Appeal No. 1999-0344
Application 08/250,770
emission from a laser is a function of current supplied to the laser and the pulse
duration that is normally supplied to it anyway. At column 6, lines 27-34 it is stated:
Therefore, in order to obtain the same image density from a same
image signal with a varied amount of laser light emission, it becomes
necessary to regulate the pulse duration in response to the change in the
amount of light emission. This is achieved, in the present embodiment, by
employing a number of binary encoding circuits corresponding to the
number of switched levels of the laser power.
Figure 5 depicts a logical flow chart diagram indicating that the particular choice of laser
power to achieve the desired print density is a function of the CPU controlled clocking
signals (pulse duration or pulse width modulation) provided. Note also in contrast
Hayashi’s prior art statement at column 1, at least at lines 18-29.
In any event, the approach taken in Hayashi appears consistent with that taken
by appellant’s disclosed invention in Figure 3, the subject matter of the chopping means
of claim 1 on appeal, and appellant’s disclosed approach to control the amount of light
illuminating the photosensitive drum to adjust the density of the printed images.
Hayashi’s approach is comparable to the analogous solutions provided by Tomita for
light emitting diode exposure printing devices. Even though it is for a plurality of light
emitting diode printing elements set forth in an array, Tomita does teach selectability of
pulse signals based on different duty ratios according to the showing in Figure 6 relied
upon by the examiner. The variable duty ratio discussions and showings in Figures 6-9
6
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