JP3238546B2 - Photoelectric conversion device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device for optimally controlling signal accumulation and signal processing of a focus detection device used for a camera or the like.

[0002]

2. Description of the Related Art Conventionally, various techniques for storing photoelectrically converted signals of a focus detection device have been proposed. For example, Japanese Patent Application Laid-Open No. 63-246710 discloses a technique of controlling the switching between the accumulation time and the signal amplification factor after the start of the focus detection operation. In this technique, the accumulation level of the accumulation monitor output is compared with a predetermined level after a predetermined time from the start of accumulation, and the accumulation time and the amplification factor are determined based on the magnitude relation at that time. Therefore, the accumulation time can be efficiently controlled according to the brightness of the subject.

FIG. 12 is a block diagram showing a configuration of a conventional photoelectric conversion device. As shown in FIG. 12, the configuration of the amplification factor control circuit 102 includes an accumulation time monitor control unit, and the amplification factor is determined according to the monitor characteristics. Then, the monitor signal MOS ₁ from the CCD image sensor 101 is compared with the comparators 104 and _1.
When input to 06, the comparators 104 and 106 compare the magnitude of the monitor output with respect to the voltage generated by the reference voltage generation circuits 103 and 105, respectively.

[0004] Here, the judgment results of the comparators 104 and 106 are based on the flip-flop 107 and the switches SW ₁ and SW.
Is determined whether amplified by the selection circuit consisting of _2, SW ₃ and SW _4. The switch SW ₁ through switching of the amplification factor by selecting the SW ₄ is flip-flop 107
Clock terminal. Then, the timing signal T ₁ generated from the accumulation start after a predetermined time, determined from the output of the comparator 106 of the time, its characteristics may vary depending on the brightness of the accumulation monitor output or focus detection subject. Based on the amplification factor thus selected, the output signal O of the sensor is obtained.
S ₁ is output to the CPU (not shown) is amplified.

[0005]

However, in the above-mentioned prior art, although the accumulation control can be performed efficiently, there is a problem that the scale of the control circuit becomes large. That is,
A control circuit having a scale as shown in FIG. 12 is required. In addition, the setting of the accumulation end level requires a margin of variation in advance, or requires an adjustment unit such as D / A conversion, which further increases the load on peripheral circuits and complicates the system configuration.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a photoelectric conversion device capable of reducing a circuit scale and optimally controlling signal accumulation of a sensor. .

[0007]

In order to achieve the above object, a photoelectric conversion device according to a first aspect of the present invention comprises a photoelectric conversion means for receiving a light beam from a subject and accumulating electric charges corresponding to the amount of received light. And monitor signal generating means for generating a monitor signal according to the amount of received light during charge accumulation of the photoelectric conversion means,
An accumulation ending time estimating means for estimating an accumulation ending time based on an output of the monitor signal generating means at an early stage of charge accumulation of the photoelectric conversion means; and an accumulation controlling means ending the accumulation based on the accumulation ending time. It is characterized by doing. The photoelectric conversion device according to the second aspect is a photoelectric conversion device according to the first aspect.
In the above, the above prediction is based on the start of charge accumulation of the photoelectric conversion means.
Time and the output of the monitor signal generator at that time
It is characterized by being performed on the basis of. The photoelectric conversion device according to a third aspect is characterized in that, in the second aspect, the output of the monitor signal generation means performs the prediction as a linear function of the charge accumulation time. The photoelectric conversion device according to a fourth aspect is the photoelectric conversion device according to the first aspect, further comprising: a photometer for receiving a light beam from the subject and obtaining an output according to brightness; Sensitivity of the photoelectric conversion means based on the output of the photometric means ,
The gain of the photoelectric conversion means and the monitor signal generation means
Determine at least one of the conditions for the read time, and
The storage end time of the photoelectric conversion means is predicted based on the output of the monitor signal generation means under the above condition . A photoelectric conversion device according to a fifth aspect includes a photoelectric conversion unit that receives a light beam from a subject and accumulates an electric charge according to the amount of light received, and a photoelectric conversion unit that receives the light beam from the subject and obtains an output according to brightness. Photometry means and charge of the photoelectric conversion means
Monitor signal that generates a monitor signal according to the amount of received light during accumulation
No. generating means and read time of the monitor signal generating means
Is determined based on the output of the photometric unit, and the accumulation end time estimating unit for estimating the accumulation end time based on the output of the monitor signal generating unit in the early stage of charge accumulation of the photoelectric conversion unit; Storage control means for ending storage based on the storage end time.

[0008]

[0009]

[0010]

That is, in the photoelectric conversion device according to the first aspect of the present invention, the light beam from the object is received by the photoelectric conversion means, and the electric charge corresponding to the amount of received light is accumulated. During the charge accumulation, a monitor signal corresponding to the amount of received light is generated, and the accumulation end time is estimated by the accumulation end time estimating means based on the output of the monitor signal generating means at the beginning of the charge accumulation of the photoelectric conversion means.
The accumulation is terminated by the accumulation control means based on the accumulation end time. In the photoelectric conversion device according to the second aspect, in the first aspect, the prediction is performed based on a time from the start of charge accumulation of the photoelectric conversion unit and an output of the monitor signal generation unit at that time. Further, in the photoelectric conversion device according to the third aspect, in the second aspect,
The prediction is performed on the output of the monitor signal generating means as a linear function of the charge accumulation time. Further, in the photoelectric conversion device according to a fourth aspect, in the first aspect, the light flux from the subject is received by the photometry means and an output corresponding to the brightness is obtained.
Based on the output of the photometric means, the sensitivity of the photoelectric
Degree, the gain of the photoelectric conversion means, the monitor signal generation means
The stage determines at least one of the read time conditions.
Based on the output of the monitor signal generation means
Then, the accumulation end time of the photoelectric conversion means is predicted.
Then, in the photoelectric conversion device according to the fifth aspect, the light beam from the subject is received by the photoelectric conversion means, the electric charge according to the amount of light received is accumulated, and the light beam from the subject is received by the photometry means, and the brightness is determined according to the brightness. Output and monitor signal
The amount of light received during the charge accumulation of the photoelectric conversion means
A monitor signal is generated according to the
The reading time of the monitor signal generating means is shorter than the photometry.
Is determined based on the output of the photoelectric conversion means.
The output of the monitor signal generating means at the beginning of load accumulation
The accumulation end time is predicted based on the accumulation end time, and the accumulation is ended by the accumulation control means based on the accumulation end time.

[0011]

[0012]

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a diagram illustrating a configuration of a camera using a photoelectric conversion device according to a first embodiment of the present invention.
As shown in FIG. 1, subject light guided through the interchangeable photographing lens 1 is reflected by the half mirror 2 and guided to the AF module 3.

This AF module 3 is described in detail in FIG.
As shown in FIG. 2B, the shift amount of the two images obtained from the light beams passing through the different pupils of the photographing lens 1 is relatively shifted from the in-focus position, which is constituted by a detection system generally called a phase difference method. Is to be detected. Furthermore, this AF
The light beam guided to the module 3 is reflected by a mirror in the AF module 3 and guided to a photometric sensor 4 and a distance measuring sensor 5. Each light beam is restricted by the optical member so as to be a light beam having an opening of a required size. Further, at the time of focus detection, the photographic lens 1 is driven to move to a focus position based on the result obtained by processing the output of the distance measuring sensor 5.

The detailed structure of the distance measuring sensor 5 is as shown in FIG. As shown in FIG.
The light flux guided by the F optical system enters the light receiving units 6 and 7 of the sensor. This sensor operation is performed by the light receiving units 6, 7
, The light receiving units 6 and 7 accumulate charges corresponding to the amount of incident light. Further, the charge storage amount of this sensor is externally monitored by a monitor output signal MON for detecting the peak value of the pixel, and the charge of each pixel stored for a predetermined time is simultaneously held in the storage unit by the signal ΦT. Then, the held signals are sequentially read out by the shift register 8 according to the readout signal φST. Further, an amplifier for amplification is connected to the output section, and A / A
The signal OS amplified to the D conversion level is output. still,
The light receiving section has an opening divided into two, and each opening is one to eight.
And the sensitivity is also equivalent to the area ratio.
The sensitivity of the light receiving section can be set by setting the level of the SEL terminal to "1".

As shown in FIG. 2, the sensor control circuit is roughly divided into a control section 9, a monitor section 10, a light receiving section 11, a reading section 12, a shift register section 13, an output amplifying section 14, and an output section 15. You. The communication with the CPU 16 is performed through five input terminals and one output terminal. Here, connection of the power supply system is omitted.

Hereinafter, control of the CPU 16 will be described. Among the input terminals, the DCK and CODE terminals are dedicated terminals for inputting 4-bit serial data. Data input from the CODE terminal is set in the decoder of the control unit at the rising timing of the DCK terminal to control each operation. It is assumed that the command input here is allowed to be controlled at a relatively slow speed. Specifically, a reset command, light receiving unit sensitivity switching, and amplification factor sets (× 1, ××) of the amplifier are set.
2, × 4, × 8). In addition, a test function or the like can be performed.

Subsequently, the main operation is as shown in FIG. That is, when relatively slow control is possible, many commands can be input. Note that ΦSIG, ΦMON and RC
Each terminal of K is a terminal for supplying the reading of the monitor output, the input of the accumulation termination command, and the transfer clock of the shift register in combination.

Here, as shown in FIG.
Monitor lead when MON _bar · RCK) = 1 ( _bar indicates negative logic), end of accumulation when (ΦSIG _bar · ΦMON · RCK) = 1, and signal from RCK terminal when (ΦSIG _bar · ΦMON) = 1 The circuit is configured so that signal data is read out in synchronization with the circuit. Further, since a time delay directly affects the signal level between the monitor reading and the accumulation ending operation, the monitor reading and the accumulation ending operation can be set only by decoding so that a command can be directly input.

Hereinafter, the operation inside the sensor will be described. The monitor unit 10 is for monitoring the amount of light received by the sensor,
Initialized at the same time as the start of storage. Thereafter, the output of the monitor unit 10 increases according to the amount of received light. And CPU1
When the monitor read command is issued from 6, the control section 9 immediately generates a sample-and-hold signal .phi.SHM to the monitor section 10 by the combinational circuit. At this time, the output section 15 has MOSEL = "1", and the monitor output is selected. Therefore, the CPU 16 can know the accumulated amount by A / D converting the output voltage from the OUT terminal.

The light receiving section 11 receives the light beam guided by the optical system, and performs photoelectric conversion of the subject image. In response to an accumulation start command, signals ΦR and ΦT are output from the control section, and the light receiving section 11 Initialized. At this time, the sensitivity of the light receiving unit 11 can be set externally from the SEL terminal. Further, when there is no external input, switching is automatically performed internally according to the brightness. In the case of the present embodiment, the light receiving section 11 is constituted by a MOS amplification type photodiode. Then, after the electric charge accumulated in the light receiving section 11 is accumulated by a predetermined amount, a signal φSHS is generated to the reading section in response to a reading command from the CPU 16.

The reading section 12 simultaneously holds the accumulation signals of the respective pixels. Further, the reading unit 12 sequentially reads out signals from the shift register 13 to the output unit 15. Then, the shift register 13 outputs the signal CK
1 and CK2, and when a pulse ΦST is input, a transfer operation is started.

The accumulated signal is sampled and held in synchronization with the sample and hold pulse output from the control unit 9, and after subtracting the dark output from the signal, the CP is output prior to the read signal.
The signal is amplified by the amplification factor set to the amplification factor set by U16, and sent to the output unit 15. At this time, MOSEL
= “0”, and the signal side is selected as the output. And
The signal output from the OUT terminal is A / D-converted by the CPU 16 and used as a distance measurement signal in the calculation. Since the above operations can be set independently by data communication from the CPU 16, the configurations of the control unit 9 and each of the waveform generation units can be composed of relatively small-scale circuits.
Further, various combinations of operations can be easily performed by software. The switching of the monitor and the signal output, the timing of the sample hold, and the like obviously occur with each operation, so that they are set at the same time as each command.

The operation of this embodiment will be described below with reference to the flowchart of FIG. After starting counting by the timer (step S1), the CPU 16 outputs a reset signal .PHI.R to the sensor to start the accumulation operation (step S2). The time t1 from the start of the accumulation
Later (step S3), the CPU 16 performs A / D conversion of the monitor output for reading the monitor output (step S3).
4). The monitor output from this sensor is
It is designed so that the output characteristics match the D conversion level. Then, the CPU 16 determines the signal accumulation end time from the A / D result of the monitor output. Furthermore, since the output characteristics of the monitor output and the signal output level vary depending on the module, the sensor output is irradiated with uniform sensor light when adjusting the sensor output, and the signal output is obtained from the relationship between the A / D conversion result of the monitor output and the signal output at that time. The A / D conversion value of the monitor output when is at the appropriate level is obtained and stored in advance in an EEPROM or the like. The CPU 16 sets the accumulation end time with the stored value as a target.

If the sensor output is to be amplified at a plurality of amplification factors, if the above-mentioned A / D conversion value or its substitute characteristic value is provided for each of the amplification factors, the accuracy can be improved regardless of the switching of the amplification factor. Can be controlled. At this time, when the sensor output is amplified with a plurality of amplification factors, the above-described A is used for each amplification factor.
It is preferable to have a / D conversion value or a value of its substitute characteristic.

Further, when the monitor A / D value is saturated, for example, when "255" is output in the case of 8 bits, the accurate accumulation level is not known, so the target value of the monitor end time is changed. To perform the accumulation operation again (step S5). Conversely, when the monitor does not reach the predetermined value, that is, when the subject is relatively dark, it is difficult to determine the storage time, so the monitor output is read again after the second predetermined time t1 '(steps S6 and S7).

After the calculation of t2, the CPU 16 outputs a signal transfer pulse ΦT to the sensor when the set time t2 has come (steps S8, S9, S10).
As described above, the setting of the read time t2 can be obtained by calculation. That is, when the monitor output is obtained with the characteristics shown in FIG. 5 after the start of accumulation, the A / D conversion value V1 of the monitor output at time t1, the offset value V0 of the monitor output stored in the EEPROM, and the target value V2 Assuming that the monitor output is a linear function, the time t2 can be calculated as t2 = (V2-V0) / (V1-V0) .t1. Here, V2 is a target value when the amplification factor is "1", and a value suitable for the amplification factor selected based on the value of V1 is selected. The CPU 16 sets a timer at time t2 based on the above calculation result.

Thus, the read pulse ΦST is sent to the sensor, and the stored signals are sequentially read. The read signal is sampled and held at the timing of the signal φSH and A / D converted (step S11). The sensor accumulation operation for distance measurement is controlled by the above sequence.

Next, in FIG. 7, the monitor accumulation time is determined not by the signal from the CPU 16 but in the sensor as in the first embodiment, and the output of the sample / hold signal is also performed in the same chip. FIG. 6 is a diagram showing a second embodiment of the configuration.

As shown in FIG.
Simultaneously with the occurrence of R, the sample and hold signal .phi.SHM goes to a high level "H" and enters a sample state. After that, a constant current flows from the terminal EEout of the constant current characteristic after the start of accumulation,
When a predetermined amount of accumulation is performed, the sample and hold pulse Φ
SHM is inverted to low level “L”, and the device enters the hold state. In FIG. 8, the monitor output is A / D converted. However, an amplification rate switching unit is provided at the output stage of the monitor to amplify the monitor output when the monitor level is too low when the subject is relatively dark. Alternatively, the determination of the storage time may be made relatively early.

Next, a control example of the accumulation operation when the CPU 16 executes another sequence after the start of distance measurement will be described. FIG. 8 is a flowchart showing the operation of the CPU 16 in the second embodiment.

When the distance measurement operation is started, the CPU 16
After setting the output of the L terminal to "0" to set it to the high sensitivity side (step S20), the photometric value EV is read (step S21). Subsequently, it is determined whether or not the photometric value EV is greater than a value EV0 indicating the brightness stored at the time of adjustment. This determination is made by a method described later (step S2).
2). Then, when the above condition is satisfied, the CPU 16 sets the terminal SEL to “1”. At this time, the sensor has a substantially smaller aperture of the light receiving section and the sensitivity is reduced. Then, under other conditions, the output of the SEL terminal is set to “0”. At this time, the aperture of the light receiving section becomes large (step S2).
3).

Subsequently, after starting counting by the timer (step S24), the CPU 16 outputs a reset signal ΦR to the sensor and starts the accumulation operation of the sensor (step S25). Thereafter, the CPU 16 executes another sequence for a certain period of time, here from the start of accumulation to tcpu (step S26). Then, after tcpu, the monitor output is A / D converted. When the monitor output itself reaches the storage time determined from the photometric value, the CPU 16 samples and outputs the sampled data.
By outputting a hold pulse to the sensor, the monitor output level at that time is held. There is no particular limitation on the output time of the sample and hold pulse (step S27).

At this time, if the A / D value is equal to or greater than "255", the operation returns to the step S24. At other times, the accumulation end time t2 is set from the A / D result,
After the elapse of the set time, a transfer pulse is output to the sensor. Then, a read pulse is output as described above (steps S28 to S32).

Although not shown, in this embodiment,
In particular, when the subject is bright, there is a case where accurate determination cannot be made with one A / D result. That is,
When the subject is bright, the amount of change in the monitor output during the A / D conversion time of the monitor is large. Therefore, if the reading time is slightly shifted, the output is saturated. In order to prevent this, when the subject is relatively bright, the monitor output is read out earlier in consideration of the error in the monitor output time. However, if the reading time is earlier than the monitor output, on the other hand, there is a disadvantage that the monitor output is too small. Therefore, in order to correctly determine the signal accumulation end time, the monitor output is A / D converted again after the monitor output A / D shown in FIG. 6 and the monitor output level is confirmed. In this way, the monitor output can be read a plurality of times.

Next, a control example of the second embodiment will be described with reference to FIGS. In this embodiment, the monitor holding time is determined from the photometric output. After the start of the accumulation, the CPU 16 performs other work until a predetermined time, so that it is difficult to control when the subject is bright. Therefore, as shown in FIG.
When the subject brightness is brighter than EV0, the sensitivity of the sensor light receiving unit is reduced. In this embodiment, the sensitivity is reduced to 1/8. Since the gain of the sensor output when the brightness is high is one, if the sensitivity is lowered, the storage time for the brightness is shifted by 3 EV and the storage end time is eight times late. The relationship between the monitor output and the accumulation time is as shown in FIG.

Hereinafter, this control example will be described in detail for each condition with reference to FIG. First, when EV ≧ EV1, when the sensor sensitivity is 1 / 8R and when the brightness of the subject is brighter than EV1, the monitor read pulse is tcp.
u Set to occur before. Under this condition, the subject is very bright, and the CPU 16 performs monitor reading prior to another sequence so that the response delay is not affected. This monitor output is sampled and held at time t1, and A / D converted in an A / D time of about 10 .mu.s.
The accumulation end time t2 is determined from the result, and the signal .PHI.t is generated. Further, the accumulation signal is read out after tcpu from the accumulation start. This reading time is several tens μs after the start of accumulation, and is not a time that is burdensome in the sequence.

When EV0 ≦ EV <EV1,
The sensor sensitivity is 1 / 8R and the brightness is such that it can be read out after tcpu. A monitor readout pulse is generated at the time determined from the photometric output, and the sample is held. This time is especially t
It is not limited to cpu, and the target level is the level when the gain is 1. After that, the value sampled and held after tcpu is read to determine the accumulation end time t2.

Further, when EV2 ≦ EV <EV0,
The sensor sensitivity is a brightness that can be read out after tcpu in R, and the control conditions are the same as when EV0 ≦ EV <EV1. When EV <EV2, the sensor sensitivity is R and the gain is 4 times. This is a case where the brightness of the subject is low, and the setting of the monitor read time is determined by １ ／ of the stored value. The conditions for this control are the same as when EV0 ≦ EV <EV1.

As described above in detail, in the present invention, the monitor output of the focus detection data is read from the photometric output, and the accumulation end time is determined based on the value. Therefore, the accumulation termination judgment voltage and the accumulation termination time setting counter are not required, and the accumulation time of the sensor can be controlled without reading out the signal data. This eliminates the need for an interrupt operation and allows flexible control.

Further, since the interrupt operation is not required and the control signal synchronization at the end of the accumulation can be set in advance, even in a system such as a CCD which needs to synchronize the clock at the time of signal transfer, there is no need for a special circuit. Flexible control is possible.

[0042]

According to the present invention, it is possible to provide a photoelectric conversion device capable of reducing the circuit scale and optimally controlling the signal accumulation of the sensor.

[Brief description of the drawings]

1A shows a configuration of a camera using a photoelectric conversion device according to a first embodiment of the present invention, FIG. 1B shows a detailed configuration of a module 3, and FIG. FIG. 3 is a diagram illustrating a detailed configuration of a sensor 5.

FIG. 2 is a block diagram illustrating a configuration of a sensor control circuit.

FIG. 3 is a diagram illustrating a detailed operation of the sensor control circuit.

FIG. 4 is a time chart illustrating a relationship between signals in the sensor control circuit.

FIG. 5 is a diagram for explaining setting of a read time t2.

FIG. 6 is a flowchart for explaining the operation of the photoelectric conversion device according to the first embodiment.

FIG. 7 is a diagram showing a second embodiment of the configuration in which the monitor accumulation time is determined in the sensor, and the output of the sample / hold signal is also performed in the same chip.

FIG. 8 is a flowchart illustrating an operation of a CPU 16 according to the second embodiment.

FIG. 9 is a diagram showing the relationship between subject brightness and accumulation time.

FIG. 10 is a diagram illustrating a relationship between a monitoring time and an accumulation time.

FIG. 11 is a diagram in which control examples of the second embodiment are summarized according to conditions.

FIG. 12 is a block diagram illustrating a configuration of a photoelectric conversion device according to a conventional example.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photographing lens 2 half mirror 3 AF module 4 photometric sensor 5 distance measuring sensor 6 7 light receiving unit 8 shift register 9 control unit 10 monitor unit 11 light receiving section, 12 reading section, 13 shift register, 14 output amplifying section, 15 output section, 16 CP
U.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B ^7/ 28-7/40 G01J 1/44

Claims (5)

(57) [Claims] 1. A photoelectric conversion means for receiving a light beam from a subject and accumulating electric charge according to the amount of received light, and a monitor signal generating means for generating a monitor signal according to the amount of received light during charge accumulation of the photoelectric conversion means. An accumulation end time estimating means for estimating an accumulation end time based on an output of the monitor signal generating means at an early stage of charge accumulation of the photoelectric conversion means; and an accumulation control means for ending accumulation based on the accumulation end time. A photoelectric conversion device, comprising: 2. The photoelectric conversion device according to claim 1, wherein the prediction is made based on a time from the start of charge accumulation of the photoelectric conversion unit and an output of the monitor signal generation unit at that time. 3. The photoelectric conversion device according to claim 2, wherein the output of the monitor signal generation means performs the prediction as a linear function of the charge accumulation time. 4. A photometric device for receiving a light beam from a subject and obtaining an output corresponding to brightness, wherein the accumulation end time predicting device is configured to generate an output based on the output of the photometric device.
The sensitivity of the photoelectric conversion means, the gain of the photoelectric conversion means,
At least the read time of the monitor signal generator
These conditions are determined, and the monitor signal is generated according to these conditions.
2. The photoelectric conversion device according to claim 1, wherein an accumulation end time of the photoelectric conversion unit is predicted based on an output of the generation unit. 5. A photoelectric conversion means for accumulating a charge according to the amount of light received by receiving a light beam from an object, a photometric means for obtaining an output corresponding to the brightness by receiving a light beam from an object, the Monitor according to the amount of received light during charge accumulation of photoelectric conversion means
A monitor signal generating means for generating a signal, and a reading time of the monitor signal generating means,
Determined based on the output, the accumulation end time predicting means for predicting the accumulation end time based on the output of said monitor signal generating means in the initial charge accumulation of the photoelectric conversion means, the accumulation based on the accumulation end time A photoelectric conversion device, comprising: storage control means for ending.