Telequipment DM64, Руководство пользователя

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3.8.1 The storage circuit provides the voltage levels necessary to
operate the flood guns, collimation electrodes, target back-
plate, and erase generators. Additional circuitry includes the
enhance generator, which permits faster single sweeps to be
stored and the integrate switch which permits a stored image
of a number of repetitive sweeps, each of which are too fast
to store alone as a single sweep.
Fig. 1 a block diagram includes the storage circuit.
3.8.2 Storage Basic Operating Principles
The storage target backplate (STB) collects the secondary
electrons emitted by the insulator surface, when the insulator
is bombarded with high energy electrons from the writing gun.
This stored positive charge on the insulator is then used to
control the flow of flood gun electrons to a phosphor screen,
in order to produce a visual image.
3.8.3 The flood guns provide low energy electrons directed in a
large cone towards the screen, the collimation electrodes
shape the electron beam to provide uniform coverage of the
STB.
3.8.4 The operating level of the tube, that is the storage or non-
storage mode, is determined by the potential difference
between the STB and the flood gun cathodes.
3.8.5 In the storage mode, the following states are required to
exist in sequence.
1. Ready to write. The insulator surface of the STB tends to
discharge down towards the flood gun cathodes, such that
the flood gun landing energy is not sufficient to illuminate
the phosphor
in the target.
The target is now ready to write.
2. Writing. The storage target is scanned by high energy
electrons from the writing cathode. These electrons cause
secondary emission to occur over the scanned area and the
bombarded surface charges sufficiently positive to switch
over to a higher voltage stable state and remains in this
state after the writing gun excitation
is removed.
3. Viewing. In this written state, the potential difference
between the flood gun cathodes and the STB has
increased due to the positive charge on the insulator. The
flood gun electrons now penetrate the written area and
illuminate the phosphor. This visual display will persist as
long as the flood beam is allowed to continue to land on
the insulator surface.
At high sweep rates, the writing beam energy is not
sufficient to cause the insulator to switch to the upper
voltage stable state, so when flood gun electrons land on
the target they discharge the insu lator down to the flood
gun cathode potential.
Hence, storage is a function of writing speed.
4. Erasure. When the stored display is no longer required, a
positive pulse is applied to raise the whole STB voltage
above the writing threshold, so that the whole area is
written with flood gun electrons The pulse then goes
negative and as the voltage gradually returns towards zero,
the target is charged
towards the ready to write threshold
and the whole procedure can be repeated.