inkjet printer technology is truly the magic of cmy colors the engineering behind the droplets and how the color algorithm creates the final image is pretty clever we all know that display technology consists of minute red green and blue subpixels as an experiment one of our engineers at lesix filter inkjet printer with the same rgb colors let's take a look at our printer output the result was terrible the printer couldn't reproduce the image of the flower with the correct colors to understand the reasons behind this intriguing result let's explore the inner working of the inkjet printer in color science first consider the most fundamental inkjet technology the black and white printer you can print any image with a collection of many dots these dots are produced by drops of ink being released from many nozzles the ink is not dropped continuously but in a discreet and controlled way as shown the small circumference of the nozzle and back pressure inside it won't allow the ink to leak out allowing for a precise image to release the ink we must use these small heating resistors these resistors are so responsive that when the electricity runs through them they gain around 100 degrees celsius pe microsecond to release a drop of ink simply supply power to the respective resistor it will then heat up and vaporize the ink thus forming a bubble this bubble acts as a piston to push the ink out of the nozzle however when the primary drop is falling the ink gets elongated due to viscosity as a result it forms one more drop which falls near the primary drop after some time both drops combine while focusing on the drop you may have missed one important process let's replay the animation again this time direct your focus on the top region here after some time the heater is turned off causing the vapor around the coil to condense in the bubble to collapse the back pressure of the ink sucks outside air into the nozzle immediately afterwards the surface tension of the meniscus will play an important role by working against the back pressure forcing the fresh ink to fill the nozzle and remove the air from it now that we've established the fundamentals let's see how to build a practical printer an ink tank is connected to the printhead via a connection pipe which is free to move along this horizontal rod the printer also uses a belt and pulley mechanism powered by a stepper motor next connect the printhead with a belt using a movable arm you can see how the head moves left and right along with the movement of the belt let's start the printing now as we saw earlier the head can print a series of black dots by properly controlling the heating resistors the printing example you see here is highly exaggerated for ease of understanding the actual printhead size is a fifth of this head notice how the head produces nine lines during a pass but the actual head produces more than one thousand lines one pass has been completed now we have to continue the printing process in the remaining area of the paper for this a roller stepper motor and two supportive roller arrangements come into play this arrangement can move the paper downward now just repeat the process we saw earlier until the print finishes the print head movement shown here is not so smart it doesn't do any printing during movement from left to right also the printhead takes many unnecessary steps modern printers are equipped with clever algorithms which make this process faster the optimal printing path of a printhead and precise paper roller movement is calculated even before the printing process starts you can see how fast this printing is now when the printhead follows this predefined path obviously this path will change drastically based on the image you want to print the printhead and paper are able to follow such a precise path because they are controlled by a stepper motor and a feedback circuit till now we have constructed a basic black and white printer but how can we use the knowledge what we've learned so far to develop a color inkjet printer the most obvious and intuitive answer seems to be to use red green and blue ink since these are the fundamental colors of display technology however this just won't work to understand why let's explore the fundamentals consider two colored flashlights one is red and the other is green when we flash both torches at the same point the resulting light is yellow now let's try the same experiment using ink colors when we mix these two colors we instead get a muddy yellow color why do these two experiments produce totally different output colors even though the input colors are the same the first case in which we mixed lights was an example of the additive color mixing method while the second case with the ink is a subtractive mixing method the additive mixing method is so simple the combined light portion directly reaches your eye and you see that color however the subtractive method is a little tricky the lights reflected from the ink are important here to better understand how the subtractive
method works we need to examine the link at a molecular level we know we see a red color because the red molecule absorbs everything except red in short what we see in an ink color is the remaining color after the subtraction the same is the case with the green color however when we mix both colors the physics becomes more interesting since one layer of molecules cannot completely fill a surface we should consider at least two layers for this study here we are assuming that the different color molecules are uniformly mixed as shown let's start with the bottom green molecule the green molecule will obviously reflect green light however this green light has to pass through the upper molecular layer you can see this top green molecule will just allow this green light however the neighboring red will completely absorb this green light in short that area will produce a black color now let's consider the light coming from the bottom red molecules when you do the analysis the same way this is the final output the black is present in a good portion between the red and green lights which affects the final output color this muddy yellow color is what our eye sees due to the presence of black a good example of the understanding of the effect of black color in the final output is this gray hair example we see the overall color of the hair is gray but in fact it is a blend of white and black hairs this is why the subtractive method is totally different from the additive method in why we got horrible printout when we used rgb colors in the print heads so far we've learned that we can't use primary colors to reproduce colors and the subtractive method is the villain the color we see in an ink print is in fact the inverted portion after the absorption the solution to this issue is simple just invert the fundamental colors the inversion colors of red green and blue are cyan magenta and yellow respectively thus these are the colors we must use in the printer here's an example we want to produce a green color using these cym colors first release a drop of cyan ink from the nozzle before this drop dries up release a yellow droplet at the same location mixing these two colors will produce a perfect green color after some time the drop gets absorbed in the paper and we get a green dot similarly as shown in the animation we can produce most of the colors with perfection using c y and m droplets we saw how to produce a perfect green color in an inkjet printer but can we produce a lighter shade of green like these to achieve this clever engineers have tricked our eyes they just printed the normal green color with different spacing increased spacing tricks the brain into seeing a lighter shade of the color now the next task how to produce the darker shade darker shades cannot be achieved just by using c m and y the printer has to use black link as well the black ink is referred to as k where k stands for a key now let's understand the mechanism behind dark shades of green color printing the obvious answer will be just mixing a black ink droplet with green color logically it's correct but there's an issue with this method you won't be able to increase the darkness of the green color by a small degree since the droplet size of the black and green are the same to achieve different shades of the colors accurately here again the engineers tricked our eyes just drop a black link droplet in between green droplets according to the shade of green color it will trick the brain into seeing a darker shade of the color the printer quality of modern printers is quite high due to the very small size of the ink drops the smaller the drop the higher quality of the print for decent quality we required more than 300 dots per inch square of paper however to achieve even more incredible results the modern printer has 2100 to 4200 nozzles per printhead thank you for this we hope it gave you a clear understanding of what goes on inside your printer see you next time