GB2266779A - An automatic focusing camera - Google Patents

Abstract

An automatic focusing camera comprises a variable focal length photographic lens (121, 122) and a prism (124) located in a finder. An auxiliary light projecting system (126, 127) projects a predetermined pattern image through the prism toward a photographing object. The image magnification of the finder is variable corresponding to the variation of the focal length of the photographic lens so that the magnification of said pattern image varies corresponding to the variation of the focal length of said photographic lens. <IMAGE>

Description

AN AUTOMATIC FOCUSING CAMERA The present invention relates to distance measuring devices for cameras, and more particularly, to a passive distance measuring device in which the optical axis of a finder and those of optical elements of the distance measuring device are dissimilar to each other.

Among conventional distance measuring devices provided with automatic focusing systems (AF systems), there is a passive distance measuring device which utilizes external light. The passive distance measuring device of an automatic focusing system is mainly employed in a lens-shutter type camera in which a photographic optical system, a finder and a distance measuring optical system of the AF system are separately arranged. A brief description will now be given of a lens shutter type camera having the conventional distance measuring device, with reference to Figs. 1 through 3 inclusive. A photographie lens 12, a finder (objective window) 14, and a light emitting window 16 for a built-in strobe are provided on a front panel of a camera body 10 with a release button 18 on a top surface thereof.

A pair of AF lenses 22, 23 of a distance measuring device 20 are disposed above the photographie lens 12 on the front panel of the camera body 10.

Figs. 2 and 3 are a plan and an elevational view of the distance measuring device 20.

Before being projected onto a distance measuring sensor 30, rays of object light passing through the pair of AF lenses 22, 23 are substantially inwardly refelcted from respective mirrors 24, 25 at right angles and passed through respective condenser lenses 26, 27 to become incident upon a mirror prism 28 where they are rearwardly reflected at right angles.

The distance measuring sensor 30 is, as shown in an elevational view of Fig. 4, provided with a light receiving mit equipped with a CCD (Charge Coupled Device) line sensor 32 having a number of light receiving elements erranged in a row. The line sensor 32 consists of two sections 32A. 32B disposed in the row and the luminous flux, of au object, passing through the pair of AF lenses 22, 23 is projected onto the respective line sensors 32A, 32B. Each light receiving element of the line sensor 32 submils the projected image of the object to photoelectric conversion and stores the image in the form of signal charge. Numeral 34 denotes a monitor sensor for finding an optimum signal charge accumulation time for line sensor 32.

A control system in the camera body is used for reading the signal charge stored in the light receiving elements of the line sensor 32, computing an objected distance through operations, and driving a focusing lens up to a focusing position according to the measured value of distance.

A description will be given of the realation of a distance measuring zone to a finder field in the aforementioned camera with reference to Fig. 5. In this camera, the finder 14 is interlocked with the zooming of the photographic lens 12 so as to charge its field magnification. Taking a distance measuring zone as the range of the object projected onto the line sensor 32 on a finder field 36, a distance measuring zone 37T for the telephoto posiiton is shown in Fig. 5.

The finder field 36 is provided with a distance measuring frame 38 for visualizing the distance measuring zone. When the photographic lens 12 in this state is caused to zoom toward a wide angle, the field magnification of the finder 14 reduces, but the size of the field frame 38 remains unchanged.

On the other hand, despite the zooming, the magnification of the distance measuring device 20 also remains unchanged. As a result, a distance measuring zone 37W on the finder field 36 becomes small at a wide angle position as shown in Fig. 5.

With reference to Figs. 6A arid in, a further description will be given of the relationship between the finder field 36 and the distance measuring zone in the cases of a telephoto and a wide angle position when the same object is photographed from the same position.

At the telephoto position, it is assumed that an object image 39 in the finder field 36 and a distance measuring zone 37T are those illustrated in Fig. 6A.

in this case, when the photographic lens 12 is zoomed toward tulle wide angle position, the field magnification of the finder 14 reduces. Consequently, the object image 39 in the finder field 36 becomes smaller down to the size shown in Fig. 613 at the wide angle position.

On the other hand, the size of the distance measuring zone relative to the object does not vary since the magnification of the distance measuring device 20 remains unchanged as stated above. In other words, the size of the distance measuring zone relative to the object image 39 is constant. As shown in Fig. 6B, the distance measuring zone 37W on the finder field 36 also becomes smaller as shown the object image 39.

In the conventional distance measuring device 20, the size of the distance measuring zone in the finder field 36 changes as stated above as the field magnification of the finder 14 changes. in other words, because the size of the distance measuring zone occupying the finder field 36 varies with the focal length of the photographic lens 12, a problem arises that an error in distance measuring may be made in relation to an object which is not intended for photography by a photographer.

In a camera equipped with an auxiliary projector for projecting a stripe pattern image onto a dark object or what offers a dim contrast to be photographed, the spot diameter (irradiation angle), if it has been adjusted to the distance measuring zone at a wide angle, for instance, will become wider than the distance measuring zone at the telephoto position leading to wasteful irradiation. The problem is that a long distance cannot be covered.

According to the present invention there is provided an automatic focusing camera comprising: a variable focal length photographic lens; and an auxiliary light projecting system for projecting a predetermined pattern image toward a photographing object; wherein the magnification of said pattern image varies corresponding to the variation of the focal length of said photographic lens.

Preferably, the camera further comprises a finder, wherein the image magnification of said finder is variable corresponding to the variation of the focal length of the photographic lens; and wherein said finder installs a prism therein, said predetermined pattern image being projected through said prism.

Reference is made to parent patent application number 9010384.7 from which the present application has been divided out and also to the following co-pending divisional patent applications: An example of the present invention will now be described with reference to the accompanying drawings, in which: - Fig. 1 is an elevational view of a known camera equipped with a passive distance measuring device; Figs. 2 and 3 are a plan and an elevational view of the optical system of the passive distance measuring device; Fig. 4 is an elevational view of the construction of a conventional line sensor; Figs. 5 and 6A, 6B are diagrams illustrating problems at a wide angle and telephoto position for the finder field of a conventional passive distance measuring device; Figs. 7, 8A , 8B, 9, 10A, 10B are diagrams illustrating problems posed by different object distances in a conventional passive distance measuring device; Figs, 11, 12A, 12B, 13, 14A, 14B are diagrams illustrating problems posed at a macro-photographic position in a conventional passive distance measuring device;; Fig. 15 is a diagram illustrating problems posed by a three-dimensional object for a conventional passive distance measuring device; Fig. 16 is an elevational view of the principal construction of a distance measuring sensor; Figs. 17A, 17B and 17C are elevational views of light receiving ranges of the distance measuring sensor shown in Fig. 16; Figs. 18A and 18B are diagrams illustrating finder fields for a wide angle and a telephoto position in a camera having a distance measuring device of Fig. 16; Figs. 19A, 19B 19C, and 20A, 20B, 20C are diagrams illustrating light receiving ranges in conformity with the construction and focal length of first and second modifications of distance measuring sensors, respectively;; Figs. 21A, 21B, 21C, 21D are diagrams illustrating solving problems caused by different object distances due to parallax: Figs. 22A, 22B, 22C, 23A, 23B, 23C and 24A, 14B.

24C are diagrams illustrating light receiving ranges of the line sensor in proportion to object distances at a wide angle, standard and telephoto time, respectively: Figs. 22D, 23D, 24D are diagramms illustrating divided forms of the line sensor at divided distance measuring time: Figs. 25A, 25B, 25c, 25D are diagrams illustrating solving problems caused by different object distances due to parallax; Fig. 26 is a schematic perspective view of a photographic range data reader; Fig. 27 is a schematic perspective view of a focal point regulator:: FIg. 28 is a block diagram illustrating a control circuit in a camera having the distance measuring device; Fig. 29 is a circuit diagram specifically illustrating the periphery of the line sensor in the control circuit; Fig. 30 is a timing chart illustrating timing of each part of the control circuit; Fig. 31A is a diagram of a circuit for controlling necumulation control time of the sensor; Fig. 31B is a @iming chart of the control time: Figs. 32 and 33 are operation flowchart of the present invention: Figs. 34A, 34B are diagrams illustrating optical paths of an auxiliary projector embodying the present invention; and Fig. 35 is a perspective view of the prism of the auxiliary projector.

The arrangement of an optical system in a camera will be referred to in relation to Figs. 16 through 18.

Fig. 16 is an elevational view of a distance measuring sensor 50.

This distance measuring sensor 50 has a pair of line sensors 52A, 52B symmetrically arranged in a horizontal row as in the case of the conventional distance measuring sensor 30 in Fig 4. However, each of the line sensors 52A, 52B is transversely longer than each of the conventional line sensors 32A, 32B.

An object image is projected onto each of the line sensors 52A, 52B via respective corresponding AF lenses 22, 23. A description will now be given of the construction ans operation of the line sensor 52A and a monitor sensor 54 onto which the object image introduced from one AF lens 22 is projected. The luminous flux of the object, which has passed through the AF lens 22, is projected over the whole range of the line sensor 52A. The range over the line sensor 52A thus subjected to image projection is defined as a light receiving range 53W. The range of the object thus projected within the light receiving range 53W on a finder field 56 of a variable finder 14 is defined as a distance measuring zone 57W.When the photographic lens 12 is a wide angle lens, a distance measuring frame 58 is formed so that the object within the distance measuring frame 58 formed in the finder field 56 of the variable power finder 12 is coincident with the object in a distance measuring zone 57W (Fig.

17A and 18A). Although the photographic lens 12 is a zoom lens capable of zooming over a range that covers a wide angle to a telephoto range, for convenience of illustration, it will be described as a multi focal length lens with three focal lengths, a wide angle, standard position and telephoto position.

When the fotographic lens 12 is adjusted to the standard position by zooming, the object within the distance measuring frame 58 is projected onto a light receiving range 53S as shown by slant lines in Fig.

17B. When the photographic lens 12 is further adjusted to the telephoto position by zooming, the object within the distance measuring frame 58 is projected to a light receiving range 53T as shown by stant lines in Fig. 176.

Distance measuring computations at a wide angle are carried out by utilizing the object image projected onto the light receiving range 53W, i.e., using signal charges accumulated by all the light receiving elements of the line sensor 52A, whereas in the standard position, distance measuring computations are carried out by using the light receiving elements within the smaller light receiving range 53S. Range-finding computations for the telephoto position are carried out by using the light receiving elements within the still smaller light receiving range 53T. In this way, the distance measuring zones 57W, 57S, 57T become coincident with the distance measuring frame 58, irrespective of the focal length of the photographic lens 12.

When one and the same object is photographed at the same range using the camera, the distance measuring zone 57W is coincident with the distance measuring frame 58 in a wide angle position as shown in Fig. ISA. when the photographic lens 12 at this position is zoomed out, the field magnification of the variable power finder 14 is increased as the focal. length of tlie photographic lens 12 changes, whereby an object image 59 looks larger as shown in Fig. 18B. As the range of the object image incident on the line sensor 52A via the AF lens 22 reamains unchanged, the range of the distance measuring frame the line sensor 52A tends to become larger as shown by an imaginary line of Fig. 18B, provided the whole line sensor 52A is used conventionally as before.

However, the range of the line sensor 52A for use is restricted to the light receiving range 53T in the telephoto position as shown in Fig. 17A which makes tile size of the ci Is tance measuring zone 57T on the finder field 56 likewise substantially as large as tlie distance measuring Frame 58 For the wide angle position.

As stated above, the size of the distance measuring zone 57 on the finder field 56 is made constant, irrespective of the field magnification, by rendering the breadth of the line sensor 52 greater than before and selecting the light receiving range of the line senzor 52, which is used in distance measuring, in proportion to the field magnification (focal length of the photographic lens 12) of the variable power finder 14. The distance measuring zone 57 thus becomes coincident with the distance measuring frame 58.

In other words, despite the alteration of the focal length and the magnification, the light receiving elements (light receiving range) for use in the line sensors 52A, 52B are selected so that the distance measuring zone 57 and the distance measuring frame 58 in the object finder field 56 become coincident with each other.

Furthermore, the photographic lens 12 is a zoom lens, althrough it has been described as a three focal length lens. When such a zoom lens is employed, the light receiving range can be finely divided in accordance with the focal length.

A description will now be given of an arrangement of light receiving elements of the line sensors 52A, 52B and a mode in which the signal charges atored in these light receiving elements are read.

The line sensor 52A shown in Figs. 17A, 17B, 17C comprises light receiving elements having three different breadths a, 2a, 3a. These light receiving elements are disposed symmetrically about an optical axis 0 with that which has a breadth of a as a standard.

The breadth of the light receiving range 53 is set at 2/3 for the light receiving range 53S in the standard position and 1/3 for the light receiving range 53T in the telephoto position with the light receiving range 53W in the wide angle position as the norm. In this case, 24 light receiving elements a in breadth are included in the light receiving range 53T for the telephoto condition, whereas the light receiving elements having a breadth of 2a are provided for the light receiving range 538 in the standard position outside those having a breadth a. The light receiving elements a and 2a included therein are equivalent to a breadth of 48a in total. In addition, the light receiving elements having a breadth 3a are provided for the light receiving range 52W in the wide angle position outside those having a breadth a and 2a.The light receiving elements having a breadth a, 2a, 3a included therein are equivalent to a breadth of 72a in total.

The breadth of light receiving is changed at the ratio stated above to process the output of the line sensor 52 an a 24-bit signal, irrespective of the light receiving range. I in otmlier words, a hit equivalent to the breadth a is processed as one bit in tIre telephoto position; a bit equivalent to the breadth 2a is processed as one bit in the standard position; and the light receiving element equivalent to tIre breadth 3a is processed as one bit in the wide angle position.

Figs. 19A, 19B, 19C show a first modification of the line sensor 52. In this modification, there are 72 light receiving elements having a breadth a and the light receiving ranges at tulle respective focal lengths are similar to those shown in Fig. 17. These light receiving elements are likewise processed as 24-bit signals at the respective focal lenghts.In other words, 24 light receiving elements are processed as one lit in tlie telephoto position; adjoining two light receiving elements are combined before being procesed as one bit in the standard position, and adjoining three light receiving elements are combined before being processed as otie bit in the wide angle position.

Figs. 20A, 2(1B, 20C show a second modification of the line sensor 52. The arrangement of light receiving elements in this second modification is similar to that which is shown in Fig. 19. Although the light receiving ranges at the respective focal lengths are similar to those shown in the first modification, bit processing differs. In this modification, each light receiving element is processed as one bit; in other words, it is processed as 24-bit data ii the telephoto position as 48-bit data in the standard position, and as 72-bit data in the wide angle position.

however , tlie ritimber of light receiving elements is riot limited to that which lias been defined in the embodiments above. Moreover, the number for tulle light receiving range may be altered as desired with orie bit as a minimum unit, depending on the focal length.

A description will now be given for solving problems resulting from parallax due to the Fact that the optical axis of the distance measuring device is displaced relative to that of the photographic lens with reference to Figs. 21 through 25.

A camera comprises AF lenses 61, 62 of a distance measurillqq device and a variable power finder 60, which are provided substantially in a horizontal row, and a photographic lens 63 disposed under the variable power finder 60. With this arrangement, an object image projected by the AS lenses 61, 62 onto a line sensor is transversely moved in proportion to the object distance. For this reason, the distance measuring zone relative to a distance measuring frames 68 in an object fiekd 66 is transversely shifted because of the object distance as shown in Fig. 8A, 8B.

The line sensor 64 is therefore formed longer in the transverse direction, irrespective of the object distance, so that an object image is received by light receiving elements of a line sensor 64. As shown by siant lines in Figs. 22A through 22C, 23A through 23C, and 24A through 24C, the light receiving range, i.e., the range of the light receiving elements for use is changed in proportion to the object distance.

With this arrangement, the shifting of the distance measuring zone 67 from the distance measuring frame 68 is decreased, irrespective of the object distance. F.igs. 22, 23 and 24 designate modes at a wide angle position, standard position and telephoto position respectively.

In this camera, the optical axis position of the variable power finder 60 is caused to move toward the optical axis oE the photographic lens 63 (downward in the drawing) in macrophotography to decrease the parallax of the photographic lens fi3 from the variable power finder 60. As aresult, the distance measuring zone 67 on the finder field lends to shift upward in macrophotography (Fig. 21D).

Line sensors 64C, 64D are therefore provided above line sensors 64A, 64B (Fig. 21C), and tIre lower line sensors 64A, 64B are employed for normal use in normal photography, whereas tlie upper line sensors 64C, 64D are employed for macro rise in macrophotography for distance measuring purposes. With this arrangement, the parailax is corrected to make the distance measuring frame 68 and the actual distance measuring zone 67 on the finder field coincident with each other. In the above-described camera, morcover, distance measuring is carried out using the light receiving elements for tlie widest range at each focal lenght of the photographic lens as the object distant remains unknown at the time of initial distance measuring.When the object is a three-dimensional object, there appear a plurallity of output peacks of light receiving elements (Fig. 15). As a result, their distances become impossible to be measured or otherwise it is left unknown one of the object is set for distance measuring.

The light receiving range is therefore divided into there sections (Figs. 22D, 23D 24D) and the ranges of the objects projected ontothe light receiving ranges 64&alpha;, 64ss, 64&gamma; are found.

respectively. The number of division of the light receiving ranges and their sizes are optional. Furthermore, the divided light receiving areas may be employed in a normal distance measuring operation wherein the distance measuring is only one executed.

Fig. 25 shows an arrangement of the optical system where tire Finder 60 arid tite AF leases 61 62 of the AF optical system are vertically disposed and these are further disposed next to t-.lie zoominy Hotographic lens (;3.

The vatiable power finder 60 is displaced relative to the optical axes of tIre AF optical systems 61, 62 and the distance measuring frame 68 mainly vertically shifts from distance measuring zone 67 on the finder field 66, depending on the object distance in normal photography. Since the optical axis of tic variable power finder 60 moves in the direction of tIre optical axis of the photographic lens 63 during macrophotography, the destance measuring zone 67 moves diagonally vertically with respect to the distance measuring frame 68.

The line sensors 64 are therefore vertically provided in three rows. The lowermost line sensors 64A, 64B are used for a short distance: middle line sensors 64C, 64D for an intermediate distance: and the uppermost line sensors 64K, 64F for a long disatnce and macro. Each of the line sensors 64 is transversely longer than the conventional one.

The lines sensors 64C, 64D for an intermediate distance are used first in normal photography to measure the object distance. Then selection is made determing which one of the line sensors 64 should be used on the basis of the range measured. The line sensor 64 thus selected is used to perform the distance measuring operations again in order to drive a focusing lens up to the focusing position based on the range measured.

Through the aforementioned operations, the parailax between the distance measuring zone 67 and the distance measuring frame 68 resulting from the difference in object distance is corrected, whereby the distance measuring zone 67 becomes coincident with the distance measuring frame 68 on the finder field, irrespective of the object distance. As a result, the object intended for photography by a photographer is Accurately focused. In this case, divided distance measuring is applied to a three-dimensional object.

Since the optical axis of the variabile power finder 60 is caused to move.

toward the optical axis of the photographic lens 63 during macrophotography in this camera, the distance measuring zone 67 upward with respect to the distance measuring frame 68 on the finder field 66.

The line sensors 64E, 64F for a long distance are selected during machrophotography.

Consequentely, the parailax is corrected as the optical axis of the variable power finder 60 meves, whereby the distance measuring frame 68 becomes coincudent with the distance measuring zone 67 on the finder field 66.

A description will now be given of a reader for reading data on the focal lenght of the photographic lens 12 for controlling the line sensor 64 in accordance with the focal lenght with reference to Fig. 26.

The photographic lens 12 zooms in conformity with the relative reciprocative movement of a vari-focal lens 1,1. A code plate 72 is stuck to the surface of a zoom cylinder 71 which moves a group of vari-focal lenses L1 as the cylinder moves linearly, the code plate idedntifying the position of the zoom cylinder 71 in the form of codes. the code plate 71 is formaed with 3-bit codes, each being a combination of conducting and insulating units Each code on the code plate 72 is ready by a brush 73 provided with a contact which slide-contacts the bits of each code. The code read thereby is decoded by a decoder 74 before being sent to a CPU 80 (FIg. 28B).

The CPU 80 stores focal lenght data corresponding to each code of the code plate 72, and data on the range of use of the line sensor in conformity with each focal lenght. The CPU 80 determines the range of use of the line sensor 64 according to the data (focal lenght) delivered from the decoder 74.

With refrence to Fig. 27', the focusing system will now be described. Focusing is regulated as a lens cylinder 75, holding a focusing lens 1,2, moves in the direction of the optical axis. Apin 76 extends from the lens cylinder 75 and engages with a screw 77 arranged in parallel to the optical axis. The screw 77 is driven to rotate by a focusing motor 78.

As the focusing motor 78 rotates, the lens cylinder 75 reciprocates the regulate the focal point. In this case, the direction and amount of rotation of the focusing motor 78 are controlled by the CPU 80.

A conductive plate 75n is stuck to the rear end portion of the lens cylinder 75 and a switch 70 having a contact 79a which slide-contacts the conductive plate 75a is disposed behind the conductive plate 75n. In this way, the contact 79a contacts the conductive plate 75a to turn it on when then lens cylinder 75 is located within a fixed range of movement, whereas when the lens cylinder 75 advances beyond a predetermined position, the contact 79a is detached from the conductive plate 75a to turn it off. The switch 79 is used to detect whether the lens cylinder 75 is located at a standard position.

A description will now be given with reference to Fig.

28 of a control system configuration of a camera to which the embodiment shown in Fig. 16 is applied.

This camera is a lens-shutter type camera equipped with a distance measuring device, a power zoom lens and a pop-up strobe.

The CPU 80 collectively controls operations of the camera relating to distance measuring, metering, exposure and the like. The CPU 80 performs each control operation in accordance with programs stored in its internal memory.

When a film is loaded, the CPU 80 reads the film sensitivity data via a DX code reading means 81 and stores the data in an internal RAM as the ISO speed data of the film.

The CPU 80 further reads the focal lenght data of a photographic lens 82 (12) and data on whether macro is employed and stores the data. These operations are performed via a focal lenght data reader 83 and a decoder 84 configured in a manner similar to that which is shown in Fig. 26. Based on the focal lenght data and the like, the CPU 80 selects the light receiving range of the line sensor 64 and the line sensor 64 for use.

There are also provided switches for actuating the CPU 80, including a metering switch 85, a release switch 86, macro switch 87, and a strobe pop-up switch 88. When the metering switch 85 is turned on, metering and AF operations are performed and when the release switch 86 is turned on, an exposure operation is performed. The macro switch 87 is turned on when the photographic lens 82 moves to a macro area. When the strobe pop-up switch 88 is turned on, a built-in strobe is popped up to make the strobe ready for light emission.

In tulle metering operation, a Light measuring circuit 90 subjects a signal, produced by a light receiving element 89 which has received object light, to predetermined processes such as logarithmic compression and the feeds the results to the CPU 80. This CPU 80 performs metering operations using the film ISO speed data stored in the memory according to the metering signal and determines a diaphragm value and a shutter speed.

In the distance measuring operation, switch circuits 91, 92 are actuated and the line sensors for use are selected. Then, the line sensors 64 are caused to start accumulating signal charges.

After tIie lapse of a predetermined ti.me, the line sensors 64 are caused to stop accumulating the charges, which are then read as electric signals. A monitor circuit shown in Fig. 31A. for instance, determines the timing at which the charge accumulation is suspended.

The accumulated signals rend from the line sensors 64 are supplied via the switch circuits 91, 92 to A/I) converters 93, 94, respectively. The signals thus supplied thereto are converted to predetermined respective digital signals or a predetermined light receiving element unit and are supplied to the CPU 80. The CPU 80 is not designed to subject all the accumulated signals to A/D conversion and to read the resulting signalsm but to subject to A/D conversion only the signals accumulated by the light receiving elements within the light receiving range selected in accordance with the focal of the photographic lens 82 and to simultaneousity store the resulting signals. Accumulation control, reading, A/D conversion and the like are exercised on the basis of the pulse generated by a clock generator 95.

The CPU 80 treats the signals read and stored from a pair of selected line sensors 64 as standard and reference signals respectively and performs operations to obtain an object distance. Based on the object distance, the CPU 80 starts an AF motor 96 (78) and driives the focusing lens 1,2 up to a focusing position via a lens drive 97. Numeral 98 denotes a position detecting switch for detecting a standard position of the lens drive 97.

IÄn the exposure operation, the diaphragm is contracted to the set diapragm value via a shutter drive circuit 99 according to the predetermined diaphragm value and the shutter speed, and opens or closes the shutter at the set shutter speed to expose the film.

When the exposure is terminated, one frame of the film is wound up by an auto winder (not shown) to charge the shutter, the film may be wound up manually.

A built-in pop-up strobe 100 is provided.

The pop-up strobe 100 is provided with a light emitting circuit 101 and a light emittng unit 102 detachably fitted to the camera body.

In the metering operation stated above, an infinder indication unit 103 provided in the finder field is flickered to call attention to the use of the strobe when the object luminance is judged lower than a predetermined value. The in-finder indication unit 103 is also capable of indicating a @ocused state.

When the strobe pop-up switch 88 is turned on, the light emitting unit 102 projects to set up a condition in which strobe light can be emitted. When the release switch 86 is turned on this condition, the light emitting nuit 102 emits light at predetermined timing.

Numeral 104 in Fig. 28 denotes a battery for supplying power the CPU 80, the pop-up strobe 100 and the like, whereas 105 denotes an X contact switch for compeiling the light emitting unit 102 to emit light and it is turned on/off interlockingly with the shutter drive circuit 99.

A description will now be given of the operation of reading the signal charge from the line sensor 64 with reference to Fig. 29. The line sensors 64A - 64D are provided on noe IC (Integrated Circuit) board. The pair of line sensors 64A. 64B and the other pair of line sensors 64C. 64D are formed in a transverse row, and the line sensors 64 in the respective pairs are disposed vertically in parallel to each other. the luminous flux of the object that has passed through the AF lenses 61. 62 is projected onto the separate areas of the line sensor 64. i.e., the line sensors 64A. 64C on the left-hand side and the line sensors 64B. 64D on the right-hand side, and converted by the respective light receiving elements into signal charges.The signal charges accumulated by the respective light receiving elements of the line sensor 64 are transferred to a horizontal transfer unit on the board one at a time.

This horizontal transfer unit is provided for each line sensor 64 and a pair of read transfer units are provided outside the horizontal transfer unit. With respect to the signal charges transferred to the read transfer units, the signal charges in the left-hand line sensors 64A, 64C are transferred to the left-hand read transfer unit in steps and are alternately read one at a time from the read end of the read transfer unit.

The signal charges stored in the right-hand read transfer unit are also alternately read one at a time from the end of the right-hand read transfer unit.

Since the operation of the each line sensor is similar to that of the other, the operation of the line sensors 64B. 64D on one side will be described.

The clock generator 95 under the control of the CPU 80transfers the signal charges accumulated by the respective light receiving elements of the line sensor 64 to the horizontal transfer units one at a time and outputs an accumulation control signal # T for stopping the accumulation of the signal charges and a read pulse for use in reading the signal charges transferred to the horizontal transfer units in sequence. The pulse generated by the clock generator 95 is supplied to not only the line sensor 64 but also to a counter 106 and the A/D converter circuit 94.

The CPU 80 sets a count to a count setter 107 in accordance with the range of use of the line sensor 64 for fetching the signal charge. The count setter 107 supplies the set value to a count comparator 108. On the other hand, the counter 106 counts the number of read pulses generated by the clock generator 95 and supplies the count to the counter comparator 108. The counter comparator the set value with the count and supplies a coincident signal to the CPU 80 only when both coincide with each other.

Upon receipt of the coincident signal, the CPU 80 converts the signal supplied to the line sensor 64 vin the circuit 92 to a discharge signal by operating the A/D converter 94. The switch circuit 92 is used for alternatively connecting the read terminals of the line sensors 64B. 64D to the A/D converter 94 with the switching operations are controlled by the CPU 80.

A description will now be given of the aforementioned operations after the termination of charge accumulation on the part of the line sensor 64. An accumulation control signal is produced from the clock generator 95 and when the charge accumulation is completed by transferring the electric charges in the respectinve light receiving elements of the line sensor 64 to the horizontal transfer units one at a time, the CPU 80 causes the clock generator 95 to output the read pulses.

The CPU 80 selects which one of the light reveiving ranges of the line sensor 64 is to be utilized on the basis of the focal lenght data of the photographic lens 82 supplied by the decoder 84 and the data derived from the macro switch 87 and sets the value obtained from the counter setter 107 and further selects either on the contacts of the switches 91, 92. In this case, the line sensor 64B and the telephoto light receiving range 64T in normal photography.

The clock generator 95 outputs the read pulses with a predetermined period, whereby the signel charges accumulated by the respective light receiving elements of the line sensor 64 are suplied to the switch circuit 92 as electric signals with a predetermined period. However, because no coincident signel is delivered from the count comparator 108 unit and the change signal of the lifgt receiving range G4T is supplied, the CPU 80 fetches no signal. The comparator circuit 108 compares the set value supplied by the count setter 107 with the number of read pulses generated by the counter 106 and outputs n coincident signal when both coincide with cach other.

The CPU 80 then fetches the signal produced by the line sensor 64 by starting the A/D converter 94 when the delivery of the coincident signal is detected and stores the signal in a storage memory area thereof. Each of the light receiving elements (bits) is responsable for the aforemantioned process. When the signals from two or three light receiving elements are added processed as one bit for the standard or telephoto position, the signals delivered by the two or three light receiving elements are subjected to A/D conversion in the A/D converter circuit 94 and added up in the CPU 80 before being stored in the RAM The siganals produced from the pair of line sensors on both sides are fetched by the CPU 80 via the read and a data bus for common use.Consequently, signal data 1 on one side and signal data 2 on the other ncan alternytely be loaded onto the data bus by changing the timing of a transfer signal.

When the first round of the signals accumulated in the line sensors 64A, 64B, are read and stored completely, the CPU 80 performs predetermined distance measuring operations according to the data thus stored to obtain the object distance. Then the CPU 80 selects the light receving range propor tional to the object distance, resets the count to the counter seter 107, and starts redaing the new signals accumulated in the line sensors 64A, 64B.

During the operation of readding and storing the signals, the CPU 80 performs the predetermined distance measuring operations acording to the stored data to obtain the object distance, starts the focusing motor 96 (78) according to the value thus obtained, and drives the focusing lens L2 mup to the focusing position.

Each of the aforementioned operations is performed by the CPU 80 in accordance with the program stored in its ROM.

A description wil now be given of a configuration of a circuit for controlling signal charge accumulation time of the line sensor 64 with reference to Fig. 31A.

A monitor sensor 110 is provided near the line sensor 64A. The monitro sensor 110 measures the amount of light incident on the line sensor 64 and controls the charge accumulation time of the line sensor 64 to make the time optimal.

The monitor is divided into section which correspond to the light receiving ranges 64T, 64S, 64W of the line sensor 64 for use: namely, a central section 110A; Intermediate sections 110B, 110B on both sides thereof; and outer sections llOC, llOC on both sides of the respective intermediate sections. only the central section 110A is used for the telephoto position; the central section 110A and the intermediate sections llOB, llOB are used for tire standard position; and all of the sections 110A, 110B, 110C are used for the wide angle position.

The outputs of the sections of the monitor sensor 110 are connected to inverted input terminals of respective comparators 111, 112, 113. Reference voltages Vr1, Vr2, Vr3 are applied to the inverted input terminals of the respective comparators 111, 112, 113. When the output level of the nmonitor sensor 110 drops below a predetermined value, the output of the comparators becomes "H." the outputs of the comparators 111, 112, 113 are connected to one input of respective AND gates 114, 115, 116. Output terminals A, B, C of an output switch circuit 117 are connected to the other Inputs of the rsespective AND gates 114, 115, 116.

While the output of the output switch circuit 117 remains at "H", the outputs of the AND gates 114, 115, 116 change from "H" when the output of the line sensor 64 changes to "H".

The outputs of the AND gates 114, 115, 116 are connected to the input of an OT gate 118. The output of the OR gate 118 consequently changes from "L" to"H" when any one of the outputs of the AND gates changes to "H." The output of the OR gate 118 is applied to a #T generator 119 in phase with clock generatorv 95. The #T generator 119 outputs an accumulation control signal #T for stopping the line sensor 64 from accumulating electric charges when the output of the OR gate 118 changes to "H." When the acumulation control signal #T is produced. the line sensor 64 transfers the signal charges accumulated by the light receiveng elements to the horizontal transfer units one at a time to terminate the accumulation of signal charges.

The operation of the electric charge acumulation circuit thus arranged will now be described with reference to Fig. 31B. When an object image is projected onto the monitor sensor 110, the output potential of the monitor sensor 110 begins to drop. The droppng speed is proportional to the bvrightness of the object thus projected. In other words, the brighter the object is, the faster the output potential drops, whereas the darker the object, the slower the potential drops.

When that potential becomes equal to the potential (Vr) of the non-inverted input terminal. the outputs of the comparators 111, 112, 1113 change to "H." A predetermined reference voltage Vr is kept applied to the non-inverted input terminals of the comparators 111, 12, 113. When the potential of a diviede sections 111A, 110B, 110C, becoimes equal to the references voltage, the outputs of the comparators 111, 112, 1113, to which the outputs of the divided sections 110A, 110B, 110C have been applied, change to "H." All or one of the output terminals A, B, C of the output switch circuit 117 is set to "H." by the CPU 80 in proportion to the focal lenght of the photographic lens. In this embodiment, the output terminals A, B and C are set to "H" for a wide angle position; the output terminals A and B are set to "H" for a standard position; and only A is set to "H" for a telephoto position. As a result, if the corresponding output terminal A, B or C remains at "H" when the output of any of the comparators 111, 112, 113 becomes "H", the outputs of the AND gates 114, 115, 116 become "H" and the output of the OR gate 118 also becomes "H", whereby the accumulations conttrol siganl #T is delivered from the #T generator 119 to make the line sensor 64 terminate the accumulation of electric charges. Although it is preferred to arrange the monitor sensor 110 in conformity with the light receiving range, it may be left undivided.

With the above-described operations, optimum electric charge acumulation time corresponding to the object luminance is obtained. The reference voltage Vr is determined in conformity with various conditions such as standard of line sensor and the monitor sensor. the area of the divided monitor sensor and the like. In this case, the CPU 80 outputs a signal for causing the accumulation control signal #T to be produced after the lapse of a predetermined time even though the output potential of the monitor sensor may not drop below the reference voltage.

A descriuption will now be given of the operational sequence of the camera having the circuit configuration stated above with reference ti Figs. 32.

33. These poperations are performed by the CPU 80 in accordance with the programs stored in the Internal memory of the CPU 80.

When the power supply it turned on, the main routine shown in Fig. 32 is entered first.

In the main routine, a decision is made on whether or not the metering switch 85 has been turned on and @ it has not been turned on, the operation is repeated until it is turned on (S1).

When the metering switch 85 is turned on, the measuring circuit 90 starts to begin metering (S13).

Then the switching conditions of the macro switch 87 and the strobe pop-uop switch 88 are checked (S15).

Further, metering opeartions are performed according to the metering signal from the measuring circuit 90 (S17).

The CPU 80 receives the focal length data of the photographic lens 82, selects the light receiving range of the line sensor 64 and the line sensor 64 for use on the basis of the focal length data, causing the line sensor 64 to accumulate signal charges thereby, performs distance measuring operations by reading the A/D converted signal, and performs the AF process for driving the focusing lens 1.2 up to the focusing position via the AF motor 96 according to the value obtained from the distance measuring operations (S19).

On terminating the AF process, the CPU 80 performs an indication process for cuasing the in-finder indication unit to illdicate a focused state or for calling attention to the rise of the strobe in the case that the object luminance indicates a value for calling atention to the use of the strobe during the luminance operations (S21).

The CPU 80 then checks whether or not the release switch 86 has been turned on and if it has not been turned on, returns to S11 to repeat the aforementioned process, whereas if the release switch 86 has been turned on, the CPU 80 performs the exposure process by driving the shutter drive circuit 99 and then returns to S11 (S23).

The basic operation of the camera has been described above.

A description will now be given of the AF process for use when a three-dimensional ovject is photographed. A object at the shortest distance is foacused when it is judged a threedimensional one as a result of division distance measuring: When a strobe is employed, an object at the shortest distance is focused within the possible appropiate irradiation range of the strobe.

The operation stated above will be described with reference to Fig. 33 showing the AF subroutine (S19) of Fig. 32. When the subroutine is enetered, CPU 80 receives data from the photographic lens 82 (data of focal length and that of macro switch 87) to make a decision on whether it is macro.

If it is not macro, thge CPU 80 selctes the line sensors 64A, 64B and also the range of use (Figs. 22A, 23A, 24A), depending on the focal length. Then CPU 80 reads the signals of the line sensor 64 accumulated within the range of use and performs distance neasuring operations (S37, S39).

The CPU 80 makes a decision on whether the object is a three-dimensional one from the results of distance measuring operations and if it is not a threedimmensional object, selcted the light receiving ranges 64S, T, W acording to the computed distance measuring value (S41, S43, Figs. 22A through 22C, Figs. 23A through 23C, Figs. 24A through 24C). The CPU 80 reads the signals accumulated by the light receiving elements of the line sensors 64A, 64B, confirming the conditions thus selected for storage, and then performs distance measuring operations after storing all the signals (S43, S45).

The CPU 80 makes a decision on whether the strobe is to be used from the on/off condition of the strobe pop-up switch 88. If it is not to be used, the CPU 80 drives the AF motor 96 according to the distance measuring value nad returns to the main routine after driving the focusing lens 1,2 to the focussed position (S47, S49).

When the photographic lens 82 is macro, the CPU 80 proceeds to S51 from S33, where whether or not macro was determined, and selects the line sensors 64C, 64D for macro. The cPU 80 then reads the signals accumulated by the line sensors 64C, 64D and performs distance measuring operations (S53, S55). Then, the CPU 80 drives the focusing lens 1,2 to the focusing position via the AF motor 96 according to the computed distance measuring value and return to the main routine (S49).

When the object is not macro but a threedimensional one, the CPU 80 proceeds from S41 to S57 and selected the divided light receiveng ranges 64&alpha;, 64ss, 64#, (Figs. 22D, 23D, 24D) for the threedimensional object. Based on the signal of each light receiving range, the CPU 80 performs respective distance measuring operations. i.e., divided distance measuring operations and selects the computed value at the shortest distance among them (distance neasuring object distances) before proceeding to S47 (S59).

While the strobe pop-up switch 88 is heid on, the CPU 80 proceeds from S47 to S61 to receive the possible appropiate irradiation range of the strobe and checks whether distance measuring value computed in S45 or S59 is within the possible appropiate irradiation range of the strobe (S63). If it is not within the irradiation range, the CPU 80 displays an alarm by means of the In-finder indication unit 103 before performing the lens driving process(S65, S49) and if it is within the irradiation range, performs the lens driving process immmediately (S63, S49). It is possible for the release button (numeral 18 of Fig.

1) to be locked against pushing when any one of the computed distance measuring values is not within the irradiation range of the strobe (numeral 19 of Fig. 1).

With the above-described operations, ,the distance measuring zone 67 is made to coincide withn the distance measuring frame 68, irrespective of the focal lenght, macro or object distance, and the distance mréasuring and automatic focusing operatiuons are performed in that coincident state. Moreover, a three-dimensional object at the shortset distance can also be focused.

If it is judged that the distance measuring value at the shortest distance selected in S59 is not within the possible appropriate Irradiation range of the strobe in S63, a distance measuring value being within the possible appropriate irradiation range of the strobe is scarched for from among a plurallity of distance measuring values computed in S59 in order that the focusing operation may be based on the selection of an applicable distance measuring value. With the performance of the operation above, an object at least within the distance measuring zone 67 may be photographed at a suitable focus point and a suitable exposure value, using a strobe when a plurality of objects are photographed.

A passive distance measuring device offers inferior distance measuring precision for a dark object (whose luminance is lower than a predetermined value) or that lacks contrast on the surface such as a white wall. With the present invention, an auxiliary projector element is arranged near the finder. This state is shown in Figs. 34A, 34B.

The finder is a variable power finder whose field magnification varies interlockingly with the zooming of the zoom lens. The objective lans consisits of two variable focussing lenses 121, 122 capable of relative reciprocation, whereas an ocular consisits of one fixed lens 123. There are disposed a prism 124 and a half mirror 125 between the variable power lens 122 and the fixed lens 123. In addition, there is arranged a light emitting element (e.g., infrared) 126 having a wavelength of over 700 nm (nanometer) outside the optical path of the finder toward the half mirror 125.

In front f the light emitting element 126 is a pattern 127 for forming a stripe pattern. Efficiency will be increased if the half mirror 125 is one which reflects a wavelength of over 700 nm at an angle of 45 degrees and allows visible light to pass therethrough.

The variable power lenses 121, 122 interlock with the zooming of the zoom lens via an interlocking mechanism and vary the field magnification of the finder in proportion to the focal length of the zoom lens by relatively reciprocating themselves. in other words, the finder field is made to substantially coincide with or be slight smaller than the photographic image plane, despite the zooming. The interlocking mechanism may be that the variable power lenses 121, 122 are relatively reciprocated by siding a cam plate provided with a cam groove by means of a zoom motor, using cam follower pins attached to the variable power lenses 121, 122 and mating with the cam groove.

The optical paths in this embodiment will now be described with reference to the drawings. The prism 124 is composed of three triagle prisms (refer to Fig. 35). The light beam passed through the variable power lenses 121, 122 and introduced through a plane 124a of the prism 124 is downwardly reflected from an include 124b at a right angle, backwardly reflected from an incline 124c as viewed from the surface of the drawing, upwardly refelcted from an incline 124d, reflected again from an incline 124c to the right at a right angle and radiated out of a plane 124f. The light beam thus radiated out is passed through the half mirror 125 and the fixed lens 123 and the comes into a photographer's sight.

On the other hand, an auxiliary light beam mitted from the light emitting element 126 is reflected from the half mirror 125 toward the prism 124, introduced from the plane 124f into the prism 124 and passed through the opposite optical path before being radiated out of the plane 124a. Then the light beam is passed through the variable power lenses 122, 121 and radiated out of the camera to irradiate the object. The auxiliary light beams sent out of the light emitting element L 1 26 nre consequenly condensed by tIre variable power lenses 122, 121 so as to irradiate the object.

The converging amount, by means of the variable power lenses 122, 121, is low for a wide angle position and high for a telephoto position. In other words, a wide range is irradiated for a wide angle position, whereas a narrow range is irradiated for a telephoto position. As a result, an object can be irradiated corresponding to the light receiving range selected in proportion to the focal length. Since the irradiation area for a telephoto position is narrowed for the telephoto position, an object at a long distance can be irradiated.

The auxiliary projector with the present invention is such that light is projected by utilizing the variable power lens in the variable power finder to make the angle of irradiation changeable in proportion to the magnification whereby a suitable range can be irradiated in conformity with the distance measuring zone.

Claims (3)

1. An automatic focusing camera comprising: a variable focal length photographic lens; and an auxiliary light projecting system for projecting a predetermined pattern image toward a photographing object; wherein the magnification of said pattern image varies corresponding to the variation of the focal length of said photographic lens.

2. A camera according to claim 1 further comprising a finder, wherein the image magnification of said finder is variable corresponding to the variation of the focal length of the photographic lens; and wherein said finder installs a prism therein, said predetermined pattern image being projected through said prism.

3. A automatic focusing camera as claimed in claim 1 and substantially as herein described with reference to figures 16 to 55.