JPS6255350B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical sensor device, particularly a charge storage type optical sensor device, which has a function of accumulating electric charge corresponding to an integral amount of incident light and outputting this accumulated electric charge as a photoelectric conversion signal. The present invention relates to an imaging device capable of controlling charge accumulation time in a sensor device.

Today, this type of charge storage type optical sensor device includes a CCD (Charge coupled device) photo sensor, a BBD (Bucket Brigade Device) photo sensor, or a photo diode.
Charge storage type photo diode arrays, etc., which are combined with CCDs, are known;
Basically, it generates an electric charge in response to light, and
A photosensor section has a plurality of photosensor regions that accumulate generated charges by applying a photo gate voltage, and a photosensor section that accumulates generated charges by applying a photo-gate voltage. A charge transfer unit that captures accumulated charge and sequentially transfers the captured charge to an output unit in response to a transfer signal (transfer pulse), and is disposed between the charge transfer unit and the optical sensor unit. When a photo gate voltage is applied to the photosensor part while the photosensor part is exposed to light, a potential well is formed in each photosensor area. When each generated charge is accumulated in each potential well and a charge capture signal is applied to the shift gate section and charge transfer section,
Similarly, potential wells are formed such that the accumulated charge in each photosensor region is taken into each corresponding potential well in the charge transfer section through each corresponding potential well in the shift gate section, and subsequently into each corresponding potential well in the charge transfer section. When a transfer signal is applied to the charge transfer section, each charge is sequentially transferred to the output section, from which the charges accumulated in each photosensor area can be extracted in time series as photoelectric conversion signals. be.

In addition, in the case of the above-mentioned charge storage type photo diode array formed by combining a photo diode and a CCD, the above-mentioned photosensor section serves as a photo-receiving section that generates charge in response to light.・It consists of a diode coupled to a charge storage section provided near each photo diode to individually store the charge generated in each photo diode, and the photo gate voltage described above is A potential well is formed in each of the charge storage sections by applying a voltage to the charge storage section, the charge generated in each photo diode is accumulated in each potential well, and the accumulated charge in each charge storage section is taken into the charge transfer section. Therefore, the combination of one photo diode and one charge storage section corresponds to one photosensor area.

Now, in this type of charge storage optical sensor device, when a photo-gate voltage is applied to the optical sensor section, a potential well is formed in each optical sensor region, and the formation of this potential well is caused by the photo-gate voltage. This will continue as long as the voltage is applied, but the capacitance of each potential well formed in each photosensor region by applying this photo-gate voltage, that is, the charge storage capacity, is determined in advance. It's something that happened. Therefore, in actual use, for example, if the amount of charge generated in a certain photosensor region exceeds the storage capacity of that potential well, the excess charge exceeding the saturation level will flow out and diffuse. Therefore, if such a phenomenon (so-called blooming phenomenon) occurs when scanning an image using this kind of optical sensor device, it will not be possible to properly scan the image. You will no longer be able to gain confidence.

Therefore, when putting this type of photosensor device into practical use, it is very important to adjust the storage time of the generated charges in each photosensor region, that is, the charge storage time. That is, the amount of accumulated charge in each photosensor region is the integrated amount of incident light to each within this charge accumulation time, that is,
It corresponds to the "intensity of incident light" x "charge accumulation time". Therefore, if this charge accumulation time is appropriately controlled, the outflow of excess charge and
This means that the phenomenon of diffusion can be avoided.

In addition to this, the control of this charge accumulation time is
This is absolutely necessary in order to improve the S/N ratio of the photoelectric conversion output from the optical sensor device and to always obtain reliable output over a wide range of intensity changes in incident light.

The first thing that can be considered as a method of controlling this charge accumulation time is the capture cycle interval when charges accumulated in each photosensor region are captured into the charge transfer section through the shift gate section, that is, the shift gate section.
This is to control the time interval at which a charge capture signal is applied to the gate section and the charge transfer section. That is,
The charge accumulation time in each photosensor region is determined by the periodic interval at which the accumulated charge is taken into the charge transfer section. Therefore, if the periodic interval at which the accumulated charge is taken into the charge transfer section is changed, each This means that the charge accumulation time in the photosensor region changes. and,
A specific method for changing the cycle interval at which the charge accumulated in each optical sensor region is taken into the charge transfer section is, for example, by changing the frequency of the transfer signal that can be applied to the charge transfer section. or (i.e.
The generation interval of the charge capture signal that can be applied to the shift gate section and the charge transfer section is determined based on the relationship with the transfer signal that can be applied to the charge transfer section, and therefore, By changing the frequency of the transfer pulse that can be applied to this charge transfer section, the generation cycle interval of the charge capture signal will change.)
Alternatively, there is a method of changing the relationship with respect to the transfer signal when determining the generation period interval of the charge capture signal, that is, the count number of transfer pulses.

However, this method of controlling charge accumulation time has the following disadvantages. For example, when looking at the shortest controllable charge accumulation time obtained by such a control method, this is
It is impossible to make the number of optical sensor regions in the device, n, shorter than the value obtained by multiplying the adjustable maximum frequency of the transfer pulse by its period 1/f, that is, n/f. Therefore, if the intensity of the incident light is particularly high, there is a risk that the amount of charge generated in each optical sensor area may exceed its storage capacity. . Additionally, in such a control method, the frequency of the transfer pulse described above must be increased in order to obtain a shorter charge accumulation time, but in general, the clock pulse is generated. In this case, the higher the frequency, the more power consumption increases, and in that case, the charge transfer efficiency decreases. Therefore, the above method
In this respect as well, it is disadvantageous.

Apart from this, as a method of controlling the charge accumulation time, in order to ensure the accuracy of the underlying detection, for example, when reading the output from the optical sensor device, the peak of the output obtained at this time is - Compare the level against a predetermined voltage range, and if the peak level exceeds the upper limit of the voltage range, shorten the accumulation time;
The most common control method is to extend the voltage when it is below the lower limit so that the peak level of the output always remains within the above voltage range. However, in the case of such a control method, for example, the peak of the output of the optical sensor device obtained in a certain output readout
Even if the accumulation time is changed because the level is outside the predetermined voltage range above, it is not possible to actually obtain an output whose level is properly adjusted by changing the accumulation time. At least in the next output readout, and in the case where the output readout from the optical sensor device is constantly repeated without any interruption, the next time, that is, change in the accumulation time. The second
When the output is read out for the second time, in the end, with this type of control method, since the accumulation time cannot be controlled in real time, an incorrect output will inevitably occur when controlling the accumulation time. This means that the readout output of that time or the next time that follows it is completely wasted. Particularly in recent years, various attempts have been made to use optical sensor devices as light receiving units in automatic focus detection systems or ranging systems for optical equipment such as cameras, and Since the dynamic range of light handled by these devices is extremely wide, it is essential to control the storage time, but in such cases, problems with the control method described above arise. The point is that there is a risk of false detection due to the above-mentioned incorrect output, a change in system configuration to deal with this incorrect output, or the movement of the subject within the time required until the output is corrected. This obviously brings about inconveniences such as the fear of erroneous detection due to changes in brightness and the like.

The present invention has been made in view of the above-mentioned circumstances, and the present invention has been made in view of the above-mentioned disadvantages in the methods conventionally considered as methods for controlling charge accumulation time in charge accumulation type optical sensor devices. In particular, it is possible to control the storage time in real time, and the range of adjustable charge storage time is further expanded. The purpose of the present invention is to provide a new and more advantageous charge accumulation time control method that does not involve disadvantages such as a decrease in the amount of light. In an optical sensor device equipped with a sensor section,
After the start of charge accumulation in the optical sensor section, the amount of charge from the optical sensor section is determined by detecting whether the amount of accumulated charge in at least a part of the optical sensor section has reached a predetermined amount of charge. The present invention is based on the fact that the charge accumulation time in the optical sensor section is controlled by determining the time to take out the accumulated charges.

In addition, as a specific embodiment of the charge accumulation time control method according to the present invention, according to the embodiment described below, the charge accumulated in the optical sensor section is An excess charge discharge part is provided to limit the upper limit of the amount to the above-mentioned predetermined amount, and a detection means is provided to detect the presence or absence of charge flowing out through the charge discharge part, and based on the detection output of the detection means. An embodiment has been proposed in which the charge accumulation time in the optical sensor section is controlled by determining when to take out the accumulated charge from the optical sensor section. An optical sensor device with a structure in which a charge discharge section is attached is already well known as a so-called optical sensor device with an anti-blooming gate, and therefore, the method of the present invention applies to an optical sensor device with such a structure. This can be implemented very easily without requiring any basic modifications to the sensor device.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

First, FIG. 1 shows the cross-sectional structure of an example of an optical sensor device suitable for carrying out the method of the present invention, and the figure shows a two-phase transfer type CCD photo sensor as an example. . In the figure, 1 is, for example, a P-type Si substrate, and on the surface of the substrate 1, a SiO ₂ film 2 is formed by high-temperature oxidation. - The electrode 4 for the gate part and the electrode 5 for the charge transfer part are connected to the electrode 3 for the photo gate part, and the control electrode 6 for the excess charge discharge gate part is located on the opposite side of the electrode 4 for the shift gate part. , are formed by a method such as vapor phase growth of highly transparent polycrystalline Si or vacuum evaporation of Al. Further, the SiO ₂ film 2 near the control electrode 6 for the excess charge discharge gate portion is partially removed by a method such as photo etching, and corresponding to the removed portion, the SiO 2 film 2 is etched for the P-type Si type. An n ⁺ region (i.e., a P-N junction diode or less , referred to as a sink portion) 7 is formed. Note that 8 is an electrode of the sink section 7, and 9 is a light shielding layer formed to cover the other surfaces except for the photo-gate section electrode 3.

For an optical sensor device with such a configuration,
When a photo-gate voltage Vp is applied to the photo-gate electrode 3 through its input terminal 3a, a potential well is formed under the electrode as shown by the broken line in the figure, and therefore the light to the electrode 3 is reduced. Charges generated under the electrode due to the injection are accumulated in the potential well, and here, a predetermined voltage Vc is also applied to the control electrode 6 for the excess charge discharge gate section through its input terminal 6a. Then, a certain amount of potential well is formed under the electrode as shown by the broken line in the figure, and one barrier of the potential well formed under the photo-gate electrode 3 is formed. The height becomes lower, and therefore, among the charges accumulated at the bottom of the electrode 3, the excess charge exceeding the height of the potential barrier formed at the bottom of the control electrode 6 flows out over the barrier. However, as a result, the charge storage capacity under the electrode 3 is determined by the height h of the potential barrier formed under the control electrode 6. Generally, in order to prevent charge saturation (blooming) in the photo-gate section, when the voltage applied to the photo-gate section electrode 3 is, for example, about 5 to 8 V, the voltage applied to the control electrode 6 is set to about 5 to 8 V. For example, by setting the voltage to about 2 to 3 V, the height h of the barrier at the bottom of the electrode 6 can be set to about 8 to 300 volts, which is the depth of the potential well at the bottom of the electrode 3.
90%, and the level at which charges can be accumulated in the photo gate section is set to approximately 80 to 90% of its saturation level.

On the other hand, the excess charge that has flowed out over the barrier at the bottom of the control electrode 6 flows into the sink section 7, but as already mentioned, the sink section 7 is connected to the P-N
is formed as a junction diode and therefore
The charge flowing into the sink portion 7 is converted into a current and output through the electrode 8-terminal 8a.

Therefore, as an embodiment of the charge accumulation time control method according to the present invention, the current from the sink section 7 outputted through the terminal 8a is applied to the optical sensor device configured as described above. By detecting this, the timing of applying the shift gate pulse φs to the electrode 4 for the shift gate portion, that is, the timing of taking out the accumulated charge from the photo gate portion, is determined. A configuration in which the charge accumulation time in the photo gate section is controlled is possible.

Next, a specific example will be explained with reference to FIGS. 2 and 3. In FIG. 2, the optical sensor device is indicated generally at 10 and has a structure as described in FIG. That is, 1
1 is the optical sensor section, and the channel stopper 15
The sensor element P has a linear array of n sensor elements P separated from each other so that the accumulated charges do not mix with each other, and each sensor element P has a common photo array. -A storage well (potential well shown in the first diagram) is formed by applying a photo-gate voltage Vp to the gate electrode 3. Reference numeral 12 denotes a shift gate section for taking out the accumulated charge from each sensor element P in the optical sensor section 11, and the shift channel is divided by the channel stopper 15 corresponding to each sensor element P. has been done. The shift gate electrode 4 is formed commonly for each shift channel. 13 and 13' sequentially output charges taken in through the shift gate section 12 to the output section 1.
4, the transfer section electrode 5 is formed individually for each transfer element 13, 13', and the electrode 5 for the transfer element 13 is connected to the input terminal. The electrode 5 for the transfer element 13' is connected to the input terminal 5b, to which the transfer pulse φ ₁ (shown in FIG. 3 i) is applied. ₂ (shown in FIG. 3). As is well known, the output section 14 is composed of a preamplifier, a reset transistor, etc., and a transfer pulse _φ2 from the input terminal 5b is applied as a reset pulse to the reset transistor. 14a is a video signal output terminal of the output section 14. 16 is the optical sensor section 11
is an excess charge discharging gate section for taking in excess charge in each sensor element P into the sink section 7, and the intake channel is divided by the channel stopper 15 corresponding to each sensor element P. There is. In addition, the control electrode 6
is commonly formed for each intake channel.

Reference numeral 17 denotes an amplifier for converting into voltage and amplifying the output current from the sink section 7 outputted through the electrode 8 and the terminal 8a, and 18 denotes an amplifier that operates when the output voltage of the amplifier 17 reaches a predetermined level. - The trigger circuits 19 and 20 are monostable multivibrator circuits activated by the output pulses of the Schmitt trigger circuit 18, respectively. In addition, here, multi-vibrator circuit 1
Reference numeral 9 is configured to output a single pulse (shown in FIG. 3c) that rises in synchronization with the rise of the output pulse of the Schmitt trigger circuit 18 and has a pulse width t. Reference numeral 20 outputs a single pulse (shown in FIG. 3d) which rises after a predetermined time τ with respect to the rise of the output pulse of the Schmitt trigger circuit 18 and has a pulse width t' (≦t-τ). It is something that is being done. The output of the monostable multi-vibrator circuit 19 is connected to an npn transistor 21 for producing a shift gate pulse φs (shown in FIG. 3f) to be applied to the shift gate section 12.
The output of the monostable multi-vibrator circuit 20 is applied to the base of an npn transistor 22 for controlling the photo gate voltage Vp (shown in FIG. 3e) to be applied to the optical sensor section 11. granted to. Note that voltages Vcc2 and Vcc1 are applied to the collectors of the transistors 21 and 22, respectively. Reference numeral 23 indicates a reference pulse Φ which is a reference for creating the transfer pulse _φ1 for the charge transfer element 13.
₁ (shown in Figure 3, g) and the inverted signal from the inverter 24 of the output of the monostable multi-vibrator circuit 19, and its output (shown in Figure 3, h) is transferred. Pulse φ
It is attached to the base of the npn transistor 25 for producing ₁ . 26 is charge transfer element 1
The reference pulse Φ ₂ (shown in FIG. 3 j) which serves as a reference for creating the transfer pulse φ ₂ for 3' (in this case, the pulse Φ ₂ is an inverted pulse of the pulse Φ ₁ ) and the simple This is an OR gate for calculating the logical sum with the output of the stable multi-vibrator circuit 19, and its output (shown in FIG. 3k) is connected to the npn transistor ₂ for producing the transfer pulse φ2.
7 is attached to the base. Note that a voltage Vcc3 is applied to the collectors of the transistors 25 and 27.

In the above configuration, the photo gate voltage Vp (=Vcc1) is now applied to the electrode 3 of the optical sensor section 11 through the input terminal 3a, and the photo gate voltage Vp (=Vcc1) is applied to the control electrode 6 of the excess charge discharge gate section 16. Through the terminal 6a, the electrode 6 shown in FIG.
The barrier height h of the lower potential is the voltage Vp
Assuming that a voltage Vc is applied that is, for example, about 80 to 90% of the depth of the potential well formed at the bottom of the electrode 3, the sensor
When the storage capacity from the generated charges in any one of the elements P is exceeded, the excess charges at this time flow into the sink section 7 through the corresponding channel of the excess charge discharge gate section 16. As a result, a current corresponding to the charge flowing into the sink section 7 is output from the terminal 8a connected to the sink section 7, and this is caused by the amplifier 17 as shown in FIG.
After voltage conversion and amplification as shown in FIG. The trigger circuit 18 outputs a pulse as shown in FIG. 3b when the output voltage of the amplifier 17 reaches a predetermined level.
(The lower the operating voltage level of the trigger circuit 18 in this case, the better.) This triggers the monostable multi-vibrator circuits 19 and 20 to generate a single pulse as shown in FIG. 3c and d, respectively. It will start outputting. At this time, the transistor 21 is turned on corresponding to the output pulse of the multi-vibrator circuit 19, and thus, as shown in FIG.
Shift gate pulse φs (voltage
Vcc2) is generated and applied to the electrode 4 of the shift gate section 12 through the input terminal 4a. On the other hand, at this time, the output pulse of the multi-vibrator circuit 19 is transmitted to one input of the third vibrator circuit 19.
An inverter 24 is connected to the other input of the AND gate 23 receiving a reference pulse Φ ₁ as shown in FIG.
Therefore, at this time, the and
The output of the gate 23 becomes as shown in _FIG. The charge capture signal φ's is superimposed on the voltage Vcc3 as shown in FIG. 3i. Further, the output pulse of the multi-vibrator circuit 19 is passed through an OR gate 26 which receives a reference pulse _Φ2 at one input as shown in FIG. 3J.
Therefore, the output of the OR gate 26 at this time is as shown in FIG. 3k,
Since the transistor 27 is switched by the output of the OR gate 26, the transfer pulse φ ₂ (voltage Vcc3) applied to the transfer element 5' through the input terminal 5b is transferred as shown in FIG. The portion corresponding to the charge capture signal φ's in the pulse _φ1 is missing.
Thus, the accumulated charge in each sensor element P of the optical sensor section 11 is transferred to the transfer element 1 through each corresponding channel of the shift gate section 12.
After that, by applying transfer pulses φ ₂ and φ ₁ to the transfer elements 13' and 13, respectively, the output unit 14 sequentially passes through the transfer elements 13' and 13. The signal is then transferred to the point where it is converted into a current or voltage and output from the output terminal 14a. On the other hand, at this time, the shift gate pulse φs becomes low because the output pulse of the multi-vibrator circuit 19 falls after time t has elapsed from its rise, thereby causing the shift gate section 12 to turn off the gate. In order to reach this state, each sensor element P in the optical sensor section 11 starts accumulating charges again in accordance with each amount of incident light. After the start of this charge accumulation, the amount of accumulated charge in any one of the sensor elements P exceeds the storable capacity defined by the potential of the discharge gate section 16, and the excess charge is removed. When the charge flows into the sink section 7, a current corresponding to the current charge flowing into the sink section 7 is outputted again from the terminal 8a of the sink section 7, and the above-mentioned operation is thereby repeated again. Thus, after the start of charge accumulation in the optical sensor section 11, it is determined whether the amount of accumulated charge in at least a part of the optical sensor section 11 has reached a predetermined capacity defined by the discharge gate section 16. Based on this, the charge accumulation time in the optical sensor section 11 is controlled. Note that this charge accumulation time is the time interval T until the fall of the shift gate pulse φs, as shown in FIG. 3f.

In addition, the monostable multi-vibrator circuit 20 mentioned above
The output pulse is a photo signal for the optical sensor section 11.
The photo gate voltage Vp is applied to the base of the transistor 21 in order to control the gate voltage Vp, so that the photo gate voltage Vp is multi-multiple when the stored charge is extracted from the photosensor element P, as shown in FIG. 3e. Although it is temporarily cut off in response to the output pulse of the vibrator circuit 20, this is a consideration to improve the efficiency of extracting the charge from the photosensor element P. Furthermore, when taking charge from the sensor element P into the transfer element 13, if the transfer efficiency is taken into account, it is better to set Vcc1<Vcc2<Vcc3.

In the embodiment described above, all of the sensor elements in the optical sensor section 11 were targeted when detecting the outflow of excess charge.
This is a predetermined sensor in the optical sensor section 11.
It may also be limited to only elements. That is, for example, the present applicant filed a patent application in
In the distance detection method proposed in JP-A No. 53-85453 and JP-A No. 52-506 (JP-A No. 53-85454), two images of an object focused on the baseline distance optical system are Image signals for the two images are obtained by scanning using an optical sensor device, and in particular, the field of view for the reference image is different from the field of view for the reference image. For example,
According to the above embodiment, if a very bright object that is not included in the reference image field of view happens to be included in the reference image field of view, the charge accumulation time of the photosensor section at this time will be The field of view becomes extremely short due to the influence of the brightness of the object, and as a result, there is a fear that the level of the image signal for the reference image field of view will drop extremely and the accuracy of distance detection will no longer be fully guaranteed. To prevent such a situation, the sensor elements to be detected when detecting the outflow of excess charge should be limited to, for example, only the array of sensor elements corresponding to the image of the reference image field mentioned above. It's okay.

That is, FIG. 4 shows an embodiment suitable for such a case, in which the sink section 7 for detecting the outflow of excess charge is connected to a part of the sensor in the optical sensor section 11 as shown in the figure. A sink section 7' is provided corresponding only to the array of elements, while a sink section 7' exclusively for discharge is provided for the remaining array of sensor elements. In such a configuration, the optical sensor section 11 is affected by the outflow of excess charge in any one of the sensor elements corresponding to the sink section 7.
The overall charge accumulation time is controlled, while during this time any excess charge draining in any of the sensor elements corresponding to the sink 7' will cause the current to flow in the sink 7'. After being converted, it will be discharged through the electrode 8'-terminal 8'a.

On the other hand, in the embodiment described above, for example, the intensity of the light incident on the optical sensor section 11 is extremely low, and therefore the charge accumulated in the sensor element P is determined by the discharge gate section 16. If the upper limit of the storage capacity is not reached easily, it will take a long time to see the excess charge flowing out. In such cases, the accumulation time becomes abnormally long, and for example, in the case of a distance detection device such as the one described above, there is a risk that the object may move during this time, resulting in a large error in distance detection. There is a fear that this may occur. To prevent such a situation, the voltage applied to the control electrode 6 for the discharge gate section must be
By making Vc variable instead of fixed and increasing the voltage Vc, the electrode 6 explained in FIG.
By lowering the height h of the barrier at the lower potential of
Each sensor defined by the discharge gate section 16
The storable capacity of element P may be made small.

That is, FIG. 5 shows an embodiment suitable for such a case, in which the control voltage Vc to the control electrode 6 of the discharge gate section 16 is applied through the voltage switching circuit 28. For example, the voltage variable circuit 28 is configured to control the output pulse of the multi-vibrator circuit 20 and the reference pulse Φ
₁ , the time is counted, and the voltage Vc is applied to the discharge gate section 16 until a predetermined time elapses.
The storable capacity of each sensor element P defined by
A voltage that is relatively close (for example, 2~
3V), but after this predetermined time has elapsed, the output voltage is gradually increased. Therefore, within the above predetermined time, the sensor
If excess charge does not flow out from any of the elements P, after the predetermined period of time has elapsed, the accumulation in each sensor element P as determined by the discharge gate section 16 is reduced by increasing the control voltage Vc. The available capacitance became progressively smaller until we began to see excess charge draining from any of the sensor elements P, and thus in response to this excess charge draining,
As described above, the extraction and transfer of the accumulated charge from each sensor element P starts.

Incidentally, as the voltage variable circuit 28, for example, one having a configuration as shown in FIG. 6 can be applied. That is, in the figure, 29 is the reference pulse Φ ₁
The above monostable multi-counter is a counter that counts
It is configured to be reset by an output pulse from the vibrator circuit 19. 30 receives the outputs from _the output terminals Q _N -Q _X among the output terminals Q ₁ -Q 31 is an amplifier that receives the output of the D/A converter 30, and the output voltage of the amplifier 31 is used as the control voltage Vc for the control electrode 6 of the discharge gate section 16.
granted to.

In the configuration of such a voltage variable circuit, when a pulse is output from the multi-vibrator circuit 19 for extracting the accumulated charge from the sensor element P, the counter 29 is reset by this, and the output terminal of the multi-vibrator circuit 19 is reset. All outputs from Q ₁ to _Q
outputs a predetermined lowest voltage, and therefore, at this point, the control voltage applied to the discharge gate control electrode 6 through the amplifier 31 is at the lowest value. In this state, the counter 29 counts the reference pulse Φ ₁ , and until the counter 29 counts the reference pulse Φ ₁ a predetermined number of times, that is, the output from the output terminal Q _N of the counter 29 goes high. If excess charge begins to flow out from one of the sensor elements P before this occurs, a pulse is output from the multi-vibrator circuits 19 and 20 as described above, and the sensor element P outputs a pulse as described above. The accumulated charge is taken out, and the counter 29 is reset at this time. On the other hand, if no excess charge flows out from any of the sensor elements P during this time, the counter 29 is reset. Due to the high output from the output terminal _QN , the D/A converter 30 starts adding a predetermined small voltage to the above-mentioned minimum output, and therefore, at this point, the control voltage Vc output from the amplifier 31 The voltage value of will be raised slightly more than before. Even in this state, if excess charge does not flow out from any of the sensor elements P, then when the count of the counter 29 advances and the output from its output terminal Q _N+1 becomes high, the D/ The A converter 30 begins to add the above-mentioned minute voltage to the previous output voltage, and therefore, at this point, the control voltage Vc comes to be further increased. Thereafter, the output voltage from the D/A converter 30 increases in accordance with the change in the output from the output terminals Q _N to Q _X of the counter 29 until excess charge flows out from one of the sensor elements P. In order to do this, the control voltage Vc applied to the control electrode 6 of the discharge gate section 16 is gradually increased, and thus the storage capacity of each sensor element P defined by the discharge gate section 16 is gradually reduced. I feel like I'm being forced to go. If excess charge begins to flow out from one of the sensor elements P during the process of increasing the control voltage Vc, at this point a pulse is output from the multi-vibrator circuits 19 and 20 to each sensor as described above. - Taking out and transferring the accumulated charge from the element P starts, and the counter 29 is reset by the output pulse from the multi-vibrator circuit 19 at this time, so that its output terminal Q ₁ ~Q Since all outputs from _X become low, the output voltage from the D/A converter 30 returns to the lowest voltage.

In the configuration of the voltage variable circuit shown in FIG. 6, as described above, after a predetermined time has elapsed, the control voltage Vc applied to the discharge gate control electrode 6 is gradually increased at a predetermined rate of change. It is something that becomes. In addition, in this case, the above D/A converter 3
0 minimum output voltage and the output terminal Q of the counter 29
_The value of the weighted voltage for the change in output from _N to _Q When the voltage is about 8 V, the output voltage of the amplifier 31 should be about 2 to 3 V with respect to the lowest output voltage of the D/A converter 30, and the change in the count output (Q _N to Q _X ) of the counter 29 The weighted voltage from the amplifier 31 relative to the weighted voltage from the D/A converter 30 corresponding to the voltage may be selected between about 0.3 to 1 V depending on the rate of rise of the control voltage Vc, etc. be. Further, the timing to start increasing the control voltage Vc is appropriately determined based on the light receiving area of the sensor element P, the assumed incident intensity, the photo gate voltage V _P, and the like. Incidentally, in the configuration shown in FIG. 6, by appropriately selecting the terminal output of the counter 29 to be provided to the D/A converter 30, the timing and rate of increase of the control voltage Vc can be arbitrarily adjusted. It is possible.

Now, the above measures are taken against the situation that may occur when the intensity of the incident light on the optical sensor section 11 is extremely low, but on the other hand, for example, when the output reading from the optical sensor device is continuously repeated, In this case, the intensity of the incident light on the optical sensor section 11 becomes very high, and the controlled accumulation time T becomes the time required for one output readout, that is,
If the time required for the voltage taken out from the last sensor element to finish being transferred to the output part 14 through the transfer part after taking out the accumulated charge from each sensor element P is still There is a fear that the newly extracted signal charge will be mixed into the signal charge that is being transferred, resulting in a very inappropriate output signal.

Therefore, finally, with reference to FIG. 7, an embodiment will be described in which countermeasures against such a situation are taken into consideration.

In the figure, 32 is a counter that counts the reference pulse Φ ₁ , and 33 is a JK type flip-flop that is triggered by the carry signal of the counter 32, both of which are monostable multivibrator circuits. It is designed to be reset by the output pulse No. 19. 34 is an npn transistor for controlling the output of the amplifier 17, and the output of the flip-flop 33 is applied to its base. 35 changes the control voltage Vc to the discharge gate section 16 to the voltage Vcc5 and the voltage Vcc5 according to the state of the output of the flip-flop 33.
This is a voltage switching circuit for switching between Vcc6 and outputs voltage Vcc5 as the control voltage Vc when the output of the flip-flop 33 is low, and outputs voltage Vcc6 as the control voltage Vc when it is high. has been done. Note that detailed illustration of the configuration of the voltage switching circuit 35 is omitted here;
For example, a simple circuit configuration consisting of analog gates or the like can be adopted. Further, the voltage Vcc5 is a voltage (for example, 2 to 3 V) that makes the storage capacity of each sensor element P defined by the discharge gate section 16 approximately 80 to 90% of its saturated capacity. Further, the voltage Vcc6 is a relatively high voltage that allows the potential at the discharge gate section 16 to be equal to or lower than the potential at each sensor element P. Further, the counter 32 receives the reference pulse Φ
The counting capacity is selected so that a carry signal is output when the number of ₁ 's exceeds the number required for one output readout.

In such a configuration, when the accumulated charge is taken out from each sensor element P by the output pulses from the multi-vibrator circuits 19 and 20, the output pulse from the multi-vibrator circuit 19 at this time This resets the counter 32 and flip-flop 33, and the output of the flip-flop 33 goes high, thus turning on the transistor 34, while the voltage switching circuit 35 outputs a high voltage as the control voltage Vc.
Vcc6 will be output. As a result, the output terminal of the amplifier 17 is grounded and its output is invalidated, while the potential of the discharge gate section 16 is lowered, so that all the electric charge generated in each sensor element P is passed through the discharge gate 16. Sink part 7
, and the accumulation of charge is prohibited.
In this state, when the transfer of the signal charge taken out from each sensor element P is completed and a carry signal is output from the counter 32, the flip-flop 33 is triggered and its output changes from high to low. Therefore, while the transistor 34 is turned off, the voltage switching circuit 35 outputs the low voltage Vcc5 as the control voltage Vc. Accordingly, each sensor element P
Then, when it becomes possible to accumulate the generated charge, and in the process of charge accumulation, the excess charge flows out from one of the sensor elements P, the amplifier 1 for the output current from the sink section 7 at this time
The Schmitt trigger circuit 18 is operated depending on the output voltage of the sensor element 7, whereby a pulse is output from the multi-vibrator 19, 20, and the accumulated charge is taken out from each sensor element P again. Also, at this time, the counter 32 and flip-flop 33 are reset and set to the state described at the beginning.

Thus, in the embodiment shown in FIG.
Even if the intensity of the light incident on the optical sensor section 11 is extremely high and therefore the accumulation time T is extremely short, there is a risk that the next signal charge will mix into the signal charge that is being transferred. This will effectively prevent such situations.

As detailed above, in the imaging device of the present invention, after the start of charge accumulation in the optical sensor section, whether the amount of accumulated charge in at least a part of the optical sensor section has reached a predetermined amount of charge or not. The charge accumulation time is controlled by determining when to take out the accumulated charge from the optical sensor section by detecting the As a result, compared to conventional methods, the accumulation time can be controlled more accurately according to the intensity of the light incident on the optical sensor section.
It is possible to accurately track frequent changes in the intensity of incident light and control the output of the optical sensor device at an appropriate level at all times.In addition, the adjustment range of the accumulation time is further expanded, and the clock・Since there is no need to change the pulse frequency in any way, it does not cause problems such as increased power consumption or deterioration of charge transfer efficiency in the charge transfer section, which were seen in conventional methods, and is extremely beneficial. There are advantages to be gained.

In addition, in the example, a two-phase transfer type linear
Although only an example of application to a CCD photo sensor has been shown, the invention is, of course, not limited to optical sensor devices of this configuration, but can be applied to various other types of optical sensors, including area-type image sensors.・It can be adopted in devices.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a cross-sectional structure of an example of an optical sensor device suitable for employing the method of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention, and FIG.
The figure is a waveform diagram showing input/output signals of main circuit blocks in the second illustrated circuit, FIG. 4 is a diagram showing another embodiment of the present invention, and FIG. 5 is a diagram showing still another embodiment of the present invention. FIG. 6 is a block diagram showing an example of the voltage variable circuit shown in FIG.
The figure shows still another embodiment of the present invention. 10... Optical sensor device, 11... Optical sensor section, P... Sensor element, 12... Shift gate section, 13, 13'... Charge transfer element, 14... Output section, 16... Excess Charge discharge gate section, 7... sink section.

Claims (1)

[Claims] 1. A photosensor section that accumulates charges according to the integrated amount of incident light, an excess charge discharge section that discharges excess charges from the photosensor section, and a portion of the charges themselves that are being accumulated in the photosensor section. a detection means for detecting as a charge accumulation time control signal via the excess charge discharge section, and after the start of charge accumulation in the optical sensor section,
A charge accumulation time control means for controlling charge accumulation time in the optical sensor section by determining when to take out the accumulated charge from the optical sensor section using a signal from the detection means. imaging device.