Photochromic vs Self Dimming
05-23-15, 09:53 AM
#1
Driver School Candidate
Thread Starter
Photochromic vs Self Dimming
A friend of mine has an Acura with photochromic side mirrors. They have a slight bluish tint. Lexus describes the side view mirrors on my 15 RX as "self dimming". The Lexus mirrors do not seem to have a bluish tint.
What is the difference between the Lexus self dimming mirrors and the Acura photochromic mirrors? Is the underlying technology the same. I have not had a chance to drive the RX extensively at night so I don't know how well the technology works.
Thanks
What is the difference between the Lexus self dimming mirrors and the Acura photochromic mirrors? Is the underlying technology the same. I have not had a chance to drive the RX extensively at night so I don't know how well the technology works.
Thanks
05-23-15, 01:05 PM
#2
Moderator
Without researching Acura's mirrors, I suspect the implementations are different. I'm not into all the scientific detail and PhD-speak, but there is lots of that available with a simple WWW search if you're so inclined. Knowing someone is probably going to find a technicality with it, I'll still try to more simply describe what I suspect are the two auto-dimming/anti-glare implementations like this...
One can use a chemical process to cause self-dimming of lenses and mirrors like on sunglasses. It can take something like 1-15 mins to go from minimum to maximum darkness through the chemical process that occurs when the same surface is exposed to certain types of light. As an example, photochromatic glasses and sunglasses have an applied coating that looks pretty clear in a shaded room, but once you walk into the sun, they begin to darken, and then begin to get clear again as you walk into a building or darkened room again. The speed of that transition is what is an issue for some people. I personally found photochromatic prescription glasses very difficult to use at theme parks where you are frequently moving in and out of light and dark spaces; when shopping at an outside mall as you meander in and out of stores, or when I used to drive through tunnels in Hawaii and the glasses were sometimes starting to brighten up as I was exiting the tunnel back into the brilliant sun going to and from work each day. The chemical process to dim things is relatively inexpensive I suppose, but with my glasses, always seemed to be behind where I wanted them to be at that moment in time. The question is, with a rearview mirror, how long is "too long" before auto-dimming one way or the other takes place?
The other way to dim something is to use liquid crystals within the glass panel or mirror. An electrical charge is used to align the crystals such that light passes almost fully through, or by aligning the crystals another way, you block light. You've seen how liquid crystals work on electronic displays for years -- those black digits, text and graphics that appear out of nowhere as current is passed to certain predefined areas of the LCD. You may have also seen examples where people have glass windows in a home or business with a liquid crystal sheet in or on it, such that with a flip of a switch, the whole panel goes from see-through to opaque and back when you flip the switch the other way. That is also how my fancy MBZ Magic Sky Roof works -- I press a button and the "sunroof" gets fairly dark, or I press it again and it's nearly see-through -- when I turn the car off, the "sunroof" always goes dark, but goes back into the state I had set it once I start the car again. It's a similar thing with Lexus rearview mirror implementations -- a light sensor on your rearview mirror tells your car when to send a current that dims or brightens the mirror, effectively giving you an anti-glare function because of the way it's angled and designed. IMHO, using liquid crystals is probably a bit more expensive, but is a lot faster, more precise than the photochromatic (chemical) implementation, and you don't get the color-hue side effects that some have. The sensor location or the reason power is applied to flip around the crystals doing the auto-dimming in this case, can be anywhere or anything the designers desire, whereas the photochromatic version happens more on "auto pilot" based on light hitting the same surface that is to be dimmed. E.g. in my RX450h, the auto-dimming function gets turned back on by my RX each time I start the vehicle, even if I turned auto-dimming off for some reason the last time I was driving -- that couldn't be done with a photochromatic implementation as it will always be trying to adjust itself based on the available light hitting that specific surface.
One can use a chemical process to cause self-dimming of lenses and mirrors like on sunglasses. It can take something like 1-15 mins to go from minimum to maximum darkness through the chemical process that occurs when the same surface is exposed to certain types of light. As an example, photochromatic glasses and sunglasses have an applied coating that looks pretty clear in a shaded room, but once you walk into the sun, they begin to darken, and then begin to get clear again as you walk into a building or darkened room again. The speed of that transition is what is an issue for some people. I personally found photochromatic prescription glasses very difficult to use at theme parks where you are frequently moving in and out of light and dark spaces; when shopping at an outside mall as you meander in and out of stores, or when I used to drive through tunnels in Hawaii and the glasses were sometimes starting to brighten up as I was exiting the tunnel back into the brilliant sun going to and from work each day. The chemical process to dim things is relatively inexpensive I suppose, but with my glasses, always seemed to be behind where I wanted them to be at that moment in time. The question is, with a rearview mirror, how long is "too long" before auto-dimming one way or the other takes place?
The other way to dim something is to use liquid crystals within the glass panel or mirror. An electrical charge is used to align the crystals such that light passes almost fully through, or by aligning the crystals another way, you block light. You've seen how liquid crystals work on electronic displays for years -- those black digits, text and graphics that appear out of nowhere as current is passed to certain predefined areas of the LCD. You may have also seen examples where people have glass windows in a home or business with a liquid crystal sheet in or on it, such that with a flip of a switch, the whole panel goes from see-through to opaque and back when you flip the switch the other way. That is also how my fancy MBZ Magic Sky Roof works -- I press a button and the "sunroof" gets fairly dark, or I press it again and it's nearly see-through -- when I turn the car off, the "sunroof" always goes dark, but goes back into the state I had set it once I start the car again. It's a similar thing with Lexus rearview mirror implementations -- a light sensor on your rearview mirror tells your car when to send a current that dims or brightens the mirror, effectively giving you an anti-glare function because of the way it's angled and designed. IMHO, using liquid crystals is probably a bit more expensive, but is a lot faster, more precise than the photochromatic (chemical) implementation, and you don't get the color-hue side effects that some have. The sensor location or the reason power is applied to flip around the crystals doing the auto-dimming in this case, can be anywhere or anything the designers desire, whereas the photochromatic version happens more on "auto pilot" based on light hitting the same surface that is to be dimmed. E.g. in my RX450h, the auto-dimming function gets turned back on by my RX each time I start the vehicle, even if I turned auto-dimming off for some reason the last time I was driving -- that couldn't be done with a photochromatic implementation as it will always be trying to adjust itself based on the available light hitting that specific surface.
I've not tried it on my 450h, but on my former 400h, at night in my driveway I could cover the sensor on the rearview mirror and I'd see the reflection brighten-up, then immediately take my finger off and shine a flashlight onto the sensor and pretty quickly, it darkened... That simulated the way the rearview mirror acted when I drove through the dark desert at night, and as cars approached from behind with the headlights (and highs!) on, the rearview mirror would dim, then get brighter as the cars went back to low beam or passed me.
I don't think the side mirror anti-glare function is standard on the base RX, or which package it comes with -- likely the Premium and/or Luxury Pkg with folding side mirrors if I were to guess. I believe my side mirrors auto-dim just like the rearview mirror does on my 450h, but I've not paid enough attention to be 100% positive. The manual for my 2013 states side mirror auto anti-glare is only available on "(if equipped) vehicles", and that it is activated in conjunction with the inside rearview mirror anti-glare function. Therefore, if my logic holds, and we both have auto-dimming side mirrors, all 3 have to be using the liquid crystal implementation that IMHO does not have that "blue hue" you are referring to on your friend's car.
Hopefully I didn't stray too far from your question, but helped describe what I suspect is the likely difference in implementations... Enjoy that RX!
I don't think the side mirror anti-glare function is standard on the base RX, or which package it comes with -- likely the Premium and/or Luxury Pkg with folding side mirrors if I were to guess. I believe my side mirrors auto-dim just like the rearview mirror does on my 450h, but I've not paid enough attention to be 100% positive. The manual for my 2013 states side mirror auto anti-glare is only available on "(if equipped) vehicles", and that it is activated in conjunction with the inside rearview mirror anti-glare function. Therefore, if my logic holds, and we both have auto-dimming side mirrors, all 3 have to be using the liquid crystal implementation that IMHO does not have that "blue hue" you are referring to on your friend's car.
Last edited by BertL; 05-23-15 at 01:13 PM. Reason: Dang autocorrect caused a couple of typos ;)
05-23-15, 01:54 PM
#3
Driver School Candidate
Thread Starter
Wow! Lots of information to absorb. Thank you so much for taking the time to craft such a thorough answer.
Based on your answer I suspect that the implementation is electrochemical. I have an FSport. The specs indicate that it has self dimming mirrors. I have covered the sensors in the rear view mirror and had similar results yours, however I have yet to find the sensors for the side view mirrors. It could be that they are imbedded in the mirror glass.
Thanks again for your response.
Based on your answer I suspect that the implementation is electrochemical. I have an FSport. The specs indicate that it has self dimming mirrors. I have covered the sensors in the rear view mirror and had similar results yours, however I have yet to find the sensors for the side view mirrors. It could be that they are imbedded in the mirror glass.
Thanks again for your response.
05-23-15, 02:15 PM
#4
Moderator
If your side mirrors dim and get brighter along with your inside rearview mirror, you definately have liquid crystals in all 3. It's the only way they could be coordinated.
If your side mirrors are photochromatic like some sunglasses, there won't be a sensor for them -- "the chemical" that does the dimming is effectively also the sensor all-in one thing -- it's why you could in theory have one side mirror dimmed a bit more than the other at the same time because light hits each of them differently based on how they are angled, and your rearview interior mirror could be much darker or brighter than the outside ones because your inside mirror is more responsive as its light sensor is aimed more directly at the traffic behind you. If you have photochromatic side mirrors, and it's pitch black outside where someone hits their high beams behind you, you'll be better off to only look at that car in your interior rearview mirror since it will dim almost immediately to reduce the glare, whereas the side mirrors will take much longer (as in minutes) to do the same, and they'll also take longer to "brighten up" once that car passes you or dims it's lights behind you.
Try the flashlight example in your garage or driveway I tried to explain when it's completely dark. The other thing you could do is ask the Technology Specialist at your dealership. With your VIN, and their knowledge of what comes with what package, they should be able to provide the answer if you don't want to play Sherlock Holmes and figure it out on your own.
Enjoy!
If your side mirrors are photochromatic like some sunglasses, there won't be a sensor for them -- "the chemical" that does the dimming is effectively also the sensor all-in one thing -- it's why you could in theory have one side mirror dimmed a bit more than the other at the same time because light hits each of them differently based on how they are angled, and your rearview interior mirror could be much darker or brighter than the outside ones because your inside mirror is more responsive as its light sensor is aimed more directly at the traffic behind you. If you have photochromatic side mirrors, and it's pitch black outside where someone hits their high beams behind you, you'll be better off to only look at that car in your interior rearview mirror since it will dim almost immediately to reduce the glare, whereas the side mirrors will take much longer (as in minutes) to do the same, and they'll also take longer to "brighten up" once that car passes you or dims it's lights behind you.
Try the flashlight example in your garage or driveway I tried to explain when it's completely dark. The other thing you could do is ask the Technology Specialist at your dealership. With your VIN, and their knowledge of what comes with what package, they should be able to provide the answer if you don't want to play Sherlock Holmes and figure it out on your own.
Enjoy!
05-24-15, 07:16 AM
#6
Driver School Candidate
Thread Starter
I tried to emulate a headlight shining in the mirrors by using a flashlight and observed 2 things.
1) the side view mirrors are self dimming using a liquid crystal technology.
2) the sensor on the front of the rear view mirror senses the amount of available light for both the rear view mirror and the side view mirrors. Covering the sensor tells the system that it is dark which increases the amount of tint in the mirrors when they are exposed to headlights.
1) the side view mirrors are self dimming using a liquid crystal technology.
2) the sensor on the front of the rear view mirror senses the amount of available light for both the rear view mirror and the side view mirrors. Covering the sensor tells the system that it is dark which increases the amount of tint in the mirrors when they are exposed to headlights.
05-24-15, 07:29 AM
#7
Moderator
I tried to emulate a headlight shining in the mirrors by using a flashlight and observed 2 things.
1) the side view mirrors are self dimming using a liquid crystal technology.
2) the sensor on the front of the rear view mirror senses the amount of available light for both the rear view mirror and the side view mirrors. Covering the sensor tells the system that it is dark which increases the amount of tint in the mirrors when they are exposed to headlights.
1) the side view mirrors are self dimming using a liquid crystal technology.
2) the sensor on the front of the rear view mirror senses the amount of available light for both the rear view mirror and the side view mirrors. Covering the sensor tells the system that it is dark which increases the amount of tint in the mirrors when they are exposed to headlights.
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