Why do Digital Displays have a Screen saver. When CRT's Don't?

[Labrat101]

Here is The Question.
  That over 50 years in electronics no one has Yet given me a Good Answer .
     Why do Digital displays have a screen savers when CRT's Don't?

 All the CRT's and analog scopes . I have ever used or seen Don't have a screen savers .
 To stop that nasty screen burn. which plagues them All. Also the Plasma &  Phosphor screens suffer from screen burn . 

  I have never seen screen burn on a Digital screen . ie LCD, LED,  But all have a screen saver .. Why.. ?? 

  Yes I know its a silly Question but does any one Know the Real Answer. 
     "To me its like inventing the Gate after the cows have all run out of the field . "

So I would like to hear from all .. WHY. ??     

RNS

[Zero999]

I've never seen a screensaver on any oscilloscope.

There won't be a screensaver on an analogue oscilloscope because it's not something which can easily be implemented using analogue circuitry.

If a modern digital oscilloscope has a screensaver, it will just be for marketing or a novelty.

[Siwastaja]

Never seen one either, so the claim that "all" have it is not on a very stable ground.

IIRC, I think I have seen a screensaver on an Agilent digital storage oscillosscope, but that was a CRT.

Analog scopes could implement "screensaver" in a form of turning the thing off automatically after a set time of no setting changes, but people hate such auto-off features. Engineers want a reliable device that doesn't fuck with their work, because their worktime is more valuable than the fact that instruments wear out and must be replaced. Analog scopes require some understanding, you need to be quite stupid to really burn the phosphor. Most people understand not to do it.

[0culus]

Tek scopes with an mcp crt (7104, 2467) have a protection circuit that (at least in the 7104) shuts off the crt based on a combination how bright the display is set and timing. The brighter you set it (I think it's actually looking at grid current or something), the faster it shuts off to protect the microchannel plate gain. The HP 53310A modulation domain analyzer (and I assume also o-scopes built in the same form factor, using a raster crt) has a screen saver. It's also important to note that electrostatic deflection analog scope crts are not the same as the raster crts that we know and love from televisions and computer monitors.

[Bud]

Shutting off the crt on analog scopes is your screen saver. The fancy dancing stars and stuff on modern digital scope screens is a habit carried over from computers.

[TomS_]

Keysight scopes have a screensaver, which is basically their logo drifting around the screen.

[ucanel]

Shutting off the crt on analog scopes is your screen saver.
....

If i recall correctly, desktop pc that i had 15 years ago was doing the same thing as a screen saver mode.
There was just the hissy crt screen energising sound i remember.

[Zero999]

Yes, blanking the screen is the old fashioned screensaver. I was thinking of the modern fancy screen savers of course. CRTs don't like being turned on and off too often, so it can't kick in too often.

[Labrat101]

When I said screen saver that is what's is in the menu of most Digital scopes .  with set time in minutes etc.
 Yes .
    Very annoying as the screen goes blank in the middle of working.  (yes I disabled it )

  On the big CRT scopes it would be useful if the brightness would turn down automatically on temperature or  after 4 or 5 hours
 to save the screen burning . But that feature was never implemented  .
 As mentioned turning them on & Off is not good.

 Thanks for some Good Answers .. 

[David Hess]

I've never seen a screensaver on any oscilloscope.

Tektronix oscilloscopes which used microchannel plates for image amplification have protection in various forms including blanking tied to intensity and time on the 7104.

Many of their other oscilloscopes tracked the beam current for fault protection.

There won't be a screensaver on an analogue oscilloscope because it's not something which can easily be implemented using analogue circuitry.

And the same applies to a CRT monitor which leads to the answer.  LCD displays include a layer of processing between the video signal and display which can implement a screen saver.  CRT displays are almost always directly controlled from the video signal so any screen saver has to be implemented in the source.

If a modern digital oscilloscope has a screensaver, it will just be for marketing or a novelty.

The same applies to LCD monitors except in some special applications.  Marketing overcomes engineering every time.

[Someone]

CRTs and LCDs do have burn in, and it varies wildly between different panels/drivers. There are a range of mitigation methods used in products that make it less noticeable, or reduce the accumulation. Screen savers are brute force methods when you don't have anything better.

For the high contrast images displayed by test equipment you'll likely never notice the small variations. But in a smooth gradient that same burn in will jump out obviously.

[langwadt]

CRTs and LCDs do have burn in, and it varies wildly between different panels/drivers. There are a range of mitigation methods used in products that make it less noticeable, or reduce the accumulation. Screen savers are brute force methods when you don't have anything better.

For the high contrast images displayed by test equipment you'll likely never notice the small variations. But in a smooth gradient that same burn in will jump out obviously.

yep, we used som 7" lcds and they were basically scrap after about month of showing the same picture

[james_s]

I've seen image retention on LCD panels but usually it fades after a while if you show something else. I've also seen panels that displayed the same image for many years and never showed any kind of retention. There's zero reason to have a screensaver on a LCD scope, although many newer scopes are Windows PCs under the hood so it would not surprise me if the standard Windows screensaver framework can be enabled. I've also heard people refer to the wallpaper or lock screen image on a phone as a screensaver which never made any sense to me, I figured it must be people too young to remember what a screensaver is.

IMO the only time screensavers ever made sense was on all-in-one CRT based computers like the compact Macs. Anything with a separate monitor it has always made sense to just turn off the monitor if you won't be using it for a while. If anything, screensavers encourage people to leave a monitor on unnecessarily. I do have fond memories of watching the flying toasters float by though.

[David Hess]

The only LCD panels where I have seen image burn were either high intensity projection displays or defective displays.  Projection displays are what I was thinking of when I mentioned exceptions.

[NiHaoMike]

I do have fond memories of watching the flying toasters float by though.

Ported to several modern platforms.
https://www.jwz.org/xscreensaver/

[0culus]

HP 85662A spectrum analyzer display (8566A/B, 856(7/8A)/B) is another one I forgot about...shift+g to turn off beam and shift+h to turn it on again. Can also be programmed via GPIB.

[jklasdf]

The Agilent 54622d oscilloscope has a screensaver for its CRT (although it's easier to implement there since it's a digital scope). I think if high-end analog oscilloscopes had continued to be developed into the late 90s, screensavers for the CRT might have become a thing, but for just a plain old analog oscilloscope it seems like a lot of work to implement. The only ones I can think of (as already mentioned) are the Teks with MCP.

I don't think I've ever seen a screensaver on a modern LCD oscilloscope, or if they have one it can at least be disabled. Some early CRT DSOs (e.g. monochrome LeCroys) often have pretty noticeable screen burn-in, and really could've used a screensaver back in the day.

I've seen some screensavers on LCD TVs when there is no signal, or from DVD players when there's no disc, but otherwise I think they're fairly uncommon on most of the devices I've seen. It kind of makes sense when otherwise it would just display a static error message, but I think screen savers are there mostly for legacy reasons or to look nice nowadays, rather than to prevent screen burn-in.

[0culus]

I know for a fact that Keysight MSO series scopes have screensavers. It's buried in some settings menu, and by default just blanks the screen and moves the Keysight branding around.

[vk6zgo]

With normal TV receivers & picture monitors, the normal cause of "burn in" could be caused by still images like test patterns, or more often, text, bright white lines on a dark background, large white geometric shapes, etc.

The most common cause in TV Broadcasting, however, was deliberate underscan.
Older TV tubes had pronounced rounded corners, so if they needed to display a correct 3:4 image, it was common to set the scans to "underscan" to achieve this (it was often provided as a switch function)

If, after being set in this manner for a long time, it was restored to "full scan", the burnt on image of the smaller raster would be evident as a sharply delineated area of lower brightness.

Until the 1980s, the default with no video input was for the TV/monitor horizontal & vertical scans to "free run" at close to the normal scan rates, & the display to remain visible, basically showing random noise instead of video.
If the scans were set to "underscan", it could still  cause burn in.
Starting in that decade, TV sets were designed to display a black screen when video was lost.
Picture monitors did not, by default, do this.

When CRT based monitors were used with computers, the usual display was a black screen with white (or green) text displayed upon it.
As some text was common to many operations, the problem arose of that text burning in.
The computer would automatically generate the "screen saver" when "in standby",  but not currently busy.

[flolic]

My current laptop (HP ZBook 15 G1) with FHD IPS panel has very noticeable image retention after few hours displaying the same image. It gradually goes away, but previous image is still noticeable after an hour.

[Labrat101]

I do have fond memories of watching the flying toasters float by though.

Ported to several modern platforms.
https://www.jwz.org/xscreensaver/

Interesting . puts a whole new light on magic smoke.
  This was not quite what I was referring to . . But to screen blanking .screen protection to stop image burn.
 Which seem to be under the title of screen saver. on many system.
 
     After Dark was far better .. ( The man on a desert island )    Never did do any work just sat and watched it  ..

[SiliconWizard]

As said above, just blanking the CRT display would have been an easy way to avoid screen burns.

On old analog scopes which basically had no "fixed" area of the display, the problem would be minor unless the user left the exact same signal on display for a very long time. Probably not that much of a problem in practice.

The problem started to appear when scopes started to have on-screen display of extra information. I guess automatically blanking the screen after a defined amount of time would have solved the issue, but OTOH that could have been pretty annoying for many use cases. Detecting the user is NOT actually using a scope (as opposed to a computer when you can more or less safely assume that if the user doesn't take any action for a while, they're probably not using the computer) is not that trivial. In some cases, you may work with a scope for extended periods of times without touching it, but still looking at it. Guess vendors didn't bother to add this optional feature. And screen burns can be pretexts to buy new gear anyway...

It's not a "digital display" (I guess LCD?) vs CRT matter IMHO, more a matter of history. When LCD displays became the norm on scopes, screen savers were already popular on computers, so that became more obvious. Still, I've used quite a few modern scopes that didn't have any screen saver feature (at least that I've known of.)

[Labrat101]

Very True.
I have 2 analog scopes which I prefer over my digital .
Both Have the grid on the screen its self and not on a glass over lay . And both have a visible
Burn marks and I can see the grid even when I turn the display Grid Off.
Yes I always turn the brightness down if I am leaving my bench for any length of time.
Hp Agilent @ & the big old Tektronix which I repaired and re calibrated Both not so long ago.
I did even wonder about putting a small button and relay on the brightness control just to dim the screen to minimum .. Push & Go ..But As every one knows if its working don't fix it. .

Thanks for all the feed back . I thought that this thread would never get any replies . 
As being a Engineer/Tech My self it was one of those thoughts that I came up with while stuck Looking at My screens and wondering why the savers or Blanker were invented nearly 10 years after they were not really Needed. 
  ...Lock down has a lot to answer for .. 
I See by all the feed back, this has open a whole new portal .
 Its the simple things in life that are so Pleasing
 I would Love to Get "After Dark" Back   

RNS

[TimFox]

On IPS computer monitors from -hp-, they do not warranty against burn-in caused by a stationary display.  They specifically warn against the use of those monitors in a security/surveillance application, where the scene does not change for hours at a time.  For that reason, I switched the power settings on my desktop computer to blank the screen after a reasonable dead time.

[james_s]

Most of the CRT based DSOs and other instruments I've encountered have some screen burn but I don't think it really matters, it's not something you notice in regular use. Burn is an issue on computer displays and arcade games where the display shows vastly different images at different points in time, I remember seeing a lot of computers with a login screen burned in and arcade games typically have "GAME OVER" and scores and such burned in. A scope though always displays roughly the same thing, a graticule, menu grid, maybe some text. It's rare that large areas of the screen are illuminated which would make the burn visible.