Photoelectric transducer device

In a photoelectric transducer device such as a solid state image pick-up device or sensor having a great number of minute photoelectric transducer elements with their image-receiving surfaces of certain shape arranged in a one-dimensional or two-dimensional manner so that brightness informations of the various individual sections of the object image are sensed by the respective photoelectric transducer elements which then produce outputs in the form of time-sequential signals, the above-described shape of the image-receiving surface area of each of the minute photoelectric transducer elements is made to be such that, as the distance from the center of the image receiving area toward the margin increases, the proportion of the area of a progressively farther concentric zone of the same width is decreased. The shape takes such a form or such characteristics as to be represented by a sampling function or other analogous functions with respect to the scanning direction of the image pick-up device.

BACKGROUND OF THE INVENTION 
This invention relates to photoelectric transducer devices usable as image 
pick-up elements for television cameras, or as sensor elements for 
auto-focus systems in photographic cameras. 
Recently, photoelectric transducer devices using minute photoelectric 
transducer elements have found their increasing use as an image pick-up 
element in television cameras, or as a device for AF in photographic 
cameras. In particular, a great number of silicon photodiodes (SPD) in an 
array constituting an XY assigning device, and a charge coupled device 
(CCD) are used as a light sensor for converting the brightnesses of the 
various image sections in the image plane to electrical signals in time 
sequence which are read out in the form of a video signal. 
What has also generally been used in the past as the light sensor is the 
electron beam scanning type image pick-up device, for example, in the form 
of a vidicon type image pick-up tube having a target surface of 
finely-divided photoelectric particles on which an image of the object is 
focused while being scanned by a fine electron beam to obtain a video 
signal. This scanning electron beam is of almost round cross-section at 
the target plane. The brightness informations of the various image 
sections are read out by an electron beam in time sequence so as to 
provide outputs in the form of a video signal. 
On the other hand, in order to construct a two-dimensional light sensor by 
the use of a solid state image pick-up device such as a CCD, it is the 
common practice in the prior art to configure each element in the 
photoelectric transducer to a square shape. These square elements all 
integrate the object brightnesses within the respective image-receiving 
surfaces and store them in the form of charges which are then sequentially 
read out on the basis of the self-transfer function in response to clock 
pulses. Thus, types of information representing the brightnesses of the 
various image sections corresponding to the addresses of the respective 
elements can be obtained as the time-sequential signals. 
In this connection, it should be pointed out that, when the individual 
minute photoelectrical transducer elements are arranged to define the 
individual respective image sections, each of the minute elements converts 
the sum of brightness within its image receiving surface of a 
corresponding electrical quantity, and therefore when each minute element 
is square in the area as has been mentioned above, it cannot be said in a 
strict sense that the output of each element is, in sampling the 
brightness of the respective image section. 
That is, in general, the "brightness information in each minute image 
section" essentially refers to "what is obtained by integrating the 
brightness while reducing the weight for the brightness value 
progressively from the center of the area of that image section outwards." 
In the case of the square photoelectric transducer elements, such 
weighting is neglected and instead a uniformization is crept in. 
There are exceptions, however, if the objective lens for forming an image 
of the object on the array of these photoelectric elements has so large an 
aberration that the brightnesses at the various points on the object are 
to be distributed about the corresponding image points at the focal plane 
and are somewhat weighted. In this case, the error resulting from the 
above-described particular shape of each of the minute image sensing 
elements can be compensated for to some extent. 
However, where the outputs from the elements, for example, between adjacent 
two bits to each other are compared, the use of the square element 
configuration can create a large gap between the output signals, because 
the weight in the neighborhood of the boundary between the two elements 
becomes larger than it actually is. 
Another problem arises, for example, when two or three images of the same 
object are formed on respective image pick-up devices through an 
intermediary such as a dichroic mirror system or other suitable light 
splitting systems as in the color television camera. When the output 
signals from such plurality of image sensing devices are processed to 
obtain a video signal, it is required that the relative position of the 
photoelectric transducers be accurately adjusted, or otherwise its 
influence on the output signal would present itself very noticeably when 
no weight from the center is given in the brightness integration as in the 
square pattern. With this arrangement particularly when formed as a 
two-dimensional sensor as in a television system, since the lateral 
direction of the field coincides with the line scanning direction and with 
that in which the time-sequential signals are read out successively, the 
later signal treatment must be carried out by using very elaborate means, 
or otherwise it will be difficult to absorb the above-described error. 
As for the vertical direction, since interlaced scanning is performed, the 
photosignals from the vertically adjacent transducer elements occur in a 
time gap on the order of about 1/60 second, and therefore, the buffering 
of the gap of signal between the upper and lower two bits becomes very 
difficult to achieve no matter how well the later treatment of the signals 
may be carried out. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a photoelectric 
transducer device capable of sampling brightness information of an object 
image more correctly than was heretofore possible. 
Another object of the invention is to obtain image section dependent, 
time-sequential signals which are more amenable to later signal treatment 
employing simple signal processing techniques. 
Still another object of the invention is to provide an assembly of two or 
more photoelectric transducer devices for converting images of the same 
object to corresponding number of electrical signals with the limitation 
of the signal error resulting from the deviation of the relative position 
of the devices from the ideal points to a minimum. 
A further object of the invention is to provide an image pick-up device 
which is adapted to the later fine adjustment. 
According to an embodiment of the present invention, in a photoelectric 
transducer device having photoelectric transducer elements with their 
light receiving surfaces arranged in different points of position from 
each other to convert the brightnesses of different image sections of the 
object image to electrical signals which are then read out in time 
sequence, the above-described light receiving surfaces of the 
photoelectrical transducer elements are configured to such a shape that 
the proportion of a progressively farther outer zone of the area toward 
the surrounding other light receiving surfaces is progressively smaller, 
whereby the brightness information of the object image can be sampled more 
correctly. 
Another advantage arising from the reduction of the weight on the signal in 
the neighborhood of the boundary of each photoelectric transducer element 
is that the gap of the output signal produced at this boundary region can 
be minimized. 
In the following stage including a digital signal processing circuit, 
therefore, a faulty operation can be prevented from occurring. 
Still another advantage arising from the progressive reduction of the area 
of the light receiving surface of each of the photoelectric transducer 
element in a direction toward the ones of the other photoelectric 
transducer elements which are adjacent thereto in the directions 
perpendicular to that in which the scanning means runs, is that when a 
color image pick-up apparatus is comprised of two or more photoelectric 
transducer devices of the invention, there is little room to produce a 
registration error or the like. 
A further advantage is that, if the area of the light receiving surface of 
each of the photoelectric transducer elements is represented by a sampling 
function in terms of the distance measured from the center of the area of 
the light receiving surface as a parameter, or an approximate function 
thereto, the brightness information of the object image can be sampled 
very precisely so that the later signal processing can be carried out 
without causing the occurrence of any erroneous discrimination or the 
like. 
A still further advantage is that, since the boundary of each of the light 
receiving surfaces of the photoelectric transducer elements with the 
adjacent ones includes lines making certain angles with the scanning 
direction as the scanning advances, the output of one of the photoelectric 
transducer elements is transferred to that of the next one very smoothly, 
whereby a strained weighting can be avoided.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will next be described in greater detail by reference 
to the drawings. FIG. 1 shows the photoelectric transducer portion, in 
part in, the conventional photoelectric transducer device, for example, a 
CCD. In the figure, A1, A2, A3 . . . are photoelectric transducer elements 
oriented in a lateral direction (line scanning direction) and each having 
a square image receiving surface. These square elements are lined up in 
adjoining relation to each other through respective channel stoppers S1, 
S2, S3, . . . and form a 100th element row. Similarly, after a space from 
the above-described 100th row of elements, there are a 101st row of 
elements B1, B2, B3, . . . which are then similarly followed by a 102nd 
row of elements C1, C2, C3, . . . , and so on. These rows of elements are 
all vertically aligned with each other. Thus, the elements A1, B1, C1, . . 
. are column-oriented, and they form a two-dimensional sensor. These 
individual photoelectric transducer elements permit the luminance 
information of the various section of an object image formed on the 
2-dimensional sensor at the respective elements to be converted to 
electrical charges, and these charges to be stored. These information 
signals are transferred to a charge transfer portion by clock pulses, and 
then produced as time-sequential signals through a register portion read 
out by the self-charge transfer function. 
FIG. 2 shows the use of three photoelectric transducer devices of FIG. 1 in 
constituting part of an image pick-up system in a color television camera. 
In the figure, element 2 is an objective lens; elements 3, 5 and 7 are 
dichroic prisms constituting a light splitting optical system, these parts 
forming a three-color separation optical system. 
Elements 4, 6 and 8 are blue, red and green image pick-up devices 
respectively with their target surfaces on which the blue, red and green 
components of the object image separated by the dichroic prism are 
focused. These blue, red and green image pick-up devices produce output 
signals which are then processed and transmitted from the camera as the B, 
R and G signals for the normal television, or the Y, I, Q signals for NTSC 
system. 
In color television cameras, the three image pick-up devices are required 
to be precisely aligned with one another mechanically so that no 
registration error is produced between the three signal outputs, and the 
relative element in each photoelectric transducer device represents the 
luminance of the same image section. 
But, this precision for an image of 2 cm long in the vertical direction and 
525 scanning lines with the resultant size of the above described image 
section being in the order of 40 .mu.m, has to be limited to 8 .mu.m, even 
though 20% misalignment is made acceptable. 
Therefore, a precision adjustment on the order of a few microns must be 
made with high reliability. 
Now let us assume that the conventional type solid state image pick-up 
devices are used in the above-described three-tube color television 
camera, while, as shown in FIG. 3, the red and green image pick-up plates 
are misaligned from each other by a magnitude, .delta., in the vertical 
direction. In FIGS. 3, 3R1, 3R2, 3R3, . . . are an n-th row of 
photoelectric transducer elements in the red image pick-up tube; 3G1, 3G2, 
3G3, . . . are a row of photoelectric transducer elements of the same 
address as the n-th row of the above-described red image pick-up tube in 
the green image pick-up tube. Also, 3R11, 3R12, 3R13, . . . are an (n+1)th 
row of photoelectric transducer elements in the red; and 3G11, 3G12, 3G13, 
. . . are an (n+1)th row of photoelectric transducer elements of the same 
address in the green. When correctly adjusted, these elements of the same 
address do not produce a registration error. As has been mentioned above, 
however, when the above-described red and green sensor plates are fixed in 
a condition that there is an error in the vertical direction, as the 
yellow component of the object image on the n-th and (n+1)th rows in these 
sensor plates changes like Y in FIG. 3, the n-th rows in the sensor plates 
receive this Y component in uniformity over the entire area of the image 
receiving surface of each photoelectric transducer element in the red and 
green sensors so that the red and green portions of spectrum of the yellow 
component are converted to respective electrical charges and upon later 
combination of the outputs from the two n-th rows, the original yellow 
component can be reproduced. While, on the contrary, it is in the (n+1)th 
rows that as far as the upper marginal zone of the width .delta. (for 
example 20%) is concerned, the Y component of the incident light bearing 
an object image is detected by only the red sensor elements 3R11, 3R12, 
3R13 . . . , but not by the green sensor elements 3G11, 3G12, 3G13. 
Therefore, the outputs from the (n+1)th row of red sensor elements differ 
from those of the same row of green sensor elements with the result that 
the reproduced color deviates from the true one. This means a 
deterioration of image quality. In more detail, when a picture is 
reproduced, the upper part of the picture which is yellow is downwardly 
followed by a red-rich part in one scanning line, thus giving an 
unpleasant impression to the viewer. 
Such example is not always attributable to the misalignment of the tubes, 
and is encountered when the object includes a nearly horizontal yellow 
band or the like. 
It is to be understood that as the registration error of 20% at most is now 
assumed to be acceptable, the configuration of each sensor element to a 
square shape as in the prior art, because of its lacking any weight on the 
integration in the vertical direction, permits the incorrect adjustment of 
alignment to present itself fully in the form of a color deviation of the 
output signals. 
The present invention is intended to provide a novel arrangement of 
photoelectric transducer elements of special shape which minimizes the 
production of erroneous signals for color deviation due to such incorrect 
adjustment of alignment of the image pick-up devices as described above. 
FIG. 4 shows an example of configuration and orientation of the image 
receiving surfaces of the photoelectric transducer elements in the device 
of the invention. In the figure, there is shown an equivalent portion of 
the device to that shown in FIG. 3, where each element is oriented as 
turned by 90.degree. from the position of FIG. 3 so that the opposite two 
corners are in a line parallel to the scanning direction. It is noted that 
the image receiving surface is not necessarily of regular square shape, 
but may be of a rhombic shape. Unlike the conventional orientation of the 
elements as shown in FIG. 3 where no weighting is made in the scanning 
direction as the distance from the center of the area increases, the 
element orientation of the invention in FIG. 4 gives rise to the creation 
of a weighting with respect to the central portion of the area. In other 
words, the pattern of FIG. 4 obtained by turning the square surfaces of 
the elements by 90.degree. is characterized in that, as the distance from 
the center of the area of the surface to the adjacent ones of the other 
photoelectric transducer elements increases, the proportion of the area of 
a concentric zone decreases. 
With a plurality of light sensor tubes having such arrays of photoelectric 
transducer elements as described above used in the image pick-up system of 
the color television camera of FIG. 2, when the misalignment amounts up to 
the same value, for example, 20% as in the conventional one, it is found 
that the net error can be reduced to about 16%. Therefore, even when the 
yellow component of the object image changes like Y' in FIG. 4, the color 
deviation due to the registration error can be lessened with an advantage 
that the precision adjustment of the apparatus can be carried out far more 
easily than was in the prior art. 
Next, explanation is presented concerning the construction of the 
photoelectric transducer elements of the invention in the form of a 
one-dimensional sensor, and the application of this sensor to an automatic 
focus detecting system of a photographic camera by reference to FIG. 5. In 
the figure, elements 103 and 105 are one-dimensional sensor arrays of 
photoelectric transducer elements arranged on a common line as spaced from 
each other by a distance or base line d. Element 102 is a lens system for 
forming a reference object image on the sensor array 103; element 104 is a 
lens system for forming an active object image on the sensor array 105. To 
measure the distance from the camera to the object, the angular position 
of the axis of the lens system 104 is made to change so that two images of 
the same object are formed on the respective sensor arrays 103 and 105 
with the resultant angle at the intersection of the two optical axes 
contributing along with the base line length to calculate the distance. 
If such apparatus illustrated has a registration error between the relative 
two of the elements in the sensor arrays 103 and 105, a logic noise 
migrates into the distance measurement result so that an accurate 
detection of the object distance becomes impossible. In the apparatus as 
shown in FIG. 5, when the orientation and configuration of the 
photoelectric transducer elements is changed from the conventional as 
shown in FIG. 3 to that of the invention as shown in FIG. 4, even the 
presence of the same alignment error can reduce the amount of logic noise 
migrated in the measurement result with an advantage that a faulty 
operation of the following stage electrical circuitry can be lessened. 
As in the above, in the photoelectric transducer device of the invention, 
the spatial characteristics of the light receiving portions of its 
photoelectric transducer elements are so adjusted that the gain at a point 
of position nearer to the margin is made smaller by changing the shape and 
orientation of the light receiving portion, or by positioning a diffusion 
plate in front of the light receiving portion, thus as a total imparting 
such characteristics to the light receiving portion. Therefore, when the 
outputs from the plurality of light sensor tubes are combined, the 
migration of an erroneous signal (logic noise) due to the registration 
error is made smaller than was in the conventional one. For the shape of 
the element, mention may be made of those defined by 
##EQU1## 
representing the sampling function in the information theory where the 
area of each light receiving surface is measured from the center of each 
light receiving surface outward. If this is satisfied, the analogue change 
of the incident light can be converted to a spatial digital quantity 
correctly. In this case, the boundary between the adjacent light receiving 
surfaces is defined by a triangular function waveform. In practice, 
however, this may take the form of an approximate triangular function as 
shown in connection with the above-described example. Even from this, a 
considerable improvement can be expected. 
Next, another embodiment of the present invention where the photoelectrical 
transducer device is so constructed that the logic noise can be lessened 
in the lateral direction (scanning direction) is described. 
FIGS. 6 are fragmentary front elevational views in an enlarged scale of the 
conventional array of photoelectric transducer elements of the shape known 
in the art and of an example of an array of photoelectric transducer 
elements of a shape characteristic of the invention, and shows examples of 
input and output signal waveforms. In the drawing, FIG. 6(a) shows the 
conventional type photoelectric transducer element pattern, and FIG. 6(b) 
a new photoelectric transducer element pattern according to the present 
invention. Now assuming that the patterns of FIGS. 6(a) and 6(b) are 
scanned laterally, then when the luminance of light incident upon each of 
the arrays changes as shown in FIG. 6(c), the array of FIG. 6(a) produces 
output signals as shown in FIG. 6(d), and the array of FIG. 6(b) produces 
output signals as shown in FIG. 6(e). It will be appreciated from the 
waveforms that as the luminance changes stepwise, the output signals of 
the pattern (a) are caused to change their amplitudes largely in 
correspondence with the phase of luminance change and the interrelation of 
the sensor element pitch therewith. Therefore, the use of such signals 
from the conventional pattern of photoelectric transducer elements in 
measuring the degree of image sharpness, or in pattern recognition leads 
to the production of a large error. In other words, the sensor pattern 
rapidly quantizes the luminance pattern so that a so-called "folded 
strain" is liable to be produced and therefore there is a high possibility 
of occurrence of a moire in the reproduced pattern. 
Unlike this, since the sensor pattern (b) of the invention forms a spatial 
high cut filter, the output signals of FIG. 6(e) are made less sensible to 
the phase shift in relation to the luminance change pattern, thereby it 
being made possible that a smaller "folded strain" is produced. 
For the method of reducing such "generation strain" usable in a two-tube 
color television camera with each sensor plane provided with a respective 
color filter, mention may be made of a low pass filter in the form of an 
electrical circuit from which an equivalent effect to that of the 
invention can be expected, as the influence of the registration error 
between that color filter and the sensor on the color deviation is 
generally considered to be effectively lessened by the use of the low pass 
filter. This measure takes its place in the signal process after the 
quantization and it is therefore to be understood that this is different 
from the spatial filter effect before the quantization in the device of 
the present invention, and that the above-described conventional method 
though being able to smooth the signal waveform, has no effect of reducing 
the "folded strain." 
All what is necessary to realize the photoelectric transducer element 
pattern of the invention is only to change the mask in the process for 
fabricating the sensor plate, while nevertheless a great advantage is 
expected. It is to be noted that in the case of the two-dimensional 
sensor, depending upon which direction, horizontal or vertical is 
emphasized, the pattern can be made more complicated in that emphasized 
direction than in the above-described embodiment, for example, a hang 
curve. 
FIGS. 7(a) to 7(e) show other examples of patterns usable in the 
photoelectric transducer device of the invention. The pattern of FIG. 7(a) 
is adapted for use in a vertically somewhat elongated sensor, and has the 
boundary lines between the adjacent image receiving surfaces as diffused 
into each other in the horizontal as well as in the vertical direction. 
The pattern of FIG. 7(b) has those of the boundary lines which are inclined 
over the entire width of each row-oriented photoelectric transducer 
element, so that the weight is decreased in the horizontal direction. 
The pattern of FIG. 7(c) is an example of modification of the pattern of 
FIG. 7(b) with the reduction of weight also in the vertical direction. 
The pattern of FIG. 7(d) is another example of modification of the pattern 
of FIG. 7(b) and has the boundaries between the successive two image 
receiving surfaces in each row which are configured to a progressively 
stepped-up shape in the scanning direction. 
The pattern of FIG. 7(e) has the boundaries between the successive two 
row-oriented image receiving surfaces which are curved to a triangular 
function shape so that the surfaces can be represented by a sampling 
function. 
It is noted that since the photoelectric transducer device of the invention 
employs no such simple or regular square shape for the light receiving 
surfaces of the photoelectric transducer elements corresponding to the 
image sections as in the prior art, but a particular shape analogous to a 
sampling function in its scanning direction or in a direction 
perpendicular thereto in order that the sampling of each image section 
should become very accurate so that faulty operation of discrimination in 
the following stage signal processing circuit can be prevented. Further 
the large change of the output signal due to the phase shift between the 
sensor and the image can be lessened, even when applied not only to the 
case where more than a pair of outputs of the sensors are combined with 
each other as has been described in connection with the embodiment of the 
invention but also to the case where, for example, a single-tube color 
television camera employs such a photoelectric transducer device as of the 
present invention in place of the image pick-up tube thereof in 
combination with a color stripe filter, such large reduction of the range 
of variation of the output signal can be assured. 
As has been described in greater detail in connection with the embodiments 
of the invention, it is made possible by the use of the photoelectric 
transducer device of the invention that the logic noise due to the 
registration error which occurs when a plurality of row- and 
column-oriented photoelectric transducer elements are scanned is 
remarkably reduced. Therefore, a great advantage can be expected from the 
application of the invention to color television cameras in which the 
outputs of two or more solid state image pick-up devices are combined to 
produce a video signal, and to auto-focus cameras in which the light 
sensor is required to be as effective a pattern as possible.