Ex parte Sekiguchi

Board of Patent Appeals and Interferences

Aug 6, 1997

07996393 (B.P.A.I. Aug. 6, 1997)

Application for patent filed December 23, 1992, entitled "Solid State Imaging Device,"1
which claims the priority benefit under 35 U.S.C. § 119 of Japanese Application 03-345089, filed
December 26, 1991.
- 1 -
THIS OPINION WAS NOT WRITTEN FOR PUBLICATION
The opinion in support of the decision being entered
today (1) was not written for publication in a law
journal and (2) is not binding precedent of the Board.
_______________
Paper No. 17
UNITED STATES PATENT AND TRADEMARK OFFICE

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES

Ex parte KATSUO SEKIGUCHI

Appeal No. 95-4788
Application 07/996,3931

HEARD: July 17, 1997

Before KRASS, BARRETT, and TORCZON, Administrative Patent Judges.
BARRETT, Administrative Patent Judge.
DECISION ON APPEAL
Appeal No. 95-4788
Application 07/996,393
- 2 -
This is a decision on appeal under 35 U.S.C. § 134 from the final rejection of claims 3-5,
all of the claims pending in the application. Claim 1 and 2 have been cancelled.
The invention is directed to a solid state imaging device as may be understood from claim
3 reproduced below.
3. A solid state imaging device comprising: an array of photosensitive elements
for storing signal charges, a plurality of vertical shift registers for storing the signal charges
transferred from the photosensitive elements, charge storage sections for storing one field
of signal charges transferred from the respective vertical shift registers, a horizontal shift
register for storing one line of signal charges transferred thereto successively at time
intervals from the charge storage sections, a timing generator for producing clock pulses
for driving the vertical shift registers to transfer the signal charges from the vertical shift
registers to the charge storage sections and to sweep residual charges from the vertical
shift registers, a driver for amplifying the clock pulses fed thereto from the timing
generator, the driver having a variable amplification factor, control means for controlling
the amplification factor of the driver so as to provide a smaller amplitude for the clock
pulses used to sweep the residual charges than for the clock pulses used to transfer the
signal charges, wherein the driver has a smaller amplification factor when it receives a
smaller reference voltage, and wherein the control means includes means for producing a
first reference voltage and a second reference voltage which is less than the first reference
voltage, switching means for selectively coupling one of the first and second reference
voltages to the driver, and wherein the switching means includes means for coupling the
first reference voltage to the driver when the signal charges are to be transferred from the
vertical shift registers to the respective charge storage sections and for coupling the second
reference voltage to the driver when the residual charges are to be swept from the vertical
shift registers.
The examiner relies on the admitted prior art and the following reference:
Howard et al. (Howard) 4,845,482 July 4, 1989
The admitted prior art is described in the specification at page 3, line 13 to page 6, line 14
with respect to figures 3-5. In the prior art of figures 4 and 5, "[t]he power circuit 26 provides
Appeal No. 95-4788
Application 07/996,393
- 3 -
a reference voltage V1 to determine the amplification factor of the driver 22 and, thus, the
amplitude of the driving pulse signals to the solid state image sensor 10" (specification, page 4,
lines 20-23).
Howard discloses a method for eliminating crosstalk due to capacitive coupling in a thin
film transistor/liquid crystal display (TFT/LCD). A matrix of liquid crystal cells is controlled by
means of an x-y array of thin film transistors, one per cell, which can be switched on, a row at a
time to control the charge on the row of liquid crystal electrodes. As each row of transistors is
turned on by a pulse applied to the gate lines, the voltages of vertical data electrodes are
transferred to cell capacitors. Crosstalk can occur by capacitive coupling between the data
electrodes 22 and 24 and the transparent liquid crystal electrode 26 (figure 2). In conventional
operation, the row gate electrodes are strobed in sequence, each being activated once per frame
T, for an interval of approximately T/N, where N is the number of rows in the display (column 3,
lines 55-58). Each column electrode then has a repetitive sequence of voltages V applied to it,i
each for a time interval T/N in synchronization with the gate pulses (column 3, lines 59-61).
Because of this serial sequence of data voltages, a given liquid crystal cell capacitor will be
subjected to a fraction of all the voltages in the column in sequence, with the fraction depending
on the size of the coupling capacitor relative to the cell capacitance (column 3, lines 27-34).
Howard applies the gate pulse for a fraction of the line time T/N, e.g., T/2N and changes
the sequence of data line voltages applied to the source electrode 38 in figure 3 to V , V -V , V ,i M i i+1
V -V , etc., where V is a fixed voltage (which could be zero) (column 3, lines 61-68). ThisM i+1 M
Appeal No. 95-4788
Application 07/996,393
- 4 -
sequence corresponds to data, data complement, data, data complement, etc., with the gate pulses
synchronized to the intervals of the data voltage for transferring charge to the cell capacitance 40
and the data complement pulses driving the column electrodes when there are no gate pulses
active, thereby compensating for the effect of crosstalk via capacitive coupling by the cell
capacitances 42 and 44 (column 3, line 66 to column 4, lines 1-9). That is, the data signal is
applied to one of the data lines when the gating signal is applied and the crosstalk compensation
signal is applied when the gating signal is not applied. A variation is to trade a longer duration
data signal time for a shorter duration compensation signal with increased amplitude, e.g., the gate
signal being ON for a time 0.8T/N during which period from 0 to 0.8T/N the data signal is applied
and the gate signal being off during the time 0.8T/N to T/N during which period the crosstalk
compensation of amplitude 2(V -V ) is applied.M i
Claims 3-5 stand rejected under 35 U.S.C. § 103 as being unpatentable over the admitted
prior art and Howard. The examiner finds that Howard teaches a circuit which produces two
voltage levels (e.g., V and V -V shown in figure 5) at the output of the analog toggle 48. Thei M i
examiner states (Examiner's Answer, page 5):
It is well known in the art of solid state imaging that for sweep and transfer clock pulses
generated during the vertical blanking period, the power dissipation caused by the high
repetition rates that are required can cause the generation of undesirable heat contributing
to an increase in unwanted charges due to thermal noise. It is also standard practice in the
design of solid state imagers, as seen in the admitted prior art device, to provide a means
for varying the amplitude of clock pulse voltages. Thus, it would have been obvious to
one of ordinary skill in the art at the time the invention was made to control the variations
in the prior art clock pulse voltages in accordance with the dual-voltage control means
disclosed in Howard et al. in order to provide different clock voltages for the respective
Appeal No. 95-4788
Application 07/996,393
- 5 -
sweep and transfer functions of a solid state imaging device so that more control could be
exercised over minimizing the thermal noise generated by these pulses.
The examiner further states (Examiner's Answer, page 6):
Howard et al. do not specify that the larger voltage be used when the refresh operation is
performed. However, it is well known in the art that, using an appropriate polarity, the
larger the voltage applied to an electrode in a CCD, the greater the amount of charge that
can be transferred by the device. Also, the amount of residual charge which needs to be
swept out is smaller than the amount of charge comprising the signal. Thus, it would have
been obvious to one of ordinary skill in the art at the time the invention was made to use
the larger of the two voltages of Howard et al. to clock the transfer of signal charges and
the smaller voltage to sweep out the residual charges.
OPINION
We reverse.
"It is well established that before a conclusion of obviousness may be made based on a
combination of references, there must have been a reason, suggestion, or motivation to lead an
inventor to combine those references." Pro-Mold and Tool Co. v. Great Lakes Plastics Inc.,
75 F.3d 1568, 1573, 37 USPQ2d 1626, 1629 (Fed. Cir. 1996). A suggestion to combine "may
come expressly from the references themselves. It may come from knowledge of those skilled in
the art that certain references, or disclosures in the references, are known to be of special interest
or importance in the particular field. It may also come from the nature of a problem to be solved,
leading inventors to look to references relating to possible solutions to that problem." Id. at 1573,
37 USPQ2d at 1630 (citations omitted).
We find no motivation to modify the admitted prior art to produce the claimed invention.
Neither appellant's admitted prior art nor Howard suggest using different voltage levels for
Appeal No. 95-4788
Application 07/996,393
- 6 -
sweeping and for transferring and that reducing the amplitude of the vertical transfer clock pulses
will sufficiently sweep the residual charges. The admitted prior art discloses that conventional
imaging devices generate a great amount of power and heat in sweeping and transferring which
have an adverse effect on the characteristics of the sensor (specification, para. bridging pages 5-6).
Therefore, we agree with the examiner's finding that "[i]t is well known in the art of solid state
imaging that for sweep and transfer clock pulses generated during the vertical blanking period, the
power dissipation caused by the high repetition rates that are required can cause the generation
of undesirable heat contributing to an increase in unwanted charges due to thermal noise"
(Examiner's Answer, page 5). However, the admitted prior art does not suggest reducing the
voltage level used in sweeping to lower the overall power, and therefore the heat and undesired
characteristics, as a solution to the problem.
The admitted prior art in figure 4 discloses a driver 22 whose amplification factor is
controlled by a reference voltage from power circuit 26 (specification, page 4, lines 10-23). The
examiner's finding that "[i]t is also standard practice in the design of solid state imagers, as seen
in the admitted prior art device, to provide a means for varying the amplitude of clock pulse
voltages" (Examiner's Answer, page 5) is correct to the extent that the structure in figure 4
determines the amplitude in accordance with a reference voltage. However, the admitted prior
art does not suggest that the reference voltage is varied or that it takes on other than a single
value. While the admitted prior art driver may be capable of being modified to provide two
different amplifications the way appellant's apparatus is claimed, there must be a suggestion or
Appeal No. 95-4788
Application 07/996,393
- 7 -
motivation in the references to do so. See In re Mills, 916 F.2d 680, 682, 16 USPQ2d 1430, 1432
(Fed. Cir. 1990) ("While Mathis' apparatus may be capable of being modified to run the way Mills'
apparatus is claimed, there must be a suggestion or motivation in the reference to do so.");
In re Gordon, 733 F.2d 900, 902, 221 USPQ 1125, 1127 (Fed. Cir. 1984) ("The mere fact that
the prior art could be so modified would not have made the modification obvious unless the prior
art suggested the desirability of the modification.'). We see no such suggestion in the admitted
prior art or Howard.
The fact that Howard discloses structure producing two voltage levels does not suggest
using different voltage levels for sweeping and for transferring. The two voltage levels in Howard
are used to compensate for crosstalk in a TFT/LCD, not to reduce power and heat in a solid state
charge coupled device (CCD). We fail to see the motivation for using the two voltage levels in
Howard for a completely different purpose in the admitted prior art. The examiner attempts to
show that CCDs are analogous to TFT/LCDs because both use capacitive cells arranged in an x-y
matrix (Examiner's Answer, pages 8-10 and 14). Assuming there are analogies that can be drawn,
we do not see how Howard's technique of applying the data signal (one voltage) to one of the data
lines when the gating signal is applied and applying the crosstalk compensation signal (the second
voltage) when the gating signal is not applied suggests the claimed operation of applying one
voltage during a sequence of sweeping clock pulses and applying another voltage during a
sequence of transferring clock pulses. Howard does not involve sweeping away residual charges.
We agree with appellant's argument that "[t]here is no teaching in Howard of a control means for
Appeal No. 95-4788
Application 07/996,393
- 8 -
controlling the amplification factor of the driver so as to produce a smaller amplitude of the clock
pulses used to sweep the residual charges than for the clock pulses used to transfer the charge
signals specified in claim 3" (Brief, page 9). The examiner's reasoning that "it would have been
obvious . . . to control the variations in the prior art clock pulse voltages in accordance with the
dual-voltage control means disclosed in Howard et al. in order to provide different clock voltages
for the respective sweep and transfer functions of a solid state imaging device so that more control
could be exercised over minimizing the thermal noise generated by these pulses" (Examiner's
Answer, page 5) does not provide any factual support for the reasoning that one skilled in the art
would have sought to minimize the thermal noise by controlling the amplitude of the clock pulses.
For the reasons stated above, the rejection of claims 3-5 is reversed.
REVERSED
ERROL A. KRASS )
Administrative Patent Judge )
)
)
)
) BOARD OF PATENT
LEE E. BARRETT ) APPEALS
Administrative Patent Judge ) AND
) INTERFERENCES
Appeal No. 95-4788
Application 07/996,393
- 9 -
)
)
)
RICHARD TORCZON )
Administrative Patent Judge )
Appeal No. 95-4788
Application 07/996,393
- 10 -
HILL, VAN SANTEN, STEADMAN & SIMPSON
A Professional Corporation
85th Floor Sears Tower
Chicago, IL 60606