JP3931851B2 - Focus detection device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a focus detection apparatus that detects a focus adjustment state of a plurality of focus detection areas.
[0002]
[Prior art]
Conventionally, a focus detection device and a distance detection device using an image sensor are known. The operations in these focus detection devices and distance detection devices are usually performed in the following steps.
A subject image signal is serially output to the microcomputer from the charge storage type image sensor.
[0003]
The subject image signal is AD converted by the AD conversion means built in the microcomputer to become subject image data.
The microcomputer performs arithmetic processing on the subject image data subjected to AD conversion, and calculates the focus state and subject distance.
The charge of the next charge storage type image sensor is set so that the level of the subject image signal is optimal for focus state and distance detection according to the characteristic values (peak value, average value, contrast value) of the subject image data after AD conversion. Control the accumulation time.
[0004]
Repeat the above steps.
[0005]
[Problems to be solved by the invention]
However, in the focus detection device and the distance detection device as described above, in order to control the charge accumulation time of the next charge accumulation type image sensor based on the current subject image data, even when focus detection and distance detection are not performed. In order to improve the responsiveness when focus detection or distance detection is activated, the charge accumulation type image sensor is always operated, the subject image data is taken in, the accumulation time of the charge accumulation type image sensor is controlled, and the subject It was necessary to make the level of the image signal appropriate for focus state and distance detection.
[0006]
After focus detection and distance detection are activated, the charge accumulation type image sensor is operated, the subject image data is captured, the accumulation time of the charge accumulation type image sensor is controlled, and the level of the subject image signal is detected as the focus state and distance detection. If it is set to be appropriate, the loop consisting of the above steps must be repeated several times until the level of the subject image signal becomes appropriate, and the responsiveness of focus detection and distance detection will deteriorate. It is.
[0007]
On the other hand, the microcomputer that performs AD conversion of the subject image signal is used for processing for other purposes (for example, exposure calculation) when focus detection or distance detection is not performed, so even when focus detection or distance detection is not performed. In preparation for the start of focus detection or distance detection, performing AD conversion of all pixel signals from the image sensor and taking in subject image data at all times reduces the processing speed for other processing and increases responsiveness. There was a drawback of being lowered.
[0008]
In addition, there are a plurality of focus detection areas and distance detection areas, and even when focus detection and distance detection are performed only in the area selected from them, they are not selected in parallel with the focus detection or distance detection of the selected area. It is a burden on the microcomputer to perform the above-described operation for capturing the subject image data in the area, and there is a problem that the responsiveness of the focus detection and the distance detection operation deteriorates.
Therefore, the present invention solves the above problem, and when the focus detection and distance detection are not performed, the accumulation time of the charge accumulation type image sensor is controlled so that the level of the subject image signal is appropriate for the focus state and distance detection. Therefore, an object of the present invention is to provide a focus detection device or a distance detection device using a charge storage type image sensor that does not require AD conversion of all subject image signals from the charge storage type sensor.
[0009]
[Means for Solving the Problems]
A focus detection apparatus according to the present invention has a plurality of focus detection areas, and an analog signal and a characteristic value output in accordance with charges accumulated in a charge accumulation type image sensor provided corresponding to each focus detection area. Of the signals, for the selected focus detection area, analog signals and characteristic values are converted into digital signals to determine the focus adjustment state in the selected focus detection area, and the charge accumulation time is controlled and selected. For a focus detection region that has not been selected, only the characteristic value signal is converted into a digital signal to control the charge accumulation time for the focus detection region that has not been selected.
[0010]
(Function)
In the present invention, it is possible to control the charge accumulation time by converting only the characteristic value into a digital signal for the focus area that is not selected from the output from the charge accumulation type image sensor.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a configuration diagram when a focus detection apparatus according to an embodiment of the present invention is used in a camera.
In FIG. 1, the apparatus splits a light beam from a subject passing through a photographing optical system 3 in a lens 2 into a direction of a sub mirror 5 and a viewfinder 6 by a main mirror 4, and a light beam in the direction of the sub mirror 5 is reflected by the sub mirror 5. Then, it is configured to enter the focus detection device 9. In addition, a lens driving device 10, an area selection device 12, and an activation device 11 that exchange signals with the focus detection device 9 are provided.
[0012]
The body 1 is a camera body and includes an apparatus and members described below.
The lens 2 is configured to be detachable from the body 1, and guides the light flux from the subject into the body 1 by the photographing optical system 3 in the lens 2.
The main mirror 5 is a half mirror for dividing the light beam from the photographing optical system 3 in the direction of the sub mirror 5 and the viewfinder 6.
[0013]
The sub mirror 5 is a mirror that deflects the light beam that has passed through the main mirror 4 toward the bottom of the body 1 and guides it to the focus detection device 9 that is disposed in the vicinity of the planned focal plane of the photographing optical system 3.
The focus detection device 9 detects the focus adjustment state of the imaging optical system in the focus detection area in the imaging screen selected by the area selection device 12 described later, and drives and controls the lens driving device 10 according to the detection result. It is a device. As will be described later, it is composed of a focus detection optical system 7, an image sensor 8, and a microcomputer 90.
[0014]
The lens driving device 10 includes a motor and the like, and is a device that achieves a focused state by moving the photographing optical system 3 in the optical axis direction.
The activation device 11 is a device for activating the focus detection operation or the automatic focus adjustment operation of the focus detection device 9, and is also used as, for example, a release button for performing a release operation. When the release button is released, the focus detection operation or the automatic focus adjustment operation of the focus detection device 9 is prohibited, and the focus detection operation of the focus detection device 9 or by the transition from the release button release to the half-pressed state. The automatic focus adjustment operation is activated, and the release operation is performed by fully pressing the release button.
[0015]
The area selection device 12 is a device that manually or automatically selects a specific focus detection area when the focus detection device 9 can perform focus detection in a plurality of focus detection areas in the shooting screen. In the present embodiment, as shown in FIG. 2, two focus detection areas, a first focus detection area and a second focus detection area, are provided, and one of them is selected.
[0016]
With the above apparatus, a subject image can be focused on a film surface (not shown).
FIG. 2 is a diagram showing a focus detection area in the photographing screen.
In FIG. 2, the first focus detection area corresponds to light receiving units 80 and 81 (first light receiving unit) described later, and the second focus detection area corresponds to light receiving units 82 and 83 (second light receiving unit).
The focus detection apparatus 9 in FIG. 1 will be described with reference to FIGS.
[0017]
FIG. 3 is a diagram illustrating the configuration of the focus detection device 9, and FIG. 4 is a diagram illustrating the focus detection optical system 7 in the focus detection device 9.
In FIG. 3, the focus detection device 9 is roughly composed of a focus detection optical system 7, an image sensor 8, and a microcomputer 90.
First, the focus detection optical system 7 will be described with reference to FIG. 4 illustrates the imaging optical system 3 and the image sensor 8 in order to explain the correspondence between the imaging optical system 3 in FIG. 1 and an image sensor 8 described later.
[0018]
The focus detection optical system 7 includes a field mask 71 having openings 70A and 70B, condenser lenses 72A and 72B, a diaphragm mask 75 having two pairs of aperture openings 73A and 74A, and 73B and 74B, The imaging lenses 76A and 77A, and 76B and 77B are included.
In the configuration as described above, the two pairs of aperture openings 73A and 74A, 73B and 74B are a pair of regions symmetrical to the optical axis of the surface 30 near the exit pupil of the photographing optical system 3 by the condenser lenses 72A and 72B. 31 and 32 are projected. A light beam passing through the regions 31 and 32 first forms a primary image near the field mask 71. The primary image formed in the openings 70A and 70B of the field mask 71 further passes through the condenser lenses 72A and 72B, the two pairs of aperture openings 73A and 74A, and 73B and 74B, and the two pairs of re-imaging lenses 76A and 77A. , 76B and 77B form two pairs of secondary images on the light receiving portions 80 and 81 and the light receiving portions 82 and 83 of the image sensor 8 described later. (The actual optical axis is bent by the sub-mirror 5 in FIG. 1)
Next, returning to FIG. 3, the image sensor 8 will be described.
[0019]
The image sensor 8 is a charge storage type image sensor, and includes a first light receiving unit, a second light receiving unit, a peak hold circuit 84, and a control circuit 85.
The first light receiving unit is a pair of light receiving units 80 and 81 each including a plurality of pixels, and receives an optical subject image from the focus detection optical system 7 and outputs an electrical subject image signal.
[0020]
The second light receiving unit is a pair of light receiving units 82 and 83 similar to the first light receiving unit.
The peak hold circuit 84 is arranged in parallel with the output line 87 and corresponds to the peak value of the subject image signal (corresponding to the brightest part) while the subject image signal of the first light receiving unit or the second light receiving unit is output and transferred. Signal value) is detected and held, and the peak value detected at the time when the output transfer of the subject image signal is completed is output.
[0021]
The control circuit 85 is a circuit that generates control signals for the start, end, and transfer of charge accumulation in the first light receiving unit and the second light receiving unit. Further, the first light receiving unit and the second light receiving unit are controlled independently.
And what constitutes these image sensors 8 is mounted as one chip on the same semiconductor substrate.
The operation of the image sensor 8 configured as described above will be briefly described.
[0022]
The first light receiving unit and the second light receiving unit are configured to output a pair of subject images formed on the first light receiving unit and the second light receiving unit by the focus detection optical system 7 according to a control signal output from the control circuit 87. Charge accumulation is performed for the accumulation time. The charges accumulated corresponding to the intensity distribution of each pair of subject images are output according to the transfer pulse signal as analog subject image signals for each pixel unit from a well-known CCD shift register provided in each light receiving unit. Serial transfer from the line 87 to the microcomputer 90 is performed.
[0023]
Further, the control circuit 85 controls the transfer timing of the first light receiving unit and the second light receiving unit so that the outputs of the first light receiving unit and the second light receiving unit do not appear simultaneously on the output line 87.
In addition, the peak hold circuit 84 outputs the peak value detected when the output transfer of the subject image signal is completed to the microcomputer 90 via the output line 87.
[0024]
The relative positional relationship between the pair of secondary images on the light receiving portions 80 and 81 and the pair of secondary images on the light receiving portions 82 and 83 changes according to the focus state of the photographing optical system 3, respectively. Will do. Then, by detecting the relative positional relationship between each output pair of secondary images, the microcomputer 90 described later detects the focus adjustment state of the photographing optical system 3.
Further, the output timing of the signal from the image sensor 8 will be described in detail with reference to FIG.
Next, the microcomputer 90 will be described.
[0025]
The microcomputer 90 is for performing accumulation time control and focus detection calculation of the first light receiving unit and the second light receiving unit in the image sensor 8, and includes an AD conversion device 91 and a focus detection calculation unit. 92 and a sensor control unit 93.
The AD converter 91 is connected to the output line 85 and AD converts the subject image signal and the peak signal. When the first focus detection area is selected by the area selecting device 12, the subject image signal corresponding to the first light receiving unit, the peak signal, and the peak signal corresponding to the second light receiving unit are AD-converted to obtain the second light receiving The subject image signal corresponding to the part is not AD converted. When the second focus detection area is selected by the area selection device 12, the subject image signal corresponding to the second light receiving unit, the peak signal, and the peak signal corresponding to the first light receiving unit are AD-converted, and the first The subject image signal corresponding to the light receiving unit is not AD converted.
[0026]
The focus detection calculation unit 92 adjusts the focus of the first focus detection area based on the subject image data subjected to AD conversion corresponding to the first light receiving unit when the area selection device 12 selects the first focus detection area. Detect state. When the second focus detection area is selected by the area selection device 12, the focus adjustment state of the second focus detection area is detected based on the subject image data subjected to AD conversion corresponding to the second light receiving unit. Since focus detection is already known, it will not be described in detail.
[0027]
The sensor control unit 93 includes the first light receiving unit and the second light receiving unit so that the output level of the subject image signal output from the first light receiving unit and the second light receiving unit is appropriately within the AD conversion range of the AD conversion device 91. The accumulation time of the light receiving unit is determined, and a command is sent to the control circuit 85 via the control line 86 to control the accumulation time of the first light receiving unit and the second light receiving unit.
The AD value of the peak signal corresponding to the first light receiving unit is PA, the accumulation time when the peak signal is obtained is TAP, the AD value of the peak signal corresponding to the second light receiving unit is PB, and the peak signal is obtained. When the accumulation time at this time is TAB and the target peak value is PX, the next accumulation times TAN and TBN of the first light receiving unit and the second light receiving unit are calculated by Equation 1.
[0028]
[Expression 1]
TAN = TAP × PX / PA
TBN = TBP × PX / PB
Thus, by determining the next accumulation time, it can be expected that the next peak value becomes the target value PX.
As described above, the subject image signal corresponding to the focus detection area that is not selected does not need to be AD-converted, so that the microcomputer 90 can perform another work correspondingly. In addition, the focus detection area that has not been selected operates with the accumulation time controlled so that the subject image signal level is appropriate, so even if the focus detection area is switched, the subject image signal of the appropriate level is immediately available. Therefore, the focus detection calculation can be performed, so that the responsiveness is improved.
[0029]
Further, since the output lines of the plurality of light receiving sections are made common, the number of terminals can be saved, and there is an advantage that only one peak hold circuit 84 is required.
Further, since the output line of the peak hold circuit 84 is made common with the output line of the subject image signal, the number of terminals can be further saved.
FIG. 5 is a timing chart of the output of the image sensor 8.
[0030]
At time T1, the accumulation of the first light receiving unit is completed, and the transfer of the charge accumulated in the first light receiving unit is started. Between time T1 and time T2, a signal for each pixel is output according to the transfer pulse signal. When the transfer ends at time T2, the peak value of the subject image signal output between time T1 and time T2 is output as a peak signal. When the accumulation of the second light receiving unit is completed at time T3 and the transfer of the charge accumulated in the second light receiving unit is started, a subject image signal is output instead of the peak signal, and between time T3 and time T4. The signal for each pixel is output according to the transfer pulse signal. When the transfer ends at time T4, the peak value of the subject image signal output between time T3 and time T4 is output as a peak signal.
FIG. 6 is a block diagram showing the configuration of the peak hold circuit 84 in FIG.
[0031]
The peak hold circuit 84 includes SW20, SW21, SW24, a comparison circuit 22, a signal holding circuit 23, and a sequence circuit 25.
The SW 20 is a switch for switching whether or not to input a subject image signal to the SW 21 according to a control signal from the sequence circuit 25.
The SW 21 is a switch for switching whether or not a signal input from the SW 20 is input to the signal holding circuit 23 according to a control signal from the comparison circuit 22.
[0032]
The SW 24 is a switch for switching and outputting a signal input from the signal holding circuit 23 or a subject image signal according to a control signal from the sequence circuit 25.
The comparison circuit 22 is a circuit for comparing a signal input from the SW 20 and a signal input from the signal holding circuit 23 by a control signal from the sequence circuit 25.
[0033]
The signal holding circuit 23 is a circuit for holding a signal input from the SW 21 according to a control signal from the sequence circuit 25 and outputting the signal to the comparison circuit 22 and the SW 24.
The sequence circuit 25 receives, from the control circuit 85, a transfer start signal indicating the transfer start timing of the subject image signal, a transfer end signal indicating the transfer end timing, and a transfer pulse signal indicating the transfer timing for each pixel constituting the light receiving unit. The operation of the SW 20, the comparison circuit 22, the signal holding circuit 23, and the SW 24 is controlled in accordance with the signal.
Next, the operation of the block diagram of FIG. 6 will be described.
[0034]
The subject image signal line is input to SW20 and SW24. The output of the signal holding circuit 23 is also input to the SW 24. The sequence circuit 25 connects the SW 20 during the period in which the subject image signal is transferred, selects the subject image signal to be input to the SW 21 and the comparison circuit 22, and selects the SW 24 to output the subject image signal.
[0035]
Upon receiving the transfer start signal, the sequence circuit 25 resets the signal holding circuit and sets the holding signal to the 0 level. The output of the signal holding circuit 23 is input to the comparison circuit 22, and the comparison circuit 22 synchronizes the level of the subject image signal and the level of the output signal of the signal holding circuit 23 with the transfer pulse signal during the transfer period of the subject image signal. Compared with each pixel, when the level of the subject image signal exceeds the level of the output signal of the signal holding circuit 23, the SW 21 is turned on to hold the subject image signal in the signal holding circuit 23. repeat. If such an operation is repeated, the peak signal of the subject image signal is held in the signal holding circuit 23 at the end of the transfer of the subject image signal.
[0036]
The sequence circuit 25 selects the SW 24 to output the holding signal of the signal holding circuit 23 according to the transfer end signal.
Accordingly, the peak value of the subject image signal is output in accordance with the end of the transfer of the subject image signal.
FIG. 7 is an operation flowchart of the microcomputer 90.
[0037]
The operation of the microcomputer 90 will be described with reference to FIG.
In step S100, the process proceeds to step S101 when the power is turned on.
In step S101, the charge accumulation operation of the first light receiving units 80 and 81 is performed. The storage time is a fixed value or a value according to the output of a photometric device (not shown) immediately after the power is turned on, and if it is not immediately after the power is turned on, the storage time TAN determined by Equation 1 in step S107 described later is adopted. . The accumulation time at this time is stored as TAP.
[0038]
In step S102, it is tested whether or not the release button is half-pressed. If the release button is in the open state, step detection is not performed in the first focus detection area corresponding to the first light receiving unit. In step 106, if the button is half-pressed, the focus detection operation or the automatic focus adjustment operation is activated.
[0039]
In step S103, it is tested whether or not the first focus detection area, that is, the first light receiving unit is selected by the area selecting device 12, and if the first light receiving unit is selected, the process proceeds to step S104, where it is selected. If not, the process proceeds to step 106 without performing focus detection in the first focus detection area corresponding to the first light receiving unit.
In step S104, the subject image signal is AD converted for each pixel.
[0040]
In step S105, a known image shift detection calculation is performed based on the obtained AD conversion data to detect the focus adjustment state of the first focus detection area.
In step S106, the peak signal PA that appears after completion of the transfer of the subject image signal is AD-converted to obtain the peak value PA.
In step S107, the next storage time TAN is calculated and stored from the peak value PA and the storage time TAP based on Equation 1, and the process proceeds to step S108.
[0041]
In step S108, the charge accumulation operation of the second light receiving portions 82 and 83 is performed. The storage time is a fixed value or a value according to the output of a photometric device (not shown) immediately after the power is turned on, and the storage time TBN determined by Equation 1 in step S114 to be described later is adopted if it is not immediately after the power is turned on. . The accumulation time at this time is stored as TBP.
[0042]
In step S109, it is tested whether or not the release button is half-pressed. If the release button is in the open state, step detection is not performed in the second focus detection area corresponding to the second light receiving unit. Proceed to 113, and if it is half-pressed, the focus detection operation or automatic focus adjustment operation is activated, and the flow proceeds to step S110.
[0043]
In step S110, it is tested whether or not the second focus detection area, that is, the second light receiving unit is selected by the area selection device 12, and if the second light receiving unit is selected, the process proceeds to step S111 and is selected. If not, the process proceeds to step 113 without performing focus detection in the second focus detection area corresponding to the second light receiving unit.
In step S111, the subject image signal is AD converted for each pixel.
[0044]
In step S112, a known image shift detection calculation is performed based on the obtained AD conversion data, and the focus adjustment state of the second focus detection area is detected.
In step S113, the peak signal that appears after the transfer of the subject image signal is AD-converted to obtain the peak value PB.
In step S114, the next accumulation time TBN is calculated from the peak value PB and the accumulation time TBP based on Equation 1 and stored. Then, returning to step 101, the above operation is repeated.
In the above embodiment, the image sensor is provided with a circuit for detecting the peak value of the subject image, and the peak value detected after the transfer of the subject image signal is output to the outside, and the external control circuit uses the peak value. However, in general, data representing the characteristics of the subject image signal other than the peak value of the subject image signal is detected by the characteristic value detection circuit built in the image sensor to control the subject. The characteristic value detected after completion of the transfer of the image signal may be output to the outside, and the external control circuit may control the next accumulation time of the image sensor based on the characteristic value.
The case where the accumulation time is controlled using the average value of the subject image signal will be described below.
[0045]
When the accumulation time is controlled using the average value of the subject image signal, the next accumulation time can be determined by setting SP as the average value of the current subject image signal, TP as the current accumulation time, and SX as the next target average value. TN can be calculated as shown in Equation 2.
[0046]
[Expression 2]
TN = TP × SX / SP
By determining the next accumulation time in this way, it can be expected that the average value of the next subject image becomes the target value SX.
FIG. 8 is a block diagram showing a configuration of an average value detection circuit built in the image sensor 8 when the accumulation time control by the average value is performed. This average detection circuit can be implemented by replacing the peak hold circuit 84 of FIG.
[0047]
The average value detection circuit includes SW30, SW32, an addition circuit 31, and a sequence circuit 33.
The SW 30 is a switch for switching whether or not to input a subject image signal to the adding circuit 31 according to a control signal from the sequence circuit 33.
The SW 32 is a switch for switching and outputting the signal input from the adder circuit 32 or the subject image signal according to the control signal from the sequence circuit 33.
[0048]
The adder circuit 31 is a circuit for adding the signals input from the SW 30 according to the control signal from the sequence circuit 33 and outputting the added signal to the SW 32.
The sequence circuit 33 receives, from the control circuit 85, a transfer start signal that represents the transfer start timing of the subject image signal, a transfer end signal that represents the transfer end timing, and a transfer pulse signal that represents the transfer timing for each pixel constituting the light receiving unit. This is a circuit for controlling the operation of SW30, adder circuit 31, and SW32 in accordance with the signal.
[0049]
Next, the operation of the average value detection circuit of FIG. 8 will be described.
The line of the subject image signal is input to SW30 and SW32. The output of the adder circuit 23 is also input to the SW 32. The sequence circuit 33 connects the SW 30 during the period in which the subject image signal is transferred, inputs it to the adder circuit 31, and selects the SW 32 to output the subject image signal.
[0050]
When the sequence circuit 33 receives the transfer start signal, the sequence circuit 33 resets the addition circuit and sets the addition signal of the addition circuit 31 to 0 level.
The adding circuit 31 adds a value obtained by gradually reducing the output for each pixel by the total number of pixels in synchronization with the transfer pulse signal. If such an operation is repeated, the adder circuit 31 will eventually hold a signal corresponding to the average value of the subject image signal when the transfer of the subject image signal is completed.
[0051]
The sequence circuit 33 selects the SW 32 so that the holding signal of the adder circuit 31 is output in accordance with the transfer end signal.
Therefore, the average value of the subject image signal is output in accordance with the end of the transfer of the subject image signal.
In the following, a case will be described in which the accumulation time is controlled using the maximum contrast value of the subject image signal (maximum absolute value of the difference between adjacent or separated pixel outputs) as the characteristic value.
[0052]
When the accumulation time is controlled using the maximum contrast value of the subject image signal as the characteristic value, the maximum contrast value of the current subject image signal is CP, the current accumulation time is TP, and the next target contrast maximum value is CX. For example, the next accumulation time TN can be calculated as shown in Equation 3.
[0053]
[Equation 3]
TN = TP × CX / CP
By determining the next accumulation time in this way, it can be expected that the next maximum contrast value of the subject image will be the target value CX.
FIG. 9 is a block diagram showing a configuration of a part of the contrast maximum value detection circuit built in the image sensor 8 when the accumulation time control by the contrast maximum value is performed.
[0054]
The maximum contrast value detection circuit is achieved by inputting a contrast signal instead of the raw subject image signal to the peak hold circuit 84 shown in FIG. 6, and the block shown in FIG. 9 is added to the output line of the SW 20 in FIG. That's fine.
In FIG. 9, the contrast maximum value detection circuit includes a one-pixel delay circuit 40, a difference circuit 41, and an absolute value conversion circuit 42.
[0055]
The one-pixel delay circuit 40 is a circuit for delaying the input subject image signal by one pixel.
The difference circuit 41 is a circuit for obtaining a difference between the subject image signal and the delayed subject image signal from the one-pixel delay circuit 40.
The absolute value circuit 42 is a circuit for converting the output of the difference circuit 41 into an absolute value and outputting it.
[0056]
The subject image signal is input to the one-pixel delay circuit 40 and the difference circuit 41.
By adding the block of FIG. 9 to the block of FIG. 6, the maximum value of the contrast of the subject image signal is output according to the end of the transfer of the subject image signal.
In the above embodiment, the characteristic value of the subject image signal such as the peak value has been described as being extracted from both of the pair of light receiving units (for example, both of the light receiving units 80 and 81). (For example, one of the light receiving units 80 and 81) may be extracted.
[0057]
Further, although the output of the characteristic value detection device and the output of the subject image signal are made common, they may be different.
Further, although the case where the characteristic value detection device is integrated with the image sensor as one chip has been described, it may be configured as a separate chip outside the image sensor.
Although the focus detection system that performs focus detection using a light beam that has passed through the photographing optical system has been described, it goes without saying that the present invention can also be applied to a so-called triangulation type passive distance measurement system.
[0058]
For example, two lenses for forming a subject image are arranged as a distance detection optical system separated by a base line length, and a pair of charge storage type light receiving parts are arranged in the vicinity of the imaging plane behind the lenses. And receiving two subject images formed by the two lenses, outputting a subject image signal corresponding to the intensity distribution of the subject image, and converting the subject image signal from data obtained by AD conversion of the pair of subject images. Calculate the relative interval, calculate the relative interval, the distance between the lens and the light receiving unit and the distance from the base line to the subject, detect and hold the characteristic value of the subject image signal, and output it as a characteristic signal A characteristic value detection device may be provided, and the charge accumulation time of the light receiving unit may be controlled based on a value obtained by AD converting the characteristic signal.
[0059]
【The invention's effect】
As described above, according to the present invention, all the pixel signals of the conventional image sensor are AD-converted to perform the calculation of the focus adjustment state and the accumulation control of the charge accumulation type image sensor. For the detection region, only the characteristic value from the characteristic value detecting means can be AD converted to control the accumulation of the image sensor, so that the AD conversion is performed up to a signal for calculating an unnecessary focus adjustment state. The processing time required for AD conversion of the conventional pixel signal can be directed to other processing, and improvement in system responsiveness can be expected.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.
FIG. 2 is a diagram illustrating an arrangement of focus detection areas on a shooting screen.
FIG. 3 is a block diagram illustrating a configuration of a focus detection apparatus.
FIG. 4 is a perspective view showing a configuration of a focus detection optical system.
FIG. 5 is a time chart showing the output of the image sensor.
FIG. 6 is a block diagram showing a configuration of a peak hold circuit.
FIG. 7 is an operation flowchart of the microcomputer.
FIG. 8 is a block diagram showing a configuration of an average value detection circuit.
FIG. 9 is a block diagram showing a part of the configuration of a maximum contrast value detection circuit.
[Explanation of symbols]
1 body
2 Lens
3 Shooting optical system
4 Main mirror
5 Submirror
6 Finder
7 Focus detection optical system
8 Charge storage type image sensor
9 Focus detection device
10 Lens drive device
11 Starter
12 Area selection device
84 Peak hold circuit
90 Microcomputer
91 AD converter

Claims (9)

A focus detection device for detecting a focus adjustment state of the main optical system in a plurality of regions of a focal plane on which the main optical system forms a subject image;
A plurality of charge storage type image sensors which are provided corresponding to the plurality of regions, each of which is composed of a plurality of pixels, and which repeatedly outputs serial analog signals corresponding to the charges stored in the pixels;
Selecting means for selecting a region for focus detection from the plurality of regions;
Characteristic value detection means for detecting and holding the characteristic value of the analog signal corresponding to each image sensor, and outputting the characteristic value as a characteristic signal;
AD conversion means for converting the analog signal and the characteristic signal repeatedly output into a digital signal;
Calculation means for calculating a focus adjustment state in the plurality of regions based on an output from each image sensor digitized by the AD conversion means;
Accumulation control means for repeatedly controlling the charge accumulation time of the corresponding charge accumulation type image sensor based on the characteristic signal digitized by the AD conversion means,
The AD conversion means AD-converts only the analog signal corresponding to the region selected by the selection means among the analog signals output from the plurality of charge storage type image sensors,
The calculation means calculates a focus adjustment state in the selected area based on an output from the charge storage type image sensor digitized by the AD conversion means,
The accumulation control means controls the next charge accumulation time of the charge accumulation type image sensor for the area selected by the selection means and the area not selected based on the characteristic signal digitized by the AD conversion means. A focus detection device.   The accumulation control means controls the charge accumulation time of the charge accumulation type image sensor corresponding to the selected region based on the output from the charge accumulation type image sensor digitized by the AD conversion means. The focus detection apparatus according to claim 1.   2. The focus detection apparatus according to claim 1, wherein the plurality of charge storage type image sensors and the characteristic value detection means are formed as one chip on the same semiconductor substrate.   3. The focus detection apparatus according to claim 2, wherein the characteristic value detection means is shared by the plurality of charge storage type image sensors.   2. The focus detection apparatus according to claim 1, wherein the AD conversion unit, the calculation unit, and the accumulation control unit are configured on the same microprocessor.   2. The focus detection apparatus according to claim 1, wherein the characteristic value detection means detects and holds a peak value of the analog signal and outputs the detected peak value to the outside as a peak signal.   2. The focus detection apparatus according to claim 1, wherein the characteristic value detection means detects and holds an average value of the analog signal and outputs the detected average value to the outside as an average signal.   2. The focus detection apparatus according to claim 1, wherein the characteristic value detecting means detects and holds a contrast value of the analog signal and outputs the detected contrast value to the outside as a contrast signal.   A camera comprising the focus detection apparatus according to claim 1.

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