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Claims  |
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What is claimed is:
1. An image processing system for a color television camera comprising:
a color filter that separates light from an object being photographed into
a plurality of color images having different colors;
an imaging element that receives the plurality of color images from the
color filter and outputs image signals based on an amount of charge that
accumulates in said imaging element during an accumulation interval while
said imaging element is receiving each of said plurality of color images;
and
a timing regulation device that sets the accumulation interval of the
imaging element based on color mixing intervals during which more than one
of said color images simultaneously are received by said imaging element.
2. The image processing system of claim 1, wherein said imaging element is
a solid state imaging element.
3. The image processing system of claim 1, wherein said color filter
includes color boundaries between different color portions of said color
filter, and said color mixing interval is an interval during which one of
said color boundaries is passing over said imaging element.
4. The image processing system of claim 1, wherein said timing regulation
device sets the accumulation interval of the imaging element to correspond
to an interval other than said color mixing intervals.
5. The image processing system of claim 1, wherein said imaging element
receives the plurality of color images sequentially from said color filter
such that said color television camera is a field-sequential color
television camera.
6. The image processing system of claim 1, wherein said imaging element
accumulates charge in a series of fields, and said timing regulation
device sets the accumulation interval in all of said fields.
7. The image processing system of claim 1, wherein said imaging element
accumulates charge in a series of fields, at least some of said fields
containing said color mixing interval, and said timing regulation device
sets the accumulation interval in at least some of said fields that
contain said color mixing interval.
8. The image processing system of claim 1, wherein said imaging element
discards any charge that accumulates in said imaging element at times
other than during said accumulation interval.
9. The image processing system of claim 1, wherein said imaging element
discards any charge that accumulates in said imaging element during said
color mixing intervals.
10. The image processing system of claim 1, wherein said timing regulation
device adjusts color balance by setting the accumulation interval of said
imaging element to a different accumulation interval for each one of said
plurality of different color images.
11. The image processing system of claim 1, wherein said timing regulation
device includes:
an initial accumulation interval setting device that sets the accumulation
interval of said imaging element to a predetermined interval for each of
the plurality of color images according to a color balance setting
instruction;
a calculating device that generates a correcting signal based on the image
signal output by the imaging element for each of the plurality of color
images after the setting by said initial accumulation interval setting
device; and
an adjusted accumulation interval setting device that adjusts color balance
based on the correcting signal by adjusting the accumulation interval for
each of the plurality of color images.
12. The image processing system of claim 11, wherein said predetermined
interval is the same for each of said plurality of color images.
13. The image processing system of claim 11, wherein said predetermined
interval is a predetermined interval ratio.
14. The image processing system of claim 1, wherein said color filter is a
movable color filter, and further comprising a movement sensor that senses
movement of said movable color filter and generates a movement signal,
said timing regulation device determining said color mixing intervals and
thereby setting the accumulation interval of the imaging element based on
said movement signal.
15. An image processing system for a color television camera comprising:
an imaging element that receives a plurality of different color images and
outputs image signals based on an amount of charge that accumulates in
said imaging element during an accumulation interval while said imaging
element is receiving each of said plurality of different color images; and
a timing regulation device that sets the accumulation interval of the
imaging element to a different accumulation interval for each of said
different color images to achieve color balance.
16. The image processing system of claim 15, wherein said timing regulation
device includes:
an initial accumulation interval setting device that sets the accumulation
interval of said imaging element to a predetermined interval for each of
the plurality of color images according to a color balance setting
instruction;
a calculating device that generates a correcting signal based on the image
signal output by the imaging element for each of the plurality of color
images after the setting by said initial accumulation interval setting
device; and
an adjusted accumulation interval setting device that adjusts color balance
based on the correcting signal by adjusting the accumulation interval for
each of the plurality of color images from said predetermined interval to
said different accumulation intervals.
17. The image processing system of claim 15, further comprising a color
filter that separates light from an object being photographed into said
plurality of color images having different colors, which are received by
said imaging element.
18. An image processing system for a color television camera comprising:
color separation means for separating light from an object being
photographed into a plurality of color images having different colors;
imaging means for receiving the plurality of color images from the color
separation means and for outputting image signals based on an amount of
charge accumulated by said imaging means during an accumulation interval
while said imaging means is receiving each of said plurality of color
images; and
timing regulation means for setting the accumulation interval of the
imaging means based on color mixing intervals during which more than one
of said color images simultaneously are received by said imaging means.
19. The image processing system of claim 18, wherein said timing regulation
means sets the accumulation interval of the imaging means to correspond to
an interval other than said color mixing intervals.
20. The image processing system of claim 18, wherein said imaging means
accumulates charge in a series of fields, and said timing regulation means
sets the accumulation interval in all of said fields.
21. The image processing system of claim 20, wherein at least some of said
fields contain said color mixing interval.
22. The image processing system of claim 18, wherein said timing regulation
means includes color balance adjusting means for adjusting color balance
by setting the accumulation interval of said imaging means to a different
accumulation interval for each one of said plurality of different color
images.
23. The image processing system of claim 22, wherein said color balance
adjusting means includes:
initial accumulation interval setting means for setting the accumulation
interval of said imaging means to a predetermined interval for each of the
plurality of color images according to a color balance setting
instruction;
calculating means for calculating a correcting signal based on the image
signal output by the imaging means for each of the plurality of color
images after the setting to said predetermined interval by said initial
accumulation interval setting means; and
adjusted accumulation interval setting means for adjusting the color
balance based on the correcting signal by adjusting the accumulation
interval for each of the plurality of color images.
24. The image processing system of claim 18, wherein said color separation
means is a movable color filter, and further comprising a movement sensing
means for sensing movement of said movable color filter to generate a
movement signal, said timing regulation means determining said color
mixing intervals and thereby setting the accumulation interval of the
imaging means based on said movement signal.
25. An image processing system for a color television camera comprising:
imaging means for receiving a plurality of different color images and for
outputting image signals based on an amount of charge accumulated by said
imaging means during an accumulation interval while said imaging means is
receiving each of said plurality of different color images; and
timing regulation means for setting the accumulation interval of the
imaging means to a different accumulation interval for each of said
different color images to achieve color balance.
26. The image processing system of claim 25, wherein said timing regulation
means includes:
initial accumulation interval setting means for setting the accumulation
interval of said imaging means to a predetermined interval for each of the
plurality of color images according to a color balance setting
instruction;
calculating means for calculating a correcting signal based on the image
signal output by the imaging means for each of the plurality of color
images after the setting to the predetermined interval by said initial
accumulation interval setting means; and
adjusted accumulation interval setting means for adjusting the color
balance based on the correcting signal by adjusting the accumulation
interval for each of the plurality of color images from said predetermined
interval to said different accumulation intervals.
27. A method of processing images in a color television camera comprising:
separating light from an object being photographed into a plurality of
color images having different colors;
accumulating charge in an imaging element by exposing the imaging element
to the plurality of color images, the imaging element outputting image
signals based on the amount of charge accumulated by the imaging element
during an accumulation interval; and
setting the accumulation interval based on color mixing intervals during
which more than one of the color images simultaneously are received by the
imaging element.
28. The method of claim 27, wherein the light from the object is separated
by a color filter that includes color boundaries between different color
portions of said color filter, said color mixing interval being an
interval during which one of said color boundaries is passing over said
imaging element.
29. The method of claim 27, wherein said accumulation interval is set to
correspond to an interval other than said color mixing intervals.
30. The method of claim 27, wherein the imaging element accumulates charge
in a series of fields, and said accumulation interval is set to occur in
all of said fields.
31. The method of claim 27, wherein the imaging element accumulates charge
in a series of fields, at least some of said fields containing said color
mixing interval, and said accumulation interval is set to occur in at
least some of said fields that contain said color mixing interval.
32. The method of claim 27, further comprising discarding any charge that
accumulates in the imaging element at times other than during said
accumulation interval.
33. The method of claim 27, further comprising adjusting color balance by
setting the accumulation interval of the imaging element to a different
accumulation interval for each one of said plurality of different color
images.
34. The method of claim 33, wherein adjusting the color balance includes:
setting the accumulation interval of the imaging element to a predetermined
interval for each of the plurality of color images according to a color
balance setting instruction;
calculating a correcting signal based on the image signal output by the
imaging element for each of the plurality of color images after the
accumulation interval is set to said predetermined interval; and
adjusting the color balance based on the correcting signal by adjusting the
accumulation interval for each of the plurality of color images.
35. The method of claim 28, wherein said color filter is a movable color
filter, and further comprising sensing movement of said movable color
filter, and wherein the color mixing intervals are determined, and thereby
the accumulation interval of the imaging element is set, based on the
sensed movement of the movable color filter.
36. A method of processing images in a color television camera comprising:
accumulating charge in an imaging element by exposing the imaging element
to a plurality of color images, the imaging element outputting image
signals based on the amount of charge accumulated by the imaging element
during an accumulation interval; and
setting the accumulation interval of the imaging element to a different
accumulation interval for each of said different color images to achieve
color balance.
37. The method of claim 36, wherein setting the accumulation interval
includes:
setting the accumulation interval of said imaging element to a
predetermined interval for each of the plurality of color images according
to a color balance setting instruction;
calculating a correcting signal based on the image signal output by the
imaging element for each of the plurality of color images after the
accumulation interval is set to said initial predetermined interval; and
adjusting the color balance based on the correcting signal by adjusting the
accumulation interval for each of the plurality of color images from said
predetermined interval to said different accumulation intervals. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color mixing prevention method and
device for a field-sequential color television camera that uses a rotating
filter wheel with side-by-side color filters to sequentially filter
imaging light. The present invention also relates to a color balance
setting method and device for a field-sequential color television camera
that maximizes use of the fields and adjusts the time intervals for charge
accumulation to achieve color balance in lieu of complexities in the
signal executing circuit system.
2. Description of Related Art
In general, with color television cameras that use a solid state imaging
element or the like, it is necessary to adjust the white balance in order
to correct discrepancies in the color balance that occur through
differences in color temperature or the like from the light source. This
type of white balance adjustment has conventionally imaged a white object,
for example, or taken light from a white light source into the camera, and
adjusted the gain of each color through a white balance circuit located in
the movie signal executing circuit of the camera. It has thus been
possible, through adjusting the white balance, to image a white object,
for example, with the proper degree of whiteness.
FIG. 6 shows the action timing of a prior art field-sequential color
television camera that uses a solid state imaging element and a color
separating color filter. With the field-sequential color television camera
that corresponds to FIG. 6, one revolution of a rotary color filter with
the three filter domains of G (green), B (blue), and R (red) is
synchronized with the time interval for one cycle of 9 field divisions of
the solid state imaging element. In the time interval from field 1 to
field 3 the green field domain passes the imaging surface of the solid
state imaging element. The blue domain passes during the interval from
fields 4-6, and the red domain passes during the interval from fields 7-9.
The solid state imaging element does not accumulate light from the object
being photographed during all of the field intervals, but transmits the
charge accumulated at the end of the fields to the surface image executing
circuit of the camera. In the surface image signal executing circuit, a
signal corresponding to the transmitted charge for each color is recorded,
the signals recorded for each color being composed according to the
desired ratios, and color image signals being formed and output.
With the above-mentioned prior-art field-sequential color television
camera, two different color signals are projected onto the imaging surface
and accumulated during the interval TM3, during which the color boundaries
of the color separating filter pass over the imaging surface of the
imaging element, resulting in color mixing. Any charge accumulating during
the color mixing interval is not useful because it results from two
different colors. With prior-art field-sequential color television
cameras, the surface image accumulation is not carried out during the
entire field time interval of the solid state imaging element when the
field time interval includes color mixing. The surface image signals of
fields that include the color mixing time interval TM3 are discarded, and
ultimately cannot be used in the formation of the color image signal. For
example, referring to FIG. 6, the data from fields 1, 4 and 7 would be
discarded. U.S. Pat. No. 4,851,899, the disclosure of which is
incorporated herein by reference, discloses such a prior art system.
Therefore, high-speed image input cannot be performed because the imaging
signals from fields that include color mixing, during which the color
boundaries of the color separating filter pass over the imaging surface,
are ignored, and only the imaging signals from the other fields are used.
Additionally, such color television cameras require white balance circuits
to adjust the gain of each color in the image signal executing circuit for
the white balance. Such circuits complicate the construction of the camera
circuits and hinder the development of smaller, lighter color television
cameras. Because the signal level of image signals prior to the white
balance execution in a prior-art color television camera varies widely
with each color and because the signal executing circuits cross a wide
dynamic range and must move stably and precisely, the circuits becomes
very complicated and costly.
SUMMARY OF THE INVENTION
An object of the present invention is, with a field-sequential or other
type of color television camera, to make possible the effective use of
imaging element signals from fields that include color mixing intervals,
and to make possible a higher-speed surface image input.
Another object of the present invention is, with a field-sequential or
other type of color television camera, to make possible a precise color
balance adjustment using a simple circuit construction, without reliance
on only the white balance circuit in the signal executing system.
Another object of the present invention is, with a field-sequential or
other type of color television camera, to make possible the adjustment of
color balance without imparting a large load to the signal executing
circuit system, and to make possible high-speed image input.
Another object of the present invention is, with a field-sequential or
other type of color television camera, to automatically perform a color
balance adjustment using a simple circuit construction, without relying on
the white balance circuit in the signal executing system.
Another object of the present invention is, on a field-sequential or other
type of color television camera, to make possible an automatic color
balance adjustment without imparting a large load to the signal executing
circuit system, and to make possible a high-speed image input.
In order to accomplish the above and other objects, embodiments of the
present invention provide a color mixing prevention device for a
field-sequential color television camera in which charge does not begin to
accumulate in a solid state imaging element until after the color mixing
interval of a given field is completed. Any charge generated in the solid
state imaging element during color mixing is discarded.
The operation of the present invention prevents charge accumulation for
transmission during the color mixing time interval, during which the color
boundaries of the color filter pass over the solid state imaging element
at least within one field interval. A charge is accumulated for
transmission only during intervals other than the color mixing time
intervals. Since intervals other than the color mixing time intervals of
each field are used, an efficient high-speed imaging system becomes
possible.
CCDs, for example, may be used in the solid state imaging element. Charge
accumulation for transmission during color mixing can be avoided by
regulating each timing pulse from the drive circuit of the solid state
imaging device. Thus, color image signals with no color mixing can be
rapidly obtained.
In order to further accomplish objectives stated above, the present
invention provides a charge accumulation regulation device that adjusts
the color balance by setting the time of charge accumulation of the solid
state imaging element for each filed for each color.
No charge is accumulated for transmission at least during the color mixing
time intervals, during which the color boundaries of the color filter pass
over the solid state imaging element.
In first and second embodiments of the invention, the start of charge
accumulation is set to coincide with the end of the color mixing interval
for the first field of each color of the color filter wheel. In third,
fourth and fifth embodiments of the invention, color balance is achieved
by adjusting within the field time intervals other than the color mixing
time interval the accumulation time intervals for each color.
The present invention provides a method of setting the color balance on a
field-sequential color television camera, comprising color separating the
light from the object being photographed using a color filter, imaging the
light from the object being photographed that has been separated by the
color filter using a solid state imaging device that has regulated charge
accumulation, and adjusting the color balance by setting the charge
accumulation time of the solid state imaging element in the fields for
each color.
In the third and fourth embodiments of the present invention, a timing
regulation signal from the signal executing circuit adjusts the charge
accumulation time interval of the solid state imaging device to correct
the imbalance of the gain for each color caused by differences in light
source color temperatures or the like, and adjust the color balance.
Therefore it is not necessary to use a complex white balance circuit,
making it possible to make the color television camera smaller and
lighter.
In particular, with a field-sequential color camera that color separates
the light from the object being photographed by means of a color filter,
the charge accumulated on the surface element is swept up (that is,
discarded) during the color mixing time interval, during which the color
boundaries of the color filter pass over the surface of the solid state
imaging element, and the color balance can be adjusted within time
intervals other than the color mixing time interval by varying the
accumulation time for each color. There is no need to discard the entire
signal from fields that include the color mixing time, making possible
high-speed surface image input. It is also possible to perform a suitable
color balance adjustment without using a white balance circuit.
In addition, with the third and fourth embodiments of the present
invention, since the signal level of the signal circuits prior to the
white balance execution do not fluctuate widely from each color, and since
the level fluctuations for each color have been already removed by the
step that has been output from the solid state imaging device, the load to
the signal executing circuit system is lightened, and the construction of
the circuit system can be simplified and the cost lowered.
In a fifth embodiment of the present invention, similar to the third and
fourth embodiments of the invention, a color balance setting device is
described in more detail. In the fifth embodiment of the invention, a
charge accumulating initial setting device sets the surface image charge
accumulation time of the solid state imaging element corresponding to each
color to the same or to a predetermined interval, according to color
balance setting instructions. A calculation device separate from the
signal executing circuit, obtains a correcting signal, based on the signal
value for each color obtained from the solid state imaging element after
setting by the initial charge accumulation interval times. A color balance
setting device adjusts the surface image charge accumulation time interval
for each color of the solid state imaging device based on the correcting
signal.
In addition, with the present invention, since the signal level of the
signal circuits prior to the white balance execution does not fluctuate
widely for each color, and since the level fluctuations for each color
have been already removed by the step that has been output from the solid
state imaging device, the load on the signal executing circuit system is
lightened, and the construction of the circuit system can be simplified
and the cost lowered.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in conjunction with the following drawings
in which like reference numerals designate like elements and wherein:
FIG. 1 is a block diagram showing the construction of a field-sequential
color television camera that includes a color mixing prevention device
according to first and second embodiments of the present invention;
FIG. 2 shows the construction of a color separating filter for use on the
color television cameras of FIG. 1, FIG. 7 and FIG. 9.
FIG. 3 (a) is a partial plan view showing a sample construction of the
solid state imaging element used with the color television cameras of FIG.
1, FIG. 7 and FIG. 9;
FIG. 3 (b) is a signal waveform diagram showing the regulating pulse
supplied to the solid state imaging element;
FIG. 4 (a) is a signal waveform diagram of a first embodiment of the
invention using a three-field color filter in the color television camera
of FIG. 1;
FIG. 4 (b) is a signal waveform diagram of a second embodiment of the
invention using a six-field color filter in the color television camera of
FIG. 1;
FIG. 5(a1) is a descriptive waveform diagram showing image signal outputs
with a three-field color filter using charge accumulation during the color
mixing time intervals;
FIG. 5(a2) is a descriptive waveform diagram showing image signal outputs
of the color television camera of FIG. 1 using a three-field color filter;
FIG. 5(b1) is a descriptive waveform diagram showing image signal outputs
with a six-field color filter using charge accumulation during the color
mixing time intervals;
FIG. 5(b2) is a descriptive waveform diagram showing image signal outputs
of the color television camera of FIG. 1 using a six-field color filter;
FIG. 6 is a waveform diagram describing the action of a prior-art
field-sequential color television camera;
FIG. 7 is a block diagram showing the construction of a field-sequential
color television camera that includes a color balance setting device
according to third and fourth embodiments of the present invention;
FIG. 8(a) is a signal waveform diagram of the third embodiment of the
invention using a three-field color filter in the color television camera
of FIG. 7;
FIG. 8(b) is a signal waveform diagram of the fourth embodiment of the
invention using a six-field color filter in the color television cameras
of FIG. 7.
FIG. 9 is a block diagram showing the construction of a field-sequential
color television camera that includes a color balance setting device
according to a fifth embodiment of the present invention;
FIG. 10(a) is a signal waveform diagram showing the color balance setting
action with the color television camera of FIG. 9 before the operation of
the color balance setting switch;
FIG. 10(b) is a signal waveform diagram showing the color balance setting
action with the color television camera of FIG. 9 directly after the
operation of the color balance setting switch; and
FIG. 10(c) is a signal waveform diagram showing the color balance setting
action with the color television camera of FIG. 9 after the color balance
setting has been completed.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Embodiments of the present invention are described hereafter, with
reference to the drawings. FIG. 1 shows the construction of a
field-sequential color television camera that relates to an embodiment of
the present invention. The device in FIG. 1 comprises an image composing
lens 2 that composes an image from the light from the object 1 being
photographed onto the imaging surface of a solid state imaging element 4.
A color filter 3 for separating the colors is positioned between the image
composing lens 2 and the imaging element 4 and is rotated. The imaging
element 4 of the device of FIG. 1 is comprised, e.g., of charge coupled
devices (CCDs).
The device of FIG. 1 is also equipped with a drive circuit 5 and a
synchronized signal generating circuit 6, which supplies a drive pulse to
the imaging element 4, an amplifier 7 that amplifies the imaging signal
output from the imaging element 4, and a signal executing circuit 9 that
receives the imaging signal output from the amplifier 7 and outputs the
desired color movie signal. In addition, a motor or other type of color
filter driving device 8 is provided to rotate the rotary color filter 3
and a rotation detector 10, such as, for example, a photo interrupter, is
provided to detect the rotation of the rotary color filter. The output of
the rotation detector 10 is input to the synchronized signal generating
circuit 6.
FIG. 2 shows the construction of the color separating rotary color filter 3
that can be used with the present invention. The color filter 3 in FIG. 2
is divided into three filter domains 11, 12, and 13, each with an angular
span of 120.degree. which pass colors green, blue and red, respectively,
as indicated by the letters G, B and R. Filter domain 11 allows only green
light to pass, filter domain 12 allows only blue light to pass, and filter
domain 13 allows only red light to pass. The color filter 3 is
synchronized with the scanning timing of the solid state imaging element 4
and rotated about the axis of rotation 14 by the color filter driving
device 8. In FIG. 2, the relative positions of the rotary color filter 3
and the described solid state imaging element are shown. Thus, when the
rotary color filter 3 turns in the direction shown by the arrow, the time
interval during which the boundaries between the filter domains 11, 12,
and 13 pass the imaging surface of the solid state imaging device becomes
the color mixing time interval.
An opaque region 15 is provided near the edge of the color filter 3 on the
border of filter domains 11 and 12. This opaque region 15 is used to
obtain a signal through the rotation detector 10 of FIG. 1 indicating the
rotational position of the color filter 3.
The imaging element 4 includes charge accumulating type surface elements in
which the accumulating time can be regulated, and in which a reset action
is possible. FIG. 3 (a) shows a construction of the solid state imaging
element 4 that can be used with the field-sequential color television
camera of FIG. 1, and that provides for adjustment of the charge
accumulation times. The solid state imaging element 4 in FIG. 3(a)
comprises multiple light receiving elements 16, such as photodiodes,
arranged in a two-dimensional matrix, vertically transmitting CCDs 17 that
receive the charge signals that correspond to the light from the object
being photographed from the photo diodes 16 via field shift gates (not
shown) and transmit the charge signals in the vertical direction (top to
bottom in the drawing), and CCDs 18 that sequentially horizontally
transmit the movie image signals from the surface elements that have been
sequentially transmitted from each vertically transmitting CCD 17. An
amplifier 19 receives the output of the horizontally transmitting CCDs 18.
With this type of solid state imaging element, the light from the object
being photographed shines on each surface element (each photo diode 16),
and charges that correspond to the intensity of the light from the object
being photographed in each position of the surface element are transmitted
through a field shift gate (not shown) to the vertically transmitting CCDs
17 that are adjacent to each photo diode 16 between adjacent fields. The
vertically transmitting CCDs 17 sequentially transmit each surface image
charge that has been input from the photo diodes 16 to the horizontally
transmitting CCDs 18, which sequentially transmit the charges supplied
from the vertically transmitting CCDs 17 in the horizontal direction, and
output them as movie image signal outputs via the amplifier 19.
This type of solid state imaging element is driven so that surface element
information from one field portion for each cycle of a field shift gate
pulse b is obtained, as shown in FIG. 3(b). The accumulation of surface
element charge in each photo diode 16 begins, for example, at the point of
descent of the accumulation commencement pulse a, and continues until the
point of ascent of the field shift gate pulse. In other words, the
interval from the descent of the accumulation commencement pulse a to the
ascent of the field shift gate pulse b becomes the accumulation interval
for the light from the object being photographed. Thus, in the interval
prior to the accumulation interval in one field, the surface element
charge is swept away without being accumulated. The surface element charge
accumulated on each surface element during the accumulation interval is
output after the completion of the accumulation interval, or at the end of
each field.
The field-sequential color television camera of the present invention is
controlled so that charges are not accumulated for transmission during the
color mixing intervals. In FIG. 1, the light from the object being
photographed 1 is composed into an image on the imaging surface of the
solid state imaging element 4 by the image composing lens 2. The imaging
element drive circuit 5 inputs a drive pulse to the solid state imaging
element 4 by means of the fixed field cycle, based on the regulating
signal from the synchronized signal generating circuit 6, and prevents
charge accumulation for transmission by sweeping up the charge accumulated
during the color mixing intervals, and causes the accumulation and
transmitting actions described above to be carried out. A regulating
signal from the synchronized signal generating circuit 6 is also input to
the color filter driving device 8, and the rotation of the color filter 3
and the scanning of the solid state imaging element 4 are synchronized.
The opaque region 15 of the rotary color filter 3 is detected by the
rotation detector 10, which inputs information relating to the rotary
position of the rotary color filter to the synchronized signal generating
circuit 6. The synchronized signal generating circuit 6 determines the
color mixing interval, or the interval during which the color boundaries
of the rotary color filter 3 pass over the solid state imaging element 4,
from the rotary position of the rotary color filter 3, and the position of
the imaging surface of the solid state imaging element, based on the
signal from the rotation detector 10. The synchronized signal output
circuit 6 generates a signal that indicates this color mixing interval to
the imaging element drive circuit 5. The imaging element drive circuit 5
generates an accumulation commencement pulse after the color mixing
interval has ended, based on the signal from the synchronized signal
generating circuit 6, and inputs it to the solid state imaging element 4.
The solid state imaging element 4 operates to sweep up charge accumulation
until the accumulation commencement pulse is input. When the accumulation
commencement pulse is input from the imaging element drive circuit 5, the
surface image charge begins to accumulate. This accumulation of surface
image charge continues until the end of each field interval, and the
charge accumulated at the end of these intervals is transmitted.
The action of the solid state imaging element is next described with
reference to FIG. 4(a) and FIG. 4(b). FIG. 4 (a) shows fields using a
three-field rotary color filter. As described above, the rotation of the
rotary color filter is synchronized with the scanning of the solid state
imaging element. One color of the color filter has a pass time at least as
long as one field interval. In FIG. 4 (a), the beginning time of each
field is designated as the color mixing interval TM1. The charges
accumulated in the surface elements of the imaging element during this
color mixing interval are removed by sweeping up the charges. The
accumulation commencement pulse is then given at the end of the color
mixing interval TM1, and accumulation of the surface element charge
begins. Thus the accumulation action is performed only in intervals in
which the same color of light is shining on all surface elements of the
solid state imaging element. This accumulation action is continued until
the end of the field interval, transmitted to the exterior at the end of
the field intervals, and then output. In this manner, it is possible to
use the surface image input from each field, making high-speed imaging
possible.
The setting of the color mixing interval, and therefore the setting of the
accumulation commencement timing, are determined from the structure of the
rotary color filter, the relative positions of the axis of rotation 14 of
the filter 3 and the imaging element 4, the image surface size of the
imaging element 4, the speed of rotation of the color filter 3, and any
other relevant variables.
A six-field rotary color filter may also be used and its field scan
operation is described with reference to FIG. 4(b). In this case, green
(G) light from the object is imaged in fields 1 and 2, blue (B) light is
imaged in fields 3 and 4, and red (R) light is imaged in fields 5 and 6.
Color mixing intervals TM2 are present at the beginning of fields 1, 3,
and 5. After these color intervals TM2 are finished, an accumulation
commencement pulse is output, and the accumulation of surface image
information begins. Fields 2, 4, and 6 do not include color mixing
intervals, but, since they each have the same accumulation times as the
fields directly preceding them (fields 1, 3, and 5), the timing of the
accumulation commencement pulse is the same as when there is a color
mixing interval TM2 at the beginning of each field. With this example
also, the fields that included color mixing times could be used, making
high-speed imaging possible.
FIG. 5(a1) and FIG. 5(a2) show the result of the regulation of the surface
image accumulation interval described above. Both FIG. 5 (a1) and FIG.
(a2) relate to cameras in which the color filter is rotated with the same
timing shown in FIG. 4 (a). In the case that an accumulation commencement
pulse is not given, unlike the present invention, color mixed signals that
differ from the pure G, B, and R signals are output, as shown in FIG.
5(a1), because the surface image light accumulation is carried out during
the color mixing interval in which the boundaries of the color separating
filter pass the imaging element domain, or, in other words, the beginning
interval TM1 of each field. In contrast, in the present invention, since
an accumulation commencement pulse is given at the end of the color mixing
interval (i.e., shutter regulation is performed), a charge does not
accumulate during the interval in which the color separating filter
boundaries pass the imaging element. As shown in FIG. 5(a2), an image
signal with no color mixing is output in each field.
FIG. 5(b1) and FIG. 5(b2) correspond to FIG. 4 (b), a color mixing interval
TM2 being present at the beginning of the first field of each two
continuous color fields. Because of this color mixing interval, a color
mixed image signal is output for the color mixing interval, as shown in
FIG. 5(b1), unlike the present invention. In contrast, in the present
invention, image signals with no color mixing can be obtained from each
field as shown in FIG. 5(b2).
As described above, by using the present invention, extremely high-quality
color images with no color mixing are possible because the signal charges
accumulated on the surface elements of the solid state imaging element are
removed during the color mixing interval in which the color boundaries of
the color filter pass over the imaging domain of the solid state imaging
element. In addition, since the effective imaging actions can be performed
in every field, an extremely rapid image input is possible.
Third and fourth embodiments of the present invention are described
hereafter, with reference to FIG. 7, FIG. 8a and FIG. 8b. FIG. 7 shows the
construction of a field-sequential color television camera that relates to
those embodiments of the present invention. In FIG. 7, the same reference
numerals have been used to refer to the same elements, which remain
unchanged from those of FIG. 1.
The action of a field-sequential color television camera of FIG. 7 is next
described, centering on the color balance adjustment action. In FI | | |
