Patent Application
20210218902
This invention is in the broad field of imaging/photography and more specifically is for automated image capture in sequential focus-distance steps using still or video cameras.
This invention provides a new method and hardware to obtain photographs of any subject ranging from very small insects to distant landscapes with the entire image in complete focus, from the very front edge to the back edge of the subject. In the past, such extended depth of field (DOF) photographs were obtained using so-called field cameras (4″×5″ film) using very small apertures and with a bellows attachment, tilting the lens vertically relative to the plane of the film to maximize DOF. This approach is still used by some for product photography because of the high resolution provided by a 4″×5″ sensor (film). Some film users have the films digitized using high resolution scanning in order to further refine the images using commercial software. Because of modern computers and digital cameras, a different approach is possible in which a series of photographs is taken in incremental focus distance steps and then combine all of these (perhaps hundreds of images) into a single composite image in which software combines in-focus regions of each image to give a final image having very high detail clarity. There are several ways to adjust the focus distance, either manually or automatically:
For the past decade or so, Methods 2 (mainly) and 3 have been used extensively by photographers and scientists interested in high resolution images. Method 2 is accomplished for small objects (Macro-photography) by use of a manual rail or a linear rail and stepper motor having a lead screw and moving platform, allowing steps in distance smaller than 0.01 mm. This method however is limited to subjects not much larger (in terms of depth) than the length of the rail, typically 10-20 cm.
Method 1 can be accomplished manually and there are a few approaches offered commercially to improve the ease of manual changes. One company (Wemacro) offers a means to automatically rotate the focus knob of a microscope to take in-depth images of microscopic objects. A few high-end DSLR and mirrorless digital cameras now offer a “focus-bracketing” feature using internal motors to adjust the focus stepwise while taking pictures at each step. These cameras work but do not offer full control of the process and require auto-focus features in both the camera and lens. Method 1 can now also be accomplished with a commercial “add-on” product—Helicon FB Tube is an extension tube with integrated electronic microcontroller designed to enable automated focus bracketing in single or continuous shooting modes. Mounted on the camera in the same way as a conventional macro extension tube, the tube automatically shifts the focus by one step with each shot thus producing any desired stack of images for later processing to obtain the final image. This device currently (2019) only works on selected Nikon and Canon cameras using selected (auto-focus) lenses.
Method 2 can be accomplished using commercial linear rail hardware and control software designed for that purpose such as by Cognisys or Wemacro. With some modifications (not currently offered) Method 3 could be executed using these rail systems.
There is another area of imaging technology that also relates to this invention, regarding taking videos with digital cameras, including inexpensive DSLR or mirrorless cameras and very expensive movie cameras using so-called cine lens often used by professionals in this field. The cine lenses often have a gear band fastened to the lens focus ring and sometimes to the zoom ring or to the aperture ring. External focus follow motors can be used on these cameras for video recording even with manual lenses. Several companies have introduced hardware to assist amateur and professional movie makers involving automated gimbal devices to minimize rapid camera movement. These gimbal frames also provide for use of the focus-follow geared motors attached to the lens barrel or camera mounting hardware and which interface with the focus ring. Though with a much different purpose, the physical arrangement is related to one embodiment of this invention and in fact uses the same kind of gear band on the focus ring that we use. The motors currently used in these devices are small, 3-phase brushless motors often used to power remote vehicles and provide about a ×6 mechanical advantage in reducing speed of rotation of the focus ring compared to the motor rotation speed. The devices are not currently intended nor controlled for the purpose focus bracketing. The purpose of the focus-follow devices is to manually or automatically smoothly change the focal distance, when for example filming a moving object. Some devices also provide the means to wirelessly rotate the focus ring from a distance as might be useful in filming wild animals.
New commercial software (even free versions) has recently become available to extract individual frames from digital videos. The ever-increasing resolution in modern digital cameras (50 mp or more) makes filming an interesting approach to capture multiple still images. Our invention allows taking advantage of hardware approaches and possibly focus follow devices related to our design to control the focus ring rotation during filming. Many digital cameras allow filming at speeds up to 10 frames per second and movie cameras deliver up to 100 frames per second. Some movie cameras now offer resolution as high as 16K, meaning each frame may contain 100 mp of data. Even for higher-end (advanced amateur) cameras, each frame contains up to 10 mp of information, suitable for high resolution imaging. This means, using this invention that 15 or more frames can be obtained in a few seconds, ideal for photography of insects, flowers, animals, etc. in nature. It could also be useful in a studio where instead of taking a few minutes to obtain 50 or more still images (for example, a portrait), it could be done in 8 seconds, or less than 1 second with a professional movie camera.
Technical considerations—before describing the focus ring control system and its different embodiments, it is useful to recognize some basic features and constraints regarding camera lens in general that lead to the design and implementation of this invention.
First, before focus stacking images using computers became possible and even now, it is common practice to use very small apertures (e.g. f32) to maximize the depth of field (DOF). When this is done, because of diffraction effects, some blurring occurs. It is commonly understood the sharpest images are obtained with the lens a few stops less than the wide-open aperture for any given lens (e.g. f5.6 or f8). Since focus stacking removes the DOF constraint, optimum lens settings can be used to deliver the sharpest image, affecting only the number of images required in the stack since the larger the aperture, the smaller is the DOF. The number of images is usually chosen to be about V2 the DOF at the desired camera-subject distance in order to overlap in-focus regions. This often leads to stacks of 20-200, or more images. One photographer (L. Biss) produces extraordinary photos of large, colorful insects using microscope lens with very shallow DOF and in total takes as many as 10,000 images for the final extraordinary product.
Second, the common linear rail approach of incrementally moving the camera and lens together to focus the front through to the back of the subject, involves a considerable change in magnification as shown in
Third, although the linear rail method is precisely linear in distance/step, the focus ring on any lens is quite non-linear regarding focus distance, as displayed in
This behavior is important for the leadscrew/tab embodiment of the invention, because for practical mechanical reasons, it does have an angular range of about 120 degrees during any one stack collection. Thus, in order to cover the entire depth range from the nearest point out to infinity (about 250 degrees rotation), it would be necessary to do two or more series of photo collections. It would be better to do so anyway, because many fewer shots are needed at long distances since the DOF increases dramatically in that range.
This invention allows either manual or fully automatic collection of images by externally moving the focus ring for any camera and any lens. The manual method (see
The automated method employs either a stepper motor/lead screw configured to interface with a tab extending out from the focus ring or use of solid gears or a pully gear to interface with a gear band secured to the focus ring. Because the low torque required to turn the focus ring, the stepper motor can be controlled to deliver very fine micro-steps even though the power is reduced by doing so. For example, the typical stepper motor delivers 200 steps per 360-degree rotation of the axle. Using micro-stepping, we can adjust this to be 3200 or more steps to achieve 360-degree rotation. The combination of electronic and mechanical advantages allows focus ring adjustments in extremely small increments, even smaller than needed.
The following drawings (3-13) define the primary embodiments of this invention which include two basic hardware configurations—one in which all hardware is attached directly to the Camera/lens and another in which most of the hardware is attached to a rigid platform that is mounted on a tripod.
Introduction—This invention allows either manual or fully automatic collection of images by externally moving the focus ring for any camera and any lens. The manual method (see
The automated method employs either a stepper motor/lead screw configured to interface with a tab extending out from the focus ring or use of solid gears or a pully gear to interface with a gear band secured to the focus ring. Because of the low torque required to turn the focus ring, the stepper motor can be controlled to deliver very fine micro-steps even though the power is reduced by doing so. For example, the typical stepper motor delivers 200 steps per 360-degree rotation of the axle. Using micro-stepping, we can adjust this to be 3200 or more steps to achieve 360-degree rotation. The combination of electronic and mechanical advantages allows focus ring adjustments in extremely small increments, much smaller than needed.
The invention includes the ability to mount all the hardware needed directly on the lens barrel and focus ring (see
Unlike methods 2 and 3 described earlier, this Method (1) is suitable for close-up macro work, for portraits, for product photography and for landscape photography. It can take thousands of photographs, though normally 100 or so, extending from a few centimeters out to infinity and any smaller distance range of interest.
The invention is highly portable (<1 Kg) with nominal dimensions 10 cm×10 cm×30 cm for the Z-channel support structure and uses a small 9-12V DC power pack to power a Nema-17 stepper motor. Because our controller turns off power to the motor between series (unlike current commercial rail systems) and because so little power is needed to rotate the focus ring (compared to moving a 2-3 kg camera and lens), many thousands of shots can be taken with a single battery pack before recharging.
Method of use—Because photography in general and especially the focus-stacking method is dependent on the DOF/distance conditions in its execution, it is useful here to give a few examples of how the controller is used in order better understand the method regarding the appropriate step size and number of steps which are somewhat different for every situation. With some experience, the method is simple to execute. Here are a few examples—
These three examples suggest it will often be the case that taking 100 shots or less for any subject will be adequate, depending on the lens and aperture used. Note that the usual linear rail method (moving the camera and lens together) would require a 25 cm rail for example 2 and example 3 could be accomplished only with a much longer rail, or with a very wide-angle lens. (In fact, for 20 mm and lower focal distance lens, everything will be in focus from 1 m to infinity by focusing at the hyperfocal distance (2 m for 20 mm, 1.4 m for 16 mm) and only one picture is needed. If you intended to create a gigantic wall poster, you might use 4 or 5 shots and focus stacking to enhance the foreground.)
We can also use the controller in a somewhat different manner than described by the pervious examples and which may be important as software evolves. Because of the nonlinear behavior of camera lens regarding DOF as a function of distance, and the nonlinear behavior of focus ring rotation to select the focus distance, the use of fixed steps in terms of rotation angle may not be best. It is possible by reprograming the drive chip in the controller to automatically change the step size as each step is taken. In this way, it would be possible to make the step sizes be larger as the focus distance increases but maintain that the step size is still about ½ the DOF at that distance. This would minimize the number of shots required and may allow improvements in the rendering of the stack as well. Since we have not yet refined this alternative, all the discussion and examples in this submission refer to what we might call the “standard means” to control the process, meaning the steps are all the same in terms of angle of rotation. The “advanced means” suggested here would use different step sizes depending on the focal distance in moving from the front to the back of the subject.
Regarding the length of time involved, we typically use 1-2 seconds per step. That means taking 100 steps requires 100 to 200 seconds. We previously identified the use of video to acquire the needed images. It is worth remembering that by using the method of this invention to control focus ring rotation while filming at 7 frames per second, 100 images can be collected in 15 seconds and with a true cine camera, 1 second would be enough. Processing the 100 images in Helicon software may take 30 minutes or more.
Regarding measuring the rotation-angle change desired, a typical lens has a diameter of 7.5 cm, with a circumference of 23.5 cm. So, rotating the focus ring by 1 cm produces an angle change of 360/24=15 degrees. To be precise, an inexpensive digital level meter can easily measure changes to 0.01 degrees. In any case the user focuses at the very front of the subject, notes the ring position and then focuses at the back, again noting the ring position. This is easily done using colored tape to mark the positions. Movement by 2 cm would mean 30 degrees rotation and you would set the step size to cover that range in 100 steps or so. The method is especially simple for digital cameras because it is so inexpensive and easy to acquire the images—if too large a rotation angle is used, simply discard those not needed by visual inspection, before processing.
Finally, this invention utilizes various gear bands such as those used in printers and computer numerical control (CNC) equipment where stepper motors provide precise positioning for printer heads or various tools. The fiber reinforced band material is available in both 6 mm and 10 mm (preferred) wide versions with gear teeth about 0.8 mm deep. There are various solid gears that mate with the gear band. The cine cameras and various focus follow devices use a thicker neoprene/rubber gear band 7.5 mm wide and with gear teeth about 1.5 mm deep and there are also solid gears that mate to these. It is also possible to purchase gear bands custom made to fit most lens and targeted to the video community. In a commercial embodiment of this invention, the gearing would be customized for that purpose and deeper gear teeth like 2 mm would be even better.
Controller functions and use—A controller is used to adjust several important factors in using this method to vary step size, number of steps, etc., depending on the subject distance and corresponding DOF. The controller is shown in
The following table describes the various screens/control options and the range in variables currently set as the standard ranges, but which can be readily adjusted by reprogramming the control chip.
A camera shooting sequence is initiated by the user by pressing the Enter keypad switch while the initial Shots screen is displayed.
The embedded software
The progress through the sequence is displayed on the liquid crystal display (LCD), for example, “Performing shot 8 of 100”. At the end of a shooting sequence, the motor direction is then automatically set opposite to its initial setting and the motor is returned to its initial position by sending a series of motor increments equal to the photographs taken (steps) multiplied by the Steps per Shot. At that point, the motor coils are disabled. The user can then start a new shooting sequence with the same configuration or change the configured parameters. An active shooting sequence can also be aborted by pressing the Enter button.
There is one manual configuration shown (
This figure shows the magnification changes for different lenses as a function of distance to the subject. Note that at the point of closest focus, 4 lens achieve m=1:1, being so-called macro-lens, while one lens reaches only 1:2. At the 1:1 condition, the subject fills the sensor area, being about 40 mm×25 mm for full-frame cameras. At 1:2, the subject only occupies about ½ the sensor area. The magnification changes are larger for short focal length lens (40 mm) compared to telephoto lens (such as 200 mm). Lens of the same focal length are different in their magnification dependence vs. distance for different manufacturers. The lens shown include Nikon 40 mm, Nikon 60 mm, Canon 60 mm, Sigma 105 mm, and Nikon 200 mm. Note for example the magnification changes for the Canon 60 mm lens are a factor of 10 through about 0.4 meters change in distance. So, using the traditional linear translation method, even moving just a distance from front to back of a subject=0.04 m (40 mm) changes magnification by 100%.
This figure shows the nonlinear relationship between the subject distance and focus ring rotation angle. For all three lens-200 mm, 105 mm and 60 mm, the focus ring rotates about 100 degrees going from the point of closest focus (1:1) to a point about 0.2 m further away. Although not fully shown here, the distance from about 0.8 m out to infinity requires only about another 50-150-degree rotation depending on the lens. This characteristic, along with large increases in DOF as distance increases have a strong influence on how the method is executed, being somewhat different in dealing with close-up, mid-range, and long-distance photography subjects.
This figure displays the most simple, manual method of precisely rotating the focus ring to incrementally change focal distance and then take the desired series of photographs by using a manual electronic shutter release to minimize inadvertent camera movement. In this manner, the camera (3.1) is mounted on a plate (3.2) which in turn is attached to a tripod (not shown). An L-shaped extension arm (also attached to the releases plate) and attached micrometer mounting plate support the micrometer screw (3.3). As an alternative, the micrometer screw could also be attached to the solid part of the lens barrel with an appropriate clamp and extension hardware. The tip of the micrometer screw is iron and is strongly attracted to the bar magnet (3.4). The bar magnet is attached to the lower portion of a rigid L-shaped arm (3.5) which in turn is attached to the focus ring (3.7) by means of a clamp (3.6). The micrometer screw typically has a range of only 2.5 cm, but 5 cm screws, or longer are available. Rotating the focus ring by 1 cm produces an angle change of 360/24=15 degrees. Because of the geometric position of the screw, movement at that point by 1 cm is only ⅓ cm at the focus ring and produces 5 degrees rotation. This means a 5 cm screw movement moves the ring 25 degrees. As discussed through examples given earlier, the rotation angle needed may be more than 25 degrees which would require either taking two or 3 series of photographs, or using a 10 cm screw or longer, one could cause rotation of 50 degrees or more.
Regarding sensitivity, a typical micrometer can easily be read/adjusted to within 0.0001 cm, meaning the angular resolution will be to 0.0005 degrees in rotation, well smaller than needed.
This figure shows one method of automated rotation control of the focus ring in which all the hardware is attached to the lens. In this embodiment, a metal band (4.1) is attached to the solid base of the lens barrel (4.1). A hinge-pin (4.3) is also attached to the metal band and it in turn is connected to a stepper motor (4.4) by means of an attached mounting plate (4.5). The motor could be for example a Nema 14 or even Nema 11 motor because very little power is needed to rotate the focus ring. The motor in any case turns a pulley wheel which in turn rotates a moving gear band (4.6) interfaced to an identical pitch gear band (4.7) fastened directly to the focus ring (4.8). Although not shown, a double solid gear arrangement (as shown in a plate mounted embodiment (
Regarding sensitivity, the mechanical advantage is about ×6 for both the solid gear and pulley-gear band embodiments, so the motor axle must turn 360 degrees 6 times to cause the focus ring to move 360 degrees. At the normal step size for this motor of 1.8 degrees per step, (200 steps per 360 degrees), the focus ring will rotate 1.8/6=0.3 degrees per step. Using micro steps at 1/16 the normal size, the resolution is 0.02 degree per step.
While mounting hardware on the lens barrel is clearly possible, we consider it better to mount the hardware directly on the tripod in such a way that the camera can be easily removed and used in conventional hand-held photography, without the encumbrance of external hardware. This figure shows a front view of a plate mounted embodiment in which the plate (5.1) is directly mounted via a quick connect clamp (5.5) to a tripod (5.4). The camera/lens is also attached to this plate via a quick connect clamp, in this example in such a way that the large lens extends out from the front edge of the plate. The motor (5.7) drives a pulley wheel (5.6) which in turn drives the pulley gear band (5.8). The moving gear band interfaces exactly (same pitch) with a gear band solidly attached to the focus ring. The moving pulley band, by way of a freewheeling cylinder (5.9) interfaces with both the top and the bottom of the lens with slight compression, to maintain the gear band-to-band interface, without putting any asymmetric force on the lens or camera, as occurs with arrangements from just one side. In order to properly (and conveniently) tension the pulley band, both the motor (5.7) and free-wheeling cylinder (5.8) are mounted on a T-channel, allowing their adjustment toward or away from the lens.
The sensitivity of this embodiment is about the same as for mounting the pulley system on the barrel as in
In this figure, we show how solid gears can be used to rotate the focus ring. In this case, all the hardware and camera/lens (6.7) are attached to a single plate (6.11) which can be of any dimension but might be about 10 cm by 30 cm and 3 mm thick. The plate (6.11) is attached to a tripod via a quick release clamp (6.5). In this example, there is room for the controller (6.6), as well as for the battery power pack which can be placed just under the controller. The camera is mounted to the plate via a quick release clamp and can move forward and back to align the focus ring gear band (6.9) with the position of the mating solid gear (6.4). The mating gear (6.4) is driven by the motor gear (6.3). The mating gear and motor are attached to a face plate (6.1) which in turn is mounted on a sliding plate (6.10). The sliding plate is confined to lateral movement by two slots in the plate (6.2) and can be tightened by two bolts extending through the slots from the sliding plate above, just at the point where the mating gear (6.4) and the focus ring gear band (6.9) are in good contact. A T-channel mounting could also be used instead of slots to adjust the motor/gear position. The focus ring gear band (6.9) in this example is attached to a steel band (6.8) for easy attachment to the focus ring.
The sensitivity in this embodiment as in previous examples is largely determined by the ratio of the focus ring diameter to the diameter of the drive gear. In this case, the ratio is over 8 to 1. The highest sensitivity works out to be about 0.015 degree per step.
This figure provides a block diagram showing how a commercial motor driven linear rail can be adapted to execute Method 1 by positioning the camera/lens in such a way that an extension of the lead screw, through a pulley-gear is able to rotate the focus ring. In this figure, the commercial rail system is shown as a side view and is confined by a base and two end plates (7.1, 7.4). The rail and moving platform (7.13) normally used to move mounted objects horizontally can be either ignored or removed as they are not used in this adaptation. Normally, the lead screw (7.3) does not extend beyond the end plate (7.4), but by using a longer lead screw, it can be modified such that the lead screw does extend out beyond the frame end. A small diameter pulley gear (7.5) can be attached directly to the lead screw end as shown. This drive gear (7.5) interfaces with a pulley gear band (7.8) which in turn interfaces to a gear band (7.10) that is attached to the focus ring (7.9). Though not shown here, a freewheeling pulley gear can also be added to the end plate (7.4) in such a way as to provide a tensioning mechanism to the pulley gear band (7.8). As shown, the camera (7.12) and lens (7.11) are mounted on a quick release plate (7.7). The plate is held by the clamp (7.6) which is attached directly to the end plate (7.4). The camera and lens can be easily moved to position the focus ring gear band (7.10) directly above the drive gear (7.5) below. Note that the pitch of the lead screw has no impact on the sensitivity as it is merely an extension of the motor drive axle in this use.
As in the other pulley gear embodiments already described, the sensitivity realized with this geometry is about 0.02 degrees per micro-step.
The sensitivity in terms of angular control of the focus ring can be enhanced from the preceding embodiments involving direct coupling of a motor axle-gear to the focus ring gear band, to instead use an indirect geometry in which the screw moves a platform in such a way as to interface to the focus ring via a rigid tab, as already utilized in the manual method displayed in
An automated version of the manual method is to replace the micrometer screw with a motor driven lead screw arrangement as shown in this figure, involving a Z-channel platform as the base, composed of a bottom surface (8.4) and a top surface (8.7). Though not shown here, the platform is attached to a tripod below by means of a quick-release clamp. The cameral/lens is attached to a quick release plate (8.7) held on the platform by the clamp (8.11) and is free to move forward and backward for alignment.
The Nema 17, 1A stepper-motor is secured to the lower base (8.2) by mechanical locking and glue between the upper platform (8.7) and the lower platform (8.4). The motor turns a 1 mm pitch lead screw (8.5). A moving nut on the screw is attached to a rectangular plate (8.6) such that the plate rests on the base surface (8.4) and thereby cannot turn, but instead causes the plate assembly to move horizontally as the screw rotates. A bar magnet (8.8) interfaces with a rigid arm/roller bearing (8.9) attached to the focus ring (8.14) by means of a clamp (8.13).
The sensitivity in this embodiment can be understood as follows—the geometry provides a ×3 mechanical advantage as suggested by
An important element of this invention is the use of a rigid extension arm to couple the focus ring rotation to the linear movement of a plate/bar magnet below the lens barrel. In this figure, a front view includes the camera lens (9.7), an attached L-shaped arm (9.3, 9.4) in four different angular positions and a moving plate/bar magnet (10.5) shown in four different lateral positions.
The arm has a long leg (9.3) and a short leg (9.4). A roller bearing (9.6) is attached to the end of the short leg (9.4).
The focus ring (9.8) rotates in unison with the attached arm as the tip of the arm (at the roller bearing edge) follows an arc described by the dashed circle. Note that the magnetic bar (9.5) at the position labeled 9.5 causes the arm to be at the bottom of the circle and as the bar magnet moves to the right (driven by the motor/lead screw), the focus ring moves counterclockwise. As the plate moves to the left, the ring rotates clockwise. In this example, note that the rigid arm is positioned to be in front of the moving bar, or it would contact the long leg of the arm (9.3) at some lateral position, which would change the point of rotation control (hence step size) quite significantly in the middle of a shooting session. Since we prefer the arm positioned at the same position as the magnet, we adjust the short leg (9.4) to be long enough (longer than depicted here) that the roller bearing is always in contact with the magnet, no matter its position.
Notice the bar magnet can only be so long as to not reach the lens barrel above nor the base below. As the magnet moves, the roller bearing moves up and down the magnet, reaching the top of the magnet at lateral positions on either side of the lens. As suggested in this illustration, the arm loses contact with the magnet at some position, and the maximum rotation angle of 180 degrees cannot be achieved without some other mechanical mechanisms, not important here. In our preferred size and geometry we have control over about a 120-degree angular range such that the rigid arm moves from about the 8:00 position to 4:00 position in going from left to right.
Note that the radius of the focus ring is about ⅓ the diameter of circle followed by the roller as measured along the dashed line from point 10.1 to 10.2 in this configuration. This gives a mechanical advantage of 3. It is entirely possible, but inconvenient to greatly increase the length of the rigid arm (9.3) such that the radius of the focus ring (4 cm) might be only 1/9 the radius of the circle followed by the roller (36 cm), and the angular rotation possible will be much larger than 120 degrees. Such an arrangement is not preferred, because the lead screw provides superior mechanical advantages by itself and 120-degree movement is more than enough for most photographic subjects.
In this figure we show a somewhat different mechanical arrangement for utilizing the stepper motor/lead screw mechanism first described in
Regarding
A relatively simple controller using inexpensive commercial hardware and electronics has been developed to manage any of the various embodiments shown earlier, in their practical execution. This requires that the controller provide means to define the image taking process in terms of speed, number and size of steps, and delay time between steps. As shown in the figure, the controller is fabricated as an aluminum box of approximate dimensions 10 cm×8 cm×4 cm.
Regarding controller functions, keypad buttons (Up, Down, Left, Right, Enter and Reset) on the top and the input/output connectors on the side of the box are all labeled. The keypad buttons on top allow the user to navigate through a list of provided configuration screens and modify settings, as described below. The Reset button resets the microcontroller (stopping any active motor motion). The Up and Down buttons are used to display the next or previous configuration screen in the list. Pressing the Right button invokes Data Entry mode allowing the value of the configuration parameter associated with the displayed screen to be modified. When in data entry mode, the Up and Down buttons increment/decrement the associated parameter by 1 and the Left and Right buttons increment/decrement the parameter value by 10. Pressing the Enter button saves the modified parameter value and exits Data Entry mode. Parameter values are stored in the microcontroller's EEPROM (non-volatile memory) so that the next use of the controller can begin with the previously used configuration.
The connectors on the side are for cables to input 12V DC power, send power to the stepper motor and activate the camera's electronic shutter.
As shown in the labeled block diagram, the controller includes an embedded microcontroller board which is connected to a stepper motor control integrated circuit (IC), a liquid crystal display (LCD) board with keypad switches, and relays for camera shutter activation. One of many possible microcontrollers that could be used is the Microchip Atmega328P with integrated RAM, Flash and non-volatile memories.
The motor control IC (Allegro A4988) accepts digital input signals (digital outputs from the microcontroller) for:
The A4988 IC is designed to operate standard bipolar stepper motors in full, half, quarter, eighth, and sixteenth-step modes.
Two camera control relays connect two contacts to a common third contact to command a connected digital camera to take a photograph. The microcontroller activates each relay using digital output pins connected to the relay coils. Optocoupler IC's could also be used instead of relays.
The display/keypad board is connected to one of the microcontroller's serial communication peripherals (inter-integrated circuit port). The microcontroller sends commands for display of characters on the LCD and to read the state of the keypad switches. The LCD provides two rows of 16 characters for displaying/modifying system settings, activating motor movements and camera control sequences, and displaying the progress of an active shooting sequence.
This figure shows the logic flow diagram utilized by the controller from the start to the end of any single shooting sequence. It is self-explanatory.
US-Provisional filing—U.S. Application Ser. No. 62/922,425 filed Aug. 8, 2019, Confirmation number 3184 (mailed Aug. 23, 2019) Related patent submission: Automated apparatus to obtain images in incremental focus-distance steps using either camera focus-ring rotation or linear translation methods (R. P. Turcotte) Submitted Jan. 9, 2020. NA NA NA NA
