Light sensitive semi-conductor element and arrangement

In the disclosed element, a number of line shaped sensors each includes a plurality of P-N junctions each of which accumulates a charge corresponding to the amount of light incident thereon. A number of registers, one for each sensor, each defines addresses coupled to respective P-N junctions of the corresponding sensor to have the charge accumulated on each P-N junction transferred to the respective address in each register so that time sequential signals can be obtained from each register. A collection register has an address coupled to each of the other registers to store the time sequential output signals so that the stored signals can be read out sequentially. A gate arrangement connecting the output of the first registers to each address controls the time interval during which the time sequential signals of the first registers are transferred to the accumulating register.

BACKGROUND OF THE INVENTION 
This invention relates to solid state image sensing semi-conductor 
elements, particularly those which store and transfer signals 
corresponding to image signals. 
Conventional image sensors such as CCD sensors used in television cameras 
have the disadvantage that their charge integration periods are limited by 
the time necessary to scan one field of a picture frame. This prevents 
following up changes in the object brightness. Solid state semi-conductor 
image sensors present problems of dynamic range for which no fundamental 
solution has yet been found. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide an image sensor responsive 
to a wide range of incident light signals. 
Another object of the invention is to provide an image sensor capable of 
changing the level of the output signal within a prescribed integration 
period. 
Still another object of the invention is to provide an image sensor capable 
of improving the contrast of the signal output within a prescribed range 
of integration periods. 
According to an embodiment of the present invention, a plurality of line 
sensors are provided with the same number of first register means capable 
of self-scanning each of the line sensors. Since the time-sequential 
signal outputs of this first register means are fed to and accumulated in 
the corresponding addresses of second register means, the amount of 
signals stored in each address is substantially increased. 
It should be pointed out that the above-described plurality of line sensors 
when arranged in parallel to permit the output of each sensor after having 
once been stored in the second register means to be read out in sequence 
can be used as a whole in the form of a single line sensor. 
It should be further pointed out that the use of the line sensors in such 
form gives many advantages, one of which is that since the output level of 
the line sensor can be substantially increased while the integration 
period remains unchanged, even when the object brightness is very low, the 
sensor is made sensible to a brightness change. 
Another advantage is that the device, according to the invention, can sense 
dim objects with little contrast. 
Another advantage is that, conversely, the output produced by very bright 
objects can be reduced to proper levels. 
Thus, the image sensor of the invention, because it is able to provide a 
optimum output regardless of a wide range of variations of object 
brightness, achieves a great increase in dynamic range.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention is to optimize the video signal produced from the 
solid state semi-conductor element, depending upon its purpose. To achieve 
this, an external control signal, for example, one representative of the 
object brightness or contrast is used in making up a pulse signal of 
prescribed waveform, and it is by this pulse signal that the size of a 
contribution domain of the solid state semi-conductor element to each 
picture element is caused to change arbitrarily. 
The present invention will next be described in connection with a solid 
state semi-conductor element constructed to be a line sensor having a 
photo-diodized photoelectric conversion and accumulation portion and an 
N-channel CCD-ized charge transfer portion which is the most common as the 
self-scanning type image sensor, but it is to be understood that the 
present invention is not confined to the line sensor and is applicable 
when to construct as an area sensor. 
In the following, the present invention will be described in greater detail 
by reference to the drawings. FIG. 1 shows the construction of a generally 
accepted image sensor in the form of a solid state semi-conductor element. 
In the figure, PD1 to PDN are a photoelectric conversion and accumulation 
portion comprising PN junctions forming photodiodes electrically 
independent of one another. It is noted that since the number of diodes in 
this instance is N, it is possible to form N picture elements. The anodes 
of the individual diodes PD1 to PDN are connected to a common negative 
terminal of a battery. G1 to GN each are an N-channel MOS transistor 
pairs, forming gates. The sources of each transistor pairs G1 to GN are 
both connected to the respective photo-diode PD1-PDN at the cathode 
thereof. The drain of one of the transistors in each pair G1 to GN is 
connected to the input of the corresponding address of a two-phase 
CCD-first analogue shift register RE. The gate of each of the first 
transistors is connected to an input terminal SH. The drain of the other 
transistor in each transistor pair is connected to a positive terminal VDD 
of the battery. The gate of each second transistor is connected to an 
input terminal ICG. 
The signals applied from the photo-diodes to the respective addresses in 
the analogue shift register RE are shifted in sequence by clock pulses 
.phi.1 and .phi.2, appearing at an output terminal Rout as a 
time-sequential signal. The output terminal Rout is connected through a 
charge-voltage conversion condenser or capacitor C1 to the positive 
terminal VDD of the battery and also to the gate of an FET Tr1. Connected 
to the both terminals of the condenser C1 are the source and drain of an 
FET Tr2, and the gate of the FET Tr2 is connected to a terminal RS. 
The drain of the FET Tr1 is connected to the positive terminal of the 
battery, and its source is connected through a resistor to the negative 
terminal of the battery. 
The source is also connected to a terminal Vout. 
The input SH is a charge transfer signal input terminal; ICG is an 
instantaneous clear signal input terminal; RS is a reset signal input 
terminal; .phi.1, .phi.2 are shift signal inputs of the shift register; 
and Vout is a video signal output terminal. 
FIG. 2 is a timing chart showing the waveforms of the signals occurring in 
the various portions of the circuit of FIG. 1. When the instantaneous 
clear signal is applied to the terminal ICG of FIG. 1, the charges 
photoelectrically generated and accumulated in the individual photo-diodes 
PD1 to PDN flow to the positive terminal VDD, thus being cleared up. Then, 
when a charge transfer signal is applied to the terminal SH, the charges 
in the photo-diodes are transferred to the two-phase CCD analogue shift 
register RE. As shown in FIG. 2, the time interval from the falling edge 
of the pulse ICG to the falling edge of the pulse SH defines the charge 
integration period of the photoelectric conversion and accumulation 
portion. The signal charges transferred by the shift pulses .phi.1, .phi.2 
to the shift register RE charge the charge-voltage conversion condenser 
C1, and this voltage signal appears at the terminal Vout as a video 
signal. It is noted that the condenser C1 is fed with a reset pulse for 
each picture element output as shown in FIG. 2, so that a video signal as 
shown on line Vout in FIG. 2 is produced at the output terminal. In the 
self-scanning type image sensor using the solid state image pick-up 
element of FIG. 1, the magnitude of the signal obtained from the 
photo-diodes PD1 to PDN cannot be changed because it is determined by the 
shape and characteristics of the element when designed. 
FIG. 3 is an electrical circuit diagram of one embodiment of a 
self-scanning type image sensor using a solid state semi-conductor element 
according to the present invention. The parts in FIG. 3 corresponding to 
those in FIG. 1 are denoted by the same reference characters. Though the 
solid state semi-conductor element illustrated in FIG. 3 would appear to 
resemble an interline type area sensor of NxM picture elements (in this 
instance, M=5) in construction, the present invention is characterized in 
that this is used as a line sensor and that the size of that portion of 
the domain which contributes to each picture element output is made 
variable by an external control signal GSG. 
The present invention contemplates, in stead of the former photoelectric 
conversion and accumulation portion, the use of a plurality of line sensor 
rows PD11 to PD1N in combination with CCD analogue shift registers RE1 to 
REN-1 as the first register means paired up therewith. Each of the line 
sensor rows PD11 to PD1N is formed with M PN-junctions and the charge 
accumulated on each junction is transferred to and stored in the 
corresponding one of the registers RE1 to REN in response to the input at 
the charge transfer signal input terminal SH. The charge signals stored in 
the registers RE1 to REN are applied to the sources of similar MOS 
transistor pairs G1 to GN to those of FIG. 1 in response to the shift 
clock pulses .PSI.1, .PSI.2. 
The combinations of the line sensor rows PD11 to PD1N with the registers 
RE1 to REN can each be formed to a self-scanning type photoelectric 
conversion element, and a similar drive method to that described in 
connection with FIG. 1 may be used in producing time-sequential signals 
from the individual registers RE1 to REN. 
The MOS transistor pairs G1 to GN in the present invention form gate 
circuits, the gate of one of the transistors in each pair G1 to GN being 
connected to the contribution area control signal input GSG, and its drain 
terminal being connected to the corresponding address in second register 
means in the form of a CCD or other suitable analogue shift register RE. 
The gate of the other transistor in each pair G1 to GN is arranged to be 
fed with a signal from the control signal input terminal GSG through an 
inverter IN, and its drain is connected to the positive terminal VDD of 
the battery. 
The output Rout of the second register RE is connected similar to that in 
FIG. 1. 
FIG. 4 is a timing chart showing the waveforms in the various portion of 
the circuit of FIG. 3. 
When a momentary clear signal enters at the ICG terminal, the charges 
stored in the first registers RE1 to REN are cleared up. Then, until the 
advent of a transfer signal SH, the line sensor rows PD11 to PD1N each 
accumulate a charge of a magnitude proportional to the incident light 
intensity. Responsive to this transfer signal SH, the individual charges 
are transferred to the respective addresses in the first registers RE1 to 
REN. Then, these transferred charges are caused by the shift pulses .PSI.1 
and .PSI.2 to successively produce in time-sequential relation. It is 
noted that during this time, the shift pulses .phi.1 and .phi.2 stop the 
second register RE by M bits. 
Therefore, when the signal entering the control input terminal GSG assumes 
a high level, one of the transistors in each of the gate circuits G1 to GN 
is ON, causing the time-sequential signals from the first registers RE1 to 
REN to be transferred to and additively stored in the respective addresses 
of the second register. 
On the other hand, when the control input GSG assumes a low level, only the 
other transistors of the gate circuits G1 to GN are turned on, causing the 
time-sequential signals from the first registers RE1 to REN to flow to the 
positive terminal of the battery. 
It is to be understood from the foregoing that since the transfer of the 
time-sequential signals from the first registers RE1 to REN continues only 
for a time interval during which the signal at the control input terminal 
GSG is high, it is possible to control which charge in each of the first 
registers RE1 to REN is transferred, and of how long the transfer 
continues. 
The lines labelled GSG-Ex.1, -Ex.2 and -Ex.3 represent three different 
examples of determination of such selection and duration. 
In Example 1, the 5-bit time-sequential signal is all additively stored in 
the respective address in the second register RE, so that the amount of 
charge stored reaches a maximum, and when taken out as the time-sequential 
signal output from the second register, a large output signal level is 
also attained. 
In Example 2, only the 3rd bit of the time-sequential signal is extracted 
and transferred to the second register RE, so that only the central 
portion of the area of an image formed with light coming from the object 
is sensed. 
In Example 3, only the odd-numbered bits of the signal are extracted and 
transferred. This is advantageously used when a particular optical system 
is positioned in front of the line sensor, or when the object image is 
special. 
According to an embodiment of the invention, a number of such different 
patterns for the signal GSG are readied and the selection of either one of 
the patterns is controlled so as to obtain an optimum output signal. 
Next, FIG. 5 is a block diagram showing an example of a circuit for 
changing the contribution rate of the picture element group of the solid 
state semi-conductor element to the output by changing over the 
contributing area control signal GSG in accordance with the object 
brightness. Here a sensor of 1 corresponds in construction to that shown 
in FIG. 3. A peak detection circuit 2 of known construction detects a 
maximum peak value of the output of the sensor 1. A 3 value evaluating 
circuit 3 serves for comparing the peak value detected by the peak 
detecting circuit 2 with, for example, a standard value to form a control 
signal dependent upon the brightness. A setting circuit 4 serves for the 
external control signal GSG to set the waveform of the GSG signal 
depending upon the output of the peak value evaluating circuit 3. When its 
output is applied to the sensor 1, the contributing area of the picture 
element output is changed in magnitude. Thus, the video output Vout from 
the sensor 1 is adjusted in accordance with the object brightness. It is 
noted that the setting circuit 4 may be simply such that the width of 
control signal GSG is increased depending upon the difference between the 
output of the peak detecting circuit 2 and the standard value. 
FIG. 6 is a block diagram of changing the magnitude of the contributing 
area of the picture element output of the solid state image pick-up 
element by the use of a control signal corresponding to the contrast of 
the object. The figure includes a sensor; 11 a circuit 12 for detecting 
the absolute value of difference between the picture element outputs as a 
quantity corresponding to the object contrast; and a circuit 13 for 
detecting a peak value of the difference in the output of the circuit 12. 
The output peak value of the circuit 13 is applied to a circuit 14 where 
in a similar manner to that shown in FIG. 5, a differential peak value is 
evaluated. The output of the circuit 14 is used in setting the waveform of 
the external control signal GSG by a circuit 15. Its output GSG signal 
controls the sensor 11, so the magnitude of the contributing area of the 
picture element output of the sensor 11 is varied in accordance with the 
object contrast. 
As mentioned above, in the solid state image pick-up element of the present 
invention, the picture elements forming each row of the sensor are 
constructed with a plurality of divided picture elements, and these finely 
divided picture elements are arbitrarily selected to produce by the 
external control signal. This makes it possible to properly change each 
picture element output of the solid state image pick-up element. 
Therefore, when the external control signal is formed by the object 
brightness, contrast or other information, an optimum video output for the 
condition of the object can be obtained. This results in many advantages. 
For example, the sensitivity of the sensor can be increased without 
causing the lateral resolving power of the solid state image pick-up 
element to deteriorate.