JPS6230577B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photoelectric conversion device having a plurality of photoconductive elements such as CDS arranged one-dimensionally.

FIG. 1 shows the basic configuration of this type of photoelectric conversion device. Reference numeral 1 denotes an image sensor, which includes N photoconductive elements A ₁ to A _N arranged in one row.
The photoconductive elements A ₁ to A _N have resistors R ₁ to A N, respectively.
R _N are connected in series, each photoconductive element A ₁ ~
The connection points between A _N and the resistors R ₁ to _RN are connected to the inputs of the amplifier 2 via switches S ₁ to _SN , respectively.

Then, each photoconductive element A ₁ ~
When a common constant voltage is applied to A _N and resistors R ₁ to R _N , the resistance value of each photoconductive element A ₁ to _{A N} changes depending on the amount of light incident on them. The voltage at the connection point between _N and resistors R ₁ to R _N is
The value corresponds to the amount of light incident on each of the photoconductive elements A ₁ to A _N .

Therefore, by sequentially selectively turning on the switches S ₁ to _SN , time-series electrical signals corresponding to the pattern of light incident on the photoconductive elements A ₁ to A _N are sent to the amplifier 2.
can be obtained from the output of

However, in an actual photoelectric conversion device of this type, the total number N of photoconductive elements is ₁₀₀₀ to ₂₀₀₀ , and as in the circuit shown in FIG. Since it is impossible to provide the switches S ₁ to S _N in terms of implementation, conventional photoelectric conversion devices of this type have a circuit configuration as shown in FIG. 2.

That is, in FIG. 2, 1 is an image sensor, and m×m photoconductive elements A ₁ to A _no ,
It has diodes _D1 to _Dno connected in series to these photoconductive elements _A1 to _Ano , respectively.
The photoconductive elements A ₁ to _{A no} are divided into m blocks, with n photoconductive elements forming one block.

One ends of the photoconductive elements A ₁ to _{A no} are collectively connected to common side terminals l ₁ to l _n for each of the blocks, respectively, via diodes D ₁ to D _no . Further, the other end of the photoconductive elements A ₁ to _{A no} is
Those located at corresponding positions in the block are grouped together and connected to individual side output terminals P ₁ to _{P o} .

The common terminals l ₁ to _{l n} are connected to the positive pole of the constant voltage power supply 3 via switches S _a1 to _{S an} and a resistor R, respectively. One pole of this constant voltage power supply 3 is grounded. Further, the common side terminals l ₁ to l
Resistors R _a1 to R _an are connected between _n and ground. The separate output terminals P ₁ -P _o are connected to the inputs of the amplifier 2 via switches S _b1 -S _bo , respectively, and are grounded via resistors R _b1 -R _bo .

In this conventional device, as shown in the timing chart of FIG. 3, by sequentially turning on the switches S _a1 to S _an , a constant voltage of photoconductive elements A ₁ to A _no is supplied to each block from the constant voltage power supply 3. A voltage is applied. Then, as mentioned above, the switch S _a1 ~
By sequentially turning on the switches S _b1 to S _bo during each period in which S _an is turned on, the output voltage of the photoconductive elements A ₁ to A _o of the first block changes to the individual side output terminal P. ₁ and the switch S _b1 , and then the output voltage of the photoconductive elements A _o+1 to A _{2 o} of the second block is inputted to the amplifier 2 via the individual side output terminal P ₂ and the switch S _b2 . The signals are sequentially input to the amplifier 2, and the same operation is performed for the remaining blocks.

As a result, a time-series electrical signal k (hereinafter referred to as a photoelectric conversion signal) corresponding to the pattern of light incident on each of the photoconductive elements A ₁ to _{A no} can be obtained from the photoelectric conversion signal output terminal 4 .

However, there are variations in the photoconductive characteristics of each of the photoconductive elements _A1 to _Ano , and if this variation is not corrected, there will be variations in the reference level of each bit of the photoelectric conversion signal k obtained from the photoelectric conversion signal output terminal 4. It will happen.

Therefore, in the conventional device shown in FIG. 2, due to the manufacturing process of the photoconductive element array, variations among the photoconductive elements A ₁ to _{A no} that are located close to each other,
Rather than variations between elements located far from each other,
Taking advantage of the small size, the above correction was performed for each block. That is, by adjusting the values of the resistors R _a1 to _{R an} and changing the ratio at which the voltage E of the power source 3 is divided by the resistors R and R _a1 to _{R an} , the average output of the photoconductive elements of each block is adjusted. The above correction was performed by making them the same.

In FIG. 3, k ₁ represents each photoconductive element A ₁ to A _n
A uniform amount of light is incident on _o , and low resistance R _a1 =R _a2 =
The photoelectric conversion signal k of one line is shown when . . . =R _an . Further, _k2 indicates the light guide conversion signal k of one line when the resistances R _a1 to R _an are adjusted and the correction is performed. As can be seen _from the figure, the variation E _{2 in k 2} is smaller than the variation E ₁ in k ₁ .

Note that in the above case, v is the common side terminal l _1
.about.ln , specifically, the voltage is proportional to the reciprocal of the average value of the output of the photoconductive elements of each block in the case of _k1 .

However, with such a conventional device, not only is it impossible to compensate for variations in the characteristics of photoconductive elements within each block, but also the total number of photoconductive elements (m×n) is 2000 as described above. Therefore, the number of blocks of the photoconductive element is 50 to 100 m.
Therefore, adjusting and setting the values of the resistors R _a1 to _{R an} connected to each of these blocks one by one requires a great deal of effort and work time, making mass production virtually impossible. There was a drawback.

The present invention was made to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a photoelectric conversion device that can extremely easily correct variations in photoconductive characteristics of each photoconductive element.

That is, the photoelectric conversion device according to the present invention includes a plurality of photoconductive elements arranged one-dimensionally, a voltage generation circuit that sequentially outputs voltages set for each of the photoconductive elements, and a voltage generating circuit that sequentially outputs voltages set for each of the photoconductive elements. a switching circuit that applies the voltage to the corresponding photoconductive element and a resistor connected in series to the photoconductive element, and application of the voltage by this switching circuit to the respective photoconductive element and the and means for temporally synthesizing the voltages generated at the connection points with the resistors.

The present invention will be explained in more detail below based on the drawings.

FIG. 4 shows an embodiment of the present invention, and FIGS. 5 and 6 show timing charts in this embodiment (FIG. 6B is a partially enlarged view of FIG. 6A). In FIG. 4, reference numeral 1 denotes an image sensor, which has the same configuration as in FIG. 2. 5
is a master clock generation circuit that generates master clock c.

Reference numeral 6 denotes a scanning address generating section consisting of a multi-stage frequency dividing circuit, which divides the frequency of the clock c inputted from the master clock generating circuit 5 and outputs the output of each stage as address signals a and b. FIG. 5 shows an example in which the address signals a and b are binary waveforms,
The address signal b is obtained by further dividing the frequency of the address signal a.

7 is a memory circuit consisting of a ROM, and as will be explained in detail later, each of the photoconductive elements A ₁ to _{A no} has been determined in advance in order to correct variations in the photoconductive characteristics of the photoconductive elements A ₁ to A _no. The correction data d for the address signals a,
This correction data d is read by using b as an address input.

8 is a D/A converter for D/A converting the correction data d read out from the memory circuit 7, and 9 is a constant voltage power supply having one pole grounded. Reference numeral 10 denotes an amplifier, and its input is changed over via a switch 11 to output e of the D/A converter 8 or + of the constant voltage power supply 9.
It is designed to be connected to a pole.

The output of the amplifier 10 is connected to the common side terminal of the image sensor via transistors _F1 to _Fn , respectively.
It is connected to l ₁ to l _n . In addition, the individual side output terminals P ₁ to _{P o} of the image sensor 1 are transistors G ₁
~G _o to one end of a common resistor R _c , and the other end of this resistor R _c is grounded.
The connection point between the transistors G ₁ to _{G o} and the resistor R _c is connected to the input of an amplifier 2 , and the output of this amplifier 2 is connected to a photoelectric conversion signal output terminal 4 .

Reference numeral 12 denotes an m-bit parallel output decoder which receives the address signal b as an input, and the m-bit outputs f ₁ to f _n of this decoder 12 cause the transistors S ₁ to
The on/off state of S _o is controlled respectively.

Reference numeral 13 denotes an n-bit parallel output decoder which receives the address signal a, and the n-bit outputs g ₁ to _go of this decoder 13 cause the transistors G ₁ to
The on/off of G _o is controlled respectively.

Next, the operation of this embodiment will be explained based on the timing charts and voltage waveform diagrams shown in FIGS. 5 and 6.

First, the changeover switch 11 switches the amplifier 10
A constant voltage power supply 9 is connected to the input of the photoconductive elements A _{1 to A no, and a uniform amount of light is made incident on each of the photoconductive elements A 1 to A no} .

In this state, when the address signal b is sequentially input from the scanning address generator 6 to the decoder 12, the outputs f ₁ to f _o of the decoder 12 are sequentially set to high level (hereinafter abbreviated as "H") one by one. ), and accordingly, transistors F ₁ to F _n are sequentially turned on.

Also, during this period, the address signal a is input from the scanning address generator 6 to the decoder 13, so that the outputs g ₁ to go of the decoder 13 are sequentially output for each period in which the transistors F ₁ to _{F n} are turned _on . The level becomes "H" one by one, and the transistors G ₁ to _{G o} are sequentially turned on accordingly.

As a result, the output voltage (constant voltage) of the amplifier 10 is sequentially applied to each of the photoconductive elements A ₁ to _{A no} via the diodes D ₁ to D _no with the resistor R _c connected in series. The output voltages of the photoconductive elements A ₁ to _{A no} generated by the application of the output voltage of the amplifier 10 are sequentially input to the amplifier 2, so that the output voltages from the photoelectric conversion signal output terminal 4 as shown in k ₁ in FIG. Time-series photoelectric conversion signals corresponding to such variations in photoconductive properties of each of the photoconductive elements A ₁ to _{A no} can be obtained.

In this embodiment, a value proportional to the reciprocal of the voltage value of the photoelectric conversion signal k ₁ for each photoconductive element A ₁ to A _no is encoded into a binary number, and this is used as correction data d to be stored at the corresponding address of the memory circuit 7. (This writing operation to the memory circuit 7 is performed using a circuit jig or the like that is separate from the main circuit.

Then, the actual optical information is transferred to the photoconductive elements A ₁ to _{A no}
If you want to read it, press the switch 11.
and connects the output e of the D/A converter 8 to the input of the amplifier 10. In this state, when address signals a and b are input from the scanning address generating section 6 to the memory circuit 7, correction data d of the addresses specified by the address signals a and b are sequentially read out from the memory circuit 7. .

This sequentially read correction data d is D/A converted by the D/A converter 8, and the D/A converter 8
Since the output e is amplified by the amplifier 10, the amplifier 10 sequentially outputs a voltage having a value corresponding to the correction data d for each of the photoconductive elements _A1 to _Ano .

On the other hand, during this time, since the address signals a and b are also input to the decoders 12 and 13, respectively, the transistors F ₁ to F _o and G ₁ to _{G o} are sequentially turned on at the same timing as described above. Therefore, the output voltages of the amplifier 10, which are sequentially output, are applied to the corresponding photoconductive elements _A1 to _Ano and the resistor _Rc . At this time, each photoconductive element A ₁ to _{A no}
By amplifying the output in the amplifier 2, a time-series photoelectric conversion signal k corresponding to the one-dimensional light pattern incident on the photoconductive elements _A1 to _Ano is obtained at the photoelectric conversion signal output terminal 4. .

Here, the output h of the photoconductive elements A ₁ to _{A no} is a value obtained by dividing the output voltage of the amplifier 10 by the resistance of the photoconductive elements A ₁ to _{A no} and the resistance R _c , but in this case, Since the output voltage of the amplifier 10 applied to each of the photoconductive elements A ₁ to A _no is not common and has a value corresponding to the correction data d for the photoconductive elements A ₁ to _{A no} , photoelectric conversion signal k
has been corrected for variations in photoconductive characteristics among the photoconductive elements A ₁ to _{A no} .

k ₂ in FIG. 6 indicates the photoelectric conversion signal k when the above correction is performed when a uniform amount of light is incident on each photoconductive element A _{1 to} A _no ;
By correcting the variation in the characteristics of ~A _no , the value becomes uniform over one line.

As described above, according to this embodiment, the photoconductive element A ₁
~A _{no It} is possible to completely correct the variations in the characteristics of each individual photoconductive element, but the variation between photoconductive elements located close to each other is practically negligible, and the variation in photoconductive elements between blocks is If this is a problem, it is also possible to perform the above correction for each block by setting the correction data d for each block. In that case, the memory circuit 7 can be a small-capacity memory circuit that uses only the higher-order signal b of the address signals a and b.

Note that the voltage applied to each photoconductive element A ₁ to _{A no} is constant, and the amplification factor of amplifier 2 is set to
Although it is possible to correct the variations by sequentially changing A ₁ to _{A no} in accordance with variations in the photoconductive properties, this case has the disadvantage of handling minute signals. However, when the voltages applied to each of the photoconductive elements A ₁ to _{A no} are changed in response to variations in each of the photoconductive elements A ₁ to A _no as in the present device, such disadvantages do not occur.

As described above, the photoelectric conversion device according to the present invention includes a voltage generation circuit that sequentially outputs a voltage set to each photoconductive element, and a voltage generating circuit that outputs the voltage set to each photoconductive element, and a resistor connected in series to the corresponding photoconductive element. By having a switching circuit for applying voltage, it is extremely easy to correct for variations in the photoconductive characteristics of each photoconductive element without the need for the troublesome adjustment and setting of a large number of resistance values as in the past. It is possible to obtain excellent effects such as being able to perform

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the basic configuration of a light guide conversion device equipped with photoconductive elements arranged one-dimensionally, FIG. 2 is a circuit diagram showing a conventional light conversion device, and FIG. 3 is a circuit diagram showing the conventional device. FIG. 4 is a circuit diagram showing an embodiment of the photoelectric conversion device according to the present invention, FIG. 5 is a timing chart of the embodiment,
FIG. 6A is a voltage waveform diagram of the photoelectric conversion signal and the output of the D/A converter in the embodiment, and FIG. 6B is an enlarged view of FIG. 6A. 2...Amplifier, 4...Photoelectric conversion signal output terminal,
6...Scanning address generation section, 7...Memory circuit,
8...D/A converter, 10...amplifier, 12...
m-bit parallel output decoder, 13... n-bit parallel output decoder, A ₁ to _{A no} ... photoconductive element, F ₁ to F _o , G ₁ to G _o ... transistor, d...
...Correction data, h...Photoconductive element output.

Claims (1)

[Scope of Claims] 1. A plurality of photoconductive elements arranged one-dimensionally, a voltage generating circuit that sequentially outputs a voltage set for each of the photoconductive elements, and a voltage generating circuit that sequentially outputs a voltage set for each of the photoconductive elements, and a switching circuit that applies a voltage to the corresponding photoconductive element and a resistor connected in series to the photoconductive element; and a switching circuit that applies a voltage to the corresponding photoconductive element and a resistor connected in series to the photoconductive element; 1. A photoelectric conversion device comprising means for temporally synthesizing voltages obtained by 2. The voltage generation circuit includes a memory circuit in which correction data for each photoconductive element is written, and a voltage output circuit that sequentially outputs a voltage for each photoconductive element based on the data sequentially read from the memory circuit. A photoelectric conversion device according to claim 1.