JP2004151183A - Automatic focusing device, digital camera and portable information terminal equipment equipped with the automatic focusing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic focusing device capable of quickly and accurately detecting a focal position. <P>SOLUTION: The automatic focusing device is provided with a CCD 103 for picking up an object image formed on a light receiving surface, a lens system 101 including a focus lens system 101a for forming the object image on the light receiving surface, an external AF sensor 136 for measuring a distance up to the object based on a triangulation and detecting the focal position of the lens system 101, and an IPP 107 for sampling the contrast of the object image formed on the light receiving surface while shifting the focus lens system 101a along the optical axis, and then, detecting the focal position of the lens system 101, and after shifting the focus lens system 101a near the focal position detected by the external AF sensor 136, sampling is performed by the IPP 107 within the extent including the vicinity of the focal position, and then, the final focal position is detected. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an automatic focusing device that automatically detects a focus position, a digital camera having the automatic focusing device, and a portable information terminal device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, automatic focusing in an electronic still camera or the like is performed by a CCD-AF method in which a contrast peak (in-focus position) is detected by a luminance signal accumulated in a CCD while driving a focus lens or a CCD in an optical axis direction, or a triangle. The AF method based on surveying (hereinafter, automatic focusing based on triangulation performed outside the imaging optical system is referred to as “external AF”, whereas the CCD-AF is referred to as “internal AF”) alone is employed. ing.
[0003]
[Problems to be solved by the invention]
However, as shown in FIG. 12, the CCD-AF method drives a focus lens or CCD so that the focus changes from infinity to the closest distance, and finds the peak by finely sampling the contrast. However, there is a problem that it takes time to detect the in-focus position. On the other hand, as shown in FIG. 13, rough sampling is performed from infinity to the nearest point to obtain a rough focus position, and fine sampling is performed near the rough focus position to determine a final focus position. Although a detection method has been proposed, such a method can slightly reduce the time for detecting the in-focus position, but it is still not practically sufficient.
[0004]
In the CCD-AF, when there is a high-luminance subject (light bulb, candle flame, reflected signboard, etc.) in an area to be focused on a shooting (imaging) screen, a contrast peak may be found. There is a possibility that the camera may be in focus without being able to do so, and there is also a possibility that the camera may be incorrectly focused in a dark scene.
[0005]
On the other hand, in external AF based on triangulation, the distance to the subject can be measured at high speed, but parallax occurs on the closest distance side, and the measured distance is likely to be shifted. However, there were problems such as inferiority.
[0006]
Further, when the temperature becomes high or low, the lens portion of the external AF sensor (see FIG. 5) for performing triangulation deforms to change the measurement distance, and the lens barrel deforms to change the focus lens. For example, a change in the focusing point causes deterioration of the focusing accuracy.
[0007]
The present invention has been made in view of the above, and has an automatic focusing device capable of accurately detecting a focus position in a short time, a digital camera having the automatic focusing device, and a portable information terminal device. The challenge is to provide
[0008]
[Means for Solving the Problems]
In order to solve the above-described problem, the invention according to claim 1 includes an imaging unit that captures a subject image formed on a light receiving surface, and a lens system including a focus lens that forms the subject image on the light receiving surface. Measuring a distance to a subject based on triangulation, and determining a focus position of the lens system by first focus position detection means; and moving the focus lens or the imaging means along an optical axis. Second focus position detecting means for sampling the contrast of the subject image formed on the light receiving surface and obtaining the focus position of the lens system, and the focus obtained by the first focus position detecting means. After moving the focus lens to the vicinity of the position, the second focus position detection means performs sampling in a range including the vicinity of the focus position to obtain a focus position, and determines this position as the final position. Wherein the automatic focusing device for detecting as a focus position.
[0009]
According to a second aspect of the present invention, in the automatic focusing apparatus according to the first aspect, a temperature measuring means for measuring a temperature is provided, and a sampling condition of sampling by the second focus position detecting means is the temperature measuring means. Is set according to the temperature measurement result by
[0010]
According to a third aspect of the present invention, in the automatic focusing apparatus according to the first or second aspect, an imaging condition determining unit that determines a focal length or an F value of the lens system or the number of recording pixels of the imaging unit. The sampling condition of the sampling by the second in-focus position detecting means is set according to the judgment result by the imaging condition judging means.
[0011]
According to a fourth aspect of the present invention, in the automatic focusing apparatus according to the second or third aspect, as the sampling condition, a sampling range, a sampling interval, or a sampling start position of sampling by the second focus position detecting unit is used. Alternatively, an area used for the sampling is set on the light receiving surface.
[0012]
According to a fifth aspect of the present invention, there is provided a digital camera having the automatic focusing device according to any one of the first to fourth aspects.
[0013]
According to a sixth aspect of the present invention, there is provided a portable information terminal device having the automatic focusing device according to any one of the first to fourth aspects.
[0014]
According to the present invention, after the focus lens is moved to the vicinity of the focus position obtained by the first focus position detection means, sampling is performed by the second focus position detection means in a range including the vicinity of the focus position. Is performed, the in-focus position is obtained, and this position is finally detected as the in-focus position, so that the in-focus position can be accurately specified in a short time. That is, the distance to the subject is measured at high speed by the first focus position detection means based on triangulation, and the focus position is temporarily grasped. Then, the approximate focus position is obtained by the second focus position detection means. By sampling only in the vicinity of the focus position and determining the focus position with high accuracy, the focus position can be accurately detected in a short time.
[0015]
In particular, according to the second aspect of the present invention, since the sampling condition is set according to the temperature measured by the temperature measuring means, the in-focus position can be detected with high accuracy even in a high or low temperature environment.
[0016]
According to the third aspect of the present invention, the sampling condition is set in accordance with the focal length or the F-number of the lens system or the number of recording pixels of the image pickup means. The specific sampling conditions for this purpose include, as in the invention according to claim 4, a sampling range, a sampling interval or a sampling start position of sampling by the second in-focus position detecting means, or a light receiving position. A region (sampling period) used for sampling on the surface can be exemplified.
[0017]
Further, according to the invention according to claim 5 or claim 6, the effect of the invention according to any one of claims 1 to 4 can be obtained in a digital camera or a portable information terminal.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 is a configuration diagram of a digital camera to which the automatic focusing device according to the present embodiment is applied. In FIG. 1, reference numeral 100 denotes a digital camera. The digital camera 100 includes a lens system 101, a mechanical mechanism 102, a CCD (charge coupled device) 103, a CDS (correlated double sampling) circuit 104, and an AGC amplifier (variable gain amplifier). ) 105, A / D converter 106, IPP (Image Pre-Processor) 107, DCT (Discrete Cosine Transform) 108, Coder (Huffman Encoder / Decoder) 109, MCC (Memory Card Controller) card, DRAM card 110, DRAM 111 , CPU 121, display unit 122, operation unit 123, SG (control signal generation) unit 126, strobe device 127, battery 128, DC-DC converter 129 EEPROM 130, a focus driver 131, a pulse motor 132, a zoom driver 133, a pulse motor 134, motor driver 135, and an external AF sensor 136 and temperature sensor 137.
[0020]
The digital camera 100 has a PC card interface 112 detachably connected to a PC card interface 112. The digital camera 100 (CPU 121) has a recording mode for recording image data obtained by photographing a subject on the PC card 150, and a PC mode. A display mode for displaying images recorded on the card 150 and a monitoring mode for directly displaying captured images on the display unit 122 are provided.
[0021]
The lens system 101 and the mechanical mechanism 102 constitute a lens unit of the digital camera 100. The lens system 101 is composed of, for example, a varifocal lens and has a focus lens system 101a and a zoom lens system 101b. The mechanical mechanism 102 includes a mechanical shutter, an aperture / filter unit, and the like, and the mechanical shutter performs simultaneous exposure of two fields (not shown).
[0022]
The focus driver 131 drives the pulse motor 132 in accordance with a control signal from the CPU 121 to move the focus lens system 101a along the optical axis. The zoom driver 133 drives the pulse motor 134 according to a control signal from the CPU 121, and moves the zoom lens system 101b along the optical axis. The motor driver 135 drives the mechanical mechanism 102 according to a control signal from the CPU 121, and sets, for example, an aperture value. Note that the number of pulses Zp of the pulse motor 134 (18 motor divisions) and the lens extension amount (mm) of the zoom lens system 101b have, for example, a relationship as shown in FIG. 2, and the zoom position is from Wide (wide) to Tele. In the case of (telephoto), the shooting distance (1 / L) and the lens extension amount (mm) of the zoom lens system 101b have a relationship as shown in FIG. 3, for example.
[0023]
The CCD 103 converts an image input through the lens unit into an electric signal (analog image data). The CDS circuit 104 is a circuit for reducing noise in the CCD type imaging device. The AGC amplifier 105 corrects the level of the signal that has been correlated double sampled by the CDS circuit 104. The gain of the AGC amplifier 105 is determined by setting data (control voltage) in the AGC amplifier 105 through a D / A converter built in the CPU 121. The A / D converter 106 converts analog image data from the CCD 103 input from the AGC amplifier 105 into digital image data. That is, based on a control signal transmitted from the SG unit 126 in accordance with an instruction from the CPU 121, the output signal of the CCD 103 passes through the CDS circuit 104, the AGC amplifier 105, and the A / D converter 106, and is output to an optimum sampling frequency (for example, NTSC The signal is converted into a digital signal by an integer multiple of the subcarrier frequency of the signal.
[0024]
The IPP 107, the DCT 108, and the coder 109 are digital signal processing units. The digital image data input from the A / D converter 106 is divided into color differences (Cr, Cb) and luminance (Y) to perform various processes (correction and image compression). / Data processing for decompression etc.). The DCT 108 and the coder 109 perform, for example, orthogonal transformation / inverse orthogonal transformation which is a process of JPEG-compliant image compression / decompression, and Huffman encoding / decoding which is also a process of JPEG-compliant image compression / decompression.
[0025]
The MCC 110 temporarily stores the compressed image and records the image on the PC card 150 via the PC card interface 112, or reads the image from the PC card 150.
[0026]
The CPU 121 uses the DRAM 111 as a work area in accordance with a program stored in the EEPROM 130, and controls various operations of the digital camera 100 in accordance with an instruction from a user via an operation unit 123 or a remote controller (not shown) described later. More specifically, the CPU 121 controls a shooting operation, an automatic exposure (AE) operation, an automatic white balance (AWB) adjustment operation, an AF operation, and the like. The camera power is input from a battery 128 made of NiCd, nickel hydride or lithium battery to the DC-DC converter 129 and supplied to the CPU 121 and other parts of the digital camera 100.
[0027]
The display unit 122 is configured by an LCD, an LED, an EL, or the like, and displays digital image data obtained by photographing, image data obtained by expanding data recorded on the PC card 150, and the like. The operation unit 123 is used by a user to perform a function selection, a shooting instruction, other various settings, and the like, and includes a button, a touch panel, and the like. Specifically, the operation unit 123 includes a release key for giving a shooting instruction, a zoom key for setting a zoom position (Tele to Wide) of the zoom lens system 101b, and the number of recording pixels of the CCD 103 (1800 × 1200, 900 × 600 or 640 × 480). The CPU 121 performs an AF operation or the like when the release key is half-pressed and a sensor not shown (hereinafter, referred to as “sensor RL- 1”) is turned on, and the release key is fully pressed and a sensor not shown in the drawings (hereinafter referred to as “sensor RL- 1”). When “sensor RL-2” is turned on, a photographing operation is executed.
[0028]
The strobe device 127 emits light automatically at the time of photographing or in response to a user's instruction, and adjustment data used when the CPU 121 controls the operation of the digital camera 100 is written in the EEPROM 130. A known sensor is used as the temperature sensor 137, and the measured temperature of the temperature sensor 137 is output to the CPU 121.
[0029]
FIG. 4 shows an example of a specific configuration of the IPP 107. In FIG. 4, the IPP 107 is a color separation unit that separates the digital image data input from the A / D converter 106 into R, G, and B color components. 1071, a signal interpolator 1072 for interpolating the separated R, G, and B image data, a pedestal adjuster 1073 for adjusting the black level of each of the R, G, and B image data, and each of the R, B A white balance adjustment unit 1074 for adjusting the white level of the image data; a digital gain adjustment unit 1075 for correcting each of the R, G, and B image data with the gain set by the CPU 121; and each of the R, G, and B image data A gamma conversion unit 1076 for performing gamma conversion of the image data, a matrix unit 1077 for separating the RGB image data into color difference signals (Cr, Cb) and a luminance signal (Y), and a color difference signal (Cr Create a video signal based on Cb) and the luminance signal (Y), and a video signal processing unit 1078 for outputting to the display unit 122.
[0030]
Further, IPP 107 detects a Y operation unit 1079 for detecting luminance data (Y) of the image data after the pedestal adjustment by pedestal adjustment unit 1073, and passes only a predetermined frequency component of the luminance data (Y) detected by Y operation unit 1079. BPF 1080, an AF evaluation value circuit 1081 that outputs an integrated value of the luminance data (Y) passed through the BPF 1080 to the CPU 121 as an AF evaluation value, and a digital count value corresponding to the luminance data (Y) detected by the Y operation unit 1079. An AE evaluation value circuit 1082 that outputs the luminance data (Y) of the R, G, and B image data adjusted by the white balance adjustment unit 1074 to the CPU 121 as an AE evaluation value. The luminance data (Y) of each color detected by the arithmetic unit 1083 is counted, and the AW of each color is counted. And AWB evaluation value circuit 1084 to output as evaluation value to CPU 121, and includes a CPU interface 1085 is an interface with the CPU 121, and a DCT interface 1086 is an interface with DCT108.
[0031]
The external AF sensor 136 in FIG. 1 measures the distance to the subject in a passive manner, and FIG. 5 shows a schematic configuration thereof. The external AF sensor 136 includes lenses 151a (left) and 151b (right), photosensor arrays 152a (left) and 152b (right), and an arithmetic circuit (not shown). The distance measurement principle of the external AF sensor 136 will be described. The distance to the subject is d, the distance between the lens 151a and the photosensor array 152a, and the distance between the lens 151b and the photosensor array 152b is f, and the photosensor arrays 152a and 152b. Assuming that the widths of the incident light are x1 and x2, respectively, and the distance between the light incident portions of the photosensor arrays 152a and 152b is B, the distance d is calculated by triangulation as d = B · f / (x1 + x2). be able to. FIG. 6 shows the subject images of the left and right photo sensor arrays 152a and 152b. The arithmetic circuit integrates the light amounts of the subject images of the respective photo sensor arrays and calculates the deviation of the data obtained by the left and right sensors. Then, the distance d to the subject is calculated and output to the CPU 121.
[0032]
As described above, the case where the focus position is detected using the external AF sensor 136 is referred to as external AF, and the case where the focus position is detected using the CCD 103 is referred to as CCD-AF (internal AF). In the CCD-AF, the lens of the focus lens system 101a is moved to sample the contrast (AF evaluation value) of the subject according to the image signal output from the CCD 103, and the peak position of the AF evaluation value is set as the focus position. Adopt hill-climbing servo method. The digital camera 100 uses the external AF and the CCD-AF in combination as in the operation example described below. Performing the AF using the external AF and the CCD-AF in this manner is called hybrid AF.
[0033]
Next, an operation example regarding the automatic focusing of the digital camera 100 will be described with reference to FIGS.
[0034]
FIG. 7 is a flowchart illustrating an example of control by the CPU 121. First, the CPU 121 determines whether or not the release key is half-pressed to turn on the sensor RL-1 (step 1 (described as “S1” in FIG. 7; the same applies hereinafter)). If it is determined that the sensor RL-1 has been turned on, a temperature measurement process by the temperature sensor 137 and a distance measurement process by the external AF sensor 137 are executed (steps 2 and 3), and the sensor RL-1 is turned on. If it is determined that there is not, the process returns to step 1 again.
[0035]
Subsequently, the CPU 121 determines the zoom position (focal length) of the zoom lens system 101b, the aperture value (F value) of the lens system 101, the set image quality (number of recording pixels) and the measured temperature (step 4), and executes later. The sampling conditions of the CCD-AF to be performed are set (step 5).
[0036]
Here, the CPU 121 determines the zoom position based on the number of drive pulses of the pulse motor 134 that drives the zoom lens system 101b. The CCD-AF sampling conditions include (1) a sampling range of the AF evaluation value when the CCD-AF is executed (moving range of the focus lens system 101a), and (2) a CCD 103 when the AF evaluation value is sampled. (3) Sampling interval when CCD-AF is executed (movement amount of focus lens system 101b from a certain sampling point to an adjacent sampling point), (4) CCD-AF execution In this case, the CPU 121 sets at least one of the sampling conditions (1) to (4) in step 5 (for conditions that are not set, the sampling start position (movement start position of the focus lens system 101a)). These conditions will be described below.
(1) Sampling range of AF evaluation value when executing CCD-AF
FIG. 8 is a diagram for explaining a sampling range (moving range of the focus lens system 101a) when executing the CCD-AF. In the figure, the horizontal axis indicates the lens position (closest to infinity), the vertical axis indicates the contrast of the subject (AF evaluation value), and the symbol a indicates the sampling range. When the CPU 121 appropriately sets the sampling range (sampling width) according to the focal length, the F value, and the number of recording pixels, it is possible to achieve both the accuracy and speed of focus position detection.
[0037]
For example, in the case of setting Wide, small aperture, or low pixel number that can be accurately handled even by the external AF, the CPU 121 sets the sampling range of the CCD-AF to be narrow to speed up the focus position detection. On the other hand, in the case of a Tele, an open aperture, or a high pixel count setting with insufficient accuracy in the external AF, the CPU 121 sets a wide sampling range of the CCD-AF. Further, when the measurement temperature is high or low temperature (when the temperature does not fall within a predetermined temperature range including room temperature), the accuracy of the external AF deteriorates, the lens barrel is deformed, and the focal point shifts. Set widely.
[0038]
It should be noted that the expansion rate of the sampling range may be increased as the temperature becomes higher or as the temperature becomes lower, so that the in-focus position can be detected with high accuracy even when the temperature change from room temperature is large. Can be done.
{Circle over (2)} The range of the AF area on the light receiving surface of the CCD 103 when sampling the AF evaluation value
FIG. 9 is a diagram for explaining an AF area (an area for acquiring an AF evaluation value) on the light receiving surface of the CCD 103. In the figure, reference numeral 1031 denotes a light receiving surface of the CCD 103, 1032 denotes an AF area, and the CPU 121 appropriately sets the AF area 1032 inside the light receiving surface 1031 according to the focal length, thereby detecting a focus position. It is possible to achieve both accuracy and speed (in FIG. 9, the light receiving surface 1031 is divided into 15 in the horizontal direction and 10 in the vertical direction, for a total of 150 divisions, and the AF area 1032 is an area divided into the 150 divisions). Is set as a unit.)
[0039]
For example, in the case of Wide in which the occupied area of the subject on the shooting screen is considered to be small, the CPU 121 sets the AF area 1032 on the entire light receiving surface 1031 as shown in FIG. Sampling is performed, and the AF evaluation value is sampled at a slow sampling cycle. On the other hand, in the case of Tele in which the occupation area of the subject on the shooting screen is considered to be large, the CPU 121 sets the AF area 1032 in the center of the light receiving surface 1031 as shown in FIG. Only the AF evaluation value is sampled, and the AF evaluation value is sampled at an earlier sampling period. Since the sampling period of the CCD-AF is determined by the image processing time, if the range of the image to be processed is narrowed, sampling can be performed at a correspondingly fast period.
(3) Sampling interval when executing CCD-AF
FIG. 10 is a diagram for explaining the sampling interval of the AF evaluation value with respect to the movement amount of the focus lens system 101a of the CCD-AF. In the figure, the horizontal axis indicates the lens position (closest to infinity), the vertical axis indicates the contrast of the subject (AF evaluation value), and the symbol b indicates the sampling interval of the AF evaluation value. By appropriately setting the sampling interval according to the focal length by the CPU 121, it is possible to achieve both the accuracy and speed of focus position detection.
[0040]
For example, at a focal length with a large depth of focus, the CPU 121 increases the sampling interval of the AF evaluation value by increasing the lens movement interval, reduces the number of sampling points, and speeds up the focus position detection. Also in the case of setting the small aperture and the low number of pixels, the depth of focus becomes deep, so that the CPU 121 similarly aims to speed up the focus position detection.
(4) Sampling start position when executing CCD-AF
Due to the general temperature characteristics of the lens barrel, the focal point of the focus lens system 101a tends to shift to the short distance side when the temperature is high compared to normal temperature (25 ° C.), and shifts to the long distance side when the temperature is low. The CPU 121 shifts the sampling start position so as to cover the accurate focus position at the time of sampling of the CCD-AF (to be included in the sampling range). That is, the CPU 121 determines whether or not the measured temperature is within a predetermined range around room temperature. If the measured temperature is within the predetermined range, the predetermined position is set as the sampling start position. Side, and if the temperature is low outside the predetermined range, the sampling range is shifted to the short distance side. This makes it possible to maintain the accuracy of focus position detection even in a high or low temperature environment, and to speed up the focus position detection because only the sampling start position is changed instead of expanding the sampling range. Is achieved.
[0041]
It should be noted that the shift amount (shift amount) of the sampling start position may be increased as the temperature becomes higher or as the temperature becomes lower. Can be detected with high accuracy.
[0042]
In the following step 6, the CPU 121 calculates the CCD-AF start position (reference position) based on the distance measurement result of the external AF. The start position of the CCD-AF can be obtained, for example, by using the focus position by the external AF as the center of the sampling range. When the condition (4) is set in step 5, the CPU 121 considers the condition. calculate. That is, if the focus position by the external AF is Faf, the sampling range is Fsamp, and the shift amount of the start position due to the temperature is Fshift, the start position Fstart to be obtained is Fstart = Faf−Fsamp / 2 + Fshift.
[0043]
Then, the CPU 121 moves the focus lens system 101a to the start position obtained in the previous step (step 7), and starts the CCD-AF (step 8). The sampling in the CCD-AF is performed by moving the focus lens system 101a near the reference position and acquiring an AF evaluation value under the sampling conditions set in step 5. At this time, the CPU 121 stores the peak of the AF evaluation value every time it is found, and specifies the position stored as the position corresponding to the peak at the stage where the sampling process is completed, as the focus position.
[0044]
When the sampling is completed over the entire sampling range, the CPU 121 determines that the CCD-AF is completed (step 9), and moves the focus lens system 101a to the position specified as the focus position (the stored position). Then, the detection of the focus position is completed (step 10). Thereafter, when the release key is fully depressed and the sensor RL-2 is turned on, the CPU 121 performs a photographing operation, captures image data of the subject, performs predetermined processing, and records it on the PC card 150.
[0045]
FIG. 11 is a diagram for explaining the above operation examples collectively. The vertical axis indicates the contrast (AF evaluation value), and the horizontal axis indicates the lens position (closest to infinity). First, the CPU 121 obtains the approximate focus position by the external AF, and then, based on the sampling conditions (sampling range, sampling interval (number of sampling points), sampling start position, etc.) set near the approximate focus position. Sampling by the CCD-AF method to detect a final focus position.
[0046]
According to the present embodiment, after the focus lens system 101a is moved to the vicinity of the focusing position obtained by the external sensor 136 and the CPU 121, sampling is performed by the IPP 107 and the CPU 121 in a range including the vicinity of the focusing position. Since the in-focus position is determined and this position is finally determined as the in-focus position, the in-focus position can be accurately detected in a short time.
[0047]
In addition, since the sampling conditions are set according to the temperature measured by the temperature sensor 137, the in-focus position can be detected with high accuracy even in a high or low temperature environment, and the lens system 101 (zoom lens system 101b) can be detected. Since the sampling conditions are set according to the focal length, the F-number, or the number of pixels recorded on the CCD 103, it is possible to achieve both high-dimensional focus position detection accuracy and speed. At this time, by setting a sampling range, a sampling interval or a sampling start position, or an AF area 1032 on the light receiving surface 1031 as specific sampling conditions, the accuracy and speed of focus position detection can be balanced very efficiently. It has become possible.
[0048]
Further, since the digital camera 100 according to the present embodiment uses a passive distance measuring sensor as the external AF sensor, it is possible to reduce the size, cost, and simplification of the processing.
[0049]
It should be noted that the present invention is not limited to the above-described embodiment, and can be appropriately modified and executed without changing the gist of the invention. For example, in this embodiment, an example in which the automatic focusing device is applied to a digital camera has been described. However, the present invention is not limited to this, and can be applied to portable information terminal devices such as PDAs and personal computers. It is.
[0050]
【The invention's effect】
As described above, according to the present invention, after the focus lens is moved to the vicinity of the focus position obtained by the first focus position detection means, the focus position is moved by the second focus position detection means. Since the in-focus position is obtained by performing sampling in a range including the vicinity, and this position is finally detected as the in-focus position, the in-focus position can be specified accurately in a short time. That is, the distance to the subject is measured at high speed by the first focus position detection means based on triangulation, and the focus position is temporarily grasped. Then, the approximate focus position is obtained by the second focus position detection means. By sampling only in the vicinity of the focus position and determining the focus position with high accuracy, the focus position can be accurately detected in a short time.
[0051]
In particular, according to the second aspect of the present invention, since the sampling condition is set according to the temperature measured by the temperature measuring means, the in-focus position can be detected with high accuracy even in a high or low temperature environment.
[0052]
According to the third aspect of the present invention, the sampling condition is set in accordance with the focal length or the F-number of the lens system or the number of recording pixels of the image pickup means. The specific sampling conditions for this purpose include, as in the invention according to claim 4, a sampling range, a sampling interval or a sampling start position of sampling by the second in-focus position detecting means, or a light receiving position. A region (sampling period) used for sampling on the surface can be exemplified.
[0053]
Further, according to the invention according to claim 5 or claim 6, the effect of the invention according to any one of claims 1 to 4 can be obtained in a digital camera or a portable information terminal.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a schematic configuration of a digital camera according to an embodiment.
FIG. 2 is a diagram illustrating an example of a relationship between the pulse number Zp of a pulse motor (18 motor divisions) and a lens extension amount (mm) of a zoom lens system;
FIG. 3 is a diagram illustrating an example of a relationship between a shooting distance (1 / L) and a lens extension amount (mm) of a zoom lens system when a zoom position is Wide to Tele.
FIG. 4 is a diagram illustrating an example of a specific configuration of the IPP of FIG. 1;
FIG. 5 is a diagram showing a schematic configuration of the external AF sensor of FIG. 1;
FIG. 6 is a diagram for explaining a principle of distance measurement of an external AF sensor.
FIG. 7 is a flowchart illustrating an operation example regarding AF of the digital camera.
FIG. 8 is a diagram for explaining a sampling range when executing CCD-AF.
FIG. 9 is a diagram for explaining an AF area on a light receiving surface of a CCD.
FIG. 10 is a diagram illustrating a sampling interval of an AF evaluation value with respect to a movement amount of a focus lens system of a CCD-AF.
FIG. 11 is a diagram for explaining the operation example of FIG. 7;
FIG. 12 is an explanatory diagram showing an example of a conventional CCD-AF method.
FIG. 13 is an explanatory diagram showing another example of the conventional CCD-AF method.
[Explanation of symbols]
100 digital camera
101 lens system
101a Focus lens system
101b Zoom lens system
103 CCD (imaging means)
107 IPP
121 CPU
136 External AF sensor
137 Temperature sensor

Claims (6)

Imaging means for imaging a subject image formed on a light receiving surface;
A lens system including a focus lens that forms the subject image on the light receiving surface;
First focus position detection means for measuring a distance to a subject based on triangulation to obtain a focus position of the lens system;
A second focusing position detecting unit that samples a contrast of a subject image formed on the light receiving surface while moving the focusing lens or the imaging unit along an optical axis and obtains a focusing position of the lens system. Prepare,
After moving the focus lens to the vicinity of the focus position obtained by the first focus position detection means, sampling is performed by the second focus position detection means in a range including the vicinity of the focus position. An automatic focusing device for determining a focusing position by using the same, and detecting this position as a final focusing position. Equipped with temperature measuring means for measuring temperature,
2. The automatic focusing apparatus according to claim 1, wherein sampling conditions for sampling by the second focus position detection unit are set according to a temperature measurement result by the temperature measurement unit. 3. An imaging condition determination unit that determines a focal length or an F value of the lens system or the number of recording pixels of the imaging unit,
The automatic focusing device according to claim 1, wherein a sampling condition of sampling by the second focus position detecting unit is set according to a determination result by the imaging condition determining unit. A sampling range, a sampling interval or a sampling start position of sampling by the second focus position detecting means, or an area used for the sampling on the light receiving surface is set as the sampling condition. The automatic focusing device according to claim 2 or 3. A digital camera comprising the automatic focusing device according to claim 1. A portable information terminal device comprising the automatic focusing device according to any one of claims 1 to 4.

Images