The invention relates to a method for the recording of pictures, preferably living pictures, by means of a camera and simultanous recording of sound connected to the pictures by means of one or more microphones being displaceable in relation to the camera.

The invention also relates to an embodiment of a camera and one or more microphones for carrying out the method.

By carrying out the prior known method of recor¬ ding of pictures and sound the location of the microphones depend on and is limited by the recording field of the camera, and the size of this recording field depends on the lens system of the camera, of its adjustment for focusing in the recording field, and of the size and shape of the normally rectangular field of vision of the camera. Sound for films and TV is normally recorded by a sound assistant guiding a microphone being suspended at the end of a movable long rod, above the heads of the actors. It is the task of the sound assistant to . guide the microphone so that it follows the actor as closely as possible in the recording field of the camera, but without the microphone being visible in said field. By cameras carried on a camera dolly, and by which zoom objectives are used, the boundary surfaces of the recording field are so varying that it takes a great ex¬ perience and expertise to guide a microphone optimally. Since a sound volume fades with the second power of the distance from a sound source, a displacement of only 20 cm of the location of a microphone in relation to the sound source may be crucial for the quality of a sound recording.

By carrying out the known method it frequently happens that a microphone unfortunately is taken into the recording field of a camera, which means that a new recording must be made.

It is the purpose of the invention to reduce the

risk of a microphone being taken into the recording field of a camera during the recording of pictures and sound.

The method according to the invention is charac¬ terized in that one or more signal wave fields are formed, each passing closely outside or touching a boundary surface for the recording field of the camera, that signals for the formation of said signal wave fields are emitted from one or more signal wave transmitters, and that the signals might be received and transmitted on e.g. by reflection from one or more microphones to respective microphone-guiding receivers by the reflected signals.

Thereby it is achieved that some signal fields can be arranged around an area to be filmed. According to the invention the signals may consist of sound waves or of electromagnetic waves, e.g. light or radio waves. The reflected signals can be conceived by the eyes or ears of a microphone operator or received by an apparatus converting the signals so that the operator can conceive them, or which apparatus automatically guides a microphone. If a microphone then is about to be taken into the area to be filmed, the microphone will already have entered a signal field and therefrom have transmitted, e.g. reflected a signal, which informs a signal receiver, e.g. a microphone operator, that now the limit of the microphone displacement has been reached. It is thereby possible to prevent a microphone being entered into the recording field and to prevent a new recording having to be made due to a microphone having been erroneously guided. The signal wave fields may also be placed inthe very area to be filmed and may possibly confine the actual area. The signals for this may be ultrasonic signals or signals based upon infrared light.

An embodiment of a camera and one or more micropho¬ nes for carrying out the method may, according to the invention, be characterized in that one or more signal transmitters is or are mounted in respective holders on the camera, and that one or more microphones has or have means for receiving and sending on of the signals received from the

signal transmitters.

Since the signal transmitters thereby have been arranged so closely to the camera as possible is achieved that the signal fields can be arranged closely to the normally rectangular recording field of the camera. The warning signals from the reflecting means will not be apparent until the microphones are quite close to the recording field. The displaceability of the microphones will thereby be limited as little as possible. Since the signal transmitters have been mounted on the camera, the location of the signal fields in relation to the recording field will remain unchanged during the displacements or motions of the camera.

An embodiment of a camera and one or more micropho- nes may according to the invention also be characterized in that one or more of the signal wave transmitters is or are laser light transmitters transmitting laser light of a wavelength of about 800 nm and being adapted so that the signals are emitted forward in relation to the camera in one or more fan or carpet shaped bunches of laser beams, and equipped with guiding means to guide the direction of a light bunch concurrently with an alteration of the adjustment of the camera optics so that the light bunch intersects the picture field plane corresponding to the camera optics in a belt situated outside, preferably immediately outside and parallel to one side, preferably an upper side of the picture field corresponding to the optics, and that the microphones have been provided with laser light reflecting zones, preferably in the form of fluorescent plates. Thereby an optimum effect is achieved, namely that well defined signal fields may be arranged quite closely to the recording field of the camera, that the laser light is nearly invisible to the human eye and totally invisible for the emulsion of a film and the picture tube of a TV camera, and that a fluorescent zone or plate is shining powerfully, e.g. in the form of a luminous line, when it is hit by laser light and thereby gets clearly visible for a microphone

operatør, immediately before the microphone has reached a boundary surface for the recording field of the camera.

The invention will now be described in more detail in connection with an embodiment of a camera or one or more microphones for carrying out the method according to the invention and with reference to the drawing, in which fig. 1 shows a camera with a zoom-objective, a laser light transmitter and a microphone with a flourescent plate, fig. 2 shows the laser light transmitter seen from outside, and fig. 3 shows the inner parts of the laser light transmitter.

Fig. 1 shows a camera 2 with a signal wave field source, here in the form of a laser light transmitter 1, the latter being arranged in a holder 8 on the camera 2. The laser light transmitter 1 emits or transmits a fan or carpet shaped bunch of laser light having a wavelength of about 800 nm. The carpet intersects the plane of the picture field 5 of the camera 2 in a belt 3 lying parallelly with and immediate¬ ly outside the upper side of the picture field. A microphone 6 which can be guided manually by a microphone operator, has been provided with a flourescent zone or fluorescent plate 7 mounted at the lower edge of the microphone. The microphone 6 has been shown in a position in which its fluorescent plate is situated immediately above the fan or carpet shaped bunch of laser light waves. If the microphone 6 is lowered from this position and down into the light bunch, the fluorescent plate 7 will at once be hit by laser light. The fluorescent effect of the plate will make it shine powerfully when hit by the almost invisible laser light. The reflecting light will be visible at a distance of at least 20 m from the camera, even in broad sunshine. Thus, the microphone operator gets a visible warning if the microphone is about to be taken from above into the picture field of the camera.

If the location of the aforementioned belt 3 should be maintained in the picture field plane of the camera in a position immediately above the picture field after an alteration of the optics, the inclination 12 between the

lower side of the carpet formed light bunch and the centre line of the camera optics should be altered as a function of amendments in the optics.

Adjustment of the inclination 12 of the laser light transmitter may e.g. be made by means of bushbuttons 9 located at the upper side of the laser light transmitter 1, and which relate to the sizes of the optics used, cf. fig. 2.

The mechanical adjustment is made by means of a step motor 10 with a threaded shaft 11 which amend the in- clination 12 of the laser light transmitter. By a push on one of the pushbuttons 9 for a given size of the optics, a microprocessor 13 transmits a corresponding number of impulses to the step motor 10, which makes a given number of rotations for achieving the correct inclination 12, cf. fig. 3, and thus a location of the belt 3 immediately above the upper side of the relevant picture field. When a zoom objective is used, an impulse transmitter 14 is mounted in engagement with the toothed rim 15 which a priori has been used for motor adjustment of the picture size, cf. fig. 1. When a zoom elector button 16 on the upper side of the laser light transmitter, cf. fig. 2, has been pushed, the signals from the impulse transmitter 14 will be transmitted to the step motor 10 in such a way that the inclination 12 is amended synchronously with the amendments of the zoom objective so that the belt is located as mentioned above.

In order to compensate for mechanical variations by different cameras and zoom objectives and for permitting a zone of a few centimeters, in which the fluorescent plate 7 of the microphone is illuminated without being part of the picture, the laser light transmitter 1 has a 0-point adjust¬ ment 17 with the opportunity of a manual adjustment up and down of the inclination 12.

The laser light transmitter may have dimensions as a large matchbox. It might via a change-over switch 18 be supplied with current, either from internal batteries or from the current supply of the camera.

If sound waves are used for the signal wave

transmitters, said sound waves are preferably within the ultra short wave area, permitting the formation of a well defined fan or carpet shaped signal field. Here the micropho¬ nes themselves may transmit ultra sound signals together with the sound recorded. After the ultra sound signals having been filtrated from the microphone signals, they can be processed and caused to form audible or visible signals for the microphone operator or guiding signals for a microphone guiding robot. The reason for the selection of laser light with a wavelength of about 800 nm, e.g. ± 10% is that said light - contrary to visible laser light, is invisible to the human eye and to the picture tube of a TV camera as well, and can practically not influence an unexposed film emulsion. This particular laser light can be made visible by hitting a surface being treated with a fluorescent material which only shines powerfully, when light of this particular wavelength hits it. Consequently, when a microphone is hit by the carpet formed bunch of laser light beams, a warning stripe of light will be formed on the microphone itself.

The invention is not limited to the use of laser light as source of the signal wave field, since other sources as mentioned above may be used. The signal wave field does not need to be placed outside the recording field, but may be inside as well as outside, surrounding this field.1