JP2006171144A - Auxiliary light device for focus detection of camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hybrid AF camera, which has a plurality of focus detection (AF) systems, with an auxiliary light device for focus detection, with the auxiliary light device being capable of effectively emitting light to a subject in any of the AF systems. <P>SOLUTION: The device includes an AF sensor 17 for carrying out phase difference AF, an imaging element 30 for carrying out contrast AF, a lamp 25 for emitting AF auxiliary light, and a CPU 1 for an auxiliary light usage determination means. According to the storage time of the AF sensor 17 during the phase difference AF, the CPU 1 decides whether to turn on the lamp 25 during the contrast AF. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a focus detection auxiliary light device for a camera equipped with hybrid AF that assists in focus detection of a subject image by irradiation when the subject has low brightness or low contrast.

  In recent years, a subject image formed by a photographing optical system is photoelectrically converted into an electric signal using an image sensor such as a CCD or CMOS, and the image signal obtained thereby is recorded on a recording medium or the like. Digital cameras are widely used. Such a digital camera has a so-called contrast detection type focus detection unit that detects a focus state of a subject image based on a difference (contrast) in a high-frequency component amount included in an imaging signal acquired by an imaging device, In general, an automatic focusing (AF) unit which is an automatic focusing adjustment unit configured to automatically adjust the focusing position of the photographing optical system based on the focus detection result by the focus detection unit is used. It has been put into practical use. This is because it is not necessary to provide a dedicated sensor or an optical system for focus detection, and because AF is performed using the image pickup device itself, focusing accuracy is high.

  However, such contrast detection AF means (hereinafter referred to as contrast AF) captures image signals at a plurality of locations while driving the imaging optical system little by little to detect the contrast peak at the focus position. Since the contrast of each part must be compared, it takes time to focus. For this reason, there is a problem that the time lag until photographing increases and a photo opportunity is missed or a moving subject cannot be focused.

  Therefore, for single-lens reflex digital cameras that require continuous shooting performance and moving object tracking performance, phase difference detection AF means (hereinafter referred to as phase difference AF) employed in conventional single-lens reflex type silver salt film cameras are used. ) Is adopted.

  The phase difference AF differs among the light transmitted through the imaging optical system by arranging one or more pairs of image detection sensors such as line sensors on a surface that is substantially equivalent to an imaging surface on which a silver salt film or an image sensor is arranged. Detects the focus state of the subject image based on the distance (phase difference) between the subject images output from the paired image detection sensors by guiding the luminous flux of the part to different image detection sensors. Since it is possible to immediately recognize how far the in-focus position is with respect to the film surface from the direction and amount of displacement of the subject image on the sensor, the photographic optical system is driven once. Since the in-focus position can be obtained, the in-focus time is fast.

  On the other hand, the image pickup element of a digital camera is considerably smaller than the size of a silver salt film, and the density of pixels has been increased, and some of them have millions of pixels. As the density of pixels in the image sensor increases, the pitch between the pixels decreases. For this reason, when a digital camera is configured using an image sensor in which a plurality of pixels are arranged at a higher density than in the past, the permissible circle of confusion is smaller than in the conventional case, and thus high focusing accuracy is required during AF. Is done.

  In order to realize a highly accurate in-focus state by phase difference AF, it is necessary to increase the resolution of the image detection sensor, and the image detection sensor becomes larger and different parts of the light transmitted through the imaging optical system. The secondary imaging lens for guiding the luminous flux of the light to different image detection sensors must also be increased in size, but there is a limit to disposing in the camera, and the size of the image detection sensor and the secondary imaging lens is increased. There is a problem of higher costs. Further, there may be a case where the focus position includes an error due to an attachment error of the image detection sensor. Therefore, there is a limit to the focusing accuracy in phase difference AF, and it is becoming impossible to perform AF with focusing accuracy commensurate with the pixel pitch as the number of pixels of the image sensor increases.

  In view of such a problem of focusing time and focusing accuracy, for example, when selecting a sports mode that requires continuous shooting performance and moving object tracking performance, phase difference AF is used to capture a stationary subject and landscape mode that requires focusing accuracy. The AF method to be used is changed depending on the shooting mode, such as using contrast AF when the macro mode is selected, or the imaging optical system is first focused with coarse resolution using phase difference AF, and then focused by contrast AF. So-called hybrid AF has been proposed in which fine adjustment of the operation is performed.

However, the hybrid AF is not universal, and when the brightness or contrast of the subject is low, the focus detection capability is lowered and the focus cannot be achieved. Therefore, a camera with auxiliary light means (hereinafter referred to as auxiliary light) that assists focus detection by increasing the luminance and contrast of the subject by irradiating the subject with auxiliary light in the case of low brightness and low contrast is proposed. Has been. For example, Japanese Laid-Open Patent Publication No. 10-056772 proposes auxiliary light in hybrid AF that uses phase difference AF for silver film photography and contrast AF for video photography.
JP-A-10-056772

  However, in general, in a camera having only phase difference AF or contrast AF, whether to use auxiliary light is determined by irradiating auxiliary light again when focusing cannot be performed by first performing phase difference AF or contrast AF. Since the phase difference AF or the contrast AF is performed, when the hybrid AF is simply combined with the sequence, it takes time to focus and the effect of the hybrid AF is lost.

  In JP-A-10-056772, if auxiliary light is used during video shooting, shadows of auxiliary light appear on the recording screen. To prevent this, video shooting or simultaneous video and silver salt film shooting is performed. That is, the use of auxiliary light is prohibited during contrast AF. In this case, in order to solve the problem of the focusing time and the focusing accuracy, it is impossible to take a picture at the time of low luminance or low contrast as a hybrid AF of phase difference AF and contrast AF.

  Therefore, an object of the present invention is to provide an auxiliary light device for focus detection of a camera that can irradiate a subject effectively in any AF method in a camera equipped with hybrid AF.

  In order to achieve the above object, the first aspect of the present invention provides a first focus detection unit using a phase difference detection method for detecting a focus state of a subject image, and a second focus detection method using a contrast detection method. The auxiliary light means for assisting focus detection by irradiating the subject with light, and the auxiliary light when the second focus detection means is used according to the accumulation time of the first focus detection means. And auxiliary light usage determining means for determining whether or not to use the means. According to this configuration, it is possible to realize a camera focus detection auxiliary light device that can effectively irradiate a subject in any AF method in a camera equipped with hybrid AF.

  In the invention of claim 2, in order to detect the focus state of the subject image, first focus detection is performed by the first focus detection means using the phase difference detection method, and then the second focus using the contrast detection method. Two focus detection means for performing focus detection by the detection means, auxiliary light means for assisting focus detection by irradiating the subject with light, and the second focus according to the accumulation time of the first focus detection means An auxiliary light use determining means for determining whether or not to use the auxiliary light means when the focus detecting means is used. The auxiliary light means is used at the time of focus detection by the first focus detecting means. In this case, the auxiliary light means is used at the time of focus detection by the second focus detection means. According to this configuration, it is possible to realize a camera focus detection auxiliary light device that can effectively irradiate a subject in any AF method in a camera equipped with hybrid AF.

  According to a third aspect of the present invention, a first focus detection unit using a phase difference detection method for detecting a focus state of a subject image, a second focus detection unit using a contrast detection method, The second focus detection according to the auxiliary light means for irradiating and assisting focus detection, the accumulation time of the first focus detection means, and the subject distance information obtained from the first focus detection means And auxiliary light use determining means for determining whether or not to use the auxiliary light means when using the means. According to this configuration, it is possible to realize a camera focus detection auxiliary light device that can effectively irradiate a subject in any AF method in a camera equipped with hybrid AF.

  In the invention of claim 4, in order to detect the focus state of the subject image, first focus detection is performed by the first focus detection means using the phase difference detection method, and subsequently the second focus using the contrast detection method. Two focus detection means for performing focus detection by the detection means, auxiliary light means for assisting focus detection by irradiating the subject with light, accumulation time of the first focus detection means, and the first focus An auxiliary light use determining unit that determines whether to use the auxiliary light unit when the second focus detection unit is used according to subject distance information obtained from the detecting unit. When the auxiliary light means is used at the time of focus detection by one focus detection means, the auxiliary light means is used at the time of focus detection by the second focus detection means. According to this configuration, it is possible to realize a camera focus detection auxiliary light device that can effectively irradiate a subject in any AF method in a camera equipped with hybrid AF.

  The invention according to claim 5 is characterized in that, when the subject distance information is farther than a predetermined distance, the use of the auxiliary light means is prohibited when the focus detection means of the contrast detection method is used. According to this configuration, the auxiliary light device for detecting the focus of the camera according to claims 3 and 4 can be realized.

  As described above, according to the first aspect of the present invention, in the camera equipped with the hybrid AF, whether or not the auxiliary light means is used when the second focus detection means is used according to the accumulation time of the first focus detection means. By providing the auxiliary light use determining means for performing the determination, it is possible to realize a camera focus detection auxiliary light device that can effectively irradiate the subject in any AF method.

  According to a second aspect of the present invention, there is provided a hybrid AF camera in which focus detection is first performed by a first focus detection unit using a phase difference detection method, and subsequently focus detection is performed by a second focus detection unit using a contrast detection method. When the auxiliary light means is used at the time of focus detection by the first focus detection means, it is effective for any AF method by using the auxiliary light means at the time of focus detection by the second focus detection means. In addition, an auxiliary light device for focus detection of a camera that can irradiate a subject can be realized.

  According to a third aspect of the present invention, in a camera equipped with hybrid AF, when the second focus detection means is used according to the accumulation time of the first focus detection means and subject distance information obtained from the first focus detection means. By providing auxiliary light use determining means for determining whether to use auxiliary light means, it is possible to realize an auxiliary light device for focus detection of a camera that can effectively irradiate a subject in any AF method.

  The invention of claim 4 uses the auxiliary light means when using the second focus detection means according to the accumulation time of the first focus detection means and the subject distance information obtained from the first focus detection means. In the hybrid AF camera including the auxiliary light use determining unit for determining whether or not, when the auxiliary light unit is used at the time of focus detection by the first focus detection unit, at the time of focus detection by the second focus detection unit By using the auxiliary light means, it is possible to realize a camera focus detection auxiliary light device that can effectively irradiate a subject in any AF method.

  According to a fifth aspect of the present invention, when the subject distance information is farther than a predetermined distance, the use of the auxiliary light unit is prohibited when the focus detection unit of the contrast detection method is used. A focus detection auxiliary light device can be realized.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the digital camera according to the first embodiment. In FIG. 1, 1 is a CPU that controls the camera unit and the entire camera, 2 is a memory controller that performs various controls of image data, and 3 is an EEPROM that stores setting / adjustment data for performing various controls. It is.

  Reference numeral 10 denotes a lens barrel, 11 a zoom lens for adjusting a photographing magnification, 12 an aperture for adjusting the amount of light, and 13 a shutter for adjusting a time for which an image sensor 30 described later receives the amount of light that has passed through the aperture 12. , 14 are focus lenses for adjusting the focus.

  15 is a main mirror and 16 is a sub-mirror, both of which are constituted by half mirrors to divide the optical path. Reference numeral 17 denotes an AF sensor that receives an optical image reflected by the main mirror 15 and transmitted through the sub-mirror 16 and performs focus detection by a phase difference detection method. Reference numeral 18 receives an optical image reflected by the main mirror 15 and reflected by the sub-mirror 16. This is an AE sensor that measures the subject brightness.

  Reference numeral 20 denotes a zoom drive circuit that drives the zoom lens 11, reference numeral 21 denotes an aperture drive circuit that drives the diaphragm 12, reference numeral 22 denotes a shutter drive circuit that drives the shutter 13, reference numeral 23 denotes a focus drive circuit that drives the focus lens 14, and reference numeral 24 denotes a subject. A built-in strobe for emitting strobe light, 25 is a lamp for irradiating the subject with auxiliary light in the case of low brightness and low contrast, and 26 is inserted in front of the lamp 25 so that the light emitted from the lamp 25 is vertically or An irradiation pattern 27 for making the pattern light in the horizontal direction is an irradiation pattern driving circuit 27 for putting the irradiation pattern 26 in and out of the front surface of the lamp 25.

  Reference numeral 30 denotes an image sensor that converts an optical image transmitted through the lens barrel 10 and the main mirror 15 into an electrical signal, and 31 denotes a CDS (correlated double sampling) that samples and holds an image signal output from the image sensor 30 and performs automatic gain adjustment. / AGC (automatic gain adjustment) circuit, 32 is an A / D converter that converts the analog output of the CDS / AGC circuit 31 into a digital signal, 33 is a TG (timing generation) circuit, and a drive signal, CDS / A sample hold signal is supplied to the AGC circuit 31 and a sample clock signal is supplied to the A / D converter 32.

  Here, the memory controller 2 receives an image signal output from the image sensor 30 via the CDS / AGC circuit 31 and the A / D converter 32, and performs focus detection of the subject image by a contrast detection method.

  Reference numeral 34 denotes an SDRAM for temporarily recording image data and the like digitally converted by the A / D converter 32. Reference numeral 35 denotes Y / C (luminance signal / color difference signal) separation, white balance correction, γ correction, and the like. An image processing circuit 36 performs image compression / decompression circuit that compresses image data according to a format such as JPEG and decompresses the compressed image data.

  Reference numeral 37 denotes a D / A converter that converts image data into an analog signal, and reference numeral 38 denotes an LDC that displays the image data.

  Reference numeral 40 denotes an I / F (interface) with a later-described medium 42, reference numeral 41 denotes a slot for connection to the later-described medium 42, and reference numeral 42 denotes a medium for recording image data.

  Reference numeral 50 denotes an accessory attached to the camera, an accessory shoe having an I / F with the accessory, 51 an external strobe that can be attached to the accessory shoe 50, 52 a strobe light emitting unit provided in the external strobe, and 53 provided in the external strobe This is an infrared LED that irradiates a subject with infrared light in the case of low brightness and low contrast.

  Reference numeral 60 denotes an operation SW such as various buttons and dials for operating the camera, and 61 denotes a DC / DC converter that converts the voltage of the power source 62 into a voltage necessary for each circuit.

  Next, the operation of the camera will be described with reference to FIG. FIG. 2 is a flowchart showing the focus detection operation of the camera.

  In S <b> 1, the CPU 1 initializes an auxiliary light flag for determining whether to use auxiliary light, sets N (does not use auxiliary light) for the flag, and stores it in the EEPROM 3.

  In S2, the CPU 1 determines whether or not the auxiliary light is to be used by the auxiliary light flag. If the auxiliary light flag is N, the process proceeds to S3, and if Y, the process proceeds to S12. Immediately after starting the focus detection, since the auxiliary light flag is set to N in S1, the process proceeds to S3.

  In S3, first, in order to perform the first stage focusing by the phase difference AF, the AF sensor 17 is reset and preparations for starting the accumulation of the AF sensor 17 are made.

  In S4, the CPU 1 starts counting the accumulation timer in which the longest accumulation time of the AF sensor 17 is set.

  In S5, accumulation of the AF sensor 17 is started.

  In S6, the CPU 1 starts measuring the accumulation time.

  In S7, the CPU 1 determines whether or not the accumulation timer has reached the set maximum time, and if not completed, the process proceeds to S8, and if completed, the process proceeds to S10.

  In S8, the CPU 1 determines whether or not the accumulation has reached a predetermined reference level. If it has reached, the process proceeds to S9. If not, the process proceeds to S7, and the accumulation timer ends or the accumulation reaches a predetermined reference level. Repeat until it reaches.

  In S9, the measurement of the accumulation time is finished.

  In S10, the measurement of the accumulation time is finished.

  In S11, the CPU 1 determines that the auxiliary light should be used in response to the fact that the predetermined reference level has not been reached even after the longest time for which accumulation has been set, and determines that auxiliary light should be used. Is stored in the EEPROM 3, and the process proceeds to S2. In this case, the determination in S2 is Y and the process proceeds to S12.

  In S12, in order to perform phase difference AF using the auxiliary light, the lamp 25 is turned on and the subject is irradiated with the auxiliary light by the lamp light.

  In S13, the AF sensor 17 is reset and preparations for starting the accumulation of the AF sensor 17 are made.

  In S14, the CPU 1 starts counting the accumulation timer in which the longest accumulation time of the AF sensor 17 is set.

  In S15, accumulation of the AF sensor 17 when the lamp 25 is lit is started.

  In S16, the CPU 1 determines whether or not the accumulation timer has reached the set maximum time, and if it has not been completed, the process proceeds to S17, and if it has been completed, the process proceeds to S19.

  In S17, the CPU 1 determines whether or not the accumulation has reached a predetermined reference level. If it has reached, the process proceeds to S18. If not, the process proceeds to S16, and the accumulation timer ends or the accumulation reaches a predetermined reference level. Repeat until it reaches.

  In S18, the lamp 25 is turned off.

  In S19, the lamp 25 is turned off.

  In S20, the CPU 1 determines that focusing cannot be performed because the accumulation does not reach a predetermined reference level even though the auxiliary light has been irradiated, and the fact that focusing cannot be performed is displayed on the LCD 38 or a finder (not shown).

  In S21, the accumulation timer count ends.

  In S22, the CPU 1 reads data accumulated from the AF sensor 17 and calculates a correlation amount based on the data.

  In S23, the defocus amount of the focus lens 14 is calculated based on the calculated correlation amount, optical data such as the focal length of the zoom lens 11, the sensitivity of the focus lens 14, and the like.

  In S24, the focus lens 14 is driven by the focus drive circuit 23 based on the calculated defocus amount. As a result, the first-stage focusing by the phase difference AF is completed.

  In S25, it is determined whether or not auxiliary light is to be used when performing the second-stage focusing operation by contrast AF. First, the CPU 1 determines whether or not auxiliary light was used during phase difference AF using the auxiliary light flag. If the auxiliary light flag is N, the process proceeds to S26, and if Y, the process proceeds to S32.

  Next, in S26, secondly, it is determined whether or not the accumulation time of the AF sensor 17 measured during the phase difference AF is shorter than the set predetermined time (threshold value). Proceed to S32.

  In S27, the focus lens 14 is finely driven by the focus drive circuit 23 in order to perform contrast AF.

  In S <b> 28, the memory controller 2 reads the image signal of the image sensor 30 at the position where the focus lens 14 is finely driven and records it in the SDRAM 34.

  In S29, the memory controller 2 determines whether or not the in-focus peak position can be detected by contrast detection from a plurality of image signals corresponding to a plurality of positions of the focus lens 14, and if it can be detected, the process proceeds to S30. Then, the focus lens 14 is finely driven and the image signal is read at that position until the in-focus peak position can be detected. Since at least three image signals are required to detect the in-focus peak position, the routine from S27 to S29 is performed three times or more.

  In S30, the defocus amount of the focus lens 14 is calculated based on optical data such as the focus peak position detected by the CPU 1, the focal length of the zoom lens 11, and the sensitivity of the focus lens 14.

  In S31, the focus lens 14 is driven by the focus drive circuit 23 based on the calculated defocus amount. As a result, the second-stage focusing by contrast AF is completed.

  In S32, when the auxiliary light flag is Y in S25 and when the accumulation time is longer than a predetermined time in S26, the lamp 25 is turned on to perform contrast AF using auxiliary light, and the subject is illuminated with the lamp light. Irradiate auxiliary light.

  In S33, the focus lens 14 is finely driven by the focus drive circuit 23 in order to perform contrast AF.

  In S <b> 34, the memory controller 2 reads the image signal of the image sensor 30 at the position where the focus lens 14 is finely driven and records it in the SDRAM 34.

  In S35, the memory controller 2 determines whether or not the in-focus peak position can be detected by contrast detection from a plurality of image signals corresponding to a plurality of positions of the focus lens 14, and if it can be detected, the process proceeds to S30. Then, the focus lens 14 is finely driven and the image signal is read at that position until the in-focus peak position can be detected. Since at least three image signals are required to detect the in-focus peak position, the routine from S27 to S29 is performed three times or more.

  In S 36, the defocus amount of the focus lens 14 is calculated based on optical data such as the focus peak position detected by the CPU 1, the focal length of the zoom lens 11, and the sensitivity of the focus lens 14.

  In S37, the focus lens 14 is driven by the focus drive circuit 23 based on the calculated defocus amount. As a result, the second-stage focusing by contrast AF is completed.

  In S38, the lamp 25 is turned off.

  In S39, the completion of focusing is displayed on the LCD 38 or a finder (not shown), and the focus detection operation is terminated.

  As described above, according to the present embodiment, in the hybrid AF camera including the two AF methods of the phase difference AF and the contrast AF in order to solve the problem of the focusing time and the focusing accuracy, By determining whether or not auxiliary light at the time of contrast AF is used according to the accumulation time, it is possible to realize an auxiliary light device for focus detection of a camera that can effectively irradiate a subject in any AF method.

  In addition, when auxiliary light is used during phase difference AF, an auxiliary light device for focus detection of a camera that can effectively irradiate a subject in any AF method can be realized by using auxiliary light also during contrast AF. .

  In the above description, the auxiliary light is provided by the lamp light from the lamp 25, but the built-in strobe 24 or the strobe light of the external strobe 51 or other methods may be used.

  Further, although the auxiliary light use determining means is performed by the CPU 1, it may be performed by a dedicated IC or other means.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. The block diagram showing the configuration of the digital camera is the same as that of the first embodiment in FIG.

  Next, the operation of the camera will be described with reference to FIG. FIG. 3 is a flowchart showing the focus detection operation of the camera.

  In S51, the CPU 1 initializes an auxiliary light flag indicating whether or not auxiliary light is used, sets N (not using auxiliary light) to the flag, and stores it in the EEPROM 3.

  In S52, the CPU 1 determines whether or not the auxiliary light is used by the auxiliary light flag. If the auxiliary light flag is N, the process proceeds to S53, and if Y, the process proceeds to S62. Immediately after the focus detection is started, since the auxiliary light flag is set to N in S51, the process proceeds to S53.

  In S53, first, in order to perform first-stage focusing by phase difference AF, the AF sensor 17 is reset and preparations for starting accumulation of the AF sensor 17 are made.

  In S54, the CPU 1 starts counting the accumulation timer in which the longest accumulation time of the AF sensor 17 is set.

  In S55, accumulation of the AF sensor 17 is started.

  In S56, the CPU 1 starts measuring the accumulation time.

  In S57, the CPU 1 determines whether or not the accumulation timer has reached the set maximum time, and if not completed, the process proceeds to S58. If completed, the process proceeds to S60.

  In S58, the CPU 1 determines whether or not the accumulation has reached a predetermined reference level. If it has reached, the process proceeds to S59. If not, the process proceeds to S57, and the accumulation timer ends or the accumulation reaches a predetermined reference level. Repeat until it reaches.

  In S59, the accumulation time measurement ends.

  In S60, the measurement of the accumulation time is finished.

  In S61, in response to the fact that the CPU 1 has not reached the predetermined reference level even after the longest time for which accumulation has been set, it is determined that the auxiliary light should be used, and the auxiliary light flag is set to Y (use auxiliary light). Is stored in the EEPROM 3, and the process proceeds to S52. In this case, the determination in S52 is Y, and the process proceeds to S62.

  In S62, in order to perform phase difference AF using the auxiliary light, the lamp 25 is turned on and the subject is irradiated with the auxiliary light by the lamp light.

  In S63, the AF sensor 17 is reset and preparations for starting the accumulation of the AF sensor 17 are made.

  In S64, the CPU 1 starts counting the accumulation timer in which the longest accumulation time of the AF sensor 17 is set.

  In S65, accumulation of the AF sensor 17 when the lamp 25 is lit is started.

  In S66, the CPU 1 determines whether or not the accumulation timer has reached the set maximum time, and if not completed, the process proceeds to S67, and if completed, the process proceeds to S69.

  In S67, the CPU 1 determines whether or not the accumulation has reached a predetermined reference level. If it has reached, the process proceeds to S68. If not, the process proceeds to S66, and the accumulation timer ends or the accumulation reaches a predetermined reference level. Repeat until it reaches.

  In S68, the lamp 25 is turned off.

  In S69, the lamp 25 is turned off.

  In S70, the CPU 1 determines that focusing cannot be performed because the accumulation does not reach a predetermined reference level even though the auxiliary light is irradiated, and displays that focusing cannot be performed in the LCD 38 or a finder (not shown).

  In S71, the accumulation timer count ends.

  In S72, the CPU 1 reads the accumulated data from the AF sensor 17 and calculates the correlation amount based on the data.

  In S73, the defocus amount of the focus lens 14 is calculated based on the calculated correlation amount, optical data such as the focal length of the zoom lens 11, the sensitivity of the focus lens 14, and the like.

  In S74, the CPU 1 calculates the distance to the subject to be photographed based on the calculated defocus amount and the absolute position of the focus lens 14.

  In S75, the focus lens 14 is driven by the focus drive circuit 23 based on the calculated defocus amount. As a result, the first-stage focusing by the phase difference AF is completed.

  In S76, it is determined whether or not auxiliary light is to be used when performing the second-stage focusing operation by contrast AF. First of all, it is determined whether or not the distance to the subject to be photographed is closer than a predetermined distance (threshold value) that has been set. If so, the process proceeds to S77, and if far, the process proceeds to S79.

  Next, in S77, secondly, the CPU 1 determines whether or not the auxiliary light was used during the phase difference AF by using the auxiliary light flag. If the auxiliary light flag is N, the process proceeds to S78, and if it is Y, the process proceeds to S88.

  In S78, thirdly, it is determined whether or not the accumulation time of the AF sensor 17 measured at the time of phase difference AF is shorter than a predetermined time (threshold value) set. Proceed to S88.

  In S79, the CPU 1 sets the minute driving range of the focus lens 14 based on the optical data such as the first-stage focusing position by the phase difference AF, the focal length of the zoom lens 11, the sensitivity of the focus lens 14, and the like in the EEPROM 3. Store.

  In S80, the focus driving circuit 23 finely drives the focus lens 14 in order to perform contrast AF.

  In S81, it is determined whether or not the position of the focus lens 14 that is finely driven is within the set driving range. If it is within the range, the process proceeds to S82, and if it is out of the range, the process proceeds to S86.

  In S <b> 82, the memory controller 2 reads the image signal of the image sensor 30 at the position where the focus lens 14 is finely driven and records it in the SDRAM 34.

  In S83, the memory controller 2 determines whether or not the in-focus peak position can be detected by contrast detection from a plurality of image signals corresponding to the plurality of positions of the focus lens 14, and if it can be detected, the process proceeds to S84. Then, the focus lens 14 is finely driven and the image signal is read at that position until the in-focus peak position can be detected. Since at least three image signals are required to detect the focus peak position, the routine from S80 to S83 is performed three or more times.

  In S <b> 84, the defocus amount of the focus lens 14 is calculated based on optical data such as the focus peak position detected by the CPU 1, the focal length of the zoom lens 11, and the sensitivity of the focus lens 14.

  In S85, the focus driving circuit 23 drives the focus lens 14 based on the calculated defocus amount. As a result, the second-stage focusing by contrast AF is completed.

  In S86, the CPU 1 receives the fact that the position of the focus lens 14 is outside the set drive range before the focus peak is detected, and defocuses from that position to the focus position obtained by the phase difference AF. Calculate the quantity.

  In S87, the focus lens 14 is driven by the focus drive circuit 23 based on the calculated defocus amount. In other words, since the first stage of focus is achieved by phase difference AF, the focus position of the second stage by contrast AF should normally be within the drive range, but with contrast AF within the drive range. Since the focus peak cannot be detected, the focus lens 14 is returned to the first stage focus position by the phase difference AF.

  In S88, when the auxiliary light flag is Y in S77 and when the accumulation time is longer than a predetermined time in S78, the lamp 25 is turned on to perform contrast AF using auxiliary light, and the subject is illuminated with the lamp light. Irradiate auxiliary light.

  In S89, the focus lens 14 is finely driven by the focus drive circuit 23 in order to perform contrast AF.

  In S <b> 90, the memory controller 2 reads the image signal of the image sensor 30 at the position where the focus lens 14 is finely driven and records it in the SDRAM 34.

  In S91, the memory controller 2 determines whether or not the in-focus peak position can be detected by contrast detection from a plurality of image signals corresponding to a plurality of positions of the focus lens 14, and if it can be detected, the process proceeds to S92. Then, the focus lens 14 is finely driven and the image signal is read at that position until the in-focus peak position can be detected. Since at least three image signals are required to detect the in-focus peak position, the routine from S89 to S91 is performed three times or more.

  In S <b> 92, the defocus amount of the focus lens 14 is calculated based on optical data such as the focus peak position detected by the CPU 1, the focal length of the zoom lens 11, and the sensitivity of the focus lens 14.

  In S93, the focus lens 14 is driven by the focus drive circuit 23 based on the calculated defocus amount. As a result, the second-stage focusing by contrast AF is completed.

  In S94, the lamp 25 is turned off.

  In S95, the completion of focusing is displayed on the LCD 38 or a finder (not shown), and the focus detection operation is terminated.

  As described above, according to the present embodiment, in the hybrid AF camera including the two AF methods of the phase difference AF and the contrast AF in order to solve the problem of the focusing time and the focusing accuracy, By deciding whether or not to use auxiliary light at the time of contrast AF according to subject distance information obtained from the focus detection result by accumulation time and phase difference AF, it is possible to irradiate the subject effectively for any AF method An auxiliary light device for focus detection of a simple camera can be realized.

  In addition, when auxiliary light is used during phase difference AF, an auxiliary light device for focus detection of a camera that can effectively irradiate a subject in any AF method can be realized by using auxiliary light also during contrast AF. .

  Furthermore, if the subject distance information is farther than the predetermined distance, the use of auxiliary light is prohibited during contrast AF, thereby realizing an auxiliary light device for camera focus detection that can effectively irradiate the subject in any AF method. it can.

  In the above description, the auxiliary light is provided by the lamp light from the lamp 25, but the built-in strobe 24 or the strobe light of the external strobe 51 or other methods may be used.

  Further, although the auxiliary light use determining means is performed by the CPU 1, it may be performed by a dedicated IC or other means.

It is a block diagram which shows the structure of the digital camera based on embodiment of this invention. It is a flowchart which shows the imaging | photography operation | movement of a camera based on the 1st Embodiment of this invention. It is a flowchart which shows the imaging | photography operation | movement of a camera based on the 2nd Embodiment of this invention.

Explanation of symbols

1 CPU
2 Memory controller 3 EEPROM
14 Focus lens 17 AF sensor 23 Focus drive circuit 24 Built-in strobe 25 Lamp 30 Image sensor 51 External strobe

Claims (5)

  A first focus detection unit using a phase difference detection method for detecting a focus state of a subject image, a second focus detection unit using a contrast detection method, and assisting focus detection by irradiating the subject with light. And auxiliary light use determining means for determining whether or not to use the auxiliary light means when using the second focus detecting means according to the accumulation time of the first focus detecting means. And an auxiliary light device for detecting a focus of a camera.   In order to detect the focus state of the subject image, first focus detection is performed by the first focus detection unit using the phase difference detection method, and subsequently focus detection is performed by the second focus detection unit using the contrast detection method. Two focus detection means, an auxiliary light means for assisting focus detection by irradiating light on the subject, and when the second focus detection means is used according to the accumulation time of the first focus detection means When the auxiliary light means is used during focus detection by the first focus detection means in a camera including auxiliary light use determination means for determining whether to use auxiliary light means, the second light An auxiliary light device for detecting a focus of a camera, wherein the auxiliary light means is used at the time of focus detection by the focus detection means.   A first focus detection unit using a phase difference detection method for detecting a focus state of a subject image, a second focus detection unit using a contrast detection method, and assisting focus detection by irradiating the subject with light. The auxiliary light means when the second focus detection means is used according to the auxiliary light means for performing, the accumulation time of the first focus detection means, and the subject distance information obtained from the first focus detection means Auxiliary light use determining means for determining whether to use or not, and an auxiliary light device for detecting a focus of a camera.   In order to detect the focus state of the subject image, first focus detection is performed by the first focus detection unit using the phase difference detection method, and subsequently focus detection is performed by the second focus detection unit using the contrast detection method. Two focus detection means, auxiliary light means for assisting focus detection by irradiating the subject with light, accumulation time of the first focus detection means, and subject distance obtained from the first focus detection means In a camera, comprising: an auxiliary light use determining unit that determines whether to use the auxiliary light unit when the second focus detecting unit is used according to information, the focus by the first focus detecting unit An auxiliary light device for focus detection of a camera, wherein when the auxiliary light means is used at the time of detection, the auxiliary light means is used at the time of focus detection by the second focus detection means.   5. The focus detection auxiliary of the camera according to claim 3, wherein when the subject distance information is longer than a predetermined distance, the use of the auxiliary light means is prohibited when the contrast detection type focus detection means is used. Optical device.

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