal distances of 28 mm and 300 mm of a lens, and the angle of view imaged with the imaging element for ranging.

Hereinafter, the present invention will be described based on the illustrated embodiments.
FIG. 1 is a front view showing a digital camera as an example of an imaging apparatus including a distance measuring device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing an outline of a system configuration of the digital camera shown in FIG. It is.

(Appearance structure of digital camera)
As shown in FIG. 1, on the front (front) side of the digital camera 1 according to the present embodiment, a photographing lens 2 having an optical high magnification zoom function, a lens array 4 on the front side of the distance measuring device 3 and the like are arranged. ing. On the surface of the lens array 4, a plurality of distance measuring lenses 51a, 52a, 53a, 54a, 51b, 52b, 53b, and 54b are formed integrally with each other at predetermined intervals. When ranging, 51a and 51b, 52a and 52b, 53a and 53b, and 54a and 54b are paired to measure the distance as a total of four stereo cameras (details of the ranging device 3 will be described later).

(System configuration of digital camera 1)
As shown in FIG. 2, the digital camera 1 includes a photographing lens 2 having a plurality of lens groups, a diaphragm unit 10 having a shutter function, and a photographing image for photographing a subject image formed on a light receiving surface through the photographing lens 2. A CMOS image sensor 11 as an element is provided. In addition, a signal processing unit 12 serving as an image generation unit that digitally processes and outputs a pixel output signal (electric signal) output from the CMOS image sensor 11 and converts it into image data that can be displayed or recorded is provided. The entire digital camera 1 is based on a control program stored in a ROM (not shown) based on operation input information from an operation unit 13 including a release button 6, a shooting mode switching button 7 (see FIG. 1), and the like. The control part 14 which performs system control of this is provided. In addition, a liquid crystal monitor (LCD) 15 that displays image data generated by the signal processing unit 12 is provided. Further, a focus lens driving unit 16 as a focusing unit for driving the focus lens group of the photographing lens 2, a zoom lens driving unit 17 for driving the zoom lens group of the photographing lens 2, and an aperture unit driving unit 18 for driving the diaphragm unit 10. It has. Further, the distance measuring device 3 of the external measurement type for measuring the distance from the device to the subject is also provided. The image data generated by the signal processing unit 12 is recorded on a removable memory card 19.

  FIG. 3A is a schematic longitudinal sectional view showing the distance measuring device 3, and FIG. 3B is a plan view showing a pair of distance measuring imaging elements 22a and 22b of the distance measuring device 3. FIG. 3C is a diagram illustrating that each of the distance measurement imaging elements 22a and 22b of the distance measuring device 3 is divided into four imaging regions. FIG. 3D is a plan view showing the four distance measuring lens pairs corresponding to the four image pickup areas of the distance measuring image pickup device of the distance measuring device 3.

(Configuration of ranging device 3)
As shown in FIGS. 3A and 3B, the distance measuring device 3 according to the present embodiment includes a housing 20 whose front side (upper side in FIG. 3A) is open, and a front side of the housing 20. Further, distance measuring lenses 51a, 52a, 53a, 54a and distance measuring lenses 51b, 52b, 53b, 54b are integrally formed. The lens array 4 made of a transparent resin material in which the distance measuring lenses 51 a, 52 a, 53 a, 54 a and the distance measuring lenses 51 b, 52 b, 53 b, 54 b are integrally formed, and the housing 20 facing the lens array 4 A thin plate-like imaging element substrate 21 for distance measurement disposed on the back side (the lower side in FIG. 3A) and a planar shape (two-dimensional) formed on the imaging element substrate 21 for distance measurement at a predetermined interval A pair of distance measuring image sensors 22a and 22b and a circuit board 23 disposed on the back surface of the image sensor substrate 21 are provided.

  As shown in FIGS. 3C and 3D, the distance measuring image pickup element 22a is arranged to face the distance measuring lenses 51a, 52a, 53a, 54a, and the distance measuring image pickup element 22b is a distance measuring lens. It arrange | positions so that 51b, 52b, 53b, 54b may be opposed. The distance measuring image pickup devices 22a and 22b have the same size, and the light receiving surfaces 22a1 and 22b1 of the distance measuring image pickup devices 22a and 22b have four image pickup regions 221a, 222a, 223a, 224a, 221b, 222b, 223b, and 223b, respectively. It is divided into 224b. The imaging region 221a captures an image formed by the ranging lens 51a, and the imaging region 222a captures an image formed by the ranging lens 52a. Similarly, the imaging regions 223a and 224a project images formed by the ranging lenses 53a and 54a, and the imaging regions 221b, 222b, 223b, and 224b are imaged by the ranging lenses 51b, 52b, 53b, and 54b. The image to be displayed is displayed.

  For example, when a VGA (640 × 480 pixels) size image pickup device is used as the distance measurement image pickup devices 22a and 22b, when divided into four regions, one image pickup region is 320 × 240 pixels. Accordingly, the distance measuring image pickup devices 22a and 22b include a total of eight image pickup regions 221a, 222a, 223a, 224a, 221b, 222b, 223b, and 224b each having 320 × 240 pixels. Actually, when there are light shielding walls that divide four imaging regions, there are pixels that cannot be used by the light shielding walls, and not all 320 × 240 pixels may be used, but in the following description, one imaging region is defined as 320 × 240. It will be described as a pixel.

On the other hand, the distance measuring lenses 51a, 52a, 53a, 54a are lenses having different focal lengths fa, fb, fc, fd. Similarly, the distance measuring lenses 51b, 52b, 53b, and 54b are lenses having different focal lengths fa, fb, fc, and fd. The relationship between the focal lengths of the lenses is as follows.
Focal length of ranging lens 51a = focal length of ranging lens 51b = fa
Focal length of ranging lens 52a = focal length of ranging lens 52b = fb
Focal length of ranging lens 53a = focal length of ranging lens 53b = fc
Focal length of ranging lens 54a = focal length of ranging lens 54b = fd
fa ≦ fb ≦ fc ≦ fd
The base lengths of the four pairs of lenses are all the same D

With such a relationship, it is possible to obtain the distance to the subject by capturing the image output signals of the imaging area 221a and the imaging area 221b and performing parallax calculation. Similarly, the distance to the subject can be obtained by capturing the image output signals of the imaging region 222a and the imaging region 222b, the imaging region 223a and the imaging region 223b, and the imaging region 224a and the imaging region 224b and performing parallax calculation. That is, the distance measuring device 3 according to the present embodiment can measure the distance with four stereo cameras formed with lenses having four different focal lengths (field angles). Thereby, the optimum stereo camera can be selected from the four according to the zoom magnification of the photographing lens 2 and the distance measurement data can be used.

(Ranging principle)
Here, the distance measuring principle of the stereo camera by the distance measuring device 3 will be briefly described.

  As shown in FIG. 4, the subject image a1 obtained through the distance measuring lens 51a and the subject image a2 obtained through the distance measuring lens 51b have the same point on the subject a shifted by a parallax Δ for distance measurement. Images are formed on the surfaces of the imaging regions 221a and 221b of the imaging elements 22a and 22b, respectively, received by a plurality of light receiving elements (pixels), and converted into electrical signals. Here, for the purpose of explaining the principle, explanation of other distance measuring lenses is omitted.

  The parallax is Δ, the distance between the optical axes of the distance measurement lenses 51a and 51b (base line length) is D, the distance between the distance measurement lenses 51a and 51b and the subject 101 is L, and the distance measurement lenses 51a and 51b When the focal length of 51b is fa and L >> fa, the following equation (1) is established.

      L = D · fa / Δ (1)

  Therefore, since D and fa are known, the distance L can be calculated by calculating the parallax Δ.

  Next, the details of the distance measuring imaging elements 22a and 22b of the distance measuring device 3 will be described.

  As shown in FIG. 5, the imaging element substrate 21 and the two ranging imaging elements 22 a and 22 b are two imaging elements arranged on the semiconductor wafer 30 from among a plurality of imaging elements 31 formed by a known semiconductor process. Are cut out together.

  Since the plurality of image pickup devices 31 on the semiconductor wafer 30 are patterned using a mask, the two cut-out distance measurement image pickup devices 22a and 22b are aligned with high accuracy, and the light receiving surface. The pixel matrices 22a1 and 22b1 are parallel. In addition, since the surface of the semiconductor wafer 30 is a flat surface with high accuracy, the normal lines of the two distance measuring imaging elements 22a and 22b are necessarily parallel.

  By using the two distance measuring imaging elements 22a and 22b cut out integrally from the wafer, it is possible to perform imaging without correcting the positional deviation and the angular deviation as compared with the case of adjusting and assembling one by one. Since the regions 221a, 222a, 223a, 224a, 221b, 222b, 223b, and 224b are also arranged with high accuracy, any of the four pairs of stereo cameras can stably measure the distance to the subject with high accuracy.

  Further, since the distance measurement imaging elements 22a and 22b of the distance measuring device 3 used in the present embodiment are used as distance measurement sensors and the image quality is not limited, the CMOS used for subject imaging of the digital camera 1 is used. There is no problem even if it is significantly smaller than the size of the image sensor of the image sensor 11. For this reason, as the distance measuring image pickup devices 22a and 22b of the distance measuring device 3, for example, a small image pickup device of about 1/10 inch used in a camera module of a mobile phone can be used.

  In addition, imaging devices for mobile phone camera modules are already mass-produced, which is advantageous in terms of cost. Among them, an image sensor having a VGA (640 × 480 pixels) size is particularly inexpensive. Therefore, four pairs of stereo cameras are configured by dividing two VGA-size image sensors into four regions. Thereby, a small and inexpensive stereo camera can be obtained without increasing the number of distance measuring image sensors. In this way, the distance measuring device 3 suitable for the high-power zoom digital camera 1 can be obtained without increasing the size and cost.

  Next, the effect of using the distance measuring device 3 constituted by four pairs of stereo cameras will be described. Here, four pairs will be described as an example. However, even if the number of pairs is not four, the effect is more effective than the case of a plurality of pairs.

  Prior to the description of the four pairs of stereo cameras, the case of using a pair of conventional stereo cameras will be described with reference to FIG. In a pair of stereo cameras, two VGA (640 × 480 pixels) distance measurement image sensors are imaged by a pair of lenses and subjected to parallax calculation to measure distance. When a digital camera is equipped with a high-power zoom lens of 28 mm to 300 mm in terms of 35 mm, the stereo camera as a distance measuring device takes one point between 28 mm and 300 mm, for example, a pair of fixed focus of 100 mm A lens will be installed. When block matching is performed using 8 × 6 pixels of the ranging image sensor as one unit, the maximum number of distance measuring points is 6400 (= 80 × 80). When block matching is performed with 4 × 3 pixels as one unit, the maximum number of distance measuring points is 25600 (= 160 × 160).

Table 1 below shows the focal length of the main lens and the number of distance measuring points used for distance measurement at that time.

  As shown in Table 1, when zooming to 300 mm, when block matching is performed with 8 × 6 pixels as one unit, the number of distance measuring points decreases to 711 points (27 × 27: 80 × 100/300 = 27). When block matching is performed with 4 × 3 pixels as one unit, the number of distance measuring points decreases by 2844 points (53 × 53: 160 × 100/300 = 53), and only about 1/10 of the distance measuring points are obtained. It will disappear. That is, when the telephoto zoom of 300 mm is used, there is a possibility that the distance measurement points are reduced to 1/10 or less as compared with the case of 100 mm or less, resulting in a distance measurement error.

  In the case of a wide angle of 28 mm, distance measurement is possible with all the number of distance measurement points (8 × 6: 6400 points, 4 × 3: 25600 points). There is a risk of focusing only on a certain subject.

Next, a case where four pairs of stereo cameras are used as the distance measuring device 3 of the present embodiment will be described. In the case of four pairs of stereo cameras, two VGA (640 × 480 pixels) image sensors 22a and 22b are each divided into four, and each of them is used as a QVGA (320 × 240 pixels) image sensor. Then, the image is imaged and parallax calculation is performed to measure the distance. When a digital camera is equipped with a high-power zoom lens of 28 mm to 300 mm in terms of 35 mm, the stereo camera as a distance measuring device has four points between 28 mm and 300 mm, for example, angles of view of 30 mm, 60 mm, 120 mm, and 240 mm. It is assumed that four lenses having focal lengths fa, fb, fc, and fd having a considerable angle of view are mounted (see Table 2).

  In the present embodiment, as described above, imaging is performed using a 320 × 240 pixel imaging device obtained by dividing a VGA (640 × 480 pixel) imaging device into four. When parallax calculation is performed by performing block matching with 4 × 3 pixels as one unit, the number of distance measuring points is 6400 points (= 80 × 80) by dividing 320 × 240 pixels by 4 × 3 pixels.

Table 3 below shows the focal length of the main lens and the number of distance measuring points used for distance measurement at that time.

  When the stereo camera unit 1 using lenses equivalent to 30 mm (51a and 51b) covers the optical zoom of the digital camera from 28 mm to 60 mm, the number of distance measuring points ranges from 6400 at 28 mm to 1600 at 40 mm (40 × 40). : 80 × 30/60 = 40), and the number of distance measuring points becomes 1/4 (= 1600/6400). Therefore, from 35 mm to 60 mm, by using lenses (52a, 52b) equivalent to 60 mm, it is possible to secure a distance measuring point of 6400 points. In addition, when the lens (52a, 52b) corresponding to 60 mm is used when the distance is 35 to 60 mm, the distance near the edge of the screen cannot be measured, but compared with a conventional distance measuring device using only a lens corresponding to 100 mm. For example, the range that cannot be measured is small. Therefore, compared with a conventional distance measuring device using only a lens equivalent to 100 mm, it is possible to reduce the range where there is a risk of being out of focus, and to obtain an almost entirely focused image even at a wide angle. it can. Which lens should be used for distance measurement between 30 mm and 60 mm may be determined as appropriate in consideration of the decrease in the number of distance measurement points and the range where the image cannot be measured. For example, when the focal length of the photographic lens 2 is about 30 mm, the range in which the distance cannot be measured is large when a 60 mm lens is used. On the other hand, when a 30 mm lens is used, the number of distance measuring points is not decreased and the entire screen can be measured. Therefore, for example, ranging from 30 mm to 35 mm may be performed using a 30 mm lens, and ranging from 35 mm to 60 mm may be performed using a 60 mm lens.

  Similarly, when the zoom of the digital camera is covered from 60 mm to 120 mm by the stereo camera unit 2 using the lenses (52a and 52b) equivalent to 60 mm, the number of distance measuring points is from 6400 at 60 mm to 1600 at 40 mm (40 × 40: 80 × 60/120 = 40), and the number of distance measuring points becomes 1/4 (= 1600/6400). Therefore, ranging from 60 mm to 120 mm can be performed with a distance measuring point of 6400 by measuring with a 120 mm lens. Further, in this case, when the focal length of the taking lens 2 is 75 mm, the distance measuring points are 4096 points (64 × 64: 80 × 60/75 = 64), and 4000 points or more can be secured. (52a, 52b) is used to measure the entire screen, and from 75 mm to 120 mm, the distance is measured using a 120 mm lens (53a, 53b), and the distance is measured at 6400 distance measuring points. Good. As a result, the distance measurement point does not fall below 4000, and accurate distance measurement can be maintained.

  Also, as shown in Table 3, when the zoom of the digital camera is covered from 120 mm to 240 mm by the stereo camera unit 3 using lenses equivalent to 120 mm (53a and 53b), the number of distance measuring points is from 6400 to 240 mm at 120 mm. It decreases to 1600 points of time (40 × 40: 80 × 120/240 = 40), and the number of distance measuring points becomes 1/4 (= 1600/6400). Therefore, ranging from 120 mm to 240 mm can be performed with the number of distance measuring points of 6400 by measuring with the 240 mm lens (54a, 54b). Further, when the focal length of the photographic lens 2 is up to 150 mm, even if a 120 mm distance measuring lens (53a, 53b) is used, the number of distance measuring points of 4000 points or more can be secured (64 × 64 = 4096 points: 80 × 120/150). = 64). Therefore, until the focal length of the photographic lens is up to 150 mm, it is possible to measure the distance on the entire screen while maintaining the accuracy of the distance measurement by measuring with the distance measuring lenses (53a, 53b) equivalent to 120 mm. Further, when the focal length of the taking lens 2 exceeds 150 mm, the number of distance measuring points is less than 4000. When the focal length of the taking lens 2 exceeds 150 mm, the distance is measured by a distance measuring lens (54a, 54b) equivalent to 240 mm. Measure at the focus point.

  The zoom of the digital camera is covered from 240 mm to 300 mm by the stereo camera unit 4 using lenses (54a and 54b) equivalent to 240 mm. In the case of 300 mm, the number is reduced to 4096 points (64 × 64: 80 × 240/300 = 64), and the number of distance measuring points is about 1 / 1.6 (= 4096/6400), and the distance measuring points are secured 4000 or more. it can. Therefore, as shown in Table 1, distance measurement is performed with a number of pixels sufficiently larger than the number of distance measurement points at 300 mm (2844 points) as compared with a lens having only a 100 mm lens corresponding to the focal length of the photographing lens. Can do. Accordingly, accurate distance measurement can be performed even at a telephoto distance of 300 mm, and high-precision focusing (focusing) can be performed even during telephoto shooting.

Table 4 shows an example of the relationship between the focal length L of the photographing lens 2 in this embodiment and the lens used for distance measurement.

  Thus, in the present embodiment, it is possible to secure 4000 or more ranging points (4096 × 3 × 4 = 49152 pixels in terms of pixels) even during telephoto shooting where the focal length of the photographing lens 2 is 300 mm. it can. Thus, since a sufficient number of distance measurement points (pixels) can be secured, accurate distance measurement is possible even during telephoto imaging. As a result, it is possible to take a photograph that is not out of focus. Further, when the photographing lens 2 has a focal length of 28 mm, the distance is measured using a distance measuring lens (51a, 51b) equivalent to 35 mm, so that the distance is measured using a distance measuring lens equivalent to 100 mm. The distance can be measured up to the vicinity of the edge of the image. Thereby, compared with the case where distance measurement is performed with a distance measuring lens equivalent to 100 mm, it is possible to focus well to the vicinity of the edge of the image.

  Further, in the present embodiment, by using the distance measuring imaging elements 22a and 22b in four divisions, a pair for each distance measuring lens pair (51a and 51b, 52a and 52b, 53a and 53b, 54a and 54b). The number of distance measuring image sensors can be reduced and the distance measuring device 3 can be reduced in size as compared with the one provided with the distance measuring image sensor. Further, since it is sufficient to supply power to the pair of distance measuring image sensors, an increase in power consumption can be suppressed. Further, if four pairs of 320 × 240 pixel image sensors for distance measurement are used, the same effect as this embodiment can be obtained. In this case, a special image sensor for distance measurement for a distance measuring device is manufactured. Therefore, there arises a problem that the cost of the image sensor for distance measurement increases. On the other hand, as described above, the present embodiment is already mass-produced as an image sensor for a camera module of a mobile phone, and an inexpensive VGA (640 × 480 pixels) size image sensor is divided into 320 × 240 pixels. Since the area is set, the apparatus can be made cheaper than the case where four pairs of 320 × 240 pixel image sensors for ranging are provided.

(Ranging operation)
Next, the distance measuring operation of the distance measuring device 3 when photographing the subject with the digital camera 1 will be described.

FIG. 7 is an operation flowchart when the digital camera 1 takes a picture.
When the photographer turns on a power switch (not shown) (S1) to set the photographing mode (S2), a distance measurement start command signal is output from the control unit 14 to the distance measuring device 3. Next, the zoom magnification is set (S3). When the zoom magnification is set, the distance to the subject is measured by a stereo camera unit equipped with a distance measuring lens corresponding to the set zoom magnification (S4). The subject to be photographed is far away or moves around, or the zoom magnification is changed appropriately according to the subject. When the zoom magnification is changed, the distance is measured again by a stereo camera unit equipped with a distance measuring lens corresponding to the magnification.

  When the distance measurement is completed, the focus lens driving unit 16 as the focusing means is driven based on the obtained distance value, and the position of the lens is adjusted so as to be in focus (S5). After the lens is aligned with the in-focus position, the subject image is formed on the light receiving surface of the CMOS image sensor 11. The pixel output signal output from each pixel of the CMOS image sensor 11 is taken in, and the luminance of the subject is calculated.

  The calculated luminance information of the subject is output to the control unit 14. Then, the control unit 14 adjusts the exposure amount to be appropriate for the subject based on the input luminance information (S6). Specifically, the open state (aperture value) of the aperture unit 10 and the number of electronic shutters of the CMOS image sensor 11 are set. The open state of the aperture unit 10 is controlled by driving the aperture unit drive unit 18.

  When the release button 6 is pressed, the subject is photographed with a focused and appropriate exposure amount (the number of electronic shutters of the CMOS image sensor 11, the aperture value of the aperture unit 10, etc.) (S7). The signal processing unit 12 digitally processes and captures a pixel output signal output from the CMOS image sensor 11 and converts it into image data that can be displayed and recorded. The image data generated by the signal processing unit 12 is stored in the memory card 19 (S8) and displayed as a still image on the liquid crystal monitor (LCD) 15 (S9).

  If the zoom magnification is changed after the power switch is turned on and the shooting mode is set in this way, distance measurement is performed again according to the magnification. At this time, in order to focus as quickly as possible, a stereo camera unit having an optimum focal length (view angle) is selected from the four stereo camera units according to the zoom magnification. For example, when the zoom magnification of the digital camera is changed to be equivalent to 200 mm, as can be seen from Table 4, the position of the lens is adjusted based on the distance value measured by the stereo camera unit 4 using the lenses 54a and 54b. Conversely, only the stereo camera unit 4 needs to calculate the distance value, and the stereo camera units 1, 2, and 3 do not need to calculate the distance value.

  If only the stereo camera unit 4 is used, it is only necessary to perform a parallax calculation on an area of 320 × 240 pixels, so that the calculation amount is ¼ compared with the case of calculating all the pixels (640 × 480 pixels) of the distance measuring image sensor. It becomes. As a result, the calculation time is shortened to ¼, and autofocusing can be performed at high speed.

  If the zoom magnification is recognized in this way, a stereo camera suitable for the zoom magnification can be selected. As a result, by performing the parallax calculation for only the necessary imaging region, the entire screen can be measured without reducing the number of distance measuring points, and the AF speed can be increased.

  In the above, an example in which the distance measuring device 3 of the present embodiment is applied to a digital camera has been described. For example, an imaging device having a zoom function, such as a digital video camera, a vehicle-mounted camera, a mobile device mounted camera, and an FA camera. It can be installed as a distance measuring device that measures the distance to the subject.

What was demonstrated above is an example, and this invention has an effect peculiar to every following (1)-(4) aspect.
(1)
A pair of two-dimensional imaging elements for distance measurement 22a and 22b having a plurality of pixels arranged at a predetermined interval, and an image of a distance measuring object formed on one of the two-dimensional imaging elements for distance measurement 22a A distance measuring lens, a distance measuring lens that forms an image of a distance measuring object on the other distance measuring two-dimensional image sensor, and a two-dimensional distance measuring object when the distance measuring object is imaged. In the distance measuring device including distance calculating means such as the control unit 14 for calculating the distance from the device to the distance measuring object based on the output signals of the image sensors 22a and 22b, each distance measuring two-dimensional imaging element 22a. , 22b is divided into a plurality of imaging areas 221a to 224a, 221b to 224b, and the one-side distance measuring lens corresponds to each of the divided imaging areas 221a to 224a of one distance measuring two-dimensional imaging element 22a. A plurality of lenses for distance measurement on the other side A plurality of the two-dimensional imaging elements 22b for distance measurement are provided so as to correspond to the divided imaging regions 221b to 224b, and the focal distances of the one-side distance measuring lenses 51a to 54a are made different from each other. The focal distances of the side ranging lenses 51b to 54b are made different from each other, and the focal distances of the other ranging lenses 51b to 54b are set to any one of the plurality of one side ranging lenses 51a to 54a. Same as the focal length.
By providing such a configuration, as described in the embodiment, a pair of distance measuring image sensors is provided for each distance measuring lens pair (51a and 51b, 52a and 52b, 53a and 53b, 54a and 54b). In comparison, the number of distance measuring image sensors can be reduced, and the distance measuring device 3 can be downsized. Further, if four pairs of 320 × 240 pixel image sensors for distance measurement are used, the same effect as this embodiment can be obtained. In this case, a special image sensor for distance measurement for a distance measuring device is manufactured. Therefore, there arises a problem that the cost of the image sensor for distance measurement increases. On the other hand, in the aspect described in (1) above, for example, an inexpensive image sensor with a VGA (640 × 480 pixels) size that has already been mass-produced as an image sensor for a camera module of a mobile phone can be used. Therefore, the apparatus can be made cheaper than when four pairs of ranging image sensors are provided.
In addition, even when the telephoto lens 2 has a focal length of 300 mm, it is possible to secure 4000 or more ranging points (4096 × 3 × 4 = 49152 pixels in terms of pixels). Thus, since a sufficient number of distance measurement points (pixels) can be secured, accurate distance measurement is possible even during telephoto imaging. As a result, it is possible to take a photograph that is not out of focus. Further, when the photographing lens 2 has a focal length of 28 mm, the distance is measured using a distance measuring lens (51a, 51b) equivalent to 35 mm, so that the distance is measured using a distance measuring lens equivalent to 100 mm. The distance can be measured up to the vicinity of the edge of the image. Thereby, compared with the case where distance measurement is performed with a distance measuring lens equivalent to 100 mm, it is possible to focus well to the vicinity of the edge of the image.

(2)
In the aspect described in (1) above, the pair of distance measuring two-dimensional imaging elements are imaging elements formed and cut out on the same wafer.
By having such a configuration, as described in the embodiment, each two-dimensional image sensor for distance measurement is used as in the case of the image sensor formed and cut out on a separate wafer for each two-dimensional image sensor for distance measurement. Compared to the case of adjusting and assembling each other, it is possible to suppress positional deviation and angular deviation between the two-dimensional imaging elements for distance measurement. As a result, any of the four pairs of stereo camera units can stably and accurately measure the distance to the subject.

(3)
Further, image data is generated based on a photographing lens 2 having a zoom function, a photographing imaging device such as a CMOS image sensor 11 on which a subject image is formed through the zoom lens, and a signal output from the photographing imaging device. An image generating means such as the signal processing unit 12, a distance measuring means such as a distance measuring device 3 for measuring the distance from the apparatus to the subject, and a focus lens for focusing the subject based on the measurement result of the distance measuring means. In the imaging apparatus such as the digital camera 1 provided with the focusing means such as the drive unit 16, the distance measuring apparatus according to the aspect described in the above (1) or (2) is used as the distance measuring means.
With such a configuration, it is possible to obtain focused image data from wide angle to telephoto. In addition, the digital camera can be reduced in size, battery consumption can be suppressed, and reduction in the number of shootable images can be suppressed.

(4)
Further, in the imaging apparatus such as the digital camera 1 according to the aspect described in (3) above, the two-dimensional imaging element for distance measurement used for calculating the distance from the apparatus to the subject according to the zoom magnification of the photographing lens 2 The imaging area is selected.
By providing such a configuration, as described in the embodiment, since the parallax calculation is performed only for the necessary imaging region, compared to the case of calculating all the pixels (640 × 480 pixels) of the ranging image sensor. This reduces the amount of calculation. As a result, the calculation time is shortened to ¼, and autofocus can be performed at high speed.

1: Digital camera 2: Shooting lens 3: Distance measuring device 4: Lens array 6: Release button 7: Shooting mode switching button 10: Aperture unit 11: Image sensor 12: Signal processing unit 13: Operation unit 14: Control unit 16: Focus lens drive unit 17: Zoom lens drive unit 18: Unit drive unit 19: Memory card 20: Housing 21: Distance image sensor substrate 22a, 22b: Distance image sensor 23: Circuit substrate 30: Semiconductor wafer 31: Imaging elements 51a, 52a, 53a, 54a: ranging lenses 51b, 52b, 53b, 54b: ranging lenses 101: subjects 221a, 222a, 223a, 224a: imaging areas 221b, 222b, 223b, 224b: imaging areas

JP 2002-90616 A JP 2008-286527 A

Claims (4)

A pair of two-dimensional image sensors for ranging, which are arranged at predetermined intervals and have a plurality of pixels;
A one-side ranging lens that forms an image of a ranging object on one ranging two-dimensional image sensor;
A lens for distance measurement on the other side for forming an image of the object for distance measurement on the other two-dimensional image sensor for distance measurement;
A distance measuring device comprising distance calculating means for calculating a distance from the device to the distance measuring object based on an output signal of each distance measuring two-dimensional image sensor when the distance measuring object is imaged.
Dividing each two-dimensional image sensor for distance measurement into a plurality of imaging regions,
A plurality of one-side distance measuring lenses are provided so as to correspond to the divided imaging regions of the one distance-measuring two-dimensional image sensor, and the other distance-measuring lens is provided to the other distance-measuring lens 2. A plurality of dimension imaging elements are provided so as to correspond to the divided imaging areas,
The focal lengths of the respective one-side distance measuring lenses are made different from each other, the focal lengths of the respective other-side distance measuring lenses are made different from each other, and the focal lengths of the respective other side distance-measuring lenses are made different from each other. A distance measuring device having the same focal length as any one of the distance lenses. The distance measuring device according to claim 1.
The pair of distance measuring two-dimensional image sensors are image sensors formed on the same wafer and cut out. A photographic lens having a zoom function;
An imaging device for photographing on which a subject image is formed through the zoom lens;
Image generating means for generating image data based on a signal output from the imaging element for photographing;
Distance measuring means for measuring the distance from the device to the subject;
In an imaging apparatus comprising focusing means for focusing the subject based on the measurement result of the distance measuring means,
An imaging apparatus using the distance measuring device according to claim 1 or 2 as the distance measuring means. The imaging device according to claim 3.
An imaging apparatus, wherein an imaging area of the distance measuring two-dimensional imaging element used for calculating a distance from the apparatus to the subject is determined according to a zoom magnification of the photographing lens.

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