When were the DMI'S introduced to LU stations

Yeah i like those DMI's, i don't travel on the Central much but they shouldn't change those DMI's, they don't seem to have changed the original ones.

so they have changed the original DMI's

There have been several types of DMIs, some of the earlier models faded in the sunlight on outside stations such as Edgware Road.

Of course originally the DMIs simply replaced the existing train describer signs but they were still driven by the original TD equipment. That is probably still so in many locations and is also why they don't display 'time to next train' very well in some places.
You need to understand that back in the days of illuminated TD signs across the system they were mostly driven by ribbon storage and drum TD equipment. These systems worked on the principle of transmitting the description ahead as a train left certain retransmission points, initially the description was 'punched up' by a signalman and then transmitted ahead as the train departed the station and replaced the starting signal. For instance a train departing Wood Green WB Picc would cause the description to be forwarded to King's Cross where it was stored and illuminated the local TD sign but would also cause the TD signs at the intermediate stations to be illuminated with the next train destination. Thus there was apparently a long wait at King's Cross and a very short wait at Turnpike Lane. The Northern line worked differently because it had a positive train identification system which 'knew' the location of trains and put up first, second and third trains on the TD sign when they were a certain distance away from any particular station.
At places like Baker Street platform 5 the next train description was not displayed until the next train departed Edgware Road so all that was ever seen was 1 minute. The DMIs inherited information from the previous systems, whichever they were. Thus most DMIs showed pretty much what the old systems did.

Bear in mind that because the old TD systems mostly relay upon track circuits to 'see' the progress of a train they don't actually have a concept of time so if a train is displayed as 5 minutes away that could be displayed 20 minutes if the train is not moving!

AFAIK new systems were/are being installed which will drive the DMIs more correctly but obviously progress is slow.

How can it be said the signs aren't as clear as a DMI ? What is difficult about seeing a destination and a list of stations the train won't be stopping at ?

Comparing the indicators at Harrow to the DMIs at Wembley, I'd consider the Indicators to be the better solution because they show the stopping pattern of the train in its entirity instead of scrolling like the DMIs. However as pointed out these don't show time to arrival, or where subsequent trains are heading. There have been indicators though that have shown these...

Perhaps in the long term as LCD screens become more suitable, they'll be able to replace both, combining the functional and clear layout of an indicator board with the myriad information and size of a DMI screen.

What do you mean by a low quality blind?

One that is badly designed, badly lit, badly aligned, badly set, dirty and/or wearing out, etc. These days at least they are more common than good ones.

The s stock and 2009 stock uses DMI indicators but what type of destination indicators do the 1996 and 1995 stock use? Why didn't they use DMI indicators.

DDA prefers upper-and-lower case because lower case letters vary much more in size and shape than block capitals, so the general shapes of the words can be distinguished at a greater distance.

Please, not 'any'. Unless you're counting me as old school!