JPH0268511A - Automatic focusing camera equipped with auxiliary lighting device - Google Patents

Abstract

PURPOSE:To start projecting auxiliary light while eliminating a meaningless integration time and to shorten an operation time by monitoring data read out of a photoelectric converting element without destruction and the integration time at the readout point of the data before integrating operation is completed and predicting the brightness of a subject. CONSTITUTION:An image of the object is formed by an optical system on a focus detecting means 3 including an image sensor such as a CCD having a nondestructive reading function. This image sensor is constituted by arraying electrostatic induction phototransistors linearly or in two dimensions, a photoelectric signal is integrated by the nondestructive read, and the halfway process of data storage is monitored by a control means 4. The control means 4 predicts the brightness of the subject from the read out nondestructive data and the integration time at the readout point of this data before the integrating operation by a focus detecting means 3 is completed and operates an auxiliary light means 5 when judging that the predicted brightness is smaller than a prescribed value, thereby projecting the auxiliary light on the subject.

Description

DETAILED DESCRIPTION OF THE INVENTION (Prior Art) Cameras having an automatic focus function have recently become widespread, and various focus detection devices for this automatic focus have been developed. According to conventional focus detection devices, when the subject brightness is low or the subject contrast is low, an auxiliary light source such as an electronic flash device or a high-brightness LED lamp is used to project light onto the subject to enable focus detection. is being carried out.

In a combination of a focus detection device constituted by a photoelectric conversion element such as a CCD and an auxiliary light source, auxiliary light source control conventionally performed using a microcomputer is performed according to the flow chart shown in FIG. In addition to focus detection, a microcomputer built into an actual camera performs various controls such as photometry, aperture control, and lens drive, but here we will focus only on the focus detection process.

When the focus detection subroutine is called, the presence or absence of the auxiliary light flag is first determined. When this auxiliary light flag is set, the auxiliary light is turned on prior to the start of integration such as COD. Since this auxiliary light flag is set based on the state of CCD data, it will not be set during an initial focus detection operation in the camera operation sequence.

Therefore, the process of determining the presence or absence of the auxiliary light is meaningful in the second and subsequent focus detection operations.

Next, an integral start is applied to start the integration of the CCD signal, and a timer is started to define the maximum value of the integration time. The reason for specifying the maximum value of this integration time is to prevent that if the subject brightness is too low, the COD will be charged only gradually and the integration will not be completed easily.

When the integration is started, the microcomputer selects the COD
The timer monitors whether an integration completion signal is output from the timer and determines whether the integration time has reached a specified value based on the timer's end signal. If the timer ends before the integration completion signal is generated, it is determined that the subject brightness is low and focus detection is impossible. Therefore, the auxiliary light flag is set.

When the integration completion signal arrives, the microcomputer
The CD data is accepted and the amount of focus shift is calculated in the calculation routine. In this calculation routine, it is also determined whether the subject has the contrast necessary for focus detection. In contrast determination, when it is determined that the contrast state is low, an auxiliary light flag is set to increase the contrast with auxiliary light. When it is determined that there is a contrast, after leaving the focus detection flow,
The photographing lens is controlled based on the calculated amount of deviation.

When the series of focus detection operations as described above are completed, finally, if the auxiliary light is on, the auxiliary light is turned off and exits from the focus detection flow.

(Problems to be Solved by the Invention) According to the conventional auxiliary light control method as described above, there is a problem that it is not possible to determine the necessity of the auxiliary light unless the data is recognized by integrating once. This problem becomes particularly serious when the brightness of the subject is low and data cannot be collected. In this case, integration is performed just to determine whether to turn on the auxiliary light, and this integration time is almost meaningless for focus detection and slows down the camera's operation sequence. I will let you do it.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an autofocus camera with an auxiliary illumination device that eliminates meaningless integration times.

(Means and effects for solving the problem) According to the present invention, stored data can be read out without being destroyed (hereinafter referred to as non-destructive reading) S! P.T.
A 5IT (static induction transistor) image sensor is used in which (static induction phototransistors) are arranged in lines and areas. If the value is so low that it is judged that it is meaningless to continue the integration, the projection of the auxiliary light is started from the middle of the integration. Also, C
Even in the case of an image sensor such as a CD, the output of a light receiving element provided to monitor charge accumulation can be read out during integration, thereby making it possible to control the auxiliary light.

That is, as shown in FIG. 1, a subject 1 is imaged by an optical system 2 on a focus detection means including an image sensor such as a COD having a non-destructive readout function.

The photoelectric signal is integrated in this focus detection means, and the auxiliary light control means 4 predicts the subject brightness based on the non-destructive data read out before the end of the integration operation in the focus detection means and the integration time at the time when this data is read out. and when it is determined that the predicted brightness is below the specified value, activates the auxiliary light means 5,
Emits fill light onto the subject.

(Embodiment) The present invention will be explained in detail with reference to the block diagram shown in FIG.

The light beam from the exit pupil of the photographic lens 11 is divided by the splitting optical system 12, and the A-group sensor 1 of the line sensor 13 is composed of a photoelectric conversion element capable of non-destructive readout such as SIT.
Images are formed on the 3A and 8 group sensors 13B, respectively.

The interface circuit 14 includes a line sensor control circuit and an A/D converter (not shown), and when a control signal is supplied from the microcomputer 15, the line sensor control circuit operates and outputs a sensor output signal.

When the integral signal reaches an appropriate level, the integral output is converted into a digital value by the A/D converter and supplied to the microcomputer 15. When the microcomputer requests the non-destructive read mode, the interface circuit 14 converts the data being integrated into a digital value and supplies it to the microcomputer 15.

The microcomputer 15 controls the light emitting circuit 1 in order to control the sequence of the entire system and perform various calculations.
6, coupled to a shutter control circuit 19, an aperture control circuit 20, a photometry processing circuit 21, a film winding circuit 22, a film sensitivity reading circuit 23, a motor drive circuit 24, a release switch 25, and a mode setting switch 26.

The light emitting circuit 16 controls an auxiliary light source 17 such as a lamp or a light emitting diode based on a control signal from the microcomputer 15. The shutter control circuit 19 is based on the shutter time signal from the microcomputer.
The shutter speed Tv is determined and the leading and trailing curtains of the focal plane shutter are controlled.

The aperture control circuit 20 controls the quick return mirror to move up and down based on the signal of the aperture value Av calculated by the microcomputer 15, and also controls the aperture of the lens.

The photometry processing circuit 21 is a silicon blue cell (B B C
) etc. 71 - 1 detects the subject brightness from the photocurrent of the optical element 21 a and sends a signal of the subject brightness By to the microcomputer 15 .

When the exposure of the film is completed, the film winding circuit 22 drives the winding motor in response to a command from the microcomputer 15, and winds the film by -frames.

The mode setting switch 26 is a switch for setting various exposure modes and AF (autofocus) modes.

The release switch 25 is a two-stage stroke switch. The microcomputer 15 performs automatic focusing (AF) and photometry using the first switch signal of the release switch, and the microcomputer 15 performs exposure control using the second switch signal. The microcomputer 15 determines the calculated lens movement amount necessary for focusing,
A motor 27 is driven by a motor drive circuit 24 to move the photographing lens 11 to a focal point.

5I according to Figure 3 (a) (b) and Figure 4 (a) (b)
The operation of a sensor using PT will be explained.

According to the sensor shown in FIG. 3(a), the shift register 31 transfers the output data of each 5IPT pixel sampled and held in the readout circuit 32 to the sensor output terminal O6.
Generates control signals for more serial output. The readout circuit 32 has a function of sampling and holding the output of each SIT pixel and amplifying it.

The reset circuit 34 resets the charge accumulated in the gate of 5IPT at the start of integration. The monitor circuit 34 detects the maximum value of each pixel of SIT and outputs the monitor output terminal M.
Output from O3. The interface circuit 14 constantly monitors the monitor output during integration, and when the monitor output reaches the maximum value that can be converted by the A/D converter, it reads the sensor output and finishes planting.

FIG. 3(b) shows an equivalent circuit of the sensor of FIG. 3(a), and before explaining this circuit, the configuration and operation of the 5IPT will be explained with reference to FIGS. 4(a) and (b).

5IPT consists of a drain region (n+), an epitaxial layer (n-) with a low impurity concentration grown on the drain region (n+), and a shallow source region (n+) formed in this epitaxial layer. , and a gate region (p+) formed to surround this source region, and an MO9 type capacitor ff1cG is formed on the gate electrode.

When the interface circuit 14 receives the integration start signal,
It is necessary to reset the charge accumulated in the capacitor CG of 5IPT. Therefore, M connected to the source electrode of 5IPT
OS) Transistor Qφ5゜Ql5. A gate pulse φR1 is applied to the gates of Q25..., and these MOS
) transistor is turned on.

At this time, the potential of φG rises to VDD. By this operation, the holes accumulated in CG flow to the source S and are reset. At this time, if the forward voltage drop between the gate G and source S of 5IPT is vF, then the capacitance CG is VD
Charged to the voltage of D-VP.

At the same time as this operation, MOS transistors Qφ2. It is necessary to erase the charge accumulated in the capacitance QCG of the gate electrode of Ql2°Q22.... This capacitor CG temporarily holds the data when reading the data of 5IPT, and interface circuit 1
If we include the A/D converter No. 4, it can be considered as a hold capacitor for the sample and hold circuit for the A/D converter.

In order to erase the charge on this capacitor, at the same time a voltage is applied to φR1, Qφl, Qll, Q2
It is sufficient to apply a gate pulse φT to turn on 1... This operation causes Qφ2, Ql2. Q2
The gates of 2... are connected to GND, and the charge of CG is discharged.

When the above reset operation is completed, the interface circuit 14 drops φG to the GND potential to start integration. As a result, the potential of gate G 4;i-(VDD-VF
), and as shown in FIG. 4(b), the gate and drain of the 5IPD are in a reverse bias state and a depletion layer is formed. At this time, the band gap value of silicon (E g
When light having energy greater than -1, 1 eV) is incident, electron-hole pairs are generated. Since there is a reverse bias between the drain and gate, a voltage is generated, and the electric field moves electrons to the drain region and holes to the gate region.

When holes enter the gate, the gate voltage increases,
This voltage change is output to the source S.

The maximum value of the output voltage of the source S of each 5IPT is detected by a monitor circuit 35 formed of MOS transistors QφG, QIB, 02G, . . . , and outputted to the interface circuit 14 from a monitor output terminal MO3. The interface circuit 14 is connected to the MO at the same time as the integration starts.
Monitor that the S output becomes an appropriate voltage for focus detection. When the appropriate voltage is reached, gate pulse φT is applied and Qφ
l, Qll, Q21... as ONL, Qφ2. Q
l2. The output voltage of each 5IPT is held in the gate capacitance of Q22... The held voltage of 5IPT is applied to each corresponding MOS transistor, for example, Qφ4.
If the output is, the impedance is converted by a source follower amplifier constituted by transistors Qφ2 and Qφ3 and output. These outputs are coupled to the sensor output terminal O8 through MOS transistors Qφφ, Qlφ, Q2φ, . The interface circuit 14 is
In order to serially input the output of 5IPT, Qφφ,
It is necessary to turn on Qlφ, Q2φ, etc. in order. Therefore, the interface circuit 14 connects the shift register 3
1, two-phase clocks φ1 and φ2 are input, and a start pulse φST is manually inputted at the time of reading. Through this operation, gate pulses are sequentially output, and the MOS transistors are sequentially turned on. At this time, a gate pulse φR2 is applied to Ql to reset the OS line every time one output of 5IPT is output, and Ql is turned ON.

The analog outputs of the 5IPTs that are serially output are sequentially converted into digital codes by the A/D converter in the interface circuit 14, and then sent to the microcomputer 1.
5.

The sensor readout described above is based on the monitor output.
I executed it after the standard value was reached and the output from the 5IPT was at a level sufficient for focus detection, but the readout itself was
It can be executed regardless of monitor output. Moreover, 5I
The charges accumulated in the CG of the PT are not destroyed unless the reset circuit is operated, so they can be read out any number of times.

Therefore, by calculating the ratio of the sensor data read out midway before the monitor output reaches the specified value and the time from the start of integration to the point in time when the reading is performed midway, the time until the monitor output reaches the specified value can be calculated. That is, the integration time can be predicted.

Since this integration time and the subject brightness are proportional, it is also possible to predict the subject brightness. When it is determined that auxiliary light is necessary based on the predicted brightness, the auxiliary light source 17 is turned on during the integration.

As a result, the number of integration operations can be reduced by one time compared to when control is performed using a sensor such as a CCD.

The focus detection device of this invention will be further explained.

The first part and the second part of the photographic lens sandwich the optical axis of the photographic lens.
2 created by the subject light flux that has passed through each part of
A focal point detection device using a photographing lens exit pupil division method that detects the correlated position of two images to determine the focal state is already known. The two images that have passed through the two imaging lenses Ll and L2 in the splitting optical system 12 shown in FIG. 2 are incident on the A group sensor 13A and the 8 group sensor 13B, respectively, which are comprised of SIT image sensors. It is assumed that the A-group and 8-group sensors each include, for example, 64 elements.

Although the reading of the sensor is carried out as described above, how the amount of defocus of the photographing lens is calculated in the microcomputer 15 will be explained with reference to FIG. The RAM of the microcomputer is now being read.
The A group and 8 group data stored in al, a2-a
84. Let bl, b2-b[14. First, 0
．． Assuming 5≦32 (S: & (7) deviation amount), the following calculation is first performed.

F (M-1)<)' When (M+1), the above formula (1) will shift A column sequentially by 1 shift with B column as the reference.
The sum of the differences between each pixel in column and column B is calculated. Equation (2) above calculates the sum of each pixel in columns A and B while sequentially shifting column B by one shift with column A as a reference.

Next, F (-32), F (-31)...F (0
).

The minimum value MINF (S) is determined from the correlation values of 65 elements of F(1)...F(31) and F(32).

Let M be the shift amount S at this time. That is, F (M) - M
INF (S). This M is the closest integer value to the amount of deviation to the in-focus point. However, this alone is not enough.
Since the focusing accuracy is extremely poor, it is necessary to interpolate the data of F (S) before and after F (M) to improve the accuracy. Therefore, calculation is performed when F (M-1)≧F (M+1). Once the image shift amount S is determined, the focus shift m-K (S-8') is then calculated.

Here, S' is the amount of image shift during focusing, and K is a coefficient determined by the optical system.

Next, the operation of the embodiment shown in FIG. 2 will be explained as shown in FIGS. 6, 7, and 8.
This will be explained with reference to the flowchart shown in the figure.

In FIG. 6 showing the overall flow, when the power of the camera is turned on, the microcomputer 15 turns on the power.
Perform a reset and initialize the output port and memory control flags before starting operation. Next, the mode setting switch is read, and the exposure mode and AF mode are determined by the state of the switch. Next, it is determined whether the first position of the release switch is ON. O
In the case of FF, no operation is performed, and flags such as the exposure permission flag, single completion flag, and auxiliary light flag are reset and switches are read.

In the case of ON, first, the Bv value of the subject brightness is taken in from the photometry processing circuit 21, and the Sv value of the film sensitivity is taken in from the film sensitivity reading circuit 23. Next, the shutter time Tv value and aperture value A set during exposure
The v value is calculated based on the program diagram and displayed. Next, various AF determined by the mode setting switch
mode subroutine is called.

In the AF focus mode, the lens is driven based on photometry and focus detection until the subject is in focus. Once the camera is in focus, focus detection will not be performed until the release switch is set to 0FFL and turned on again.

After focusing, the exposure sequence is allowed to be executed only once.

In the AF servo mode, while the first step of the release switch is pressed, lens drive is performed based on photometry and focus detection. If the subject moves and becomes out of focus even after -degree focusing, lens drive is executed based on focus detection. The exposure sequence can be performed any number of times as long as it is in focus.

In manual mode, only in-focus and out-of-focus indications are performed based on focus detection. Lens adjustments are made by the user himself. At this time, the release switch is set to O.
If N, the exposure sequence can be executed regardless of whether the image is in focus or out of focus.

When returning from the AF resetting subroutine, it is determined whether the single completion flag is set.

This flag is set at the end of the exposure operation, so when the flag is set, it indicates that -degree focusing has been achieved and the exposure operation has been completed. Therefore, when the flag is set, it is not allowed to move to the exposure operation, as already described with respect to the AF lens mode operation, and the process returns to the top flow. And the first step of the release switch is 0FFL.
,, If the flag is reset, the AF resetting mode operation is performed from the beginning. When the single completion flag is not set, it is determined whether the exposure permission flag is set, in the same way as when returning from the AF servo mode or manual mode. Exposure permission flag is AF light, AF
In the servo mode, this is a flag that is set after the focus adjustment operation is completed and focus is achieved. In manual mode, this flag is set regardless of whether the image is in focus or out of focus. This is because in manual mode, whether or not to perform the exposure operation is determined by the user's will, and the exposure operation must be performed whenever the release button is pressed to the second step. . If the exposure permission flag is not set, it is necessary to execute the subroutine again, so the process returns to the top flow. When the flag is set, it is determined whether the second step of the release switch is pressed. When it is OFF, the exposure operation cannot be executed, so return to the top flow) When it is ON, the process moves to the execution of the exposure operation. The By value of the subject brightness from the photometry processing circuit 21 and the Sv value of film sensitivity information from the film sensitivity reading circuit 23 are read into the microcomputer 15, respectively. Then, the microcomputer 15 calculates the final aperture signal Av value and shutter time Tv value based on a predetermined program diagram. Next, microcomputer 1
5 sets the aperture control circuit 20 to the Av value of the aperture signal,
Sends a start signal. Therefore, the aperture control circuit 20 raises the mirror and narrows down the aperture to the set Av value. When the narrowing down is completed, the microcomputer 15 controls the shirt control circuit 19 to
Set the value to v and send the start signal. Then, the shutter control circuit 19 controls the shutter leading and trailing curtains based on the set Tv value. When the shutter control ends, a termination signal is sent to the microcomputer 15. Based on this termination signal, the microcomputer 15 sends a hemi-lowering signal to the aperture control circuit 20 and a winding signal to the film winding circuit 22. ,
The exposure operation ends. Next, after resetting the exposure permission flag and setting the single completion flag, the process returns to the top flow.

The AF processing of the subroutine will be explained with reference to the flowchart of FIG. First, it is determined whether the exposure permission flag is set. When the exposure permission flag is set, it indicates that the focus adjustment to the -degree position has already been completed, so there is no need for further focus adjustment, and the process returns.

Since this flag is not reset unless the first stage of the release switch is turned off, focus adjustment is not performed until the user releases the release switch and presses it again. Next, a timer in the microcomputer 15 is started. This timer is used to measure integration time. Next, a command to start integration is output to the interface circuit 14. Then the interface circuit 14
resets the charge accumulated in the gate of 5IPT that constitutes the sensor and starts integration.

Next, it is determined whether the auxiliary light flag is set. This flag is set during the integral prediction subroutine described later. And the release switch 25 is set to O.
Since it is always reset when the FF is in effect, this flag is not yet set when AF single is called for the first time after the first step of the release switch 25 is turned on. Therefore, there is no branching to the light projection start process at the first integration. The reason why this flag is determined here is that if it is determined that it is necessary to turn on the -degree auxiliary light, in the second and subsequent integrations, the integral prediction process is stopped and the auxiliary light is emitted from the beginning.

As a result, the time required for the integral molecule 7IllJ can be used as an effective integration time, leading to a reduction in the integration time.

When the auxiliary light flag is not set, the microcomputer 15 waits for an integration end signal from the interface 14 and continues to monitor whether the timer reaches Tφ. Normally, the integration ends before the timer reaches Tφ, and the microcomputer 15 inputs the A/D converted digital data of the sensor from the interface circuit 14. Then stop the timer. Then, the amount of focus shift is calculated using the obtained data and the evaluation formulas (1) and (2) described above. Next, a determination of focus is made. Here, the amount of deviation obtained is F number / 30 [
It is determined whether the circle of confusion is within the circle of least confusion shown in mm). When it is determined that the focus is in focus, the exposure permission flag and single completion flag 1 are set, and after the focus is displayed, the A
Return from processing of F resin. When it is determined that the camera is out of focus, the exposure permission flag and the single completion flag 1 are reset, an out-of-focus display is displayed, the lens is driven based on the amount of deviation, and the process returns from the AF focusing process. Regarding the single completion flag 1, please refer to the AF
Used in servo processing.

Next, a description will be given of processing when the integration end signal is not output from the interface circuit 14 even when the timer reaches Tφ. The processing described below is an important point of this invention.

The microcomputer 15 is an interface circuit 1
A read command is output to 4. Then, the interface circuit 14 reads out the data of 5IPT during the integration without destroying it, as previously explained in the sensor reading method. After A/D conversion, the data is input to the microcomputer 15. Next, the integral prediction subroutine is called. Integral prediction will be explained with reference to the flowchart in FIG. First, the maximum value (D
MAX) and minimum value (DMIN) are detected. Integral time Tφ and maximum value D MA when this data is read next
The time required to complete the integration is calculated from X using the following equation.

The numerator value 255 indicates the maximum value of data output from the interface circuit 14 when the integration normally ends when an 8-bit A/D converter is used. Next, the integration time T1 pre-11-1 is the maximum integration time T W
It is determined whether it is larger than AX. When it is determined that the brightness of the subject is large, it is necessary to increase the subject brightness by using fill light, so the fill light flag is set (-1). and return. The maximum integration time T MAX is a value determined by taking into account the maximum integration time of 5IPT that does not cause any practical problems and the maximum integration time allowed in the camera sequence. When it is determined that TI is smaller than T MAX, contrast is predicted. The contrast of the image formed on the sensor at this moment is (DMAX - DMI
N)/(DMAX+DHIN). Therefore, the contrast C at the end of the integration is 2
It can be predicted that the current contrast is multiplied by 55/DMAX. When this contrast is determined to be smaller than the minimum contrast CMIN required for detecting the amount of defocus, even if the subject brightness is sufficient, it is necessary to increase the contrast of the subject using fill light.
The auxiliary light flag is set (-1). If the predetermined integration time is less than the specified value and the contrast is greater than or equal to the specified value, if the integration is continued as is, appropriate data can be obtained. Therefore, the auxiliary light flag is reset (-
φ) and return. Returning to the flow shown in FIG. 7, when returning from the integral prediction subroutine, it is determined whether the auxiliary light flag is set. When the flag is set, the microcomputer 5 sends a light signal to the light emitting circuit 16, and light emission starts. Next, the interface circuit 14
It is monitored whether a signal indicating the end of integration is output from the timer, and whether the timer reaches TMAX indicating the maximum integration time is monitored. When the integration end signal is output, data is input, and when the timer reaches T MAX, a read command is output to the interface circuit 14, and the integration is completed by inputting the data during the integration. shall be.

Next, if the auxiliary light is being used, a light projection stop signal is sent to the light emitting circuit 16, and furthermore, the operation of the timer is stopped.

After this, the process already described is executed and the process returns from the AF recording process.

The AF servo processing will be explained based on the flowchart of FIG.

First, it is determined whether the single completion flag 1 is set. The single completion flag 1 is set when focus adjustment is performed to the in-focus point in the AF single mode. If the flag is not set, the process branches to the AF processing shown in FIG. Due to this branching, the same operation as the AF lens is performed until -degree focusing is achieved. Such processing is performed to reduce the number of times the auxiliary light is projected.

If an attempt is made to execute the AF servo operation by repeating the AF processing, in the case of low luminance, auxiliary light will be emitted every time integration is performed, giving the user a feeling of freshness. When single completion flag 1 is set,
Since control of the auxiliary light is not required, normal integration without integral prediction processing is performed. The amount of deviation is calculated using the data obtained by this integration. When in focus,
The exposure permission flag is set, the focus is displayed, and the process returns from the AF servo. When it is not in focus, the exposure permission flag is reset, an out-of-focus display is performed, the lens is driven, and then the process returns.

The manual mode will be explained based on the flowchart in FIG.

First, an exposure permission flag is set. The reason why the exposure permission flag is set regardless of whether the camera is in focus or out of focus is that whether or not to execute an exposure sequence in manual mode is determined solely by the user's will and is not affected by the results of focus detection. . Therefore, the focus detection results are used only for display purposes. After starting the timer and outputting an integration start command, the microcomputer 15 monitors the presence or absence of an integration end signal and whether or not the timer has reached the maximum integration time TMAX, and then switches the release switch to the second stage. It also determines whether or not the button has been pressed. The reason for monitoring the release switch during integration is to shorten the time it takes to move on to the exposure sequence and allow the user to perform exposure at his/her convenience. When the release switch is turned on, stop the timer and return. Furthermore, since it is unnecessary to project the auxiliary light in the manual mode, the integral prediction process necessary for controlling the auxiliary light is not executed. When the integration is finished and the data input is finished, the microcomputer 1
Step 5 stops the timer, calculates the amount of deviation, displays in-focus or out-of-focus based on the calculation result, and then returns.

Second Embodiment In the first embodiment, an example was shown in which an SIT image sensor was used as a focus detection sensor. In the second embodiment, C
An example using a CD linear image sensor will be shown. 11th
The configuration of the CCD linear image sensor 40 will be explained with reference to the drawings.

The monitor photodiode is a photodiode for controlling the accumulation time of signal charges generated in the photodiode array, and charges exceeding the potential applied to the monitor barrier gate are accumulated in the diffusion layer of the gate of the MOS transistor Q1.

MOS) transistors Q1 to Q4 constitute a two-stage source follower amplifier, and the source output of Q3 is the monitor output signal M.
It becomes O3. The MOS transistor Q5 is provided to reset the accumulated charge of the monitor photodiode to the drain voltage VDD of the MOS transistor Q5 before starting integration, and the monitor reset signal MφR of the MO3I-transistor Q5 is connected to the interface circuit like the overflow gate signal OFG. 14.

The photodiode array is a photoelectric conversion element array composed of, for example, 128 photoelectric conversion elements arranged in a straight line. Charges generated in proportion to the light intensity on the pixel formed by the photoelectric conversion element and exceeding the potential applied to the barrier gate are accumulated in the storage gate. When the amount of charge generated in the monitor photodiode reaches a predetermined level, the transfer gate opens and the signal charge is transferred to the CCD shift register. The diode DI connected to the transfer output terminal of the CCD shift register is a floating diffusion output diode, MO.
The S transistor QIO is used to periodically reset the floating diffusion, and is controlled by the output signal φR from the CCD driver. The MOS transistors Q6 to Q9 constitute a two-stage source follower amplifier, and the signal charge O8 of each pixel is taken out from the source of the MOS transistor Q8. This signal charge O8 is digitally encoded by the A/D converter of the interface circuit 14 and output to the microcomputer 15.

In the various signals shown in FIG. 11, MBA is a signal that controls the monitor barrier gate, BA is a signal that controls the rear gate, OFD is a signal that controls the overflow drain below the storage gate, OFG is the overflow gate signal, ST is a signal that controls the storage gate, TR is a transfer gate pulse that controls the transfer gate, φ■φ
2 indicates a transfer lock pulse given to the CCD shift register.

Conventionally, the accumulation time of the photoelectric conversion element array is controlled by an interface circuit monitoring the MOS output.
This was done by reading out the signal charge when the output reached half the dynamic range of the A/D converter. Therefore, after issuing an integration start signal to the interface circuit, the microcomputer merely waits for the digitally encoded signal charge data to be output, without monitoring the MOS output. However, if it is read out during the MOS output integration, the integration time can be predicted in the same way as when using an SIT image sensor. In the first embodiment, when a CCD image sensor is used instead of the SIT image sensor, the operation of the microcomputer in which the processing is different will be explained with reference to the flowcharts of FIGS. 12 and 13.

The flowchart in FIG. 12 corresponds to the AF in FIG. 7 of the first embodiment.
Equivalent to Lesinru. The difference from FIG. 7 is that when the timer reaches Tφ before the integration end signal is output, the microcomputer 15
4, this part outputs a monitor read command and inputs monitor data obtained by A/D converting the MOS output.

After inputting the monitor data, the integral prediction subroutine is called. FIG. 13 shows this flowchart. FIG. 13 corresponds to the flowchart of FIG. 10 of the first embodiment. The predicted integration time TI can be calculated by multiplying the integration time Tφ when the monitor output is read by 130/monitor output. The numerator 130 is 8 bi
The dynamic range of Soto's A/D converter is 25
5, which is approximately half of this value. The reason for setting it to half is that since the monitor photodiode is a single element with approximately the same size as the photoelectric conversion element array, its output approximately represents the average value of the element array. The predicted integration time TI is the maximum integration time T MA
When it is larger than X, there is a need for auxiliary light, so the auxiliary light flag is set, and when it is smaller, it is reset and then returns.

When using a SIT image sensor, data for each element can be read out, so it is possible to predict the contrast, but only the average value can be obtained from the monitor output.
Contrast cannot be predicted. This point differs from the first embodiment.

(Effects of the Invention) As described above, by non-destructively reading out the sensor, it is possible to eliminate unnecessary integration operations when the subject brightness is low, and the time required for focus adjustment can be shortened.

[Brief explanation of the drawing]

Fig. 1 is a block circuit diagram showing an outline of the present invention, Fig. 2 is a block circuit diagram of an autofocus camera according to an embodiment of the invention, and Fig. 3 shows a line sensor used in the camera of Fig. 2. , (a) shows the configuration of the line sensor, (
b) is a diagram showing the equivalent circuit of the line sensor, Figure 4 shows the 5IPT that constitutes the line sensor, and (a) is the diagram showing the 5IPT
The structure of the PT is shown, (b) is a diagram showing the operating state of the 5IPT, FIG. 5 is a diagram showing the process of calculating the amount of focus shift, and FIG.
Figure 7 is a flowchart showing the overall operation of the autofocus camera of the present invention, Figure 7 is a flowchart showing the operation in AF focus mode, Figure 8 is a flowchart showing the operation in AF servo mode, and Figure 9 is a manual FIG. 10 is a flowchart showing the operation of the mode, FIG. 10 is a flowchart showing the operation of performing integral measurement, FIG. 11 is a diagram showing the configuration of a CCD linear image sensor used in another embodiment of the invention, and FIG. FIG. 13 is a flowchart for explaining the operation of the main parts of the second embodiment. FIG. 14 is a flowchart for explaining the operation of integral measurement according to the second embodiment. FIG. 3 is a flowchart diagram showing the operation. DESCRIPTION OF SYMBOLS 1... Subject, 2... Optical system, 3... Focus detection means, 4... Control means, 5... Filling light means, 11...
- Photographing lens, 12... Division optical system, 13... Line sensor 14... Interface circuit, 15...
・Microcomputer, 16... Light emitting circuit, 17・
...Auxiliary light source, 19...Shutter control circuit, 20.
...Aperture control circuit, 21...Photometering processing circuit, 24...
・Motor drive circuit, 25...Release switch, 26
...Mode setting switch. Figure 1 Applicant's agent Patent attorney Jun Tsuboi Figure 8 Figure 10 Figure 9 Figure 1 Figure 13 Figure 14

Claims (2)

[Claims] (1) In an autofocus camera equipped with an auxiliary illumination device, a focus detection means constituted by a photoelectric conversion element having a non-destructive readout function, and an auxiliary light means for projecting light to improve the brightness of the subject. , an auxiliary light control means for controlling the auxiliary light means based on the output of the photoelectric conversion element, and the auxiliary light control means performs non-destructive readout from the photoelectric conversion element before the integration operation is completed. The automatic focusing system is characterized in that the brightness of the subject is predicted from the data read out by the data and the integration time at the time of reading this data, and when the predicted brightness is below a specified value, the auxiliary light means emits light onto the subject. expression camera. (2) In an autofocus camera equipped with an auxiliary illumination device, a photoelectric conversion element and a focus detection means having a monitoring means for monitoring the state of charge accumulation in the photoelectric conversion element, and a light emitting device for improving the brightness of the subject. and an auxiliary light control means for controlling the auxiliary light means based on the output of the monitor means, and the auxiliary light control means controls the auxiliary light when the integral operation of the photoelectric conversion element is completed. Before shooting, the brightness of the subject is predicted based on the data input from the monitor means and the integral time at the time this data is read out, and when the predicted brightness is judged to be below a specified value, the auxiliary light unit projects light onto the subject. An autofocus camera that is characterized by a light source.