FLIR E40 upskirt shots - Page 1
Forum section: electronics / general

author: eKretz
author_rank: Frequent Contributor
timestamp: March 09, 2019, 10:08:01 am
content: I have been thinking of possible ways to try to use a 75mm f/1.0 lens I picked up cheap some time ago with my FLIR E40, so I decided to do some poking around at the lens mount to see if the lens could be removed and replaced with something else with some modification. I pulled the O.E. lens and measured it for future reference. While it was out I took a few shots in case anyone besides me was curious what's under there.

author: eKretz
author_rank: Frequent Contributor
timestamp: March 09, 2019, 10:09:32 am
content: And under the lens...It appears that the front lens element is just mainly an aspheric to correct distortion, as the camera still produces an image even with it out of the mount, but it's not nearly as sharp as it is with the front element in. Down in the hole it looks like either a filter or a germanium window, as it's flat. Placing my 75mm lens in front of the mount basically just acts like a close-up lens is mounted.

author: Fraser
author_rank: Super Contributor
timestamp: March 09, 2019, 12:44:09 pm
content: An interesting thread that I am sure will be of interest to manyI am no expert on optics as I have stated previously. I have bought various books in an attempt to better understand optical block designs. Please bear this in mind when reading my comments. I am writing this in less than ideal circumstances on an iPad so it is bound to be full of typos and weird auto corrections. Sorry about that and I will correct the text laterFirstly, I do not know anything about the 75mm lens you are using, or its intended original host. Such information is invaluable as I may know a little about the host camera and its optical systems.The lens in your E40 will consist of at least two lens elements. Sometimes thermal cameras have a ‘doublet’ design that looks like a single lens when, in fact, the ray trace indicates two distinct lens actions are in play. The E4 has such a lens. The two lenses can be separate, as in the Exx series, but they work in harmony with each other as a matched pair to create a low distortion image that illuminates the sensor array. It is not normally possible to just replace the objective lens element to change the optical blocks characteristics for telephoto operation. A mismatch beteween the lenses causes the effect you have seen. You description of the effect experienced, (close-up effect) makes me think you are using a 75mm lens from certain models of scanning thermal camera made by Inframetrics or Agema. Such lens barrels contain only one or two lenses, the objective and a focus element, as the rear lens is a fixed component in the scanning cameras lens mount. That fixed lens is usually a negative concave type.The back focus distance of a thermal camera is a critical specification of the lens block design and can be completely wrong if the lens block contents are modified without consideration of the effect on the back focus distance and correct illumination of the sensor array.So what can I offer as positive comment .........I personally would avoid any modification of the excellent quality FLIR Exx lens block. Such is fraught with complications that severely reduce the imaging performance. You really have to be a master of ray tracing simulation and have access to both the specifications of the original lens elements and those you are hoping to replace them with. Practical Experimentation is possible but can be fruitless and frustrating without a good understanding of optics and interpretation of issues that can occur.A safer/easier way to enhance a thermal camera optical performance is to go down the path of supplimentary optics. In the same way that a close-up lens is like placing reading glasses on the camera, you can effectively place a monocular telescope in front of the objective to achieve the desired telephoto effect. There are losses involved in such an approach but a calibration offset may be applied to account for such where needed. For wildlife observation, calibration is not often required.Inframetrics, NEC-AVIO, AGEMA, FLIR and FLUKE all use afocal, non inverting supplimentary telescopes and wide angle Adaptor’s in order to avoid the need to remove the cameras objective lens. This is often a requirement due to the lens block design (sealed or internal motorised focus). Supplimentary lenses are not to be scorned or feared and they are very suitable for experimentation.A quick guide to supplemental lenses.... These are normally Afocal when intended for use on a conventional camera optical block. That is to say, they receive rays at their input and ‘process’ them to exit the output in parallel ray format suitable for illumination of the cameras fixed objective. Some cameras are focussed at finity when used with supplemental lenses. The output of a supplemental lens can be an inverted version of that which entered them. This is due to the optical design and is normally dealt with in the host camera the lens was intended for. It is a purely electronic processing change in the camera to re-invert the image. Sadly when using an inverting supplimentary lens on a camera that does not offer image inversion, the user is faced with either modifying the supplemental lens by inserting an erector element, inverting lens pair, or post image capture manipulation in software (host PC)Are all supplimentary lenses the same in terms of how they work ? In short, NO.As an example, the supplimentary lenses for the Agema PM series, FLIR Exx series and FLUKE cameras are non inverting and may be mounted in front of many LWIR cameras that have a matching, or similar FOV and lens diameter. Using a small diameter supplimentary lens on a large diameter objective is not a great idea due to vignetting. The use of a large diameter supplimentary lens on a small diameter camera objective works fine however.Now the tricky types of supplimentary lens........Agema used to offer alternative lenses for their scanning cameras that, at first glance, appeared to be supplemental types. Upon seeing how they mount on the camera it becomes clear that it is not a supplimentary lens system, but rather a split lens block with half the elements in the removable lens barrel, and half permanently mounted in the camera mount on the camera chassis. This approach effectively reduced lens barrel cost as one Germanium element was not required in the barrel..... the one fixed in the camera. This also facilitated the required vacuum sealed scanning mirror assembly as the fixed Germanium element is sealed into the side of the vacuum module.Inframetrics took different approaches to the challenge of interchangeable lenses. Some are the same principle as that used by AGEMA, a spilt lens block, whilst others are a complete lens block in the camera, with true supplimentary telescopes or wide angle adapters that mount in front of the scanning cameras input window. These are the lenses that I sought out for experimentation as the range includes both MWIR and LWIR coated telescopes of decent power. x3 is a common magnification factor for the telescopes found on eBay. The Inframetrics supplimentary lenses are different to those ones from FLIR, FLUKE etc. They are intended for operation into the large window input of a scanning mirror imaging system and those systems were capable of image inversion. As such, a standard Infametrics x3 supplimentary lens will be inverting and will not optically match into another cameras objective without some experimentation. Please see the experiments by Ultrapurple for detail. He had to place his cameras objective quite some distance behind the telescopes output. These Inframetrics lenses are superb quality thermal optics though, so worth the effort.Well that is enough from me for nowFraser

author: Fraser
author_rank: Super Contributor
timestamp: March 09, 2019, 01:03:17 pm
content: Some adational information......FLUKE offer two types of optional lenses. Be aware that some are Supplimental whilst others are not. I can confirm that the Tele 2 and Wide 2 are true supplimentary lenses. I believe the Tele 1 and Wide 1 are primary lenses that replace the cameras lens block. I have yet to delve deeper I into the Tele 1 and Wide 1 lens block designs though. Be careful which you buy !Fraser

author: Fraser
author_rank: Super Contributor
timestamp: March 09, 2019, 01:32:18 pm
content: EKretz,Is your post title intended to attract attention ? Upskirt means something very different to me. I have referred to looking under a cameras ‘clothes’ when doing a tear down, but upskirting ? NopeFraser

author: Vipitis
author_rank: Frequent Contributor
timestamp: March 09, 2019, 02:12:44 pm
content: Ah,this is very interesting. I heard the Exx lens has some kind of hidden bayonet and can be removed all together. Having direct access to the sensor is important for me. My approach to lens design has been 'trail and error' using an improvised optical bench and 3D printed prototypes. Just yesterday I ripped my current lens prototype apart to allow for better infinity focussing.Also yesterday I took apart my phone and looked the different lens elements while replacing the battery.I would love to know more, as I am sure thinking about heaping out on the M1 again.

author: Fraser
author_rank: Super Contributor
timestamp: March 09, 2019, 04:35:28 pm
content: Vipitis,Regarding the bayonet mount on the Exx series..... there is room for confusion.....The E30/40/60 do have a bayonet mount but it is in front of the objective lens and accessed by twisting the lens bezel a quarter turn CCW. The bayonet mount is for mounting supplimentary lenses in front of the fixed primary lens which cannot easily be removed.The latest Ex5 series cameras also have a bayonet mount, but it is very different to the earlier model. The Ex5 series have user removeable primary lenses. The primary lens is attached via a bayonet mount and may be removed and another primary type lens fitted in its place. This is a better optical solution than the use of supplimentary lenses as the primary lenses are optimised and suffer lower transmission losses and distortion than a combination of primary and supplementary lenses.Be aware that just because a camera platform offers a removeable primary lens, it does not mean that you can fit another primary lens to it that was not designed for the application. There are two issues, the lens needs to illuminate the sensor array fully and operate at the correct back focus distance. There is also the added complication of ‘smart’ lenses. Many removeable lenses, both primary and secondary contain an EEPROM or other System to identify the lens characteristics to the host camera electronics. Some cameras use a combination of tiny magnets and Hall effect sensors in the mount faces (FLIR PM series) whilst others use pogo pins and contacts in the mount faces FLIR Txxx series). If the camera is expecting to see ID data from a primary lens that is not present, it will often raise an error condition and the camera will not operate. It may be possible to spoof the ID system but knowledge of its operation would be needed. A non original fitment or DIY primary lens is possible on cameras that are not ‘conscious’ of a lens being fitted or that do not require an ID code from the lens.Fraser

author: Ultrapurple
author_rank: Super Contributor
timestamp: March 09, 2019, 04:40:12 pm
content: Quote from: Fraser on March 09, 2019, 01:32:18 pm+1And LWIR isn't even the best choice. I'm told.

author: eKretz
author_rank: Frequent Contributor
timestamp: March 09, 2019, 07:58:56 pm
content: Upskirt was just sort.of referring to looking up under the lens... not meant in a serious way.The lens is an Ophir SupIR. I knew that it was not an afocal lens but was unaware of the double lens setup in the EXX cameras. Thought maybe I could make some modifications that would allow the original objective to be swapped for the SupIR lens. Wasn't too worried about it not working, as the price for the lens was dirt cheap. At any rate I've got some very large coated germanium lens elements to play with for next to nothing.That is very good information Fraser thanks, and now that I have discovered that the lens block setup is different than I had imagined, I agree that it would be a very large pain in the tail to modify in the way that I had thought about. It would seem that if I could find the correct plano-concave lens this SupIR might work as an afocal lens but that would be unlikely unless I order one, which would throw any "low cost" consideration right out the window.I did end up cleaning everything up with optical KimWipes and some acetone last night and de-dusting, then putting everything back together. I used UV-curing resin around the outside of the lens to re-seal it in place. Still thinking about what I might want to try next. Anybody got any afocal lenses they might want to trade for a nice SupIR?

author: Fraser
author_rank: Super Contributor
timestamp: March 09, 2019, 08:08:02 pm
content: Nice lensFraser

author: Hyper_Spectral
author_rank: Regular Contributor
timestamp: March 11, 2019, 01:51:09 pm
content: What core was this lens designed for that allows it to work with 1024x768?

author: eKretz
author_rank: Frequent Contributor
timestamp: March 11, 2019, 10:15:24 pm
content: No idea, but it doesn't have to be designed for a specific core to work, just has to have enough physical area to cover the sensor. The elements are quite large. Front element is nearly 3" diameter.