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Re: [OM] Flash patents (Long)

Subject: Re: [OM] Flash patents (Long)
From: HI100@xxxxxxx
Date: Mon, 24 Jan 2000 23:17:33 EST
         Since there seems to be a lot of interest in OM/Minolta OTF and 
Flash patents here are a few references I dug up a while back when looking 
into this for my own purposes. I have more references but don't have space 
here. You can follow up more for yourself on the IBM or US patent office web 
sites. Minolta has a number of fundamental patents but Olympus/Maitani/Cannon 
etc have various enhancements and Olympus is still actively patenting a 
variety of flash related ideas (including underwater photography recently). 
Some of the more recent patents are for IS series cameras with dual tubes to 
act as zoom etc. I have annoted the patents a bit (see sections in 
parenthesis) here and included the first line of the claims but I may have 
missed some so there may be other fundamental patents. Some of the Olympus 
flash patents are interesting in that they give substantial circuit detail 
and description in the patents specification section, and you realise FP 
flash is not so easy to do. 

Patents :

US3730063: DUAL LIGHT-RESPONSIVE AUTOMATIC EXPOSURE CONTROL APPARATUS
May. 1, 1973 / May. 11, 1971    (Minolta ) 
We claim :
1. In a photographic camera having light-responsive means for measuring scene 
light through an objective lens, a capacitor connected to said light 
responsive means to form an integrating circuit, a switching circuit 
responsive to said integrating circuit, and means driven by said switching 
circuit to initiate shutter closing after a delay period determined by said 
integrating circuit, the improvement wherein said light-responsive means 
comprises: a first photoconductive element mounted outside of the direct 
light path from said objective lens to the light sensitive film surface and 
responsive to light reflected from at least said light sensitive surface, and 
a second photoconductive element mounted for receiving light transmitted 
through said film. 

US3687026: A LIGHT REFLECTIVE SHUTTER CONTROL APPARATUS 
(OTF Minolta)
Aug. 29, 1972 / Nov. 13, 1970 
A light scattering surface is mounted facing the objective lens to direct 
light to a photoelectric detector during movement of a shutter curtain so 
that shutter control is provided during the exposure. An integrating circuit 
formed by a condenser and the photoelectric detector actuate a switching 
circuit to control movement of a second shutter curtain to terminate the 
exposure. 

US3726197: APPARATUS FOR AUTOMATIC ELECTRONIC FLASH PHOTOGRAPHY 
April 10, 1973 / March 26, 1970  (Cannon) 
In the apparatus disclosed a photocell is mounted inside the camera and 
directed toward the film of the camera. After the shutter of the camera is 
snapped a flash is set off. A control system responds to the output of the 
photocell to control the amount of light produced by the flash. 

US3864699: AUTOMATIC EXPOSURE CONTROL SYSTEM FOR TTL METERING TYPE 
SINGLE-LENS REFLEX CAMERA 
( Cannon)
Feb. 4, 1975 / Sept. 6, 1973 
In the TTL metering type single-lens reflex camera, a photoelectric converter 
element disposed for receiving light from a viewfinder's optical system and a 
photoelectric converter element disposed outwardly of such optical system for 
receiving light reflected from a shutter curtain or a film surface after 
flip-up of the viewing mirror are parallel-connected and have characteristics 
selected to be substantially equal so that the rising and falling electrical 
properties of these elements are utilized to accomplish a smooth transition 
of exposure control. 

US3842424: EXPOSURE CONTROL DEVICE IN SINGLE-LENS REFLEX CAMERA 
Oct. 15, 1974 / April 11, 1973 (Cannon )
This invention relates to an exposure control device for automatically 
controlling the shutter speed in a camera, especially a single-lens reflex 
camera. It utilizes the reset time characteristic of a light receiving 
element such as photoconductive cell or the like having a slow response 
characteristic to control the camera shutter to a high shutter speed, and 
utilizes light reflected from the surface of a film to control the shutter to 
an intermediate or a lower shutter speed. 

US3994001: Photometric apparatus for single lens reflex camera 
Nov. 23, 1976 / Sept. 13, 1974 (OTF/ Maitani/Olympus) 
What is claimed is: 
1. A photometric apparatus for a single lens reflex camera and of the type in 
which an exposure value is determined by photometry of light which is 
transmitted through a photographic optical system and reflected by at least 
one of the surfaces of a shutter blind and a film, comprising a photoelectric 
transducer element for receiving reflected light from at least one of the 
surfaces of a shutter blind and the film; 

US4064517: Photometric apparatus for single lens reflex camera 
Dec. 20, 1977 / Aug. 24, 1976 
A photometric apparatus for single lens reflex camera and of the type in 
which an exposure value is determined by photometry of light which is 
transmitted through a photographic optical system and is reflected by at 
least one of the surfaces of a shutter blind and a film, said apparatus 
comprising a photoelectric transducer element for receiving light reflected 
by at least one of the surfaces of a shutter blind and a film, and an 
operational amplifier for biasing the photoelectric transducer element to 
maintain the voltage applied thereacross substantially null, thereby enabling 
a photometric output of the photoelectric transducer element to be 
effectively derived even when the amount of light received is minimal. The 
photometric apparatus, including a photoelectric transducer element, a 
photometry switch and associated circuitry are mounted upon a printed circuit 
board mounted within the camera to position the transducer element to receive 
reflected light from the film or the shutter. 

US4072961: Light measuring circuit for automatic exposure control 
Feb. 7, 1978 / Aug. 5, 1976  ( Minolta)
Light measuring circuit for camera automatic exposure control measures scene 
light passing through the objective and reflected at the film surface and/or 
the shutter curtain surface located at the exposre aperture of the camera. 
The measuring circuit is provided with a compensating circuit for 
compensating the light responsive output for the difference of light 
reflecting power of the surfaces of the film and the shutter curtain. The 
compensating circuit is actuated in a predetermined timing relationship with 
the travel of a shutter curtain. 

US4295720: Apparatus for determining light reflection from a focal plane 
shutter 
Oct. 20, 1981 / Jan. 7, 1980  (Olympus)
An apparatus for determining the amount of light reflected from a focal plane 
shutter includes a photoelectric transducer element which determines light 
reflection from the shutter blind surface and the film surface. The 
transducer element produces a photocurrent which charges an integrating 
capacitor. A correcting capacitor is disposed so as to be connected in 
parallel with the integrating capacitor during a part of the exposure time in 
order to correct the output voltage thereof for different reflectivities of 
the film surface and the shutter blind surface. The correcting capacitor is 
charged to the same voltage as that appearing across the integrating 
capacitor at the time the correcting capacitor is connected in parallel with 
the integrating capacitor. 

US4459007: Apparatus for reflection photometry of a single lens reflex camera 
July 10, 1984 / June 7, 1982 
( Olympus)
An apparatus for reflection photometry of a single lens reflex camera 
includes a first shutter blind, the surface of which exhibits a reflectivity 
which is nearly one-half the reflectivity of a film surface. During the time 
a photoelectric transducer element, used for photometry, receives light 
reflection from the surface of the first blind, an output from a photometric 
circuit is doubled so as to be substantially equal to the output produced 
when the transducer element receives light reflection from the film surface 
during the running of the first blind. 

US4367022: Exposure control circuit for camera of TTL reflective photometry 
type 
Jan. 4, 1983 / Jan. 25, 1982
(Olympus )
An exposure control circuit for camera of TTL reflective photometry type 
includes a shutter blind of a lower reflectivity than that of a film. The 
circuit is arranged such that until a given proportion of the film surface 
becomes exposed as a result of running of a first shutter blind, a correction 
semiconductor element is rendered conductive to supply a current, which 
represents a magnified version of minimal current from a photoelectric 
transducer element when reflected light from the surface of a first blind is 
incident on the transducer element, the current being supplied to an 
integrating operation. However, after the given proportion of the film 
surface has been exposed to increase the magnitude of the photocurrent, the 
correction semiconductor element is rendered non-conductive, thus allowing an 
integrating operation of only the photocurrent. 

US5184174: Photographic system with off-the-film exposure metering 
Feb. 2, 1993 / Nov. 19, 1991  (Kodak)
Off-the-film metering in a photographic film camera is improved by measuring 
actual film reflectivity at the time of film manufacture and recording a film 
adjusted exposure constant on a magnetic recording layer on the film. Camera 
apparatus is provided to read this film adjusted exposure constant value and 
generate an adjustable reference level representative of actual film 
reflectivity which is then used in confunction off-the-film metering 
apparatus to control exposure of the film in accordance with actual film 
reflectivity values rather than a fixed or assumed value. Measured film 
exposure aim may also be recorded at film production and used to control film 
exposure in the camera. 

Tim Hughes
Hi100@xxxxxxx



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