Focal Plane Shutter Research Articles

Shuttering methods and the artifacts they produce

When exposure times were measured in minutes, the opening and closing of the shutter was essentially instantaneous. As more sensitive films and brighter optics became available, exposure times decreased, the travel time of the shutter mechanism became increasingly significant, and artifacts became visible. Perhaps the best-known shutter artifacts are the spatio-temporal distortions associated with photographing moving subjects using a focal-plane shutter or sequential electronic sampling of pixels (electronic rolling shutter). However, the shutter mechanism also can cause banding with flickering light sources and strange artifacts in out-of-focus regions (bokeh); it can even impact resolution. This paper experimentally evaluates and discusses the artifacts caused by leaf, focal plane, electronic first curtain, and fully electronic sequential-readout shuttering.

Megacam: A Wide-Field CCD Imager for the MMT and Magellan

Megacam is a large-format optical camera that can be operated at the f/5 Cassegrain foci of the MMT on Mount Hopkins, Arizona, and the Magellan Clay telescope at Las Campanas Observatory, Chile. Megacam’s focal plane is composed of 36 closely packed e2v CCD42-90 CCDs, each with 2048 × 4608 pixels, assembled in an 18,432 × 18,432 array. Two additional CCD42-90s are provided for autoguiding and focus control. The CCDs have 13.5 μm square pixels that subtend at the f/5 foci, yielding a 25′ × 25′ field-of-view. The camera system includes a focal plane shutter, two filter wheels, two liquid nitrogen reservoirs, a central chamber that holds the CCD mosaic array, and two electronics boxes. Megacam is equipped with a variety of broadband and narrowband filters. Software features include automatic calculation of twilight flat exposure times.

Measuring the Noise of Digital Imaging Sensors by Stacking Raw Images Affected by Vibrations and Illumination Flickering

This paper discusses camera noise estimation from a series of raw images of an arbitrary natural static scene, acquired with the same camera settings. Although it seems natural to characterize noise from the random time fluctuation of pixel intensity, it turns out that these fluctuations may also be caused by illumination flickering and mechanical microvibrations affecting the camera. In this context, the contributions are twofold. First, a theoretical model of image formation in the presence of illumination flickering and of vibrations is discussed. This parametric model is based on a Cox process. It is shown that illumination flickering changes the standard affine relation between noise variance and average intensity to a quadratic relation. Second, under these conditions an algorithm is proposed to estimate the main parameters governing sensor noise, namely the gain, the offset, and the readout noise. The rolling shutter effect, which potentially affects the output of any focal-plane shutter camera, is...

POSE VERSUS STATE: ARE SENSOR POSITION AND ATTITUDE SUFFICIENT FOR MODERN PHOTOGRAMMETRY AND REMOTE SENSING?

Abstract. We investigate the advantages of using what we call sensor state parameters or sensor state to describe the geometrical relationship between a sensor and the 3D space or the 4D time-space that extend the traditional image pose or orientation (position and attitude) to the image state. In our concept, at some point in time t, the sensor state is a 12-dimensional vector composed of four 3-dimensional subvectors p(t), v(t), γ(t) and ω(t). Roughly speaking, p(t) is the sensor’s position, v(t) its linear velocity, γ(t) its attitude and ω(t) its angular velocity. It is clear that the state concept extends the pose or orientation ones and attempts to describe both a sensor’s statics (p(t), γ(t)) and dynamics (v(t), ω(t)). It is also clear that if p(t), γ(t) are known for all t within some time interval of interest, then v(t) and ω(t) can be derived from the former. We present three methods to compute the state parameters, two for the continuous case and one for the discrete case. The first two methods rely on the availability of inertial measurements and their derived time-Position-Velocity-Attitude (tPVA) trajectories. The first method extends the INS mechanization equations and the second method derives the IMU angular velocities from INS mechanization equations' output data. The third method derives lineal and angular velocities from relative orientation parameters. We illustrate how sensor states can be applied to solve practical problems. For this purpose we have selected three cases: multi-sensor synchronization calibration, correction of image motion blur (translational and rotational) and accurate orientation of images acquired with focal-plane shutters.

Electromagnetic focal plane shutter with vertical moving double curtains

Electromagnetic focal plane shutter with vertical moving double curtains

EOS Kiss X50 電子先幕専用シャッター

EOS Kiss X50 電子先幕専用シャッター

An open and shut case [computer graphics

You press the button on your camera, the shutter opens, the film is exposed, the shutter closes, and you have a picture. If anything moved, including you, the image will show motion blur. When we create synthetic images with computer graphics, we have to account for motion blur for three reasons. First, we're used to it from physical motion pictures. Second, without motion blur a film can suffer from strobing, a psychophysical phenomenon. Third, without motion blur an object can alias in time. In a real camera, a mechanical device called the shutter controls the exposure of the film. The computer graphics literature includes many camera models, lenses, and even discussions of film and its simulation. Surprisingly, there is little discussion of simulating how a moving shutter actually exposes the film. The author finds it surprising because modeling the shutter mechanism is easy, and as shown in the article, very important to the rendered image. The following shutter types are modelled via computer graphics: instantaneous shutter; uniform shutter; focal plane shutter; interlaced shutter; leaf shutter; inverse leaf shutter; and clock shutter.

SOFT X-RAY IMAGES OF THE SOLAR CORONA USING NORMAL INCIDENCE OPTICS

A solar coronal loop system has been photographed in soft X-rays using a normal incidence telescope based on multilayer mirror technology. The telescope consisted of a spherical objective rnirror of 4 cm aperture and 1 m focal length, a film cassette, and a focal plane shutter. A metallized thin plastic film filter was used to exclude visible light. The objective mirror was covered with a multilayer coating consisting of alternating layers of tungsten and carbon whose combined thicknesses satisfied the Bragg diffraction condition for 44 A... radiation The image was recorded during a rocket flight on 1985 October 25, and was dominated by emission lines arising from the Si XII spectrum. The rocket also carried a high resolution soft X-ray spectrograph that confirmed the presence of Si XII line radiation in the source. This image represents the first successful use of multilayer technology for astrophysical observations.

Soft X-Ray Images of the Solar Corona Using Normal Incidence Optics

AbstractA solar coronal loop system has been photographed in soft X-rays using a normal incidence telescope based on multilayer mirror technology. The telescope consisted of a spherical objective mirror of 4 cm aperture and 1 m focal length, a film cassette, and a focal plane shutter. A metallized thin plastic film filter was used to exclude visible light. The objective mirror was covered with a multilayer coating consisting of alternating layers of tungsten and carbon whose combined thicknesses satisfied the Bragg diffraction condition for 44 Å radiation. The image was recorded during a rocket flight on 1985 October 25, and was dominated by emission lines arising from the Si XII spectrum. The rocket also carried a high resolution soft X-ray spectrograph that confirmed the presence of Si XII line radiation in the source. This image represents the first successful use of multilayer technology for astrophysical observations.

Multilens Cameras For High Velocity/Low Altitude Photoreconnaissance

After an outline of the fundamentals of the multilens array combined with focal plane shutter and angle-correct forward motion compensation, the KS-153A Trilens and Pentalens arrays are described. Then the special ground resolution capability of the multilens camera is compared to that of the tri-camera fan, and the geometric imaging capability is compared to that of the panoramic scan camera.

Comments on speckle interferometry with regard to displacements of the camera during an exposure

Displacements of single-lens-reflex camera, which lead to errors in measuring displacements of an object by speckle interferometry, are studied to make sure that cameras with focal plane shutters displace to some extent, regardless of ways of mounting.

Mariner 10 star photography

Two identical television cameras, each having a long and short focal-length capability, were carried aboard the spacecraft for the reconnaissance of Venus and Mercury. These telescopes were used in conjunction with a filter-wheel assembly and a focal-plane shutter to provide an image on a slow-scan vidicon tube. The results obtained with this system are discussed, giving attention to aspects of sensitivity and questions related to focal length and geometric distortion.

Diffraction Effects of a Focal-Plane Slit Shutter and Its Interaction with Uniform Linear Image-Motion

A general expression for the exposure transfer function of a photographic system employing a focal-plane shutter is derived which includes the effects of uniform, linear image-motion. The results show that the modulation transfer function (MTF) of such a system is upper bounded by the product of the diffractionlimited optical MTF and a term strongly coupling the shutter and motion effects. The coupling of these effects results in a general solution dependent upon the size and shape of the pupil and the aberrations of the optical system.

The Surveyor Variable and Fixed Focal-Length Lenses

The Surveyor spacecraft has TV cameras equipped with specially designed versatile variable focal-length lenses. Each lens is capable of withstanding extreme environments under the most adverse conditions of an earth launch, earth-moon journey, lunar soft landing and the vacuum and temperature variations of the moon. Each lens assembly is an optically integrated unit consisting of a 25mm to 100mm variable focal-length lens with earth-commanded motor drives for focal length, 4 ft to infinity focus and f/4 to f/22 adjustable iris mechanisms; a reflex viewing system behind the lens for automatic exposure control; solenoid-actuated focal-plane shutter; and motor-driven color filter wheel to provide color picture capability. Effects of radiation on optical transmission, optical performance in a vacuum, outgassing of particles on the lens surfaces, selection of lubricants and an all air-spaced optical design were among the design problems that were solved.

Unit and System Design of a Lunar Operating TV Camera

When Surveyor I soft landed on the moon it began within an hour to transmit the first of over 11,000 TV pictures of the moon. The camera's design requirements were set by a wide range of temperatures, the need to maneuver the camera to view any area, the spacecraft's power supply and the need for verification from the spacecraft to confirm to the operator that the camera had received and executed each command. The camera has a complex variable focal length lens complete with focus adjustments and a commandable iris. The camera is positioned vertically on the spacecraft and the lens looks directly into the rotating-mirror assembly. A focal plane shutter exposes a 1-in. hybrid vidicon tube for 150 ms prior to the frame readout. Problems encountered are described and illustrations show the variety of conditions under which the camera performed.

Skin and subcutaneous temperature changes during exposure to intense thermal radiation.

Radiometric measurements have been made of the skin temperature changes occurring during irradiation of the body by high-intensity thermal radiation with square-wave pulses. A quartz lamp bank provided a source of color temperature of 2,650 K and a uniform (± 5%) irradiance of 0.16 cal/sec per cm2 over areas of 40 x 30 cm. A spring-operated focal-plane shutter controlled exposure times from 2–120 sec with a rise time of 0.01 sec. The radiometer, mounted between the quartz lamps so as to view the skin from normal incidence, had a 96% response time of 0.1 sec and a precision of ± 0.1 C. When corrections were made to allow for the far infrared radiation reflected from the skin, the radiometer gave accurate measurements of skin temperature during the periods of irradiation. Experimental values of skin temperature rise were compared with those calculated by the finite differences method for various skin layers using the best available values for optical and thermal properties of each skin layer. During the initial 10–15 sec of irradiation, theoretical and experimental values were in agreement, indicating passive response of the skin to thermal radiation. Subcutaneous temperatures, calculated from surface temperature data, indicated a high degree of penetration of the radiation 0.2–0.4 mm below the skin surface. mathematical model; infrared reflection by the skin; radiometric measurement of skin temperatures Submitted on September 2, 1964

The Influence of Image Motion and Shutter Operation on the Photographic Transfer Function

In Part I a general two-dimensional expression for the transfer function of the photographic exposure image is derived, including as factors the optical transfer function, the transfer function arising from scattering of light in the emulsion, the shutter function, and the motion of the image. The effect of shutter operation in the absence of image motion is discussed and it is shown that a focal-plane shutter acts as an independent agent with its own effective transfer function, whereas a between-the-lens shutter is not independent but acts as an apodizing agent. In Part II, the effect of image motion is discussed, with the assumption that the optical transfer function is independent of the shutter action. The concept of an equivalent spread function for image motion is developed, and uniform linear image motion and harmonic image motion are discussed in detail, the latter especially for the case where there are at simple the most only a few periods in the exposure time. An approximation for small degradations is then obtained in which all possible combinations of uniform linear motion and simple harmonic motion are contained. Throughout the paper the functions discussed are functions of two-dimensional space.

Applications of the High-Speed Focal-Plane Shutter Camera to Explosives Research

The camera described in the paper immediately preceding in this Journal is particularly suited for the study of detonation phenomena because of its continuous coverage in time, for 216 frames, of at least some portions of the subject. The coverage feature minimizes the chance of failure to observe details of rapidly changing phenomena. The camera was intentionally designed to record the six rows of images on two film strips with the images of the three rows on each film phased one-third frame apart. In addition, the shutter apertures for each filmed group of images can be selected independently for flexibility in control of exposure. This camera has been used at framing rates up to 1.1 million frames per second to record transient phenomena in the study of the growth to detonation in explosives subjected to mechanical shocks of known amplitude. Example records of these experiments are shown and discussed.

Inexpensive 50 000 Pictures Per Second Framing Camera

A framing camera has been built based upon a very simple image multiplier. The image multiplier consisted of two layers of ¼-in.-diam glass rod (glass blowers' cane) crossed at right angles. At each intersection a real image of the event was produced. A 6×6 in. image multiplier produced some 576 separate images of the event. A transfer lens allowed these images to be projected on to a sheet of 8×10 in. film. A Nipkov disk was used to scan the image multiplier to produce a framing sequence up to a rate of 50 000 pictures/sec. It was considered that this framing rate could easily be extended beyond 106 pictures/sec using a Jacob's optical focal plane shutter. The camera has the faults of parallax and optical distortion, but in the present application of the camera these are minimized by using a grid stationed at the event. It is considered that the camera is superior to those based upon image dissection devices. The camera was designed to be continuously available for approximately 3 msec, and was fitted with a crudely synchronized shut-off shutter to prevent overwriting when used in the present application.

Paper H–3: A Rotating-Mirror Framing Camera with Multiple Focal-Plane Shutters

Paper H–3: A Rotating-Mirror Framing Camera with Multiple Focal-Plane Shutters