Treasure of optics
Treasure of optics ( Arabic كتاب المناظر, DMG Kitāb al-Manāẓir , Latin De aspectibus or Perspectiva ) is a seven-volume script written by the Arabic scholar Alhazen (965-1039 / 1040), in which, among other things, optical, physical and meteorological topics are dealt with. It is partly based on older writings and views of Greek philosophers, but also contains numerous revolutionary new theories by Alhazen himself. The book was translated from Arabic into Latin at the end of the twelfth century, making it accessible to the western world. It was printed by Friedrich Risner in 1572 . It had a great influence on medieval science and is considered a starting point for the development of modern optics.
Summary of the individual paragraphs of the first five chapters of Book 1
according to the English translation
Chapter 1: Foreword to the entire book
1. There is confusion about vision. 2. Vision must be described by mathematics and science. 3. Scientists used to think that some form goes from the object to the eye. Mathematicians thought that rays go from the eye to the object. 4. Mathematicians have come up with different versions of the extra mission. 5. The truth must be extra or intromission, or something else. Unity can be achieved through thorough research. 6. My starting point is to be certain of the given, the unchangeable, the premises and principles that can be found by induction. Criticism of the premises and conclusions should be exercised for deepening purposes. The decisive factor is fair judgment instead of prejudice, the search for truth instead of influencing opinion. This is how the heart-filling truth can be known; so we can get certainty. God assists us in dispelling the clouding of the human spirit. 7. I have written 7 volumes on optics. 8. Please throw away my previous book on the treasure of optics.
Chapter 2: Studies on the properties of the sense of sight
1. A certain distance between the eye and the object is necessary to see. 2. The object must face the eye. Imagined connecting lines between the eye and the object must not run into an opaque obstacle. 3. Otherwise the object is invisible as long as it is in the same atmosphere and is not reflected. 4. Only that part is invisible whose connection line to the eye is interrupted by the obstacle. 5. Visibility is when there is an unbroken straight line between the point seen and the eye. 6. This can be tested experimentally with a construction made of a ruler and tube. 7. Look at the object through a straight tube, with and without the shielding of the tube. 8. By making it invisible, the straightness of the propagation of light is shown. 9. We conclude unequivocally: the visible lies on a straight line between the eye and the seen. 10. An object is visible when it contains light itself or receives it from another object, regardless of whether the eye is in light-filled air. 11. An object becomes invisible when it is small enough; depending on eyesight. 12. An object is invisible when it is transparent. 13. An object becomes invisible from a certain distance, depending on the object size. 14. and the brightness of the object (e.g. fire). 15. We conclude: the distance of visibility depends on the light in the object 16. and on its color (e.g. on a ship). 17. White is visible before bright colors, these in turn before dull colors. 18. We conclude: The distance of visibility depends on the color of the object 19. and on the eyesight. 20. Visibility therefore depends on the condition of the object and the eyes. 21. The eye does not see an object unless the object meets the stated conditions and the eye is undamaged. 22. Details become invisible even at smaller distances. 23. An object is perceived as shrinking when it moves away. 24. Close to the eye, the object appears to blur and disappear. 25. We state that a moderate distance is necessary for seeing. 26. We will next examine light and radiation, then the eye, and then discuss the process of seeing.
Chapter 3: Investigations into the properties of light and the types of light radiation
1. Self-luminous bodies shine in all directions and light up all surfaces facing as long as they are not shielded or too far away. 2. The radiation is straight when the air or the transparent body between the luminous and illuminated body is consistently similar. 3. This straightness is an unchangeable fact. We see them, for example, when light enters a dusty room through holes, gaps or doors. In a dust-free room, we can trace the straightness of an opaque object with the help of a straight rod. We find no light on crooked paths. 4. Likewise with moonlight and starlight that comes through a hole in the darkroom. If the eye looks from the light spot to the hole, it sees the star. 5. Light can also be intercepted with an opaque body at a straight distance. 6. This also works with fire, and can be checked with a straight rod pushed through the hole. 7. The straightness is also understandable in shadows, because here the straight connection to the luminous body is interrupted. 8. We conclude: Radiation from self-luminous bodies runs in a straight line. 9. The totality of the self-luminous body has more light than its parts, as we notice for example at sunrise and sunset. 10. Light shines on an object from that part of the sun that faces the object. 11. The same applies to a solar eclipse; every part of the sun shines. 12. Light comes in a straight line from every part of the sun, see solar eclipse. 13. This is also evident from the fact that the rays diverge from the hole in the darkroom. 14. Radiation goes in a straight line from every part of the sun to every opposite surface. 15. This also applies to the waxing and waning, rising and setting, and the eclipsed moon. 16. Likewise for fire, as we can test experimentally with a pipe in a copper plate. 17. Different variations of our experiment confirm that light from all fire is stronger than from part of it. 18. If we tilt the tube differently, we see that light shines in all directions from every part of the flame. 19. We conclude: Light emanates from every part of every self-luminous body along every straight line. 20. Extensive self-luminous bodies are continuous insofar as the small parts retain the shape of the fire (e.g. in the sun, in the moon, and in the other celestial bodies), no matter how small they shine. 21. We define the light of self-luminous bodies as primary light. 22. If daylight comes from the sun, why are shadows in courtyards lit up? 23. Even before and after sunrise, the atmosphere and the earth are filled with light. 24. Illuminated surfaces illuminate opposite surfaces. 25. We can test this experimentally using a door in front of a sunlit wall. 26. We can increase the experiment with a chamber in a chamber with white walls. This is also feasible in moonlight and daylight. 27. The experiments show that from the light that shines on a body, light radiates in every opposite direction. So the sun illuminates the atmosphere, the atmosphere in turn illuminates the earth. 28. This explains the light shadows. 29. These random lights can be investigated through certainty experiments; z. B. in a chamber in a chamber with holes from east to west. 30. We stretch threads through the holes and mark the points of intersection with the walls. 31. At night without bright stars, the wall will be dark in the marked places. 32. When the atmosphere is lit, there are spots of light at the marked points that can be individually shaded. 33. We can catch the light with an opaque body and also drill additional holes in the walls. 34. We conclude: light radiates in a straight line from the atmosphere. 35. There is no light on crooked paths between the holes and walls. 36. An obstruction does not break the continuity of air. 37. Light radiates in a straight line from any part of the enlightened air in all opposite directions. 38. Daylight comes straight from the lighted atmosphere. 39. One could object that no light comes through the atmosphere in the evening, although half the atmosphere is always bright. 40. To this I answer: Light becomes weaker with distance, so the more it penetrates into the shadow cone of the earth. 41. At sunrise, the illuminated atmosphere is directly adjacent to the shadow cone, is therefore close to the viewer and therefore appears bright. 42. The brightness depends on the distance; This creates a column of light at dusk, darkness at night - this can be justified geometrically. 43. The light is not inherent in the air, but is reflected back as if from a wall. 44. The amount of light depends on the volume. 45. Morning and evening light come from the large volume of air that is seen through. 46. Along the straight line to the eye, the faint lights of the various air sections multiply, so the light becomes visible. 47. This is how we would have clarified this problem: Morning and evening light come from the sun-lit air. 48. We can test random light experimentally using walls with doors and a specially marked block of wood. 49. We mark angles and distances on the cube. 50. We drill a horizontal and an oblique through hole. 51. We set the cube in a wall that faces a white, lighted wall. 52. We push a stick with a point through the horizontal hole in the cube and mark the point of impact on the white wall. 53. We look through the hole at the marked point and circle our head until the point becomes invisible. 54. We mark the targeted circle on the white wall. 55. The circle may need to be corrected. 56. The circle will also be visible through the oblique hole. 57. This is due to the previously established proportions. 58. Therefore the axes of the holes intersect in a circle on the wall. 59. The center of the circle lies on the axis of the horizontal hole 60. As well as on the axis of the oblique hole. 61. The lengths of the holes are related to each other like the distances from the holes to the white wall. 62. The circles are proportioned accordingly. 63. The circles behave accordingly with regard to the horizontal lines. 64. The inclined stretches behave accordingly to the horizontal stretches. 65. The circles behave accordingly to the inclined stretches. 66. Therefore, only the marked circle can be seen through the oblique hole. 67. If more can be seen, the cube must be corrected. 68. Instead of the circle on the wall, we now drill a conical hole in the white wall and cover the hole with white cloth. 69. With the oblique hole covered, we let a white object illuminate through the horizontal hole in the darkroom, with light coming from the white wall, which in turn comes from the atmosphere. 70. When the white cloth is removed, the light spot in the darkroom disappears. If there is residual light from inside the tube, 71. the tube should be painted black. 72. Light appears as soon as the white cloth covers the hole in the white wall. 73. Light only comes in from the white cloth, 74. Light on crooked paths does not. 75. A white object between the hole in the white wall and the hole in the cube will illuminate the chamber; another object between the cube hole and the object inside will take away the light. 76. As [73] & [74]. 77. Random light only works in a straight line 78. Because crooked lines are not important. 79. The light becomes weaker with increasing distance. 80. The same observations are possible with the oblique hole. 81. We conclude: light comes only from the white cloth and only in a straight line. 82. The light becomes weaker as the distance between the object and the oblique hole increases. 83. Now we open both holes at the same time. 84. Now we can use any number of holes. We conclude: A body illuminated by daylight shines in a straight line in all directions. 85. It works the same in sunshine, only better. 86. It works in the same way with moonlight and fire light. 87. We conclude: random light in opaque bodies radiates in a straight line in all directions and becomes weaker with increasing distance. 88. We define light from randomly illuminated bodies as secondary light, but it emanates from the body in the same way as primary light. 89. We can test this in experiments: A light spot from a hole in the darkroom shines like primary light and can be shielded by a cup. 90. With a mirror, the darkroom becomes brighter due to the bright spot of light. 91. Without a mirror, the light in the darkroom is not based on reflection. 92. The mirror can illuminate an object. 93. We exchange a white object for a black one. 94. We conclude: The light seen everywhere in the darkroom is secondary light, it does not arise from reflection. 95. Light from the moon behaves in the same way. 96. The same is true of light from objects illuminated by fire. 97. Mirrors, on the other hand, reflect; in addition, like any other body, they emit light in all directions. 98. Every part of an object shines in all directions, even if this is sometimes imperceptible due to the small amount of light. 99. Reflected light goes in a straight line. 100. We can test this in experiments by collecting the reflected light with an opaque object. 101. With a needle we can collect part of the reflected light; with a ruler we use the shadow to check the linear propagation of light 102. We conclude: light is always reflected in a straight line, never in a curvilinear manner. 103. The reflection takes place only in a certain direction. 104. Even after the transition into a transparent body of another transparency, the expansion is straight. 105. We can test this experimentally: We hold a glass ball in the sunlight in front of a wall, its shadow receives light that can be caught by an opaque body. We check the straightness of the light propagation with a needle as a shadow generator. 106. Light only passes through the transparent body in certain straight lines. 107. Light in the transparent body does not have the same direction as the light in front of or behind it, except when entering perpendicularly. 108. The exit point emits secondary light. 109. We can test this experimentally: A hole in the darkroom illuminates a glass ball in such a way that it illuminates objects around it. 110. Light therefore goes straight from all luminous bodies in all directions. 111. Secondary lights are weaker than primary lights; both become weaker with increasing distance. 112. Reflection and refraction happen in a straight line and only in certain directions. 113. Color goes hand in hand with light. 114. Secondary lights are strongly colored when the radiating body is strongly colored and the opposite body is weakly colored. 115. Green plants in the sunlight turn a nearby house wall in the shade green. 116. The leaf green appears in the shade on the wall, in the floor and on a white robe. 117. An experimental test is possible at any time. 118. We can carry out the following experiment: A purple body illuminated by the hole in the darkroom colors all interior walls purple. 119. White cloth near the purple body is colored all the more the closer it is; White bodies placed all around are colored. 120. This works with all light colors. White illuminates everything, black darkens everything. 121. Color always goes hand in hand with light. It also spreads in a straight line and decreases with increasing distance. 122. The color received from other objects does not reach the eye through reflection, but as if from colored bodies. 123. We hold on to [122] again. 124. If we hold a colored liquid in a glass in front of a hole in a darkroom, a white cloth that is held out appears in a clear color, which becomes weaker as the distance from the glass increases. 125. This also works with colored water, so the color is bound to the light. 126. This also works with a liquid-filled glass that is lit by fire. 127. We conclude: Together with light, color also emerges from transparent bodies. 128. We further conclude: color in general is always associated with light; if it is not visible, the sense of sight is too weak for that. 129. Transparent bodies, like light, can receive their color from themselves or from other bodies; like light, it shines straight in all directions. 130. Color cannot emanate from bodies unless they are emitted with light. 131. It is beyond dispute or uncertain that color and light radiate from bodies together. 132. Some see color as something that arises between the eye and light, but the iridescent colors of peacock feathers are based on reflection. 133. The color of opaque bodies, on the other hand, is visible all around (even if to different degrees) and is therefore not based on reflection. 134. Color comes from colored bodies, e.g. B. from a face filled with shame (while the external light and the observer's point of view remain the same). 135. Fear turns the face yellow. 136. We conclude that color is a form of colored body; it is not uncertain that it does not arise from external factors. 137. Even as color varies with lighting conditions, its own reality cannot be doubted. 138. Since light radiates naturally in all directions, and since color is bound to light, the spread of color around the body is independent of the eye. 139. Color is not based on reflection and is not produced by the sense of sight. 140. If so, then the color of the object irradiated by the colored body is a shape on the irradiated object. 141. As it is, the illuminated body radiates color and light in all directions, regardless of the eye. 142. Color spreads in a straight line with light in all directions. 143. This happens as long as the body is illuminated and the adjacent bodies are continuously transparent. 144. But why does the color appear only on shaded and primarily white bodies, and only when the body opposite is rich in color? This is due to the sense of sight.
Chapter 4: On the effect of light on the sense of sight
1. Looking into bright light - for example direct or reflected sunlight - hurts. 2. After looking at a brightly lit white body for a long time, a dark veil appears to fall between the observer and the observer; whether with sun or fire lighting. 3. After looking at a white object for a long time in daylight, something similar appears again as soon as one looks at a dark place, as well as with closed eyes. 4. The same happens after looking for a long time at a fire-lit object or a hole in the darkroom. 5. Apparently light has a certain effect on the sense of sight. 6. If you look at a brightly lit meadow or a purple body for a long time, a dark place appears green or purple. 7. We conclude: Illuminated colors have an effect on the sense of sight. 8. We do not see the stars visible at night during the day because the atmosphere is then filled with light. 9. Details of an object illuminated by fire are no longer visible when the viewer also has the fire in view. 10. Apparently, bright light shining on the eyes hinders the vision of dimly lit objects. 11. Details on a reflective object disappear when it reflects the bright sky or a bright wall in the eye. 12. The same applies to fine writing on smooth paper. 13. A lighted body in the sunshine is invisible, but the fire is visible. 14. In the same way, a white object that is irradiated by an illuminated colored body appears colored in the shade, but not in the sunshine. 15. Likewise, an object that is illuminated by a glass filled with colored liquid no longer appears colored when it is illuminated with another fire. 16. Some marine animals and fireflies appear to glow like fire in the dark, but not in daylight or fire. 17. All of this shows that the strong lights of visible objects disappear certain properties that are visible in dim lighting. 18. In dark places, details that are visible in light disappear, e.g. B. engravings or writing. 19. So strong light can bring out certain details that disappear in strong light. 20. Dark colors appear clear and distinct in light, but appear black in weak light. 21. Strong lighting makes white bodies brighter and dull colored bodies more colorful. 22. Transparent, strongly colored liquid appears black in weak light and colored in bright light. 23. The same goes for transparent stones. 24. The shadow of a transparent, colored body appears colored in strong light and colorless in weak light. 25. Peacock feathers and the fabric abu qalamun seem to change their colors depending on the lighting. 26. We conclude: The sense of sight perceives colors differently depending on the lighting. 27. Furthermore, the color depends on the light in the object, on the eye, and on the air. 28. I will explain in connection with the visual process why strong light hinders the view of certain objects.
Chapter 5: About the Structure of the Eye
1. The eye consists of various layers, membranes and bodies; it arises from the forebrain. 2. Two hollow, bilayered nerves cross in front of the brain and lead into the eye sockets. 3. The nerves go through openings in the eye sockets and lead like a funnel to the eye. 4. The eyeballs consist of several layers. 5. The first layer consists of white fat and is called the conjunctiva. 6. The second layer is blackish, lined like velvet and is called uvea because of its grape-like appearance. It is covered by the conjunctiva up to the front. 7. There is a hole in the uvea opposite the nerve. 8. The hole and the exposed uvea are covered by the horn-like cornea. 9. Opposite the hole is the lenticular, moist, ice-like, transparent crystal. 10. This body fluid is in two parts. The rear part is as transparent as crumbled glass, hence it is called glass body. Both parts are enclosed by the cobweb-like aranea. 11. The cornea emerges from the outer layer of the hollow nerve, the uvea from the inner. 12. A protein-like liquid, the albuginous liquid, fills the inside of the eye. 13. There are straight lines between all the transparent bodies. 14. It is said that the sight fills the nerves and gives the crystalline sight. 15. The nerve extends from the opening in the eye socket to the crystalline. In doing so, it expands. 16. The conjunctiva encloses the diverging nerve. The eye always moves as a whole. 17. The nerve is only bent at the opening to the eye socket. 18. Since the cornea merges into the surface of the eye, its radius is larger than that of the uvea. 19. According to the spherical geometry, the center of the inside of the cornea is further inside than that of the uvea. 20. The center of the outer surface is also further inwards. 21. A straight line goes through the two centers, and through the centers of the opening and the cornea. 22. The centers of albuginous fluid and cornea coincide. 23. The straight line through the uvea, cornea and hole in front goes through the center of the nerve cavity. 24. The circle of intersection between the front and back of the crystalline is the connecting circle, or parallel to it. 25. The straight line through the centers of uvea and crystalline goes vertically through the connecting circle 26. and vertically through the rest of the crystalline. 27. So the line goes through the nerve cavity. 28. This line goes vertically through all parts of the eye. 29. Most likely the center of the ball of the posterior surface of the crystalline and the center of the ball of the cornea coincide. 30. All layers opposite the uveal hole have their center in the middle of the eyeball. 31. The position of this center does not change when the eye moves. 32. The nerve bend takes place behind this center. 33. The nerve is symmetrical in relation to the connecting circle. 34. The surface of the nerve cavity does not change position with respect to the eyeball. 35. The line through the centers of the ocular layers goes straight through the center of the nerve cavity. 36. So these are the positions and proportions. 37. The geometry is the same for both eyes. 38. The conjunctiva is attached by two muscles each; Eyelids and eyelashes cover the eyes. 39. Everything shown is in the anatomy books.